Elbow-Forearm PDF

Bones of the forearm: Ulna: medial and longer stabilizing bone of the forearm. It does not participate in the wrist joint. ○ Oleacron: projects proximally from its posterior aspect (forms the point of the elbow) serves as a short lever for extension of the elbow...

Bones of the forearm: Ulna: medial and longer stabilizing bone of the forearm. It does not participate in the wrist joint. ○ Oleacron: projects proximally from its posterior aspect (forms the point of the elbow) serves as a short lever for extension of the elbow ○ Coronoid process: extends with the oleacron and projects anteriorly. ○ Trochlear notch: formed by the oleacron and the Coronoid process. This articulation allows for mostly extension and flexion, but a little abduction and adduction occur during supination and pronation. ○ Tuberosity of ulna: inferior to the Coronoid process, serves as an attachment to the brachialis muscle. ○ Radial notch: lateral to the Coronoid process, is a smooth rounded concavity, receives the broad periphery of the head of the radius. ○ Supinator crest: proeminent ridge inferior to the radial notch. ○ Supinator fossa: concavity between the Supinator crest and the Coronoid process. ○ Shaft: thick and cylindrical proximally, becomes thinner the more distal you look. ○ Head: abrupt enlargement on the distal end of the ulna. Disc like shape. ○ Styloid process:part of the head of the ulna. Radius: ○ Head: discoid structure articulating with the Capitulum. Also articulates with the radial notch of the ulna. It is covered by articular cartilage. ○ Neck: constriction distal to the head. ○ Radial tuberosity: splits the head and neck (proximal part) from the shaft (distal part). It is an oval shaped elevation. ○ Ulnar notch: concavity on the medial aspect of the radius’ most distal part. It accommodates the head of the ulna. ○ Styloid process: the ulnar notch becomes more and more ridge like and terminates distally into the Styloid process. ○ Dorsal tubercule: posterior projection, lies between shallow grooves for the passage of forearm muscles. ○ Interosseous border: part of the radius and or ulna that allows for attachment of the Interosseous membrane. ○ Interosseous membrane: fibers run obliquely, allow for radial impact force to be transferred to the ulna and then to the humerus. Joints of the forearm: Elbow joint: ○ Type: hinge type synovial joint ○ Two articulations: the elbow joint is formed by 2 articulations of 2 different bones with the humerus: Humeroulnar: articulation between the Trochlear notch of the ulna and Trochlea of the humerus. Humeroradial: articulation between the Capitulum of the humerus and the head of the radius. ○ Capsule: surrounds the joint. Attaches to the humerus at the lateral and medium ends of the Capitulum and the Trochlea. ○ Ligaments:  Radial collateral (LCL): lateral fan like ligament. Attaches proximally at the lateral epicondyle of the humerus and distally at the anular ligament of the radius. Annular: encircles radial head and holds it in the radial notch of the ulna. (This forms the radio-ulnar joint and allow for pronation and supination of the forearm). Ulnar collateral (MCL): medial triangular ligament. Its proximal attachment is the medial epicondyle of the humerus to the oleacron and Coronoid process of the ulna. Made up of three bands: anterior (cordlike, strongest), posterior (fanlike, weakest), oblique (slender, deepens the socket of the Trochlea of the humerus). ○ Movements: flexion/extension ○ Blood supply: anastomosis around the elbow joint ○ Nerve supply: musculocutaneous, radial, median and ulnar nerves. ○ Bursae: Intratendinous Oleacron bursa: sometimes present in the tendon of the triceps brachii. Subtendinous Oleacron bursa: located between the oleacron and triceps tendon, just proximal to its attachment to the oleacron. Subcutaneous Oleacron bursa: