Stability of acetabular fractures after internal fixation. A cadaveric study.

The rigidity of a transverse acetabular fracture in a laboratory cadaveric model immobilized by internal fixation was studied. On the application of a longitudinal load imposed on the fifth lumbar vertebra, four modes of displacement of the acetabular fracture were monitored by the use of variable impedance transducers. The rigidity of various combinations of lag screws and plates was assessed. The fracture deformations documented were generally quite small at any observation point with any of the fixation methods, and in most cases they were recoverable on load release. Anterior column lag screw fixation combined with plate fixation of the posterior column provided a degree of stability indistinguishable from that of other methods, and allowed the minimal exposure and devascularization of the pelvis. The 3.5 mm reconstruction plate, which is readily contoured to the intricate peri-acetabular bony structure, showed no significant difference in rigidity compared to the other apparently more rigid plates under study.