Posterior Forearm and Hand Muscles PDF

Posterior Forearm Muscles - ALL innervated by the radial nerve = origin from C5, C6, C7, C8 and T1 roots (terminal branch of posterior cord) SUPERFICIAL LAYER Muscle Brachioradialis (BR) Origin + Insertion Origin - Proximal 2/3 of lateral supracondylar ridge of humerus Insertion - Lateral surface o...

Posterior Forearm Muscles - ALL innervated by the radial nerve = origin from C5, C6, C7, C8 and T1 roots (terminal branch of posterior cord) SUPERFICIAL LAYER Muscle Brachioradialis (BR) Origin + Insertion Origin - Proximal 2/3 of lateral supracondylar ridge of humerus Insertion - Lateral surface of distal end of radius proximal to styloid process Function Flexion of the forearm Innervation Radial Nerve - Origin from C5, C6, C6, C7, C8 and T1 roots - Terminal branch of posterior cord Origin - Distal 1/3 of lateral supracondylar ridge of humerus Insertion - Base of 2nd metacarpal bone - Extension of hand @ wrist - Radial deviation (abduction) of wrist - Flexion of elbow (weak) Radial Nerve - Origin from C5, C6, C6, C7, C8 and T1 roots - Terminal branch of posterior cord Extensor Carpi Radialis Brevis (ECRB) Origin - Lateral epicondyle of humerus (via common extensor tendon) Insertion - Base of 3rd metacarpal bone - Extension of hand @ wrist - Radial deviation (abduction) of wrist Radial Nerve - Origin from C5, C6, C6, C7, C8 and T1 roots - Terminal branch of posterior cord Extensor Digitorum (ED) Origin - Lateral epicondyle of humerus (via common extensor tendon) Insertion - Distal + middle phalanges of fingers #2-5 (via its dorsal digital expansion) - Extension of fingers 2-5 @ MCP, PIP and DIP joints - Extension of hand @ wrist - Extension of elbow (weak) Radial Nerve - Origin from C5, C6, C6, C7, C8 and T1 roots - Terminal branch of posterior cord *Does not cross wrist, only crosses elbow* *A boundary between posterior and anterior compartments* Flexor Carpi Radialis Longus (ECRL) *Longer of the 2 muscles in the pair and UNIQUE because it does not attach at the common extensor tendon* *Stays as a belly + separates into 4 pathways* *Allows extensor muscles to work all together + individually* Picture Extensor Digiti Minimi (EDM) Origin - Lateral epicondyle of humerus (via common extensor tendon) Insertion - Middle + distal phalanges of little finger (via its dorsal digital expansion) - Extension of finger 5 at MCP, PIP and DIP joints - Extension of hand @ wrist - Extension of elbow (weak) Radial Nerve - Origin from C5, C6, C6, C7, C8 and T1 roots - Terminal branch of posterior cord Extensor Carpi Ulnaris Origin - Lateral epicondyle of humerus (via common extensor tendon) - Posterior border of ulna Insertion - Base of 5th metacarpal bone - Extension of hand @ wrist - Ulnar deviation (adduction) of wrist - Extension of elbow (weak) Radial Nerve - Origin from C5, C6, C6, C7, C8 and T1 roots - Terminal branch of posterior cord Anconeus Origin - Extension of forearm @ elbow Radial Nerve - Lateral epicondyle of humerus - Origin from C5, C6, C6, C7, Insertion C8 and T1 roots - Olecranon process of ulna - Terminal branch of posterior - Proximal of posterior surface cord of ulna Dorsal Digital Expansion (Extensor Hood) - Extensor tendons flatten to form “dorsal digital expansions” or “extensor hoods” on the dorsal aspect of the digits o They are triangular tendinous aponeurosis that wrap around the MCP joints and extend along the proximal + middle phalanges across 2 interphalangeal joints to attach to the distal phalanx o Both interossei + lumbrical muscles attach to their sides o During flexion of the MCP joints by the lumbrical + interossei muscles, the proximal + distal interphalangeal joints are pulled by the extensor expansions into nearly complete extension (Ta-Ta position) o EXTENSOR EXPANSIONS ALLOWS THEM TO WORK TOGETHER + ALSO INDIVIDUALLY DEEP LAYER Supinator *PROSCUITTO AROUND A BREADSTICK** **From pronation à supination** Origin - Supination of forearm Radial Nerve - Supinator crest of ulna - Origin from C5, C6, C6, C7, (posterior ulna) C8 and T1 roots - Lateral epicondyle of humerus - Terminal branch of posterior Insertion cord - Proximal 1/3 of lateral surface of radius Has two heads and has a relationship with