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Releasable attachment system for a prosthetic limb

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Releasable attachment system for a prosthetic limb


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.

Browse recent University Of Utah Research Foundation patents - Salt Lake City, UT, US
Inventors: Kent N. Bachus, Jeremy D. Borchert
USPTO Applicaton #: #20120316657 - Class: 623 32 (USPTO) - 12/13/12 - Class 623 
Prosthesis (i.e., Artificial Body Members), Parts Thereof, Or Aids And Accessories Therefor > Leg >Suspender Or Attachment From Natural Leg



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The Patent Description & Claims data below is from USPTO Patent Application 20120316657, Releasable attachment system for a prosthetic limb.

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CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 11/995,875, filed on Jul. 23, 2008, which is a 35 U.S.C. §371 application of PCT international application no. PCT/US2006/026837, filed on Jul. 12, 2006, which claims the benefit of, and priority to, U.S. Provisional Patent Application No. 60/701,189, filed on Jul. 20, 2005 and U.S. Provisional Patent Application No. 60/767,440, filed on Mar. 28, 2006, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates generally to improvements in external or exoskeletal prosthetic devices and systems of the type utilizing an implanted, bone anchored mounting post having or carrying an externally protruding or externally exposed fixator structure for removable attachment to a prosthesis such as a prosthetic limb or the like. More particularly, this invention relates to an improved attachment system for coupling the external fixator structure to the prosthesis, wherein the attachment system includes a safety release mechanism adapted to release in response to an excess mechanical load applied to the prosthesis.

Socket type prosthetic limbs such as prosthetic arm and leg structures for use by amputees are generally well known in the art, wherein a prosthesis is constructed with an open-ended and typically padded socket structure for receiving and supporting the post-surgical stump of an amputated limb. By way of example, a socket type prosthetic leg includes such open-ended socket structure at an upper end thereof for receiving and supporting the post-surgical upper leg of a transfemoral amputee. Various straps and/or other fasteners are provided for securing the prosthetic leg to the amputated limb to accommodate walking mobility at least on a limited basis. Such prosthetic limbs can be an important factor in both physical and mental rehabilitation of an amputee.

However, socket type prosthetic limbs are associated with a number of recognized limitations and disadvantages. In particular, the socket style prosthesis inherently couples mechanical loads associated with normal ambulatory activity through a soft tissue interface defined by the soft tissue covering the end or stump of the amputated limb, but wherein this soft tissue interface is structurally unsuited for this purpose. While many different arrangements and configurations for the requisite straps and other fasteners have been proposed for improved transmission and distribution of these mechanical loads to bone structures to achieve an improved secure and stable prosthesis attachment, to correspondingly accommodate a more natural ambulatory movement, such arrangements have achieved only limited success. In addition, compressive loading of the soft stump tissue interface often results in blisters, sores, chafing and other undesirable skin irritation problems which have been addressed primarily by adding soft padding material within the socket structure. But such soft padding material undesirably increases the extent of the soft or non-rigid interface between the amputated limb and prosthesis, all in a manner that is incompatible with an optimally secure and stable prosthesis connection. As a result, particularly in the case of a prosthetic leg, traditional socket style connection structures and methods have generally failed to accommodate a normal walking motion.

In recent years, improved external or exoskeletal prosthetic devices have been proposed, wherein the external prosthesis is structurally linked by means of a bone anchored mounting system directly to patient bone. In such devices, a rigid mounting post is surgically implanted and attached securely to patient bone as by means of osseointegration or the like. This implanted bone anchored mounting post extends from the bone attachment site and includes or is attached to a fixator pin or post structure that protrudes through the overlying soft stump tissue at the end of the amputated limb. Thus, one end of the fixator structure is externally exposed for secure and direct mechanical attachment to a prosthetic limb or the like by means of a rigid linkage.

In such bone anchored mounting systems, mechanical loads on the prosthetic limb during ambulation are thus transmitted by the rigid linkage and through the external fixator structure and implanted mounting post directly to patient bone. As a result, conventional and undesirable mechanical loading of the soft tissue interface is avoided, and substantially improved and/or substantially normal patient movements are accommodated. In addition, the requirement for compressive loading of the soft tissue at the end of the amputated limb is significantly reduced, to correspondingly reduce incidence of blisters and other associated skin irritation problems. Moreover, by mechanically linking and supporting the prosthesis directly from patient bone, amputees have reported a significant increase in perception of the prosthesis as an actual and natural body part—a highly desirable factor referred to as “osseoperception”.

