Acromiohumeral distance in a seated position in persons with impingement syndrome

Purpose To compare the acromiohumeral distance (AHD) of both shoulders in subjects with a unilateral shoulder impingement syndrome (SIS) and healthy subjects in a seated position during free shoulder movements of large amplitude. Materials and Methods Using a 0.5‐Tesla SIGNA‐SP/ i ™ open‐configuration magnetic resonance imaging (MRI) system, the AHD was measured at several arm positions, in a standardized seated position. Results In flexion (rest to 130°), the mean AHD of SIS varied from 8.3 to 2.8 mm, as compared to from 8.7 to 4.1 mm for asymptomatic contralateral shoulders. In abduction (rest to 110°), the AHD varied from 8.1 to 3.4 mm and from 8.8 to 4.6 mm for SIS and asymptomatic shoulders, respectively. The smallest AHD ( P < .01) was observed at 110°. From 80° of arm elevation, the AHD was significantly smaller in impingement than in asymptomatic shoulders ( P < .05). The AHD of asymptomatic shoulders did not differ from that of healthy subjects. In SIS, the AHD at rest was correlated with its reduction at all shoulder positions (r p = 0.62–0.88), but was a poor predictor of the smallest AHD observed at 110° (flexion, R 2 = 0.09; abduction, R 2 = 0.08). Conclusion In the critical arm elevation positions for impingement, AHD is discriminative for SIS, compared to asymptomatic shoulders and healthy ones. AHD at rest is a good indicator of the magnitude of its reduction in elevation, but not of the smallest AHD in arm elevation. J. Magn. Reson. Imaging 2003;18:72–79. © 2003 Wiley‐Liss, Inc.