Acromio humeral distance less than six millimeter: Its meaning in full-thickness rotator cuff tear

SummaryThe present study sought to identify full-thickness rotator cuff tears liable to induce an acromiohumeral distance (AHD) of less than 6 mm. The hypothesis was that, less than 6 mm AHD is found exclusively in association with total full-thickness infraspinatus tear.MaterialsA continuous single-center series recruited 109 shoulders, free of glenohumeral osteoarthritis, presenting with full-thickness tear requiring surgery. Preoperative acromiohumeral distance, rupture location and extension on the various tendons and muscular fatty degeneration (FD) were known.MethodsFull-thickness tears were categorized by location and extension on the various tendons. For each group, the number of shoulders showing AHD < 6 mm was determined.ResultsTotal full-thickness infraspinatus tears were almost the only tendon lesions able to induce AHD < 6 mm, but this only when the infraspinatus muscle showed FD equal to or greater than 2.25: i.e., when the tear was longstanding.DiscussionUnlike previous reports, the present study took account of the total or partial nature of infraspinatus and subscapularis tendon tear. The findings may suggest that AHD < 6 mm is induced by posterior migration of the humeral head secondary to longstanding total infraspinatus tear, reducing AHD projection height on X-ray.ConclusionAHD < 6 mm is a sign of rotator-cuff rupture almost systematically involving longstanding total infraspinatus tear, not always amenable to suture repair due to advanced fatty degeneration. AHD equal to or greater than 6 mm is of no diagnostic relevance and in no way indicates whether there is subscapularis tear and, if so, whether suture repair is feasible.Level of evidenceLevel IV (retrospective study).