Although use of a bone anchored mounting system offers potentially dramatic improvements in secure and stable prosthetic limb attachment, and corresponding improvements in amputee lifestyle, major complications can arise when the prosthetic structure encounters a mechanical load that exceeds normal design parameters. More particularly, in the event of a tensile, bending, or torsion load exceeding structural design limitations, fracture-failure can occur. Breakage of prosthesis structures such as the implanted bone anchored mounting post often requires repair by surgery. Breakage of the patient bone at or near the interface with the implanted mounting post also requires surgical repair, and reseating or replacement of the implanted mounting post may not be possible. Both of these failure modes represent traumatic and highly undesirable complications.

There exists, therefore, a significant need for further improvements in and to external or exoskeletal prosthetic devices of the type utilizing a bone anchored mounting post, wherein an improved attachment system couples the prosthetic device to an externally protruding fixator structure in a manner accommodating substantially normal patient movement and a corresponding range of normal mechanical loads, but wherein the improved attachment system includes a safety release mechanism adapted to release in response to an excess mechanical load thereby preventing undesirable fracture failures. The present invention fulfills these needs and provides further related advantages.

SUMMARY

OF THE INVENTION

In accordance with the invention, an improved releasable attachment system is provided for use in combination with a bone anchored post and related external prosthesis such as a prosthetic limb or the like adapted for connection thereto. The bone anchored mounting post comprises an implant component adapted for secure and stable affixation to patient bone. This bone anchored mounting post carries or is connected to a fixator structure such as an elongated pin which protrudes through soft skin tissue and the like covering the end or stump of an amputated limb, and is adapted for secure and stable attachment to the external or exoskeletal prosthesis. The improved attachment system incorporates a safety release mechanism designed to accommodate substantially normal patient movement and a corresponding range of substantially normal mechanical loads. However, in the event of an excess mechanical load applied to the prosthetic structures and/or to the implant interface of the mounting post with patient bone, the safety release mechanism is designed to release or break away thereby preventing undesirable fracture failure modes. The safety release mechanism is designed for response to excessive bending, tensile, and/or torsion loads.

In a preferred form, the releasable attachment system is interposed between the prosthesis and the fixator structure, and is adapted for mechanical connection with a radially enlarged mounting flange on the fixator structure. The safety release mechanism includes an upper socket member lined by a plurality of spring-loaded jaw elements for releasable clamp-on, substantially snap-fit engagement with the fixator structure mounting flange. The socket member is coupled by a resilient tension band to a lower release clutch including a plurality of downwardly presented, radially open detent seats having a sawtooth geometry or the like for respectively receiving a plurality of radially projecting detent pins. The tension band normally draws and retains the detent pins securely within the detent seats.

Upon encountering a bending force exceeding a predetermined limit, the tension band accommodates relative movement between the upper socket member and the lower release clutch, while the spring-loaded jaw elements accommodate relative movement between the socket member and the fixator structure mounting flange. When the bending force exceeds a predetermined limit, the jaw elements will accommodate separation of the socket member from the fixator structure. Similarly, upon encountering a tensile force load exceeding a predetermined limit, the tensile band will elongate and/or the spring-loaded jaw elements will displace to accommodate similar relative motions between components of the attachment system. Upon encountering a torsion force load exceeding a predetermined limit, the tensile band will elongate sufficiently to accommodate relative rotational displacement between the detent pins and the detent seats.

In an alternative preferred form of the invention, the attachment system or unit comprises a bending force clutch for adjustably responding to a bending force overload condition, and a torsion force clutch for adjustably responding to a torsion force overload condition. The bending force clutch comprises a relatively large ball-shaped member having a peripheral groove for normally seated reception of an array of spring-loaded clutch balls. This ball member is coupled by means of a universal joint linkage with the torsion force clutch comprising a torque cartridge including spring-loaded detent balls carried within a generally cup-shaped unit housing. The ball member and the unit housing are adapted for connection between the bone anchored fixator structure and the prosthesis. The ball member is designed for angular movement relative to the housing in response to a bending force overload condition, whereas the torque cartridge is designed for rotational movement relative to the housing in response to a torsion force overload condition.

Other features and advantages of the present invention will become apparent from the following more detailed description, taken in connection with the accompanying drawing which illustrate, by way of example, the principals of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate the invention. In such drawings:

FIG. 1 is a somewhat schematic diagram showing the releasable attachment system of the present invention in combination with a bone anchored prosthesis mounting post for use in releasable external attachment to an exoskeletal prosthesis;

FIG. 2 is a somewhat schematic diagram illustrating an amputated upper leg portion of a transfemoral amputee, prior to implanted installation of a bone anchored mounting post;

FIG. 3 is a somewhat schematic diagram similar to FIG. 2, but showing the amputated upper leg portion following implantation of the bone anchored mounting post;

FIG. 4 is a fragmented perspective view showing the lower or stump end of the amputated upper leg portion, and illustrating a fixator structure protruding externally from the amputated limb;

