COMMINUTED FRACTURES OF THE POSTERIOR WALL OF THE ACETABULUM - A BIOMECHANICAL EVALUATION OF FIXATION METHODS

Reproducible simple fractures and osteotomies of the posterior wall of the acetabulum were created in twenty paired hemipelves from fresh hu man cadavera. Comminution was created with an additional fracture line that was either parallel (concentric comminution) or perpendicular (t ransverse comminution) to the posterior rim of the acetabulum. Under s imulated weight-bearing, the stiffness of fixation of the transversely comminuted fractures that had been achieved with use of a reconstruct ion plate and screws was significantly higher than that achieved with fixation with screws alone (p < 0.05). The load to failure of the fixa tion of transversely comminuted fractures treated with a reconstructio n plate and screws was also significantly higher than that of fixation of such fractures with screws alone (p = 0.05). The load to failure o f the fixation of concentrically comminuted fractures was significantl y higher when a reconstruction plate and accessory spring plates had b een used than when a reconstruction plate alone had been employed (p < 0.05). CLINICAL RELEVANCE: Secure fixation of fractures of the poster ior wall of the acetabulum is critical since loss of fixation results in chronic instability and limited options for reconstruction. The dat a from the present study support our clinical observations that, for t ransversely comminuted fractures, fixation with a buttress plate is st ronger than fixation with screws alone and that supplementary fixation with spring plates mag help to prevent redisplacement of concentrical ly comminuted fractures of the posterior wall of the acetabulum.