located in the subcutaneous connective tissue over the oleacron. Bicipitoradial bursa: separated the biceps tendon from the radial tuberosity,also reduces friction. Proximal radioulnar joint: ○ Type: pivot type synovial ○ Capsule: continuous with the elbow joint capsule. ○ Ligaments: Anular:encircles radial head and holds it in the radial notch of the ulna. ○ Movements: pronation/supination. Occurs through rotation of the head of the radius. ○ Blood supply: supplied by the peri-articular arterial anastomosis of the elbow joint. ○ Nerve supply: musculocutaneous and radial for supination and median for pronation. Carrying angle: named after how the forearm angles away from the body when something is carried. It is about 10-15° in men vs greater than 15° in women. Allows for the arms to clear the larger female pelvis when walking. Carrying angle doesn’t exist in pronated arm. Cubital fossa: Location: ○ Superior boundary: imaginary line connecting lateral and medial epicondyles. ○ Medial boundary: mass of flexor muscles attached to the medial epicondyle of the humerus, more specific the pronator teres. ○ Lateral boundary:mass of extensor muscles of the forearm, attaching to the lateral epicondyle and supra epicondylar ridge. More specific, the brachioradialis. ○ Floor boundary: brachialis and Supinator muscles of arm and forearm.  ○ Roof of the cubital fossa: brachial and antebrachial deep fascia as well as well as bicipetal aponeurosis, subcutaneous tissue and skin. Contents: ○ Brachial artery’s end ○ Beginning of ulnar artery ○ Beginning of radial artery ○ Veins that accompany the arteries ○ Biceps brachii tendon ○ Median nerve ○ Radial nerve Boundaries: Cubital tunnel: Boundaries: ○ Floor: MCL& Elbow joint capsule (cubital tunnel retinaculum). ○ Roof: ligament between medial condyle & Oleacron. ○ Anterior wall: medial epicondyle of humerus. ○ Lateral wall: Oleacron process ○ Posterior wall: Triceps (medial head) Contents: ○ Ulnar nerve ○ Fat Arm compartments: Anterior (flexors): supplied by the musculocutaneous muscle. Anterior portion of the arm. ○ Biceps ○ Brachialis ○ Coracobrachialis Posterior (extensors): supplied by the radial nerve, posterior portion of the arm. ○ Triceps Muscles of the arm: Biceps brachii: ○ Proximal attachment: short head: tip of Coracoid process of scapula. Long head: supraglenoid Tubercule of scapula. ○ Distal attachment: tuberosity of radius and fascia of forearm via bicipital aponeurosis. ○ Innervation: Musculocutaneous (C5,C6, and C7) ○ Muscle action: supinates forearm, flexes forearm when supinated. Short head resists dislocation of the shoulder. Coracobrachialis: ○ Proximal attachment: tip of the Coracoid process of the scapula. ○ Distal attachment: middle third of medial surface of the humerus. ○ Innervation: musculocutaneous (C5,C6 and C7) ○ Muscle action: helps flex and adduct the arm; resists dislocation of the shoulder. Brachialis: ○ Proximal attachment: distal half of anterior surface of humerus. ○ Distal attachment: Coronoid process and tuberosity of the ulna.  ○ Innervation: musculocutaneous nerve (C5, C6 and C7) and Radial nerve (C5, C7) ○ Muscle action: flexes forearm in all positions. Triceps brachii: ○ Proximal attachment: long head: Infraglenoid tubercule of scapula. Lateral head: posterior surface of humerus, superior to radial groove. Medial head: posterior surface of humerus, inferior to radial groove. ○ Distal attachment: proximal end of oleacranon of ulna and fascia of forearm. ○ Innervation: radial nerve (C6, C7 and C8) ○ Muscle action: chief extensor of forearm; long head resists dislocation of the humerus: especially important during adduction Anconeous: ○ Proximal attachment:lateral epicondyle of the humerus. ○ Distal attachment: lateral surface of Oleacron and superior part of posterior surface of the ulna. ○ Innervation: radial nerve (C7, C8, T1) ○ Muscle action: assists triceps in extending forearm; stabilizes elbow joint; may abduct ulna during pronation Forearm compartments: Anterior (flexor-pronator) separated from the extensors by the radius and ulna and Interosseous membrane at the bottom. ○ Superficial (first): pronator teres, flexor carpi radialis, palmaris longus, and flexor carpi ulnaris. ○ Intermediate (second): flexor digitorium superficialis ○ Deep (third): flexor digitorium profundus, flexor policies longus, pronator quadratus Posterior (extensor-Supinator) ○ Superficial (first) ○ Intermediate (second) ○ Deep (third) Muscles of anterior compartment of forearm: Superficial (first) layer: Pronator Teres: ○ Ulnar head: Proximal attachment: Coronoid process Distal attachment: middle of convexity of lateral surface of the radius Innervation: Median nerve C6,C7 Muscle action: pronates and flexes forearm at elbow. ○ Humeral head: Proximal attachment: medial epicondyle of humerus (common flexor origin) Distal attachment:middle of convexity of lateral surface of the radius Innervation:Median nerve C6,C7 Muscle action:pronates and flexes forearm at elbow. Flexor carpi radialis: ○ Proximal attachment:medial epicondyle of humerus (common flexor origin) ○ Distal attachment: base of second metacarpal ○ Innervation: Median nerve C6,C7  ○ Muscle action: flexes and abducts hand at wrist Palmaris longus: ○ Proximal attachment:medial epicondyle of humerus (common flexor origin) ○ Distal attachment: distal half of flexor retinaculum and apex of palmar aponeurosis. ○ Innervation: Median nerve C7,C8 ○ Muscle action: flexes hand (at wrist) and tenses palmar aponeurosis. Flexor Carpi Ulnaris: ○ Humeral head: Proximal attachment:medial epicondyle of humerus (common flexor origin) Distal attachment:Pisiform hook of hamate, 5th metacarpal Innervation:Ulnar nerve (C7, C8) Muscle action: flexes and adducts hand at wrist ○ Ulnar head: Proximal attachment: Oleacron and posterior border of ulna (via aponeurosis) Distal attachment:Pisiform hook of hamate, 5th metacarpal Innervation:Ulnar nerve (C7, C8) Muscle action:flexes and adducts hand at wrist Intermediate (second layer): Flexor digitorium superficialis: ○ Humerus-ulnar head: Proximal attachment: Medial epicondyle common flexor origin and Coronoid process) Distal attachment: shafts of middle phalanges of medial 4 digits. Innervation: median nerve (C7,C8, T1) Muscle action: flexes middle phalanges at proximal interphalangeal joints of middle four digits; acting more strongly, it also flexes proximal phalanges at metacarpophalangeal joints. ○ Radial head: Proximal attachment: superior half of anterior border. Distal attachment:shafts of middle phalanges of medial 4 digits. Innervation:median nerve (C7,C8, T1) Muscle action:flexes middle phalanges at proximal interphalangeal joints of middle four digits; acting more strongly, it also flexes proximal phalanges at metacarpophalangeal joints. Deep (third) layer: Flexor digitorium profundos: ○ Medial part: Proximal attachment:proximal ¾ of medial and anterior surfaces of ulna and interosseous membrane. Distal attachment: base of phalanges of 4th and 5th digits Innervation: Ulnar nerve (C8,T1) Muscle action: flexes distal phalanges 4 and 5 at distal interphalangeal joints. ○ Lateral part:  Proximal attachment:proximal ¾ of medial and anterior surfaces of ulna and interosseous membrane. Distal attachment: bases of distal phalanges of 2nd and 3rd digits Innervation: Anterior Interosseous nerve from median nerve (C8, T1) Muscle action: flexes distal phalanges 2 and 3 at distal interphalangeal joints. Flexor pollicis longus: ○ Proximal attachment: anterior surface of radius and adjacent Interosseous membrane. ○ Distal attachment: base of distal phalanx of thumb ○ Innervation:Anterior Interosseous nerve from median nerve (C8, T1) ○ Muscle action: flexes phalanges of 1st digit. Pronator