ORTHOPAEDIC SURGERY Reliability of computer-assisted surgery as an intraoperative ruler in navigated high tibial osteotomy

Background Computer-assisted surgery (CAS) can act as an intraoperative ruler in high tibial osteotomy (HTO) to visualize continuously the leg during surgery. Questions The aim of the study is to evaluate the accuracy of CAS with respect to preoperative planning and postoper-ative deviation from the planned leg axis in HTO. In addition, the influence of surgeon experience as well as operation time and perioperative complications are analyzed. Methods A prospective multicenter study case series with follow-up at 6 weeks was performed in six centers. Medial open-wedge HTO with Tomofix was done using com-puter assisted navigation technique with the Brainlab VV Osteotomy 1.0 module. Results Fifty-one patients with medial gonarthritis were treated with navigated HTO. The follow-up rate was 98%. The majority of HTO–CAS patients fell within the tolerated limit of ±3 for leg axis deviation, however, seven patients were reported with deviations outside of this range: three patients had deviations of[3–4.5 and four patients[4.5, respectively. Eight intraoperative complications were doc-umented, partially resulting from technical problems asso-ciated with the navigation system. During the 6-week follow-up period, three postoperative complications were experienced, all not associated with navigation technology. Conclusions In about 85 % of cases, a perfect result in terms of deviation of the planned mechanical leg axis could be achieved. Computer assistance in HTO proved to be a helpful tool regarding intraoperative control of leg axis. Level of evidence Level I, High quality prospective study (all patients were enrolled at the same preoperative plan-ning point with C80 % follow-up of enrolled patients)