Cadaveric femoral fractures in a fall on the hip configuration

We fractured 100 cadaveric femora with different areal bone mineral density (aBMD) (normal, osteopenic, and osteoporotic) in a fall on the hip loading configuration using a mechanical testing system. Two single-axis and one multi-axis load cells measured the forces and moments in the femoral head, shaft, and the greater trochanter. Two high-speed video cameras recorded the events leading to fracture from the anterior and posterior directions. Force-displacement curve of a typical experiment showed a linear elastic region followed by post-yielding associated with sinking of the superior neck region into greater trochanter (73 of the tested femora). Fatal crack initiated in tension on the inferior region of the neck or medial shaft. Femoral strength (peak trochanteric force) exhibited strong correlation with aBMD. One-way analysis of variance showed significantly lower values for means of fracture forces and moments of osteoporotic femora compared to those of osteopenic and normal femora. Fracture forces showed very weak correlation with the femoral geometric parameters measured from CT scans. Using post-fracture CT scans and with the help of an orthopedist, the femoral fractures were classified into subcapital, transcervical, intertrochanteric and pertrochanteric. Oneway analysis of variance indicated that femora with intertrocanteric fracture had significantly lower neck aBMD than femora with pertrochanteric and transcervical fractures.