Shoulder Girdle: Anatomy and Pathology

• The lecture is about the anatomy, physiology, and pathology of the shoulder girdle

Learning Outcomes

• Describe the anatomy and physiology of the shoulder girdle, including bones, joints, and muscles.
• Recognize the radiographic appearances of structures comprising the shoulder girdle
• Comprehend the blood and nerve supply to the shoulder girdle.
• Identify and describe common shoulder girdle pathologies and their radiological features

Shoulder Girdle Bones

• Clavicle
• Scapula
• Proximal Humerus

Shoulder Girdle Joints

• The shoulder girdle contains the following joints, shoulder joint, also known as the Glenohumeral joint.
• Acromio-clavicular joint – AC joint
• Sterno-clavicular joint – SC joint

Clavicle Overview

• The clavicle is an S-shaped long bone.
• It lacks a medullary cavity.
• The clavicle is the first bone to ossify
• The shaft runs horizontally from the base of the neck to the shoulder, lying subcutaneously
• The sternal end is the medial aspect, slightly expanded and quadrangular
• The sternal end articulates with the clavicular notch of the sternum to form the sternoclavicular joint.
• The acromial end is the lateral aspect, slightly expanded and flattened
• The acromial end articulates with the scapula (acromion process) to form the acromioclavicular joint.
• The facet for the first costal cartilage is located in the inferior aspect of the sternal end
• The conoid tubercle is located in the postero-inferior aspect of the acromial end. The coracoclavicular ligament attaches here
• The trapezoid line is located as a ridge extending laterally from the conoid tubercle (coracoclavicular ligament attached)

Clavicle Ossification Centers

• There are typically two primary ossification centers in the shaft, appearing around the 5th week of intrauterine life; these fuse to form one center at 45 days old
• There is also one secondary center, the sternal end appears around age 18/20 years. It fuses with the shaft around 18/25 years

Tuberosity

• A large rounded elevation

Costal

• Associated with the ribs

Lateral

• Away from the midline of the body

Medial

• Nearer the midline of the body

Facet

• A smooth area, usually covered with articular hyaline cartilage

Scapula Overview

• The scapula is a flat and triangular shaped bone
• The scapula sits on the postero-lateral aspect of the bony thorax
• The scapula extends from the 2nd-7th ribs
• Acromion process articulates with the acromial end of the clavicle to form the acromioclavicular joint
• The Glenoid Cavity articulates with the Head of the Humerus to form the glenohumeral or shoulder joint

Scapula Ossification Centers

• There is one primary ossification center which appears near the glenoid cavity during the 8th week of intrauterine life
• There are seven secondary centers that fuse at 20 years old

Spine (Posterior Aspect)

• A narrow ridge that divides the upper ⅓ from lower ⅔.
• The spine allows for attachment for the trapezius and deltoid muscles.

Supraspinous fossa (Posterior Aspect)

• A depression above the spine, allowing for the supraspinatus muscle

Infraspinous fossa (Posterior Aspect)

• A depression below the spine, allowing for the infraspinatus muscle

Acromion Process (Posterior Aspect)

• The lateral aspect of the spine is the articular facet for clavicle.

Medial Border (Posterior Aspect)

• also known as the vertebral border

Lateral Border (Posterior Aspect)

• also known as the axillary border. Allows for teres minor attachment

Subscapular fossa (Anterior Aspect)

• Depression for the subscapularis muscle

Scapular notch (Anterior Aspect)

• The lateral end of the superior border

Coracoid process (Anterior Aspect)

• The attachment point for the coracoclavicular ligament, short head of biceps, & coracobrachialis muscles

Glenoid Cavity (Lateral Aspect)

• A pear shaped depression for the head of humerus

Supraglenoid tubercle (Lateral Aspect)

• A tendon of the long head of biceps muscle

Infra-glenoid tubercle (Lateral Aspect)

• A tendon of long head of triceps muscle

Proximal Humerus

• Humerus is a long bone, and the largest bone in the Upper Limb
• The head articulates with the Glenoid Cavity of Scapula, also known as the Glenohumeral or shoulder joint
• There is a tendon for the biceps through bicipital groove

Humerus Ossification

• The Primary ossification center for the shaft appears during the 8TH week of Intra-uterine Life.
• The Upper end has secondary centers
• Head of Humerus appears around age 6 months
• Greater tuberosity 1-2 years old
• Lesser tuberosity 4-5 years old
• Fuses together around 6 years old
• Fuses With Shaft around 18-20 years old

