ACETABULAM TRAUMA An acetabular fracture is a break in the socket portion of the “ball-and-socket” hip joint. These hip socket fractures are not common — they occur much less frequently than fractures of the upper femur or femoral head (the “ball” portion of the joint). The majority of acetabular fractures are caused by some type of high-energy event, such as a car collision. Many times patients will have additional injuries that require immediate treatment.