Rotational strength of the femoral neck. Computed tomography in cadavers

The mean bone density of the femur at different levels was determined by means of quantitative computed tomography (QCT) in 50 pairs of normal cadaveric femora and related to the rotational strength of the femoral neck. All the femora fractured vertically and spirally in the neck. The bone-mass-related measures at different levels were calculated from QCT densities and volumes. Cancellous bone was defined with threshold limits ranging from 50-500 Hounsfield units (HU), and attenuation values exceeding 500 HU were assessed as cortical bone. The recorded QCT mass-related measures of cortical and cancellous bone separately and as total bone masses gave significant right/left correlations. Correlations were found between the ultimate torsional strength of the femoral neck and QCT recordings of bone mass at all the femoral levels. The best correlations were demonstrated between the rotational strength of the femoral neck and the total bone-mass-related measures in the femoral shaft and condylar area. Bone mass of the femur measured by computed tomography may become useful as an index of the mechanical strength of the femoral neck.