Traumatic native hip dislocation in the absence of acetabular or femoral fracture in adults: a retrospective study reporting clinical and radiological outcomes from a major trauma centre in the United Kingdom.

Introduction: Posterior native hip dislocations (NHD) are high-energy injuries. Thompson-Epstein Type I dislocations describe those without significant associated femoral or acetabular fracture. The aim of this study was to compare the clinical and radiological outcomes of patients with Type I NHDs. We also evaluate the association between radiological indicators of femoroacetabular impingement (FAI) and NHD.

Patients and methods: A retrospective study from January 2012 to May 2021 compared skeletally mature patients (⩾16 years) with Type I posterior NHD to age and gender-matched controls with Type II-V posterior NHD. Patient demographics, mechanism of injury, complications and patient-reported outcome measures (PROMs) are presented. Post reduction radiographs and computed tomography were used to assess for FAI. Univariate analyses were performed to evaluate radiological outcomes.

Results: 13 patients (77% male) with Type I posterior NHD were compared to a control group of 40 patients (80% male) with Type II-V posterior NHD. 11 patients in the study group and 14 in the control group experienced isolated injuries (p = 0.01). Post-reduction complications were similar. The study group had significantly lower post-injury osteoarthritis incidence (n = 0) compared to controls (n = 18, p = 0.0083). Patients reported a mean Oxford Hip Score of 43.5 ± 2.2 and EQ-5D-VAS score of 87.1 ± 7.4, with 6 patients indicating minimal symptoms across all EQ-5D-5L domains. Radiological femoroacetabular impingement (FAI) was prevalent in both groups, especially among males.

Conclusions: Patients who underwent emergent closed reduction of Type I NHD demonstrated good short to medium term outcomes. Our radiological findings suggest a high prevalence of FAI. Future work should aim to quantify longer term outcomes following this injury. We call for further comparative studies of patients who suffer NHD with and without fractures to aid our understanding of risk factors. Given the rarity of this injury, multicentre efforts will be required to capture large numbers of patients.