The anterior tilt of the acromion: radiographic evaluation and correlationwith shoulder diseases

The aim of this study was to test whether the anterior tilt of the acromion can be objectively evaluated on lateral radiographs, and whether there is a relation between this anatomical feature and the most common shoulder dis eases. Lateral radiographs of 15 dried scapulas were performed in neutral p osition and with 5 degrees of caudal, cranial, anterior and posterior angul ations. Two hundred and forty-three shoulders, both asymptomatic and affect ed by chronic and post traumatic impingement, calcific tendinitis and insta bility, were examined by conventional radiography. The presence of rotator- cuff tears was investigated by sonography. A method was elaborated to obtai n reproducible lateral radiographs and to determine the acromial tilt angle . Inter- and intraobserver and inter- and intraoperator variations in measu rements were evaluated. Variations in tube angulation produced changes in t ilt-angle values on dried scapulas. the average tilt angle for the chronic impingement and the instability groups were significantly different from th e post-traumatic, calcific tendinitis and control groups. Rotator-cuff tear s were significantly more frequent in the chronic impingement group and rel ated to a more acute tilt angle. The inter- and intraobserver variability c oefficients were 0.95 and 0.98, whereas the inter- and intraoperator variab ility coefficients were 0.94 and 0.96, respectively. Conventional radiograp hy using flouroscopy for positioning is a well-reproducible method for the evaluation of acromial tilt. There is a significant difference in tilt-angl e values between some groups of subject examined, but the lack of specifici ty limits the clinical importance of such measurement.