Biomechanical evaluation of transverse acetabular fracture fixation

The purpose of this two-part biomechanical study was to evaluate various fixation methods for transverse acetabular fractures in a synthetic pelvic model. In Part 1, 40 transverse acetabular fractures were repaired with anterior column plating using 10-hole curved reconstruction plates with one of four screw configurations to evaluate the effect of screw placement and number on fracture fixation stiffness. In Part 2, 36 transverse acetabular fractures were repaired with one of six fixation methods using combinations of contoured plates and column screws to stabilize the anterior column, the posterior column, or both. Each repaired acetabulum was loaded via a hemiarthroplasty in a direction consistent with stance phase. Fixation stiffness was measured from the force-displacement curve for each construct. In Part 1, there was no significant difference in fixation stiffness afforded by any of the constructs. However, the stiffest construct resulted from two screws on each side of the fracture site: one placed as close to the fracture site as allowed (one empty screw hole adjacent to the fracture) and the second at the end of the plate. In Part 2, the constructs that concomitantly stabilized anterior and posterior columns were significantly stiffer than were those addressing either the anterior or posterior column alone, regardless of the number of plates applied. The stiffest construct combined a posterior column plate with an anterior column screw. Because no significant change in stiffness occurred with the addition of a third set of screws, two screws on each side of the fracture site appear to provide sufficient stability with acetabular plating. Concurrent fixation of anterior and posterior columns of transverse acetabular fractures provides the greatest resistance to postoperative loss of reduction in this model.