Shoulder & Brachial Plexus PDF

Pectoral Girdle, Shoulder, Axilla, & Brachial Plexus  PAS-508  Dr. Rhonda Hazell  Associate Professor  CHHS  “SHOULDER” “ELBOW” The pectoral girdle attaches the “WRIST” upper limb to the axial skeleton Pectoral girdle (a...

Pectoral Girdle, Shoulder, Axilla, & Brachial Plexus  PAS-508  Dr. Rhonda Hazell  Associate Professor  CHHS  “SHOULDER” “ELBOW” The pectoral girdle attaches the “WRIST” upper limb to the axial skeleton Pectoral girdle (anterior) Scapula (shoulder blade)  The pectoral girdle has evolved to maximize mobility of the upper limb, in contrast to… …the pelvic girdle, which has evolved to maximize stability in weight bearing by the lower limbs  The pectoral girdle consists of... CLAVICLE SCAPULA – The “collar bone” – The “shoulder blade” – The only bony connection – Glides freely on the between upper limb and posterior thoracic wall, axial skeleton (sternum) moving the pectoral girdle and the upper – A bony strut suspending the limb upper limb and allowing it to – Articulates with the swing clear of the trunk clavicle at the – Develops early via intra- acromioclavicular membranous ossification joint – The earliest postcranial – Articulates with the bone to initiate ossification proximal humerus at the glenohumeral joint The CLAVICLE acts a bony strut providing the only direct bony connection between the upper limb and the axial skeleton – one of several reasons that the clavicle is the most frequently fractured bone in the body The Clavicle – a bony strut maintaining the normal relations of upper limb and thorax Lateral superior (acromial Medial end) (sternal) end - broad & flat - articulates - rounded with scapula - articulates with the manubrium inferior Impression for the COSTOCLAVICULAR LIGAMENT The clavicle is the most frequently fractured bone in the body, due to… The bone’s role as a strut between arm and axial skeleton Note the typical displacement of the limb following clavicular fracture Its early ossification in skeletal development Its subcutaneous position Its sinuous shape The changing cross-sectional shape of the middle third We will shortly consider the STERNOCLAVICULAR and ACROMIOCLAVICULAR joints Acromioclavicular joint Sternoclavicular joint The scapula Superior Superior Acromion Dorsal surface angle A triangular body - Three borders - Three angles - One spine continuing laterally as the Lateral acromion process angle Medial (Vertebral) Lateral (Axillary) Inferior angle The scapula Dorsal surface The spine divides the body into two fossae Both the SCAPULAR SPINE and the ACROMION PROCESS may be palpated The scapula Ventral (costal) surface GLENOID FOSSA The CORACOID PROCESS is also palpable  At the lateral angle, the GLENOID FOSSA provides a shallow, oval articular surface, deepened somewhat by a cartilaginous LABRUM, for receipt of the GLENOID FOSSA  The HEAD OF THE HUMERUS articulates with the GLENOID FOSSA to form the GLENOHUMERAL JOINT GLENOHUMERAL JOINT PROXIMAL HUMERUS (anterior view) Head Greater tubercle Lesser tubercle Intertubercular (Bicipital) sulcus PROXIMAL HUMERUS (posterior view) The “Shoulder” is a misnomer… SCAPULOTHORACIC “JOINT” – Between the ventral (costal) surface of the scapula and the posterior thoracic wall – Movement results from contraction of extrinsic shoulder (thoracoappendicular) muscles GLENOHUMERAL JOINT – A multiaxial (ball & socket joint) between glenoid fossa of the scapula and the head of the humerus – Movement result from contraction of intrinsic shoulder (scapulohumeral) muscles ACROMIOCLAVICULAR JOINT STERNOCLAVICULAR JOINT SUBACROMIAL SPACE  AC JOINT GLENO- SC HUMERAL JOINT JOINT The SCAPULOTHORACIC “JOINT” permits the scapula to glide along the thorax on a curved surface of loose connective tissue SCAPULOTHORACIC MOVEMENTS Elevation and Depression Protraction and Retraction Upward and Downward Rotation Repositions the glenoid fossa to facilitate the full range of active motion at the “shoulder”  The STERNOCLAVICULAR JOINTS are quite strong The joints permit clavicular movements associated with the