Spontaneous detachment of the deltoid muscle origin.

Three patients with four affected shoulders with spontaneous detachment of the deltoid origin are reported. In this group spontaneous detachment of the deltoid origin was associated with chronic massive rotator cuff defects. Detachment of the deltoid origin was associated with an acute, sudden onset of shoulder weakness. Pain was not a prominent complaint, and shoulder function was poor because of weakness. Spontaneous detachment of the deltoid origin can occur with chronic massive rotator cuff tears and can be responsible for an acute onset of shoulder weakness.