Patent Publication Number: US-2021177629-A1

Title: Adjustable socket system

Description:
TECHNICAL FIELD 
     The disclosure relates to an adjustable socket system for a residual limb. 
     BACKGROUND 
     A typical prosthetic leg and foot includes a socket, pylon, and foot. A socket is commonly referred to as the portion of a prosthesis that fits around and envelops a residual limb or stump, and to which prosthetic components, such as a foot, are attached. Fitting and alignment of the socket are difficult tasks to perform, and require extensive knowledge, training and skill for the prosthetist. 
     The socket must fit closely to the stump to provide a firm connection and support, but must also be sufficiently loose to allow for circulation. In combination with proper fitting, the socket must transfer loads from the residual limb to the ground in a comfortable manner. 
     Conventional sockets are rigid and generally have a general uniform shape which receives a large portion of the residual limb. These sockets are permanently formed to a customized shape that is static, meaning the socket does not account for shape and volume fluctuations of the residual limb. When there are shape and volume fluctuations, the fitting of the socket is impeded, with these sockets causing discomfort, pain and soft tissue breakdown of the stump. Conventional sockets also tend to be bulky and cumbersome to wear, and may be difficult to don making the residual limb uncomfortable when worn. 
     Some attempts have been made to develop adjustable sockets with individual components that can be varied in size and/or shape to account for volume and shape fluctuations of the residual limb. These adjustable sockets however tend to have labor intensive and complicated tightening systems for donning and doffing the socket, making their use difficult for patients with limited dexterity, cognition, and/or strength. This can result in unsafe and improper use of the socket, causing discomfort and even injury. 
     In view of the foregoing, there is a need for an adjustable socket system that overcomes the problems of existing sockets. 
     SUMMARY 
     Embodiments of the present disclosure comprise an adjustable socket system that provide an intuitive and simple manner for users with limited dexterity or cognition to don and doff the system. From its straightforward and versatile design, the adjustable socket system can improve ease of use, and decrease the likelihood of over-tightening and/or under-tightening of the system over known adjustable socket systems. 
     An adjustable socket system of the present disclosure can include a base, a plurality of longitudinal supports connected to the base, and a plurality of shell components operatively connected to the longitudinal supports. The system is movable between an open configuration in which at least some of the shell components are moved radially outward relative to a longitudinal axis to loosen the fit of the system, and a closed configuration in which at least some of the shell components are moved radially inward relative to the open configuration to tighten the fit of the system or secure the fit of the system on the residual limb. 
     A tightening system is arranged to selectively move the adjustable socket system between the open and closed configurations. The tightening system includes a tensioning unit including at least one movable connection point and a handle defining a moment arm rotatable about a rotation axis, and at least one tensioning element operatively coupled to the handle via the at least one movable connection point and to at least one of the shell components via at least one control point. Rotation of the handle about the rotation axis from an off position to an on position displaces the at least one movable connection point and the at least one tensioning element relative to the at least one control point to tension the at least one tensioning element and move the adjustable socket system to the closed configuration. 
     Because the handle defines a moment, it provides a user a mechanical advantage, requiring less user strength to move the tensioning unit between the on position and the off position. In addition, the tensioning unit can have a binary configuration such that a user can only position and/or lock the handle in the on position or the off position, providing an intuitive and simple manner for users with limited dexterity or cognition to don and doff the adjustable socket system. This is beneficial over known tightening systems such as dial tensioners or strap systems which require complex levels of manual dexterity, making their use difficult and intimidating for many users. The binary configuration of the tensioning unit also allows the tensioning unit to control the basic fit of the adjustable socket system on the residual limb rather than requiring the user to precisely fit the system with straps or dial tensioners, as in the prior art, substantially decreasing the likelihood that a user will over-tighten or under-tighten the adjustable socket system, improving ease of use and safety (especially for elderly users). 
     According to a variation, the at least one tensioning element provides a closing effect on the handle or urges the handle toward the on position. This beneficially reduces the physical effort required to put the handle into the on position. Additionally, and in contrast to prior art tightening systems such as dial tensioners and electrical switches, the closing effect on the handle safely stows the tensioning unit in the on position, reducing the risk of accidental release, thereby improving user safety. 
     According to a variation, the tightening system includes one or more elastic elements operatively coupled to the handle and the at least one tensioning element to permit automatic volume adaption of the adjustable socket system. “Automatic” means “without human intervention.” For instance, when the handle is moved from the off position to the on position, the elastic elements can be configured to deflect so that the volume of the adjustable socket system can adapt or adjust to more closely match that of a residual limb. This advantageously improves comfort and ease of use, especially for users with limited dexterity or cognition. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present disclosure will become better understood regarding the following description, appended claims, and accompanying drawings. 
         FIG. 1  is a side view of a socket system according to an embodiment. 
         FIG. 2A  is a front view of the socket system in  FIG. 1  in an open configuration according to an embodiment. 
         FIG. 2B  is a front view of the socket system in  FIG. 1  in a closed configuration according to an embodiment. 
         FIG. 3  is a partial exploded view of the tensioning unit in the socket system of  FIG. 1 . 
         FIG. 4A  is a partial schematic view of the tensioning unit in the socket system of  FIG. 1  in the open configuration according to an embodiment. 
         FIG. 4B  is a partial schematic view of the tensioning unit in the socket system of  FIG. 1  in the closed configuration according to an embodiment. 
         FIG. 5  is a side view of the displacement wheel in the socket system of  FIG. 1  according to an embodiment. 
         FIG. 6  is a partial schematic view of the tightening system in the socket system of  FIG. 1  according to an embodiment. 
         FIG. 7  is a side view of a tensioning unit according to another embodiment. 
         FIG. 8  is a partial schematic view of a tightening system including the tensioning unit in  FIG. 7 . 
         FIG. 9  is an exploded view of a secondary tensioner according to an embodiment. 
         FIG. 10A  is a side view of an adjustable socket system in an open configuration according to another embodiment. 
         FIG. 10B  is side view of the adjustable socket system in  FIG. 10A  in a closed configuration. 
         FIG. 11A  is a schematic view of the tensioning unit in the socket system of  FIG. 10A  in an off position. 
         FIG. 11B  is a schematic view of the tensioning unit in the socket system of  FIG. 10A  in an on position. 
         FIG. 12  is a partially exploded view of a secondary tensioner according to another embodiment. 
         FIG. 13  is a schematic view of a volume adjustment system according to an embodiment. 
         FIG. 14  is a perspective view of a grip portion according to another embodiment 
         FIG. 15A  is a schematic view of a tensioning unit in a first position according to another embodiment. 
         FIG. 15B  is a schematic view of the tensioning unit in  FIG. 15A  in a second position. 
         FIG. 16  is a partial side view of a tensioning unit according to another embodiment. 
         FIG. 17  is a side view of an adjustable socket system according to another embodiment. 
         FIG. 18A  is a partial schematic view of a tightening system with a tensioning unit in an off position according to an embodiment. 
         FIG. 18B  is a partial schematic view of the tensioning unit of  FIG. 18A  in an on position according to an embodiment. 
         FIG. 19  is a side view of an adjustable socket system according to another embodiment. 
         FIG. 20  is a partially exploded view of the tensioning unit and lateral support of  FIG. 19 . 
         FIG. 21  is a side view of the displacement wheel of  FIG. 19 . 
         FIG. 22  is a partially exploded view of the tensioning unit of  FIG. 22 . 
         FIG. 23  is an exploded view of a secondary tensioner of  FIG. 19  according to another embodiment. 
         FIG. 24  is a bottom view of the secondary tensioner body of  FIG. 23 . 
     
    
    
     DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS 
     A better understanding of different embodiments of the disclosure may be had from the following description read with the accompanying drawings in which like reference characters refer to like elements. 
     While the disclosure is susceptible to various modifications and alternative constructions, certain illustrative embodiments are in the drawings and are described below. It should be understood, however, there is no intention to limit the disclosure to the specific embodiments disclosed, but on the contrary, the intention covers all modifications, alternative constructions, combinations, and equivalents falling within the spirit and scope of the disclosure. 
     It will be understood that unless a term is expressly defined in this application to possess a described meaning, there is no intent to limit the meaning of such term, either expressly or indirectly, beyond its plain or ordinary meaning. 
     Any element in a claim that does not explicitly state “means for” performing a specified function, or “step for” performing a specific function is not to be interpreted as a “means” or “step” clause as specified in 35 U.S.C. § 112(f). 
       FIGS. 1-6  illustrate an adjustable socket system  100  according to an embodiment. As seen in  FIG. 1 , the socket system  100  can include a base  102 , a plurality of longitudinal supports  104  connected to the base  102 , and a plurality of shell components  106  connected to the supports  104 . The shell components  106  collectively form a socket wall  108  defining a receiving volume  110  adapted to receive a residual limb. The shell components  106  can include a medial shell component  106 A that wraps around and engages at least a medial aspect of the residual limb, and a lateral shell component  106 B that wraps around and engages at least a lateral aspect of the residual limb. The shell components  106  can be formed of plastic materials, such as thermoplastic or thermosetting polymers, fiber reinforced plastic, polypropylene, polyethylene, molded chopped fibers, or any other suitable materials. 
     The base  102  is arranged to provide support for a distal end of the residual limb and can include at least one coupling device  112  for fixing or securing the residual limb or a liner to the base  102 . The base  102  and longitudinal supports  104  can be formed of any suitable material. For example, the base  102  and/or the longitudinal supports  104  can be formed of metal or molded parts including plastic with carbon fiber mixed therein. 
     The socket system  100  is radially adjustable between an open configuration and a closed configuration. A tightening system  114  is arranged to move the socket system  100  between the open and closed configurations. In the open configuration (shown in  FIG. 2A ), at least some of the longitudinal supports  104  and/or shell components  106  are free to move or are forced radially outward relative to a longitudinal axis  116  of the socket system  100 , increasing the receiving volume  110  or increasing a circumference of the socket system  100 . This effectively loosens the fit of the socket system  100  on a residual limb inserted in the receiving volume  110  or decreases the loading on the residual limb from the socket wall  108 . 
     In the closed configuration (shown in  FIG. 2B ), at least some of the longitudinal supports  104  and/or the shell components  106  are moved or forced radially inward relative to the open configuration, decreasing the receiving volume  110  or decreasing the circumference of the socket system  100 . For instance, the longitudinal supports  104  can include a medial support  104 A having an elongate configuration and a lateral support  104 B having an elongate configuration. At least one of the medial or lateral supports  104 A,  104 B can be pivotally connected to the base  102  such that in the closed configuration at least one of the medial or lateral supports  104 A,  104 B is rotated or folded toward the other to decrease the receiving volume  110 . This tightens or secures the fit of the socket system  100  on a residual limb inserted in the receiving volume  110  and/or increases the loading on the residual limb from the socket wall  108 . It will be appreciated that movement of any suitable portion of a support or shell component can move the socket system  100  between the open and closed configurations. 
     The tightening system  114  includes a tensioning unit  118 , one or more tensioning elements  120  operatively coupled to the tensioning unit  118 , and one or more secondary tensioners  122  operatively coupled to the one or more tensioning elements  120 . It will be appreciated that the tensioning elements  120  may be formed of line, cord, wire, string, combinations thereof, or any other suitable element. 
