Abstract:
A prosthetic insert unit for cushioning shocks in prosthetics is provided. The unit includes attachment member ( 150  etc.), a lower sleeve ( 124 ′ etc), a slide bearing ( 152 ′ etc.) to allow free reciprocal motion therebetween, an elastomeric energy storage member ( 124 ′ etc.) received in the interior of the sleeve ( 124 ′ etc.), a piston ( 134 ′ etc.) cooperative with said elastomer member to compress same, and an anti-rotation mechanism. Preferably, the anti-rotation mechanism is integral with the slide bearing ( 152 ′ etc.). The elastomer member provides controlled deflection as well as damping for the insert. Preferably, an anti-click element ( 269  etc.) is provide to minimize rebound clicking. Acoustical elements ( 268  etc.) may also be included to minimize noise transmission into other areas of the insert.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     This invention is directed to an insert for prosthetics that is connectable between prosthetic parts. More particularly, the present invention is directed to an elastomer linear energy management unit for inclusion in a prosthetic lower limb or the like. 
     When a patient moves with a prosthetic limb, such as during walking or athletic activities, the patient&#39;s stump and or pelvis experiences shock, and this shock may cause pain and further physical deterioration. This is particularly true in patients with recent amputations. Providing a flexible insert within the patient&#39;s prosthetic minimizes such shocks. Examples of prostheses including a flexible element may be found in U.S. Pat. Nos. 4,038,705, 4,883,493, 5,217,500, and 5,458,656, and GB 2 014 855A. 
     One such flexible elastomeric prosthetic including an elastomeric flexible element is described in DE 196 42 719 A1 to D. Kuczka filed Oct. 17, 1996 entitled “Insert for Prosthetic Devices”. Kuczka teaches a prosthetic insert having a prosthetic sleeve ( 2 ) and a lower sleeve ( 10 ) that at least partially projects into the prosthetic sleeve ( 2 ), a bearing ( 11 ) to provide low friction movement between the sleeves ( 2 ,  10 ), a counterbearing ( 9 ), and a longitudinally displaceable elastomer damping element ( 8 ′) positioned at the lower end of and within sleeve ( 2 ). Threaded disc ( 5 ) interconnects to the sleeve ( 2 ) and contacts elastomer element ( 8 ′). Anti-rotation is provided by element ( 15 ) including an external key ( 16 ) formed on the sleeve ( 2 ) and a slotted bolt ( 17 ). 
     The Kuczka device suffers from a number of problems. First, the anti-rotation feature is external to the sleeve, thus it is bulky and unsightly and provides a large lower profile. Further, the elastomer element is subject to buckling because of its long length. Also, since the elastomer element is positioned near the foot adapter, the large upper tube ( 2 ) must extend the distance from the prosthetic part near the knee to the foot adapter, thus providing an unwanted massive and high rotary inertia structure. Moreover, the Kuczka device may click during rebound as stop ( 13 ) hits bearing (II). Therefore there is a need for a low inertia, low profile prosthetic insert which solves the problems associated with the prior art. Additionally, in some applications, rotational compliance of the prosthesis is desirable. 
     The present invention, in one aspect thereof, is directed to prosthetic suspension insert, comprising a lower cylindrical sleeve attachable to a first (lower) prosthetic member; an external attachment member attachable to a second (upper) prosthetic member and surrounding a portion of the cylindrical sleeve; a slide bearing located between an internal peripheral portion of the external attachment member and an external peripheral portion of the cylindrical sleeve, such that the external attachment member may slide freely relative to the cylindrical sleeve; an elastomeric energy storing element positioned within the cylindrical sleeve; a piston cooperative with the external attachment member and slidably positioned within the cylindrical sleeve to engage an axial end portion of the elastomeric energy storage element; and an anti-rotator engaged between the cylindrical sleeve and the external attachment member restraining relative rotation therebetween whereby the elastomeric energy storage element will provide an axial cushioning action to the user during walking. 
     In another aspect, the elastomeric energy storage member is relatively unstable and collapsible is provided with guide means along its length. The guide means engage the internal surface of the sleeve and provide damping of movement between the sleeve and external attachment means. Preferably, the cylindrical sleeve includes an inner diameter of constant dimension along its length, and the elastomeric energy storing member is positioned entirely within the inner diameter. The elastomeric member may include a plurality of individual units, preferably including a central aperture therethrough, and is preferably precompressed by a desired amount. This precompression may be adjustable. 