quadratus: ○ Proximal attachment: distal quarter of anterior surface of ulna ○ Distal attachment: distal quarter of anterior surface of radius ○ Innervation:Anterior Interosseous nerve from median nerve (C8, T1) ○ Muscle action: pronates forearm, deep fibers bind radius and ulna together. Muscles of posterior compartment of forearm: Superficial layer: Brachioradialis: ○ Proximal attachment: proximal ⅔ of lateral of lateral Supra-epicondylar ridge of humerus ○ Distal attachment: lateral surface of distal end of radius proximal to Styloid process ○ Innervation: radial nerve (C5, C6, C7) ○ Muscle action: relatively weak flexion of the forearm; maximal when forearm is in mid pronated position. Extensor carpi radialis longus: ○ Proximal attachment: lateral Supra-epicondylar ridge of humerus ○ Distal attachment: dorsal aspect of base of 2nd metacarpal ○ Innervation: radial nerve (C6, C7) ○ Muscle action: extends and abducts hand at wrist joint. Active during first clenching. Extensor carpi radialis brevis: ○ Proximal attachment: Lateral epicondyle of humerus (common extensor origin) ○ Distal attachment: dorsal aspect of base of 3rd metacarpal ○ Innervation: deep branch of radial nerve (C7,C8) ○ Muscle action:extends and abducts hand at wrist joint. Extensor digitorum: ○ Proximal attachment:Lateral epicondyle of humerus (common extensor origin) ○ Distal attachment: extensor expansions of medial 4 digits ○ Innervation:deep branch of radial nerve (C7,C8) ○ Muscle action: extends medial 4 digits primarily at metacarpophalangeal joints, secondarily at the interphalangeal joints Extensor digiti minimi:  ○ Proximal attachment:Lateral epicondyle of humerus (common extensor origin) ○ Distal attachment: extensor expansion of 5th digit ○ Innervation:deep branch of radial nerve (C7,C8) ○ Muscle action: extends 5th digit primarily at metacarpophalangeal joint and secondarily at the interphalangeal joint. Extensor carpi ulnaris: ○ Proximal attachment:Lateral epicondyle of the humerus; posterior border of ulna via shared aponeurosis ○ Distal attachment: Dorsal aspect of base of 5th metacarpal ○ Innervation:deep branch of radial nerve (C7,C8) ○ Muscle action: extends and adducts hand at wrist joint (also active during clenching) Deep layer: Supinator: ○ Proximal attachment: Lateral epicondyle of humerus; radial collateral and anular ligaments; Supinator fossa; crest of ulna ○ Distal attachment: lateral posterior and anterior surfaces of proximal third to radius ○ Innervation: Deep branch of radial nerve (C7,C8) ○ Muscle action: supinates forearm; rotates radius to turn palm anteriorly or superiorly (if elbow is flexed) Extensor indicis: ○ Proximal attachment: posterior surface of distal third of ulna and Interosseous membrane ○ Distal attachment: extensor expansion of 2nd digit ○ Innervation: Posterior Interosseous nerve (C7, C8) continuation of deep branch of radial nerve ○ Muscle action: Extends 2nd digit (enabling its independent extension); helps extend hand at the wrist. Abductor pollicis longus: ○ Proximal attachment: posterior surface of proximal halves of ulna, radius and Interosseous membrane ○ Distal attachment: base of 1st metacarpal ○ Innervation:Posterior Interosseous nerve (C7, C8) continuation of deep branch of radial nerve ○ Muscle action:abducts thumb and extends it at carpometacarpal joint Extensor pollicis longus: ○ Proximal attachment: posterior surface of middle third of ulna and Interosseous membrane ○ Distal attachment: dorsal aspect of base of distal phalanx of thumb ○ Innervation:Posterior Interosseous nerve (C7, C8) continuation of deep branch of radial nerve ○ Muscle action: extends distal phalanx of thumb at interphalangeal joint; extends metacarpophalangeal and carpometacarpal joint. Extensor pollicis brevis: ○ Proximal attachment: posterior surface of distal third of radius and Interosseous