Season 10 Case 05

History: trauma, MVA

Season 10 Case 05

History: Trauma, MVA


So the right hip is obviously not normal right? The femoral head is not within the acetabulum. But where is it?

Answer:

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Answer: Obturator (aka inferior) dislocation of the right hip

Hip dislocations are not super common, comprising ~5% of all dislocations.

Causes:

  • high energy trauma (Motor vehicle accident)
  • fall
  • sports injury
  • Congenital (as part of developmental hip dysplasia relating to a shallow acetabular cup)
  • Hip arthroplasty dislocations

Types:

Posterior Hip dislocation
* Most common (~85%)
* Commonly caused by MVA = classic dashboard injury where the sitting patient slides forward, femur hits the dashboard dislocating the femoral head posterior in relation to the acetabulum
* Commonly associated with posterior wall or column acetabular fractures
* Leg commonly presents shortened, in internal rotation and ADducted

Anterior Hip dislocation
* Uncommon
* Leg commonly presents in external rotation and ABducted
* Types:
* Inferior (obturator) - femoral head moves inferior and medial, locking into the obturator canal
* Superior (pubic or iliac) where the femoral head moves anterior and cranial, resting in the iliac fossa) - Extremely uncommon (ie pretty much only in case reports)

Central Hip dislocation
* This is actually a fracture-dislocation
* Always associated with displaced medial acetabular wall fracture and the femoral head moves INTO the pelvix through the fractured wall

Treatment:

  1. Prompt relocation - prolonged dislocation can lead to femoral head AVN
    if you want to see all the techniques, try here
  2. Assessment for fractures and loose intraarticular fracture fragments. Although you can compare joint spaces on a post-reduction X-ray (if affected hip is wider than the normal hip, think loose fragments in the joint space), ideally CT is far better to see smaller fragments as well as better to evaluate for wall/column fractures in addition to any other fractures that may be present

Complications:

  • delayed reduction can lead to avascular necrosis of the femoral head
  • Hip reductions can be difficult. Beware of causing/worsening a fracture while performing it such as unfortunately see here: