Anterior acromial anatomy: Relevance to arthroscopic acromioplasty.

PURPOSE To evaluate the effect of arthroscopic acromioplasty on the anterior deltoid origin. TYPE OF STUDY In vitro cadaveric histologic study. METHODS We performed a histologic evaluation of the anterior aspect of 15 acromions, the parameters of the anatomy of the anterior acromion, including the deltoid origin, and the morphology of the acromion. A simulated arthroscopic acromioplasty was performed and the effect on the anterior deltoid origin was determined. RESULTS Resection of 4 mm of bone from the underside of the acromion resulted in release of 56% (+/- 11%), and resection of 5.5 mm of bone resulted in 77% (+/-15%) release of the deltoid origin. The amount of deltoid released correlated statistically with both the thickness of the acromion and the acromial angle ( P < .0001 and P = .04). CONCLUSIONS These findings show that arthroscopic acromioplasty can cause substantial injury to the deltoid origin, that this effect is related to acromial anatomy, and that preoperative planning may help to reduce the risk of excessive deltoid origin release. CLINICAL RELEVANCE Consideration of acromial anatomy is required to avoid deltoid detachment when performing arthroscopic acromioplasty.