     The tensioning elements  120  are routed through a plurality of guides  124  on the shell components  106  and/or longitudinal supports  104 , facilitating tightening of the socket system  100 . For instance, the tensioning elements  120  can extend from the tensioning unit  118  through upper and lower guides  126 A,  126 B on the lateral support  104 B, which, in turn direct the tensioning elements  120  through upper and lower guides  128 A,  128 B located along or near leading edges  130  of the medial shell component  106 A. 
     In an embodiment, the tensioning elements  120  can include a first tensioning element  120 A (shown in  FIG. 2A ) forming a first loop over a distal posterior region of the lateral aspect of the socket system  100 , a second tensioning element  120 B forming a second loop over a distal anterior region of the lateral aspect, a third tensioning element  120 C forming a third loop over a proximal anterior region of the lateral aspect, and a fourth tensioning element  120 D (all shown in  FIG. 2A ) forming a fourth loop over a proximal posterior region of the lateral aspect of the socket system  100 . Increasing tension in the tensioning elements  120 A,  120 B,  120 C,  120 D reduces the circumference of the loops, which, in turn pulls the leading edges  130  of the medial shell component  106 A together, tightening the fit of the socket system  100  on the residual limb. While the tensioning elements  120  are described forming loops, it will be appreciated that the tensioning elements  120  can be routed on the socket system  100  in any suitable configuration and on any suitable region of the socket system  100 . For instance, the tensioning elements  120  can be routed in a zig-zagging pattern between the lateral guides  126 A,  126 B and the medial guides  128 A,  128 B. 
     This grouping of guides  124  allows the tightening system  114  to tighten and/or loosen the socket system  100  by actively tensioning a limited region rather than wrapping and/or tightening cables or wires about the entire or substantial entirety of the socket wall  108 , improving user comfort. This helps reduce the overall profile of the socket system  100 . It also helps limit pressure points from forming on different areas of the residual limb. Pressure points on the residual limb can be problematic in that the pressure points cause irritation, pain, and discomfort to the user. Further, when the tensioning elements  120  are tensioned, they tend to tension or pull the medial shell component  106 A tight around the residual limb rather than compress directly on the residual limb, further increasing user comfort. 
     The upper and lower guides  126 A,  126 B can be integrated into the lateral support  104 B, lowering the overall profile of the socket system  100  and improving structural reliability. The upper and lower guides  126 A,  126 B can alternatively be attached to the lateral support  104 B. The upper and lower guides  126 A,  126 B can define elongated linear and/or curved pathways that direct the tensioning elements  120  between the tensioning unit  118  and upper and lower guides  128 A,  128 B on the medial shell component  106 A, reducing friction in the tightening system  114 . 
     Referring now to  FIGS. 2A and 2B , the socket system  100  can be easily opened or closed with a simple manipulation of the tensioning unit  118  between off and on positions, respectively. In an embodiment, the tensioning unit  118  comprises a handle  132  defining a moment arm rotatable about a rotation axis  134  and operatively coupled to the tensioning elements  120 . 
     In the off position (shown in  FIG. 2A ), slack or low tensions levels in the tensioning elements  120  can allow the socket system  100  to move toward the open configuration. In the on position (shown in  FIG. 2B ), the handle  132  effectively pulls and/or shortens the length of the tensioning elements  120  forming the loops, which, in turn, tensions the tensioning elements  120  and the shell components  106  to move the socket system  100  to the closed configuration. More particularly, the tensioning elements  120  are connected to the tensioning unit  118  via at least one movable connection point  138  (shown in  FIG. 4A ) that shifts toward and away from at least one control point  136  (also shown in  FIG. 4A ) that directs the tensioning elements  120  between the tensioning unit  118  and the shell component  106  and/or longitudinal supports  104 . This shifting of the movable connection point  138  relative to the control point  136  displaces the tensioning elements  120  extending from the tensioning unit  118  up or down along the longitudinal axis  116 . In an embodiment, the movable connection point  138  can be operatively associated with the handle  132  and the control point  136  can be defined by at least one of the guides  126 A,  126 B. In other embodiments, the control point  136  can be defined by at least one of the guides  128 A,  128 B or any other suitable point along the tensioning elements  120  between the shell components  106  and the tensioning unit  118 . 
     Movement of the handle  132  from the off position to the on position shifts the movable connection point  138  away from the control point  136 , which, in turn, displaces the tensioning elements  120  up or down along the longitudinal axis  116 . This tensions the tensioning elements  120  and the shell components  106  to move the socket system  100  to the closed configuration. Because the handle  132  defines a moment arm it provides the user a mechanical advantage, as it requires less user strength to move the tensioning unit  118  between the on position and off position. 
     In addition, the tensioning unit  118  can have a binary configuration such that a user can only position and/or lock the handle  132  in the on position or the off position. In other words, the tensioning unit  118  is either on or off, providing an intuitive and simple manner for users with limited dexterity or cognition to don and doff the socket system  100 . This is beneficial over known tightening systems such as dial tensioners or strap systems which require complex levels of manual dexterity, making their use difficult and intimidating for many users. The binary configuration of the tensioning unit  118  also controls the basic fit of the socket system  100  on the residual limb rather than requiring the user to precisely fit the system with straps or dial tensioners, as in the prior art. This substantially decreases the likelihood that a user will over-tighten or under-tighten the socket system  100 , and improves ease of use and safety, especially for elderly users. According to a variation, the binary configuration of tensioning unit  118  permits the user to only lock the handle  132  in the on position. 
     In an embodiment, the tensioning elements  120  provide a closing effect on the handle  132  or urge the handle  132  toward the on position. For example, the tensioning elements  120  can be located and configured to pull the handle  132  toward the on position or in the posterior direction P when the handle  132  reaches a critical angle about the rotation axis  134 , providing the closing effect on the handle  132 . 
     It will be appreciated that the tightening system  114  may provide a closing effect on the handle  132  via other means. For instance, the tensioning unit  118  and/or base  102  can include magnets, ferromagnetic material, and/or ferrous material to form a magnetic attraction between the handle  132  and the base  102 , achieving a closing effect on the handle  132  toward the on position. In other embodiments, the tensioning unit  118  can include a latch release mechanism that selectively stows the handle  132  in the on position, achieving a closing effect. 
     In the illustrated embodiment, the handle  132  includes a connecting portion  132 A and a grip portion  132 B connected to the connecting portion  132 A and curving toward the medial support  104 A (shown in  FIG. 1 ). The grip portion  132 B can be wider than the connecting portion  132 A and its orientation and arrangement provides a large and ergonomic gripping area for the user, making operation of the handle  132  easier for users with limited dexterity. Moreover, the elongate configuration of the connecting portion  132 A provides a user with greater mechanical advantage, requiring less user strength to move the tensioning unit  118  between the on position and off position. The handle  132  can be formed of any suitable material such as metal, plastic, carbon fiber, combinations thereof, or any other material which would provide sufficient strength to resist unwanted deformation during use or accidental contact with external objects. 
     As best seen in  FIG. 2B , when the handle  132  is in the on position, the connecting portion  132 A extends downwardly and the grip portion  132 B wraps around an anterior side of the base  102 . This beneficially locates the grip portion  132 B substantially adjacent the base  102  and below the shell components  106 , lowering the general profile of the handle  132  on the socket system  100  and reducing the risk of it being dislodged by accidental contact with external objects. The positioning of the handle  132  on the anterior side of the base  102  also allows the base  102  and/or the lateral support  104 B to partially shield the handle  132  in the on position, further reducing the risk of the handle  132  being dislodged by accidental contact. 
     The tensioning unit  118  thus provides a binary system that beneficially facilitates donning and doffing of the socket system  100  as good hand dexterity and/or strength is not required to operate the tensioning unit  118 . The tensioning unit  118  also decreases and/or eliminates the likelihood that a user will over-tighten and/or under-tighten the socket system  100  on the residual limb, enhancing safety and comfort. It will be appreciated that while the tightening system  114  is generally described on the lateral aspect of the socket system  100 , this and other tightening systems of the present disclosure can be adapted for use on the medial, anterior, or posterior aspect of the socket system  100  to achieve the same or similar benefits. 
     The secondary tensioners  122  enable tension control of the tensioning elements  120  independent of the tensioning unit  118 . This allows for adjustment or control of tension in the tensioning elements  120  even when the tensioning elements  120  are under a load. For instance, when the tensioning unit  118  is in the on position, a clinician or certified prosthetist orthoptist (“CPO”) can manipulate at least one of the secondary tensioners  122  to fine tune the fit or loading of the socket system  100  on the residual limb. 
     If the fit of the socket system  100  is too loose, at least one of the secondary tensioners  122  can be manipulated to decrease the length of at least one of the tensioning elements  120  and thereby increase tension in the tensioning element  120 . If the fit of the socket system  100  is too tight, at least one of the secondary tensioners  122  can be manipulated to increase the length of at least one of the tensioning elements  120  and thereby decrease tension in the tensioning elements  120 . 
     The secondary tensioners  122  can be connected to different tensioning elements  120 . For example, the secondary tensioners can include a first secondary tensioner  122 A connected to the first tensioning element  120 A, a second secondary tensioner  122 B connected to the second tensioning element  120 B, a third secondary tensioner  122 C connected to the third tensioning element  120 C, and a fourth secondary tensioner  122 D connected to the fourth tensioning element  120 D. 
     The first and second secondary tensioners  122 A,  122 B can be located on opposite sides of the lateral support  104 B and the third and fourth secondary tensioners  122 C,  122 D can be located above the first and second secondary tensioners  122 A,  122 B on opposite sides of the lateral support  104 B. This allows the loading or fit of the socket system  100  to be proportionally or differentially adjusted using different ones of the secondary tensioners  122 A,  122 B,  122 C,  122 D. 
     The secondary tensioners  122  can comprise spool units, worm gear units, torque units, friction plates, turn dial units, or any other suitable mechanisms. Four secondary tensioners  122 A,  122 B,  122 C,  122 D are shown but the tightening system  114  can include any suitable number of secondary tensioners  122 . 
       FIG. 3  shows a partial exploded view of the tensioning unit  118  according to an embodiment. The tensioning unit  118  includes the handle  132 , a displacement member comprising a displacement wheel  142  rotatably mounted on the lateral support  104 B, and a plate member  144  secured over the displacement wheel  142  via a plurality of support posts  146 . The handle  132  is attached to the displacement wheel  142  via an opening  148  formed in the plate member  144 . Movement of the handle  132  between the on position and the off position rotates the displacement wheel  142  about the rotation axis  134 . 
     Referring to  FIGS. 4A and 4B , the displacement wheel  142  includes the movable connection point  138  comprising a pulley assembly  150  engaging one or more of the tensioning elements  120 . The pulley assembly  150  includes a pin  152  and a pulley  154  mounted on the pin  152 . The pulley  154  may be fixedly attached to the pin  152  or the pulley  154  may rotate on the pin  152 . The pulley assembly  150  moves in a circular path on the displacement wheel  142  when the displacement wheel  142  rotates about the rotation axis  134 . A variable distance D is defined between the movable connection point  138  and the control point  136 . Optionally, the displacement wheel  142  includes a plurality of attachment holes for varying the position of the pulley assembly  150  on the displacement wheel  142 . 
