Abstract:
A CPM chair for repeatedly flexing and extending a patient&#39;s knee permits a patient to remain comfortably seated while controlling therapeutic knee flexure and extension. A slide member is longitudinally reciprocal between extended and retracted positions with its slide direction controlled by the patent. A drum has an endless cable wrapped about its periphery and is rotated in alternate directions by a reversible electrical motor. The cable extends over respective forward and rearward pulleys and is secured to the slide member. A pedal assembly supports the patient&#39;s foot and is pivotally secured to the slide member to accommodate different positions of the patient&#39;s heel. Control switches are actuable by the patient to control slide member direction.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a Nonprovisional Application of Provisional Application No. 61/317,420, filed 25 Mar. 2010 and entitled “Continuous Passive Motion Systems,” the disclosure of which are hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    present invention pertains generally to continuous passive motion (CPM) device and, more particularly, to a physical therapy chair for imparting flexure to the knee of patient recovering from an injury or knee replacement surgery. 
       BACKGROUND OF THE INVENTION 
       [0003]    Injury to or surgical procedures on limbs and joints are typically followed by a period of rehabilitation in order to aid recovery. Such postoperative rehabilitation of the joint has been shown to reduce the likelihood of ligamentous and articular adhesions, thromboembolism, venos stasis, post-traumatic osteopenia, peripheral edema, and muscle atrophy. Joint rehabilitation further promotes faster healing, reduction of the amount of pain experienced, and improvement in the range of motion of the affected. Such rehabilitation generally requires that the knee be flexed and the leg be extended such as occurs in normal walking; however, it is frequently undesirable for a recovering patient to bear weight on his leg while rehabilitating his knee. In addition, when a knee has suffered a trauma or other injury, or after surgery, a person often lacks the necessary muscle control, strength, or will to flex his knee and straighten his leg. The therapeutic use of an external force to flex and extend the limb to induce motion is referred to as passive motion. Continuous passive motion (CPM) devices are typically motor driven device designed to exercise a particular joint by repeatedly extending and flexing the joint. CPM devices are capable of applying continuous motion to the joint in a repeatable, consistent manner. 
         [0004]    Conventional CPM devices for knees are generally closed systems requiring the limb to be enclosed within femoral and/or tibial supports. This is often uncomfortable for the user, since the leg is fixed along a longitudinal path that may not represent the natural flexing motion of the user&#39;s leg. In addition, many knee CPM devices require the user to be oriented in the supine position for its use. This is problematic, particularly for the elderly or users with back conditions. 
         [0005]    Consequently, there is a need for a rehabilitation device that can be used to mobilize the joint over a period of time as a part of the orthopedic care. There further remains a need for CPM devices that are simpler in construction, are easier for a patient to use, and enable a user to receive treatment while seated. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is directed toward a continuous passive motion (CPM) device operable to repeatedly flex and extend a joint (e.g., a knee) along predetermined pathway. The CPM device includes a user support, a CPM assembly, and a control unit. The user support orients a user in a non-supine (e.g., seated) position. The CPM assembly includes a carriage with a foot support that receives and supports the foot of a user. The carriage is configured to move in a reciprocal motion, traveling along a generally linear travel path. The control unit controls one or more operational parameters of the device. In operation, a user is seated on the user support, placing a foot within the foot support. The CPM device is activated (via the controller) and the carriage reciprocally travels along its travel path, extending outward from and retracting inward toward the user support, bending the knee of the user and providing rehabilitative treatment to the joint. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1A  illustrates perspective view of a continuous passive motion device in accordance with an embodiment of the invention. 
           [0008]      FIG. 1B  illustrates a perspective view of the continuous passive motion device shown in  FIG. 1A . 
           [0009]      FIG. 1C  illustrates is a side plan view of the continuous passive motion device shown in  FIG. 1A . 
           [0010]      FIG. 2  illustrates an isolated plan view of the continuous passive motion assembly shown in  FIG. 1A , with the cover removed for clarity. 