FIG. 5 is a somewhat schematic diagram similar to FIG. 1, but depicting initial release and displacement of the attachment system in response to a bending force overload condition;

FIGS. 6 through 8 are diagrams similar to FIG. 5, and showing successively further release and displacement of the attachment system in response to a bending force overload condition;

FIG. 9 is another schematic diagram similar to FIGS. 1 and 5-8, illustrating initial release and displacement of the attachment system in response to a tensile force overload condition;

FIG. 10 is a somewhat schematic diagram similar to FIGS. 1 and 5-9, and showing initial release and displacement of the attachment system in response to a torsion force overload condition;

FIG. 11 is a perspective view showing the top, front and left sides of a releasable attachment unit constructed in accordance with one alternative preferred form of the invention;

FIG. 12 is a front elevation view of the releasable attachment unit of FIG. 11;

FIG. 13 is a left side elevation view of the releasable attachment unit of FIG. 11;

FIG. 14 is an exploded top perspective view of the releasable attachment unit of FIG. 11;

FIG. 15 is an exploded bottom perspective view of the releasable attachment unit of FIG. 11;

FIG. 16 is an exploded front view of the releasable attachment unit of FIG. 11;

FIG. 17 is an exploded saggital or medial-lateral sectional view of the releasable attachment unit shown in FIG. 16;

FIG. 18 is an enlarged top plan view of a cup-shaped housing forming a portion of the releasable attachment unit, taken generally on the line 18-18 of FIG. 17;

FIG. 19 is an exploded left side elevation view of the releasable attachment unit of FIG. 11;

FIG. 20 is an exploded anterior-posterior sectional view of the releasable attachment unit shown in FIG. 19;

FIG. 21 is an enlarged saggital or medial-lateral sectional view of the assembled releasable attachment unit shown in FIG. 17;

FIG. 22 is an enlarged anterior-posterior sectional view of the assembled releasable attachment unit shown in FIG. 20;

FIG. 23 is an enlarged anterior-posterior sectional view similar to FIG. 22, but showing a ball member displaced to a released position in response to a force overload condition;

FIG. 24 is an enlarged anterior-posterior sectional view similar to FIG. 23, but illustrating threaded retraction of an inner adjustment ring to relieve spring-loaded retention forces acting on the ball member, thereby facilitating return movement of the ball member to a normal operating position; and

FIG. 25 is an enlarged anterior-posterior sectional view similar to FIG. 24, and depicting return displacement of the ball member to the normal operating position.

DETAILED DESCRIPTION

OF THE INVENTION

As shown in the exemplary drawings, an attachment system referred to generally by the reference numeral 10 in FIGS. 1 and 5-10 is provided for releasably connecting an external or exoskeletal prosthesis 12 in a bone anchored mounting system of the type having an implanted bone anchored mounting post 14. The attachment system 10 is designed for secure and stable attachment of the bone anchored mounting post 14 to the external prosthesis 12, such as a prosthetic limb or the like for an amputee. In accordance with the invention, the attachment system 10 includes a safety release means or mechanism which provides a substantially rigid and direct-coupled attachment of the prosthesis 12 to an externally protruding fixator structure 16 formed on or carried by the implanted mounting post 14, to accommodate a substantially normal range of force loads encountered during substantially normal movement and/or use of the prosthesis 12. However, the safety release mechanism is also designed for displacement and ultimately for breakaway separation in response to an applied force load exceeding a predetermined design limit, thereby safeguarding the prosthesis and the bone-mounting post attachment interface against undesired fracture failure.

The releasable attachment system 10 of the present invention is particularly designed for use with external or exoskeletal prosthetic fixation or mounting systems of the type having the internal, implanted bone anchored mounting post 14 which is surgically attached to and securely supported by patient bone, as by means of osseointegration or the like. For example, with reference to FIGS. 2-4, an amputated patient limb 18 such as the upper leg in the case of a transfemoral amputee includes a portion of a long patient bone 20 such as the femur which, prior to amputation, anatomically supports a range of loads encountered during normal ambulatory movements. When amputated, as viewed in FIG. 2, the femur 20 is surgically severed, and upon healing is covered by soft stump tissue 22 including skin and the like.

FIG. 3 shows the bone anchored mounting post 14 in the form of an elongated tube or rod constructed typically from a high strength and biocompatible metal or the like and adapted for secure affixation within the intramedullary canal 24 of the long patient bone 20. In this regard, mounting post affixation can be obtained by a threaded post construction (not shown) adapted for thread-in placement into the medullary canal 24, or by alternative affixation means (also not shown) such as press-fitting, and/or by the provision of a bone ingrowth surface or surfaces on the mounting post 14. The fixator structure 16 comprises an elongated post or pin carried by or formed integrally with the implanted bone anchored mounting post 14, and protrudes therefrom through the overlying soft stump tissue 22 to an externally positioned lower or distal end. As shown in FIGS. 3-4, the lower or distal end of the fixator structure 16 includes or carries a mounting element 26 such as the illustrative radially enlarged mounting flange for releasable connection to the prosthesis 12. This releasable connection is provided by the attachment system 10 of the present invention.

