Anatomy of The Forearm And Ellbow Dr Fadel

Anatomy of The Forearm And Ellbow Dr. Fadel Naim Orthopedic Surgeon IUG

Extensor Muscles of the Forearm • In the posterior (extensor-supinator) compartment of the forearm • All are innervated by the radial nerve • Three functional groups: 1. Muscles that extend abduct or adduct the hand at the wrist joint » Extensor carpi radialis longus » Extensor carpi radialis brevis » Extensor carpi ulnaris 2. Muscles that extend the medial four digits » Extensor digitorum » Extensor indicis » Extensor digiti minimi 3. Muscles that extend or abduct the thumb » Abductor pollicis longus [APL] » Extensor pollicis brevis [EPB] » Extensor pollicis longus [EPL]

Posterior compartment: Superficial group 1. Extensor carpi radialis brevis 2. Extensor digitorum 3. Extensor digiti minimi 4. Extensor carpi ulnaris 5. Anconeus muscle Posterior compartment: Deep group 1. Supinator 2. Abductor pollicis longus 3. Extensor pollicis brevis 4. Extensor indicis Attached by a common extensor tendon to the lateral epicondyle

Brachioradialis • Origin – Proximal two-thirds of lateral supracondylar ridge of humerus • Insertion – Lateral surface of distal end of radius • Action – Flexes forearm • Innervation – Radial nerve (C 5, C 6, and C 7)

Brachioradialis • This fusiform muscle forms the lateral border of the cubital fossa • Exceptional among muscles of the "posterior" (extensorsupinator) compartment in that – It flexes the forearm at the elbow » Especially when quick movement is required and when a weight is lifted during slow flexion of the forearm. – The brachioradialis and the supinator are the only muscles of the compartment that do not cross the wrist. • To test the brachioradialis: – The elbow joint is flexed against resistance with the forearm in the midprone position. – If acting normally, the muscle can be seen and palpated.

Anconeus • Origin – lateral epicondyle of humerus • Insertion – olecranon and superior portion of shaft of ulna. • Action – Extension forearm at elbow joint • Nerve supply – radial nerve

Extensor Carpi Radialis Longus • Origin – Lateral supracondyle ridge of humerus • Insertion – Base of 2 rd metacarpal • Action – Extend abduct hand at wrist joint • Innervation – Radial nerve (C 6 and C 7)

Extensor Carpi Radialis Longus • To test the extensor carpi radialis longus – The wrist is extended and abducted with the forearm pronated. – If acting normally, » The muscle can be palpated infero-posterior to the lateral side of the elbow. » Its tendon can be palpated proximal to the wrist.

Extensor Carpi Radialis Brevis • Origin – Lateral epicondyle of humerus • Insertion – Base of 3 rd metacarpal • Action – Extend abduct hand at wrist joint • Innervation – Deep branch of radial nerve (C 7 and C 8)

• The extensor carpi radialis brevis and longus act together to steady the wrist during flexion of the medial four digits.

Extensor Digitorum • Origin – Lateral epicondyle of humerus • Insertion – Extensor expansions of medial four digits • Action – Extends medial four digits at metacarpophalangeal joints; Extends hand at wrist joint • Innervation – Posterior interosseous nerve (C 7 and C 8), the continuation of the deep branch of the radial nerve

Extensor Digitorum • The principal extensor of the medial four digits • Its four tendons proximal pass through a common synovial sheath, deep to the extensor retinaculum with the tendon of the extensor indicis • Adjacent tendons are linked by intertendinous connections. • Because of presence of the intertendinous connections extension of one finger is impossible • The index finger has greater freedom because its tendon is not connected to the other tendons

Extensor Digitorum • To test the extensor digitorum: – The forearm is pronated and the fingers are extended. – The person attempts to keep the fingers extended at the metacarpo-phalangeal joints as the examiner exerts pressure on the proximal phalanges by attempting to flex them – If acting normally, the extensor digitorum can be palpated in the forearm, and its tendons can be seen and palpated on the dorsum of the hand.

