Study Guide

Hip Dislocations - Traumatic

Key Points:

Rare and can be associated with low-energy (younger patient) or high-energy injuries (adolescent patient)
Prompt reduction (<6 hours) decreases the risk for avascular necrosis
There should be a high level of suspicion for incongruent reduction, with MRI the preferred study to evaluate
Treatment is directed by the age of the patient
Complications include, but are not limited to: AVN, myositis ossificans, traumatic arthritis, and coxa magna

Description:

A traumatic hip dislocation occurs when, due to an outside force, the femoral head is dissociated from the acetabulum.

Epidemiology:

Traumatic hip dislocations are rare. Approximately, 90-95% of dislocations are posterior.(Herrera-Soto, 2009) There is a male preponderance of 4:1. (Petrie, 2009)

Clinical Findings:

Patients are unable to bear weight on the injured extremity and there is groin or buttock pain. They may have a shortened, flexed, and internally rotated extremity if the dislocation is posterior.(Herrera-Soto 2009) Anterior dislocations present with hip extension and external rotation.(Herrera-Soto 2009) The dislocation may be isolated or may be associated with soft tissue injury, neurovascular injury, acetabular fracture, or femoral head/neck fracture.

Imaging Studies:

Plain radiographs are the initial imaging modality for traumatic hip dislocations. MRI has been shown to be superior to CT for post-reduction assessment if there is asymmetric joint widening, as it can better estimate posterior wall fractures and soft tissue injuries than CT scan. (Mayer 2015, Elder 2004)

Treatment:

Closed reduction of the hip is usually possible under conscious sedation or general anesthesia. Care must be taken to avoid an iatrogenic femoral neck fracture or displacement of a nondisplaced associated femoral neck fracture.

Following closed reduction, imaging with plain radiographs, CT, and/or MRI is important to confirm adequate reduction. Capsule, labral, or osteochondral fragments may become interposed and prohibit a concentric reduction, and one should have a high level of suspicion with a low threshold for advanced imaging.

An open reduction is indicated if the hip is irreducible or if the reduction is not concentric. The surgical exposure should proceed from the direction of the dislocation; posterior dislocations are addressed via the Kocher-Langenbeck approach and anterior dislocations via the Smith Peterson approach. (McCarthy 2015) Alternatively, the surgical hip dislocation approach may be a safe and effective technique for the adolescent patient with residual instability, nonconcentric reduction, or associated femoral head fracture requiring reduction. (Podeszwa 2008, Novais 2015)

There is no consensus on post reduction care. For the younger patient, spica casts for approximately 4-6 weeks can be used to provide immobilization. (Herrera-Soto 2009, Mehlmann 2000) For the older patient, early mobilization with protected weight-bearing is recommended.(Mehlmann 2000) Postoperative hip precautions to prevent redislocation may be considered.

Complications:

Avascular Necrosis
The incidence of AVN ranges from 3-15% and may become apparent radiographically between 2-12 months post-injury.(Herrera-Soto 2009, Mehlmann 2000) Mehlman et al reported a 20-fold increase in AVN in hips that remained dislocated >6 hours.(Mehlmann 2000)

Traumatic Arthritis
Early arthritis may develop in up to 20% of patients with AVN . (Herrera-Soto, 2009)

Heterotopic Ossification
This is a rare complication. Excision of heterotopic bone is required only when symptomatic and after the bone has matured.(Herrera-Soto, 2009)

Coxa Magna
Mehlman reported a 26% rate of coxa magna. It is rarely symptomatic and is believed to be caused by reactive hyperemia.(Mehlmann 2000)

References:

Elder G, Harvey EJ. Surgical images: musculoskeletal. Imaging in musculoskeletal trauma: the value of magnetic resonance imaging for traumatic pediatric hip dislocations. Can J Surg. 2004 Aug;47(4)290-1.
Herrera-Soto JA, Price CT. Traumatic hip dislocations in children and adolescents: pitfalls and complications. J Am Acad Orthop Surg. 2009 Jan;17(1):15-21
Hung NN. Traumatic hip dislocation in children. J Pediatr Orthop Br. 2012 Nov;21(6):542-51.
Mayer SW, Stewart JR, Fadell MF, Kestel L, et al. MRI as a reliable and accurate method for assessment of posterior hip dislocation in children and adolescents without the risk of radiation exposure. Pediatr Radiol. 2015 Mar 24. [Epub ahead of print]
McCarthy J and Noonan K. Fractures and Traumatic Dislocations of the Hip in Children in Beaty JH and Kasser JR, eds. Rockwood and Wilkins’ Fractures in Children. 8^th ed: Philadelphia, PA: Lippincott; 2015: 769-796.
Mehlman CT, Hubbard GW, Crawford AH, Roy DR, Wall EJ. Traumatic hip dislocation in children. Long-term followup of 42 patients. Clin Orthop Relat Res. 2000 Jul;(376):68-79.
Novais EN, Heare TC, Hill MK, Mayer SW. Surgical hip dislocation for the treatment of intra-articular injuries and hip instability following traumatic posterior dislocation in children and adolescents. J Pediatr Orthop. 2015 May 13. [Epub ahead of print]
Petrie SG, Harris MB, Willis RB. Traumatic hip dislocation during childhood. A case report and review of the literature. Am J Orthop. 1996 Sep;25(9):645-9.
Podeszwa DA, Rocha AD, Larson AN, Sucato DJ. Surgical hip dislocation is safe and effective following acute traumatic hip instability in the adolescent. J Pediatr Orthop. 2014 Sept 5. [Epud ahead of print]

Top Contributors:

Michael Paloski M.D.

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