COMPUTER-ASSISTED TIBIAL OSTEOTOMY FOR VALGISATION: USE FOR THE TREATMENT OF 19 CASES OF GENU VARUM

Abstract

Purpose: Tibial osteotomy for valgisation is a difficult procedure with a risk of over-correction or under-correction which can have significant aesthetic, functional and medicolegal consequences. In order to improve the precision, we adapted a navigation system to tibial osteotomy for valgisation. The purpose of the present work was to evaluate the feasibility and results of this technique.

Material and methods: From March to November 2001, we used the Orthopilot system for 19 patients with genu varum. Mean patient age was 50.8±11.7 years (range 18–71). The indication for valgisation was genu varum, associated with joint degeneration (grade 1, 2, or 3 in the modified Ahlback classification) in 18. The aesthetic effect of genu varum was the only indication in one patient. Preoperatively, the mean HKA was 173.73±3.24° (range 169–178). The mechanical axis was determined with Orthopilot before performing an open medial osteotomy for valgisation which was fixed temporarily with a metal wedge to control as needed lower limb alignment. Orthopilot enabled verification of the desired axis. When obtained, the metal wedge was removed and replaced by a wedge of tricalcium phosphate (Biosorb®, B-Pharm) of the same size. The osteotomy was stabilised with a screw plate. The objective was to obtain a femorotibial axis between 182° and 186°, i.e. 2° to 6° valgus.

Results: HKA measured peroperatively with Orthopilot was 174.05±3.06°, exactly the same as on the preoperative x-rays. After oseotomy, HKA was 183.47±1.07° (180°–184°) with Orthopilot, and 183.47±1.44° (179°–186°) on the x-rays. Eighteen knees were within the objective of 182°–186° giving a success rate of 94.7%.

Discussion: Computer-assisted tibial osteotomy for val-gisation using Orthopilot is quite feasible. To have a valid assessment of this new method, results would have to be compared with a series performed without computer assistance.