Cite This Article

What is the diagnosis?

Anterior inferior (“obturator”) dislocation of the left hip joint 

• Pearl: Emergently acting on native hip dislocations is paramount given the risk of avascular necrosis (AVN) which is similar to talus dislocations of the foot. 90% of hip dislocations are posteriorly dislocated [1].

What is the mechanism of injury?

For hip dislocations, common mechanisms include high-energy axial trauma or impact to the greater trochanter, or ground-level falls in geriatric patients and those with osteoporosis.

What physical exam findings are expected?

The hip visibly can be noted out of place/misaligned. In posterior hip dislocations, the most common form, you will see the affected limb shortened in slight flexion, adduction and internally rotated. In this case, we discuss the less common anterior inferior hip dislocation where the lower extremity is abducted, slightly flexed and externally rotated without obvious shortening. In anterior superior dislocations the lower extremity appears shortened, externally rotated and extended. The log roll physical exam maneuver with the examiner rotating the patient’s hip internally by turning their foot and then removing pressure to allow the hip to passively rotate externally is used for intra-articular testing of the hip. This is nearly impossible to do in someone with a significantly dislocated hip due to pain and mechanical block to motion. Any form of circumduction of the hip joint will be difficult if not impossible. Vascular and neurologic examinations are frequently normal, however must be assessed. 

• Pearl: Up to 10-20% will have an associated sciatic nerve injury in posterior hip dislocations. [2] The log roll test has been described as one of the most specific tests for hip pathology. [3] 

Which imaging modalities can be used?

In the ED multiple imaging studies can be utilized. An X-ray will show dislocation of the femoral head. Post-reduction films including AP pelvis should be obtained as well.  After reduction, all native hip dislocations warrant CT scan to evaluate for femoral head fractures, loose bodies, and acetabular fractures. If the dislocation is a prosthetic joint, post reduction CT scan is not necessary unless there is concern for fracture or component loosening. 

• Pearl: Initial X-ray evaluation MUST include two views to identify if the hip is anteriorly or posteriorly dislocated. AP of the pelvis and can be supplemented by Judet or lateral femoral views. In an anterior dislocation the femoral head will appear larger on the AP Pelvis view than the contralateral femoral head. The opposite is true for a posterior dislocation. 

Image 2. Post reduction radiographic image of the injured left hip. Author’s own images.

What is the management in the ED?

Initial management includes emergent reduction of the dislocation. This can be performed through various reduction maneuvers (read about here [4]). Reduction can be painful and difficult without muscle relaxation, therefore management with sedation is often recommended. If clinically appropriate, propofol is the preferred drug of choice during reduction to achieve maximum paralysis to counteract the significant muscle mass surrounding the hip joint. 

When do you consult Orthopedics?

Orthopedics should be consulted immediately if unable to reduce the dislocation, and after reduction if an associated fracture or persistent instability is present. If in a location where Orthopedics is not readily available post-reduction and the hip remains unstable, the goal is to minimize the chance the leg is put into a position where the joint is susceptible to re-dislocation. This depends on the type of dislocation. You can immobilize the patient with abduction pillows, a knee immobilizer or a long leg splint to help immobilize the limb. If stable, the patient can be discharged with a knee immobilizer and protected weight bearing for 4-6 weeks with outpatient follow up. Follow-up with Orthopedics as an outpatientis also recommended to monitor for complications, including avascular necrosis of the femoral head, degenerative osteoarthritis, and heterotopic ossification.