BMS100_Shoulder Girdle, Rotator Cuff and Brachial Plexus.docx

BMS100 – MSK6 SHOULDER GIRDLE AND JOINT, BRACHIAL PLEXUS AND ROTATOR CUFF BRACHIAL PLEXUS Brachial plexus: major nerve network supplying the upper limb formed by the union of anterior rami of C5-T1; begins in neck and extends inferior-laterally into the axilla Arterial supply of upper limb – subc...

BMS100 – MSK6 SHOULDER GIRDLE AND JOINT, BRACHIAL PLEXUS AND ROTATOR CUFF BRACHIAL PLEXUS Brachial plexus: major nerve network supplying the upper limb formed by the union of anterior rami of C5-T1; begins in neck and extends inferior-laterally into the axilla Arterial supply of upper limb – subclavian artery axillary artery Peripheral nerves of brachial plexus are divided into supraclavicular and infraclavicular parts Supraclavicular part – 4 branches Dorsal scapular nerve (from C5 root) Long thoracic nerve (from C5, 6, 7) Nerve to subclavius (from superior trunk) Suprascapular nerve (from superior trunk) Infraclavicular part Branches of lateral cord: Lateral pectoral nerve Musculocutaneous nerve Branches of the medial cord: Medial pectoral nerve Medial cutaneous nerve of arm Medial cutaneous nerve of forearm Ulnar nerve Branches of the posterior cord: Upper subscapular nerve Thoracodorsal nerve Lower subscapular nerve Axillary nerve Radial nerve Pneumonic Formation of plexus in inferior lateral direction – 5-3-6-3-5 5 roots 3 trunks 6 divisions 3 cords 5 terminal branches (peripheral nerve) Arrangement of terminal branches – MARMU Musculocutaneous Axillary Radial Median Ulnar ROOTS: anterior branches of fully formed spinal nerves that have exited the intervertebral foramen and head laterally/inferiorly away from the midline Roots pass through the gap between anterior and middle scalene muscles – lateral to cervical spine 5 roots – C5, C6, C7, C8, T1 TRUNKS: roots pass through scalene muscles on lateral aspect of neck to form three trunks Superior trunk – union of C5 and C5 roots Middle trunk – continuation of C7 root Inferior trunk – union of C8 and T1 roots DIVISIONS: each trunk gives off two branches; splitting into anterior (flexor) and posterior (extensor) divisions as plexus passes posterior to the clavicle Superior trunk – anterior and posterior divisions Middle trunk - anterior and posterior divisions Inferior trunk - anterior and posterior divisions CORDS: once anterior and posterior divisions have entered axilla, they combine to form three cords, named by their position relative to the axillary artery Lateral cord – anterior divisions of the superior and middle trunks (lateral to artery) Medial cord – anterior division of inferior trunk (medial to artery) Posterior cord – posterior division of all three trunks (posterior to artery) TERMINAL BRANCHES: once in axilla and proximal aspect of upper limb; three cords give rise to 5 major branches which continue into upper limb (MARMU) Musculocutaneous nerve lateral cord Axillary nerve posterior cord Radial nerve posterior cord Median nerve lateral and medial cord Ulnar nerve medial cord SHOULDER GIRDLE MUSCLES MUSCLE ATTACHEMENT/LOCATION INNERVATION MAIN ACTION/ROLE Trapezius Flat, triangular muscle covering the upper and back part of the neck and shoulders Origin: Upper trapezius – external occipital protuberance, medial superior nuchal line of the occipital bone, ligamentum nuchae, SP of C7 Middle trapezius – SP of T1 to T5 Lower Trapezius – SP of T6 to T12 Insertion (all): lateral 1/3 of clavicle, acromion, spine of scapula Spinal accessory nerve (CN XI) Primarily moves at insertion point (scapula) Upper fibers Elevation of scapula Upward rotation of scapula External and lateral flexion of head (bilateral contraction mostly) and neck Contralateral rotation of head and neck Middle fibers Retraction (abduction of scapula) Lower fibers Depression of scapula Upward rotation of scapula Rhomboid minor Origin: SPs of C7 and T1 Insertion: medial (vertebral) border of scapula at root of the spine Dorsal scapular nerve Retraction (adduction) of scapula Elevation of scapula Downward rotation of scapula Rhomboid major Origin: SPs of T2 to T5 Insertion: medial (vertebral) border of scapula inferior to spine Levator scapulae