COMPUTER ASSISTED REVISION TOTAL KNEE REPLACEMENT

Introduction Computer assistance can be valuable in positioning of knee prostheses when the bone interface is in the form of bone graft. The efficacy of this technique can be checked using the Perth CT Protocol for knee prosthesis alignment. Methods Fourteen patients are presented who had an allograft revision total knee replacement. The entire prosthesis had to be removed and this resulted in bone deficits sufficently severe to require bone grafting. The Stryker computer navigation system was used. The final outcome was subsequently checked using a multi-slice CT which provided a six paramenter evaluation of the alignment of the knee prosthesis. Results The technique produces excellent alignment of both components in the coronal plane, less good results in sagittal plane and the greatest problems are in the axial plane with femorotibial mismatch occuring in 50%. The mean mal-alignment index is 4.0:1.4. This compares with an index of 2.6:1.3 in navigated primary TKRs. Conclusions Computer assistance provides significant help in the revision total knee replacement but does not produce perfect alignment in every case. Further refinement of the techniques are still needed.