Does improved instrumentation result in better component alignment in total knee arthroplasty?

Accurate component alignment and joint line reproduction in total knee replacement (TKR) is crucial for successful clinical outcome. Advances in instrumentation and better understanding of the biomechanics can help to achieve better three dimensional alignments of TKR components and joint line restoration. We compared the accuracy of component alignment and joint line restoration with the use of 2 different TKR instrumentation kits (an older Gobot and a newer Xcelerate). Retrospective study of 150 consecutive patients undergoing primary TKR had their pre and post-operative x-rays reviewed. Seventy-five patients (group A) had their TKR using the older instrumentation kit (Gobot) and 75 (group B) had the newer version (Xcelerate). The positioning of the prosthesis components were assessed using the American Knee society radiographic evaluation method and the joint line position using the Figgie's method. The results from the two groups were statistically compared. There was a significantly greater elevation of the joint line position in TKRs done with the Gobot instrumentation (mean 4.49 mm vs. 2.71 mm in group B, P=0.03), and significant differences in the mean tibial component angle cTCA (group A 88.6°, group B 90.1°, P=0.04) and the mean Q angle (group A 6.28° valgus, group B 8.45° valgus, P=0.04). Use of the newer Xcelerate instrumentation was associated with better restoration of joint line position, however the femoral component flexion and posterior slope of the tibial component ere found to be above the desired level. Hence the overall differences between the two groups were found to be small.