Abstract:
An improved prosthetic knee joint utilizes a rotary hydraulic chamber with internal flow control and positioned with hydraulic chamber opposite the upper joint section. A polycentric knee joint is provided with a forward flexion bumper and a cable extension assist for improved gait performance.

Description:
FIELD OF THE INVENTION 
   The present invention relates to prosthetic knees, in particularly to improved prosthetic knee designs that may advantageously utilize a rotary hydraulic chamber for damping and to adjust the ease of flexion and extension of the knee. 
   BACKGROUND OF THE INVENTION 
   Prosthetic knees are generally designed to allow above-the-knee amputees to replicate the biomechanical movements of a human knee joint and to permit an appropriate level of activity and stability to the wearer. In biomechanical terms, the human body is generally divided by sagittal and coronal planes. The sagittal plane is a vertical plane running from front to back, dividing the body into left and right sides. The coronal plane, or frontal plane, is a vertical plane running from side to side at right angles to the sagittal plane and therefore divides the body into front and back. Prosthetic knees offer no special function in the coronal plane and, thus, the discussion of relevant gait biomechanics occurs in the sagittal plane. 
   The gait cycle includes both stance and swing phases, each of which may be further subdivided into initial, intermediate and final phases. The stance phase begins with initial contact of the forward limb or “heel strike,” with the hip flexed and knee extended. Loading begins to occur as the body carries forward and includes elements of shock absorption, weight bearing stability, and preservation of forward motion. The body progresses forward to mid-stance and then over the ankle and the limb lags behind the body with the heal rising and preferably the knee flexing slightly in preparation for swing phase. In swing phase, increasing the hip and knee flexion advances the limb and in mid-swing the knee will move into extension. In biomechanical terms, flexion usually indicates decrease in the angle between body segments, or in this case bending at the hip and knee, while extension indicates an increase in the angle. The swing phase ends when the limb again touches the floor. 
   Historically, prosthetic knees evolved with the creation of constant friction or single axis prosthesis consisting of a simple axle connecting shank segments. Modern versions will usually have an adjustable friction cell and spring loaded extension assist to improve swing phase function. 
   Subsequently, stance control prostheses were developed utilizing weight-activated braking mechanisms to add resistance to bending or flexion during stance only. A brake might consist of a spring-loaded brake bushing that binds when loaded during stance phase but is released during swing phase. 
   More complex polycentric prosthetic knees then evolved, most having four pivot points and often referred to as “four bar linkage” devices, with multiple centers of rotation. The positioning of the polycentric rotations with respect to the ground reaction line and the joint line determines the stability of the device during stance and the amount of voluntary control the amputee has over the prosthesis. 
   Fluid control devices comprise another principal category of prosthetic knees and utilize liquid or gas-filled cylinders and pistons to provide hydraulic or pneumatic cadence control. Generally, a piston moves axially from one end of the cylinder towards the other and is aligned in the sagittal plane. Many of the more recent prosthesis designs are hybrids which combine some of the properties of two or more of the principal categories of prostheses. The most modern and costly designs will even incorporate microprocessors to control and modify the characteristics of the prosthesis during gait and changing gait conditions. 
   Numerous difficulties exist in designing an effective knee prosthesis. For example, the use of liquid or gas-filled chambers may affect the ability to locate the centers of polycentric rotation in a polycentric knee; and prosthetic knees may develop very high operating temperatures due to the number of repetitions involved in ambulation and the necessarily small components and confined spaces available within the prosthesis. Furthermore, it is desirable to provide a polycentric knee with some flexion action in stance phase and to provide the extension assist mechanisms to improve gait function in the final portion of the swing phase. Thus, the development of more reliable prosthetic joints that comfortably allow the wearer increased activity and stability remains an objective of prosthetic design. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the invention to provide an improved rotary hydraulic chamber apparatus useful for fluid control in a polycentric or other knee prosthesis. It is further an object of the invention to provide improved polycentric knee prostheses that allow flexing action of the knee joint in stance phase and provide extension assist in swing phase. 
   According to the invention, an improved hydraulic chamber apparatus is provided with valving contained in a rotatable shaft connected to a paddle in the hydraulic chamber where the paddle rotates relative to the chamber as the knee proceeds through phases of flexion and extension. The rotary hydraulic chamber apparatus is designed to dissipate heat and minimize the height of the chamber to facilitate location of the top of the prosthesis close to the joint line. When utilized in a polycentric knee, a polyurethane bumper may be employed to permit slight flexion of the knee, while being restrained by compression against the bumper. A cable operated extension assist may also be provided. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view of the components of an improved hydraulic chamber apparatus for prosthetic knee according to the present invention. 
