Delayed Spontaneous Pectoralis Major Tendon Rupture Following Anterior Latissimus Dorsi Transfer for Irreparable Subscapularis Tear: A Case Report

Introduction: Irreparable subscapularis (SSC) tears can lead to significant functional impairment, particularly affecting internal rotation (IR) and anterior shoulder stability. Anterior latissimus dorsi (LD) tendon transfer has gained popularity as a surgical option due to its favorable biomechanical alignment with the SSC. Although partial release of the pectoralis major (PM) tendon is commonly performed during LD harvest and is generally considered safe, its long-term effects on PM integrity remain unclear. This report describes a rare case of delayed spontaneous rupture of the PM humeral insertion following anterior LD transfer. Case Report: A 57-year-old male presented with progressive IR weakness 5 years after undergoing anterior LD transfer for an irreparable SSC tear. Imaging revealed an intact transferred LD tendon but a complete rupture of the PM humeral insertion with muscle atrophy. The patient underwent PM tendon transfer with acellular dermal matrix augmentation. At 1-year follow-up, significant improvements were observed in pain (Visual Analog Scale 4-1), Constant score (59-81), and American Shoulder and Elbow Surgeons score (57-82). IR strength improved markedly, and functional tests normalized. Imaging confirmed intact tendon healing, and the patient returned to daily activities without complications. Conclusion: Delayed rupture of the PM tendon can occur as a long-term complication after anterior LD transfer. PM transfer represents an effective salvage procedure, restoring IR strength and shoulder function. Awareness of this potential complication and preservation of the PM insertion during the index procedure are essential.