A RADIOLOGICAL STUDY OF THE ALIGNMENT OF DIFFERENT TOTAL KNEE ARTHROPLASTY PROSTHESES

Abstract

Introduction and Aims: Aim of the study is to show whether the accuracy of alignment of a total knee pros-thesis is more dependent on the instrumentation or the skills of the surgeon.

Method: Forty patients that had total knee arthroplasties performed between September 1997 and September 1999 have been analysed. The results of prospective randomised trial using the LCS (Depuy) and IBII (Zimmer) prostheses have been analysed, as well as results using the Scorpio (Stryker) and Profix (Smith + Nephew) total knee replacement systems. Patients were evaluated according to a radiographic protocol, a modification of the Knee Society total knee arthroplasty x-ray evaluation and scoring system. All patients had long leg standing x-rays in full extension and neutral rotation. Lateral x-rays were taken in neutral rotation with a maximum of 10 degrees of flexion. The femoral varus/valgus alignment is recorded on the AP x-ray as the Alpha angle, and the tibial alignment as the Beta angle. On the lateral x-ray the Gamma angle records the femoral flexion and the Theta angle the tibial prosthesis alignment along the tibial shaft.

Results: The results were statistically analysed by the Department of Statistics at the University. Results were stratified according to both the instrumentation used and the surgeon. These showed that there was no statistical difference between the alignment of the different prostheses, irrespective of the surgeon performing the procedure.

Conclusion: From this study we concluded that no one set of instrumentation used while performing a total knee replacement was superior to another. As long the surgeon is familiar with the instrumentation the final alignment of the prosthesis will be satisfactory.