Deltoid Muscle 

- See: Shoulder Abductors

- Discussion:
    - major function of the deltoid muscle is to abduct  arm;
    - it performs this action after   scapula[scapula  has been fixed by its stabilizing muscles and the humeral head  has been
           snubbed to glenoid  by the rotator cuff;
    - it is innervated by axillary nerve (C5);

- Anterior Division:
    - origin: anterior border of the lateral 1/3 of the clavicle;
    - insertion: deltoid tuberosity of the humerus;
    - action: abduction, horizontal flexion and medial rotation of humerus at shoulder;
    - nerve supply: axillary, C5, C6 ;
    - synergists: medial and posterior deltoid divisions, supraspinatus and pectoralis major clavicular division;

- Deltoid: Medial Division:
    - origin: superior surface of the acromion process;
    - insertion: deltoid tuberosity of humerus;
    - action: abduction of the humerus at the shoulder
    - nerve supply: axillary, C5, C6;
    - synergists: anterior and posterior deltoid divisions, supraspinatus;

- Deltoid: Posterior Division:
    - origin: inferior margin of spine of scapula;
    - insertion: deltoid tuberosityy of humerus;
    - action: abduction, horizontal extension & lateral rotation of humerus at shoulder;
    - nerve supply: axillary, C5, C6;
    - synergists: anterior and medial divisions of deltoid, supraspinatus;

- Surgical approach:
    - if deltoid muscle is split anteriorly for > 5 cm, branches of axillary nerve will be damaged, rendering corresponding portion of deltoid muscle deinnervated;
           - however, deltoid is innervated by the axillary nerve, whose branches pass upward as they extend anteriorly & may come as close as 2 cm to acromion;
                 - hence, this anamatomy defies the described 5 cm safe zone;
    - posteriorly: medial edge of the deltoid is too medial to provide useful access to the glenohumeral joint;
           - access must be acheived by splitting deltoid, which is most conveniently done at junction of its middle & posterior thirds;
    - site is favorable for a split because it overlies joint & also because axillary nerve exiting quadrangular space divides into 2 trunks
           (anterior and posterior divisions) in an inferior location;

- Deltoid Contracture:
    - often arises from multiple intra-muscular injections;
    - clinical manifestations:
          - shoulder pain, palpable fibrous band, scapular winging, difficulty in combing hair, and an abduction contracture;
    - radiographs: anterosuperior subluxation of the humeral head;
    - management: distal release;

- Deltoid Paralysis: (most commonly occurs from parsonage turner syndrome)

The sub-deltoid approach to the metaphyseal region of the humerus.

Contracture of the Deltoid Muscle. Results of distal release

A cadaveric study on the anatomy of the deltoid insertion and its relationship to the deltopectoral approach to the proximal humerus.

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Tuesday, April 10, 2012 4:10 pm