     As seen, a first end of the tensioning element  120 A can be attached to a first anchor point  156 . The first anchor point  156  may comprise one of the support posts  146 . From the first anchor  156  point, the first tensioning element  120 A extends to the movable connection point  138  or pulley assembly  150  where the first tensioning element  120 A partially loops around the pulley assembly  150 , which directs it toward the control point  136 . To enhance displacement of the tensioning element  120 , the tensioning element  120  can be looped around the pulley assembly  150  one or more times. In the illustrated embodiment, the first and second tensioning elements  120 A,  120 B are engaging the pulley assembly  150 . 
       FIG. 4A  shows the tensioning unit  118  in the off position with the two tensioning elements  120 A,  120 B passing over the pulley assembly  150 , one to the first anchor point  156  and the other to a second anchor point  158 . When the tensioning unit  118  moves to the on position, the pulley assembly  150  or movable connection point  138  moves along a circular path on the displacement wheel  142 , moving the pulley assembly  150  or movable connection point  138  upward relative to the control point  136  as seen in  FIG. 4B . This increases the distance D between the movable connection point  138  and the control point  136  and displaces the tensioning elements  120 A,  120 B in an upward direction, which, in turn, tensions the tensioning elements  120 A,  120 B and the shell components  106  to move the socket system  100  to the closed configuration. 
     When the pulley assembly  150  reaches a critical angle Y, the tensioning elements  120 A,  120 B can pull the handle  132  toward the base  102  or in a posterior direction P. This provides a closing effect that safely stows the handle  132  and decreases the risk of accidental release. In an embodiment, the critical angle Y can be greater than about 180 degrees, about 181 degrees, about 182 degrees, about 185 degrees, or about 190 degrees relative to the location of the pulley assembly  150  when the tensioning unit  118  is in the off position. 
       FIG. 5  illustrates a displacement wheel  142  according to an embodiment. The displacement wheel  142  defines an attachment portion  160  for attachment of the handle  132  and includes a first movable connection point  138 A comprising a first pulley assembly  150 A extending between a first plate  162  and a second plate  164 , and a second movable connection point  138 B comprising a second pulley assembly  150 B extending between the second plate  164  and a third plate  166 . 
     The first and second pulley assemblies  150 A,  150 B can be radially offset relative to the longitudinal axis  116 . For instance, they can be at different levels on the displacement wheel  142  such that rotation of the displacement wheel  142  moves the first pulley assembly  150 A in an arcuate path with the second pulley assembly  150 B moving in an arcuate path above the first pulley assembly  150 A. Having first and second pulley assemblies  150 A,  150 B at different levels on the displacement wheel  142  permits at least some of the tensioning elements  120  to be separated from one another during use of the tensioning unit  118 . For instance, the first and second tensioning elements  120 A,  120 B can be connected to the first pulley assembly  150 A, and the third and fourth tensioning element  120 C,  120 D can be connected to the second pulley assembly  150 B. This reduces friction on the tensioning elements  120 , which, in turn, decreases the physical effort needed to move the handle  132  to the on position. The reduction in friction also decreases wear and tear on the tensioning elements  120  and components in contact with the tensioning elements  120 . 
     The first and second pulley assemblies  150 A,  150 B can be angularly offset relative to one another. For instance, the first and second pulley assemblies  150 A,  150 B can be offset about 180 degrees or by some other angular distance. This helps ensure that when the handle  132  is moved to the on position both the lower tensioning elements  120 A,  120 B and the upper tensioning elements  120 C,  120 D are tensioned. 
     The angular offset between the first and second pulley assemblies  150 A,  150 B can also form a constant force mechanism so that the input force required to move the handle  132  between the on and off positions is substantially constant over the range of motion of the handle  132 . For example, as the tensioning unit  118  moves between the on and off positions, the forces on the first and second pulley assemblies  150 A,  150 B from the tensioning elements  120 A,  120 B,  120 C,  120 D can generally oppose one another so that an input force required to move the handle  132  is substantially constant over the range of motion of the handle  132 . This can help facilitate operation of the tightening system  114  for users with limited strength and/or dexterity. 
       FIG. 6  is a schematic view of the tightening system  114  according to an embodiment. A first end of the first tensioning element  120 A is attached to the first anchor point  156  on or near a support base  168  for the tensioning unit  118 . The support base  168  can be attached to or integrated into the lateral longitudinal support  104 B and/or the lateral shell component  106 B. The first anchor point  156  may comprise any suitable structure such as one of the support posts  146  (shown in  FIG. 3 ). From the first anchor point  156 , the first tensioning element  120 A extends to the first movable connection point  138 A comprising the first pulley assembly  150 A. The first pulley assembly  150 A then directs the first tensioning element  120 A to a first control point  136 A. The first control point  136 A can comprise the lower guide  126 B. The lower guide  126 B then directs the first tensioning element  120 A to the lower guide  128 B on the posterior side P of the medial shell component  106 A. The lower guide  128 B then directs the first tensioning element  120 A to the first secondary tensioner  122 A. A second end of the first tensioning element  120 A is attached to the first secondary tensioner  122 A. 
     A first end of the second tensioning element  120 B is attached to the second anchor point  158  on or near the support base  168 . From the second anchor point  158 , the second tensioning element  120 B extends to the first movable connection point  138 A or first pulley assembly  150 A. The first pulley assembly  150 A then directs the second tensioning element  120 B toward the first control point  136 A or the lower guide  126 B. The lower guide  126 B then directs the second tensioning element  120 B to a lower guide  128 B on the anterior side A of the medial shell component  106 A. The lower guide  128 B then directs the second tensioning element  120 B to the second secondary tensioner  122 B. A second end of the second tensioning element  120 B is attached to the second secondary tensioner  122 B. 
     A first end of the third tensioning element  120 C is attached to a third anchor point  170  on or near the support base  168 . From the third anchor point  170 , the third tensioning element  120 C extends through the upper guide  128 A on the anterior side A of the medial shell component  106 A. The upper guide  128 A then directs the third tensioning element  120 C to a second control point  136 B comprising the upper guide  126 A on the lateral support  104 B. The third tensioning element  120 C then extends to a second movable connection point  138 B comprising the second pulley assembly  150 B. From the second movable connection point  138 B, the third tensioning element  120 C loops around the support post  146  on the anterior side A, back around the second pulley assembly  150 B, and then back to the second control point  136 B and through the upper guide  126 A. From the upper guide  126 A, the third tensioning element  120 C extends again through the upper guide  128 A, which, in turn, directs the third tensioning element  120 C to the third secondary tensioner  122 C. A second end of the third tensioning element  120 C is attached to the third secondary tensioner  122 C. 
     A first end of the fourth tensioning element  120 D is attached to a fourth anchor point  172  on or near the support base  168 . From the fourth anchor  172  point, the fourth tensioning element  120 D extends through the upper guide  128 A on the posterior side P of the medial shell component  106 A. The upper guide  128 A then directs the fourth tensioning element  120 D to the second control point  136 B or the upper guide  126 A on the lateral support  104 B. The fourth tensioning element  120 D then extends to the second movable connection point  138 B or the second pulley assembly  150 B. From the second movable connection point  138 B, the fourth tensioning element  120 D loops around the support post  146  on the anterior side A, extends again around the second pulley assembly  150 B, and then back to the second control point  136 B and through the upper guide  126 A. From the upper guide  126 A, the fourth tensioning element  120 D extends again through the upper guide  128 A, which, in turn, directs the fourth tensioning element  120 D to the fourth secondary tensioner  122 D. A second end of the fourth tensioning element  120 D is attached to the fourth secondary tensioner  122 D. 
     When the handle  132  is moved to the on position, the displacement wheel  142  rotates in a first direction about the rotation axis  134 , which, in turn, moves the first movable connection point  138 A (e.g., the first pulley assembly) upwardly away from the first control point  136 A (e.g, the lower guide  126 B). This displaces the first and second tensioning elements  120 A,  120 B in an upwardly direction, which in turn tensions the first and second tensioning elements  120 A,  120 B and tightens a distal region of the socket system  100 . 
     Rotation of the displacement wheel  142  in the first direction simultaneously moves the second movable connection point  138 B (e.g., the second pulley assembly) downwardly away from the second control point  136 B (e.g., the upper guide  126 A). This displaces the third and fourth tensioning elements  120 C,  120 D in a downwardly direction, which, in turn, tensions the third and fourth tensioning elements  120 C,  120 D and tightens a proximal region of the socket system  100 . As seen, the first and second pulley assemblies  150 A,  150 B can be angularly offset about 180 degrees to help ensure that when the handle  132  turns, all of the tensioning elements  120  tension. Further, the first and second pulley assemblies  150 A,  150 B can be located at different levels on the displacement wheel  142  to reduce friction on the tensioning elements  120 . 
     When the handle  132  is moved to the off position, the displacement wheel  142  rotates in a second direction opposite the first, allowing the tensioning elements  120 A,  120 B,  120 C,  120 D and the movable connection points  138 A,  138 B to return toward their original positions, reducing tension in the tensioning elements and permitting the socket system  100  to move to the open configuration. It will be appreciated that the number and routing of the tensioning elements  120  on the tightening system  114  is exemplary only as different numbers of tensioning elements and different paths are possible. 
     Optionally, the tightening system  114  can include one or more elastic elements to permit automatic volume adaptation of the socket system  100 . More particularly, when the handle  132  is moved from the off position to the on position, the elastic elements can be arranged to deflect so that a volume of the adjustable socket system can adapt or adjust to more closely match that of the residual limb. This beneficially improves comfort and ease of use of the socket system  100 , especially for users with limited dexterity or cognition. 
       FIGS. 7 and 8  illustrate a tightening system  214  according to another embodiment. The tightening system  214  is similar or generally the same as the tightening system  114  except that it includes a plurality of elastic elements that permit automatic volume adaption of the socket system  100 . For instance, the tightening system  214  includes a tensioning unit  218 , one or more tensioning elements  220  arranged to interact with the tensioning unit  218 , and one or more secondary tensioners  222  operatively coupled to the tensioning elements  220 . The tensioning elements  220  are routed through a plurality of guides  124  on the medial shell component  106 A. As seen, the tensioning elements  220  include four tensioning elements  220 A,  220 B,  220 C, and  220 D. Each tensioning element  220 A,  220 B,  220 C, and  220 D includes an end attached to a corresponding secondary tensioner  222 A,  222 B,  222 C,  222 D and interacts with one of the first and second pulley assemblies  250 A,  250 B carried on the displacement wheel  242 . 
     The tensioning unit  218  includes a handle  232  operatively coupled to the tensioning elements  220 . The handle  232  defines a moment arm attached to a displacement wheel  242  that is rotatable about a rotation axis  234 . The displacement wheel  242  carries a first movable connection point  238 A comprising the first pulley assembly  250 A and a second movable connection point  238 B comprising the second pulley assembly  250 B that engage or interact with the tensioning elements  220  and move along a circular path about the rotation axis  234 . The first and second tensioning elements  220 A,  220 B include one or more segments extending between the first pulley assembly  250 A and a first control point  236 A comprising the lower guide  228 B. The third and fourth tensioning elements  220 C,  220 D includes one or more segments extending between the second pulley assembly  250 B and a second control point  236 B comprising the upper guide  228 A. 
