Objective: The purpose of this study was to evaluate the association between rotator cuff abnormalities and reduced acromiohumeral distance.
Materials and methods: Acromiohumeral distance was measured on conventional radiographs and on MR images. Three age- and sex-matched patient groups each including 21 patients were stratified according to acromiohumeral distance on conventional radiographs (group 1, <or= 7 mm; group 2, 8-10 mm; group 3, > 10 mm). Acromiohumeral distance was related to the presence, location, and size of a rotator cuff tear and the degree of fatty degeneration of the muscle assessed on MR arthrography. The relative influence on acromiohumeral distance of the various MR arthrographic findings was assessed. Spearman's rank correlation and stepwise regression were used for statistical analysis.
Results: In group 1 (acromiohumeral distance <or= 7 mm) full-thickness supraspinatus tendon tears were present in 90% (19/21) of the patients, infraspinatus tendon tears in 67% (14/21) of the patients, and subscapularis tendon tears in 43% (9/21) of the patients. The size of rotator cuff tendon tears and the degree of fatty degeneration in all rotator cuff muscles showed a significant negative correlation with acromiohumeral distance (p < 0.05). After stepwise regression, a significant relative influence on acromiohumeral distance remained for size of rotator cuff tear (p < 0.0001) and for degree of fatty degeneration of the infraspinatus muscle (p = 0.013).
Conclusion: Tendon tears and fatty muscle degeneration in the rotator cuff correlate with reduced acromiohumeral distance. Size of rotator cuff tear and degree of fatty degeneration of the infraspinatus muscle have the most pronounced influence on acromiohumeral distance.