Origin: TPs of C1 to C4 Insertion: medial border of scapulae (above spine of scapula Dorsal scapular nerve Extension of neck at spinal joints Lateral flexion of neck at spinal joints Ipsilateral rotation of neck at spinal joints Elevation of scapula at the scapulocostal joint Downward rotation of scapula at the scapulocostal joint Pectoralis minor Origin: 3rd to 5th ribs Insertion: coracoid process Medial pectoral nerve Protraction (ABD) of scapula Downward rotation of scapula Depression of scapula Elevation of ribs 3-5 at sternocostal and costospinal joints (during forced inhalation when scapula is fixed) Pectoralis major Origin: Clavicular head – medial half of clavicle Sternocostal head – sternum and costal cartilages of 1st to 7th ribs Insertion: lateral lip of tubercular (bicipital) groove of humerus Medial and lateral pectoral Flexion of arm (clavicular head) Adduction of arm Medial rotation of arm Horizontal adduction of the arm Subclavius Origin: 1st rib Insertion: subclavian groove of the clavicle Nerve to subclavius Depression of clavicle at the sternoclavicular and acromioclavicular joints (keeps down) Serratus anterior Origin: upper 9 ribs Insertion: anterior surface of medial (vertebral) border of scapula Long thoracic nerve (C5-C7) Protraction (ABD) of scapula – away from spine Upward rotation of scapula Latissimus dorsi Origin: SP of T7 to L5 Crests of ilium and sacrum Lowest four ribs (via thoracolumbar fascia) Thoracodorsal Extension of arm Adduction of arm Medial rotation of arm Anterior tilt of pelvis (slight) *downward rotation of scapula by three muscles that attach to medial border of scapula – rhomboid major/minor and levator scapulae **upward rotation of scapula by muscle that attaches on lateral surface of scapula – trapezius Winged scapula Injury of the long thoracic nerve produces a paralysis (weakness) of the serratus anterior muscle as the muscle undergoes atrophy and can no longer function properly Inferior angle of the medial border of the scapula is excessively prominent – no longer held onto rib cage (abnormal protrusion) Can no longer raise arm above head or perform pushing action – serratus anterior unable to rotate the glenoid cavity superiorly to allow complete abduction of the arm MUSCLES OF THE ROTATOR CUFF AND SHOULDER JOINT Rotator cuff muscles = includes 4 muscles: Supraspinatus Infraspinatus Teres minor Subscapularis Main role strengthen the shoulder joint capsule all around except inferiorly Muscles of the shoulder joint have same function as muscles of the rotator cuff – redundancy in movements Explains why dislocations of the humerus occur most commonly in a downward direction MUSCLES OF THE ROTATOR CUFF AND SHOULDER JOINT MUSCLE ATTACHMENT/LOCATION INNERVATION MAIN ACTION/ROLE Deltoid Origin: Lateral clavicle (anterior fibres) Acromion (lateral fibres) Spine of scapula (posterior fibres) Insertion: deltoid tuberosity of humerus Axillary nerve Flexion of shoulder joint (anterior fibres) Extension of shoulder joint (posterior fibres) Medial rotation (anterior fibres) Lateral rotation (posterior fibres) Abduction of shoulder joint (entire muscle Subscapularis Origin: subscapular fossa Insertion: lesser tubercle of humerus Upper and lower subscapularis nerves Medial rotation of shoulder joint Supraspinatus Origin: supraspinous fossa Insertion: greater tubercle of humerus Suprascapular nerve Abduction of the shoulder joint Infraspinatus Origin: infraspinous fossa Insertion: greater tubercle of humerus Suprascapular nerve Lateral rotation of shoulder joint Horizontal abduction of shoulder joint Teres minor Origin: superior lateral border of scapula Insertion: greater tubercle of humerus Axillary nerve Lateral rotation of shoulder joint Teres major Origin: inferior lateral border of scapula Insertion: medial lip of intertubercular (bicipital) sulcus (groove) of humerus Upper and lower subscapular nerves Extension of shoulder joint Adduction of shoulder joint Medial rotation of shoulder joint Axillary spaces Triangular space: Circumflex scapular artery Quadrangular space: Axillary nerve Posterior humeral circumflex artery Triangular interval space: Radial nerve Profunda brachii artery