ANATOMY & APPLIED ASPECTS OF SHOULDER JOINT

PMR PG Teaching- August 2016

Dr. Jimy Jose Resident, Deptt. Of PMR

SMS Medical College, Jaipur

OSTEOLOGY

The bone framework of the shoulder consists of: the clavicle and scapula, which form the pectoral girdle

(shoulder girdle)

the proximal end of the humerus.

Clavicle• The clavicle is the only bony attachment between the trunk and the upper limb. • It is palpable along its entire length and has a gentle S-shaped contour• forward-facing convex part medial and • forward-facing concave part lateral.

The acromial (lateral) end of the clavicle is flat The sternal (medial) end is more robust and somewhat quadrangular in shape. the surfaces and margins of the clavicle are roughened by the attachment of muscles that

connect the clavicle to the thorax, neck, and upper limb. The superior surface is smoother than the inferior surface.

Scapula

The scapula is a large, flat triangular bone with:

• three angles (lateral, superior, and inferior);• three borders (superior, lateral, and medial);• two surfaces (costal and posterior); and• three processes (acromion, spine, and coracoid process)

Posterior view of right scapula.

Anterior view of scapula

• A large triangular-shaped roughening (the infraglenoid tubercle) inferior to the glenoid cavity is the site of attachment for the long head of the triceps brachii muscle.

• The lateral angle of the scapula is marked by a shallow, somewhat comma-shaped glenoid cavity,

• which articulates with the head of the humerus to form the glenohumeral joint

Lateral viewof scapula

• supraglenoid tubercle is located superior to the glenoid cavity and is the site of attachment for the long head of the biceps brachii muscle.

• A prominent spine subdivides the posterior surface of the scapula into a small, superior supraspinous fossa and a much larger, inferior infraspinous fossa.

• The acromion, which is an anterolateral projection of the spine, arches over the glenohumeral joint and articulates, via a small oval facet on its distal end, with the clavicle.

• Unlike the posterior surface, the costal surface of the scapula is unremarkable, being characterized by a shallow concave subscapular fossa over much of its extent .

• The costal surface and margins provide for muscle attachment, and the costal surface, together with its related muscle (subscapularis), moves freely over the underlying thoracic wall.

• The lateral border of the scapula is strong and thick for muscle attachment,

• medial border and much of the superior border is thin and sharp.

The superior border is marked on its lateral end by:

• the coracoid process, a hook-like structure that projects anterolaterally and is positioned directly inferior to the lateral part of the clavicle

• the small but distinct suprascapular notch, which lies immediately medial to the root of the coracoid process.

JOINTSFour joints Within the Shoulder Complex:

1. Sternoclavicular joint

2. Acromioclavicular joint

3. Scapulothoracic joint

4. Glenohumeral joint

1.Sterno

Clavicular

2.Acromio

clavicular

3.Gleno

humeral

4.Scapulothoracic joint

The sternoclavicular joint

is surrounded by a joint capsule and is reinforced by four ligaments:

anterior and posterior sternoclavicular ligaments are anterior and posterior, respectively, to the joint

the costoclavicular ligament links the proximal end of the clavicle to the first rib and related costal cartilage.

interclavicular ligament links the ends of the two clavicles to each other ; and to the superior surface of the manubrium of sternum

STERNOCLAVICULAR JOINT

ACROMIOCLAVICULAR JOINT It allows movement in the anteroposterior and vertical planes together with some axial rotation.

surrounded by a joint capsule and is reinforced by LIGAMENTS:

acromioclavicular ligament passing between adjacent regions of the clavicle and acromion

coracoclavicular ligament-• between the coracoid process

of the scapula and the inferior surface of the acromial end of the clavicle

• anterior trapezoid ligament (which attaches to the trapezoid line on the clavicle) & a posterior conoid ligament (which attaches to the related conoid tubercle)

GLENOHUMERAL JOINT

synovial ball and socket articulation between the head of the humerus and the glenoid cavity. Multiaxial wide range of movements provided at the cost of skeletal stability Joint stability - rotator cuff muscles, the long head of the biceps brachii , bony processes, extracapsular ligaments

The glenoid cavity is deepened and expanded peripherally by the glenoid labrum

Superiorly, this labrum is continuous with the tendon of the long head of the biceps brachii muscle, which attaches to the supraglenoid tubercle and passes through the articular cavity

The synovial membrane

• attaches to the margins of the articular surfaces

• loose inferiorly. (redundant region accommodates abduction of the arm)

• also folds around the tendon of the long head of the biceps brachii and extends along the tendon as it passes into the intertubercular sulcus.

• protrudes through apertures in the fibrous membrane to form bursae, which lie between the tendons of surrounding muscles and the fibrous membrane.

