Propensity for Hip Dislocation in Gait Loading Versus Sit-to-Stand Maneuvers: Implications for Surgical Management of Acetabular Fractures

Acetabular fractures present a clinical challenge due to the complicated anatomy and difficulty of exposure, reduction, and fixation. There are several indications for surgery including any fracture which is displaced more than 2mm, failure to maintain reduction by closed means, or, for transverse fractures, a roof-arc angle less than 45 degrees (1,2). The last indication was determined by a cadaver model that only evaluated hip stability in the single leg stance phase of the gait cycle (3). Kinesiological models have well established that the magnitude and direction of the joint contact force can deviate substantially from the mechanics of gait loading, particularly for such activities of daily living as sit-to-stand maneuvers and climbing stairs (4,5). Thus, the criteria for fracture stability established using gait-only loading conditions may be inadequate for other activities of daily living. Basic engineering principles would dictate that the most conservative estimate of dislocation potential be used in managing these cases clinically; and it is therefore important to re-evaluate fracture management criteria in alternative loading conditions that have a high potential for dislocation.