     In the off position, tension levels or slack in the tensioning elements  220  can permit the adjustable socket system  100  to move toward the open configuration. The engagement or interaction between the tensioning elements  220  and the pulley assemblies  250 A,  250 B is such that movement of the handle  232  from the off position to the on position displaces the pulley assemblies  250 A,  250 B up or down relative to the first and second control points  236 A,  236 B, which, in turn, displaces the tensioning elements  220  up or down along the longitudinal axis  216 . This displacement tensions the tensioning elements  220  and the shell components  106  to move the socket system  100  to the closed configuration. The tensioning unit  218  can have a binary configuration such that a user can only lock the handle  232  in the on position or the off position, providing an intuitive and simple manner for users with limited dexterity or cognition to don and doff the socket system  100 . The binary configuration of the tensioning unit  118  also decreases and/or eliminates the likelihood that a user will over-tighten and/or under-tighten the socket system  100  on the residual limb, enhancing safety and comfort. According to a variation, the binary configuration of tensioning unit  218  permits the user to only lock the handle  232  in the on position. 
     The elastic elements  274  are operatively coupled to the handle  232  and the tensioning elements  220  to permit automatic volume adjustment of the socket system  100 . For instance, each tensioning element  220 A,  220 B,  220 C,  220 D is operatively connected to the handle  232  and a corresponding elastic element  274 A,  274 B,  274 C,  274 D positioned in a housing unit  276  mountable on the lateral support  104 B. The housing unit  276  can protect the elastic elements  274  and reduce the likelihood of injury from the elastic elements. The housing unit  276  can define windows  277  corresponding to the elastic elements  274  which allow a user or clinician to observe loading of the elastic elements  274 . The elastic elements  274 A,  274 B,  274 C,  274 D are shown as compression springs but can be constant force springs, pre-tension springs, variable tension springs, combinations thereof, or any other suitable elastic element. 
     Movement of the handle  232  from the off position to the on position displaces the tensioning elements  220 A,  220 B,  220 C,  220 D up or down, which, in turn, loads the elastic elements  274 A,  274 B,  274 C,  274 D in the housing unit  276 . As the load is applied, the elastic elements deflect or get shorter. As the load is reduced or removed, the stored energy in the elastic elements moves them back toward their equilibrium length. The deflection of the elastic elements  274 A,  274 B,  274 C,  274 D allows the fit of the socket system  100  to adapt to the shape of the residual limb. 
     For instance, if a proximal region of the residual limb has a larger circumference, the residual limb can hold back the shell components  106  in the proximal region as the tensioning unit  218  moves the socket system  100  toward the closed configuration, which, in turn, causes the third and fourth tensioning elements  220 C,  220 D to load and/or shorten the elastic elements  274 C,  274 D. Within an elastic range of the elastic elements  274 C,  274 D, the amount of deflection or shortening of the elastic elements  274 C,  274 D increases with the magnitude of the load on the elastic elements  274 C,  274 D. This shortening of the elastic elements  274 C,  274 D effectively increases a length of the tensioned third and fourth tensioning elements  220 C,  220 D outside of the tensioning unit  218 , allowing an increased circumference of the proximal region of the shell components  106  when the socket system  100  enters the closed configuration. 
     As such, deflection of the elastic elements  274  automatically adjusts the volume of the socket system  100  to better match the dimensions of the residual limb. Moreover, it will be appreciated that because the elastic elements  274 A,  274 B,  274 C,  274 D are generally independent of one another, the fit of the socket system  100  on different regions of the residual limb can be different. In other embodiments, the tensioning elements  220  can be connected to a common elastic element. Four tensioning elements and elastic elements are shown, but any number is possible. 
     Optionally, the tightening system  214  can include a lockout system that fixes the length of the elastic elements  274 A,  274 B,  274 C,  274 D once the tensioning unit  218  is in the on position. This helps makes it so that the elastic elements  274 A,  274 B,  274 C,  274 D cannot deflect to increase or decrease the volume of the socket system  100  when the socket system  100  is in the closed configuration or bearing weight, thus enhancing stability. 
       FIG. 9  illustrates a secondary tensioner  322  according to an embodiment. The secondary tensioner  332  includes a housing  376 , a spool  378 , and a lid  380 . The spool  378  is situated within the housing  376  such that the spool  378  is rotatable relative to the housing  376 . The housing  376  can be attached to a support base  168  (shown in  FIG. 6 ) or integrated with other components of the socket system  100 . A tensioning element  220  can be attached to the spool  378  via an opening  382  formed in the housing  376 . 
     When the spool  378  rotates in a tightening direction, the tensioning element  220  is drawn into the housing  376  and is wound around the spool  378 . As the tensioning element  220  is wound around the spool  378 , tension in the tensioning element  220  increases, causing the socket system  100  to tighten. When the spool  378  rotates in a loosening direction, the tensioning element  220  unwinds from the spool  378  and at least part of the tensioning element  220  exits the housing  376 . As the tensioning element  220  unwinds from the spool  378 , tension in the tensioning element  220  decreases, loosening the socket system  100 . 
     A spring member  384  can be disposed between the housing  376  and the spool  378  that forces the upper surface of the spool  378  into engagement with a lower surface of the lid  380 . The spool  378  and lid  380  define corresponding engagement features arranged to only allow the spool  378  to rotate relative the housing  376  via an external input. For instance, the lid  380  includes an upper opening  386  and the spool  378  defines a socket  388 , each arranged to receive a tool member (e.g., a wrench or key) so that a CPO or user can rotate the spool  378  to adjust tension in the tensioning element  220 . The secondary tensioner  322  thus beneficially permits adjustment or control of tension in a tensioning element  220  even when the tensioning element is under a load. 
     In an embodiment, the secondary tensioner  322  can be arranged for use with a torque wrench that provides an indicator (e.g., a click) when a desired torque in the secondary tensioner  322  has been attained. This helps determine when an appropriate tension is applied to the residual limb during fitting of the socket system  100 . In other embodiments, the secondary tensioner  322  can comprise a worm gear unit or any other suitable mechanism. 
       FIGS. 10A-13  illustrate yet another embodiment of an adjustable socket system  400  including an alternative tightening system. The socket system  400  includes a base  402  arranged to provide support for a distal end of a residual limb, a plurality of longitudinal supports  404  connected to the base  402 , and a plurality of shell components  406  connected to the supports  404 . The shell components  406  collectively form a socket wall  408  defining a receiving volume adapted to receive the residual limb. A tightening system  414  is arranged to move the socket system  400  between open and closed configurations. 
     In the open configuration (shown in  FIG. 10A ), at least some of the longitudinal supports  404  and/or shell components  406  are free to move or be forced radially outward relative to a longitudinal axis  416  of the socket system  400 , increasing the receiving volume or increasing a circumference of the socket system  400 . This effectively loosens the fit of the socket system  400  on a residual limb inserted in the receiving volume or decreases the loading of the residual limb from the socket wall  408 . In the closed configuration (shown in  FIG. 10B ), at least some of the longitudinal supports  404  and/or the shell components  406  are moved or forced radially inward relative to the open configuration, decreasing the receiving volume or decreasing the circumference of the socket system  400 . This tightens or secures the fit of the socket system  400  on the residual limb and/or increases the loading on the residual limb from the socket wall  408 . 
     The tightening system  414  includes the tensioning unit  418 , one or more tensioning elements  420  operatively coupled to the tensioning unit  418 , and one or more secondary tensioners  422  operatively coupled to the tensioning elements  420 . The tensioning elements  420  may be formed of line, cord, wire, string, combinations thereof, or any other suitable element. 
     The tensioning elements  420  can be routed through a plurality of guides  424  on the shell components and/or the supports. For instance, the tensioning elements  420  can extend from the tensioning unit  418  through a guide  426  on a lateral support  404 B, which, in turn, directs the tensioning elements  420  through upper and lower guides  428 A,  428 B located along or near leading edges  430  of a medial shell component  106 A. The guide  426  can be integrated into or attached to the lateral support  404 B. As seen, the guide  426  can define linear and/or curved pathways that direct the tensioning elements  420  between the tensioning unit  418  and the guides  428 A,  428 B on the medial shell component  106 A. 
     In an embodiment, the tensioning elements  420  include a first tensioning element  420 A forming a first loop over a distal posterior region of a lateral aspect of the socket system  400 , a second tensioning element  420 B forming a second loop over a distal anterior region of the lateral aspect, a third tensioning element  420 C forming a third loop over a proximal anterior region of the lateral aspect, and a fourth tensioning element  420 D forming a fourth loop over a proximal posterior region of the lateral aspect. Increasing tension in the tensioning elements  420 A,  420 B,  420 C, and  420 D reduces the circumferences of the loops, which, in turn, pulls the leading edges  430  of the medial shell component  406 B together around a lateral shell component  406 A, tightening the fit of the socket system  400  on the residual limb. The tensioning elements  420  are described as forming loops but can be routed in any suitable configuration. 
     Each tensioning element  420 A,  420 B,  420 C,  420 D extends between at least one control point  436  and a movable connection point  438  on a handle  432  of the tensioning unit  418 . The at least one control point  436  can comprise the guide  426  or any other suitable point along the respective tensioning element between the shell components  406  and the tensioning unit  418 . The handle  432  defines a moment arm rotatable about a rotation axis  434  and is operatively coupled to the tensioning elements  420 . The rotation axis  434  is defined by a mounting bracket  490  mounting the handle  432  to the lateral support  404 B. Like in other embodiments, the socket system  400  can be easily opened and closed with a simple manipulation of the tensioning unit  418  between on and off positions. In the off position (shown in  FIG. 10A ), slack or lower tension levels in the tensioning elements  420  can allow the system to move toward the open configuration. 
     In the on position (shown in  FIG. 10B ), the handle  432  effectively pulls and/or shortens the length of the tensioning elements  420  forming the loops, which, in turn, tensions the tensioning elements  420  and the shell components  406  to move the socket system  400  to the closed configuration. More particularly, movement of the handle  432  from the off position to the on position shifts the movable connection point  438  away from the control point  436  which, in turn, displaces the tensioning elements  420  up or down along the longitudinal axis  416 . This tensions the tensioning elements  420  and the shell components  406  to move the socket system  400  to the closed configuration. The tensioning unit  418  can be binary so that a user can only lock the handle  432  in the on position or the off position, providing an intuitive and simple manner for users with limited dexterity or cognition to don and doff the socket system  400 . The binary configuration of the tensioning unit  418  also decreases and/or eliminates the likelihood that a user will over-tighten and/or under-tighten the socket system  400  on the residual limb, enhancing safety and comfort. According to a variation, the binary configuration of tensioning unit  418  permits the user to only lock the handle  432  in the on position. 
     According to a variation, the tightening system  414  provides a closing effect on the handle  432 . For instance, the location of the tensioning elements  420 A,  420 B,  420 C,  420 D extending between the movable connection point  438  and the control point  436  is posterior to a longitudinal axis of the handle  432  when the handle  432  is in the on position as seen in  FIG. 10B . This pulls the handle  432  in a closing or posterior direction P when the handle  432  moves toward the on position, providing a closing effect on the handle  432 . This beneficially helps ensure that the handle  432  enters the on position and decreases the likelihood that the handle  432  will be accidentally dislodged due to impact from external objects. It also beneficially decreases the physical effort of putting the handle into the on position. 
