Hip Dislocations

Hip Dislocations

Luis Felipe López MD1, Carlos Prada MD MHSc2, Brett D. Crist MD FACS3 and Gregory J. Della Rocca MD PhD FACS3

1SunnyBrook Hospital, Division of Orthopaedic Surgery, University of Toronto, Toronto, ON, Canada

2Division of Orthopaedic Surgery, Department of Surgery, McMaster University, Hamilton, ON, Canada

3University of Missouri, Columbia, MO, USA

Clinical scenario

  • A 40‐year‐old male is brought to the Emergency Department after a motor vehicle crash. He was an unrestrained passenger in the front seat.
  • He is complaining of significant pain in the left hip and buttock region. His left extremity is slightly flexed, adducted, and internally rotated, and appears to be his only injury.
  • X‐ray demonstrates a posterior left hip dislocation with a small posterior wall acetabular fracture.
  • After uneventful reduction in the Emergency Department, his hip remains concentrically reduced. Stress examination reveals that the hip is stable through range of motion. Nonoperative management is selected.
  • Due to persistent pain two weeks later, he undergoes magnetic resonance imaging (MRI), and is diagnosed with a labral tear.

Top three questions

  1. In patients with a traumatic dislocation of the hip, does a delay in hip reduction increase the risk of femoral head osteonecrosis (avascular necrosis [AVN]) as compared with an earlier reduction?
  2. In patients with an isolated traumatic hip dislocation, do advanced imaging examinations (computed tomography [CT] and/or MRI) change treatment approach, as compared with X‐rays alone?
  3. In patients with hip dislocations who are diagnosed with an acetabular labral tear after closed reduction, does surgical treatment (with debridement and/or repair) achieve better functional outcomes than nonsurgical management?

Question 1: In patients with a traumatic dislocation of the hip, does a delay in hip reduction increase the risk of femoral head osteonecrosis (avascular necrosis [AVN]) as compared with an earlier reduction?


Clinical comment

Femoral head AVN – an undesirable complication after a traumatic hip dislocation – can lead to significant morbidity.3 It may be caused by disruption and/or kinking of retinacular vessels supplying the femoral head.4 Most surgeons believe that rapid reduction of hip dislocations is important to minimize AVN risk, but this is unproven. Knowledge regarding whether type of dislocation and timing to hip reduction is achieved may have an impact upon development of osteonecrosis and post‐traumatic arthritis can assist orthopedic surgeons when informing hip dislocation patients about their prognosis and offering them the appropriate treatment.

Available literature and quality of the evidence

This search produced the following results: one level III meta‐analysis1 and one level IV systematic review and meta‐analysis.5 Numerous case series and case reports are already included in the previous two articles.


Femoral head osteonecrosis and hip dislocations

Kellam et al. performed a systematic review and meta‐analysis that assessed femoral head osteonecrosis and post‐traumatic osteoarthritis (PTOA) rates after traumatic hip dislocation.5 They included 13 retrospective observational cohort studies (level of evidence: IV) with 795 posterior hip dislocations and 86 anterior hip dislocations, and found that, for both anterior and posterior dislocations, the event rate of AVN and PTOA was higher as the severity of the injury increased. On the other hand, Ahmed et al. conducted a meta‐analysis where they found that time to hip reduction was unimportant, and data pooled from the selected studies showed a trend toward higher femoral head AVN in high‐grade traumatic hip dislocations (Thompson and Epstein grade IV–V) when compared to low‐grade traumatic hip dislocations (Thompson and Epstein grade I–III), but this did not reach statistical significance (odds ratio [OR] = 1.71; 95% confidence interval [CI]: 0.22–13.22; I2 = 68.9%; p = 0.012).1

Time to reduction and AVN

From the 13 studies included by Kellam et al.,5 only two reported data about time to hip reduction. Sahin et al. showed that patients developed AVN after hip dislocation less frequently when reduction was performed within the first 12 hours (1/35, 2.9%), as compared to later than 12 hours (4/27, 14.8%) after the injury.6 However, when comparing traumatic hip dislocations reduced in <6 hours and those reduced between 6 and 12 hours from the injury, they did not find any difference in AVN rates. Brav et al. reported AVN in 3/204 (1.47%) versus 33/58 (56.9%) cases when comparing patients who underwent articular reduction within or after 12 hours, respectively.7 Although the number of studies reporting on timing was small, Kellam et al. calculated an increased risk (OR = 5.63; 95%CI: 2.97–10.67; p <0.005) for development of AVN for all types of hip dislocations when reduction is performed after 12 hours.5

Ahmed et al. considered a different timeframe in their study. They compared femoral head AVN rates when hip reduction was done early (considered to be <6 hours from the time of injury) versus late (>6 hours).1 They included five studies (all retrospective cohort studies) encompassing 236 traumatic hip dislocations. Patients who underwent late hip reduction had a significantly higher risk of femoral head AVN (OR = 5.00; 95% CI: 1.30–19.29; I2 = 48.6%), as compared to those who had an early reduction. Dreinhöfer et al., in a cohort of 50 patients who underwent hip reduction after a traumatic hip dislocation, found an overall femoral head AVN rate of 12%, but found no difference in the rates between patients who underwent reduction within one hour compared to between one and six hours after injury.8

Resolution of clinical scenario

In this clinical scenario, considering the best available evidence, the orthopedic surgeon should be prepared to perform a reduction of a dislocated hip within six hours from injury. However, as evidence associating femoral head AVN with time to reduction of a hip dislocation is moderate, the recommendation remains to perform reduction as soon as possible in order to avoid further articular damage and, possibly, femoral head AVN (overall quality: moderate).

Question 2: In patients with an isolated traumatic hip dislocation, do advanced imaging examinations (computed tomography [CT] and/or MRI) change treatment approach, as compared with X‐rays alone?


  • Hip dislocations are normally diagnosed with orthogonal plane x‐rays. Traditionally, after closed reduction is achieved, CT scans have been the imaging technique of choice to assess for associated fractures and/or intra‐articular fragments.
  • Controversy exists about the best imaging modality for evaluation of patients after closed reduction of hip dislocations, due to concern for associated soft tissue injuries and/or intra‐articular fragments that may be missed by CT scan.9

Clinical comment

Arthroscopy has emerged as an important therapeutic tool after traumatic hip dislocation to treat some patients with persistent pain or mechanical symptoms associated with intra‐articular loose bodies or other injuries, such as labral tears. Arthroscopy has been used as the gold standard when comparing the accuracy of different imaging techniques for the identification of intra‐articular pathology.

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Nov 28, 2021 | Posted by in ORTHOPEDIC | Comments Off on Hip Dislocations
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