The Shoulder Joint (Glenohumeral Joint)

• The shoulder joint consists of bony articular surfaces
• The head of humerus articulates with glenoid cavity of scapula
• Articular surfaces are covered with articular hyaline cartilage
• The shoulder joint is the synovial ball and socket
• The shoulder joint contains fibrous capsule, synovial membrane, articular hyaline cartilage, synovial fluid and is multiaxial
• The Shoulder Joint has a wide range of movement (ROM) and is complex and multi tasking
• The Shoulder Joint itself is WEAK; it is strengthened via muscles, tendons & ligaments
• Movements of this JOINT include, Abduction, Adduction, Flexion, Extension, External rotation, Internal Rotation, circumduction and hyperflexion and extension

Fibrous Capsule

• The fibrous capsule surrounds the gleno-humeral joint in the form of a cylindrical sleeve.
• The capsule is attached medially to the rim of the glenoid cavity and laterally to the anatomical neck of humerus
• Finally, the capsule is loose inferiorly to allow for movement

Intracapsular Structures

• GLENOID RIM / LABRUM - fibrocartilaginous rim around the glenoid cavity to deepen the socket
• Tendon of Long Head of Biceps

Synovial Membrane

• Lines fibrous capsule
• Secretes synovial fluid
• The subscapular Bursa lies between the joint & subscapularis muscle
• The subacromial Bursa lies between shoulder joint & acromion process

Bursa

• A small fluid filled sac
• Lined by synovial membrane
• Between tendons and bones
• Between muscles and bones
• Between ligaments and bones
• Between skin and bones

Shoulder Joint Ligaments

• Shoulder Ligaments strengthen the shoulder joint
• Glenohumeral Ligaments(superior, middle, inferior)
• Coracohumeral which arises from coracoid process of scapula to the greater tuberosity of the humerus
• Transverse Humeral - Lies between the lesser and the greater tuberosities of humerus & maintains the tendon of the long head of biceps in the intertubercular sulcus (bicipital groove)

Shoulder Tendons

• The rotator cuff reinforces the fibrous capsule
• SUPRASPINATUS is attached to superior aspect of greater tuberosity of humerus
• INFRASPINATUS attached to middle of greater tuberosity of humerus
• TERES MINOR attached to the lower posterior aspect of the greater tuberosity
• SUBSCAPULARIS attached to anterior aspect of lesser tuberosity
• Tendons are arranged in a nearly complete circle around the joint

Shoulder Muscles

• There are 30 muscles in the shoulder complex
• Their main functions are to move and stabilize the scapula; shoulder joint motion and supporting the scapula on the thorax.
• Several of the main muscles include: pectoralis major, the trapezius, the deltoid and muscles of the rotator cuff.

Pectoralis Major

• The pectoralis muscles (major and minor) run from the front of the chest to the shoulder.
• The pectoralis major muscle is the large muscle of the chest. It helps to bring the arm toward the body on the side and in front of the body from the sides and it originates from the clavicle and sternum and inserts into the anterior surface of the proximal humerus
• It acts as an adductor and performs internal rotation as a broad muscle covering upper part of chest.
• Inserted into intertubercular sulcus of the humerus producing adduction & medial rotation of arm at shoulder. It flexes and extends arm at shoulder joint

Pectoralis Minor

• A small muscle that arises from 3rd-5th ribs and is inserted into coracoid process of scapula and assists in moving the scapula laterally, forward and rotation

Trapezius

• The biggest muscle of the neck
• Runs from the neck and spine out to the shoulder.
• A large muscle that moves the shoulder blade up and down, as well as pointing the shoulder blade toward the back as a large muscle that arises from external occipital protuberance & spines of C7 and T1-12
• It inserts into spine & acromion process of scapula & into the clavicle and elevates the clavicle, rotates, elevates, depresses and moves scapula medially and backwards

Deltoid

• The biggest muscle in the shoulder, running over the shoulder joint down to the arm and arises from acromial extremity of clavicle & from the acromion process & spine of scapula.
• Parts come from the back, the top and the front of the shoulder and run to the top of the outer part of the arm
• The Deltoid flexes, extends, medially rotates and laterally rotates, also abducts the arm.

