Chronic intramuscular calcific tendinitis of the deltoid muscle.

Calcific tendinitis is a potentially symptomatic disorder characterized by calcium deposits in the substance of the tendon. Although this condition can occur in any tendinous tissue throughout the human body, calcium deposition commonly occurs at tendon insertions near the bone-tendon junction. The musculotendinous junction of the deltoid muscle has peculiarly dense intramuscular tendons to which muscle fibers attach obliquely to create muscular strength. Given that the intramuscular tendons themselves, which form the consecutive part from the insertion, are subjected to unpredictable stress load or microtrauma similar to tendon insertions, it is reasonable to assume that calcific tendinitis could also occur at the intramuscular tendons. Here we report a case of chronic symptomatic calcium deposition in the lateral part of the deltoid muscle between the origin and the insertion, which was eventually surgically removed and confirmed as intramuscular calcific tendinitis.