Computer-based periaxial rotation measurement for aligning fractured femur fragments from CT: a feasibility study

A new computer-based method for measuring periaxial rotation of healthy and fractured femurs from preoperative CT during closed femoral fracture reduction surgery is described. The method provides a comparative quantitative measure to align the distal and proximal femur fragments based on periaxial rotation. The periaxial rotation is defined in terms of patient-specific bone features. An algorithm for automatically extracting these features from the CT based on this definition has been developed. The algorithm extracts the condyle landmarks and neck axis of the healthy bone, determines its periaxial rotation, and extrapolates this data, assuming mirror symmetry between the healthy and fractured bones, to measure periaxial rotation between the fractured fragments. Unlike existing techniques, the method requires minimal user intervention. In a feasibility study, the method was applied to five dry femurs and one patient data set, and simulated a reduction based on the periaxial measurements with satisfactory results. The experiments showed the measured angle on the fractured femur to be within 1-4.5 degrees of that of the healthy bone.