Method and apparatus for hip femoral resurfacing tooling

Abstract

Tools and methods for implanting hip resurfacing femoral prostheses along a path defined by the axis of a shaped femoral head surface are described. The prostheses are stemless partial ball components having an outer surface shaped to conform to an acetabular socket and may be a two part design having a mating sleeve component with an internal bore adapted to receive the shaped femoral head. The tools and methods are capable of accurately implanting both one and two piece ball components and sleeves without requiring the prosthesis to have a central stem or the preparation of a stem cavity in the femoral head and neck.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates generally to systems, kits and methods for joint prosthesis installation tools. The present invention includes jigs and methods for installing a stemless ball component to a prepared femoral head along an axis defined by the prepared femoral head and jigs for installing a sleeve component for adapting a ball component to a prepared femoral head along an axis defined by the prepared femoral head.[0002]Artificial joint prostheses are widely used today, restoring joint mobility to patients affected by a variety of conditions, including degeneration of the joint and bone structure. Typically, the failed bone structure is replaced with an orthopedic implant that mimics, as closely as possible, the structure of the natural bone and performs its functions. The satisfactory performance of these implants can be affected not only by the design of the component itself, but also by the surgical positioning of the implanted component...

AI Technical Summary

Benefits of technology

[0021]It is an object of the present invention to provide a more successful surface replacement of the femoral portion of a total hip replacement based on a stemless modular approach to femoral hip resurfacing by improvements to the tooling and methods used for implanting the prostheses components.

Problems solved by technology

The satisfactory performance of these implants can be affected not only by the design of the component itself, but also by the surgical positioning of the implanted component and the long-term fixation of the implant.

Improper placement or positioning of the implant can adversely affect the goal of satisfactorily restoring the clinical bio-mechanics of the joint as well as impairing adequate fixation of the component when implanted.

This is especially important since installation of an orthopedic implant often involves an extensive and difficult medical procedure, and therefore replacement or revision of the installed implant is typically difficult and traumatic.

These stem type prostheses are very successful but when they fail the stem can create considerable damage inside the bone.

The implant can move about inside the bone causing the intramedullary cavity to be damaged.

Because a stiff stem transmits the forces more directly into the femoral shaft, such implants have the further disadvantage that they can weaken the surrounding bone nearer to the hip joint due to stress shielding.

While this method of fixation by cement provides immediate fixation and resistance to the forces encountered, and allows the surgeon to effectively position the device before the cement sets, it is not without problems.

Over time, the mechanical properties and the adhesive properties of the bone cement degrade; eventually the forces may overcome the cement and cause the components to become loose due to a failure at the cement / bone or cement / stem interface.

A shortfall of this approach is that, in contrast to components that utilize cement fixation, surfaces designed for biological ingrowth do not provide for immediate fixation because it takes time for the bone to grow into the specially prepared surface.

Prior art designs often require the entire implant to be replaced even if only a portion of the implant fails.

This is often due to the implant suffering from a decrease in support from the adjacent bone due to stress shielding or other negative effects of the implant on surrounding bone.

Small movement of the device against the bone caused friction of the bone and the bending loads on the peg often caused them to break out underneath the bony femoral neck.

These latter double cup designs commonly failed either by a crack progressing around the bone cement between the prosthetic femoral shell and the bone or by a fracture of the bone across from one side of the prosthetic femoral component rim to the other.

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