Stability of fixation in femoral neck fractures: Comparison of four fixation devices in vivo and in cadavers

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Abstract
On human cadaveric femora, internal fixation of cervical osteotomies was performed with four different devices. With the use of a lever, a static force was applied through the acetabulum to the osteotomy site. Motion at the osteotomy site was measured by two strain gauges. The compression force necessary to inhibit motion at the osteotomy site during the fixation procedure was measured. This force was lower with a hook pin than with the other devices. During surgery in 12 patients with displaced femoral neck fractures, the forces holding the fracture surfaces together were measured with a dynamometer. The force at which widening of the fracture gap was observed by fluoroscopy was recorded. In seven fractures, the mean compression force was 110 (60–170) N. The remaining five fractures did not open up when pressures of up to 200 N were applied. These forces were always greater than the hook pin forces measured in the cadaver experiments, but often less than the forces obtained with the other devices.