UNCEMENTED TITANIUM GEMINI FEMORAL STEM - MIDTERM RESULTS WITH A MINIMUM 8-YEAR FOLLOW UP

Abstract

This is a retrospective assessment of the performance of a consecutive series of the titanium uncemented Gemini femoral component. The Gemini uncemented stem (De Puy) is a modular titanium femoral stem with a cobalt chrome head. It has proximal porous coating allowing stable fixation by bony in-growth and a smooth distal stem allowing mechanical fixation.

Using a direct lateral approach, 152 consecutive patients underwent a total hip replacement using the Gemini uncemented femoral component and an unce-mented cup. Patients were regularly assessed clinically (Harris hip score) and radiologically (Engh’s criteria for fixation of the prosthesis). Kaplan Meier survivorship analysis was used to assess survival.

16 patients were lost to follow-up and 30 were dead with the THR in situ, leaving 106 hips for final analysis, at a mean follow-up of 106 months. The mean age of the group was 60 years (range 25–83) and OA was the commonest diagnosis. The mean Harris hip score improved from 34 to 92(range 83–100). 7 stems have been revised, four of which for aseptic loosening and a further two are radiologically loose. Mean time to revision was 41 months (range 14–76). By Engh’s criteria, 90% of the hips had stable bony fixation; only 4% of the patients complained of thigh pain at final follow-up. Kaplan Meier survivorship analysis with aseptic loosening as endpoint indicated a survival of 93% at 8 years.

A mid-term result with the Gemini uncemented stems at a mean follow-up of approximately 9 years was excellent. This is in sharp contrast to the cemented stem of similar design, even though the uncemented version was used in younger and more active group of patients. Titanium alloy is biocompatible allowing for excellent bony in growth, making it an ideal alloy in the manufacture of uncemented stems. Having a modulus of elasticity close to that of bone explains the low incidence of thigh pain.