Extensor Digiti Minimi • Origin – Lateral epicondyle of humerus • Insertion – Extensor expansion of 5 th digit • Action – Extends 5 th digit at metacarpophalangeal and interphalangeal joints • Innervation – Posterior interosseous nerve (C 7 and C 8), the continuation of the deep branch of the radial nerve

Extensor Digiti Minimi • This fusiform slip of muscle is a partially detached part of the extensor digitorum. • The tendon of this extensor of the little finger runs through a separate compartment deep to the extensor retinaculum • Then divides into two slips; – The lateral one is joined to the tendon of the extensor digitorum

Extensor Carpi Ulnaris • Origin – Lateral epicondyle of humerus and posterior border of ulna • Insertion – Base of 5 th metacarpal • Action – Extends and adducts hand at wrist joint • Innervation – Posterior interosseous nerve (C 7 and C 8), the continuation of the deep branch of the radial nerve

Extensor Carpi Ulnaris • Distally, its tendon runs in a groove between the ulnar head and the styloid process • Extends and adducts the hand at the wrist joint simultaneously when acting independently • Acting with the extensor carpi radialis, radialis it extends the hand • Acting with the flexor carpi ulnaris, ulnaris it adducts the hand • Like the extensor carpi radialis longus, it is indispensable when making the fist. • To test the extensor carpi ulnaris: – The forearm is pronated and the fingers are extended. The extended wrist is then adducted against resistance. – If acting normally: » The muscle can be seen and palpated in the proximal part of the forearm

Supinator • Origin – Lateral epicondyle of humerus – radial collateral and annular ligaments – supinator fossa and crest of ulna • Insertion – surface of proximal 1/3 of radius » Lateral » Posterior » Anterior • Action – Supinates forearm • Innervation – Deep branch of radial nerve (C 5 and C 6)

Abductor pollicis Longus • Origin: – Posterior surfaces of » Ulna » Radius » Interosseous membrane • Insertion: – Base of 1 st metacarpal • Action: – Abducts thumb – Extends it at carpometacarpal joint • Innervation: – Posterior interosseous nerve (C 7 and C 8), the continuation of deep branch of radial nerve

Abductor Pollicis Longus • It acts with the abductor pollicis brevis during abduction of the thumb • With the extensor pollicis during extension of this digit. • To test the APL: – The thumb is abducted against resistance at the metacarpophalangeal joint. – If acting normally the tendon of the muscle can be seen and palpated » At the lateral side of the snuffbox and on the lateral side of the adjacent EPB tendon.

Extensor Pollicis Brevis • Origin – Posterior sufraces of radius and interosseous membrane • Insertion – Base of proximal phalanx of thumb • Action – Extends proximal phalanx of thumb at carpometacarpal joint • Innervation – Posterior interosseous nerve (C 7 and C 8), the continuation of the deep branch of the radial nerve

Extensor Pollicis Longus • Origin – Posterior surface of middle 1/3 of ulna and interosseous membrane • Insertion – Base of distal phalanx of thumb • Action – Extends distal phalanx of thumb at carpometacarpal and interphalangeal joints – Adducts the extended thumb and rotates it laterally • Innervation – Posterior interosseous nerve (C 7 and C 8), the continuation of the deep branch of the radial nerve

Extensor Pollicis Longus • The tendon of the EPL passes medial to the dorsal tubercle of the radius, using it as a trochlea changing its line of pull as it proceeds to the base of the distal phalanx of the thumb. . • To test the EPL: – The thumb is extended against resistance at the interphalangeal Joint. – If acting normally, the tendon of the muscle can be seen and palpated on the medial side of the anatomical snuff box

Extensor Indicis • Origin – Posterior sufrace of ulna – interosseous membrane • Insertion – Extensor expansion of 2 nd digit • Action – Extends 2 nd digit and helps to extend hand • Innervation – Posterior interosseous nerve (C 7 and C 8), the continuation of the deep branch of the radial nerve

Arteries of Forearm • 1 brachial – 2 radial » 3 radial recurrent » 4 superficial radial » 5 deep radial – 6 ulnar » 7 anterior ulnar recurrent » 7 posterior ulnar recurrent » 8 common interosseous • 9 posterior interosseous • 10 anterior interosseous » 11 superficial branch » 12 deep branch • In the hand, the ulnar and radial arteries anastomose, formiug the superficial and deep palmar arterial arches.

