A cadaveric study on the anatomy of the deltoid insertion and its relationship to the deltopectoral approach to the proximal humerus.

Elevation of the deltoid insertion (DI) has been recommended, but little is known about its anatomy or importance for deltoid function. The purpose of this study is to determine the dimensions of the DI with specific reference to the deltopectoral approach. The deltoid was exposed and detached at its origin in 36 cadaveric shoulders. The morphology of the DI was documented, and its relationship with the pectoralis major insertion and the axillary and radial nerves was recorded. The anterior, middle, and posterior deltoid muscle fibers entered into the DI in a V-shaped tendinous confluence with a broad posterior band and a narrow separate anterior band, which accounted for the anterior one fifth of the DI (0.44 cm). The deltoid insertion was separated from the pectoralis major insertion by as little as 2 mm in 31 of 36 specimens. The distance between the axillary nerve and the DI averaged 5.6 cm anteriorly and 4.5 cm posteriorly. The distance between the radial nerve and posterior deltoid insertion averaged 2.4 cm proximally and 1.6 cm distally. Exposure during the deltopectoral approach is most limited by the close proximity of the deltoid and pectoralis major insertions. Our study would suggest that partial anterior DI release (greater than one fifth) could compromise the anterior deltoid. The axillary and radial nerves are not at significant risk when operating in the region of the anterior DI.