Abstract
Introduction: The Depuy Pressed Fit Condylar (PFC) total knee arthroplasty (TKA) is well established with reported 10-year survival rates of 93–97%. The PFC was modified, leading to the introduction of the Sigma TKA in 1997. The theoretical advantages of the Sigma system include increased contact area between the femoral component and the tibial insert. We report the first 5-year clinical and radiographic follow-up data for the Sigma TKA.
Methods: Over a ten-month period, 211 Sigma TKAs were performed in 179 patients. Patients were seen at a specialist nurse-led clinic at admission and at 6 months, 18 months, 3 years and 5 years after surgery. Data were recorded prospectively at each visit. Radiographs were obtained at the 5-year follow-up appointment.
Results: Of 211 knees, 187 (150 patients) were alive at 5 years. 5 were lost to follow up. 5 knees (2.4%) were revised: 4 for infection and 1 underwent change of polyethylene insert at 4.9 years. 5-year survival with an endpoint of revision for any reason was 97.4%; with an endpoint of revision for aseptic loosening it was 99.5%. The median American Knee Society score was 93/100 at 5 years compared with 25/100 at admission. Of 145 radiographs, 17 (11.7%) showed radiolucent lines. None showed radiographic loosening of either component. 28 (19.3%) had alignment outside the range of 7±3° valgus.
Discussion: These results suggest that the Sigma TKA gives excellent clinical results after five years. Further follow-up studies are required to see if this performance is maintained in the long term.
Honorary Secretary – Mr Roger Smith. Correspondence should be addressed to BASK at the Royal College of Surgeons, 35 - 43 Lincoln’s Inn Fields, London WC2A 3PN
