Sharpened lateral acromion morphology (SLAM sign) as an indicator of rotator cuff tear: a retrospective matched study

BACKGROUND: Bigliani types of acromion and critical shoulder angle (CSA) have been implicated as indicators of rotator cuff disease. A sharpened inferolateral edge of acromion (termed as Sharpened Lateral Acromion Morphology or SLAM sign) is frequently observed in anteroposterior radiographs of the glenohumeral joint in patients with rotator cuff tears (RCT). We aimed to evaluate the association of the SLAM sign with RCT in comparison to high CSA (≥35°) and Bigliani type 3 (hooked) acromion. METHODS: A cohort of 100 consecutive patients undergoing non-arthroplasty surgery for RCT and 106 patients with primary frozen shoulder were matched manually in 1:1 ratio based on age and gender to yield study population with 50 patients in each group. The 2 groups were compared for the presence of the SLAM sign, high CSA, and type 3 acromion on the radiographs. RESULTS: All the 3 parameters were found more prevalent in the RCT group than the frozen shoulder group (SLAM, 46% vs. 0; high CSA, 60% vs. 40%; type 3 acromion, 18% vs. 4%) (P < .05). The SLAM sign showed stronger correlation with RCT than high CSA and type 3 acromion (Ps = 0.562 vs. 0.220 vs. 0.224 respectively). CONCLUSION: The SLAM sign is a simple and easily identifiable radiological predictor of rotator cuff disease.