membrane  ○ Distal attachment: dorsal aspect of base of proximal phalanx of thumb ○ Innervation:Posterior Interosseous nerve (C7, C8) continuation of deep branch of radial nerve ○ Muscle action: extends proximal phalanx of thumb at interphalangeal joint; extends metacarpophalangeal and carpometacarpal joint. Nerves of the forearm Median: ○ Origin: by Union of lateral root of median nerve (C6, C7; lateral cord of brachial plexus) with medial root (C8, T1) from medial cord ○ Course in forearm: enters cubital fossa medial to brachial artery; exits by passing between the heads of the pronator teres; descends in fascial plane between the flexor digitorium superficialis and profundus. Runs deep to palmaris longus tendon as it approaches flexor retinaculum to transverse carpal plane. Anterior Interosseous: ○ Origin:Median nerve in distal part of cubital fossa ○ Course in forearm: descends on anterior aspect of Interosseous membrane with artery of same name, between Flexor digitorium profundus and flexor palmaris longus, to pass deep to pronator quadratus Palmar cutaneous branch of median nerve : ○ Origin: median nerve in middle to distal forearm, proximal to flexor retinaculum. ○ Course in forearm: passes superficial to flexor reticulum to reach skin of central palm. Ulnar: ○ Origin: Larger terminal branch of medial cord of brachial plexus (C8, T1 often receiving fibers from C7) ○ Course in forearm: enters forearm by passing between heads of flexor carpi ulnaris, after passing posterior to medial epicondyle of humerus; descends forearm between flexor carpi ulnaris and flexor digitorium profundus,becoming superficial in distal forearm. Palmar cutaneous branch of ulnar nerve: ○ Origin: ulnar nerve near middle of forearm ○ Course in forearm:descends anterior to ulnar artery; perforates deep fascia in distal forearm; runs in subcutaneous tissue to palmar skin medial to axis of 4th digit Dorsal cutaneous branch of ulnar nerve: ○ Origin: ulnar nerve in distal half of forearm ○ Course in forearm: passes posterioinferiorly between ulna and flexor carpi ulnaris; enters subcutaneous tissue to supply skin of Doris, medial to axis of the 4th digit. Radial: ○ Origin: larger terminal branch of posterior cord of brachial plexus (C5-T1) ○ Course in forearm: enters cubital fossa between brachioradialis and brachialis; anterior lateral epicondyle divides into terminal superficial and deep branches Posterior cutaneous nerve of forearm: ○ Origin: radial nerve, as it transverse radial groove of posterior humerus  ○ Course in forearm: perforates lateral head of triceps; descends along lateral side of arm and posterior aspect of forearm to wrist Superficial branch of radial nerve: ○ Origin: sensory terminal branch of radial nerve in cubital fossa ○ Course in forearm: descends between pronator teres and brachioradialis emerging from lateral to arborize over anatomical snuff box and supply skin lateral to axis of 4 digit. Deep branch of radial/posterior Interosseous nerve: ○ Origin: motor terminal branch of radial nerve, in cubital fossa; sensory fibers of wrist joint ○ Course in forearm: deep branch exits cubital fossa winding around neck of the radius, penetrating and supplying Supinator; emerges in posterior compartment of forearm as posterior Interosseous; descends on membrane with artery of same name. Lateral cutaneous nerve of the forearm: ○ Origin: continuation of musculocutaneous nerve distal to muscular branches. ○ Course in forearm: emerges lateral to biceps brachii on brachialis, running initially with cephalic vein; descends along lateral border of forearm and wrist. Medial cutaneous nerve of the forearm: ○ Origin:medial cord of brachial plexus, receiving C8 and T1 Fibers. ○ Course in forearm:perforates deep fascia of arm with basilic vein proximal to cubital fossa; descends medial aspect of forearm in subcutaneous tissue to wrist.