deep branch of radial nerve As supinator runs from lateral epicondyle to ulna, there will be a splite in the radial nerve and whenever a nerve runs beneath a muscle belly, there is irritation of the muscle = SUPINATORY SYNDROME Abductor Pollicis Longus (APL) Origin - Abduction of thumb @ CMJ Radial Nerve - Middle of posterior surface of - Extension of thumb @ CMJ - Origin from C5, C6, C6, C7, radius, ulna + interosseous - Radial deviation of hand @ C8 and T1 roots membrane wrist (weak) - Terminal branch of posterior Insertion cord - Base of 1st metacarpal Extensor Pollicis Brevis (EPB) **Posterior radius = brevis** Extensor Pollicis Longus (EPL) **Posterior ulna = longus** Extensor Indicis (EI) (indicis = ulna) Origin - Distal 1/3 of posterior surface of radius + interosseous membrane Insertion - Base of proximal phalanx of thumb Origin - Middle 1/3 of posterior surface of ulna + interosseous membrane Insertion - Base of distal phalanx of thumb Origin - Distal 1/3 of posterior surface of ulna + interosseous membrane Insertion - Dorsal digital expansion of 2nd finger - Extension of thumb @ CMJ = MCP joint - Extension of hand @ wrist - Radial deviation (abduction) of hand (weak) Radial Nerve - Origin from C5, C6, C6, C7, C8 and T1 roots - Terminal branch of posterior cord - Extension of thumb @ CMJ and MCP joint AND INTERPHALANGEAL JOINT - Extension of hand @ wrist - Radial deviation (abduction) of hand (weak) Radial Nerve - Origin from C5, C6, C6, C7, C8 and T1 roots - Terminal branch of posterior cord - Extension of hand @ wrist - Extension of digit 2 (index) @ MCP and interphalangeal joints (PROXIMAL + DISTAL) Anatomical Snuff Box - Tendons of APL + EPB bound the TRIANGULAR ANATOMICAL SNUFF BOX LATERALLY - Tendon of EPL bounds the TRIANGULAR ANATOMICAL SNUFF BOX MEDIALLY - Scaphoid + trapezium bones form the floor of the impression + can be palpated - Radial artery passes through the anatomical snuff box deep to the extensor tendons of the thumb - Fractured scaphoid = artery does not heal the bone if it is incomplete + bone begins to erode away Medial Epicondylitis (Golf Elbow) = FLEXION - Forceful + repeated bending of wrist + fingers cause tiny ruptures of common flexor tendon - In a swing: flexor muscles + tendons must tighten to hit the ball - Similar tasks that require repeated bending of wrist, gripping, grasping and turning the hand are common activities that cause medial epicondylitis - Small tears in the muscle begin to heal BUT when re-injured by continued use, become painful Lateral Epicondylitis (Tennis Elbow) - Common extensor tendon becomes painful and tender, due to overstrain, overuse or direct bang - Symptoms: tenderness + pain of outer part of lateral epicondyle Clinical Correlation: Radial Nerve Injury = DAMAGE TO POSTERIOR CORD OF BRACHIAL PLEXUS = RADIAL + AXILLARY NERVE - Muscles affected: o Deltoid, teres minor because innervated by axillary nerve o Distal triceps, anconeus, superficial + deep layers of forearm muscles = radial nerve - Movements affected: o Weakness in abduction (deltoid) + external rotation (teres minor) of shoulder o Loss of extension: elbow, wrist and fingers o Weakness in supination – biceps also supinates (musculocutaneous) thus not completely damaged - Sensory deficits: o Loss of sensation to lateral aspect of shoulder, posterior forearm and lateral 3.5 digits (dorsal surface) - Long-term deficits: o ‘Wrist drop’ deformity + deltoid atrophy (wrist drop from gravity) o Saturday night Palsy: falling into positions that cause radial nerve to be damaged The Hand - 3 parts: wrist (carpus), hand proper (metacarpus), fingers (digits) - Long axis of thumb (1st metacarpal bone) has 90° medial rotation to rest of fingers thus movements of thumb are ‘right angles’ to the movements of other fingers § § § § § Carpal Arch – directed anteriorly à changed to a tunnel à Carpal Tunnel via attachment of flexor retinaculum to the sides of it 9 tendons: 4 FDS, 4FDP, 1FPL 1 nerve: Median nerve Synovial sheath: hold synovial fluid (enlargement = presses structures = carpal tunnel syndrome) FLEXOR CARPI RADIALIS TENDON: does NOT pass through the tunnel, ONLY the flexor retinaculum Only deep + intrinsic muscles are a part of the carpal