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Hip Dislocation: Differential Diagnoses & Workup

Author: Matthew Gammons, MD, Assistant Clinical Professor, Department of Family and Community Medicine, Medical College of Wisconsin; Medical Director, Castleton State College; Consulting Staff, Vermont Orthopaedic Clinic and Killington Medical Clinic
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Updated: Jan 30, 2009

Differential Diagnoses

Other Problems to Be Considered

Femoral head chondral injury or chondrolysis
Femoral neck stress fracture
Labral tear
Rupture of the proximal insertion of the hamstring muscles
Slipped capital femoral epiphysis

Workup

Laboratory Studies

• Laboratory studies should be based on the individual patient, mechanism of injury, and concern about other injuries.
• Hemoglobin/hematocrit: Evaluate the amount of blood loss if a patient has any significant trauma to the hip or if vessel injury is suspected. Observation of serial hemoglobin/hematocrit is important in case of disruption or intimal tear of the femoral vessels.

Imaging Studies

• Radiographs (anteroposterior [AP], lateral, and internal and external oblique views)
  • A full series of prereduction radiographs should be obtained expeditiously, including the AP pelvis view, which shows most hip dislocations and provides evidence for the type of dislocation. Include other views, such as a cross-table lateral, and Judet (oblique) views. Exceptions would include expedient on-field reduction and not having timely access to a facility with radiographic capability, such as backcountry skiing/snowboarding areas.
  • In the AP pelvis view, the femoral head will appear small when compared with the uninjured side in a posterior dislocation and large in an anterior dislocation.
  • Evaluate where the femoral head lies in comparison to the acetabulum (eg, anterior vs posterior, superior vs inferior), if surgery is required to reduce the joint.
  • Lateral and oblique views are very important to evaluate for fractures of the femoral head, neck, and acetabulum.
  • Two oblique views are taken.
    • The first oblique view is taken with the patient placed on the injured side and angled anteriorly approximately 15°.
    • The second view is taken with the patient supine and angled upward about 60°.
  • A full series of postreduction films must be obtained to assess the adequacy of the reduction maneuver.
  • Although loose bony fragments or fractures may be difficult to see on a post-reduction x-ray, evaluating the hip joint for these fragments and fractures is imperative, as they may prevent complete reduction and cause further postreduction damage to the joint.
• Computed tomography (CT) scanning
  • Indications for CT scanning of hip dislocations are debatable, although the fact that failure of closed reduction indicates a CT scan or an asymmetric joint space is widely agreed, as discussed below. CT scanning is helpful to the physician for diagnosing loose bodies and fragments that impede closed reduction and to evaluate acetabular fractures as well.
  • Bony fragments or damaged soft tissues that prevent closed reduction may be present, and the patient would need to be taken to the operating room for open reduction.
  • The presence of postreduction joint-space widening is a second widely accepted indication for a CT scan. This finding may also be evidence for bony fragment involvement that cannot be seen on x-ray or soft-tissue damage that prevents normal articulation.
  • Most physicians recommend obtaining a CT scan of the hip in every patient after closed reduction to evaluate for occult fractures and soft-tissue damage.
• Magnetic resonance imaging (MRI)
  • MRI is indicated subacutely in certain cases of acute hip dislocations to evaluate labral tears, chondral injuries and cartilaginous loose bodies, particularly in the elite athlete and other patients who are likely to sustain high stresses to the hip, and in whom surgical repair of labrum and capsular ligaments would be considered.
  • MRIs should be done in 4-6 weeks to look for signs of osteonecrosis. This is repeated at about 3 months.

Procedures

• Closed reduction
  • Numerous studies have shown that closed reduction should be attempted as soon as possible after a hip dislocation and certainly within the first 6 hours after injury to minimize long-term joint damage.^6,12,13 These techniques should be performed using conscious sedation in the emergency department or under general or spinal anesthesia in the operating room. All of the methods are 2-person closed reduction.
  • The following 3 methods of closed reduction of a dislocated hip exist:
    • The Allis maneuver, the most widely performed method, involves having an assistant bilaterally stabilize the anterior superior iliac spines while the patient is supine. First, the knee of the affected side is flexed, and then the hip is flexed, with traction being placed below the knee pulling upward. The leg is internally and externally rotated until the femoral head is rearticulated with the acetabulum.
    • The Stimson maneuver places the patient in the prone position and is the least traumatic of the closed reduction methods. An assistant provides pressure on the patient's lower back for stability, while the injured leg is allowed to hang from the side of the bed with the knee and hip fully flexed. Traction is applied along with the force of gravity behind the knee, while internal and external rotation is applied to pop the femoral head back into place. Note: This technique is contraindicated in the setting of thoracoabdominal trauma or a difficult airway.
    • The Bigelow maneuver is the final method of closed reduction. As in the Allis maneuver, an assistant applies pressure to the anterior spines of the patient's pelvis for stability. One hand is used to apply traction on the affected leg by pulling on the ankle, while the other forearm is placed under the knee. The knee and hip are flexed on the injured leg, and abduction, external rotation, and extension of the hip are performed until the femoral head is in the acetabulum.
  • Reports of on-field reduction of posterior hip dislocations exist.^6,8 Although this leads to expedient reduction and may theoretically decrease complication rates from the reduction, caution should be used. Only those with experience in hip reductions should even consider attempting an on-field reduction. However, early reduction within the first 5-10 minutes can often be much easier before the onset of muscle spasm. Also consider early out-of-hospital reduction, if significant transport time will occur, such as in wilderness or backcountry situations.

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