           [0011]      FIG. 3  illustrates the foot support assembly of the continuous passive motion assembly in accordance with an embodiment of the invention. 
           [0012]      FIG. 4A  illustrates a partial cross sectional view of the continuous passive motion assembly shown in  FIG. 2 , showing the drive assembly. 
           [0013]      FIG. 4B  illustrates a partial cross sectional view of the continuous passive motion assembly shown in  FIG. 2 , showing a close-up of the limit switch. 
           [0014]      FIG. 4C  illustrates a rear perspective view of the continuous passive motion assembly shown in  FIG. 2 . 
           [0015]      FIG. 5  illustrates an exploded view of the continuous passive motion assembly shown in  FIG. 2 , showing the guide rail system of the device. 
           [0016]      FIG. 6  is a schematic of the electronic components of the continuous passive motion device. 
           [0017]      FIGS. 7A and 7B  show the operation of the device, with the carriage moving from its extended position ( FIG. 7A ) to its retracted position ( FIG. 7B ) 
       
    
    
       [0018]    Like reference numerals have been used to identify like elements throughout this disclosure. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0019]      FIGS. 1A-1C  illustrate views of a continuous passive motion device (CPM) in accordance with an embodiment of the present invention. The CPM device  10  includes a user support  105 , a CPM assembly  110 , and a control unit  115 . The user support  105  is configured to support a user in a non-supine (e.g., seated position) position, as well as to position the user above the CPM assembly  110 . In the embodiment illustrated, the user support  105  includes a chair with a seat portion  120  having forward side  125 A, a rearward side  125 B, a first lateral side  125 C, and a second lateral side  125 D that cooperate to define a seating surface  130 . The user support  105  may further include a seat back portion  135  oriented generally orthogonal to and positioned above the seating surface  130 , proximate the rearward seat side  125 B. The seat portion  120  is supported above a supporting surface by one or seat support members  140  extending downward from the seat portion. In the embodiment shown, a pair of forward legs  140 A and a pair of rearward legs  140 B support the seat  120  above a supporting surface. 
         [0020]    The user support  105  further includes a lateral support member  145  disposed along at least one of the lateral sides of the user support  105 . Specifically, as seen best in  FIG. 1B , the lateral support  145  includes a lower support section  155  and an upper support section or armrest  160 . The lower support section  155  may be in form of a generally vertical wall secured to the first lateral side  125 C of the seat portion  105  via fasteners (e.g., bolts, screws, etc.). The armrest  160  is a generally horizontal platform disposed along the upper edge of the lower support section  155  and configured to support an arm of a user positioned within the user support  105 . The control unit  115  may be disposed at forward position along the upper platform section  160 . The control unit  115  may include one or more controller actuators  165  to permit the patient to selectively control the carriage (e.g., to reverse the direction of motor rotation to change the carriage direction), thereby providing the user with the ability to determine the range of the cyclical flexure and extension motion (discussed in greater detail below). 
         [0021]    The lateral support member  145  may further include a guard  170  extending transversely from the lower support section  155 . The guard  170 , substantially aligned with the forward seat edge  125 A, provides additional support for the upper platform portion  160  on the supporting surface. 
         [0022]    The CPM assembly  110  may be coupled to the user support  105  such that it may be positionally adjusted with respect to the seat portion  120 . As best seen in  FIG. 1C , the user support  105  further includes a bar  175  extending from the forward leg  140 A to the rearward leg  140 B along first lateral edge  125 C of seat portion  120 . The bar  175  includes a plurality of apertures  180  longitudinally spaced along the bar. A fastener  185  including a knob and a threaded male post is selectively inserted into the apertures  180 . A female receptacle threaded to complement the threads of the male post of the fastener  185  is formed into the cover  195  of the CPM assembly  110  (female receptacle not illustrated). The female receptacle receives the male post of the fastener  185 , releasably securing the CPM assembly  110  to the user support  105 . 