Ulnar Artery • The larger of the two terminal branches of the brachial artery • Begins in the cubital fossa just medial to the biceps tendon • Descends through the anterior compartment of the forearm, deep to the pronator teres. • Then passes distally over the anterior aspect of the wrist to the palm.

Ulnar Artery • Pulsations of the artery can be palpated on the lateral side of the flexor carpi ulnaris tendon, where it lies anterior to the ulnar head. • The ulnar nerve is on the medial side of the ulnar artery

Branches of the Ulnar Artery in the Forearm 1. – – Anterior and posterior ulnar recurrent Just distal to elbow joint Anterior ulnar recurrent artery passes superiorly Posterior ulnar collateral artery passes posteriorly Anastomose with ulnar collateral and interosseous recurrent arteries

Branches of the Ulnar Artery in the Forearm 2. Common interosseous artery: – – 3. Just distal to bifurcation of brachial artery After a short course, terminates by dividing into anterior and posterior interosseous arteries Anterior and posterior interosseous arteries: – Pass to anterior and posterior sides of interosseous membrane – Anterior interosseous artery supplies both anterior and posterior compartments in distal forearm – The posterior interosseous artery gives off the recurrent interosseous artery » Participates in the arterial anastomoses

Branches of the Ulnar Artery in the Forearm 4. Dorsal and palmar carpal branches – Anastomose with corresponding branches of radial artery to form dorsal and palmar carpal arches, providing collateral circulation at wrist

Radial Artery Ø Ø Ø Smaller than the ulnar artery Begins in the cubital fossa near the neck of the radius It passes inferolaterally deep to the brachioradialis The course of the radial artery in the forearm is represented by a line joining the midpoint of the cubital fossa to a point just medial to the radial styloid process The radial artery leaves the forearm by winding around the lateral aspect of the wrist and crosses the floor of the anatomical snuff box

The Branches Of The Radial Artery 1. Radial recurrent artery – – 2. Lateral side of radial artery, just distal to its origin Ascends on supinator and then passes between brachioradialis and brachialis Dorsal and palmar Radial artery at level of wrist • Anastomose with corresponding branches of ulnar artery to form dorsal and palmar carpal arches

Median Nerve • The median nerve is the principal nerve of the anterior compartment of the forearm • It enters the forearm with the brachial artery and lies on its medial side. • It leaves the cubital fossa by passing between the heads of the pronator teres • The nerve then passes deep to the FDS and continues distally through the middle of the forearm, between the FDS and the FDP.

• Near the wrist, the median nerve becomes superficial by passing between the tendons of FDS and flexor carpi radialis, deep to the palmaris longus tendon

Branches of the Median Nerve • No branches in the arm, other than small twigs to the brachial artery • The branches of the median nerve arise in the forearm and hand as follows: 1. Articular branches to the elbow joint 2. Muscular branches supply: 1. The pronator teres 2. Pronator quadratus 3. All the flexor muscles • Except the flexor carpi uluaris and the medial half of the FDP.

The anterior interosseous nerve 3. The anterior interosseous nerve – Arises from the median nerve in the distal part of the cubital fossa – Passes distally on the interosseous membrane with the anterior interosseous branch of the ulnar artery. – It runs between the FDP and flexor pollicis longus to reach the pronator quadratus. • It supplies these muscles – The FDP » {lateral half sending tendons to digits 2 and 3) } – Flexor pollicis longus – Pronator quadratus • Sends articular branches to the wrist joint.

4. The recurrent branch of the median nerve (C 8 and T 1): • • Arises from the median nerve as soon as it passes distal to the flexor retinaculum. It loops around the distal border of this retinaculum to supply thenar muscles.

5. Palmar coetaneous branch of the median nerve. The course of nerve may vary in 4 important ways 1. Normally, the nerve branches off 5 cm proximal to the wrist It runs along the ulnar side of the tendon of the flexor carpi radialis before crossing the flexor retinaculum. » The nerve divides into two major branches, medial and lateral, while crossing the flexor retinaculum to supply the skin of thenar eminence 2. Less often, the nerve arises from the median nerve in two distinct branches, which travel separately across the wrist. 3. The nerve may arise within the carpal tunnel and penetrate the flexor retinaculum to supply the skin of thenar eminence. 4. The nerve may be absent, replaced by a branch derived from the radial nerve, the musculocutaneous nerve, or the ulnar nerve.

