Objective To introduce a new technique of navigated femoral nailing using noninvasive registration of the contralateral femur to control reduction and intramedullary nailing of femoral shaft fracture and discuss preliminary clinical results. Methods A new navigation module was employed to control femoral fracture, rotation and fixate femoral fraeture based on anteversion of the contralateral femur. In order to measure the femoral antcversion of the healthy femur intraoperatively, a non-invasive registration tech-nique was used. After minimal invasive reference arrays were fixed on the fraeture side, images of the frac-ture side were mandatory for femoral antevrsion measurements. Closed reduction and nailing was performed under computer navigation according to data of the contralteral side of the femur. Postoperative CT scanning on bilateral femur was done to observe specific anteversion and compare with intraoperative results of naviga-tion system. Results A total of 14 patients with femoral fractures obtained successful fixation and reduc-tion, with no intraoperative or postoperative complications. Postoperative CT scans were acordant with the intraoperative navigated measurements, with anteversion deviation within 3° between both sides. Conclu-sions Navigated femoral nailing using nnninvasive registration of the contralateral femur to control fracture fixation and reduction can help control anteversion measurements of the fracture site and reduce the inci-dence of femoral malrotation after closed reduction and intramedullary nailing.

Results: Propensity matching led to two groups of 89 patients each. The UIV, pelvic incidence minus lumbar lordosis, sagittal vertical axis, pelvic tilt, age, and body mass index were similar in both groups (p >0.05). The incidence of PJK at postoperative one year was similar for SE (30.3%) and LF (22.5%) groups (p =0.207). The PJK angle was comparable (p =0.963) with a change of −8.2° (SE) and −8.3° (LF) from the preoperative measures (p =0.954). A higher rate of PJK after SE (p =0.026) was found only in the subgroup of patients with UIV levels between T9 and T12. Conclusions Instrumentation to the sacrum with or without iliac extension did not increase the overall risk of PJK. However, an increased risk for PJK was found after SE with UIV levels between T9 and T12.