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What is the diagnosis?

Initial plain films demonstrate a right sided inferior hip dislocation. Additionally, there is also poor positioning of the left femoral head and irregularity of the left acetabulum with concern for fracture given mechanism. CT scan confirms a comminuted fracture of the roof and posterior aspect of the left acetabulum. 

Image 2 (a & b): a (left). X-ray of the AP pelvis demonstrating an antero-inferior right sided hip dislocation (yellow arrow) and concern for possible left sided acetabular lucency suggesting fracture (red arrow). Author’s own images. b (right). Axial slice of a CT abdomen and pelvis demonstrating an acetabular fracture involving the anterior column with mild displacement (red arrow) and posterior column with moderate displacement (yellow arrow). Author’s own images. 

What is the mechanism of injury?

In young patients, inferior hip dislocations and acetabular fractures are typically associated with a high impact mechanism such as falls from height or more often, motor vehicle collisions as in this patient [1]. 

What physical exam findings are expected?

Inferior hip dislocations typically present with the affected hip in flexion, abduction, and mild external rotation [2]. Acetabular fractures may present with a shortened lower extremity in addition to associated hip tenderness. 

What imaging modalities can be used?

X-rays are primary for assessing bony pelvic and hip injuries/dislocations. For simple hip dislocations (dislocation without acetabular or femoral neck fracture), pre- and post-reduction X-rays suffice. Judet views may help identify acetabular fractures. CT scans are necessary if concomitant fractures or multi-organ injuries are suspected based on the mechanism of injury. 

• Pearl: Some studies recommend post-reduction CT scans as up to 60% of posterior hip dislocations have associated acetabular fractures with chondral and osteochondral fragments retained in the joint leading to subtle subluxation not easily identified on plain films alone [3].

What is the management in the ED/when should you consult orthopedics?

Initial assessment should rule out emergent findings to include unstable pelvic fractures requiring immediate operative repair or embolization given high risk of blood accumulation/loss (i.e pelvic ring, open book fractures). Attention to other traumatic injuries is important because inferior hip dislocations are often a result of high energy trauma.

All hip dislocations should be ideally reduced within 6 hours to prevent avascular necrosis of the hip [2].

• Pearl: Studies have shown that delay in reduction after 12 hours can lead to up to 5.6x the rate of AVN in native hips [4]. 

Similar to other hip dislocation reduction techniques, gentle constant traction should be applied in line with the femur while the patient is appropriately relaxed. Some degree of external rotation and abduction was used here to help facilitate the reduction. 

Isolated hip dislocations without evidence of fracture or major neurovascular injury may be discharged with outpatient orthopedic surgery follow up. 

All acetabular fractures require orthopedic surgery consultation and admission to the hospital for assessment of hip stability and consideration of operative repair.

Image 3: Post-intervention X-ray of the AP pelvis s/p hip dislocation-reduction. Image better demonstrates concern for multiple acetabular fractures (red arrows). Author’s own images.