• At the distal border of the flexor retinaculum, the median nerve divides into two branches – The medial branch: » sends cutaneous branches to the adjacent sides of the ring and middle fingers, and to the adjacent sides of the middle and index fingers. – The lateral branch » sends cutaneous branches to the radial side of the index finger and to both sides of the thumb

Ulnar Nerve • It passes posterior to the medial epicondyle of the humerus, humerus

Ulnar Nerve • The ulnar nerve enters the forearm bypassing between the heads of the flexor carpi ulnaris

Ulnar Nerve • It then passes inferiorly between the flexor carpi ulnaris and FDP, – supplying the ulnar (medial) part of the muscle that sends tendons to digits 4 and 5. • The ulnar nerve becomes superficial at the wrist and supplies skin on the medial side of the hand

Ulnar Nerve • The ulnar nerve runs on the medial side of the ulnar artery and the lateral side of the flexor carpi ulnaris tendon. • At this level, the anatomic arrangement of these structures can be remembered by the mnemonic “ANT”: – The artery is the most lateral structure, then the nerve, and, finally, the tendon of the flexor carpi ulnaris

The Canal Of Guyon • As the ulnar nerve crosses the flexor retinaculum in the canal of guyon, , guyon it is covered with a tough fibrous tissue that is continuous with the deep fascia of the forearm, the volar carpal ligament • The boundaries of the canal of gyuon: – The floor » The flexor retinaculum (transverse carpal ligament) – The medial wall » The pisiform – The lateral wall » The hamate – The roof, » The volar carpal ligament (distal fascia of the forearm

Branches of the Ulnar Nerve ü Has no branches in the arm. 1. Articular branches pass to the elbow joint 2. Muscular branches supply: 1. The flexor carpi ulnaris 2. The medial half of the FDP 3. The palmar cutaneous branch • Arises from the ulnar nerve near the middle of the forearm • Supply skin on the medial part of the palm

4. The dorsal cutaneous branch – Arises from the ulnar nerve in the distal half of the forearm Passes posteroinferiorly between the ulna and the flexor carpi ulnaris Supply the posterior surface of the medial part of the hand the digits – – 5. The deep branch – – Arises from the ulnar nerve at the wrist It supplies » » » The hypothenar muscles (muscles of little finger The interosseous muscles The 3 rd and 4 th lumbrical muscles

Ulnar Innervated Muscles • Forearm: – Flexor Carpi Ulnaris (C 7, C 8, T 1) – Flexor Digitorum Profundus III & IV (C 7, C 8) • Thenar: – Hypothenar Muscles (C 8, T 1) – Adductor Pollicis (C 8, T 1) – Flexor Pollicis Brevis (C 8, T 1) • Fingers: – Palmer Interosseous (C 8, T 1) – Dorsal Interosseous (C 8, T 1) – III & IV Lumbricles (C 8, T 1) • Digiti Minimi: – Abductor Digiti Minimi (Quinti) (C 8, T 1) – Opponens Dgiti Minimi (C 8 -T 1) – Flexor Digiti Minimi. : ( C 8 -T 1)

Ulnar Nerve Injury at Wrist • At the wrist, of the tendon of the flexor carpi ulnaris, the ulnar artery, and the ulnar nerve is particularly vulnerable to damage by lacerations. • When falling through a window with the ulnar border of the wrist flung forward to protect the face

The Anatomical Snuff Box • Anteriorly – The tendons of the APL and EPB • Posteriorly – The tendon of the EPL • The snuff box is visible when the thumb is fully extended • This produces a concavity between the tendons

The Anatomical Snuff Box • The radial artery lies in the floor of the snuff box • Radial styloid process can be palpated proximally • The base of the 1 st metacarpal can be palpated distally in the snuffbox • Scaphoid and trapezium can be felt in the floor between the radial styloid process and the 1 st metacarpal.

