Biomechanics of coracoacromial arch modification.

Although the biomechanics of the coracoacromial arch and coracoacromial ligament (CAL) morphology are well studied, to our knowledge, the biomechanics of the coracoacromial arch after CAL resection and medial reattachment have not yet been studied. The purpose of this report is to examine the biomechanical consequences of coracoacromial arch alteration and subsequent reconstruction in cadaveric specimens. Anterosuperior humeral head translation was measured after the application of an anterosuperior 150-N load under 5 sequential scenarios: (1) intact CAL, (2) subperiosteal CAL release, (3) standard acromioplasty, (4) CAL reconstruction, and (5) modified Neer acromioplasty. A significant decrease in anterosuperior migration was found after CAL reconstruction compared with both anterior acromioplasty (P = .038) and modified Neer acromioplasty (P = .01). Thus, in patients with massive rotator cuff tears, reconstruction of the CAL may provide the necessary stabilizing force to prevent excessive anterosuperior translation and possible humeral head escape from the coracoacromial arch.