       FIG. 2A  is a side plan view of an improved paddle assembly according to the present invention. 
       FIG. 2B  is a front plan view of the improved paddle assembly. 
       FIG. 2C  is a front sectional view of the improved paddle assembly taken along line A—A at  FIG. 2A . 
       FIG. 3A  is a side plan view of an improved polycentric knee according to the invention. 
       FIG. 3B  is a front plan view of the improved polycentric knee of  FIG. 3A . 
       FIG. 3C  is a sectional side view of the improved polycentric knee taken along line A—A of  FIG. 3B . 
       FIG. 3D  is a sectional top plan view of the improved polycentric knee taken along line B—B of  FIG. 3C . 
       FIG. 3E  is a perspective view of the improved polycentric knee of  FIG. 3A . 
       FIG. 3F  is an exploded perspective view of the improved polycentric knee of  FIG. 3A . 
       FIG. 4A  is a side plan view of a prosthetic knee according to the invention at full extension. 
       FIG. 4B  is a side sectional view of a prosthetic knee according to the invention at full extension. 
       FIG. 5A  is a side view of the polycentric knee of  FIG. 4A  at 15° stance flexion. 
       FIG. 5B  is a side sectional view of the polycentric knee of  FIG. 5A  at 15° stance flexion. 
       FIG. 5C  is a side sectional view of a portion of the polycentric knee of  FIG. 5A  showing a bumper. 
       FIG. 6A  is a side view of the polycentric knee of  FIG. 4A  at full extension in mid-stance. 
       FIG. 6B  is a side sectional view of the polycentric knee of  FIG. 6A  at full extension in mid-stance. 
       FIG. 7A  is a side view of the polycentric knee of  FIG. 4A  at 45° flexion. 
       FIG. 7B  is a side sectional view of the polycentric knee of  FIG. 7A  at 45° flexion. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Turning first to  FIG. 1 , an exploded view of rotary hydraulic chamber assembly  10  which supports paddle assembly  40  is shown. Of principal importance are left and right hydraulic housings  11 ,  12 , which when joined together and sealed with O-ring  26 , define chamber  85 . Rotary chamber  85  is generally in the shape of an arc of a cylinder to cooperate with rotary movement of paddle assembly  40 . Paddle assembly  40  is mounted within chamber  85  which is filled with fluid, preferably silicone oil. In operation, front links  56  and  57  are mounted about left and right shaft ends  44 ,  45  respectively of rotatable shaft  43 , and in operation rotary motion of the front links causes paddle  41  to move through fluid in chamber  85  as described below. Paddle  41  has the same general shape as the interior of chamber  85 , so that the paddle  41  interfits closely with the chamber. Left and right hydraulic housings  11 ,  12  are shown with first apertures  17 ,  18 , second apertures  19 ,  20 , and third apertures  21 ,  22 , each of which receive locking means such as screws  27 ,  28  and  29  to securely form the chamber  85 . The upper portion of housings  11 ,  12  form the upper joining section and as illustrated comprise top surfaces  13 ,  14  respectively, which define below them grooves  15 ,  16 , and when joined together form the base of a dovetail joint to which an upper residual limb socket may be secured. The upper leg prosthesis may be a residual limb socket, a residual limb socket with adaptor, an attachment to the wearer&#39;s skeletal structure or other prosthesis. Housings  11 ,  12  also have central opening  25  in which the shaft ends  44 ,  45  are received. Mounted on the shaft ends are radial seals  53  and needle bearings  54  to permit rotation of the shaft  43  with respect to the housings  11 ,  12 . Upper apertures  58 ,  59  of front links  56 ,  57  are then received on ends  44 ,  45  of shaft  43 . Lower apertures  62 ,  63  of front links  56 ,  57  communicate with the joint chassis  72 , shown in  FIG. 3F . Also shown is rear link  30  which is mounted between rear wings of housings  11 ,  12  and supported on pivot pin  32 , which is received through apertures  23 ,  24  of the rear wings and upper aperture  31  of rear link. Washers  33  facilitate rotation of link  30  with respect to the housing wings, and needle bearings  34  facilitate rotation of pivot pin  32 . 
