Deltoid: Anatomy and Injury

Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

Anatomy Of Deltoid Muscle

• The Deltoid Muscle Begins At The Lateral Third Of The Clavicle, Acromion and Spine Of The Scapula Continuing Down To Its Insertion Into The Deltoid Tuberosity Of The Humerus.
• the shoulder and deltoid muscle get its rounded appearance due to the deltoid passing over the upper part of humerus.

Actions:

• The Middle Part Of The Deltoid Muscle Is Responsible For The Abduction Of The Arm, Which Raises The Arm To The Horizontal Level.

• The Anterior Part Of The Deltoid Muscle Flexes And Medially Rotates The Arm
• The Posterior Part Extends And Laterally Rotates The Arm

Nerve Supply:

• The Axillary Nerve Supplies The Deltoid, Giving Sensation Over The Shoulder Area.
  • The Axillary Nerve Originates From The Posterior Cord Of Brachial Plexus
  • Nerve Injury- Weakness Of Shoulder Abduction, Atrophy Of Deltoid And Numbness
  • Nerve Is Commonly Injured Due To Fracture Or Dislocations Of The Shoulder Joint
  • Deltoid Branch Of Thoracoacromial Artery Arises From The Axillary Artery And Supplies The Deltoid Muscle
  • Is Also Gets The Arterial Supply In The Posterior Aspect From The Posterior Humeral Circumflex Artery
  • The Quadrangular Space Is The Space That The Posterior Circumflex Humeral Artery And The Axillary Nerve Pass Through On The Way To The Deltoid Muscle

Injury:

• A Rupture Of Deltoid Can Occur From Sports Or Heavy Manual Labour; Complete Rupture Is Not Common• Rupture Usually Occurs From Open Shoulder Injury
• Rupture Of Deltoid Needs To Be Repaired Or Reconstructed
• Be Aware Of Os Acromiale And The Attachment Of The Deltoid- Surgery Of Os Acromiale May Weaken The Deltoid Muscle

Surgical Principles:

• Total Acromionectomy Is A Bad Procedure It Can Compromise The Deltoid Function- Arthroscopic Procedure Is Better Than Open Shoulder Procedure;
• Danger Of Lateral Approach- Incision From The Tip Of Acromion Extended Distally, And Deltoid Is Split And The Incision Should Not Be More Than 5 Cm Distal To Acromion To Protect The Nerve
• Axillary Nerve Runs Transversely From Posterior To Anterior About 7 Cm Distal To Acromion,
• If Incision Need To Be Extended Distally , As In Fixation Of Proximal Humerus, An Anterolateral Incision Over The Humeral Shaft May Be Used