     Referring to  FIGS. 11A and 11B , the amount of displacement generated by the tensioner unit  418  can be varied by controlling one or more geometric relationships between the handle  432 , the tensioning elements  420 , and/or the mounting bracket  490 .  FIG. 11A  schematically shows the handle  432  in the off position and  FIG. 11B  schematically shows the handle  432  in the on position. 
     The ability of the tensioner unit  418  to displace the tensioning elements  420  can be at least in part dependent on a distance L 1  defined between the rotation axis  434  and the control point  436  or guide  426 , a distance L 2  defined between the rotation axis  434  and the movable connection point  438 , a distance L 3  defined between the rotation axis  434  and a free end of the handle  432 , and an angle B defined between the horizontal and the handle  432 . For example, an increase in the angle B can increase the amount of displacement of the tensioning elements  420 . An increase of the ratio between L 3  and L 2  can increase mechanical advantage for a user. The amount of displacement of the tensioning elements  420  can tend to increase when L 1  increases. An increase of L 1  tends to cause the amount of displacement of the tensioning element  420  to depend more on L 2 . 
     Referring again to  FIGS. 10A and 10B , the secondary tensioners  422  provide adjustment or control of tension in the tensioning elements  420  independent of the tensioning unit  418 . For example, when the tensioning unit  418  is in the on position and the socket system  400  is in the closed configuration, a CPO can manipulate at least one of the secondary tensioners  422  to fine tune the fit or loading of the socket system  400  on the residual limb. The secondary tensioners  422  can comprise a first secondary tensioner  422 A connected to the first tensioning element  420 A, a second secondary tensioner  422 B connected to the second tensioning element  420 B, a third secondary tensioner  422 C connected to the third tensioning element  420 C, and a fourth secondary tensioner  422 D connected to the fourth tensioning element  420 D. 
     The secondary tensioners  422  are thus connected to different tensioning elements  420 , which, in turn, allows the loading or fit of the socket system  400  to be proportionally or differentially adjusted. For example, the first and second secondary tensioners  422 A,  422 B and the third and fourth secondary tensioners  422 C,  422 D can be operable independent from one another such that a distal region of the socket system  400  can be controlled or adjusted independent of a proximal region of the socket system  400 . In other embodiments, the third secondary tensioner  422 C and the fourth secondary tensioner  422 D can be operable independent from one another such that a proximal anterior region of the socket system  400  can be controlled or adjusted independent of a proximal posterior region of the socket system  400 . The secondary tensioners  422  thus allow for fine tuning and localized adjustments of the socket system  400  when it is loaded or in the open configuration. 
     In the illustrated embodiment, the secondary tensioners  422  are worm-gear units. Referring to  FIG. 12 , each worm gear unit  422  can include a spool  451  having a worm wheel  453  arranged to mesh with an elongate worm member  455  located within a housing  457  (shown in  FIG. 10B ). A single tensioning element  420  can be attached to the spool  451  or two or more tensioning elements  420  can be attached to the spool  451 . 
     In use, a CPO can use a tool to turn the worm member  455 , which, in turn rotates the worm wheel  453  and spool  451 . When the worm member  455  rotates in a tightening direction, the tensioning element  420  is drawn into the housing  457  and is wound around the spool  451 . As the tensioning element  420  is wound around the spool  451 , tension in the tensioning element  420  increases, causing the socket system  400  to tighten independent of the tensioning unit  418 . When the worm member  455  rotates in a loosening direction, the tensioning element  420  unwinds from the spool  451  and at least part of the tensioning element  420  exits the housing  457 . As the tensioning element  420  unwinds from the spool  451 , tension in the tensioning element  420  decreases, loosening the socket system  400  independent from the tensioning unit  418 . While the secondary tensioners  422  are described as worm gear units, in other embodiments the secondary tensioners  422  can comprise other dial tensioners or any other suitable mechanism. 
     The tensioning unit  418  may include at least one elastic element to permit automatic volume adjustment of the socket system  400 .  FIG. 13  schematically illustrates a volume adjustment system comprising an elastic element  474  located within a grip portion  432 B of the handle  432  according to an embodiment. As described above, loading and unloading of the elastic element  474  by the tensioning elements  420  can deflect (e.g., shorten or elongate) the elastic element  474 , which, in turn, can adapt or adjust the fit of the socket system  400  to better match the residual limb. 
     As seen, the elastic element  474  is positioned within a housing unit  433  and loaded between an end of the housing unit  433  and a loading member  494 . The housing unit  433  is positioned within the grip portion  432 B. The tensioning element  420  is connected to the loading member  494  and extends from the loading member  494  through a center of the elastic element  474  and out of the grip portion  432 B via an opening in the end of the grip portion  432 B. It will be appreciated that the housing unit  433  can be omitted and the elastic element  474  can be loaded within the grip portion  432 B or located outside of the handle  432 . 
     In use, when the tensioning element  420  is tensioned in a direction Y it forces the loading member  494  in the direction Y, loading the elastic element  474  between the loading member  494  and the end of the housing unit  433 , which, in turn, deflects or shortens the elastic element  474 . Within an elastic range of the elastic element  474 , the amount of deflection or shortening of the elastic element  474  increases with the magnitude of load on the elastic element  474 . Like in other embodiments, this shortening effectively increases the length of the tensioning element  420  outside of the grip portion  432 B, allowing for an increased circumference of the socket system  400  when the socket system  400  enters the closed configuration. This allows the socket system  400  to more comfortably fit residual limbs of different sizes and automatically adjust the volume of the socket system  100  to match that of the residual limb. 
     Optionally, the tensioning unit  418  can include a lockout system that fixes the length of the elastic element  474  once the tensioning unit  418  is in the on position. This makes it so that the elastic element  474  cannot deflect when locked out, which, in turn prevents the elastic element  474  from varying the volume of the socket system  400  when the socket system  400  is in the closed configuration. In other embodiments, the elastic element  476  is arranged such that the input force required to move the handle  432  between the off and on positions is generally constant over the range of motion of the handle  432 . For instance, the elastic element  474  can comprise a constant force spring. 
     In other embodiments, the tensioning elements  420 A,  420 B,  420 C,  420 D can be connected to four corresponding elastic or spring elements  474  within the grip portion  432 B. This allows the fit or the forces applied to different regions of the residual limb by the tensioning elements  420  to be different when the tensioning unit  418  is in the on position. It will be appreciated that the elastic element  474  can comprise compression springs, constant force springs, pre-tension springs, variable tension springs, combinations thereof, or any other suitable elastic element. 
     Referring to  FIG. 14 , the grip portion  432 B can include a feedback system for communicating an amount of tension present in the tensioning elements  420  or loads on the elastic element  474 . For instance, the grip portion  432 B can define an observation window  496  for visually observing loading of the elastic element  474 . The grip portion  432 B can include a series of indicators  498 A,  498 B,  498 C located along the observation window  496 . If the elastic element  474  is maximally loaded or compressed, the loading member  494  can substantially align with the indicator  498 A, alerting the user or clinician that volume adaption of the tensioning unit  418  is exceeded and that the socket system  400  no longer fits safely. 
     If the elastic element  474  is minimally loaded or compressed, the loading member  494  can substantially align with the indicator  498 C. If loading or compression of the elastic element  474  is between the maximum and minimal loading, the loading member  494  can substantially align with indicators  498 B. The tightening system  414  can thus communicate to the user almost immediately how much tension is present in the tensioning elements or how much volume adaptation is occurring, improving user comfort and safe use. In other embodiments, the user can observe via the observation window  496  either of two differently colored regions. One color indicates that volume adaption of the tensioning unit  418  is exceeded and that the socket system  400  no longer fits safely. The other color indicates that the volume adaption of the tensioning unit  418  is in a safe range. 
     It will be appreciated that while the elastic element  474  is described as being carried within the grip portion  432 B, the elastic element  474  can be carried within any structure, such as on one of the longitudinal supports  404 . Moreover, while the tightening system  414  is generally described on the lateral aspect of the socket system  400 , the tightening system  414  can be adapted for use on the medial, anterior, or posterior aspect of the socket system  400  to achieve the same or similar benefits. 
       FIGS. 15A and 15B  illustrate a tensioning unit  518  according to another embodiment including a force mechanism  501  that can be adapted for use with different adjustable socket embodiments of the present disclosure. The force mechanism  501  is arranged such that the input force required to move the tensioning unit  518  between the off and on positions is substantially constant. The force mechanism  501  can be incorporated in the handle or can be located near the handle. 
     In an embodiment, the force mechanism  501  includes a first pulley  503  and a second pulley  505 . The first pulley  503  can be larger than the second pulley  505 . A first elongate element  507  is wound around the first pulley  503  and a second elongate element  509  is wound around the second pulley  505 . An elastic or spring element  511  attaches an end of the second elongate element  509  to an anchor point  513 . The second pulley  505  is fixed in position relative to the first pulley  503  and is offset from a center  515  of the first pulley  503 . 
     When the first and second pulleys  503 ,  505  are rotated in a first direction via the first elongate element  507  or a handle of the present disclosure, the second elongate element  509  is wound onto the second pulley  505 . This winding of the second elongate element  509  extends the spring element  511 . The force in the spring element  511  linearly increases with its extension. A distance from a periphery of the second pulley  505  when the first elongate element  507  is tangent decreases when the pulleys  503 ,  505  are rotated in the first direction. This counters the increasing tension-force in the spring element  511 , resulting in a substantially constant required force to rotate the first pulley  503  or move a tensioning unit  518  between the on and off positions via the constant force mechanism  501 . 
       FIG. 16  illustrates a tensioning unit according to another embodiment including a force mechanism  601 . It will be appreciated that the force mechanism  601  can be adapted for use with any the embodiments described herein. The force mechanism  601  includes a pulley assembly  603  loaded onto a bearing  605  by a spring member  607  and defining a winding surface  609 . The compression force from the spring member  607  can be adjusted by manipulating an adjustment screw  611 . 
     The pulley assembly  603  is arranged to rotate freely on the bearing  605  in a first direction and only to rotate on the bearing  605  in a second direction opposite the first direction when the applied torque overcomes frictional forces acting on the pulley assembly  603  due to the compression from the spring member  607 . This allows an elongate element  619  to be unwound from the winding surface  609  with a constant force. A gear member  613  carries an elastic element and defines a first plurality of teeth  615  interacting with a second plurality of teeth  617  on the pulley assembly  603 . The elastic element can comprise a clock spring or any other suitable elastic element. 
     When the pulley assembly  603  is rotated by pulling the elongate element  619  or via a handle attached to the pulley assembly  603 , the interaction between the teeth  615 ,  617  rotates the gear member  613 , which, in turn, winds or loads the elastic element of the gear member  613 . When the force in the elongate element  619  is released or reduced enough the spring in the gear member  613  can unwind and rotate the pulley assembly  603  in the first direction, pulling the elongate element  619  back onto the winding surface  609 . This results in a substantially constant required force to rotate the pulley assembly  603  or move the tensioning unit between the on and off positions. 
