A Retrospective Review of Intra-articular Methylprednisolone Hip Injection and Development of Rapidly Progressive Idiopathic Arthritis in Adults.

Background: Rapidly progressive idiopathic arthritis (RPIA) of the hip is a rare, poorly understood, destructive hip disease. Etiologies are understudied; however, recent literature suggests a causal relationship between intra-articular corticosteroid hip injections and the development of RPIA. This study's primary objective was to identify the prevalence of RPIA following methylprednisolone intra-articular hip injections (IAHI) and assess these cases' baseline characteristics. Methods: Patients who received at least 1 fluoroscopy-guided methylprednisolone IAHI into a native hip between January 2010 and December 2019, had available preinjection and postinjection images, and met inclusion criteria were enrolled. Demographic variables, injection dose and laterality, and number of injections per hip were collected from electronic medical records. Postinjection RPIA was determined through imaging review. Results: The total was 1,402 unique hips. The mean age at the time of first injection was 63 (SD = 12.65), and 54% (n = 752) of patients were female. Review of preinjection and postinjection imaging revealed 31 cases of RPIA, thus 2.2% overall prevalence. The mean number of methylprednisolone injections per hip was 1.67 (SD = 1.72), with a mean cumulative dose of 74.91 mg (SD = 84.58). Conditional logistic regression showed each 100 mg increase in cumulative dose was associated with an odds ratio of 0.90 (95% confidence interval 0.59-1.37; p = 0.62). Thus, increasing dose was not significantly associated with the risk of RPIA. Conclusion: To our knowledge, this is the first study to exclusively analyze methylprednisolone IAHI, which found a lower prevalence of postinjection RPIA than most previous studies. Importantly, cumulative methylprednisolone dose was not significantly associated with an increased risk of RPIA, suggesting that repeat dosing within the studied ranges is unlikely to substantially increase the risk of this complication. Level of Evidence: Level II. See Instructions for Authors for a complete description of levels of evidence.