Radial Nerve • The radial nerve cross the anterior aspect of the lateral epicondyle of the humerus • It appears in the cubital fossa between the brachialis and brachioradialis. • Soon after it enters the forearm, the radial nerve divides into deep and superficial branches

Branches of the Radial Nerve 1. The superficial branch of the radial nerve – – – A cutaneous and articular nerve that descends in the forearm under cover of the brachioradialis. It emerges in the distal part of the forearm and crosses the roof of the anatomical snuff box Distributed to skin on the dorsum of the hand to a number of joints in the hand

Radial Nerve 2. The deep branch of the radial nerve – The larger of the two terminal branches – The direct continuation of the radial nerve – The deep branch arises anterior to the lateral epicondyle of the humerus and pierces the supinator – It winds around the lateral aspect of the neck of the radius and enters the posterior compartment of the forearm

Radial Nerve 3. The posterior interosseous nerve – The continuation of the deep branch of the radial nerve. 4. The posterior cutaneous nerve of the forearm – Descends along the posterior aspect of the forearm to the wrist, supplying the skin during its course.

Lateral epicondylitis (tennis elbow) • An overuse injury commonly seen in tennis players. • The common extensor tendon: – Gives rise to: » The extensor carpi radialis brevis » Extensor digitorum » Extensor digiti minimi » Extensor carpi ulnaris muscles • With repetitive strain, the tendon, periosteum, or radial collateral ligament may become inflamed. • Treatment is rest and avoidance of precipitating activities.

Medial epicondylitis (golfer or pitcher elbow) • Less common than lateral epicondylitis. • It is an overuse injury due to repetitive strain of the common flexor tendon. – – – The pronator teres Flexor carpi radialis Palmaris longus Flexor carpi ulnaris Flexor digitorum superficialis • In some instances an avulsion fracture of the medial epicondyle can mimic medial epicondylitis and should be ruled out with a radiograph. • Treatment is avoidance of precipitating activities.

Veins of the Forearm • In the forearm, as in the arm, are superficial and deep veins • The superficial veins ascend in the subcutaneous tissue. • The deep veins accompany the deep forearm (antebrachial) arteries.

Superficial Veins of The Forearm • The main superficial veins of the forearm are the: 1. 2. 3. 4. • Cephalic vein Basilic vein Median cubital vein Antebrachial vein The cephalic vein: – – – Forms over the anatomical snuff box from the tributaries that arise from the lateral side of the dorsal venous network (arch). Ascends along the lateral border of the forearm and communicates with the basilic vein through the median cubital vein. Ascends along the lateral side of the arm and empties into the axillary vein.

Superficial Veins of The Forearm • The basilic vein: – Arises from the medial side of the dorsal venous arch – Ascends posteromedially in the forearm, forearm reaching the anterior surface just distal to the elbow – Where it is joined by the median cubital vein. • The median antebrachial vein: – Drains subcutaneous tissue in the anterior aspect of the wrist and forearm. – It begins in the superficial venous palmar arch and usually ends in the basilic vein

Deep Veins of The Forearm • Deep veins accompanying the arteries are plentiful in the forearm • Arise from a deep venous arcade in the hand. • Anastomose freely with each other. • Communicate with the superficial veins. • The deep interosseous veins unite with the accompanying veins of the radial and ulnar arteries. • The deep veins in the cubital fossa are connected to the median cubital vein • These deep cubital veins also unite with the accompanying veins of the brachial artery

Interosseous Membrane • The interosseous membrane connects the interosseous margins of the radius and ulna, forming the interosseous syndesmosis • A proximal hole for the posterior interosseus artery to enter the posterior compartment of the forearm • A distal hole for the anterior interosseus artery.

Interosseous membrane • The radius forms the load-bearing articulation with the wrist • The ulna forms the load-bearing articulation with the humerus. • The load thus needs to be transferred from the wrist to the elbow across the interosseous membrane. • The general direction of the fibers of the interosseous membrane is such that a superior thrust to the hand is received by the radius and is transmitted to the ulna.

Oblique Cord • The oblique cord is an inconstant fascial band coursing from the lateral ulnar tuberosity to the radius (just distal to the radial tuberosity) • It has no known function and can be cut without apparent consequence.

