Implant Fixation
The loss of fixation between implant and bone is a common problem in joint arthroplasty and remains the most frequent cause of implant failure. Different fixation modalities of implant to bone are being investigated, including advanced techniques of cement fixation in the elbow, and the use of stems to stabilize the glenoid implant of the shoulder. In addition, we are developing new methods to achieve occlusion of the intramedullary canal prior to cement delivery. We have explored in detail the fixation of the glenoid component in shoulder arthroplasty with special interest in the influence of keel fixation and polyethylene thickness.
Cross-sections of specimens prepared in the laboratory showing the effect of cement delivery techniques for fixation of the stemmed (humeral) implant in elbow arthroplasty. On the right is a specimen prepared using hand-packing of cement; on the left is the result achieved when cement is delivered using advanced cementing techniques. The latter achieves a more uniform distribution of cement, enhanced apposition to bone and improved interface strength.

This schematic illustrates an in-vitro test set-up to measure the relative motion of the glenoid component (of a shoulder replacement) to bone for various loads applied to a metal sphere (representing the humeral head). Studies to date have examined the effect of implant thickness, keel size, screws and cement.

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