Pipkin classification of posterior dislocation of hip with femoral head fracture. A, Type I: femoral head fracture caudal to fovea capitis. B, Type II: femoral head fracture cephalad to fovea capitis. C, Type III: type I or II fracture with associated femoral neck fracture. D, Type IV: type I, II, or III fracture with associated acetabular fracture.