SHOULD THE POSTERIOR CRUCIATE LIGAMENT BE SACRIFICED FOR TOTAL KNEE ARTHROPLASTY ? 500 PROSTHESES WITH PRESERVATION OF THE POSTERIOR CRUCIATE LIGAMENT FOLLOWED A MEAN SEVEN YEARS

Abstract

Purpose: At a time when total knee arthroplasty (TKA) with an ultra-congruent tibial plateau or a mobile plateau are advocated by many, the question is whether TKA with a fixed plateau preserving the posterior cruciate ligament (PCL) should be abandoned. We analysed the results of 500 Wallaby I TKA with preservation of the PCL and presenting asymmetrical and divergent femoral condyles with a fixed, also assymetrical tibial plateau, at mean follow-up of seven years (1–10).

Material and methods: This prospective multicentric study was performed by junior and senior surgeons. Mean patient age was 70.11 years and 91.4% of the patients had primary or secondary degenerative disease. Prior surgery had been performed in 130 knees, mainly for osteotomy (n=40, mostly tibial) and revision of uni-compartmental or total prostheses (n=18). The mean preoperative IKS knee score was 26.11 points, the function score was 29.54. Preoperative alignment was correct for 11.26% of the knees, 27.16% presented > 4° valgus and 61.56% > 3° varus. Nearly all tibial and patellar pieces were cemented. 5.8% of the femoral pieces were not cemented. A prosthesis was implanted on the patella in all knees except four. There were two early infections, one popliteal sciatic paralysis and twelve wound healing problems. General mobilisation under general anaesthesia was performed in 53 knees (10.6%).

Results: Twenty-two patients were not retained for analysis, fifteen lost to follow-up and seven deceased at one year. Among the 478 knees followed for one to ten years, there were six late infections (1.25%), one aseptic bipolar loosening (0.2%), 25 patellar fractures (5.23%) including three which required revision (two cerclage, one prosthesis removal), three periprosthetic femur fractures without effect on the clinical or radiographic outcome, one traumatic tear of the medial collateral ligament, and two secondary tears of the PCL without clinical consequences. There were no revisions for instability, generally considered the most frequent reason for TKA revision. The mean postoperative IKS score was 90.6 points and the function score was 59.7 points basically due to patient age and comorbidity. The eight-year survival (Kaplan-Meier method) was 98.2% (95%CI: 99.4–96.9) irrespective of the reason for revision and 99.2% (95%CI 100–98.4%) if the revision was performed for a mechanical problem. Radiographically, more than 70% of the knees were aligned (between 3° valgus and 2° varus) and more than 90% were between 5° valgus and 5° varus. Although it was difficult to measure radiographically polyethylene wear, there was only one case of > 2 mm wear with osteolysis found in 50 knees selected randomly among the knees with more than seven years follow-up.

Conclusion: This study, like others reported by authors preserving the PCL, show that preservation of the PCL limits the risk of instability, allowing excellent clinical and radiographic outcome without important polyethylene wear, opening perspectives for good long-term results.