CORA ABSTRACT #II - 7

A QUANTITATIVE ANALYSIS OF BONE SUPPORT WITH CEMENTLESS SYNERGY AND PRODIGY TOTAL HIP REPLACEMENTS

J.L. Howard

A.J. Hui

R.B. Bourne

C.H. Rorabeck

S.J.M MacDonald

R.W. McCalden

Purpose: To determine how Synergy (tapered) and Prodigy (cylindrical) cementless stems differ in their mode of fixation to the proximal human femur.

Materials and Methods: Six pairs of embalmed cadaveric femurs were radiographed to exclude unsuspected pathology, to allow inclusion of only Dorr A or B proximal femoral morphologies and to allow for implant templating. An experienced orthopaedic team prepared the femurs and implanted the femoral stems. After implantation, the femurs were imaged in a Spiral CT scanner and analyzed using custom-developed imaging software.

Results: The Synergy implants had a mean cortical contact area of 307 mm² and a mean total contact area of 2487 mm². The Prodigy implants had a mean cortical contact area of 1770 mm² and a mean total contact area of 3623 mm². The cementless Synergy stem features proximal, cancellous bone contact and a three-point fixation pattern. The cementless Prodigy stem demonstrates cortical support in the distal aspect of the stem.

Conclusion: Synergy and Prodigy femoral implants differ in the amount and distribution of contact along the length of the stem as expected by their respective designs. Distinctions between these implants in their mode of fixation may have important implications on outcomes, especially in the prevalence of stress shielding and thigh pain.