- 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 the 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;
The sub-deltoid approach to the metaphyseal region of the humerus.
Contracture of the Deltoid Muscle. Results of distal release.
J. Ko MD et al.
JBJS. Vol 89-A. No 2. Feb 1998.
A cadaveric study on the anatomy of the deltoid insertion and its relationship to the deltopectoral approach to the proximal humerus.
