Safety of Intra-articular Hip Corticosteroid Injections: A Matched-Pair Cohort Study

Background: Recent studies have suggested there is an increased risk of avascular necrosis (AVN), subchondral insufficiency fracture (SIF), femoral head collapse, and osteoarthritis (OA) progression in the 12-month period after hip corticosteroid/anesthetic injection (CSI); however, these studies have failed to account for preinjection OA severity or preexisting AVN/SIF. Purpose: To compare these complication rates in patients treated with versus without hip CSI, while minimizing the aforementioned forms of selection bias present in previous investigations. Study Design: Cohort study; Level of evidence, 3. Methods: For all patients who had undergone a single hip CSI and hip magnetic resonance imaging (MRI) within the preceding 12 months at a single institution (CSI cohort), 2 musculoskeletal radiologists retrospectively graded OA severity (modified Kellgren-Lawrence classification) and femoral head collapse on hip radiographs taken within 12 months before, and 1 to 12 months after, CSI. Using identical methodology, radiographs from a control cohort (composed of hips that had never undergone CSI and had undergone hip MRI with hip radiographs taken within 12 months before, and 1-12 months after, MRI) were also graded. The cohorts were matched for age, sex, body mass index, and OA severity. Readers were blinded to cohort and time point. OA progression was defined as an increase in modified Kellgren-Lawrence grade >= 1 between radiographs. Results: Included were 141 matched pairs. After exclusion of 48 matched pairs with at least 1 incidence of preexisting AVN or SIF on index MRI, CSI (n = 93; mean time between CSI and final hip radiograph, 5.43 months) and control (n = 93; mean time between MRI and final hip radiograph, 4.87 months), groups did not significantly differ in rates of OA progression (3.2% vs 3.2%) or new femoral head collapse (3.2% vs 2.2%). Conclusion: In contrast to the findings of recent retrospective investigations, we did not find that patients treated with hip CSI had significantly higher rates of short-term OA progression or femoral head articular surface collapse after controlling for baseline OA severity and preexisting AVN or SIF. Future randomized trials investigating safety of hip CSI are needed to determine its exact short-term risk profile.