Hip (posterior dislocation)

About 90% of hip dislocations are posterior.

This type of injury will often occur in a road accident. In this situation the patient may have been seated in a car and been thrown forward hitting their knee against the dashboard and forcing the femoral head upwards and backwards dislocating the hip joint posteriorly. This type of injury may cause a concomitant fracture of the acetabulum and so be a fracture-dislocation of the hip joint.

Posterior hip dislocation is rarely, if ever, an occult injury due to the amount of pain elicited as well as an inability to ambulate or bear weight on the affected extremity afterward. The patient's history will usually involve a description/experience in which there was a significant "clunk" or "popping" followed immediately by pain.

Time to reduction is crucial because the longer the hip is dislocated, the higher the risk of complications, specifically avascular necrosis in the native hip. Most authors recommend a reduction time of fewer than 6 hours, while there is some evidence that fewer than 12 hours may be a critical time; regardless, the rate of secondary complications increases dramatically with increased time-to-reduction. (2)

Reference

1. Dawson-Amoah K, Raszewski J, Duplantier N, Waddell BS. Dislocation of the Hip: A Review of Types, Causes, and Treatment. Ochsner J. 2018 Fall;18(3):242-252
2. Soong M, Rubash HE, Macaulay W. Dislocation after total hip arthroplasty. J Am Acad Orthop Surg. 2004 Sep-Oct;12(5):314-21