   Paddle assembly  40  comprises paddle  41  which may have an opening  42  to receive rotatable shaft  43  or may be integrally formed with the shaft. Assembly  40  also includes plugs  46 ,  47 , back valves such as check balls  48 ,  49 , O-ring seals  50 , and left and right flow control valves such as chokes  51 ,  52 . With reference to  FIG. 2A , it may be seen that chokes  51 ,  52  are received within the ends of the rotatable shaft  43  and that paddle portion  41  has a front side  64  and rear side  65 . The paddle portion  41  preferably rotates through an arc centered on the axis of rotatable shaft  43  and generally opposite the upper portions of housings  11 ,  12 . In this fashion, the hydraulic chamber  85  is located substantially below the rotatable shaft  43  which defines the axis of rotation for the paddle portion  41 , and chamber  85  adds no additional height to the upper portion of the housings. This permits the upper joining section to be located only a short distance from the center of rotation of rotatable shaft  43 . In a prosthetic joint for use by a lower limb amputee having a body weight of 100 kg/220 pounds, the distance from the top of the joining section to the center of rotatable shaft  43  would be only about 2.2 to 2.5 centimeters. 
   With reference to  FIG. 2B , front side  64  is shown with aperture  67  into which hydraulic fluid on the forward side may enter into the paddle  41 , and aperture  66  which permits hydraulic fluid from the rear side of paddle  41  to exit into the forward side of chamber  85 . It will be understood that the opposite side  65  of paddle  41  has similar apertures to permit the flow of hydraulic fluid in the opposite directions. 
     FIG. 2C  better illustrates how hydraulic fluid may flow through paddle  41 . Specifically, when paddle  41  is moving forward through hydraulic chamber  85  toward the forward end of the chamber, as might be the case when the polycentric knee is moving from a state of 45° rear flexion toward full extension, the hydraulic fluid in the forward portion of chamber  85  may enter aperture  67  of forward surface  64  of paddle  41  and proceed through channel  68  and out an opening on the reverse side of paddle  41 . Adjusting left flow control valve  51  correspondingly adjusts the rate at which hydraulic fluid may flow through channel  68  and therefore may be utilized to make the polycentric joint more readily extendable when moving in this direction by allowing increased flow, or correspondingly reducing the extendability of the joint toward extension by decreasing the flow. A back valve such as check ball  48  prevents hydraulic fluid from flowing through channel  68  when paddle  41  is moved in the opposite direction toward the rear of hydraulic chamber  85 . Indeed, when paddle  41  is moving rearward in chamber  85  toward the rearward end of the chamber, hydraulic fluid enters opening  78  on the rear paddle side and proceeds through channel  69  and exits through opening  66  on the front side  64  of paddle  41 . Right flow control valve  52  may be utilized to adjust the rate of flow of hydraulic fluid through channel  69  and thus control the resistance of the polycentric knee toward substantial flexion. 
   Generally, by properly selecting the hydraulic fluid to match the amputee&#39;s activity level, no seals will be required about paddle  41  or the chamber walls by which the paddle passes. Such seals would be subject to heat buildup, and wear or failure. Seals can be utilized if desired, as for instance with a very active user, however, the use of seals will entail additional service to the prosthesis. By utilizing control of fluid flow to adjust the knee&#39;s characteristics, the present design eliminates the play and metallic noises inherent in rack and gear designs for hydraulic damping. 
     FIG. 3A  provides a side view of rotary hydraulic chamber assembly  10  secured by front link  56  and rear link  30  to chassis  72 . Protruding below chassis  72  is spring cup  95  and spring  96  which are used to provide extension assist to the prosthetic knee as described below. Chassis  72  is designed to mount on a lower prosthetic leg assembly (not shown).  FIG. 3E  is a perspective view of the prosthetic knee of  FIG. 3A  in which the top surfaces  13 ,  14  and grooves  15 ,  16  can be more clearly seen as forming a dovetail joint in immediate proximity to the rotary hydraulic chamber contained within hydraulic chamber assembly  10 . In addition, channel  39  which is provided to facilitate cooling and bumper placement is shown on housing  11 .  FIG. 3B  is a front view of the same prosthetic knee with a partial sectional view to show lever  92 .  FIG. 3C  is a sectional view taken along line A—A of  FIG. 3B  and shows how lever  92  communicates between rear link  30  and barrel  74 .  FIG. 3D  is taken along line B—B of  FIG. 3C  and shows a cross section of paddle assembly and bumper  80 . 
     FIGS. 3B and 3E  show the dovetail joint formed by top surfaces  13 ,  14  and grooves  15 ,  16 . In conjunction with channel  94 , the dovetail joint allows an upper leg prosthesis to be mounted directly upon the prosthetic knee. Adjusting screws on the upper leg prosthesis may be used in co-operation with channel  94  to slide the upper leg prosthesis along the dovetail joint, and secure the socket in fixed relation to the prosthetic knee. The upper leg prosthesis is secured in a more forward position for greater stability, and a more rearward position for more responsive flexion action in the knee. This dovetail joint may obviate the need for a separate adapter to join the prosthetic knee to the upper leg prosthesis in an adjustable fashion. 
     FIG. 3F  is an exploded view of the entire prosthetic knee assembly and in particular shows bumpers  80  which are mounted in channels of housings  11 ,  12  and restrained by covers  81 ,  82  which are held in place by screws  89 . Bumpers  80  may be made of different durometer materials to provide different levels of resistance to forward flexion. Bumper covers  81 ,  82  act as hard stops to forward flexion beyond about 10° to 20° of rotation.  FIG. 3F  also shows bladder  71  and bladder plugs  70  which are secured within hydraulic chamber  85  in order to provide slight compressibility of the gas within bladder  71 . By placing a bladder  71  on either side of paddle  41 , a slight compression can be achieved in either direction of paddle movement even without flow of the hydraulic fluid. 
   Lever assembly comprising lever  92 , upper and lower dowels  91 ,  90 , and washers  93 , are also illustrated in  FIG. 3F . Upper dowel  91  proceeds through slots  88  of lower wings of rear link  30  while lower dowel  90  proceeds through aperture  79  on barrel  74 , and lever  92  is held in place between dowels  91  and  92 . Barrel  74  also has catch  87  to receive proximal end of a tensile member such as cable  98  which is secured at its opposite distal end to locknut  99 , and intermediately the tensile member or cable body extends through spring ferule  97 , spring  96 , and spring cup  95  into chassis  72 . Rotation of rear link  30  about its pivot point on rear axle  76  causes upper dowel  91  to move and communicate movement through lever  92  to barrel  74 . As barrel  74  moves counter-clockwise, cable  98  is pulled into the chassis and spring  96  is compressed. Barrel  74  is received within aperture  86  in chassis  72  and secured in place by barrel bearings  73  and fasteners such as button head screws  83 . A fastener such as bolt  84  attaches the chassis  72  to a lower prosthetic limb. 
     FIGS. 4A ,  5 A,  6 A, and  7 A and corresponding sectional views  4 B,  5 B,  6 B, and  7 B show the typical movements of prosthetic knee during the stance phase from initial heel strike to heel lift. In  FIG. 4A , the prosthetic knee is at full extension in typical position for heel strike.  FIG. 5A  represents the prosthetic knee as some load is placed on the prosthetic knee and it can be seen that rear link  30  has rotated about lower rear axle  76  slightly counter-clockwise with respect to chassis  72  exposing slot  88 . In addition, front link  56  has rotated counter-clockwise slightly about shaft  43  until, as shown in  FIG. 5C , pin  60  has made increasingly resistive contact with bumper  80  until the position of bumper cover  81  has halted counter-clockwise movement after about 15° of rotation or forward flexion. Pin  60  is able to move in an arcuate fashion around the axis of shaft  43  in channel  39 . Channel  39  not only permits the motion of pin  60 , but also thins the sidewalls of housings  11 ,  12  and provides additional surface area for heat within the hydraulic chamber to dissipate. 
   As the step progresses to mid-stance as shown in  FIG. 6A , the prosthetic knee is again at full extension. Then, in  FIG. 7A , the limb is lagging behind the body and the prosthetic knee is at approximately 45° rear flexion, and it can be seen that rear link  30  has moved clockwise about rear axle  76  and front link  56  has also moved clockwise about shaft  43 . Clockwise rotation of link  30  on both rear axles  32 ,  76  has, as shown in  FIG. 7B , caused the downward movement of lever  92  with respect to chassis  72  resulting in the counter-clockwise rotation of barrel  74  thereby pulling cable  98  into chassis  72  and compressing spring  95 . The tension in spring  95  will tend to pull the knee back from its rearwardly flexed position into full extension when weight is removed from the limb. Adjustment of both the tension of spring  95  and the flow of hydraulic fluid in chamber  85  from the front of paddle  41  to the rear through channel  68  using flow control valve  51  will vary the speed and force with which the prosthetic knee returns to full extension. 
   Although preferred embodiments of the present invention have been disclosed in detail herein, it will be understood that various substitutions and modifications may be made to the disclosed embodiment described herein without departing from the scope and spirit of the present invention as recited in the appended claims.