movements at the scapulothoracic joint The Anterior Why is the sternoclavicular Posterior ligament is weak sternoclavicular ligament much stronger? The ACROMIOCLAVICULAR (AC) joint is the site of SHOULDER SEPARATION injuries… as the capsular AC LIGAMENT is very weak The two portions of the CORACOCLAVICULAR LIGAMENT maintain the integrity of this plane synovial joint, and effectively suspend the scapula from the clavicle The impressive mobility of the GLENOHUMERAL JOINT is a product of two factors: 1 - The thin, lax articular capsule 2- The incongruity of the bony articular surfaces Mobility comes at the price of instability – Four muscles arising from the body of the scapula contribute to formation of the “ROTATOR CUFF” These muscles and tendons help maintain the integrity and stability of the glenohumeral joint GLENO- HUMERAL MOVEMENTS The Brachial Plexus is the source of virtually all nerves innervating the upper extremity Named peripheral nerves arising from the plexus typically contain fibers derived from at least two adjacent ventral rami of lower cervical or upper thoracic spinal nerves Recall that the ventral rami are the larger of the two branches arising from each spinal nerve Recall that ventral rami contain both somatic afferent and somatic efferent fibers The nerves arising from the brachial plexus are often named for their peripheral distribution Let’s build the (right) Brachial Plexus together! The plexus also has 11 COLLATERAL (PRETERMINAL) branches Proximal 3 5 Distal 6 3 5 The RIGHT brachial plexus ROOTS and TRUNKS are essentially SUPRACLAVICULAR structures DIVISIONS and CORDS are essentially INFRACLAVICULAR structures The AXILLARY FOSSA is a pyramidal space The BASE is formed by the skin of the armpit The APEX is the interval between the clavicle and the first rib BASE Anterior wall - Pectoralis major and minor Medial wall - Serratus anterior and lateral ribcage Lateral wall - Intertubercular (bicipital) sulcus Posterior wall - Subscapularis, teres major and latissimus dorsi tendon The pectoral muscles and the overlying skin form the anterior axillary fold  Anterior Wall Pectoralis major Pectoralis minor Medial Wall Lateral wall G.T Serratus anterior Intertubercular L.T. and lateral (bicipital) sulcus thoracic wall Posterior wall Subscapularis Teres major Latissimus dorsi tendon Within the AXILLARY FOSSA, embedded in, and surrounded by both an abundance of fat and a fascial sheath, are: Axillary artery and vein Axillary lymph nodes Infraclavicular elements of the brachial plexus The brachial plexus is formed ROOTS – ventral rami by fibers from ventral rami of FIVE spinal nerves Because the upper limbs develop as buds arising from the venterolateral body wall adjacent to the CAUDAL CERVICAL and UPPER THORACIC segments of the embryo (somites) toward the end of the fourth week of development The dermatomes of the upper limb also reflect the limb’s origin from the venterolateral body wall adjacent to the caudal cervical and upper thoracic segments of the embryo C4 – C5 - Lateral aspect of arm C6 - Lateral aspect of forearm, hand and radial two digits C7- Middle finger and middle of hand C8 - Ulnar two digits and medial aspect of hand and wrist T1 - Medial aspect of forearm, elbow and lower arm T2 - The brachial plexus is formed by fibers ROOTS – ventral rami from ventral rami of FIVE spinal nerves There is a PROXIMAL - DISTAL GRADIENT OF INNERVATION C5 by the SOMATIC MOTOR fibers C6 in the brachial plexus! C7 C5-C6 fibers innervate C8 Fibers from intermediate rami innervate T1 C8-T1 fibers innervate  ROOTS – ventral rami The DORSAL SCAPULAR nerve arises from C5 Innervates the rhomboids and C5 levator scapulae C6 TWO COLLATERAL BRANCHES C7 OF THE BRACHIAL PLEXUS ARISE DIRECTLY FROM THE ROOTS C8 T1  ROOTS – ventral rami The DORSAL SCAPULAR nerve arises from C5 Innervates the rhomboids and C5 levator scapulae C6 TWO COLLATERAL BRANCHES C7 OF THE BRACHIAL PLEXUS ARISE DIRECTLY FROM THE ROOTS C8 The LONG THORACIC nerve T1 arises from C5,C6,C7 SERRATUS ANTERIOR The serratus is weakened or paralyzed by