FIG. 1 shows the attachment system 10 in accordance with one preferred form of the invention. As shown, the system 10 including the safety release mechanism comprises a first component in the form of an upper socket member 28 for spring-loaded clamp-on and substantially snap-fit releasable reception and retention of the mounting flange 26 on the fixator structure 16. This upper socket member 28 comprises a generally cup-shaped structure having a sturdy and rigid base plate 30 in combination with an upstanding sturdy and rigid peripheral wall 32 which cooperates with the base plate 30 to define an upwardly open, generally cup-shaped receptacle. A plurality of at least two jaw elements 34 are pivotally mounted at or near an upper margin of the peripheral wall 32 in a radially inwardly projecting orientation. Springs 36 urge these jaw elements 34 toward a normal position pivoted downwardly relative to the peripheral wall 32.

With this construction, the spring-loaded jaw elements 36 cooperate with the base wall 30 and associated peripheral wall 32 to define a pocket 38 (FIG. 8) having a size and shape for clamped, substantially snap-fit reception of the mounting flange 26 on the fixator structure 16. The downwardly loaded jaw elements 36 springably support and retain the mating flange 26 in an essentially fixed position relative to the socket member 28, throughout a normal range of mechanical loads. However, as will be described in more detail, the spring-loaded jaw elements 36 are designed to accommodate movement of the mounting flange 26 relative to the socket member 28 when a force overload condition occurs.

A relatively short tension member or tension band 40 (shown in FIG. 5) is suitably connected to the underside of the socket member base plate 30, and extends downwardly therefrom for suitable connection to an upper face of a lower base link 42. This lower base link 42 comprises a second component and is shown connected to the prosthesis 12 which may include one or more mechanical links secured to each other by appropriate fasteners 13 or the like. A plurality of radially outwardly and downwardly open detent seats 44 are defined between a sawtooth array 46 protruding downwardly from the underside of the base plate 30. A corresponding plurality of radially projecting detent pins 48 are carried by or formed on the lower base link 42 for respective seated engagement within the detent seats 44 of the sawtooth array 46. In a normal position, the tension band 40 (which may be formed from a strong and longitudinally resilient material such as metals, plastics, wood and composites) draws the lower base link 42 upwardly for secure and stable, substantially rigid seated engagement of the detent pins 48 within the sawtooth detent seats 44. However, and as will be described herein in more detail, the tension band 40 accommodates relative movement between the upper socket member 28 and the lower base link 42 when a force overload condition occurs.

FIGS. 5-8 illustrate safety release operation of the attachment system 10 in response to a bending force overload condition, wherein a bending force illustrated by arrow 50 is encountered with a magnitude exceeding a predetermined maximum limit. Upon such bending force overload, the tension band 40 in initially stretched (FIG. 5) to accommodate pivoting motion of the lower base link 42 away from the sawtooth array 46 at the underside of the upper socket member 28. Accordingly, in the presence of a relatively minor bending force overload, the tension band 40 springably or elastically permits a limited amount of relative movement between the socket member 28 and base link 42 to protect the prosthetic components including the attachment interface of the implanted mounting post 14 with patient bone 20 against risk of fracture failure.

Upon encountering a larger magnitude bending force overload, as viewed in FIG. 6, the spring-loaded jaw elements 36 are designed to displace. That is, the mounting flange 26 at the lower end of the fixator structure 16 bears against the underside surfaces of the jaw elements 36 and forces them to pivot upwardly in a manner permitting limited relative movement therebetween. If the bending force overload condition is severe enough, the jaw elements 36 will continue to pivot upwardly as viewed in FIG. 7 to accommodate complete release or separation of the socket member 28 from the mounting flange 26 (FIG. 8). Such socket member separation is, of course, accompanied by complete release or separation of the prosthesis 12 from the amputated limb 18. While such prosthesis separation renders the prosthesis temporarily ineffective (until re-attached to the fixator structure 16) and may cause the patient to fall, e.g., when the prosthesis comprises an artificial leg, the prosthetic components and the patient bone 20 are protected against fracture failure.



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stats Patent Info
Application #
US 20120316657 A1
Publish Date
12/13/2012
Document #
13589319
File Date
08/20/2012
USPTO Class
623 32
Other USPTO Classes
International Class
61F2/78
Drawings
15



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