Purpose This study aimed to verify if the navigation system used in high tibial osteotomy (HTO) adds precision to the procedure regarding mechanical axis correction and prevention of tibial slope increases. Methods In this historically controlled study, patients with medial osteoarthrosis and genuvarum underwent HTO between 2004 and 2012; the first 20 were operated with the conventional technique, using pre-planning correction by the Dugdale method and 18 further patients were operated with the navigation system introduced in our hospital. Results The two groups were similar for pre-operative mechanical axis (mean 8.10±3.14 for the control and 6.60± 2.50 for the navigated group), pre-operative tibial slope (mean 8.95±3.47 versus 8.17±3.11, respectively) and Lyshom score (40.85±15.46 and 44.83±16.86). After surgery, the control group presented mean mechanical axis of 3.35±3.27, tibial slope of 13.75±3.75 and Lyshom score of 87.60±11.12. The navigated group showed a postoperative mechanical axis mean of 3.06±1.70, tibial slope of 10.11±0.18 and Lyshom score of 91.94±11.61. Conclusions The navigation system allowed a significantly better control of tibial slope. Patients operated with the navigation system had significantly better Lysholm scores.

There was a significant difference in the calculation of the wedge opening between the DM and NS. HTO without the aid of the NS could theoretically lead to undercorrection of the deformity.

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