32 – RANDOMISED CLINICAL EVALUATION OF BONE MINERAL DENSITY VARIATION USING CEMENTED TITANIUM VERSUS NON-CEMENTED TRABECULAR METAL TIBIAL BASE PLATES IN PRIMARY TOTAL KNEE ARTHROPLASTY

Abstract

Purpose: Bone stress transmission by an implant has been demonstrated to be inversely proportional to its rigidity. Since trabecular metal has a high elasticity modulus, it is hypothesised that it should have a preservative impact on bone mineral density (BMD) loss. No current studies prospectively compare BMD variations using such implants.

Method: A randomized study recruiting 65 patients with osteoarthritis of the knee, were assigned to a cemented titanium or a non-cemented trabecular metal tibial base plate. Each patient had a DXA scan of the proximal tibia on the TKA side at two weeks, six months, one and two years follow-up. Analytic methods for DXA scans were standardized (Variation coefficient=0,59–0,84%), and BMD variation compared between groups using the Student t-Test.

Results: Versus early post operative evaluation, BMD loss was found in the two groups. Fixed effects on BMD, such as patient’s height (p< 0.001) and tibial implant size (p=0.04) were demonstrated. Patella resurfacing and polyethylene thickness had no effect on BMD. BMD loss was more important under titanium implants (−30.9%) than trabecular metal implants (−6.3%). The most affected area was the metaphysis (p=0.002) compared to the diaphysis (p=0.054).

Conclusion: Trabecular metal tibial base plate seems to diminish BMD loss under tibial implant compared to traditional titanium base plate. A long-term study will be necessary to determine the tibial trabecular metal component survival rate.