TKA WITH FIXED OR MOBILE BEARINGS IN THE SAME SYSTEM: LONG TERM RESULTS WITH SPECIAL CONSIDERATIONS TO THE PATELLA

Abstract

Purpose: To present 8 year results of a prospective clinical study of 246 patients with the Innex total knee system performed between 2000 and 2002.

Methods: 88 men and 158 women aged between 39.3 to 92.8 (mean, 71.2) years who underwent primary TKAs using the Innex prosthesis were followed up for up to 8 years. TKA was performed using ultracongruent mobile or fixed bearings, both groups with or without patella replacement. All TKAs were cemented. Patients were assessed using the Knee Society Clinical Rating System.

Results: The mean ROM improved from preoperative 105.54° up to 110.05° at the last FUP. The mean total Knee Society Score before surgery was 112.04 (range, 52–160) and improved post op up to 179.49 (55–200). There were 2 postraumatic patella fractures (14 and 49 months after surgery), 2 patients without patella replacement showed peripatellar pain syndrome and femoropatellar overload. One became fine after conservative treatment, the other patient hat patella replacement 55 months after initial surgery. 3 patients had early mobilisation under anaesthesia for postoperative stiffness. There were no deep vein thromboses or pulmonary embolism. Revisions were done in 6 patients. 4 revisions were done due to aseptic loosening and 2 due to deep infections. After 8 years we saw a survival rate of 96.09% with revision or indication for revision for any reason as the endpoint. With aseptic loosening as the endpoint survival rate was at 96.52%. Post operative results in TKA with fixed bearings and patella replacement (ROM=126.67°,KSS=190.5) where superior compared to fixed without patella replacement (ROM=118°,KSS=186). In TKA with mobile bearings again those who had patellar replacement showed somewhat clinically better results (ROM=114.44°, KSS=185.89).

Conclusion: The Innex TKA showed generally good longterm results. Selection to fixed or mobile was in our series depending on praeoperative stability and fixed preferable used tor rheumatoid patients. Patella replacement gave better results in both groups.