Background Although there is debate whether treatment with TNF inhibitors (TNFi) in AS may not inhibit spinal radiographic progression, the effect on hip involvement may be different (1,2).

Objectives To estimate the impact of long-term TNFi treatment on radiographic progression of hip arthritis in AS, by adding a quantitative scoring method, previously applied in hip osteoarthritis, to the BASRI-hip score.

Methods Consecutive TNFi-naïve AS patients (fulfilling the modified New York criteria) who were eligible for TNFi treatment were included. Hip involvement was assessed clinically (pain, reduced range of motion and intermalleolar distance) and radiographically. X-rays of the pelvis and lateral cervical and lumbar spine were obtained at 3 time points: at baseline two and seven years after the start of TNFi. Both hips were scored using: a) BASRI-hip score (BASRI-h score ≥2 is classified as definitive hip involvement), b) mean joint space width (MJSW), 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 (1). Spinal X-rays were scored were scored blindly, by 2 independent readers using the mSASSS. The significance of changes was tested by mixed models for longitudinal data.

Results 262 AS patients (188 men, age: 49.8±12 years, disease duration: 24.4±12 years) under TNFi treatment were included. Definite hip involvement at baseline was detected in 95/262 (36%) patients, who had significantly higher BASRI-hip score [2 (2–2.5) median (IQR) vs. 0.5 (0–1) p<0.0001] and lower MJSW (3.6±0.7 vs. 4.5±0.7, p<0.0001), compared to those without. In patients with hip arthritis at baseline, both BASRI-h score and MJSW remained unchanged during follow up. In patients without hip arthritis, the BASRI-hip score remained unchanged after 2.5±0.7 years, but increased significantly after 7±2.3 years compared to baseline. In contrast, the MJSW in patients without hip arthritis remained unchanged at the three time points. The mSASSS raised significantly during the follow-up period, regardless of hip involvement (see table).

Conclusions One third of the AS patients suffer from radiographic hip involvement, which seems to stabilize during long-term anti-TNF treatment. Assessment of MJSW may contribute to detect minor changes in contrast to BASRI-hip score' rough estimation.

References

1. Konsta M, et. al, Clin Rheumatol. 2013 Aug;32(8):1229–32.

2. Nystad TW, et. al. Annals of the rheumatic diseases. 2014 Jun;73(6):1194–7.

References

Disclosure of Interest None declared