The Fate of the Patient Who Has Early Dislocation After Contemporary Primary Total Hip Arthroplasty

Recurrent instability remains a leading indication for revision following primary total hip arthroplasty (THA). However, data regarding outcomes following early dislocation are dated and limited in scope. Whether these existing data apply to contemporary practice with the broad adaptation of high-stability bearings and modern surgical techniques is unknown. Therefore, we assessed revision and redislocation rates following early dislocation in a contemporary group of patients following primary THA.

A national database was used to identify patients undergoing primary THA from 2009 to 2022. Patients were divided into two cohorts: those with one or more dislocation events within 90 days and those who did not dislocate as the control group. Landmark survivorship analysis was utilized, given the potential for immortal time bias. The 2-year cumulative incidence of aseptic revision, septic revision, and recurrent dislocation after 90 days was determined by competing risk analysis.

At two years, the dislocation rate in all patients undergoing a single primary THA (n = 420,053) was 1.2%. After landmark analysis, the incidence of aseptic revision or dislocation after 90 days in patients with an unrevised early dislocation event (n = 1,942) was 29.0 versus 1.3% in controls (n = 360,493) (P < 0.001). The incidence of either dislocation or aseptic revision after 90 days in those who had zero, one, or 2+ early dislocation events was 1.3, 24.0, and 51.0% at two years, respectively (P < 0.001). Early dislocation was associated with increased risk of all-cause revision (hazard ratio [HR], 22.6; 95% confidence interval [CI], 20.23 to 25.2; P < 0.001), revision for dislocation (HR, 98.4; 95% CI, 83.5 to 116.0; P < 0.001), and aseptic revision for noninstability issues (HR, 9.8; 95% CI, 8.4 to 11.4; P < 0.001).

Early dislocation within 90 days after primary THA was associated with a markedly increased risk of aseptic revision and recurrent dislocation within two years, with multiple early dislocations identified as an indicator of poorer prognosis.