Limit of the available spine radiologic scoring methods in ankylosing spondylitis when the facet joint is the only structure involved

BackgroundAnkylosing spondylitis (AS) is a chronic inflammatory disease that affects the axial skeleton and can lead to complete ankylosis of the involved joint. Unfortunately, involvement of the facet joints (FJ) is not evaluated by the available scoring methods that are supposed to quantify the structural damage of the spine.Aim of the workThe aim of the present study we assessed is the involvement of FJ in Tunisian AS patients with low radiological score.Patients and methodsResults of 8 AS patients (7 men; 1 woman) with FJ involvement and low radiological scores were retrospectively studied. Their median age was 36 years, age at onset 26 and disease duration of 10 years. The Bath AS Radiology Index (BASRI) and the Stoke AS Spinal Score (SASSS) were calculated in all patients from the radiographs of lateral cervical spine, anteroposterior and lateral lumbar spine.ResultsAll patients had FJ ankylosis without involvement of the anterior part of the spine. Six patients (75%) had inflammatory back pain and 2 had bilateral hip pain with radiological involvement. Cervical spine limitation was noted in 4 patients. Limited lumbar spine mobility and bilateral sacroiliitis were present in all cases. The HLA-B27 typing was positive in 6/7 cases. Five patients had restrictive lung disease and 3 had osteoporosis.ConclusionInvolvement of FJ in AS may be the only sign of spine damage and may be responsible for functional impairment, however, it is not evaluated by the available radiographic scores which is an important limitation to their use.