Total knee arthroplasty (TKA) in patients with established knee osteoarthritis and major varus, mostly due to constitutional proximal deformity, remains a challenging procedure. Orthogonal cuts result in asymmetric bone resection and subsequent bone-related laxity or difficult release. A procedure that combines opening high tibial osteotomy (HTO) and TKA in the same sitting to address such major deformities is possible. But for this combined operation, precise planning and an exact intraoperative transformation of the planning is required. The assumption that the results could be predicted better by means of a navigation system was analyzed.
The precision of surgery with computer-based navigation was compared to conventional surgery. A comparative prospective study was conducted using an expert surgeon. Between 2005 and 2015, we performed 20 procedures on knees with average preoperative 18° (range, 15-25°) varus. Tibial valgus osteotomy plus TKA was performed in one sitting. It allows the surgeon to do a more sparing medial release and to achieve proper realignment with a concomitant well-balanced prothesis. A group of 10 patients had conventional surgery and the other 10 had surgery performed with computer-based navigation for both osteotomy and TKA. By means of this system, the desired mechanical axis is obtained with real-time monitoring of the coronal and sagittal plane on the navigation without intraoperative x-ray control. The positioning of the saw-jigs for the femoral and tibial cuts of the arthroplasty was also performed with the help of the navigation system.
Postoperative mean femorotibial varus was 1.5° (range, 0-5°) with better alignment for the computer-based navigation. The mean correction following osteotomy was 16° (range, 12-24°). The intraarticular part of the deformity due to cartilage wear was addressed by the TKA. No release was done during surgery. The patients were mobilized early with limitation in range of motion up to 90° of flexion during the two weeks and were allowed full weight after. No instability and no complications were observed. On assessing radiological coronal alignment of the prostheses, there was better alignment of 0.5° varus (range, 0-3° of varus) in the computer navigation group compared to the traditional group (2.5° varus; range, 1-5° of varus). The navigation group showed better tibial slope maintenance (mean change, + 0.5°, p=0.732), whereas it was increased significantly in the conventional group (mean change, +4.2°, p<0.01). The average number of fluoroscopy shots for the computer navigation group was 2.8 (95% CI, 1.2-6.5) versus 9.4 in the control group (95% CI, 5.3-12.4). This represented a shorter (p<0.001) time of 11.4 seconds of irradiation for the computerized navigation technique compared to 36.2 seconds of irradiation for the traditional technique.
Computer navigation improved precision with less radiation. The findings of this study suggest that computer navigation may be safely used in a complex procedure when combined with total knee arthroplasty and opening wedge high tibial osteotomy in one sitting.