Safe tibial subsidence pattern of a medial pivot knee. An RSA study.

Introduction: Micromotion analysis predicts component fixation survival in Total Knee Arthroplasty (TKA) but a paucity of literature exists for medial pivot designs. This clinical study examined the tibial component micromotion in a second-generation medial pivot TKA.

Methods: This prospective single-center clinical cohort trial involved 35 patients with a mean patient age of 71 years. Operations were performed by one experienced arthroplasty surgeon using the Saiph implant (MatOrtho). All patients received fully cemented fixation with patella resurfacing. Other variables were standardized. Radiostereometric Analysis was performed at 6 weeks, 12 and 24 months to monitor tibial component behavior.

Results: Benign, minor micromotion was shown with cemented fixation. At 12 months median subsidence was 0.04 mm and Median Maximal Total Point Motion was 0.44 mm. At 24 months the median subsidence was 0.02 mm and Median Maximal Total Point Motion was 0.46 mm. No tibial components were revised.

Conclusion: Low degrees of subsidence and Maximum Total Point Motion imply stable fixation of these medial pivot implants and high patient satisfaction was achieved. This is consistent with favorable long-term performance.