Deltoid Insertion Tendon

tendo insertivus musculi deltoidei

The deltoid muscle inserts via a thick convergent tendon onto the deltoid tuberosity of the lateral humerus at the mid-shaft level, where all three portions (anterior clavicular, middle acromial, and posterior scapular spine) converge to a single V-shaped footprint. The insertion tendon is short and broad, spanning approximately 2-4 cm on the lateral humerus. The radial nerve and profunda brachii pass just posterior to the insertion at the level of the spiral groove.

Region: Upper Arm

Clinical Relevance

Clinical Notes

The deltoid insertion is the reference for humeral nail entry and exit point assessment in intramedullary nailing. In humeral shaft fracture fixation, the deltoid tuberosity (containing the insertion) is the anatomical reference for assessing axial alignment and version. Deltoid insertion avulsion is extremely rare but can occur with violent shoulder abduction trauma. In surface anatomy, the deltoid tuberosity where the tendon inserts is the midpoint of the lateral upper arm and the approximate level of the radial nerve in the spiral groove just posterior to the tuberosity.

Pathology

Common Injuries & Conditions

Deltoid Insertion Level as Radial Nerve Reference

The deltoid insertion tendon at the mid-lateral humerus marks the approximate level of the radial nerve in the spiral groove posterior to the tuberosity; knowledge of this relationship guides safe surgical approaches to the mid-humeral shaft and informs the surgeon of the nerve risk zone in any mid-humeral fracture management.