Total hip arthroplasty (THA) may be complicated by dislocation. The incidence of and risk factors for dislocation are incompletely understood. This study aimed to determine the incidence and predictors of hip dislocation within 2 years of primary THA.

The 2010 to 2020 PearlDiver MHip database was used to identify patients undergoing primary THA for osteoarthritis with a minimum of 2 years of postoperative data. Dislocation was identified by associated codes. Age, sex, body mass index, Elixhauser Comorbidity Index, fixation method, and bearing surface were compared for patients with dislocation versus control subjects by multivariate regression. Timing and cumulative incidence of dislocation were assessed.

Among 155,185 primary THAs, dislocation occurred within 2 years in 3,630 (2.3%). By multivariate analysis, dislocation was associated with younger age (< 65 years), female sex, body mass index < 20, higher Elixhauser Comorbidity Index, cemented prosthesis, and use of metal-on-poly or metal-on-metal implants ( P< 0.05 for each). Among patients who experienced at least one dislocation, 52% of first-time dislocations occurred in the first 3 months; 57% had more than one and 11% experienced >5 postoperative dislocation events. Revision surgery was done within 2 years of index THA for 45.6% of those experiencing dislocation versus 1.8% of those who did not ( P < 0.001).

This study found that 2.3% of a large cohort of primary THA patients experienced dislocation within 2 years, identified risk factors for dislocation, and demonstrated that most patients experiencing dislocation had recurrent episodes of instability and were more likely to require revision surgery.