         [0023]    To adjust the longitudinal position of the CPM assembly  110  along the bar  175  (and thus the forward/rearward position of the CPM assembly with respect to the seat portion  120 ), the fastener  185  is disengaged from the CPM assembly  110  and from a first aperture of the bar. The CPM assembly  110  may then be repositioned with respect to the user support  105  by moving either the CPM assembly or the user support  105  along the supporting surface. The fastener  185  is then inserted into a second aperture that aligns with the new position of the female receptacle on the CPM assembly  110  to once again secure the user support  105  to the CPM assembly. 
         [0024]    The CPM assembly  110  is configured to continuously drive a leg from a first leg position to a second leg position. The CPM assembly  110  includes a cover  195  that hides the drive components of the device.  FIG. 2  shows a perspective view of the drive components of the CPM assembly  110  with the cover  195  removed for clarity. As shown, the CPM assembly  110  includes base or housing  200 , a carriage or sliding member  205  movably coupled to the housing, and a foot support assembly  210  coupled to the carriage. 
         [0025]    The housing  200  houses the drive assembly of the CPM device  10  within an internal cavity  212  defined by a forward wall  215 A, a rearward wall  215 B, a first lateral wall  215 C, a second lateral wall  215 D disposed opposite the first lateral wall, a top wall  215 E, and a bottom wall  215 F. The housing  200  may be elongated, and include a top wall that is angled in the housing longitudinal direction. Specifically, the height of the housing  200  may gradually decrease in the forward direction (i.e., the top wall  215 D declines in the forward direction). In an embodiment, the angle of decline measured from the rear wall  215 B to the forward wall  215 A is about 5° to about 15° (e.g., about 10°). With this configuration, the carriage  205  projects forward from the housing  200  at an angle in the range of about 5° to about 15°. 
         [0026]    The carriage may possess any size and any shape suitable for its intended purpose. In the embodiment illustrated, the carriage  205  comprises a generally inverted-U-shaped structure having a generally planar horizontal portion  220 , a first side wall  223 A and a second side wall  223 B, each side wall being oriented generally orthogonal to the horizontal portion. The carriage  205  defines a forward carriage edge  225 A and a rearward carriage edge  225 B, as well as an upper, user-facing surface  230 A and lower, housing-facing surface  230 B. The carriage  205  is arranged to slidably reciprocate longitudinally between extended and retracted positions by means of a slide mechanism (discussed in greater detail below). 
         [0027]    The foot support or pedal assembly  210  is configured to support the foot of a user. The foot support assembly is coupled to the upper carriage surface  230 A, being disposed proximate the forward carriage edge  225 A. Referring to  FIG. 3 , the foot support assembly  210  includes a foot support  300  pivotally coupled to a bracket  305  via a hinge member  310 . The foot support  300  may generally take the form of a right angle bracket, with a foot pad portion  315  and a heel portion  320  oriented generally orthogonal to the foot pad portion. The foot pad portion  315  receives the sole of the foot, while the heel portion  320  receives the heel of the foot (when the user is seated in the chair). Side walls  325 A,  325 B extend distally from the transverse edges of the foot pad  315  and heel  320  portions to limit the lateral movement of the foot within the foot support  300 , thereby containing the foot of the user within the support. 
         [0028]    The bracket  305  may be in the form of a generally L-shaped bracket having a lower bracket portion  330  and an upper bracket portion  335  oriented at an angle with respect to the lower bracket portion  330 . By way of example, the upper bracket portion  335  may be oriented at an angle of about 135° with respect to the lower bracket portion  330 . The lower bracket portion  330  may be coupled to the forward edge  225 A of the carriage  205  via fasteners  340  (e.g., bolts) such that the lower bracket portion is oriented generally orthogonal to the horizontal member  220  of the carriage. 
