Reliable semiquantitative whole-joint MRI score for the shoulder joint: The shoulder osteoarthritis severity (SOAS) score

Abstract

BACKGROUND Shoulder osteoarthritis causes severe pain and functional disability. Preventive surgical procedures aiming to halt the progression of degenerative changes are increasingly applied. However, no MRI-based score exists that may be applied for scoring of osteoarthritic changes and their progression. PURPOSE To establish a semiquantitative MRI-based shoulder osteoarthritis severity (SOAS) evaluation system and to test its reliability. STUDY TYPE Retrospective. SUBJECTS A total of N = 60 patients (73.2 ± 7.3 years; 30/60 female) was included; n = 15 subjects for each of the four radiographic grades of osteoarthritis (Samilson score 0 to 3). ASSESSMENT Based on the MRIs of the shoulder, the SOAS scoring system was created. All MRIs were assessed by six readers. The severity of degeneration was evaluated for: rotator cuff, labral-bicipital-complex, cartilage, osseous findings, joint capsule, and acromion. The total SOAS score ranged between 0 (absence of osteoarthritis) and 100 (most severe osteoarthritis). SOAS scores were correlated with radiographic Samilson, Hamada and Kellgren-Lawrence (KL) gradings. STATISTICS Pearson correlations, t-tests, receiver operating characteristics (ROC) and interclass correlation coefficients (ICC). RESULTS Intra- (ICC = 0.99) and interreader agreement (ICC 0.96-0.98) for the total SOAS score was excellent. The range of SOAS scores was from 1 to 88. SOAS correlated significantly with radiographic Samilson and KL scores (R = 0.82, P < 0.001), but not with Hamada scores (R = -0.07, P = 0.60). The highest correlations with Samilson scores were found for cartilage (R = 0.82, P < 0.001) and osseous findings (R = 0.86, P < 0.001). SOAS scores were significantly different between different Samilson grades (Samilson 0, 13.4 ± 7.6; Samilson 1, 26.0 ± 9.1; Samilson 2, 38.2 ± 19.2; Samilson 3, 65.5 ± 13.0; P < 0.05). The ability of the SOAS score to predict incident radiographic shoulder OA (KL grade ≥2) was excellent (AUC = 0.91; P < 0.001). DATA CONCLUSION The newly developed semiquantitative MRI-based SOAS score represents the severity of global shoulder OA and structure-specific shoulder degeneration with excellent reliability in a standardized manner and may therefore be helpful in MRI research studies of the shoulder. LEVEL OF EVIDENCE 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018.