Anterior Hip Dislocation: Characterization of a Rare Injury and Predictors of Functional Outcome.

Background: Anterior native hip dislocation remains poorly studied due to the rarity of the injury. The aim of this study was to describe injury characteristics of anterior hip dislocation, detail its initial treatment, and determine the intermediate term outcomes including the rate of conversion to total hip arthroplasty (THA).

Methods: A cross-sectional study was performed at a single urban academic Level 1 trauma center for patients who sustained traumatic anterior hip dislocations from 2010-2017. Baseline demographic, injury, and treatment data were recorded. Patients were contacted to inquire about subsequent surgery and complete functional outcome questionnaires. Available post-operative radiographs were also reviewed.

Results: Thirty-two anterior hip dislocations met inclusion criteria and were included in the study. 69% of dislocations were obturator dislocations and 31% iliac dislocations. Only 22% were simple dislocations with the remainder having an associated femoral head fracture and/or acetabular fracture. Iliac dislocations were more likely to be associated with acetabular fractures and require surgical treatment while obturator dislocations were more likely to be simple dislocations or have femoral head fractures. Excluding two patients treated with acute THA at the time of injury, follow-up information was available for 16 patients at a minimum of eighteen months from the time of injury. Only one required subsequent conversion to THA. For the remaining fifteen patients, modified Harris hip scores (mHHS) averaged 82.6, PROMIS global physical health averaged 51.9, and PROMIS global mental health averaged 48.3 with mean follow-up of 4.2 years. mHHS was significantly higher for obturator dislocations and a negative association was seen with age.

Conclusions: Obturator dislocations occurred twice as frequently as iliac dislocations. Associated acetabular or femoral head fractures are common. Conversion to THA was low, occurring in only 1 of 16 patients not treated with acute arthroplasty. Obturator dislocations and age less than 45 years old at the time of injury were associated with better functional outcome at intermediate term follow-up.