Bms Anatomy Lecture 8 Posterior Forearm Muscles Fall 2023 PDF

BMS Anatomy Lecture 8 Posterior Forearm Muscles (In-Person Class) Presented By: Dr. K. Lumsden; [email protected] (Toronto Campus) Dr. M. Doroudi; [email protected] Boucher Campus) Moore's Clinically Oriented Anatomy, by Arthur F. Dalley II PhD FAAA (Author), Anne M. R. Agur BSc (OT) MSc PhD FAAA (A...

BMS Anatomy Lecture 8 Posterior Forearm Muscles (In-Person Class) Presented By: Dr. K. Lumsden; [email protected] (Toronto Campus) Dr. M. Doroudi; [email protected] Boucher Campus) Moore's Clinically Oriented Anatomy, by Arthur F. Dalley II PhD FAAA (Author), Anne M. R. Agur BSc (OT) MSc PhD FAAA (Author), 9th ed. Upper Limb Chapter; Pages: 207 – 211, 220 – 222 POSTERIOR COMPARTMENT of Forearm: Remember! all posterior forearm compartment muscles are innervated by Muscles of the Posterior forearm: radial N. SUPERFICIAL LAYER: DEEP LAYER: PRIMARY ACTIONS: Supination of forearm If the muscle crosses the wrist = EXTENSION of wrist If the muscle crosses the digits = EXTENSION of digits ❖ Remember! all posterior forearm compartment muscles are innervated by radial N. Brachioradialis (BR); Ori: Proximal 2/3 of lateral supracondylar ridge of humerus Ins: Lateral surface of distal end of radius proximal to styloid process Fun: 3 N: Muscles and Nerves of the Upper Limb Muscles that perform Elbow Flexion: Flexion with Supination = Biceps = Musculocutaneous nerve Flexion with pronation = Brachialis = Musculocutaneous nerve Flexion in mid-pronation = Brachioradialis = Radial nerve ❖ Extensor Carpi Radialis Longus (ECRL) Ori: Distal 1/3 of lateral supracondylar ridge of humerus Ins: Base of 2nd metacarpal bone Fun: N: 5 ❖Extensor Carpi Radialis Brevis (ECRB) Ori: Lateral epicondyle of humerus (via common extensor tendon) Ins: Base of 3rd metacarpal bone Fun: N: 6 Mobile Wad of Three: BR,ECRL, ECRB ❖ Extensor Digitorum (ED) Ori: Lateral epicondyle of humerus (via common extensor tendon) Ins: Distal and middle phalanges of fingers #2 – 5 (via its dorsal digital expansion) Fun: N: 8 ❖ Extensor digiti minimi (Edm) Ori: Lateral epicondyle of humerus (via common extensor tendon) Ins: Middle and distal phalanges of little finger (via its dorsal digital expansion) Fun: N: 9 Dorsal Digital Expansion (Extensor Hood) ❑ The extensor tendons flatten to form “dorsal digital expansions” or “extensor hoods” on the dorsal aspect of the digits. These are triangular tendinous aponeurosis that wrap around the metacarpophalangeal joints and extend along the proximal and middle phalanges across two interphalangeal joints to attach to the distal phalanx. Interossei and lumbrical muscles attach to their sides. During flexion of the metacarpophalangeal joints by the lumbrical and interossei muscles, the proximal and distal interphalangeal joints are pulled by the extensor expansions into nearly complete extension (Ta-Ta Position). 10 Dorsal Digital Expansions (Extensor Hoods) ❖ Extensor Carpi Ulnaris (ECU) Ori: - Lateral epicondyle of humerus (via common extensor tendon) - Posterior border of ulna Ins: Base of 5th metacarpal bone. Fun: N: 12 ❖ Anconeus Ori: Lateral epicondyle of humerus Ins: - Olecranon process of ulna - Proximal of posterior surface of ulna Fun: N: 13 ❖ Supinator Ori: 1. Supinator crest of ulna 2.Lateral epicondyle of humerus Ins: Proximal 1/3 of lateral surface of radius Fun: N: 14 Supinator M. Notes Two heads, relationship with deep branch of radial N. Deep branch of radial nerve within heads of supinator 15 ❖ Abductor Pollicis Longus (APL) Ori: The middle of posterior surface of radius, ulna, and interosseous membrane Ins: Base of the 1st metacarpal Fun: N: 16 ❖ Extensor Pollicis Brevis (EPB) Ori: Distal 1/3 of posterior surface of radius and interosseous membrane Ins: Base of proximal phalanx of thumb Fun: N: 17 ❖ Extensor Pollicis Longus (EPL) Ori: Middle 1/3 of posterior surface of ulna and interosseous membrane Ins: Base of distal phalanx of thumb Fun: N: 18 ❖ Extensor Indicis (EI) Ori: Distal 1/3 of posterior surface of ulna and interosseous membrane Ins: Dorsal digital expansion of the 2 nd finger Fun: N: 19 Anatomical Snuff Box  The tendons of the abductor pollicis longus (APL) and extensor pollicis brevis (EPB) bound the triangular anatomical snuff box laterally, and the tendon of the extensor pollicis longus (EPL) bounds it medially.  The “snuff box” is visible as a hollow on the posterolateral aspect of the wrist when the thumb is extended fully. This draws the APL, EPB, and EPL tendons up and produces a concavity between them.  The scaphoid and trapezium bones form the floor of the impression and can be palpated. The radial artery passes through the anatomical snuff box deep to the extensor tendons of the thumb. 20 Forearm Flexor and Extensor muscles clinical anatomy Medial Epicondylitis (Golf Elbow) Forceful and repeated bending of the wrist and fingers cause tiny ruptures of common flexor tendon. Golfing is only one of the causes of the pain at this bone. In the golf swing, the flexor muscles and tendons must tighten to hit the ball. Similar tasks that require repeated bending of the 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. Symptoms include tenderness and pain at the medial epicondyle, made worse by flexing the wrist. Forearm Flexor and Extensor muscles clinical anatomy Lateral Epicondylitis (Tennis Elbow) Tennis Elbow or Lateral Epicondylitis is a condition when the common extensor tendon becomes painful and tender, usually as a result of a specific strain, overuse, or a direct bang. Sometimes no specific cause is found. Symptoms include tenderness and pain of the outer part of the lateral epicondyle. CLINICAL CORRELATION: Radial Nerve Injury = Damage to the posterior cord of the brachial plexus What terminal branches would be affected? What muscle(s) would be affected? Deltoid, Teres Minor Distal Triceps, Anconeus, superficial and deep layers of forearm muscles Confirmed by testing strength of muscles and comparing bilaterally What movements would be affected? Weakness in abduction and external rotation of shoulder Loss of extension: elbow, wrist and fingers Weakness in supination What sensory deficits might be present? Loss of sensation to lateral aspect of shoulder, posterior forearm and lateral 3.5 digits (dorsal surface) What long term deficits might occur? “Wrist Drop” deformity and Deltoid atrophy