The development of new instruments and surgical techniques has improved the outcome of rotator cuff repair even with massive tears. Based on cuff integrity or amount of retraction with massive cuff tears a complete repair may not be possible allowing for only partial repair. The ability to mobilize the cuff to the footprint can affect the degree of partial repair that can be performed. Partial repair may lead to abnormal biomechanics that may predispose patients to limited function and subsequent pathology following rotator cuff repair. Therefore, the purpose of this study is to compare the biomechanical characteristics of massive rotator cuff repair according to the degree of repair completion and to determine a minimum degree of repair required to restore normal biomechanics.Copyright © 2010 by ASME