5-YEAR RESULTS OF THE PFC SIGMA TOTAL KNEE ARTHROPLASTY: A STUDY OF 525 CASES

Aim: To report the intermediate clinical and radiological results of a consecutive series of knee arthroplasies using PFC Sigma endoprosthesis. Methods: 525 total knee replacements (469 patients) were performed from Aug 97 to Jun 01 using the PFC Sigma components. Cruciate retaining femoral component was used in 219 knees. All patients were prospectively followed up at 6 weeks, 3 months and yearly. Pre operative HSS knee scores and Oxford knee scores were compared with annual scores. Quality of life was assessed using SF12 questionnaire. Knee Society scores were used to assess the radiographs. The average follow up was 61 months (36–84). 11 patients lost to follow up. Results: Of the 469 patients, 64% were females. Mean age was 74.2 yrs(59–90). Valgus deformity of at least 10 deg was present in 87 (16.5%). Patella resurfacing was performed in 80.5%. A lateral release was performed in 20 patients. Post operative mobilisation was standardised in all patients. 34 patients developed radiologically proven DVT. 24 patients died to unrelated causes. 21 were lost to follow up. 16 (3%) patients developed superficial and 6 developed deep infection. 4 patients underwent revision surgery (3 – infection,1- catastrophic failure). The HSS scores improved from 29(16–65) to 86(59–97) at final follow up (p=0.004). Pre operative Oxford knee scores improved from 10(6–31) to 43(37–48) at last follow up (p=0.008). Radiological knee society score for the femur were less than 5 in 477/478 patients and 7 in 1 patient. The scores for the tibia were less than 5 in 475/478 patients and 6 in 3 patients. Average femoral flexion was 1– 9.2 deg (3.9), knee valgus angle 0.5 – 7.4 (3.5) degrees and the tibial slope was 3.1 deg(0–7.1). SF 12 health scores revealed a good functional outcome of both the physical and mental components. With failure defined as repeat revision because of aseptic loosening, the rate of survival at 5 years months was 99.1% and overall survival at 5 years with removal or repeat revision of any component for any reason as the end point was 97.5%. Conclusion: Our prospective study of patients with primary knee arthroplasties supports the use of the PFC Sigma total knee proshesis. Our results show excellent clinical outcome comparable with other prostheses. A longer follow-up is needed to establish the durability and longevity of this prosthesis given its excellent intermediate term results