a destructive lesion of the LONG THORACIC NERVE resulting from either trauma to the lateral thorax or mastectomy Patient will present with a medially “WINGED SCAPULA” and experience difficulty in raising the limb fully above the head Scapular rotation is required for both abduction and flexion of the arm at the “shoulder” beyond the initial 30 degrees… Scapular rotation is produced by a number of distinct force couples… LOWER TRAPEZIUS LATISSIMUS DORSI Also PECTORALIS MINOR  SCAPULOTHORACIC MOVEMENTS 1. Elevation and Depression Upper Trapezius Pectoralis minor Levator Scapulae Latissimus dorsi Lower Trapezius 2. Protraction and Retraction (Abduction) (Adduction) Serratus anterior Rhomboids Pectoralis minor Middle Trapezius The roots of the plexus ROOTS contribute distally to the TRUNKS formation of 3 TRUNKS The superior (upper) trunk arises from The middle trunk arises from The inferior (lower) trunk arises from  ROOTS TRUNKS TWO COLLATERAL BRANCHES of the brachial plexus arise directly from the TRUNKS The NERVE TO SUBCLAVIUS SUBCLAVIUS The SUPRASCAPULAR nerve ROOTS TRUNKS arises from C5,C6 TWO COLLATERAL BRANCHES of the brachial plexus arise directly from the TRUNKS The NERVE TO SUBCLAVIUS arises from C5,C6 Each TRUNK then splits into two DIVISIONS:  ROOTS TRUNKS ANTERIOR DIVISION DIVISIONS fibers form peripheral nerves innervating ANTERIOR muscles A P of arm, forearm A and palmar hand P P A POSTERIOR DIVISION fibers form peripheral nerves innervating POSTERIOR muscles of arm and forearm FROM A FUNCTIONAL PERSPECTIVE… Fibers from ANTERIOR DIVISIONS will supply Fibers from POSTERIOR DIVISIONS will primarily supply Anterior division fibers from the superior ROOTS TRUNKS & middle trunks form the DIVISIONS Anterior division fibers CORDS from the inferior trunk form the A P A P P Posterior A division fibers arising from ALL three trunks converge to DIVISION fibers form the in turn form three CORDS Cords are named on the basis of their anatomical relationship to the AXILLARY ARTERY when the upper limb is in the anatomical position AXILLARY ARTERY The axillary artery continues the SUBCLAVIAN ARTERY after it entered the apex of the axilla by passing over the first rib Deep in the neck, the roots and trunks of the brachial plexus, as well as the subclavian artery, pass between the anterior and middle scalene muscles AXILLARY ARTERY Root and trunks of the plexus are subject to compression resulting from hypertrophy or pathology of the scalenes as they transit the SCALENE TRIANGLE C5 – T1 VENTRAL RAMI Each SCALENE TRIANGLE This interval is bounded by the transmits the major ANTERIOR and neuro-vascular MIDDLE SCALENES MS elements supplying and the the upper limb FIRST RIB AS MS AS Symptoms of SCALENE INTERVAL SYNDROME Note that the Subclavian VEIN A cool, pale upper does NOT pass limb with through the diminished pulses interval! Sensory and motor deficits in the upper limb… The contents of the scalene interval may also be compressed by an anomalous CERVICAL RIB Each cord will give rise to a variable number of collateral nerves before splitting into TWO terminal branches The LATERAL CORD… … has only ONE collateral branch The LATERAL PECTORAL nerve arises from C5,C6,C7 T A L The MEDIAL CORD… … has THREE collateral branches D E M The MEDIAL PECTORAL nerve arises from C8,T1 PECTORALIS MAJOR…..has three heads of origin… …all three heads insert via a common tendon to the proximal humerus Contraction of the muscle causes the freely mobile arm to move at the GLENOHUMERAL JOINT Flexion Reflection of the PECTORALIS MAJOR exposes the smaller PECTORALIS MINOR The MAMMARY GLAND lies immediately superficial to the PECTORALIS MAJOR The female breast is made up of 15 to 25 lobes, each opening separately onto the nipple through a lactiferous duct Connective tissue partitions called suspensory (Cooper's) ligaments extend from the pectoralis major fascia, through the mammary layer, to the deep surface of the skin Breast carcinoma commonly invades these ligaments, causing their contracture, which may dimple the skin when the patient is