Anterosuperior Impingement in Throwing Injury of the Shoulder

Abstract

In throwing injury of the shoulder, the patient shows restrictions of flexion and internal rotation. However, the precise mechanisms remain controversial. Gerber et al. described anterosuperior impingement (ASI) as a form of intraarticular impingement in 1999. The purpose of this study was to clarify relationships between throwing injury and ASI. Subjects comprised of 22 patients (mean age, 23.8 years old; range, 16-37 years; 20 men, 2 women) who underwent surgery between 2007 and 2010 for treatment of injuries causing throwing disturbance. Clinical symptoms (range of motion, instability, etc.) were checked preoperatively. Intraoperatively, we checked ASI of all cases in flexion and internal rotation positions. ASI was present preoperatively in 19 / 22 cases and GIRD (glenohumeral internal rotation deficit) existed in 22 / 22 cases. But both diminished postoperatively after reducing anterior instability by reinforcement of the MGHL. We considered that some relationship might exist between ASI and anterior instability, and GIRD resulting from throwing injury. Restrictions of flexion and internal rotation may occur in the shoulder after throwing injury due to ASI.