Rotator cuff Muscles

• Comprised of four muscles (supraspinatus, infraspinatus, teres minor and subscapularis) and their tendons
• Rotator cuff muscles cloaks the anterior, superior and posterior surfaces of the humeral head and provide stability to the shoulder joint as well as assisting in abduction and rotation of the humerus.
• SUPRASPINATUS arises from supraspinous fossa of scapula & is inserted into greater tuberosity of the humerus aiding shoulder joint
• The deltoid muscle in abduction of the arm at shoulder joint.
• SUBSCAPULARIS arises from the subscapular fossa inserted into lesser tuberosity of humerus, medially rotates the arm at the shoulder joint
• INFRASPINATUS arises from infraspinous fossa of the scapula. Inserted into greater tuberosity of humerus. Laterally rotates the arm and adducts arm at shoulder joint.
• TERES MINOR arises from lateral border of scapula and inserts into the greater tuberosity of humerus. Laterally rotates the arm and extends and adducts arm at shoulder joint
• TERES MAJOR arises from inferior angle of scapula. Inserted into intertubercular sulcus of humerus and extends arm at shoulder joint, assists in adduction and rotation of arm medially at shoulder jont
• LATISSIMUS DORSI arises from lower 6 thoracic vertebrae & is inserted into intertubercular sulcus of humerus. Extends adducts & medially rotates the arm by drawing arm downward and backward.
• SERRATUS ANTERIOR arises from outer surfaces of upper eight ribs and inserted into the vertebral border and inferior angle of scapula; rotates scapula upwards and laterally.
• CORACOBRACHIALIS arises from coracoid process of scapula and is inserted into medial border of humerus, flexes and adducts arm.
• The glenohumeral Main muscles of internal rotation are, Pect major, Latissimus dorsi, Subscapularis, Teres major and Deltoid
  • Main muscles for flexion, Pect major and Deltoid (ant fibres)
  • Main muscles for extension, deltoid (post fibres) and Latissimus dorsi
  • Main muscles for abduction, Supraspinatus and Deltoid (middle fibres)
  • Main muscles for adduction, Pect major and Latissimus dorsi
• The main muscles of external rotation are, Infraspinatus, Teres minor and Deltoid (post fibres)

Shoulder joint: Blood and Nerve Supply

• Blood supply is from Branches of the axillary & subclavian arteries
• Nerve supply is from Suprascapular, axillary and lateral pectoral nerves

Acromioclavicular Joint (ACJ)

• A synovial plane joint, allowing only a gliding movement.
• The acromial end of clavicle articulates with medial border of Acromion process of scapula, with articular surfaces covered with fibro-cartilage
• FIBROUS CAPSULE is ATTACHED TO lateral end of CLAVICLE & medial aspect of ACROMION PROCESS and SYNOVIAL MEMBRANE lines FIBROUS CAPSULE & secretes SYNOVIAL FLUID which lubricates the joint as INTRACAPSULAR STRUCTURE being an ARTICULAR DISC IN UPPER ASPECT of JOINT
• BLOOD SUPPLY is from Suprascapular Artery and the NERVE SUPPLY is from Suprascapular & lateral pectoral nerves

Acromioclavicular Joint Ligaments

• Acromioclavicular
• Coracoclavicular

Sternoclavicular Joint (SCJ)

• The SCJ is a Synovial Saddle Joint facilitating Elevation, Depression, Anterior & Posterior movement in horizontal direction and Circumduction
• CLAVICULAR NOTCH of STERNUM and 1st Costal cartilage articulates with STERNAL END of CLAVICLE with ARTICULAR SURFACES COVERED WITH FIBROCARTILAGE
• FIBROUS CAPSULE is attached to STERNAL END of CLAVICLE & LATERAL ASPECT of MANUBRIUM STERNI, and it divides joint into 2 parts. It also has the INTRACAPSULAR STRUCTURE as an ARTICULAR DISC, dividing joint into 2 parts.
• BLOOD SUPPLY that included Internal Mammary Arteries & Suprascapular Arteries and the main NERVE SUPPLY is from the Anterior Supraclavicular Nerve

Sternoclavicular Joint (SCJ) Ligaments

• Anterior & Posterior Sternoclavicular
• Interclavicular
• Costoclavicular

Shoulder Pathology

• Osteoarthritis
• Rheumatoid arthritis
• Fractures
• Dislocation/Subluxation
• Rotator Cuff Injuries
• Frozen Shoulder
• Tendonitis/ Tendinosis
• Calcified Tendons
• Congenital abnormalities
• Cancer -primary/secondary

Osteoarthritis

• Presents with a narrowing of JT space
• Characterized by Sclerosis and OSTEOPHYTES
• Presents as POSTERIOR SUBLUXATION of GLENOID on HUMERUS

