Massive rotator cuff tears are one of the most common shoulder problems among the elderly, leading to pain and disability of the upper extremity. Muscle transfer, which can compensate for some of the deficits, has been advocated as the primary treatment of irreparable massive rotator cuff tears or as a salvage procedure after failed repairs. Latissimus dorsi transfers offer a promising solution in the treatment of irreparable posterosuperior rotator cuff tears, resulting in pain relief and function improvement of patients with the tears. However, the clinical results are variable and the factors which determine outcome are poorly understood. Prior studies have revealed that the functional outcomes of latissimus dorsi transfers were adversely affected if there was a deficit in deltoid and teres minor muscles [1, 2]. For the patient with a deltoid injury, the transfer that follows a failed rotator cuff repair produces less functional improvement than if the transfer is performed as the primary treatment to repair the rotator cuff. It was revealed that the presence of a tear of the teres minor muscle might have some predictive value prior to surgery with regard to motion and function [1], whereas the degree of fatty infiltration also played a critical role after the transfer [2]. Outcomes of muscle transfers have been reported in the literature, but the effects of extrinsic muscle integrity on the functional outcomes in the latissumus dorsi transfer have not been addressed quantitatively. The purpose of this work was to study the effects of the extrinsic muscle integrity on the functional outcomes in the latissumus dorsi transfer using a three-dimensional integrated model of the upper extremity [3]. First, the effects of extrinsic muscle integrity on the preoperative functions of shoulders with massive rotator cuff tears were investigated. Second, these effects on the functional outcomes of muscle transfers were evaluated quantitatively.

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