Risk of Femoral Head Osteonecrosis Following Hip Trauma in Adults With Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a known risk factor for femoral head osteonecrosis (FHON), but its impact on FHON risk following hip trauma has not been well characterized. We evaluated whether adults with SLE have an increased risk of FHON after hip trauma compared with patients without SLE.

We conducted a retrospective cohort study using de-identified electronic health record data from the TriNetX Research Network. Adults aged 18 to 65 years with an incident hip trauma diagnosis and no prior FHON were included. SLE was defined by the presence of an ICD-10 diagnosis code for SLE documented in the electronic health record. Patients with and without SLE were matched 1:1 using propensity scores incorporating demographics, baseline comorbidities, and systemic glucocorticoid exposure. The primary outcome was incident FHON within 5 years following hip trauma, with a secondary analysis evaluating FHON risk in matched cohorts without hip trauma. Kaplan-Meier and Cox proportional hazards analyses were performed.

Among adults with incident hip trauma, patients with SLE had a higher 5-year incidence of FHON than patients without SLE. In propensity score-matched time-to-event analyses, SLE was associated with an increased hazard of osteonecrosis (hazard ratio: 2.9; 95% CI: 2.0-4.3; log-rank p < 0.001). These findings were consistent with a similarly elevated baseline risk of FHON observed in patients with SLE in analyses without hip trauma.

SLE is associated with an increased FHON risk both with and without hip trauma. The modest absolute post-trauma risk difference supports symptom-guided vigilance rather than routine imaging after trauma.

Persistent, progressive, or atypical hip symptoms after trauma in patients with SLE warrant clinical vigilance for osteonecrosis, but these findings do not support routine imaging of all patients with SLE after trauma.