CONSEQUENCES OF TRANSVERSE ACETABULAR FRACTURE MALREDUCTION ON LOAD TRANSMISSION ACROSS THE HIP-JOINT

Objective: To evaluate the biomechanical behavior of gap and step malr eductions in a model of transverse acetabular fracture. Design: Cadave r pelvis loading in simulated single-leg stance with intact acetabulum , after transverse acetabular fracture anatomically reduced, and after step and gap malreduction. Five transtectal transverse fractures; fiv e juxtatectal transverse fractures. Setting: Quasi-static loading of t he hip with simulated abductor mechanism to physiologic loads with pre ssure-sensitive film interposed in the joint to determine contact area and contact pressure within the hip joint. Main Outcome Measurement: Hip joint contact parameters: contact area, peak and mean contact pres sure, and load distribution. Results: Step malreduction of the transte ctal transverse fracture resulted in significantly increased peak cont act pressures (20.5 megapascals) in the superior acetabular articular surface as opposed to the intact acetabulum (9.1 megapascals). Gap mal reduction of transtectal transverse fracture and step and gap malreduc tion of juxtatectal fracture did not result in significantly increased contact pressures in the hip. Conclusion: Step malreduction of a tran sverse acetabular fracture in the superior articular surface results i n abnormally high contact forces and may predispose to the development of posttraumatic arthritis.