WHY DO PROSTHESIS FAIL: ANALYSIS OF 100 CONSECUTIVE REVISION SURGERIES IN TOTAL KNEE ARTHROPLASTIES (TKA)

Abstract

Purpose: There is a growing demand on revision surgery in the last decade. 60 – 80% of these revisions are performed for early failure within the first three years. We are a referral center for painful and failed TKAs and have performed more then 400 revision surgeries between 2000 and 2005. In this paper we have analysed the cause(s) of failure(s) in patients with painful or failed TKAs.

Material and Methods: 100 consecutive revision surgeries were analysed using a standardized diagnostic algorithm. This included extended history, clinical evaluation with special tests and laboratory examinations. Radiographic analysis included standard x-rays, full leg standing weight bearing x-rays and special fluoroscopic views. Patients with suspicion of implant malrotation received a special computer tomography and stress x-rays. In patients with suspicion of infection aspiration of the joint and if negative a dynamic technetium and leucocyte bone scan was performed. The suspected cause(s) of failure(s) was analysed during revision surgery in all cases.

Results: In 48% malalignment (> 4°) caused overloading, pain and/or PE-wear. In 26% malrotation (> 3°) of the tibia and/or femoral component caused either patella malttracking, stiffness or flexion gap instability. In 23% pain was caused by instability either in extension, midflexion and/or full flexion. In 19% the cause of pain was infection. In 24 % several other rare causes could be identified. Only in 9% there was aseptic loosing over the time without any implantation failure. 78% of all revisions were performed within 3 years after the primary surgery.

Conclusions: Aseptic loosing, PE-wear and instability had been described as the main failure mechanisms in TKA. In this study it could be shown, that these are only secondary phenomena’s for the three main implantation failures of malalignment, malrotation and mismatch of the flexion/extension gaps. In most of the early failures within 3 years after primary implantation these revision surgeries might be prevented by a more precise primary implantation.