     In yet another aspect which reduces the profile width of the insert, the anti-rotator feature is formed integral with the slide bearing. In this aspect, the slide bearing preferably includes at least one protrusion which slides in at least one groove formed in the external attachment member. In another aspect, the anti-rotator includes a compliant member to provide limited rotation between the sleeve and the attachment member. Preferably, the compliant member is a annular elastomer member bonded to the cylindrical sleeve and integral with the slide bearing. 
     In another aspect, the insert includes an anti-click element, such as one or more elastomeric washers, to minimize rebound clicking during use. Optionally, or additionally, internal noise transmission may be further retarded by use of an acoustical treatment, such as a open cell foam contained in the insert, to deaden sounds generated by action of the insert. Other features, advantages and characteristics of the present invention will become apparent after a reading of the following detailed description of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following figures depict the preferred embodiments of the present invention, like items bearing like reference numerals and, in which 
     FIG. 1A is a cross-sectional side view of an embodiment of the prosthetic suspension insert in accordance with the present invention; 
     FIG. 1B is an end view of the piston used in the FIG. 1A embodiment; 
     FIG. 1C is a cross sectioned side view of an elastomer element used in the FIG. 1A embodiment; 
     FIG. 2A is a cross sectioned side view of an alternate insert embodiment in accordance with the present invention; 
     FIG. 2B is a perspective view of the slide bearing used in FIG. 2A; 
     FIG. 3A is a cross sectioned side view of another alternate insert embodiment in accordance with the present invention; 
     FIG. 3B is a cross sectioned side view of an alternate slide bearing including a complaint member; and 
     FIG. 3C is a cross sectioned side view of the slide bearing of FIG.  3 B. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As best seen in FIG. 1A, the insert  120 ′ in accordance with the present invention provides resiliency which effectively mimics that provided by the human leg, such that gait symmetry is effectively achieved. In use, the insert  120 ′ will be received in an adapter  162 ′ in a prosthetic foot  164 ′ or the like and is also received in an adapter  163 ′, for example, in a stump cap  165 ′ or the like. Upper and lower ends of unit  120 ′ are received in, for example, 31 mm adapters manufactured by Hosmer US identified by part No. 39504 or 30 mm adapters manufactured by Otto Bock identified as part no. 2R38 or 4R52. However, it will be understood that the specified adapter is regarded as merely exemplary and that the unit  120 ′ of the present invention could be configured to operate with other adapters, as well. Notably, the need for an upper adapter will be eliminated in the later embodiments. Moreover, it should be understood that the insert in accordance with the present invention finds applicability in lower leg prosthetics. However, the insert may also be applied to prosthetics for above-the-knee amputees where a mechanical knee joint is implemented. 
     A lower aluminum cylindrical sleeve  124 ′ extends a major portion of a distance between the prosthetic foot  164 ′ and the cap  165 ′. The sleeve  124 ′ is stopped by an internal plug  125 ′. The sleeve  124 ′ is crimped at  128 ′ to secure the plug  125 ′ in the desired position. Sleeve  124 ′ is provided with an external reinforcement ring  129 ′ in those applications where sleeve  124 ′ is a structural member. In this embodiment, the elastomeric energy storage means, i.e., the elastomer member  122 ′ is made up of a plurality of generally cylindrical units  123 ′ as shown in FIG.  1 C. Each cylindrical unit  123 ′ has a radially extending flange  121 ′ and a aperture  126 ′ therethrough. The addition of bore  126 ′ through each elastomer element  123 ′ provides the desired spring rate by allowing the appropriate bulge characteristics for the leg prosthesis application. The plurality of flanges  121 ′ fit snugly in sleeve  124 ′ and serving as guide means to prevent buckling of the elastomer column. This elastomeric member  122 ′ is inherently unstable because of its high length L to diameter D ratio. Generally, it is known to persons of skill in the art that L/D ratios of greater than two tend to be unstable. 