Rheumatoid Arthritis

• Presents as DIFFUSE OSTEOPENIA.
• Characterized by SYMMETRICAL JT SPACE NARROWING and PERIARTICULAR EROSIONS

Clavicle Fractures

• One of the most common fractured bones in the body
• Clavicle transmits forces from the upper extremity to the trunk
• Excessive forces are exerted, such as FOOSH or fractured clavicle may occur as treated by sling/ surgery
• Clavicle fractures happen due to trauma with the most common site in the middle third.
• Clavicle fractures also due to
  • Direct blow to the clavicle -Falling on an outstretched arm -Newborn babies can fracture clavicle passing through the birth canal

Scapula Fractures

• Though rare due to the bone’s nature of being embedded in muscle
• Fractures are usually caused by direct blow & can occur at the body, neck, acromion & coracoid processes of scapula,
• Treated by sling/surgery

Upper Humeral Fractures

• Surgical Neck is so named because of its liability to fracture from FOOSH.
• Common in Elderly, treated by sling/surgery
• Surgical neck fracture which is the most common fracture of proximal humerus is extra capsular has an adequate blood supply and relatively low incidence of Avascular Necrosis (AVN).
• The Anatomic neck fracture has a higher incidence of AVN.

Shoulder Dislocations

• The glenohumeral joint is the most mobile joint in the body where the head of the humerus sits in the shallow cup of the glenoid fossa stabilized mostly by soft tissue, including the glenoid labrum and rotator cuff muscles.
• High inheritability accounts for Glenohumeral dislocations classified as, Anterior (95 percent), posterior (4 percent) and, rarely, Inferior or superior (1 percent)

Anterior Dislocation

• To be reduced and immobilized most common being an MOST COMMON DISLOCATION,
• The shoulder is characterized via the Anterior Dislocation that ANTERIOR DISLOCATION OCCURS WHEN ARM IS EXTERNALLY ROTATED, PUSHED FROM BEHIND, ABDUCTED or EXTENDED with POSTERIOR FORCE,

Posterior Dislocation

• Is the Less common dislocation around 4% that is must be considered due to alternative mechanisms for injury, Ask about history of seizures and ECT therapy. Electric shock may also cause a posterior dislocation.
• It also occurs because of axial loading on the internally rotated, adducted arm, characterized by Direct blow on the anterior aspect of the shoulder
• Can be hard to demonstrate a posterior dislocation on an AP with possible "Rim sign"

Recurrent Shoulder Dislocation

• HILL-SACH's Lesion - compression defect on Humeral Head
• BANKART Lesion (fracture) - tear affecting inferior rim of Glenoid Cavity (glenoid labrum)

Lipohaemarthrosis

• Refers to a condition in which an intra-articular fracture has allowed fat to be released from bone marrow into the joint
• Then the fat floats on the blood in the joint and results in a fat/blood "fluid level".
• Lipohaemarthrosis is one of the few reasonably reliable soft tissue signs of fracture

AC Joint Injuries

• SUBLUXATION is a partial dislocation often treated with a sling and caused by a fall on shoulder as result in damage of the Coraco-clavicular ligament torn,
• As DISLOCATION is caused a result torn coraco-clavicular ligament. Which may needs internal fixation and is by a falling action

Sternoclavicular Joint Dislocation

• Considered RARE and has the characteristic as an effect of Fall on Shoulder forcing medial end of clavicle upwards and is reduced under anaesthetic and immobilized

Rotator Cuff Injuries

• Where the rotator cuff is a group of muscles and tendons connecting the humerus with the scapula
• The rotator cuff consists of four muscles: supraspinatus, infraspinatus, teres minor, and the subscapularis muscle where main source is Overuse...repetitive stretching of the rotator cuff may result in tendinitis and tearing
• The rotator cuff also tears because caused suddenly by severe shoulder traumas such as and 3 Rotator Cuff Tendinitis (shoulder tendinitis/shoulder bursitis)...Inflammation of Rotator Cuff Tendons

Frozen Shoulder

• Is due to adhesions in the capsules that is caused by Lack of use due to chronic pain; Bands of tissue that grow in the joint and restrict motion
• The shoulder actually "freezes up" due to the severe inflammation of the joint capsule as caused due to Lack of use due to chronic pain caused as result of fluid loss.

Tendinosis

• The degenerative condition of a tendon mainly caused in the overuse of damage action has resulting pain as result.

Tendinitis.

• Is from a resulting inflammation causes by excessive overuses or infection in general.