Effect of high tibial osteotomy on hip biomechanics in patients with genu varum: A prospective cohort study

BACKGROUND AND AIMS The aim of this study is to evaluate the effect of proximal tibia osteotomy on hip biomechanics. METHODS This cohort study was conducted on 50 knees of 37 patients divided into two groups of unilateral and bilateral surgeries during 2015-2016. Patients underwent medial open-wedge osteotomy of proximal tibia. Axial alignment of lower limb radiography was carried out for the patients before and after the osteotomy. RESULTS Findings from unilateral and bilateral high tibial osteotomies demonstrated that the average of greater trochanter (GT) angle from femoral head center and also the average angle of knee varus were significantly decreased (P = 0.001). Although not statistically significant, the average angle of the mechanical axis of lower limb showed an increase in unilateral osteotomy (P = 0.889) and a decrease in bilateral osteotomy (P = 0.887). The average angle of pelvic obliquity after unilateral osteotomy increased significantly (P = 0.001) but showed no statistically significant difference in bilateral osteotomy (P = 0.631). CONCLUSION High tibial osteotomy significantly affects the GT and causes the downward replacement of GT and consequent shortening of the abductors moment arm, increased hip joint reaction force, and reduction of the shear force on the femoral neck.