     The close fitting sleeve  124 ′ engages flanges  121 ′ and provides means to stabilize the collapse of the elastomer when engaged by the piston  134 ′ during compression. The collapse of elastomeric member  122 ′ into contact with the inner surface of sleeve  124 ′ will produce damping to restrain relative motion between the sleeve  124 ′ and elastomer means  122 ′. The elastomeric means  122 ′ is preferably made of natural rubber, although other materials such as urethane and Hytrel plastics may be used, as well. The durometer of the material in the elastomeric means  122 ′ preferably falls in the range of between 50 and 80 Shore A. Preferably, the radially outermost surface of guide means  121 ′ will be provided with a lubricant, such as a Teflon-filled grease, to reduce wear. Alternatively, other suitable lubricating mechanisms may be provided. 
     The opposite (upper) end of sleeve  124 ′ is closed by a cylindrical collar  130 ′ which slidingly receives piston rod  134 ′. The piston head  146 ′ on piston  134 ′ engages the upper axial end of elastomeric means  122 ′. The majority of the length of piston rod  134 ′ has a square configuration (FIG. 1B) which is received in a like shaped opening  135 ′ in cylindrical collar  130 ′ to prevent relative rotation. This provides a compact anti-rotation (anti-rotator) feature. 
     A external attachment member  150 ′ which includes a lower generally cylindrical sleeve portion is received over the upper end of sleeve  124 ′. A slide bearing  152 ′ of low friction material is received by and adhered to the internal periphery of attachment means  150 ′ to facilitate axial movement of attachment member  150 ′ relative to sleeve  124 ′. An axial bore  141 ′ formed through piston  134 ′ is threaded and receives a fastener  154 ′. This fastener  154 ′ secures attachment member  150 ′ to piston rod  134 ′. Likewise, a cylindrical portion  137 ′ of piston rod  134 ′ is received in a similarly-shaped recess  155 ′ in attachment member  150 ′. Piston  134 ′ will move concurrently with external attachment member  150 ′ to collapse elastomeric means  122 ′. The square shaft in square opening  135 ′ prevents relative rotation between sleeve  124 ′ and attachment member  150 ′. 
     For appropriate applications, plug  125 ′ can have a bore  157 ′ that is threaded to receive an adjustment bolt  158 ′. Bolt  158 ′ bears against washer  160 ′ and by adjusting its position relative to plug  125 ′, the amount of precompression of elastomeric member  122 ′ can be varied. The amount of preload provided can be adjusted by controlling the length of elastomeric means  122 ′. It will typically be desired to provide a preload equal to between 10% and 20% of the normal load applied to the elastomeric means  122 ′. The ultimate load will compress the elastomer up to 40% of its uncollapsed length. 
     FIG. 2A illustrates another embodiment of the insert  220  including an aluminum external attachment member  250  having an integral adapter for securing to the prosthetic stump or cap (not shown) or the like, and an aluminum lower sleeve  224  which secures to a prosthetic foot, adapter, or the like (not shown). For clarity, a large portion of the lower sleeve  224  which extends the majority of the distance between the prosthetic foot and stump cap is not shown. The stump or cap member may be attached to the attachment member  250  by inserting a square-shaped post (ex. a Hosmer 29406) thereon into square-shaped pocket  247  and securing thereto via threaded set screws (not shown) received in threaded holes  256 . An elastomer energy storage element  222  is received within the inner dimension (diameter) of the sleeve  224 . Preferably elastomer element  222  comprises a plurality of individual elements  223  as is shown in FIG.  1 C. 
     In this embodiment, the anti-rotation mechanism (anti-rotator) is integrated into the slide bearing  252 . The external attachment member  250  includes at least one, and preferably a plurality of grooves  251  formed along its length for receiving at least one, and preferably a plurality of protrusions  253  formed on the periphery of the Nylatron slide bearing  252  (FIG.  2 B). Preferably two radially opposed protrusions  253  are provided. The internal diametral surface  259  of slide bearing  252  is bonded to the outer diameter of sleeve  224  with suitable adhesive, such as an epoxy or cyanoacrylate. The protrusions  253  cooperate with the grooves  251  to restrain rotation, but allow relative axial displacements. 
