Aim

The aim of the study was to assess the impact of a self aligning unidirectional mobile tibial bearing and the use of a patella button on lateral patella release rates within a knee system using a common femoral component for both the fixed and mobile variants.

Summary: This study compares the outcomes of a large series of 683 cruciate sacrificing (PS) and cruciate retaining (CR) TKRs at minimum 2 years follow-up. Patients with a PS component showed a greater improvement in the pain and knee components of the American Knee Society Score at both 1 and 2 years post-operatively and also demonstrated a greater improvement in knee flex-ion at both time points.

Introduction: Excellent clinical results have been reported with both PS and CR TKR designs. A number of randomised trials comparing the two techniques have failed to demonstrate a difference in outcomes based on the numbers of patients recruited.

It is hypothesised that cruciate retention in total knee arthroplasty may result in improved kinematics of the knee by maintaining the femoral rollback seen in the normal knee, resulting in improved function. This study compares clinical outcomes in groups having PS and CR total knee arthroplasty and report the results at 1 and 2 years post-operatively.

Methods: A total of 683 patients undergoing TKR surgery were consecutively enrolled in a prospective multi-centre study with 2 arms. In the first arm patients receiving a PS component were randomised to receive either a mobile bearing (176 patients) or fixed bearing (176 patients) implant. In the second arm, patients receiving a CR component were randomised to receive either a mobile bearing (161 patients) or fixed bearing (170 patients) implant. All patients were assessed pre-operatively and at one and two years postoperatively using standard tools (Oxford, AKSS, Patellar Score) by independent nurse specialists. The data from the 2 arms of the trial were then analysed to compare differences between PS and CR implants.

Results: Patients with a PS component showed a greater improvement in the pain component of the AKSS at 1 year (p=0.0003) and at 2 years (p=0.0085) post-op.

Patients with a PS also showed a greater improvement in the AKSS knee score at 1 (p=0.0001) and 2 (p=0.001) years.

Knee flexion improvement was also greater in the PS group at 1 (p=0< 0.0001) and 2 (p=0.0035) years.

PS knees also achieved better outcomes in these variables in the mobile and fixed subgroups.

There were no other significant differences in the scores between the two groups at any stage.

Conclusion: This study reports on a large prospective multi-centre series of PS and CR TKRs. Improvements in pain and knee components of the AKSS score and knee flexion at both 1 and 2 years follow-up were greater in PS knees. Although this difference was statistically significant, differences in real terms were relatively small.