Hooked acromion: prevalence on MR images of painful shoulders.

An association between the morphology of the acromion and the occurrence of rotator cuff tear (RCT) has been suggested by findings at both pathologic examination and routine radiography. As a tomographic technique, magnetic resonance (MR) assessment of acromial shape may be more accurate than routine radiography. The authors studied acromial morphology on sagittal oblique MR images of a control population (47 shoulders), of patients with isolated impingement (30 shoulders), and of patients with full-thickness RCTs (34 shoulders) to assess the association of acromial shape with disorders of the rotator cuff. Acromions were classified as flat (type 1), smoothly curved (type 2), or hooked (type 3). Data were collected by two observers, blinded to clinical and surgical information, who acted in consensus. Patients with RCT had a significantly increased prevalence of type 3 acromions compared with control patients (62% vs 13%, P < .001). Type 3 acromions tended to be more prevalent in the group with impingement (30%, P = .17). There was no significant difference in the distribution of acromion types among control patients with respect to age or gender.