77. COMPUTER ASSISTED CORRECTIVE TIBIAL OSTEOTOMY: A CASE-CONTROL STUDY WITH A NON-NAVIGATED SERIES

Abstract

Purpose of the study: Tibial osteotomy to correct for varus deformity is a well defined procedure. Survival has reached 80% at ten years. Nevertheless, a number of early failures are related to inadequate initial correction. Computer assisted surgery has demonstrated its efficacy for knee arthroplasty. We hypothesised that it could also improve the reliability of correction for tibial osteotomy.

Material and method: From 2007, in a prospective case-control study, 34 tibial wedge osteotomies were performed, 17 were computer assisted (Navitrack, Orthosoft) with plate fixation (Tomofix, Synthès) without wedge insertion; the objective was valgus measuring 2 to 5°.

Results: The two series were comparable for age (54.2±6 and 55.7±4.5), body mass index (28.9±6.2 and 28.7±5.7), and varus deformity (7.2±3 and 6.2±6) respectively in the standard and navigated groups. Osteoarthritis was more severe in the navigated group, with five patients stage 2 and 12 stage 2 versus one stage 1, 12 stage 2 and 4 stage 3 in the standard group (p=0.0152). The duration of the operation was not longer in the navigation group (p)0.2779). Comparisons were made for alignment at three months, between the groups and in relation to the preoperative data. There was no significant difference between the intraoperative navigation alignment and the alignment measured at 3 months: 3.6±6 and 2.5±3 at 3 months (p=0.2187). At 3 months, there was no significant difference in alignment between the two groups with 3.22 and 2.5±1.6 valgus in the standard and navigation groups respectively (p=0.2136). The objective was achieved in 25 patients: 12 in the standard group and 13 in the navigated group. In the navigation group, there were four failures, no cases of over correction, two cases of insufficient valgus at 1.5, one neutral alignment, and one recurrent varus. In the standard group, there were five failures with two over corrections at 7 and 8, two under corrections at 0 and 1, and 1 recurrent varus at 4.

Discussion: We were unable to prove that navigation improves the reliability of the correction but it did appear to avoid important errors, particularly over correction. Few series have compared standard varus navigated osteotomies, and all published series have been small. Our study has the advantage of being monocentric with two comparable series of patients. The sample size nevertheless remains small and the follow-up short.