SHOULDER

Kaan Yücel M.D., Ph.D 19.December.2012 Wednesday

Region of upper limb attachment to the trunk Proximal segment of limb overlaps parts of the trunk (thorax and back) and lower lateral neck.

includes Pectoral ScapularDeltoid regions of the upper limblateral part (greater supraclavicular fossa) of lateral cervical region. Overlies half of the pectoral girdle.

SHOULDER

The pectoral (shoulder) girdle formed by:Scapulae and clavicles completed anteriorly by the manubrium of the sternum (part of the axial skeleton).

Clavicle & scapula [pectoral girdle-shoulder girdle]

Proximal end of humerus

BONE FRAMEWORK OF THE SHOULDER

The superficial muscles of the shoulder trapezius & deltoid muscles

together form the smooth muscular contour over the lateral part of the shoulder.

Connect scapula to trunk & clavicle to arm.

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The 3 joints in the shoulder complex :

Sternoclavicular jointAcromioclavicular jointGlenohumeral joint

JOINTS

Muscles

The two most superficial muscles of the shoulder trapezius and deltoid muscles.

Trapezius attaches scapula & clavicle to the trunkDeltoid attaches scapula & clavicle to the humerus

SUPERFICIAL POSTERIOR AXIOAPPENDICULAR MUSCLES

EXTRINSIC SHOULDER MUSCLESTrapezius & latissimus dorsi

DEEP POSTERIOR AXIOAPPENDICULAR MUSCLESEXTRINSIC SHOULDER MUSCLESLevator scapulae & rhomboids

SCAPULOHUMERAL (INSTRINSIC SHOULDER) MUSCLES

6 scapulohumeral muscles Deltoid, teres major, supraspinatus, infraspinatus, subscapularis, and teres minorpass from scapula to humerus Act on the glenohumeral joint.

All the intrinsic muscles but the deltoid and the subscapularis are muscles of the posterior scapular

region.

Deltoid

Large and triangular in shapeBase attached to the scapula and clavicle Apex attached to the humerus

DeltoidLateral 1/3 of clavicleAcromion Spine of scapula

Deltoid tuberosity of humerus

DeltoidMajor function: Abduction of the arm beyond the initial 15° accomplished by supraspinatus

Clavicular: flexes and medially rotates armAcromial: abduction of armSpinal: extends and laterally rotates arm

DeltoidInnervation: Axillary nerve branch of the posterior cord of the brachial plexus

Thick, triangular muscle Lies on the costal surface of the scapula

Subscapularis

Subscapular fossa

Lesser tubercle of humerus

Primary medial rotator of the arm Adducts the arm.

Joins the other rotator cuff muscles in holding the head of the humerus in the glenoid cavity during all movements of the glenohumeral joint!

Innervation: Superior and inferior subscapular nerves

Subscapularis

http://www.getbodysmart.com/ap/muscularsystem/armmuscles/anteriormuscles/subscapularis/tutorial.html

4 musclespass between the scapula and proximal end of humerus:SupraspinatusInfraspinatusTeres minorTeres major

POSTERIOR SCAPULAR REGION

+ part of long head of the triceps brachii, passes between the scapula and the proximal end of the forearm.

Originate from 2 large fossae, 1 above and 1 below the spine, on the posterior surface of the scapula.

Insert on greater tubercle of the humerus.

Supraspinatus initiates abduction of the arm. Infraspinatus laterally rotates the humerus.

Supraspinatus & Infraspinatus

Supraspinatus & Infraspinatus

A cord-like muscle

Laterally rotates the humerus

Component of the rotator cuff.

Teres minor

Middle part of lateral border of scapula

Inferior facet of greater tubercle of humerus

Posterior surface of inferior angle of scapula

Medial lip of intertubercular sulcus of humerus

Medially rotates and extends the humerus.

Teres major

4 intrinsic shoulder muscles1) Supraspinatus2) Infraspinatus3) Teres minor4) Subscapularis

ROTATOR CUFF MUSCLES

(SITS muscles)

Form a musculotendinous rotator cuff around the glenohumeral joint.

Insertion exception:

ROTATOR CUFF MUSCLES

Supraspinatus Infraspinatus Teres minor

greater tubercle

Subscapularis

lesser tubercle

ROTATOR CUFF MUSCLESFunctional exception:

All except supraspinatus are rotators of the humerus

Supraspinatus, besides being part of the rotator cuff, initiates and assists the deltoid in the first 15° of abduction of the arm.

Suprascapular foramen The route through which structures pass between the base of the neck and the posterior scapular region.

Gateways to the posterior scapular region

Formed by suprascapular notch of scapula & superior transverse scapular (suprascapular) ligament, which converts the notch into a foramen.

The suprascapular nerve passes through the suprascapular foramen;

Suprascapular artery & suprascapular vein follow the same course as the nerve, but normally pass immediately superior to the superior transverse scapular ligament and not through the foramen.

Gateways to the posterior scapular region

Quadrangular spaceaxillary nerve & posterior circumflex humeral artery and vein

Gateways to the posterior scapular region

Triangular space circumflex scapular artery and vein

Gateways to the posterior scapular region

Triangular interval radial nerve ,profunda brachii artery (deep artery of arm)

Gateways to the posterior scapular region

The two major nerves of the posterior scapular region: Suprascapular & Axillary nerves

originate from the brachial plexus in the axilla.

Nerves

Originates where?Base of the neck from superior trunk of brachial plexusReach where through which space? Posterior scapular region through suprascapular foramenWhich muscles innervates ?Supraspinatus muscle & infraspinatus

Suprascapular nerve

Axillary nerveOriginates where?Posterior cord of brachial plexusReach where through which space? From the posterior wall of axilla to posterior scapular region through quadrangular spaceWhich muscles innervates ?Deltoid & teres minor

Axillary nerveCutaneous branch?Superior lateral cutaneous nerve of the armcarries general sensation from the skin over the inferior part of the deltoid muscle.

3 major arteries in the posterior scapular region

Suprascapular artery Posterior circumflex humeral artery Circumflex scapular artery

Arteries

These arteries contribute to an interconnected vascular network around the scapula.

Formation of anastomosis around the surgical neck of humerus

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Posterior circumflex humeral artery anastomoses with anterior circumflex humeral artery and also with branches from:

profunda brachii (brachial artery) suprascapular (subclavian artery) thoracoacromial (axillary artery) arteries

Scapular anastomosis system

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A system connecting each subclavian artery and the corresponding axillary artery, forming an anastomosis around the scapula. It allows blood to flow past the joint regardless of the position of the arm. It includes:transverse cervical artery (subclavian artery)transverse scapular artery (subclavian artery)subscapular artery (axillary artery)branches of thoracic aorta This collateral circulation allows for blood to continue circulating if the subclavian is obstructed.

Movements of the shoulder girdleAbduction of the shoulder is initiated by the supraspinatus; the deltoid can then abduct to 90 degrees. Further movement to 180 degrees (elevation) is brought about by rotation of the scapula upwards by the trapezius and serratus anterior. As soon as abduction commences at the shoulder joint, so the rotation of the scapula begins.

 

 

Principal muscles acting on the shoulder jointAbductorsSupraspinatusDeltoidAdductorsPectoralis majorLattisimus dorsiExtensorsTeres majorLattisimus dorsiDeltoid (posterior fibres)FlexorsPectorali majorCoracobrachialisDeltoid (anterior fibres)

Medial rotatorsPectoralis majorLattisimus dorsiTeres majorDeltoid (anterior fibres)SubscapularisLateral rotatorsInfraspinatusTeres minorDeltoid (posterior fibres)