Biomechanical evaluation of fixation of posterior acetabular wall fractures.

Reproducible fractures of the posterior wall of the acetabulum were created in 10 paired hemipelves from fresh human cadavers. Under anterior-to-posterior loading by a Materials Testing System machine, the load to failure of fixation of the acetabular fractures treated with steel pelvic reconstruction plates and steel screws was significantly higher than that of fixation with titanium ribbons and titanium screws. Forces as little as 725 newtons applied directly to the fragment caused fixation failure; even the most secure form of fixation failed when a relatively small force of 2,123 newtons was applied. These results emphasize the importance of appropriate postoperative measures, such as limitation of hip flexion and restricted weightbearing, to minimize the force directed against the posterior wall until the fracture has healed. Secure fixation of fractures of the posterior wall of the acetabulum is critical, since loss of fixation results in instability and joint incongruity, which limit the options for reconstruction.