Articulation of the Elbow Joint • A hinge type of synovial joint • Articulation: – The humerus » The spool shaped trochlea » The spheroidal capitulum – The trochlear notch of the ulna – The slightly concave superior aspect of the head of the radius ØHumeroulnar articulation ØHumeroradial articulation

Articulation of the Elbow Joint • The articular surfaces, covered with hyaline cartilage, cartilage • Fully congruent when the forearm is in a position midway between pronation and supination and is flexed to a right angle.

Articular Capsule of the Elbow Joint • Continuous inferiorly with the synovial membrane of the superior radioulnar joint. • weak anteriorly and posteriorly • strengthened on each side by collateral ligaments

Articular Capsule of the Elbow Joint • The fibrous capsule • Attached at the margins of the lateral and medial ends of the articular surfaces of the capitulum and trochlea • Anteriorly and posteriorly it is carried superiorly, proximal to the coronoid and olecranon fossae. • Continuous inferiorly with the synovial membrane of the superior radioulnar joint. • weak anteriorly and posteriorly • strengthened on each side by collateral ligaments.

Ligaments of the Elbow Joint • The collateral ligaments of the elbow joint are strong triangular bands – Medial and lateral thickenings of the fibrous capsule

The lateral, fanlike radial collateral ligament • Extends from the lateral epicondyle of the humerus and blends distally with the anular ligament of the radius

The medial, triangular ulnar collateral ligament • Extends from the medial epicondyle of the humerus to the coronoid process and olecranon of the ulna • Consists of three bands: 1. The anterior cordlike band is the strongest 2. The posterior fanlike band is the weakest 3. The slender oblique band deepens the socket for the trochlea of the humerus

Carrying Angle – The long axis of the fully extended ulna makes an angle of approximately 170 ° with the long axis of the humerus – The carrying angle is more pronounced (approximately 10° more acute) in women than men. – The carrying angle disappears when the forearm is pronated

Muscles Moving the Elbow Joint • Several muscles cross the elbow and extend to the forearm and hand: • Chief flexors of the elbow joint – Brachialis – Biceps brachii – Brachioradialis • Chief extensors of the elbow joint – Triceps brachii » Especially medial head, assisted by anconeus

Blood and Nerve Supply of the Elbow Joint • The arteries supplying the elbow joint are derived from the anastomosis around the elbow joint. • The elbow joint is supplied by: – The musculocutaneous nerve – The radial nerve – The ulnar nerve

Bursae Around the Elbow Joint • The three olecranon bursae are the: 1. Intratendinous olecmnon bursa » Which is sometimes present in the tendon of triceps brachii 2. Subtendinous olecranon bursa » Which is located between the olecranon and the triceps tendon, just proximal to its attachment to the olecranon 3. Subcutaneous olecranon bursa » Which is located in the subcutaneous connective tissue over the olecranon.

Bursae Around the Elbow Joint • The radioulnar bursa lies between: – – The extensor digitorum The radiohumeral articulation The supinator muscle. This bursa lies posterior to the supinator, lateral to the tendon of the biceps, and medial to the ulna. • The bicipitoradial bursa (biceps bursa) – Lies between » The biceps tendon » The anterior part of the radial tuberosity.

Dislocation of the Elbow Joint • Posterior dislocation of the elbow joint – Fall on their hands with elbow flexed. • The distal end of the humerus is driven through the weak anterior part of the fibrous capsule – The radius and ulna dislocate posteriorly. • The ulnar collateral ligament is often torn • An associated fracture of the: – – Head of the radius Coronoid process Olecranon process of the ulna Injury to the ulnar nerve

Proximal Radioulnar Joint • The proximal radioulnar joint is a pivot type of synovial joint – allows movement of the head of the radius on the ulna

Proximal Radioulnar Joint • The head of the radius articulates with the radial notch of the ulna. • The radial head is held in position by the anular ligament.

Articular Capsule of the Proximal Radioulnar Joint • The fibrous capsule encloses the joint and is continuous with that of the elbow joint • The synovial membrane lines the deep surface of the fibrous capsule and nonarticulating aspects of the bones. • The synovial membrane is an inferior prolongation of the synovial capsule of the elbow joint.

