BIOMECHANICAL EVALUATION OF TRANSVERSE ACETABULAR FRACTURE FIXATION

The purpose of this two-part biomechanical study was to evaluate vario us fixation methods for transverse acetabular fractures in a synthetic pelvic model. In Part 1, 40 transverse acetabular fractures were repa ired 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 fixa tion 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 c onsistent with stance phase. Fixation stiffness was measured from the force-displacement curve for each construct. In Part 1, there was no s ignificant difference in fixation stiffness afforded by any of the con structs. However, the stiffest construct resulted from two screws on e ach side of the fracture site: one placed as close to the fracture sit e as allowed (one empty screw hole adjacent to the fracture) and the s econd at the end of the plate. In Part 2, the constructs that concomit antly stabilized anterior and posterior columns were significantly sti ffer than were those addressing either the anterior or posterior colum n alone, regardless of the number of plates applied. The stiffest cons truct 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. Concu rrent fixation of anterior and posterior columns of transverse acetabu lar fractures provides the greatest resistance to postoperative loss o f reduction in this model.