Preoperative assisted navigation for total knee arthroplasty (TKA): preliminary results

Objectives To achieve a successful and durable Total Knee Arthroplasty (TKA) the mechanical axis, with balanced flexion-extension gaps, must be restored. Preoperative assisted navigation aims to avoid the pitfalls associated with conventional alignment techniques and computer navigation, whilst maintaining the accuracy of computer assisted surgery. MRI scans generate a 3D model of the patient\u2019s knee, on which patient-specific resin cutting jigs are moulded. These enable accurate pin placement for the standard resection instrumentation. The aim of this study was to evaluate early clinical, functional and radiographic results of TKA performed with preoperative assisted navigation. Materials and Methods From January 2010 to date, 30 osteoarthritis patients, candidates for TKA, agreed to undergo the pre-operative MRI protocol. There were 21 women (70%) and 9 men (30%), average age of 72.5 years (range 55-82 years) and body mass index of 29.12 (range 26.2-33.5). Preoperative alignment was normal in 7 knees (23%), varus in 18 knees (60%), valgus in 5 knees (17%). Preoperative flexion contracture was observed in 14 knees (46.5%). All procedures were performed by the 2 senior Authors. A cemented posterior-stabilised prosthesis (Vanguard, Biomet Inc.) was implanted. We recorded the blood-loss (intra-operative, at 24 hrs, at 3 days and 7 days), requirement for blood transfusions, operative time, and use of analgesic in the post-operative period. Any changes to the pre-operative planning (eg bone cuts, component sizes) were noted. Functional recovery was evaluated using the Functional Independence Measure (FIM) and the Barthel Index at 15 and 45 days and with the Knee Society function score at 45 days and at final follow-up. Radiographic and clinical results were evaluated with the Knee Society clinical score at 45 days and at final follow-up. Results The average operative time was 73 min. (range 57-86). The peak of haemoglobin loss was at 3 days and averaged 3.7 gr (range 2.6 \u2013 5.7). At 15-day follow-up, FIM score was 96.2 (range 82-100) and Barthel Index 120.3 (range 97-126). In all cases, radiographs showed satisfactory component position and restoration of normal alignment (2\ub0-7\ub0 valgus). In 5 cases, a 1-size smaller femoral component was implanted. Conclusion Our preliminary results in 30 TKAs show good restoration of limb alignment and component rotation in all cases. Component sizing seems to be less accurate, although the choice of a 2mm-smaller femoral component may be highly subjective. Operative time is similar to that of conventional technique, although the first cases were affected by a learning curve and the prudence of the surgeon who double-checked the positioning of the jigs using conventional means. Further larger controlled studies, with longer follow-up and a proper analysis of cost-effectiveness will be necessary to validate this new system, although our initial results seem to be encouraging