CROSS-REFERENCE TO RELATED
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates generally to modular orthopedic prostheses and, more specifically, to attachment mechanisms for securing components of a modular orthopedic prosthesis.
2. The Relevant Technology
Modular orthopedic prostheses offer many advantages to the user. By selecting independent modular components to construct a complete prosthesis, custom fitting of a patient's specific anatomy or specific bony condition can be accomplished.
Several attachment mechanisms are known in the art for connecting the components of a modular prosthesis. As used herein, collet refers to a thin cylindrical tube with longitudinally extending slots, such as those commonly used in the machine tool industry. For example, it is known in the art to use an interpositional, independent collet to connect one bone contacting component of a modular prosthesis to another bone contacting component of a modular prosthesis. However, the use of the independent collet adds another component to the sum of components required to construct the complete prosthesis. It would therefore be an improvement in the art to provide an attachment mechanism that would reduce the number of components required to construct a complete prosthesis in order to reduce cost and simplify the assembly technique.
Because of the high physiological loads borne by the skeletal structure, orthopedic prostheses are subject to high bending, shear, and torsional loads. However, independent collets and other fasteners all represent adjunctive components that do provide bone contacting surfaces and therefore necessarily require a reduction in thickness of the mated bone contacting components in order to accommodate the connection hardware. Thus, the mated bone contacting components are weaker due to the reduction in thickness associated with the accommodation of the connection hardware. It would therefore be an improvement in the art to provide an attachment mechanism that integrates the means of connection between modular components of a modular prosthesis into one or more of the bone contacting components.
One of the advantages of modular orthopedic prostheses is the capacity to select, at the time of surgery, a desired orientation between modular components. Many modular connections known in the art do not facilitate a state of partial assembly that closely replicates the final longitudinal configuration of the prosthesis, where, in the state of partial assembly, the modular components can be freely rotated with respect to each other. It would therefore be another improvement in the art to provide an attachment mechanism for modular prostheses that would accommodate a state of partial assembly that closely replicates the longitudinal configuration of the prosthesis while permitting free relative rotation between the modular components.
BRIEF DESCRIPTION OF THE DRAWINGS
Various embodiments of the present invention will now be discussed with reference to the appended drawings. It is
appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope.
FIG. lAis a cross sectional view of a tripartite attachment 5 mechanism in a disassembled state.
FIG. IB is the tripartite attachment mechanism shown in FIG. 1A in an assembled state.
FIG. 2A is a cross sectional view of another embodiment of a tripartite attachment mechanism in a disassembled state. 10 FIG. 2B is the tripartite attachment mechanism shown in FIG. 2A in an assembled state.
FIG. 3A is a cross sectional view of a still another embodiment of a tripartite attachment mechanism in a disassembled state.
FIG. 3B is the tripartite attachment mechanism shown in FIG. 3A in an assembled state.
FIG. 4 is a cross sectional view of a modular femoral hip implant having component s connected together by a tripar20 tite attachment mechanism.
FIG. 5 is a cross sectional view of a modular tibial knee implant having components connected together by a tripartite attachment mechanism.
DETAILED DESCRIPTION OF THE 25 PREFERRED EMBODIMENTS
Referring to one or more of the preferred embodiments of the present invention as depicted in FIGS. 1-5, there are three components, a body 20, a sleeve 30 and a shaft 10,
3Q adapted to connect to each other to form a tripartite, or three-piece, modular prosthesis assembly. Body 20, sleeve 30 and shaft 10 may be made from any suitable biocompatible material that can withstand the physiological loads during the lifetime of the implant. Preferentially, body 20,
35 sleeve 30 and shaft 10 would be made from biocompatible metals, such as titanium alloys, zirconium alloys, cobalt chromium alloys, or stainless steels.
Depicted in FIG. 1 is an attachment mechanism in a disassembled state. The attachment mechanism is comprised
40 of the body 20, the sleeve 30 and the shaft 10.
The body 20 has a first top end 24, a first bottom end 25, a first internal surface bounding a bore 22 extending between the first top end 24 and first bottom end 25. The bore 22 comprises an upper socket 21 and a longitudinally
45 spaced lower socket 22. Additionally, the body has an external prosthetic surface 27 adapted to either contact bone or to engage either prosthetic or anatomical articulating surfaces. For simplicity, external prosthetic surface 27 is shown in FIGS. 1-4 as a cylinder, but it is appreciated that,
50 as shown in FIGS. 5-6, the external prosthetic surfaces 27C and 27D are adapted to provide the appropriate surface for a particular prosthetic application.
The sleeve comprises a second top end 34, a shoulder 38, a second bottom end 35, a second internal surface bounding
55 a channel 36 extending between the second top end 34 and the second bottom 35. The sleeve further has an external prosthetic surface 37 extending between the shoulder 38 and the second bottom end 35. For simplicity, external prosthetic surface 37 is shown in FIGS. 1-4 as a cylinder, but it is
60 appreciated that, as shown in FIGS. 5-6, the external prosthetic surfaces 37C and 37D are adapted to provide the appropriate surface for a particular prosthetic application. The sleeve also has a tubular protrusion 33 extending between the shoulder 38 and the second top end 34.
65 Additionally, the tubular protrusion has an outer surface 31. Depicted in FIG. IB is an assembled tripartite attachment mechanism. The lower socket 22 is sized for an interference