         [0029]    The hinge  310  enables the foot support  300  to be pivotally secured to the carriage  205  to accommodate natural movement of the user&#39;s heel during reciprocation of the carriage. In addition, the pivot arrangement may be used to fix the angle of the pedal assembly as determined by a medical professional (e.g., a physical therapist) to provide the desired level of therapy for the patient. The hinge  310  (e.g., a butt hinge), may include a first hinge plate  345  pivotally coupled to a second hinge plate  350  via a pin  355 . The first plate  345  is connected to the lower surface of the foot pad  315  along an intermediate location of the pad, while the second plate  350  is connected to the inner surface of the lower bracket portion  330  (e.g., via fasteners  360  such as rivets). 
         [0030]    The hinge  310  is secured to the bracket  305  such that the first plate  345  may pivot toward and away from the inner surface of the upper bracket portion  335  (indicated by arrow P). With this configuration, a user may adjust the angular position of the foot support  300  with respect to the bracket  305  (and thus with respect to the carriage  205 ) from a first foot support position to a second foot support position. By way of example, the foot support  300  may pivot approximately 30°. The ultimate degree of forward pivot is limited by contact between the foot pad portion  305  and the upper bracket portion  335 , while the degree of rearward pivot is limited by contact between the heel portion  320  and the carriage  205 . In addition, the degree of pivot may be selectively adjustable via a pivot adjustment mechanism that selectively adjusts the degree of pivot. The pivot adjust mechanism may be manual or may be motorized. 
         [0031]    The CPM assembly  110  includes a drive mechanism operable to reciprocally move the carriage  205  along the housing  200  (e.g., to slidably reciprocate the carriage longitudinally between extended and retracted positions). Referring to  FIGS. 4A-4C , the drive mechanism includes a drive wheel or drum  405  (e.g., a drum having a diameter of 5.5 inches) that drives a continuous (endless) cable  410  coupled to the carriage  205  (e.g., the cable may be wrapped around the periphery of the drum). The drum  405  may be generally annular, including a bar  415  extending across inner drum diameter. The bar  415  is fixed to a rotating shaft  420  driven by a gear mechanism housed in gearbox  425  that is in communication with a motor housed in motor housing  430  (e.g., a 12 volt reversible DC gear motor). The drum  405  may be rotated in alternate directions by motor  430 . Specifically, the drum may be rotated clockwise (forward) and counter-clockwise (rearward) directions by the motor  430  (indicated by R in  FIG. 4A ). 
         [0032]    The cable  410  rides on pulleys mounted along the top wall  215 E of the housing  200 . Specifically, a first or forward pulley  435 A ( FIG. 4A ) is positioned proximate the forward housing end  215 A, and a second or rearward pulley  435 B ( FIG. 4B ) is positioned proximate the rearward housing end  215 B. The cable  410  extends from the drum  405 , along housing top wall  215 E and over the rearward  435 A and forward  435 A pulleys, and then back to the drum  405 . With this configuration, as the drum  405  reciprocates rotationally the carriage reciprocates longitudinally. That is, the clockwise or counter clockwise rotation of the drum  405  generates a corresponding clockwise or counter clockwise rotation of the cable  410  along the pulleys  435 A,  435 B, which, in turn, generates the longitudinal (e.g., translating or telescoping) motion of the carriage  205 . 
         [0033]    The CPM assembly  110  further includes a slide mechanism that guides the carriage along its travel path. Referring to  FIG. 5 , the guide mechanism includes a first guide rail member  505 A and a second guide rail member  505 B each extending longitudinally along the top wall  215 E of the housing  200 . The first guide rail member  505 A is supported by a first rail support  510 A disposed proximate first lateral edge  215 C of housing, while the second guide rail member  505 B is supported by a second rail support  510 B disposed proximate the second lateral housing edge  215 D. 