     A nylon stop plug  225  is adhesively bonded via an epoxy or a cyanoacrylate adhesive to the inside surface  261  of the lower sleeve  224 . The stop plug  225  includes a hole  267  therethrough which includes a open cell foam plug  268  therein. The foam plug  268  functions as an acoustical barrier to prevent noise made via compression of the elastomer member  222  from transmitted to other portions of the insert, and in particular from resonating inside the lower chamber-like portion of sleeve  224 . Optionally, the acoustical barrier may be placed inside the lower end of sleeve  224  itself. The puck-shaped nylon piston  234  cooperates and moves in conjunction with the attachment member  250  and is slidably received in close fit relation to the inner dimension  261  of sleeve  224 . The piston  234  engages an axial end of the elastomer member  222  to compress same in use. The lower assembly comprising sleeve  224  with slide bearing  252  and plug  225  adhered thereto is assembled with the elastomer member  222  and piston  234  and inserted into the attachment member  250 . 
     An anti-click elastomer washer  269  or o-ring is inserted adjacent to the lower end of the slide bearing  252 . A rigid steel seat washer  270  is then inserted over elastomer washer  269  and the assembly  220  is precompressed in the axial direction, such that a retaining c-clip  271  may be installed. The c-clip  271  holds the insert assembly  220  together. The position of the clip  271  and thickness of the washer  270  (such as by adding additional washers) may be adjusted to vary the precompression on the elastomer member  222 . Alternatively, spacers (not shown) may be added at the interface of the piston  234  and elastomer member or at the lower end of the elastomer member  222 . During walking, the washer  269  eliminates clicking as the elastomer element  222  rebounds after the compression stroke. It should be noted that the slide bearing  252  pulls away from the seat washer  270  during compression. It should also he recognized that by having the elastomer element  222  installed entirely within the confines of the sleeve  224 , the diameter of the lower sleeve  224  can be made smaller, thereby providing lower profile. Moreover, the highest mass portion of the insert is located close to the knee, thus, advantageously providing a low rotary inertia. Further, the anti-rotation feature is preferably made integral to the slide bearing providing a streamlined appearance. 
     FIG. 3A illustrates another embodiment of the prosthetic suspension insert  320  in accordance with the present invention which includes a central fastener assembly  372  for providing precompression to the elastomer energy storage element  322 . Compliant elastomer washers  369  are provided at the lower end of fastener assembly  372  to prevent rebound clicking. Likewise, a compliant annular puck  369 ′ is preferably provided at the top of assembly  372  to prevent rattling of the fastener assembly  372  within the attachment member  350  when under enough load to alleviate the precompression. Fasteners  373 ,  373 ′ are turned to adjust the amount of precompression, whilst fastener  373 ″ secures the assembly to the attachment member  250 . Nylon piston  334  is slidably received in the lower sleeve  324  as in the previous embodiments. Similarly, the Nylatron slide bearing  352 , the same as shown in FIG. 2B, is bonded to the outer peripheral surface of the sleeve  324  and the plug  325  is bonded to the internal surface of the sleeve  324 . A plug of open cell foam  368  is provided as an acoustical barrier to prevent transmission of noise into the lower cavity  377  of sleeve  324  which could function as a resonant chamber. 
     FIG. 3B and 3C illustrate an alternate embodiment of the slide bearing  352 ′ which may be interchanged with the slide bearing of FIG. 2A or  3 A. This slide bearing  352 ′ includes rotational compliance provided by a thin elastomer layer  374  which is bonded to the outer Nylatron bearing portion  375 . The elastomer layer  374  is then preferably hot PV bonded to the outer diameter of the sleeve  324 . By way of example, and not to be considered limiting, the elastomer layer  374  is comprised of a 0.04 inch (1 mm) thick annulus and manufactured from natural rubber of a hardness of between 44 and 52 Shore A durometer. However, any other suitable elastomer or bonding method may be used. The elastomer layer  374  may include a washer-like portion  369 ″ formed at the lower end of the bearing portion  375  to provide the anti-click feature, if needed, such as for example, when installed in the FIG. 2A embodiment. This slide bearing  352 ′ provides a rotational compliance to the suspension insert. For example, under normal expected operating loads, about +/−5° of torsional motion is accommodated within the insert. 
     Various changes, alternatives and modifications will become apparent to one of ordinary skill in the art following a reading of the foregoing specification. It is intended that all such changes, alternatives and modifications as fall within the scope of the appended claims be considered part of the present invention.