       FIG. 17  illustrates an adjustable socket system  700  according to yet another embodiment. The socket system  700  is similar to other embodiments of the present disclosure including a base  702  arranged to provide support for a distal end of a residual limb, a plurality of longitudinal supports  704  connected to the base  702 , and a plurality of shell components  706  operatively connected to the supports  704 . The shell components  706  including a medial shell component  706 A and lateral shell component  706 B, collectively forming a socket wall  708  defining a receiving volume adapted to receive the residual limb. 
     Like in other embodiments, a tightening system  714  is arranged to move the socket system  700  between open and closed configurations and includes a tensioning unit  718 , one or more tensioning elements  720  operatively coupled to the tensioning unit  718 , and one or more secondary tensioners  722  operatively coupled to the tensioning elements  720 . The tensioning elements  720  are routed through a plurality of guides  724  on the shell components  706  and/or the supports  704  and may be formed of line, cord, wire, string, combinations thereof, or any other suitable element. 
     The guides  724  can include upper and lower guides  728 A,  728 B that form first and second loops with the tensioning elements  720  over the lateral aspect of the socket system  700 . A first tensioning element  720 A forms a first loop over a distal region of the lateral aspect of the socket system  700 , and a second tensioning element  720 B forms a second loop over a proximal region of the lateral aspect of the socket system  700 . Increasing tension in the first tensioning element  720 A and second tensioning element  720 B reduces the circumference of the loops, which, in turn, pulls the leading edges  730  of the medial shell component  706 B together, tightening the fit of the socket system  700 . While the tensioning elements  720  are described forming loops it will be appreciated that the tensioning elements  720  can be routed on the socket system  700  in any suitable configuration and on any suitable region. 
     The tensioning unit  718  includes a handle  732  defining a moment arm rotatable about a rotation axis  734  and operatively coupled to the tensioning elements  720 . The handle  732  is movable between an off position and an on position in which the handle  732  is orientated generally parallel to the lateral support  704 A. In the off position, slack can be present in the tensioning elements  720  so that the socket system  700  can move toward the open configuration. 
     In the on position, the handle  732  effectively pulls and/or shortens the length of the tensioning elements  720  forming the loops, which, in turn, tensions the tensioning elements  720  and shell members  706  to move the socket system  700  to the closed configuration. More particularly, the tensioning elements  720  on the tensioning unit  718  extend between at least one control point  736  directing the tensioning elements  720  between the tensioning unit  718  and the medial shell component  706 A and at least one movable connection point  738  on the handle  732 . The at least one control point  736  can be defined on the lateral support  704 B or any other suitable point along the tensioning elements between the shell components  706  and the tensioning unit  718 . 
     Rotation of the handle  732  from the off position to the on position, shifts the movable connection point  738  away from the at least one control point  736  in a direction along the longitudinal axis  716 , which, in turn, displaces the tensioning elements  720  downwardly along the longitudinal axis  716 . This displacement tensions the tensioning elements  720  and the shell components  706  to move the socket system  700  to the closed configuration. 
     The tensioning unit  718  can be binary such that it can only be locked or placed in the on position or the off position. The binary configuration of the tensioning unit  718  decreases and/or eliminates the likelihood that a user will over-tighten and/or under-tighten the socket system  700  on the residual limb, enhancing safety and comfort. This beneficially improves ease of use for the socket system  700 , especially for elderly users. According to a variation, the binary configuration of tensioning unit  718  permits the user to only lock the handle  732  in the on position. 
     In addition, the elongate configuration of the handle  732  provide a mechanical advantage and large gripping portion for the user, facilitating operation of the tensioning unit  718  for users with limited to little dexterity. Optionally, the tensioning unit  718  can include at least one elastic element connected to the tensioning elements  720  and arranged to permit automatic volume adjustment of the socket system  700 . In other embodiments, the elastic element can be arranged so that the input force required to move the handle  732  between the on and off positions is generally constant over the range of motion of the handle  732 . 
     Secondary tensioners  722  are located on the handle  732  and enable tension control of the tensioning elements  720  independent of the tensioning unit  718 . When the handle  732  is in the on position, the user or CPO can manipulate at least one of the secondary tensioners  722  to fine tune the fit or loading of the socket system  700  on the residual limb. The secondary tensioners  722  can include a first secondary tensioner  722 A connected to the first tensioning element  720 A and a second secondary tensioner  722 B connected to the second tensioning element  720 B. The loading or fit of the socket system  700  can thus be proportionally or differentially adjusted using the secondary tensioners  722 . For instance, the secondary tensioners  722  can be operably independent from one another such that the proximal area of the socket system  700  can be controlled or adjusted independent of the distal area of the socket system  700 . 
     In addition, the secondary tensioners  722  define the at least one movable connection point  738 , simplifying the design of the tensioning unit  718 . The secondary tensioners  722  can be a geared mechanism or any other suitable tensioning mechanism. 
     It will be appreciated that the embodiments described herein are to be regarded as exemplary only, as any adjustable socket system is possible. The features of one adjustable socket system embodiment can be combined or adapted for use with another adjustable socket system embodiment. For instance, the tensioning unit  118  can be arranged to include a volume adjustment system comprising one or more elastic elements. 
       FIGS. 18A and 18B  are schematic views of a tightening system  814  for use with an adjustable socket system  800  movable between open and closed configurations according to yet another embodiment. The tightening system  814  is similar to other embodiments including a tensioning unit  818 , one or more tensioning elements  820  arranged to interact with the tensioning unit  818 , and one or more secondary tensioners  822  operatively coupled to the tensioning elements  820 . The tensioning elements  820  are routed through a plurality of guides  824  on a shell component  806  of the adjustable socket system  800 . Each tensioning element  820  includes an end attached to a corresponding secondary tensioner  822  and interacts with at least one movable connection point  838 . 
     The tensioning unit  818  is movable between on and off positions and includes a displacement wheel  842  that is rotatable about a rotation axis  834  via a handle (see, e.g., handle  132  shown in  FIGS. 2A and 2B ) defining a moment arm or other actuator. 
     The displacement wheel  842  defines a first location point  856 A and a second location point  856 B that move along a circular path about the rotation axis  834 . The least one slide member  852  is slidably attached to a track  854  on a support base  868 . It will be appreciated that the support base  868  can be attached to or integrated into a longitudinal support or shell component of the adjustable socket system  800 . 
     The at least one slide member  852  includes first and second slide members  852 A,  852 B comprising first and second movable connection points  838 A,  838 B that interact with the tensioning elements  820 . For instance, the tensioning elements  820  can include first and second tensioning elements  820 A,  820 B having one or more segments extending between the first slide member  852 A and a first control point  836 A, and third and fourth tensioning elements  820 C,  820 D having one or more segments extending between the second slide member  852 B and a second control point  836 B. 
     A first linking member  858 A connects the first slide member  852 A to the first location point  856 A on the displacement wheel  842  and a second linking member  858 B can connect the second slide member  852 B to the second location point  856 B on the displacement wheel  842 . The first and second linking members  858 A,  858 B can be eccentrically attached to the displacement wheel  842 . The first and second linking members  858 A,  858 B can pivot around the connection between the first and second linking members  858 A,  858 B and the slide members  852 A,  852 B and/or the connection between the first and second linking members  858 A,  858 B and the displacement wheel  842 . The linking members  858 A,  858 B are shown forming an angle but can have any shape suitable to convert rotational movement of the displacement wheel  842  into translational movement of the slide members  852 A,  852 B. 
     In the off position (shown in  FIG. 18A ), tension levels or slack in the tensioning elements  820  can permit the socket system  800  to move toward the open configuration. The engagement or interaction between the tensioning elements  820  and the slide members  852 A,  852 B is such that movement of the handle from the off position to the on position (shown in  FIG. 18B ) displaces the linking members  858 A,  858 B up or down relative to the first and second control points  836 A,  836 B, which, in turn, drives the slide members  852 A,  852 B up or down along the track  854 . The movement of the slide members  852 A,  852 B along the track  854  displaces the tensioning elements  820  up or down relative to the first and second control points  836 A,  836 B, which, in turn, tensions the tensioning elements  820  and the shell components  806  to move the adjustable socket system  800  to the closed configuration. 
     The tensioning unit  818  can be binary such that it can only be locked or placed in the on position or the off position. The binary configuration of the tensioning unit  818  decreases and/or eliminates the likelihood that a user will over-tighten or under-tighten the socket system  800  on the residual limb, enhancing safety and comfort. According to a variation, the binary configuration of the tensioning unit  818  permits the user to only lock the handle in the on position. 
       FIG. 19-24  illustrate yet another embodiment of an adjustable socket system  900 . The socket system  900  includes a base  902  arranged to provide support for a distal end of a residual limb, a plurality of longitudinal supports  904  connected to the base  902 , and a plurality of shell components  906  connected to the supports  904 . The shell components  906  collectively form a socket wall defining a receiving volume adapted to receive the residual limb. The plurality of shell components  906  can include a first shell component comprising a medial shell component  906 A and a second shell component comprising a lateral shell component  906 B. It will be appreciated that in other embodiments the lateral shell component  906 B can comprise a first shell component and the medial shell component  906 A can comprise a second shell component. At least one of the shell components can have distal and proximal parts that are longitudinally displaceable with respect to one another so that a length of the socket system  900  is adjustable. 
     The plurality of longitudinal supports  904  can include a first support comprising a medial support  904 A and a second support comprising a lateral support  904 B. It will be appreciated that in other embodiments the lateral support  904 B can comprise a first support and the medial support  904 A can comprise a second support. At least one of the longitudinal supports can have distal and proximal parts that are longitudinally displaceable with respect to one another so that a length of the socket system  900  is adjustable. 
     Optionally, the socket system  900  includes an actuator  903  for locking and/or unlocking a prosthetic knee usable with the socket system  900 . For instance, the actuator  903  can comprise a lever or handle  905  movably connected to the lateral support  904 B for attachment to a lanyard associated with a locking mechanism of a prosthetic knee. A user can thus pull the lanyard via the lever or handle  905  to actuate the locking mechanism and lock and/or unlock the prosthetic knee. In an embodiment, the lever or handle  905  can be movably connected to the lateral support  904 B via a fastener  907  (e.g., a telescoping screw) slidably received within a slot  909  defined in the lateral support  904 B. 
     Similar to other embodiments, a tightening system  914  is arranged to move the socket system  900  between open and closed configurations. It will be appreciated that the tightening system  914  may include the same or similar features as described above with respect to other embodiments. In the open configuration, at least some of the longitudinal supports  904  and/or shell components  906  are free to move or be forced radially outward relative to a longitudinal axis  916  of the socket system  900 , increasing the receiving volume or increasing a circumference of the socket system  900 . This effectively loosens the fit of the socket system  900  on a residual limb inserted in the receiving volume or decreases the loading of the residual limb from the socket wall. 
     In the closed configuration, at least some of the longitudinal supports  904  and/or the shell components  906  are moved or forced radially inward relative to the open configuration, decreasing the receiving volume or decreasing the circumference of the socket system  900 . This tightens or secures the fit of the socket system  900  on the residual limb and/or increases the loading on the residual limb from the socket wall. 
