5- to 9-year Survivorship of Single-radius, Posterior-stabilized TKA

We studied 1030 consecutive cemented primary TKAs performed by the primary author (OMM) using a single-radius, posterior-stabilized total knee prosthesis with 5 years’ minimum followup to determine whether an accelerated early failure rate was associated with this design. At 5 to 9.5 postoperative years, 32 knees had been revised at an average of 2.4 postoperative years (range, 0.1-8.2 years) because of infection (11), periprosthetic fracture (10), aseptic loosening (eight), stiffness (two), and late hemarthrosis (one). Four had only the tibial insert revised. One-half of all failures occurred within 1.5 years. The cases of aseptic loosening involved the femoral component in one patient, tibial component in five, and both components in two. With only seven patients (0.7%) having unknown outcomes, the overall failure rate was 4.9 per 1000 person-years for the study period. The Kaplan-Meier survivorship using any part of the prosthesis removed or revised for any reason as the end point was 95.8% (95% confidence interval, 93.7%-95.5%), and with aseptic loosening as the end point, it was 98.6% (95% confidence interval, 96.5%-99.4%). The midterm survivorship rates were comparable to those of other posterior-stabilized total condylar designs and are not suggestive of excessive risk of early failure.

Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.