Patients with Simple Posterior Hip Dislocations Have Higher Rates of Hip Dysplasia and Borderline Dysplasia.

Abstract

To determine if patients suffering simple, posterior hip dislocations are more likely to display dysplastic characteristics of their acetabulum as compared to those suffering fracture dislocations. Retrospective Cohort Study. Level 1 trauma center.Patients/Participants: 86 patients suffering posterior, native hip dislocations over a 5 year period. The primary outcome was measurement of the lateral center edge angle (LCEA), acetabular index (AI), acetabular version, and Femoro-Epiphyseal Acetabular Roof (FEAR) index. Eighteen (20.9%) patients sustained simple dislocations while 68 (79.1%) suffered fracture dislocations. Patients with simple dislocations had decreased LCEA (25.7 versus 34.3; P<0.001), increased AI (7.4 versus 5.8; P=0.019) and decreased acetabular anteversion (14.02 versus 18.45; P = 0.011). Additionally, patients with simple dislocations had higher rates of dysplasia and borderline dysplasia (61.1% versus 7.3%; P<0.001). Patients with fracture dislocations had higher rates of concomitant injuries (60.9% versus 29.4%; P=0.039) as well as higher injury severity scores (8.1 versus 12.3; P = 0.022). Patients who sustain simple hip dislocations are more likely to have under-coverage of the femoral head by the acetabulum as compared to patients suffering fracture dislocations. In addition, the simple dislocation group had a lower ISS and fewer concomitant injuries, which likely relates to a lower energy required for dislocation in the setting of lesser bony constraint. Surgeons treating these complicated injuries should consider measurements of LCE and AI when counseling patients on treatment strategies. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.