What is your diagnosis?

Posterosuperior prosthetic hip dislocation. 

• Pearl: In native joints posterosuperior hip dislocations are the most common (~90%) with anterior dislocations being much less common [1]. These trends are similar in total hip arthroplasties (THA) especially due to the common posterior approach breaching the posterior soft-tissue stabilizers. 

• Pearl: Periprosthetic hip fractures can also occur with or without dislocations and can be easily missed if there is an obvious dislocation distracting you!

What are potential complications of this injury?

In native hips, common complications of hip dislocations include avascular necrosis of the femoral head, post-traumatic arthritis, sciatic nerve injury. In a prosthetic hip, the major complication is a sciatic nerve injury, which occurs in approximately 10% of cases [1]. 

• Pearl: In native hips, the time from dislocation to reduction is critical as the risk for avascular necrosis of the femoral head increases significantly after 6 hours of dislocation [2].

• Pearl: The sciatic nerve has many functions but can be tested quickly by assessing the sensation of the lateral lower leg and the sole of the foot and/or by checking the extensor hallucis longus muscle (EHL) by asking the patient to extend their great toe against resistance.

What is your management in the ED? Does orthopedics need to be consulted?

Management in the ED includes expedited reduction with neurovascular status checked before and after. There are numerous techniques for reduction but all will require some form of moderate sedation to facilitate maximal relaxation of the large, strong muscles of the pelvis to optimize chance of successful reduction. 

All reduction techniques for a posterior dislocation focus on flexion at the hip and in-line traction. There are several described techniques; a great review article describing them is listed below. Generally speaking, 1-2 attempts with each method is enough to determine whether it will work, and subsequent attempts using the same method are discouraged. 

For an uncomplicated native hip dislocation that is successfully reduced, orthopedics does not need to be consulted in the ED. For a prosthetic hip dislocation with successful reduction, they also don’t NEED to be consulted, but this is highly dependent on institutional policies. If the hip was operated on by a surgeon at your facility, they typically want to be involved in the case. All cases should be referred to orthopedics for outpatient follow-up. 

• Pearl: For an in-depth review of many of the described hip reduction techniques (including photos), see: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4821229/ [3]