Tehran University of Medical Sciences Journal of Orthopedic and Spine Trauma 2538-2330 11 4 2025 12 02 194 8 Reza Moulaei Department of Orthopedic and trauma surgery, Shariati hospital, Tehran university of medical sciences, Tehran, Iran Leila Oryadi Zanjani Associate Professor, Department of Orthopedics, Center for Orthopedic Trans-Disciplinary Applied Research, Tehran University of Medical Sciences, Tehran, Iran 2025 04 18 2025 11 23 Background: Acromioclavicular (AC) joint dislocation is a quite common shoulder injury, especially among young, athletic people. Despite various treatment approaches, AC joint injuries still pose significant treatment challenges. Common concerns include postoperative pain, limited shoulder mobility, and hardware-related complications. In recent years, a number of surgical methods have been developed with the goal of improving functional outcomes while reducing complications. In this study, we report a surgical technique using semitendinosus allograft and an 8-plate for a patient with type III AC joint dislocation. Case Report: A 33-year-old man sustained a type III AC joint dislocation following a motorcycle accident. Initial non-surgical management failed to relieve pain or restore full shoulder mobility. As a result, the patient underwent surgical intervention using semitendinosus allograft in combination with an 8-plate device. At the three-month follow-up, the patient had complete shoulder range of motion (ROM) and showed no symptoms of discomfort, dislocation, or joint prominence. Conclusion: AC joint dislocation treatment remains debated, but recent advancements in surgical methods have made it more effective. Reconstruction using semitendinosus allograft and 8-plate device offers improved clinical outcomes with fewer complications. https://jost.tums.ac.ir/index.php/jost/article/view/673 https://jost.tums.ac.ir/index.php/jost/article/download/673/450