Hip Dislocation
What is it: A displacement of the femoral head from the acetabulum. Posterior dislocations are far more common than anterior dislocations (>90%), but both types are rare due to the presence of a strong joint capsule and deep acetabulum. Hip dislocations are typically caused by high-energy trauma.
How does it present: Patients report severe hip pain with an inability to move the lower extremity. Common exam findings: With posterior dislocations, the affected limb is shortened and the hip is flexed, adducted and internally rotated. With anterior dislocations, the hip is mildly flexed, abducted and externally rotated. A thorough neurovascular exam should be documented.
Tests and treatment: Anteroposterior (AP) views of the pelvis with AP and lateral views of the femur should be ordered. With a posterior dislocation, the affected femoral head appears posteriolaterally displaced and smaller than the contralateral femoral head. Repeat radiographs should be obtained following reduction of the dislocation and CT scan may be helpful to ensure a completely concentric reduction without interposition of bony fragments. An associated fracture of the ipsilateral femur or acetabulum may present concurrently and CT scan may be helpful at fully defining the fracture pattern. Hip reduction should be performed as soon as possible to decrease the risk of ostoenecrosis, but fracture should be ruled out before this procedure is executed. Post-reduction treatment consists of early crutch-assisted ambulation with weight bearing as tolerated until pain free, typically two to four weeks. Afterwards, patients begin physical therapy using a walking aid until able to walk without a limp. Associated acetabular or femoral fractures are typically corrected with surgical repair.