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'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'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.