         [0034]    The carriage  205 , moreover, includes complementary guide channels or extension rails that telescopingly mate with the guide rail members  505 A,  505 B on the housing  200 . Specifically a first extension rail  520 A, secured to the inner surface of the first carriage side wall  223 A, slidingly couples to the first guide rail member  505 A. Similarly, a second extension rail  520 B, secured to the inner surface of the second carriage side wall  223 B, slidingly couples to the second guide rail member  505 B. With this configuration, the carriage  205  is configured to slide longitudinally/axially along the housing  200  from a first or retracted carriage position, in which it the carriage is positioned substantially or completely over the housing  200 , to a second or extended carriage position, in which the carriage extends distally form the housing, i.e., beyond the forward wall  215 A of the housing  200 . By way of example, the rail system may include a drawer glide type system (e.g., an Accuride full extension slide, available from Accuride International Inc., Santa Fe Springs, Calif.). As noted above, the cable  410  is coupled to the carriage  205  via a carriage bracket  440  ( FIG. 4C ). Consequently, rotation of the cable  410  drives the carriage  205  along the guide channel from the first carriage position to the second carriage position. 
         [0035]    The degree of extension of the carriage  205  from the housing  200  may be any suitable for its intended purpose. By way of example, in its retracted position, the carriage  205  may be positioned substantially over the housing  200  (e.g., the front edge of the carriage may be flush with or extend slightly beyond the front edge of the housing (e.g., about 2 inches)). In its extended position, the carriage may extend beyond the front edge of the housing approximately 24 inches. Thus, in certain embodiments, the carriage  205  may be configured to possess a travel distance of in the range of about 20 to about 24 inches (e.g., about 22 inches). 
         [0036]    Limit switches may be utilized such that they are actuated if the carriage moves beyond predetermined limits to thereby disable the motor and prevent knee flexure or extension beyond safe ranges for the patient. Referring back to  FIG. 4B , a limit switch  450  may be a normally closed snap action switch disposed within a housing  455  from which an actuator arm  460  extends to a location to be engaged and actuated by the carriage  205  when the carriage reaches a predetermined position along the rails. As best seen in  FIG. 2 , a first or forward limit switch  450 A is disposed along the first housing lateral side  215 C proximate the forward housing wall  215 A, and the second or rearward limit switch  450 B is disposed along the first lateral side  215 C of housing proximate the rearward housing wall  215 B. As seen in  FIG. 4C  the carriage  205  further includes a switch engagement member  470  operable to engage the switches  450 A,  450 B as the carriage moves with respect to the housing  200 . The switch engagement member  470  is a protrusion extending laterally from the first lateral side wall  223 A of the carriage  205 , disposed along the rearward carriage edge  225 B. 
         [0037]    With this configuration, should the carriage  205  extend beyond its forward pre-set limit, the switch engagement member  470  will engage the forward limit switch  435 A, stopping the motor. Additionally, should the carriage retract beyond its rearward pre-set limit, the switch engagement member  470  will engage the rearward limit switch  435 B, stopping the motor. The limit switches  450 A,  450 B may be repositioned along the housing to alter the pre-set safety limits of the device  10 . 
         [0038]      FIG. 6  illustrates an electrical schematic of the components of the drive assembly for the CPM device  10 . As shown, the drive device  10  includes the motor  605  (e.g., a reversible 12 V DC motor) in communication with the control unit  115 , as well as the forward  450 A and rearward  450 B limit switches. The CPM device  10  is powered via a power source  610  such as a conventional AC wall outlet (via a conventional step-down transformer). Alternatively, the power source  610  may include a storage pack such as a battery. The actuator  165  on the control unit  115  may be any actuator suitable for its described purpose (to selectively drive the motor in forward and rearward directions). By way of example, the actuator  165  may be a lever-type actuator or may be a pair of momentary pushbutton switches. When the actuator  165  is actuated in its first mode, the DC voltage is applied across motor  605  in a first polarity, causing the motor to rotate in a first direction. When actuator  165  is actuated in its second mode, the polarity of the voltage applied to the motor  605  is reversed, causing the motor to rotate in the opposite direction. In this manner, the patient can alternately actuate the motor  605  to extend and retract the carriage  205  as desired to effect the desired range of knee flexure. 