     The tightening system  914  includes the tensioning unit  918 , one or more tensioning elements  920  operatively coupled to the tensioning unit  918 , and one or more secondary tensioners  922  operatively coupled to the tensioning elements  920 . The tensioning elements  920  may be formed of line, cord, wire, string, combinations thereof, or any other suitable element. 
     The tensioning elements  920  can be routed through a plurality of guides  924  on the shell components  906  and/or the supports  904 . For instance, the tensioning elements  420  can extend from the tensioning unit  918  through guides  924  on the shell components  906  and the secondary tensioners  922 , which, in turn, direct the tensioning elements  920  to a plurality of end stops  926  integrated in a lateral shell component  906 B of the shell components  906 . The end stops  926  may be arranged such that an end portion of the tensioning elements  920  can be securely attached to the lateral shell component  906 B via a knot, concealing and protecting the end portions of the tensioning elements  920  with the lateral shell component  906 B. 
     Similar to other embodiments, the secondary tensioners  922  enable tension control of the tensioning elements  920  independent of the tensioning unit  918 . This allows for adjustment or control of tension in the tensioning elements  920  even when the tensioning elements  920  are under a load. For instance, when the tensioning unit  918  is in an on position, a clinician or CPO can manipulate at least one of the secondary tensioners  922  to fine tune the fit or loading of the socket system  900  on the residual limb. If the fit of the socket system  900  is too loose, at least one of the secondary tensioners  922  can be manipulated to decrease the length of at least one of the tensioning elements  920  and thereby increase tension in the tensioning element  920 . If the fit of the socket system  900  is too tight, at least one of the secondary tensioners  922  can be manipulated to increase the length of at least one of the tensioning elements  920  and thereby decrease tension in the tensioning elements  920 . 
     According to a variation, the secondary tensioners  922  include a first secondary tensioner  922 A arranged to provide adjustment to a posterior distal region of the socket system  900 , a second secondary tensioner  922 B arranged to provide adjustment to a posterior proximal region of the socket system  900 , a third secondary tensioner  922 C arranged to provide adjustment to an anterior proximal region of the socket system  900 , and a fourth secondary tensioner  922 D arranged to provide adjustment to an anterior distal region of the socket system  900 . It will be appreciated that in other embodiments the secondary tensioners  922  can adjust different regions of the socket system  900  and/or can include any suitable number of secondary tensioners. 
     The socket system  900  can be easily opened or closed with a simple manipulation of the tensioning unit  918  between off and on positions, respectively. In an embodiment, the tensioning unit  918  comprises a handle  932  defining a moment arm rotatable about a rotation axis  934  and operatively coupled to the tensioning elements  920 . In the off position, slack or low tension levels in the tensioning elements  920  can allow the socket system  900  to move toward the open configuration. In the on position, the handle  932  effectively pulls and/or shortens the length of the tensioning elements  920  extending between the guides  924 , which, in turn, tensions the tensioning element  920  and the shell components  906  to move the socket system  900  to the closed configuration. 
     The tensioning elements  920  can be connected to the tensioning unit  918  via at least one movable connection point  938  (shown in  FIG. 21 ) that translates or shifts toward and away from at least one control point that directs the tensioning elements  920  between the tensioning unit  918  and the shell components  906  and/or the longitudinal supports  904 . This shifting or translation of the movable connection point  938  relative to the at least one control point displaces the tensioning elements  920  extending from the tensioning unit  918  up or down along the longitudinal axis  916 . In an embodiment, the movable connection point  938  can be operatively associated with the handle  932  and the at least one control point can be associated with the lateral shell component  906 B and/or the lateral support  904 B. It will be appreciated that the at least one control point can comprise at least one of the guides  924 , at least one of secondary pulley assembly described below, a fixed point along an outer surface of the lateral shell component  906 B, fix point along the inner surface of the lateral support  904 B, at least one fastener, combinations thereof, or any other fixed point spaced or distinct from movable connection points  938 . 
     Movement of the handle  932  from the off position to the on position shifts the movable connection point  938  away from the at least one control point, which, in turn, displaces the tensioning elements  920  up or down along the longitudinal axis  916 . This tensions the tensioning elements  920  and the shell components  906  to move the socket system  900  to the closed configuration. Because the handle  932  defines a moment arm it provides the user a mechanical advantage, as it requires less user strength to move the tensioning unit  918  between the on position and the off position. 
     The tensioning unit  918  can have a binary configuration such that a user can only position and/or lock the handle  932  in the on position or the off position. Or in other words, the tensioning unit  918  is either on or off, providing an intuitive and simple manner for uses with limited dexterity or cognition to don and doff the socket system  900 . The binary configuration of the tensioning unit  918  also controls the basic fit of the socket system  900  on the residual limb rather than requiring the user to precisely fit the system with straps or dial tensioners, as in the prior art. According to a variation, the binary configuration of tensioning unit  918  permits the user to only lock the handle  932  in the on position. Similar to other embodiments, the tightening system  914  may be arranged to provide a closing effect on the handle  932 . For instance, at least one of the tensioning elements  920  can be arranged to pull the handle  932  toward the on position. 
     In the illustrated embodiment, the handle  932  includes a connecting portion  932 A and a grip portion  932 B connected to the connecting portion  932 A and curving toward the medial support  904 A. The orientation and arrangement of grip portion  932 B provides a large and ergonomic gripping area for the user, making operation of the handle  932  easier for users with limited dexterity. Moreover, the elongate configuration of the connecting portion  932 A provides a user with greater mechanical advantage, requiring less user strength to move the tensioning unit  918  between the on position and off position. The handle  932  can be formed of any suitable material such as metal, plastic, carbon fiber, combinations thereof, or any other material which would provide sufficient strength to resist unwanted deformation during use or accidental contact with external objects. 
     When the handle  932  is in the on position, the connecting portion  932 A extends downwardly and the grip portion  932 B wraps around an anterior side of the base  102 . This beneficially locates the grip portion  932 B substantially adjacent the base  902  and below the shell components  906 , lowering the general profile of the handle  932  on the socket system  900  and reducing the risk of it being dislodged by accidental contact with external objects. 
     Referring still to  FIG. 19 , the handle  932  is connectable to a displacement member comprising a displacement wheel  942  rotatably mounted between the lateral support  904 B and the lateral shell component  906 B. In an embodiment, the displacement wheel  942  can be rotatably mounted on an inner surface  925  (shown in  FIG. 25 ) of the lateral support  904 B and can include an attachment portion  960  positioned in a through-hole  923  defined in the lateral support  904 B. 
     The handle  932  can be connected to the displacement wheel  942  via a plate member  944  and at least one fastener  917 . For instance, the handle  932  can be attached to the displacement wheel  942  via the at least one fastener  917  received in a fastener hole  919  defined in the attachment portion  960  extending through the through-hole  923  formed in the lateral support  904 B, and to the plate member  944  via a second plurality of fasteners  915 . The plate member  944  can be attached to the displacement wheel  942  via an opening  948  formed in the plate member  944 . The plate member  944  thus forms a connection with both the handle  932  and the displacement wheel  942 , and the handle  932  is connected directly to the displacement wheel  942  via the at least one fastener  917 , enhancing a strength of the connection between the handle  932  and the displacement wheel  942 . Movement of the handle  932  between the on position and the off position rotates the displacement wheel  942  about the rotation axis  934 . 
     The opening  948  of the plate member  944  is sized and shaped to correspond to a portion of the attachment portion  960  such that the plate member  944  and the displacement wheel  942  rotate together about the rotation axis  934 . For instance, the opening  948  and the attachment portion  960  can define corresponding shapes having parallel linear portions such that engagement between the attachment portion  960  of the displacement wheel  942  and the plate member  944  in the opening  948  can help rotate the displacement wheel  942  about the rotation axis  934 . It will be appreciated that the opening  948  and the attachment portion  960  can define any suitable shapes. Optionally, the plate member  944  can define a cutout  921  configured to reduce the weight of the plate member  944 . 
     According to a variation, the opening  948  in the plate member  944  is arranged to at least in part define a range of motion of the handle, which, in turn, at least in part defines displacement of the tensioning elements  920 . For instance, varying the orientation of the opening  948  in the plate member  944  can vary the position of the handle  932  relative to the displacement wheel  942  and/or the socket system  900 . This is turn can adjust the amount of rotation of the handle  932  required to move the tensioning unit  918  between the on position and the off position, which adjusts the displacement of the tensioning elements  920  between the on position and the off position. 
     The plate member  944  can be configured so that it can attach the handle  932  to the displacement wheel  942  for use by a right handed or left handed user. For instance, the plate member  944  can be symmetric and the opening  948  can be arranged so that the same plate member  944  can be used to attach a right or left handed handle  932  by simply turning the plate member  944 . Optionally, the plate member  944  can include one or more visual indicators  951  for indicating to a user whether the plate member  944  is in a right handed configuration or a left handed configuration. The plate member  944  may have a trapezoidal configuration with an elliptical end or any other suitable shape. 
     As noted above, the displacement wheel  942  can be rotatably mounted along an inner surface  925  of the lateral support  904 B. This beneficially allows the structure of the lateral support  904 B and/or the lateral shell component  906 B to substantially conceal and protect the displacement wheel  942  including the movable connection points  938 A,  938 B, reducing the likelihood of accidental contact between the displacement wheel  942  and external objects and improving aesthetics of the adjustable socket system  900 . Further, positioning the displacement wheel  942  along the inner surface of the lateral support  904 B, helps protect a user from pinch points associated with the displacement wheel  942  as the displacement wheel  942  rotates about the rotation axis  934 . 
     For instance,  FIG. 20  shows that an inner surface  925  of the lateral support  904 B defines a first recessed portion  927  sized and configured to receive the displacement wheel  942 . The first recessed portion  927  allows the lateral support  904 B to carry the displacement wheel  942  and/or distribute forces exerted on the lateral support  904 B and/or the lateral shell component  906 B. When the displacement wheel  942  is positioned in the first recess  927 , at least a portion of the attachment portion  960  of the displacement wheel  942  can protrude through the through-hole  923  in the lateral support  904 B for selectively attaching the displacement wheel  942  to the plate  944  and the handle  932 . 
     According to a variation, a bearing member  929  is positionable in the first recessed portion  927  between a bottom of the first recessed portion  927  and the displacement wheel  942 . The bearing member  929  is arranged to reduce friction and distribute forces as the displacement wheel rotates relative to the lateral support  904 B. The bearing member  929  is shown having a circular shape corresponding to the shape of the first recessed portion  927 . The bearing member  929  includes a central opening  931  through which the attachment portion  960  can pass and may define an annular flange  933  surrounding the central opening  931  to help maintain the position of the of the bearing member  929  in the first recessed portion  927 . 
     The inner surface  925  of the lateral support  904 B may define other recessed portions for accommodating components of the tightening system  914  and/or reducing the overall weight of the lateral support  904 B. For instance, a second recessed portion  935  having an elongate configuration can extend from the first recessed portion  927  in a distal direction. The second recessed portion  935  can have a width that tapers in the distal direction and can accommodate at least one secondary pulley assembly described below. A third recessed portion  937  having an elongate configuration can extend from first recessed portion  927  in a proximal direction opposite the second recessed portion  935 . The third recessed portion  937  can be sized and configuration to accommodate at least one secondary pulley assembly described below. 
