Acromial Morphology in Different MR Oblique Sagittal Slices: Correlation with Rotator Cuff Disorder

Purpose: On the hypothesis that the acromion morphology is changed according to the its site, we identified the morphology of the acromion on the oblique slices of MRI and we investigated the association of the acromial shape with the clinical stages of rotator cuff disorder on the magnetic resonance (MR) images. In addition, we compared the acromion morphology on MRI and simple X-rays. Material and Methods: The MR images of seventy one patients with rotator cuff disorder and who underwent arthroscopic surgery were compared with that of a control group of sixteen patients who didn’t have rotator cuff disorder on MRI. On three subsequent oblique sagittal slices from the lateral edge of the acromion (S1, S2 and S3), each acromion morphology on the MRI slices was classified according to Epstein et al: flat, curved or hooked. We investigated the changing parttern of the acromion shape and we compared the acromion shape on MRI and that on simple X-rays. We classified the rotator cuff tear by the severity: bursitis, partial thickness tear or full thickness tear. We investigated which acromial type on the MRI oblique slice was associated with the severity of rotator cuff disease. Results: Changes of the acromial shape occurred in 54 patients (76.1%). The most frequent pattern was that the types are same on S1 and S2 and different on S3 (22 cases, 31.0%). The acromial type on S1 and S2 was significantly associated with the severity of rotator cuff disorder (p=0.001 and 0.022), respectively. There was no reliability of the acromial shape on MRI and roentgenography (p>0.05). Conclusion: The type of acromion changed from lateral to medial. Among the three positions, the shape of the acromion on S1 and S2 had meaningful correlation with the clinical stage of rotator cuff disorder. There was no statistical correlation of the acromial shape between MRI and simple X-ray.