in the upright position Lymphatic drainage of the breast is directed primarily towards the The MEDIAL CORD… … has THREE collateral branches D E M MEDIAL PECTORAL MEDIAL BRACHIAL CUTANEOUS nerve arises from C8, T1 MEDIAL ANTEBRACHIAL CUTANEOUS nerve arises from C8, T1  THE POSTERIOR CORD…..has three collateral branches whose exact order of branching is variable T. The LOWER S SUBSCAPULAR O P nerve arises from C5,C6 The UPPER SUBSCAPULAR nerve arises from C5, C6  THE POSTERIOR CORD…..has three collateral branches whose exact order of branching is variable T. The LOWER S SUBSCAPULAR O P nerve The UPPER SUBSCAPULAR nerve The THORACODORSAL nerve arises from C6,C7,C8  Latissimus dorsi Extends Adducts Internally rotates the arm at the glenohumeral joint After giving rise to the collateral nerves, each cord terminates by splitting into TWO The POSTERIOR CORD…..has two terminal branches T. S O P Innervates: deltoid teres minor skin over the lateral arm glenohumeral joint  The axillary nerve is uniquely vulnerable to the following destructive lesions: Stretching or tearing Axillary resulting from nerve Tearing resulting from  The POSTERIOR CORD…..has two terminal branches The AXILLARY nerve T. S O P Innervates ALL muscles of posterior arm and forearm and has an extensive cutaneous distribution to the posterior arm, forearm and most of the dorsum of the hand Leaving the axilla, the radial nerve Radial Nerve is vulnerable to compression against either of the following: Axillary Nerve 1- the tendon of insertion of latissimus dorsi 2- the proximal end of the humeral shaft Latissimus dorsi  BARSTOOL NEUROPATHY CRUTCH PALSY  Intrinsic (Scapulohumeral) Muscles Move the arm at the glenohumeral joint Deltoid Teres Major 4 “Rotator cuff” muscles – Supraspinatus – Infraspinatus – Teres Minor – Subscapularis  DELTOID ABDUCTION Three muscles participate in the formation of the POSTERIOR AXILLARY FOLD LATISSIMUS DORSI TERES MAJOR Muscles of similar name arising from the fossae of the body of the scapula contribute to formation of the “ROTATOR CUFF” SUBSCAPULARIS The muscles and tendons of the ROTATOR CUFF help to maintain the integrity of the GLENO-HUMERAL JOINT and…. stabilize the joint during contraction of powerful thoracoappendicular muscles inserting on the humerus like pec major and lat dorsi The TUBERCLES of the humerus feature clear facets for the insertion of the rotator cuff muscles  AVULSION FRACTURES of the GREATER TUBERCLE of the humerus occur commonly in elderly and middle-aged people following a fall on the point of the shoulder Stable fractures with no displacement are most common requiring minimal external fixation and exercise  SUPRASPINATUS DELTOID “Spurt” contraction Assumes initiates abduction responsibility of arm at gleno- for abduction humeral joint. beyond the first 20 degrees Isometric contraction of supraspinatus also resists the pull of gravity on the upper limb Supraspinatus and the bursae that protect it are vulnerable to inflammation and wear & tear  SUBACROMIAL BURSA SUBDELTOID BURSA SUBACROMIAL BURSITIS.. is the most commonly Injured part of the rotator cuff SUPRASPINATUS… NEURO- VASCULAR RELATIONS AT THE SHOULDER SUPRASCAPULAR NERVE and ARTERY innervates both supraspinatus and infraspinatus The nerve is vulnerable to entrapment as it courses through the scapular notch under the  QUADRANGULAR SPACE Teres minor Long Surgical head neck of triceps humerus Teres major The axillary nerve innervates both the AXILLARY NERVE and POSTERIOR HUMERAL CIRCUMFLEX ARTERY deltoid and teres minor muscles THE TRIANGULAR SPACE Transmits the circumflex scapular artery The vessel is a major participant in the complex arterial anastomosis around the shoulder  Lateral head of TRICEPS TERES MAJOR Long head of TRICEPS The TRIANGULAR INTERVAL transmits the radial nerve and deep brachial artery between axilla and posterior arm  where it is vulnerable to Upon exiting the axilla through the lesion with a midshaft triangular interval, the humeral fracture RADIAL NERVE Triangular interval courses along the RADIAL (SPIRAL) GROOVE…