Introduction: High tibial osteotomy is a recognised method of treatment for malalignment and osteoarthritis in young patients. Today computer aided surgery provides a chance to improve the existing techniques with a traceable planning and a higher degree of accuracy. Intraoperative use of fluoroscopy can be reduced and the results regarding leg axis can be improved.
Method: In our department since two years nearly all patients with malalignment of the lower legs had osteotomies guided with a navigation system. We used the Medivison-Praxim system in five, the Orthopilot prototype software in 12 and the Brain LAB System in 15 patients. The most common operation type was an open wedge osteotomy of the proximal tibia. A single cut osteotomy to correct the torsion and valgus deformity after a distal femur fracture is also possible with the Brain LAB system. Stabilisation was achieved using a plate with head locking screws (Tomofix, Synthes).
The degree of correction was controlled during the operation with the navigation system and compared with pre- and postoperative 2.5D ultrasound measurements to avoid projection errors of long standing x-rays.
Results: In all cases the intraoperative analysis was possible with the navigation systems. In one case, the computer crashed down due to interference of the fluoroscopy machine. No surgical problems were noted due to computer guidance noted. Fluoroscopy was used in all cases to verify the implant position as well as the resection plane after inserting the k-wires for saw blade guidance. The additional time for navigation was about 15 minutes.
The postoperative 2.5D ultrasound leg axis analysis showed a maximum of +/− 2° difference between the pre-, intra- and postoperative measurements.
Discussion: The chance to track the patient’s leg geometry through the complete procedure until bone fixation is the main benefit of computer assistance. The chance of failure during reduction and fixation can also be minimised and potential misalignment can be improved immediately. In addition, like in navigated joint replacement, the result of the surgical treatment can be simulated and judged before any action; values can be influenced showing the consequence right away. The final result regarding the leg axis is determined not only by the computer guidance, but by the primary stability of the implant as well. The chosen Tomofix plate is supposed to provide highest initial stability.
This first results show a promising increase of accuracy while radiation can be reduced. The actual values show that the main goal to increase the intraoperative accuracy in corrective osteotomies can be achieved with computer aided surgery.