Ligaments of the Proximal Radioulnar Joint • Anular ligament – Attached to the ulna anterior and posterior to its radial notch, notch surrounds the articulating bony surfaces forming a collar or loop – With the radial notch, notch forms a ring that completely encircles the head of the radius.

Ligaments of the Proximal Radioulnar Joint • Anular ligament – The deep surface of the anular ligament is lined with synovial membrane, which continues distally as a sacciform recess on the neck of the radius. – This arrangement allows the radius to rotate within the anular ligament without binding, stretching, or tearing the synovial capsule.

Movements of the Proximal Radioulnar Joint • During pronation and supination of the forearm, the head of the radius rotates within the ring formed by the anular ligament and the radial notch of the ulna. • The axis for these movements passes: – Proximally through the center of the head of the radius – Distally through the site of attachment of the apex of the articular disc ("triangular ligament") to the head (styloid process) of the ulna.

Movements of the Proximal Radioulnar Joint • During pronation and supination, it is the radius that rotates • Distally, the end of the radius rotates around the head of the ulna • Almost always, supination and pronation are accompanied by synergic movements of the glenohumeral and elbow joints that produce simultaneous movement of the ulna – except when the elbow is flexed.

Muscles Moving the Proximal Radioulnar Joint • Pronation – The pronator quadratus (primarily) – Pronator teres (secondarily) – With some assistance from the FCR, PL, and brachioradialis » (when the forearm is in the midprone position)

Muscles Moving the Proximal Radioulnar Joint • Supination: – The supinator (when resistance is absent) – The biceps brachii (when power is required because of resistance) – With some assistance from the: EPL and ECRL

Blood and Nerve Supply of the Proximal Radioulnar Joint • The proximal radioulnar joint is supplied by the anterior and posterior interosseous arteries • The proximal radioulnar joint is supplied mainly by the: – Musculocutaneous nerve – Median nerve – Radial nerve • Pronation – median nerve • supination – musculocutaneous and radial nerves.

Subluxation of the Radial Head (pulled elbow) Cause : n Often due to a sudden jerk on the forearm, such as when a child is lifted up by one hand. n The head of the radius subluxes out of the annular ligament.

Subluxation of the Radial Head (pulled elbow) Treatment : n It can be reduced by supinating the forearm sharply.

Madelung’s Deformity • Abnormality of the palmar ulnar part of the distal radial physis • Progressive ulnar and volar tilt develops at the distal radial articular surface, with dorsal subluxation of the distal ulna

Congenital Radioulnar Synostosis

Distal Radioulnar Joint • A pivot type of synovial joint. • The radius moves around the relatively fixed distal end of the ulna. • The head of the ulna articulates with the ulnar notch on the medial side of the distal end of the radius.

Distal Radioulnar Joint • A pivot type of synovial joint. • The radius moves around the relatively fixed distal end of the ulna. • The head of the ulna articulates with the ulnar notch on the medial side of the distal end of the radius. n During pronation and supination, the distal end of the radius moves anteriorly and medially, crossing the ulna anteriorly.

Triangular Ligament • A fibrocartilaginous articular disc ("triangular ligament") binds the ends of the ulna and radius together • The main uniting structure of the joint – The base is attached to the medial edge of the ulnar notch of the radius, radius – The apex is attached to the lateral side of the base of the styloid process of the ulna. • The articular disc separates the cavity of the distal radioulnar joint from the cavity of the wrist joint.

Ligaments of the Distal Radioulnar Joint • Anterior and posterior ligaments strengthen the fibrous capsule of the distal radioulnar joint. • These relatively weak transverse bands extend from the radius to the ulna across the anterior and posterior surfaces of the joint

• Movements of the Distal Radioulnar Joint – During pronation and supination, the distal end of the radius moves anteriorly and medially, crossing the ulna anteriorly. • Blood Supply of the Distal Radioulnar Joint – The anterior and posterior interosseous arteries supply the distal radioulnar joint • Innervation of the Distal Radioulnar Joint – The anterior and posterior interosseous nerves supply the distal radioulnar joint.