Reliability of limb alignment measurement for high tibial osteotomy with a navigation system.

OBJECTIVE: High tibial osteotomy (HTO) is one treatment option for young and active patients with unicompartmental osteoarthritis. The success of this procedure substantially depends on the degree of correction of the mechanical axis. Computer-assisted navigation systems are believed to improve the precision of axis correction through intraoperative real-time monitoring. This study investigates the accuracy of limb alignment measurements with a navigation system on a cadaver specimen.
MATERIALS AND METHODS: The measurements were performed on a well-preserved cadaver specimen with a mechanical leg axis of 4 degrees varus. Data was collected during the HTO workflow. Repeated serial measurements were undertaken by four different surgeons. After these measurements, different landmarks were deliberately set at the wrong place to examine the influence of mistakes during registration.
RESULTS: There was a high intra- and interobserver reliability with a mean mechanical leg axis of 3.9 degrees +/- 0.7 degrees and a mean error of 0.6 degrees. The grossly incorrect placement of landmarks for knee and ankle center resulted in an incorrect mechanical leg axis of 1 degrees valgus up to 10 degrees varus.
CONCLUSION: The computer-assisted navigation system provided precise information about the mechanical leg axis, irrespective of the observer's experience.