Purpose: Fracture-posterior dislocation of the femoral head is an exceptional hip injury. Emergency reduction is required. Relocation into the acetabular cavity of the displaced femoral head may not be feasible. Irreducibility, instability, and more rarely accidental fracture of the femoral neck may also occur. We encountered this latter complication in four patients and report here its frequency and mechanism and propose preventive therapeutic measures.

Material and methods: Seventy dislocations and fracture-dislocations of the hip were treated in our unit from March 1997 to February 2003. Among these cases, fourteen hip dislocations were complicated by femoral head fractures. Fracture of the femoral neck occurred during reduction in four. All four cases occurred in men, mean age 49.7 years, who were traffic accident victims (drivers or passengers). There were two Pipkin IV fracture-dislocations and two Pipkin II. The first reduction, achieved under general anaesthesia in an emergency setting, was performed by an orthopaedic surgeon in one patient and a general surgeon in three patients. Arthroplasty was used to treat the femoral neck fracture in three patients and pinning in one. We reviewed retrospectively the clinical and imaging data before and after reduction.

Results: Sub-capital fracture situated 4.0 cm (mean, range 3.5–4.5 cm) from the lesser trochanter occurred in all four cases. The head remained attached above and posteriorly to the acetabulum and was rotated less than 90°. The fragment remaining in the acetabulum was displaced in two cases. In one patient, the fracture-dislocation of the head was associated with a fracture of the posterior rim of the acetabulum.

Discussion: Neck fracture during reduction of traumatic hip dislocation is a serious complication. Prevention of this iatrogenic event requires a slow, progressive reduction limiting the trauma to a minimum; first intention open surgery may be required in selected cases.