tunnel Intrinsic Muscles of The Hand (muscles that both originate + insert @ same region) 1. Thenar Muscles = median nerve a. Abductor pollicis brevis b. Flexor pollicis brevis c. Opponens pollicis 2. Hypothenar Muscles = ulnar nerve a. Abductor digiti minimi b. Flexor digiti minimi brevis manus c. Opponens digiti minimi 3. Central Muscles = ulnar nerve a. Lumbricals (4 muscles = both ulnar + median) b. Dorsal interosseous muscles (4) c. Palmar interosseous muscles (3) d. Adductor pollicis Palmar Aponeurosis – flat tendon; thickening of deep fascia of the palm Muscle Abductor Pollicis Brevis (APB) Origin + Insertion Origin - Flexor retinaculum - Tubercle of scaphoid - Tubercle of trapezium Insertion - Lateral side of base of proximal phalanx of thumb THENAR GROUP Function 1. Abduction of thumb Innervation Median Nerve (C8, T1) Picture Flexor Pollicis Brevis (FPB) Opponens Pollicis (OP) **Insertion of an opponens muscle is on the corresponding metacarpal bone; pollicis = 1st, minimi = 5th** Palmaris Brevis (PB) Abductor Digiti Minimi (ADM) Flexor Digiti Minimi Brevis Manus (FDMB) Opponens Digiti Minimi (ODM) Origin - Flexor retinaculum - Trapezium Insertion - Lateral side of base of proximal phalanx of thumb 1. Flexion of thumb Median Nerve (C8, T1) Origin - Flexor retinaculum - Trapezium Insertion - 1st Metacarpal 1. Opposition of thumb Median Nerve (C8, T1) HYPOTHENAR GROUP = ALL INNERVATED BY ULNAR NERVE Origin **No bony attachment** Ulnar Nerve (C8, T1) - Palmar aponeurosis 1. Wrinkles the skin (to improve Insertion grip) - Skin of medial side of hand Origin - Pisiform Insertion - Medial side of proximal phalanx of little finger 1. Abduction of little finger Ulnar Nerve (C8, T1) Origin - Flexor retinaculum - Hook of hamate Insertion - Medial side of base of proximal phalanx of 5th finger 1. Flexion of little finger Ulnar Nerve (C8, T1) Origin - Flexor retinaculum - Hook of hamate Insertion - 5th metacarpal bone 1. Opposition of little finger Ulnar Nerve (C8, T1) CENTRAL GROUP OF INTRINSIC HAND MUSCLES Adductor Pollicis (AP) **Most of the bulk of 1st web is made by it, thus ulnar nerve damage = WEB ATROPHY** Lumbrical Muscles (4 small and similar muscles) Dorsal Interosseous Muscles Origin Oblique head: - Base of 2nd + 3rd metacarpal bones - Capitate Transverse Head: - Anterior surface of 3rd metacarpal bone Insertion - Medial side of base of proximal phalanx of thumb (tendon of muscle contains a sesamoid bone) Origin - Tendon of Flexor Digitorum Profundus (FDP) of each finger (4) Insertion: dorsal digital expansion of 4 medial fingers Lumbrical 1: into dorsal digital expansion of index finger (finger 2) Lumbrical 2: into dorsal digital expansion of middle finger (finger 3) Lumbrical 3: into dorsal digital expansion of ring finger (finger 4) Lumbrical 4: into dorsal digital expansion of little finger (finger 5) Origin - Adjacent sides of metacarpals Insertion: base of proximal phalanges + dorsal digital expansion of fingers (2, 3, 4) Dorsal interosseous 1: to lateral side of index finger Dorsal interosseous 2: to lateral side of middle finger 1. Adduction of thumb Ulnar Nerve (C8, T1) TATA MOVEMENT: flexion @ MCP, extension @ IP (DIP+PIP), THUS: 1. Flexion of fingers 2-5 @ MCP 2. Extension of fingers 2-5 @ PIP + DIP Median: 1+2 = fingers 2+3 Ulnar: 3+4 = fingers 4+5 TATA MOVEMENT: flexion @ MCP, extension @ IP (DIP+PIP), THUS: 1. Flexion of fingers 2-5 @ MCP 2. Extension of fingers 2-5 @ PIP + DIP AND 3. Abduction of fingers ‘DAB’ Ulnar Nerve (C8, T1) Palmar Interosseous Muscles Dorsal interosseous 3: to medial side of middle finger Dorsal interosseous 4: to medial side of ring finger Origin - Anterior side of metacarpals 2, 4, 5 Palmar interosseous 1: metacarpal 2 Palmar interosseous 2: metacarpal 4 Palmar interosseous 3: metacarpal 5 Insertion: base of proximal phalanges + dorsal digital expansion of fingers (2, 4, 5) Palmar interosseous 1: to index finger (finger 2) Palmar interosseous 2: to ring finger (finger 4) Palmar interosseous 3: to little finger (finger 5) TATA MOVEMENT: flexion @ MCP, extension @ IP (DIP+PIP), THUS: 1. Flexion of fingers 2-5 @ MCP 2. Extension of fingers 2-5 @ PIP + DIP AND 3. Adduction of fingers ‘PAD’ Ulnar Nerve (C8, T1)