The most consistent of these is the subtendinous bursa of subscapularis, between the subscapularis muscle and the fibrous membrane.

Other bursae are associated with the joint:

• between the acromion (or deltoid muscle) and supraspinatus muscle (or joint capsule) (the

subacromial or subdeltoid bursa)

• between the acromion and skin• between the coracoid process and the

joint capsule• in relationship to tendons of muscles

around the joint (coracobrachialis, teres major, long head

of triceps brachii, and latissimus dorsi muscles).

All these synovial structures reduce friction between the tendons and adjacentjoint capsule and bone.

The fibrous membrane of the joint capsule attaches to: the margin of the glenoid cavity outside the attachment of the glenoid labrum The long head of the biceps brachii muscle the anatomical neck of the humerus – the medial attachment occurs

more inferiorly than the neck and extends onto theshaft. In this region, the fibrous membrane is also loose or folded in the anatomical position. This redundant area of the fibrous membrane accommodates abduction of the arm.

The fibrous membrane of the joint capsule is thickened by: • Glenohumeral Ligamentssuperior, middle, and inferior glenohumeral ligaments, which pass between the

superomedial margin of the glenoid cavity to the lesser tubercle• The Coracohumeral Ligamentsuperiorly between the base of the coracoid process and the greater tubercle of

the humerus• The Transverse Humeral Ligamentbetween the greater and lesser tubercles of the humerus -this holds the

tendon of the long head of the biceps brachii muscle in the intertubercular sulcus

Scapulothoracic Joint not a true joint - rather a point of contact

between the anterior surface of the scapula and the posterior-lateral wall of the thorax

the scapula is typically positioned between the second and the seventh rib, with the medial border located about six (6) cm lateral to the spine

SURFACE ANATOMY

SURFACE ANATOMY

SURFACE ANATOMY

SURFACE ANATOMY

Some muscles of the shoulder connect the scapula and clavicle to the trunk.

• The trapezius• Levator scapulae• Rhomboids

muscles connect the clavicle, scapula, and body wall to the proximal end of the humerus.

• pectoralis major• pectoralis minor• latissimus dorsi• teres major• deltoid

TRAPEZIUS AND DELTOID

• The two most superficial muscles of the shoulder • Together, they provide the characteristic contour of the shoulder

• the trapezius attaches the scapula and clavicle to the trunk.• the deltoid attaches the scapula and clavicle to the humerus.

• Both the trapezius and deltoid are attached to opposing surfaces and margins of the spine of the scapula, acromion, and clavicle.

• The scapula, acromion, and clavicle can be palpated between the attachments of trapezius and deltoid.

Muscle Origin Insertion Innervation Function

• Together, the left and right trapezius muscles form a diamond or trapezoid shape, from which the name is derived.

• The accessory nerve can be evaluated by testing the function of the trapezius muscle. This is done by asking patients to shrug their shoulders against resistance.

Muscle Origin Insertion Innervation Function

Muscle Origin Insertion Innervation Function

Muscle Origin Insertion Innervation Function

Muscle Origin Insertion Innervation Function

Muscle Origin Insertion Innervation Function

four rotator cuff muscles-

supraspinatusInfraspinatusTeres minor

Subscapularis

• Tendons of the rotator cuff muscles (the supraspinatus, infraspinatus, teres minor, and subscapularis muscles) blend with the joint capsule and form a musculotendinous collar that surrounds the :

posterior, superior, and anterior aspects of the glenohumeral joint

• This cuff of muscles stabilizes and holds the head of the humerus in the glenoid cavity of the scapula without compromising the arm's flexibility and range of motion.

• The tendon of the long head of the biceps brachii muscle passes superiorly through the joint and restricts upward movement of the humeral head on the glenoid cavity.

Blood supply:ant & post circumflex humeral vessel.Suprascapular vessel.Subscapular vessel

Vascular supply of Glenohumeral joint branches of the anterior and posterior circumflex humeral and suprascapular arteries.

innervated by branches from the posterior cord of the brachial plexus, and from the suprascapular, axillary nerves.

Nerve supply:axillary nervemusculo cutaneous nervesuprascapular nerve

Internal rotation Subscapularislatissimus dorsianterior fiber of the deltoidpectoralis majorteres major.

External rotators -Infraspinatusteres minorposterior fibers of the deltoid.

Abductors DeltoidSupraspinatustrapezius,serratus anterior.

Adduction SubscapularisInfraspinatusteres minorPectoralisLatissimus dorsiteres major

Flexion of the arm Pectoralis majorbiceps brachiiand anterior deltoid

Extensionposterior deltoidteres majorLatissimus dorsi

The muscles noted previously can be divided into functional groups

ReferencesClinical Anatomy Snell’sGray’s Anatomy

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