     In an embodiment, a pair of recessed portions  939  are defined along the inner surface  925  on opposite sides of the third recessed portion  937 . These recessed portions  939  can at least in part accommodate the secondary tensioners  922  along the inner surface  925  of the lateral support  904 B, which, in turn helps conceal and protect the secondary tensioners  922 . It will be appreciated that the inner surface  925  can further define a plurality of holes  941  for securing the secondary tensioners  922  between the lateral support  904 B and the lateral shell  906 B via one or more fasteners  945  (shown in  FIG. 22 ). Further, the secondary tensioners  922  can be accessible via openings defined in the lateral support  904 B. While the displacement wheel  942  is described being mounted between the lateral support  904 B and the lateral shell component  904 A, in other embodiments, the displacement wheel  942  can be rotatably mounted between the medial support  904 A and the medial shell component  906 A, or between other components of the socket system  900 . In other embodiments, the displacement wheel  942  can be mounted along an inner surface of the lateral shell component  906 B or the medial shell component  906 A. 
       FIG. 21  shows the displacement wheel  942  according to an embodiment. Similar to other embodiments, the displacement wheel  942  defines the attachment portion  960  for attachment to the handle  932  and includes a first movable connection point  938 A comprising a first pulley assembly  950 A extending between a first plate  962  and a second plate  964 , and a second movable connection point  938 B comprising a second pulley assembly  950 B extending between the second plate  964  and a third plate  966 . As such, the displacement wheel  942  positions the first and second movable connections points  938 A,  938 B between the lateral support  904 B and the lateral shell component  904 A. 
     The attachment portion  960  can define a height arranged to extend from the inner surface  925  of the lateral support  904 B, through the opening  923 , and into engagement with the plate  944  positioned on the outside of the lateral support  904 B. Optionally, the attachment portion  960  of the displacement wheel  942  can define an annular groove  943  arranged to selectively receive a retaining ring for selectively preventing the displacement wheel  942  from being axially withdrawn from the opening  923 . 
     The first and second pulley assemblies  950 A,  950 B can be radially offset relative to the longitudinal axis  916 . For instance, they can be at different levels on the displacement wheel  942  such that rotation of the of the displacement wheel  942  moves the first pulley assembly  950 A in an arcuate or circular path with the second pulley assembly  950 B moving in an arcuate or circular path above the first pulley assembly  950 A. Having first and second pulley assemblies  950 A,  950 B at different levels on the displacement wheel  942  permits at least some of the tensioning elements  920  to be separated from one another during use of the tensioning unit  918 . For example, first and second tensioning elements can be connected to the first pulley assembly  950 A, and third and fourth tensioning elements can be connected to the second pulley assembly  950 B. This helps reduce friction on the tensioning elements  920 , which, in turn, decreases physical effort needed to move the handle  932  to the on position. The reduction in friction also decreases wear and tear on the tensioning elements  920  and components in contact with the tensioning elements  920 . 
     The first and second pulley assemblies  950 A,  950 B can be angularly offset relative to one another. For instance, the first and second pulley assemblies  950 A,  950 B can be offset about 180 degrees or by some other angular distance. This helps ensure that when the handle  932  is moved to the on position both lower tensioning elements and the upper tensioning elements are tensioned. 
     The angular offset between the first and second pulley assemblies  950 A,  950 B can also form a constant force mechanism so that the input force required to move the handle  932  between the on and off positions is substantially constant over the range of motion of the handle  932 . For example, as the tensioning unit  918  moves between the on and off positions, the forces on the first and second pulley assemblies  950 A,  950 B from the tensioning elements  920  can generally oppose one another so that an input force required to move the handle  932  is substantially constant over the range of motion of the handle  932 . This can help facilitate operation of the tightening system  914  for users with limited strength and/or dexterity. 
     While the displacement wheel  942  is described having two pulley assemblies and two different levels, it will be appreciated that in other embodiments the displacement wheel  942  can include one, three, four, or any other suitable number of pulley assemblies and/or levels. Moreover, the pulley assemblies may be arranged to rotate about an axis or may be fixed between adjacent plates. 
     As seen in  FIG. 22 , the tensioning unit  918  may include one or more secondary pulley assemblies  947  configured to vary the direction of the tensioning elements  920  and tension therein. When the tensioning elements  920  are looped around the one or more second pulley assemblies  947  and the tensioning unit  918  or the handle  932  is moved from the off position to the on position, the one or more secondary pulley assemblies  947  can direct tensioning elements  920  extending from the movable connection points  938 A,  938 B or the displacement wheel  942  back toward the displacement wheel  942 , enhancing displacement of the tensioning elements  920 . This enhanced displacement beneficially helps the movement of the handle  932  and the movable connection points  938 A,  938 B to increase tension in the tensioning elements  920  and the shell components  906  to move the socket system  900  to the closed configuration. 
     In an embodiment, the one or more secondary pulley assemblies  947  are separate from the displacement wheel  942 . The one or more secondary pulley assemblies  947  can include a first secondary pulley assembly  947 A proximal to the displacement wheel  942  and a second secondary pulley assembly  947 B distal to the displacement wheel  942 . The first and secondary pulley assemblies  947 A,  947 B can be attached to the lateral shell component and each can include one or more pulleys  949  arranged for engagement with the tensioning elements  920 . The one or more pulleys  949  may be fixed such that the tensioning elements  920  slide over the one or more pulleys  949  as the tensioning elements  920  are tensioned. In other embodiments, the one or more pulleys  949  may be arranged to rotate on a pin or rotation axis such that the tensioning elements  920  spin the one or more pulleys  949  as the tensioning elements  920  are tensioned, decreasing friction. 
     Each secondary pulley assembly  947 A,  947 B may include one, two, three or any other number of suitable pulleys  949 . In an embodiment, the secondary pulley assemblies  947 A,  947 B include a pair of pulleys  949 , each pulley  949  being arranged for different ones of the tensioning elements  920 . While the one or more secondary pulley assemblies  947  are described including two secondary pulley assemblies, in other embodiments, the one or more secondary pulley assemblies can include one, three, or any other suitable number of secondary pulley assemblies. Further, it will be appreciated that the one or more secondary pulley assemblies  947  may be incorporated with any tensioning system embodiments of the present disclosure. 
       FIGS. 23 and 24  illustrate a secondary tensioner  922  according to another embodiment. The secondary tensioner  922  includes a housing  976 , a plurality of spools  978 , and a base  968 . The plurality of spools  978  can comprise a pair of spools  978 A,  978 B. The pair of spools  978 A,  978 B are situated within receiving spaces  953 A,  953 B defined by the housing  976  such that the spools  978 A,  978 B are rotatable relative to the housing  976 . The housing  976  can be connected to the base  968  and can include one or more side portions  977  extending outward and defining cutouts  979  for receiving fasteners to attach the secondary tensioner to at least one of the longitudinal supports  904 . Tensioning elements  920  (shown in  FIG. 19 ) can be attached to the spools  978 A,  978 B via an opening  982  formed in the housing  976 . In an embodiment, the opening  982  has a flared and curved configuration arranged to reduce friction between the tensioning elements  920  and the base  968 . Sidewalls of receiving spaces  953 A,  953 B can extend partially around the spools  978 A,  978 B such that a base receiving space  975  is defined by the housing  976  to accommodate a portion of the base  968  including the flared opening  982   
     When at least one of the spools  978  rotates in a tightening direction, at least one of the tensioning elements  920  is drawn into the opening  982  and is wound around the spool  978 . As the tensioning element  920  is wound around the spool  978 , tension in the tensioning element  920  increases, causing the socket system  900  to tighten. When the spool  978  rotates in a loosening direction, the tensioning element  920  unwinds from the spool  978  and at least part of the tensioning element  920  exits the opening  982 . As the tensioning element  920  unwinds from the spool  978 , tension in the tensioning element  920  decreases, loosening the socket system  900  (shown in  FIG. 19 ). 
     A pair of spring members  984  are positionable between the spools  978 A,  978 B and the lateral support  904 B that force an upper surface  955  of the spools  978 A,  978 B into engagement with a bottom surface  957  of the receiving spaces  953 A,  953 B. 
     The spools  978 A,  978 B define corresponding engagement features  959 ,  961  arranged to only allow the spools  978 A,  978 B to rotate relative to the housing  976  via an external input. For instance, the engagement features  959  on the spools  978 A,  978 B can comprise a plurality of pin members  963  circumferentially distributed around the upper surface  955  and the engagement features  961  on the bottom surface  957  of the receiving spaces  953 A,  953 B can comprise a plurality of holes  965  defined in the bottom surface  957  and corresponding to the plurality of pin members  963 . At least some of the plurality of pin members  963  can have a rounded configuration. The interaction between the pin members  963  and the holes  965  is arranged to selectively prevent relative rotation between the spool  978  and the housing  976 . 
     An upper portion of the housing  976  defines a pair of cylinders  986  having a hollow configuration in communication with the receiving spaces  953 A,  953 B and the spools  978 A,  978 B define corresponding sockets  988  positionable in the cylinder  986 , each arranged to receive a tool member (e.g., a wrench or key) so that a CPO or user can rotate one or more of the spools  978 A,  978 B to adjust tension in the respective tensioning elements  920 . A notch  971  can be defined in an upper portion of the socket  988  for providing a user or CPO a visual indicator of displacement of the tensioning element  920 . 
     According to a variation, the interaction between the holes  965  and the pin members  963  is such that the likelihood of the spools  978 A,  978 B being locked or positioned on the upper surface  955  between the holes  965  is reduced. For instance, the upper opening of at least some of the holes  965  can define a chamfered edge  967  arranged to facilitate insertion of the pin members  963  in the holes. More particularly, spacing between the holes  965  and the chamfered edge  967  are arranged so that the pin members  963  more easily slide into the holes  965  when the CPO or user rotates the spool via an external input, reducing a likelihood of the pin members  963  resting on the upper surface  955  outside of the holes  965 . Optionally, a collar  969  can be disposed between the socket  988  and the inner wall of the cylinder  986  to decrease friction. 
     The secondary tensioner  922  thus beneficially permits adjustment or control of tension in one or more tensioning elements  920  even when the one or more tensioning elements  920  is under a load. 
     In other embodiments, the adjustable socket system of the present disclosure can be assembled from components selected from groups of components that include shell members, struts, distal assemblies, and/or suspension systems. The components within these groups are modular, meaning that they vary in size and shape but have common connecting features. This modularity applies to assembly and also repair or reconfiguration of the assembled system, by simply switching components in and out. 
     In other embodiments, the longitudinal supports can comprise struts and/or the longitudinal supports can include three, four, or any other suitable number of supports. In other embodiments, the adjustable socket system can include anterior and posterior longitudinal supports. In other embodiments, the shell components can be omitted and the tensioning unit can be operatively coupled to the longitudinal supports to move the system between the open and closed configuration. In yet other embodiments, the longitudinal supports can be omitted and the tensioning unit can be operatively coupled to the shell components to move the system between the open and closed configuration. 
     While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting. Additionally, the words “including,” “having,” and variants thereof (e.g., “includes” and “has”) as used herein, including the claims, shall be open ended and have the same meaning as the word “comprising” and variants thereof (e.g., “comprise” and “comprises”).