Radial Nerve Anatomy (PDF)

Lec.12 ‫ أشرف الصمدي‬.‫د‬ Radial n.: Origin: (Largest branch of brachial plexus) It arises from posterior cord of brachial plexus in axilla (C5,6,7,8,T1). ‫ينشأ‬...

Lec.12 ‫ أشرف الصمدي‬.‫د‬ Radial n.: Origin: (Largest branch of brachial plexus) It arises from posterior cord of brachial plexus in axilla (C5,6,7,8,T1). ‫ينشأ‬ End: It ends in front of lateral epicondyle of humerus by dividing into deep & superficial. Llterminal branches. ‫افرع نهائية‬ Course & relation: ‫مهم جدا‬ ‫املرور خالل‬ ‫مترافق مع‬ It enters the spiral groove on back of humerus by passing through lower triangular space accompanied by profunda brachii a., reaching lateral side of arm. It pierces lateral intermuscular septum to enter anterior compartment of arm (accompanied by ‫الن هي تكون مترفقة‬ anterior descending branch of profunda a.). It lies between brachioradialis ‫أمام‬ & extensor ‫مع‬ carpi radialis longus (laterally) & brachialis (medially). In front of lateral epicondyle, descending‫ال‬ it ends by giving the deep branch and continues as superficial terminal branch. branch of ‫ الي‬profunda ‫راح يكون امام‬ lateral ‫ال‬ epicodyle Branches of radial n.: In axilla: (2 muscular & 1 cutaneous) 1. Muscular: to long & medial heads of triceps. 2. Cutaneous: posterior cutaneous n. of arm. In spiral groove (arm): (3 muscular & 2 cutaneous) 1. Muscular: to lateral & medial heads of triceps & anconeus. 2. Cutaneous: lower lateral cutaneous n. of arm & posterior cutaneous n. of forearm. On lateral side of arm: (3 muscular & 1 articular) 1. Muscular: to brachialis (lateral part), brachioradialis & extensor carpi radialis longus. 2. Articular: to elbow joint.  Terminal branches: 1. Superficial radial branch (cutaneous): ‫تزود‬ ‫ظهر‬ It supplies skin of lateral two-thirds of dorsum of hand & dorsum of proximal ‫ السالميات القريبة‬phalanges of lateral three & half fingers. It descends along lateral side of forearm lateral to radial a. (middle third of forearm) under cover of brachioradialis over ‫تلتف‬ muscles attached to radius. About 5 cm above the wrist it winds round lateral side of radius to reach back of hand. It ends by dividing into 5 dorsal digital branches over anatomical snuffbox. anterior‫يعني راح تتحول من ال‬ posteriot ‫الى ال‬ 2. Deep branch (posterior interosseous n.): ‫تخترق‬ It descends under brachioradialis, pierces supinator, winds around neck of radius to back of forearm passing between superficial & deep layers of muscles. It is accompanied by posterior interosseous a. to dorsum of the hand. It gives: (1) muscular branches: to muscles of posterior compartment except anconeus, (2) articular branches: to wrist & carpal joints. Applied anatomy: Injury of radial n. in spiral groove: ‫شلل‬ It causes wrist drop & finger drop which is caused by paralysis of muscles of back of forearm (triceps not completely paralyzed). There will be loss of sensation along all cutaneous branches of radial n. except posterior cutaneous n. of arm (which is given in axilla). ‫يعني باخملتصر االفرع الي ينطيها‬ Injury to superficial branch: There will be loss of sensation on lateral two-thirds of dorsum of hand & dorsum of proximal phalanges of lateral three & half fingers. Injury to deep branch: ‫التدوير‬ It causes wrist drop & finger drop. There will be loss of supination of extended elbow (due to paralyzed supinator) as supination of flexed elbow is done by biceps brachii. Carrying angle: ‫تختفي‬ It is the angle between long axis of arm & forearm (extended & supinated). It is about 170º in male & 167º in female (opens laterally). It disappears when the elbow is flexed. It is caused by projection of medial half of trochlea more than its lateral half. ‫اسقاط‬  (MUSCLES OF FOREARM) Anterior compartment: Superficial group: (1) Pronator teres. (2) Flexor carpi radialis. (3) Flexor