Pathogenesis of deltoid muscle ruptures associated with rotator cuff tears in elderly patients is not clearly elucidated. The purpose of this study was to clarify the clinical features and image findings. 5 shoulders with deltoid muscle ruptures were included in this study. The patient's mean age at the onset was 80 years old and the mean period from onset to the 1st visits was 14 days. Mechanism of disease, history of steroid injections, clinical courses were assessed. The location and type of deltoid muscle ruptures were evaluated using MRIs. Superior migration of the humeral head and spur formations were assessed in X-rays. As causative factors, a fall, heavy labor, and shoulder elevation exercises was found in 1 shoulder. The other 2 had unknown mechanisms. 2 patients underwent injections of steroids. Motion pains, limitation of shoulder elevation, and subcutaneous hematoma at the lateral side of the upper arm were observed in all. All cases showed disability of elevation just after the onset, which had recovered to 40 degrees at the 1st visits. X-ray findings demonstrated superior migration of the humeral head in all, and spur formations at the subacromion in 4 and the greater tuberosity of the humerus in all. MRIs demonstrated detachment of the deltoid muscle origin in 2, and partial rupture of the deltoid muscle belly with nodal high intensity in T2 weighted MRI images in 3. Deltoid muscle ruptures associated with rotator cuff tears were classified into 2 types: detachment of the origin and partial rupture of the muscle belly. Detachment of the muscle origin showed no improvement with conservative therapies. However, the degree of elevation in cases with partial rupture of the muscle belly had returned to the original level in 1 month with conservative therapies. The clinical course and choice of treatment may be different between them.