         [0039]    As noted above, the limit switches  450 A and  450 B are normally closed snap action switches from which an actuator arm  460  extends to a location to be engaged and actuated by switch engagement member  470  on the carriage  205  when the carriage reaches pre-set limits. When either switch  450 A or  450 B is actuated, it interrupts the 12 volts DC applied to the motor  605 , causing rotation to stop. The motor  605  can begin rotating again only in the opposite direction upon actuation of the appropriate actuator mode. 
         [0040]    In an alternative embodiment, the control unit may be a digital control unit configured to operate the device  10  under one or more user defined and/or pre-set parameters. For example, the digital control may include a central processor in communication with one or more input buttons used to enter various operational parameters of the treatment session that are then executed by the processor. For example, the user may enter parameters such as the operational range of motion (the extension and flexion angles) the foot support angle, the speed of flexure, etc. Once the information is entered, the device  10  operates automatically to continuously flex and extend the knee. As such, the digital control unit prevents the user from having to personally change the extension and flexion directions of the carriage  205 . 
         [0041]    The operation of the device is explained with reference to  FIGS. 7A and 7B . As shown, the CPM device  110  is positioned at a predetermined location with respect to the user support  105 , i.e., the position of the CPM device  110  may be moved forward or rearward with respect to the seat  120  to adjust for the height of the user, the length of the user&#39;s leg, and/or the total available degree of flexure. A user  700  is position within user support  105  such that the user is oriented in a non-supine position (e.g., a seated position). The foot  705  of the user  700  is positioned within the foot support assembly  210 , while the leg  710  is oriented generally over the carriage  205 . The user then engages the actuator  165  of the control unit  115  (control unit not seen in  FIGS. 7A and 7B ) to activate the motor, which drives the carriage  205  along the rails such that it extends outward, from its first or retracted carriage position to its second or extended carriage position (indicated by Ex in  FIG. 7A ). In the extended position, the carriage  205  provides leg extension, extending the leg outward from the user/seat until it reaches a predetermined degree of extension (e.g., a joint angle of about 90°). In the retracted position, the carriage  205  provides leg flexion, bringing the leg inward (toward the user/seat) to bend the joint (knee) of the user until it reaches a predetermined angle of flexion (e.g., a joint angle of up to about 120°). 
         [0042]    Once the desired degree of knee extension has been obtained, the user engages the actuator  165  of the control unit  115  to switch the direction of the motor  605  to drive the carriage  205  inward, toward the user from its second/extended carriage position back to its first/retracted carriage position (indicated by Rt in  FIG. 7B ). In either direction, should the user fail to alter the direction of the carriage  205  such that the carriage extends beyond its forward or rearward pre-set limits, a limit switch  450 A,  450 B will be engaged, deactivating the motor. This process continues, with the user driving the carriage from its first position to its second position, and vice versa. 
         [0043]    Alternatively, when a digital controller is utilized, the user simply activates the power to the device, enters the operational parameters and engages the CPM assembly  110  (e.g., by engaging a START button), causing the extension and flexion as described above. 
         [0044]    The above described device provides an open CSM device, i.e., a device that does not require a tibia (upper leg) and/or femur (lower leg) support members for its operation. 
         [0045]    While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. For example, while shown as an open system, the closed system including tibial and/or femoral support members may be utilized. The degree of knee flexion provided by the device is not particularly limited. The device may be formed of any suitable material, including, but not limited to wood, plastic, metal, etc. 
         [0046]    Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. For example, it is to be understood that terms such as “left”, “right” “top”, “bottom”, “front”, “rear”, “side”, “height”, “length”, “width”, “upper”, “lower”, “interior”, “exterior”, “inner”, “outer” and the like as may be used herein, merely describe points of reference and do not limit the present invention to any particular orientation or configuration.