Releasable attachment system for a prosthetic limb

Abstract

A releasable attachment system is provided for use with a bone anchored post and related external prosthesis such as a prosthetic limb or the like, wherein the attachment system includes a safety release mechanism designed to release or break away when encountering an excess mechanical load. The bone anchored mounting post is implanted for direct affixation to patient bone, and carries or is connected to a fixator structure protruding through soft skin tissue and the like at the end or stump of an amputated limb for mechanical connection to the external prosthesis. The safety release mechanism accommodates substantially normal patient movement throughout a corresponding range of substantially normal mechanical loads, but releases in the presence of an excess load to prevent undesirable fracture failures.

1 . A releasable attachment system for coupling an exoskeletal prosthesis to a patient limb having a bone anchored mounting post with an external fixator structure, the releasable attachment system comprising:
 a first component releasably coupled to the fixator structure, the first component including
 a rigid base plate, 
 an upstanding rigid peripheral wall surrounding the base plate, 
 a plurality of spring-loaded jaw elements pivotally mounted to the peripheral wall and defining a pocket for a clamped, snap-fit reception of the fixator structure, and 
 a sawtooth array protruding downwardly from an underside of the base plate and providing a plurality of detent seats; 
 a tension member having a first end and a second end, the first end connected to the rigid base plate of the first component; and 
   a second component connected to the second end of the tension member and to the prosthesis, the second component including
 a plurality of radially projecting detent pins configured for engagement with the detent seats of the sawtooth array. 
   
     
     
         2 . The releasable attachment system of  claim 1 , wherein the plurality of spring-loaded jaw elements pivotally mounted to the peripheral wall in a radially inwardly projecting orientation, the spring-loaded jaw elements adapted to accommodate relative movement between the fixator structure and the first component when a force overload condition occurs. 
     
     
         3 . The releasable attachment system of  claim 1 , wherein the tension member is adapted to bias the radially projecting detent pins for engagement with the detent seats of the sawtooth array, the tension member further adapted to accommodate relative movement between the first component and the second component when a force overload condition occurs. 
     
     
         4 . The releasable attachment system of  claim 1 , wherein the second component is configured to pivot with respect to the first component in response to a bending force overload condition. 
     
     
         5 . The releasable attachment system of  claim 4 , wherein the tension member elongates to accommodate angular displacement between the second component and the first component. 
     
     
         6 . The releasable attachment system of  claim 1 , wherein the first component is configured to completely release from the fixator structure when the jaw elements pivot upwardly in response to a bending force overload condition. 
     
     
         7 . The releasable attachment system of  claim 1 , wherein the first component is configured to completely release from the fixator structure when the retention force of the jaw elements is exceeded in response to a tension force overload condition. 
     
     
         8 . The releasable attachment system of  claim 1 , wherein the second component is configured to rotate relative to the first component in response to a torsion force overload condition. 
     
     
         9 . The releasable attachment system of  claim 8 , wherein the tension member is adapted to elongate sufficiently to accommodate the relative rotation. 
     
     
         10 . The releasable attachment system of  claim 1 , wherein the second component is configured to rotate relative to the sawtooth array in response to a torsion force overload condition. 
     
     
         11 . The releasable attachment system of  claim 10 , wherein the detent pins ride downwardly within the respective detent seats defined by the sawtooth array in response to a torsion force overload condition. 
     
     
         12 . The releasable attachment system of  claim 1 , wherein the sawtooth array cooperates with the detent pins and the tension member to provide a spring-loaded torsion clutch that accommodates relative rotation in either direction in response to a torsion force overload condition. 
     
     
         13 . A releasable attachment system for coupling an exoskeletal prosthesis to a patient limb having a bone anchored mounting post with an external fixator structure, said releasable attachment system comprising:
 a first component releasably coupled to the fixator structure, the first component including a base plate having a sawtooth array defining a plurality of detent seats;   a second component configured for attachment to the prosthesis, the second component including,
 a link; and 
 a plurality of detent pins; 
   wherein the first component is coupled to the second component by the link such that in a normal position, the link draws the plurality of detent pins upwardly for secure and substantially rigid engagement with the detent seats.   
     
     
         14 . The releasable attachment system of  claim 13 , wherein the first component further comprises a plurality of jaw elements that are pivotally mounted to a peripheral wall and are biased into a radially inward projecting orientation. 
     
     
         15 . The releasable attachment system of  claim 14 , wherein the jaw elements pivot upwards relative to the peripheral wall in response to an overload force thereby allowing limited movement of the fixator structure relative to the first component. 
     
     
         16 . The releasable attachment system of  claim 13 , wherein the second component is configured to pivot with respect to the first component in response to a bending force overload condition. 
     
     
         17 . The releasable attachment system of  claim 16 , wherein the link elongates to accommodate angular displacement between the second component and the first component. 
     
     
         18 . The releasable attachment system of  claim 13 , wherein the first component is configured to completely release from the fixator structure when the jaw elements pivot upwardly in response to a bending force overload condition. 
     
     
         19 . The releasable attachment system of  claim 13 , wherein the first component is configured to completely release from the fixator structure when the retention force of the jaw elements is exceeded in response to a tension force overload condition. 
     
     
         20 . The releasable attachment system of  claim 13 , wherein the second component is configured to rotate relative to the first component in response to a torsion force overload condition. 
     
     
         21 . A releasable attachment system for coupling an exoskeletal prosthesis to a patient limb having a bone anchored mounting post with an external fixator structure, said releasable attachment system comprising:
 a first component adapted for connection to the fixator structure;   a second component adapted for connection to the prosthesis; and   a safety release mechanism normally retaining the prosthesis in a rigid substantially motion-free interconnected relation to the fixator structure, said safety release mechanism responding to a force overload condition to permit relative movement between the prosthesis and the fixator structure;   wherein said first component comprises a socket member including at least one spring-loaded jaw element for releasably engaging the fixator structure in response to a bending and/or tensile force overload condition, and wherein said safety release mechanism comprises a torsion clutch coupled between said socket member and the prosthesis.   
     
     
         22 . The releasable attachment system of  claim 21  wherein said torsion clutch comprises a base plate carried by said socket member, a base link comprising said second component, a tension member coupled between said base plate and said base link, and cooperatively engageable detent means carried by said base plate and said base link. 
     
     
         23 . The releasable attachment system of  claim 22  wherein said cooperatively engageable detent means comprises a plurality of radially outwardly extending detent pins on one of said base plate and said base link, and a plurality of radially open detent seats defined by the other of said base plate and said base link.