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

Abstract

Recurrent instability remains a leading indication for revision following primary THA. However, data regarding outcomes following early dislocation is dated and limited in scope. Whether this existing data applies to contemporary practice with the broad adaptation of high-stability bearings and modern surgical techniques is unknown. Therefore, we assessed revision and re-dislocation 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 two-year cumulative incidence of aseptic revision, septic revision, and recurrent dislocation after 90 days was determined by competing risks 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). Incidence of either dislocation or aseptic revision after 90 days in those who had 0, 1, or 2+ early dislocation events was 1.3, 24.0, and 51.0% at 2 years, respectively (p<0.001). Early dislocation was associated with increased risk of all-cause revision (HR 22.6; 95% CI, 20.23-25.2; p<0.001), revision for dislocation (HR 98.4; 95% CI, 83.5-116.0; p<0.001), and aseptic revision for non-instability issues (HR 9.8; 95% CI, 8.4-11.4; 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 in this population. This data provides relevant clinical data to assist surgical decision-making following early hip dislocation.