Does implant design and surgical technique improve the clinical outcome in total knee arthroplasty?

Excerpt

Recently, a new generation of prostheses for total knee arthroplasty (TKA) were introduced by different companies in order to improve the range of motion, clinical outcome and finally patient satisfaction. However, the basic principles in designing implants for total knee arthroplasty have not changed much over the last two decades. We still need to resect the anterior cruciate ligament (cruciate retaining, CR TKA) or remove both the anterior and posterior cruciate ligaments (posterior stabilised, PS TKA). The femoral component is designed to optimise patella tracking and to unload the patello-femoral compartment. Single and multiple radius designs are being used for the femoral condyles, both showing good reasons for preference. The multi-radius design of the femoral component respects the anatomical shape of the femoral condyles and the physiological change of flexion/extension axis during knee motion. However, CR mobile bearing TKA influence the flexion/extension axis as shown by Iacono et al. [10] in a study published in the current issue. The single-radius design presumes a fixed axis of flexion/extension, which lies slightly posterior to the natural one. A slight posterior placed axis increases the quadriceps moment arm and improves the efficiency of quadriceps muscle function [16]. In clinical practise, better range of motion and less pain, in particular, when rising from a sitting position has been observed with the single-radius design [14]. These findings are in harmony with a biomechanical study by Ostermeier and Stukenborg-Colsman. However, other studies did not show any differences in range of motion or clinical outcome between the single- and multiple radius designs [7]. Both concepts raise the questions whether one should restore anatomy as exactly as possible or as the osteoarthritic knee’s anatomy is altered by the disease process anyway and hence one should aim for the best knee function and modify the components accordingly? …