Differential porosity prosthetic hip system

Abstract

A prosthetic femoral implant for use in a hip joint, as a ball and socket type joint, is disclosed. The implant includes a modular neck having a variety of adjustable positions to adjust the lateral offset and version angle of the femoral implant in relation to the femur. The implant further includes a broad, full collar for providing a compression force increasing the interdigitation between the interface of the bone, implant and cement. The implant also includes a stem having a depression having a roughened porous surface for resisting the increased torsional loads placed on the implant due to the increased lateral offset and version angle. The stem further comprises three distinct zones, each zone having its own roughened surface creating a tripartite differential porosity.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of co-pending U.S. patent application Ser. No. 10 / 244,149, filed Sep. 13, 2002, entitled “DIFFERENTIAL POROSITY PROSTHETIC HIP SYSTEM,” which claims the benefit of U.S. Provisional Application No. 60 / 372,390, filed Apr. 12, 2002. [0002] Co-pending U.S. patent application Ser. No. 10 / 244,149 is a continuation-in-part of U.S. patent application Ser. No. 09 / 505,876, filed Feb. 17, 2000, entitled “MODULAR NECK FOR FEMUR REPLACEMENT SURGERY,” now U.S. Pat. No. 6,464,728, which is a continuation-in-part application of U.S. patent application Ser. No. 09 / 059,698, filed Apr. 14, 1998, now abandoned.[0003] All of the above mentioned applications are hereby incorporated by this reference herein in their entireties, including but not limited to those portions that specifically appear hereinafter, the incorporation by reference of all applications being made with the following exception: In the event that any port...

AI Technical Summary

Problems solved by technology

For example, recovery from an operation using the cementless system takes an average of about three months before the patient may return to any activity so that the bone may be permitted to grow into the pores of the implant, which results in a connection that has the potential to endure in the patient for a long period of time.

However, the interface between the bone, the cement and the implant may not last as long as the cementless system.

However, the system disclosed by Niederer et al. is disadvantageous for those situations where, for one reason or another, the implant must be removed and replaced.

The location of the grooves at the distal end of the femoral prosthesis is disadvantageous because during the removal process in order to completely loosen the implant from the bone the surgeon must have adequate access to those portions of the implant where bone ingrowth has occurred.

With grooves located on the distal end of the implant, the surgeon does not have adequate access to loosen that portion of the implant from the bone and the implant is, therefore, very difficult to remove.

However, this system is disadvantageous because torsional forces may still be exerted on the implant, which may loosen the implant over time.

However, this system is disadvantageous because there is a tendency for the implant to loosen from the cement due in part because the surface of the implant is smooth and does not provide a surface for interdigitation with the cement.

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