carpi ulnaris. (4) Palmaris longus. Intermediate group: (5) Flexor digitorum superficialis. Deep group: (6) Flexor digitorum profundus. (7) Flexor pollicis longus. (8) Pronator quadratus. Lateral compartment: (1) Brachioradialis. (2) Extensor carpi radialis longus. Posterior compartment: Transverse: (1) Anconeus. (2) Supinator. Longitudinal: (3) Extensor carpi ulnaris. (4) Extensor carpi radialis brevis. To digits: (5) Extensor digitorum. (6) Extensor digiti minimi. (7) Extensor indicis. To thumb: (8) Extensor pollicis longus. (9) Extensor pollicis brevis. (10) Abductor pollicis longus. (ARTERIES OF FOREARM & HAND) Radial a.: Beginning: ‫عنق‬ It is the smaller terminal branch of brachial a. It begins at level of neck of radius (in cubital fossa). End: ‫يستمر‬ It continues as deep palmar arch at the level of proximal end of fully extended thumb (at base of 5th metacarpal bone). Branches: In forearm: 1. Radial recurrent a. 2. Muscular branches. 3. Palmar (anterior) carpal a.: joins palmar carpal branch of ulnar a. to form the palmar carpal arch. 4. Superficial palmar branch: joins ulnar a. to complete the superficial palmar arch. In dorsum of hand: 1. Dorsal (posterior) carpal a.: joins dorsal (posterior) branch of ulnar a. to form the dorsal carpal arch which gives: (a) dorsal digital a.: for medial side of little finger. (b) second, third & fourth metacarpal arteries: that divide into two branches to supply adjacent sides of 2nd, 3rd, 4th & 5th fingers. 2. First dorsal metacarpal a.: divides into two branches, supply adjacent sides of the 1st & 2nd fingers. 3. Dorsal digital a.: supply the lateral side of thumb. In palm of hand: 1. Princeps pollicis a.: divide into 2 digital branches. 2. Radialis indicis a.: along lateral side of index. 3. Deep palmar arch: continuation of radial a., giving: (a) three palmar metacarpal arteries. (b) three perforating arteries: perforate dorsal interossei muscles to join 3 dorsal metacarpal arteries. (c) recurrent branch: ascend to join the anterior carpal arch. Course & relation of radial a.: ‫تنزل‬ ‫اجلزء اجلانبي‬ Radial a. starts at neck of radius, descends in the forearm at lateral side (accompanied by 2 venae comitantes).  ‫يعني الي فوق الشريان‬ Anterior (superficial) relation: Upper two-thirds of forearm: covered only by brachioradialis. Lower third: is subcutaneous, and pulsation can be felt. ‫الي جوا الشريان‬ ‫حتت اجللد‬ ‫النبض‬ Posterior (deep) relation: (1) Tendon of biceps brachii. (2) Supinator. (3) Pronator teres. (4) Flexor digitorum superficialis (radial head). (5) Flexor pollicis longus. (6) Pronator quadratus. (7) Radius (lower end). Lateral relation: Radial n. & brachioradialis. Medial relation: Pronator teres & flexor carpi radialis. Note: (To swim properly, flex forearm & pronate radius). Note: Radial a. winds posteriorly (at distal end of radius) to reach anatomical snuffbox (passing deep to abductor pollicis longus & extensor pollicis brevis). It leaves the snuffbox deep to extensor pollicis longus reaching the first interosseous space. It enters the palm of the hand between 2 heads of the 1st dorsal interosseous & 2 heads of adductor pollicis and continues as deep palmar arch.  Applied anatomy of radial a.: The radial pulse is the most commonly used one for feeling & counting the arterial ‫نبض‬ pulsation. Pulsation is felt against distal end of radius close to lateral side of flexor carpi radialis tendon. ‫مقابل النهاية البعيدة‬ Surface anatomy: 1. Ulnar a.: by drawing 3 points: Point at midway between 2 epicondyles of humerus. Point at junction of upper third & lower two-thirds of forearm at medial side. Point just lateral to pisiform. ‫البعيدة‬ 2. Superficial palmar arch: at distal border of fully extended thumb. ‫القريبة‬ 3. Deep palmar arch: at proximal border of extended thumb. Written by : Mohammed Wael