Factors associated with hip involvement in spondyloarthritis: a retrospective study

Hip involvement is a life-changing event during spondyloarthritis (SpA) since it's responsible for significant disability and functional impairment. This study aimed to determine the factors associated with hip involvement in patients with SpA.

This was a retrospective study, including patients with axial and/or peripheral SpA divided into two groups: patients without and with hip involvement. Hip involvement was defined as pain or abnormality on clinical examination of the hip and/or on imaging. We collected clinical and laboratory data, activity and functional scores, and radiographic parameters. We conducted a multivariate analysis to identify the associated factors of hip involvement.

We included 165 patients with a mean age of 46.13 ± 13.07 years, 121 patients were male. The mean duration of disease was 10.91 ± 6.94 years. Hip involvement, defined as SpA-related hip pain, joint limitation, and dysfunction and/or imaging involvement (X-ray/MRI), was noted in 60 cases (36.4%). Multivariate analysis indicated that disease duration over 10 years (OR=3.847, 95% confidence interval (CI95%)[1.324-11.178], p=0.013), radiographic sacroiliitis (OR=8.949, CI95%[1.261-63.513], p=0.028), very high disease activity (Ankylosing Spondylitis Disease Activity Score: ASDASCRP≥3,5) (OR=9.364, CI95%[2.552-34.352], p=0.001), higher Bath Ankylosing Spondylitis Functional Index (BASFI) (OR=1.439, CI95%[1.120-1.850], p=0.004) and higher Bath Ankylosing Spondylitis Metrology Index (BASMI) (OR=1.311, CI95%[1.065-1.615], p=0.011) were independently associated with hip involvement in these patients. Regarding extra-articular features, we found that pulmonary involvement and osteoporosis were significantly more frequent in patients with hip involvement, but neither retained significance in multivariate analysis.

Disease duration over 10 years, radiographic sacroiliitis, very high disease activity, functional impairment, and limited spine mobility were potential associated factors with hip involvement. Patients with these factors should be closely monitored to detect hip involvement at an early stage.