Background Hip involvement is the most frequent extraspinal arthritic manifestation of Ankylosing Spondylitis (AS) and a common cause of disability. In contrast to the classical changes in the spine, hip joint inflammation does not lead to formation of new bone but results in bone erosions, indicating that at different sites parallel osteoproliferative and osteodestructive changes may occur. Current evidence suggests that anti-TNF treatment does not inhibit radiographic progression in the spine; whether it affects the progression of hip joint space narrowing in AS patients with hip arthritis is not known.
Objectives To examine the impact of continuous long-term treatment with the anti-TNF antibody infliximab on radiographic progression of hip arthritis in AS patients.
Methods Twenty-three consecutive patients with AS and hip involvement (21 men, median age of 45 years) prior to the initiation of infliximab treatment were included in this retrospective study. Infliximab was given as monotherapy in 21 and combined with methotrexate in 2 patients. Anteroposterior X-rays of the pelvis obtained at baseline were compared to X-rays obtained after 5.9±2.2 years (mean±SD) of continuous infliximab treatment (5 mg/kg, every 2 months), using: a) the Bath AS radiology hip index (BASRI-h) scoring system (min 1, max 4), a reliable, disease-specific, sensitive to change method for grading hip radiographic change in AS, and b) the width of the whole joint space estimated by measurement of 3 distinct points of interbone distance (2mm inner of the external end of the acetabulum, vertical line through femoral head center, head-neck center line) with the help of a graduated eyepiece. One senior rheumatologist (A.I.) and one rheumatology fellow (M.K.) performed a blinded radiographic review of 23 X-ray pairs. Intraobserver and interobserver reliability was established using intraclass correlation coefficients (ICC).
Results Both readers achieved excellent agreement for BASRI-h scores and the three points of intraarticular distance (ICC=0.88, 95% CI:0.85, 0,91). The mean±SD BASRI-h score at baseline was 2.50±0.87 and remained unchanged at follow-up end (2.50±0.88). Moreover, the width of the whole joint space at baseline (3.49±0.6 mm) was not reduced after 5.9±2.2 years of infliximab treatment in these patients (3.50±0.74 mm).
Conclusions Despite the lack of a control group our results suggest that long term infliximab treatment inhibits radiographic progression of hip arthritis in responding patients with AS, possibly by blocking a local osteodestructive TNF-mediated effect.
Disclosure of Interest None Declared
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