Background Ankylosing spondylitis (AS) is a chronic inflammatory disease affecting the axial skeleton, the enthesis and peripheral joints. The most prominent and common enthesitis occur in the lower extremities, especially the foot at the insertion of Achilles tendon. Peripheral arthritis is uncommon in AS, but it usually occurs in the lower extremities presenting asymmetric oligoarthritis, too. Some suggested that when peripheral arthritis develop early in the disease course it can be a predictor of more aggressive disease and enthesitis may be associated with high disease activity.
Objectives The aim of this study was to investigate the association between radiologic changes of foot and radiologic progression of spine.
Methods We enrolled two-hundred patients with AS who had both feet and whole spine x-ray in similar periods at one tertiary center of rheumatology from 2005 to 2014. We collected demographic findings including sex, age and disease durations. The foot x-ray was reviewed about presence of radiologic changes such as joint space narrowing (JSN) and erosion in ten metatarsophalangeal (MTP) joints and Achilles tendinopathy such as calcaneal spur, retrocalcaneal bursitis and soft tissue thickening by orthopedic surgeon. The radiologic damage of spine was scored by modified Stokes Ankylosing Spondylitis Spinal Score (mSASSS) by two radiologists. And the annual progression rate was calculated by difference of mSASSS divided by x-ray intervals.
Results There were 149 males (73.8%) and 51 females (25.2%). Their mean age and disease duration were 38.5±12.8 years old and 45.9±59.4 months. The 26.5% of patients showed the radiologic changes of MTP joints, and 25.5% of patients had Achilles tendinopathy. There was significant difference between mSASSS in AS patients with radiologic changes of foot (8.2±6.9) and without (10.6±10.9) changes (P=0.036). The mSASSS was significantly increased in patients with Achilles tendinopathy (13.2±14.1) compared to without Achilles tendinopathy (8.8±8.0) (P=0.007). However, there was no significant difference of annual progression rate of mSASSS according to presence of radiologic damages at MTP joints and Achilles tendinopathy, respectively. The risk of radiologic changes of foot in patients without Achilles tendinopathy was more increased than patients with Achilles tendinopathy [OR=2.268 (1.146-4.487), P=0.026].
Conclusions The mSASSS was increased in patients with Achilles tendinopathy, and without radiologic damage of MTP joints, respectively. However, each findings did not associate with annual progression rate of mSASSS. Therefore, the radiologic changes of foot did not show the associations with radiologic progression of spine in this study.
Disclosure of Interest None declared