Week 5 Flashcards
Name the superficial and deep muscles in the posterior compartment of the forearm
Superficial: brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, anconeusDeep: supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, extensor indicis
When is the brachioradialis most visible?
When the forearm is half pronated, and flexing at the elbow against resistance
What is the action of the brachioradialis? Why is this of interest?
It produces flexion at the elbow, but as its origin and innervation are characteristic of an extensor muscle, it is classified in the extensor compartment
What is the innervation of the brachioradialis?
Radial nerve
Where are the extensor carpi radialis longus and extensor carpi radialis brevis found?
Laterally in the posterior forearm, the brevis lies deep to the longus
Where do the extensor carpi radialis longus and brevis attach?
II (longus) and III (brevis) metacarpal bones
What is the innervation of the extensor carpi radialis longus and brevis?
Radial nerve
What is the main extensor of the fingers?
The extensor digitorum; it makes up most of the posterior surface of the forearm
What is the action of the extensor digitorum?
Extension of the medial four fingers at the metacarpalpholangeal and interphalangeal joints of the hand
What is the innervation of the extensor digitorum?
Radial nerve
Describe the location of the extensor digiti minimi relative to the extensor digitorum
Medially, slightly deep
What is the action of the extensor digiti minimi?
Acts to extend the little finger, and also contributes to extension at the wrist
What is the innervation of the extensor digiti minimi?
Radial nerve
Where is the extensor carpi ulnaris found in the forearm
Posterior, medial
Where does the extensor carpi ulnaris attach?
The base of metacarpal V
What is the action of the extensor carpi ulnaris? What is its innervation?
Extends and adducts the wrist; the radial nerve
Which muscle is most medial of those in the extensor compartment of the forearm?
The anconeus
Which other muscle can it be hard to distinguish the anconeus from?
The anconeus is blended with the fibres of the triceps brachii
What is the action of the anconeus? What is its innervation?
Acts to move the ulna during pronation and extends at the elbow joint; radial nerve
What is wrist drop a characteristic sign of?
Radial nerve injury in the axilla or radial groove
What happens in wrist drop?
No radial innervation of extensors at wrist; they are paralysed. Unnoposed flexion (wrist drop) occurs due to action of flexor muscles (median nerve)
What is the action of the supinator? What is its innervation?
Supinates the forearm; radial nerve
Which border of the anatomical snuffbox does the abductor pollicis longus contribute to?
Lateral border
Describe the location of the abductor pollicis longus
Distal to the supinator on the lateral side of the forearm
What is the action of the abductor pollicis longus? What is its innervation?
Abducts the thumb; radial nerve
What is the position of the extensor pollicis brevis relative to the abductor pollicis longus?
Medial
Apart from the abductor pollicis longus, which muscle makes up most of the lateral border of the anatomical snuffbox?
Extensor pollicis brevis
What is the action of the extensor pollicis brevis? What is its innervation?
Extend the metacarpophlanageal and carpometacarpal joints of the thumb; radial nerve
What is the action of the extensor pollicis longus? What is its innervation?
Extends all the joints of the thumb; radial nerve
What is the action of the extensor indices? Why is it important?
Extends the index finger; allows the index finger to be independent of the other fingers during extension
What is the innervation of the extensor indices?
Radial nerve
What type of joints are the radioulnar joints? What movement do they allow?
They are both synovial pivots, responsible for the pronation and supination of the forearm
What is the proximal radioulnar joint formed by?
The head of the radius, articulating with the radial notch of the ulna
Which ligament keeps the radius in place at the proximal radioulnar joint?
The anular radial ligament; it forms a collar around the joint
Which muscles produce pronation at the radioulnar joints?
The pronator teres and pronator quadratus
Which muscles produce supination at the radioulnar joints?
The biceps brachii, and the supinator
What is the distal radioulnar joint formed by?
The head of the ulnar and the ulnar notch on the medial side of the radius
Which ligaments strengthen the distal radioulnar joint?
The anterior (palmar radioulnar) and posterior (dorsal radioulnar) ligaments, and the articular ligament
What are the functions of the articular ligament at the distal radioulnar joint?
It binds the radius and ulna together, holding them together during movement of the joint; it separates the distal radioulnar joint from the wrist joint
What is the anatomical snuffbox?
Triangular depression found on the lateral aspect of the dorsum of the hand, at the level of the carpal bones
What is the lateral border of the anatomical snuffbox?
Tendons of the abductor pollicis longus and extensor pollicis brevis
Which structure is of importance in the anatomical snuffbox?
The radial nerve; it passes diagonally through the anatomical snuffbox on its path into the hand
What is the medial border of the anatomical snuffbox?
Tendon of the extensor pollicis longus
What is the proximal border of the anatomical snuffbox?
Styloid process of the radius
What is the base of the anatomical snuffbox?
Scaphoid and trapezium carpal bones
What articulation occurs in the anatomical snuffbox?
Scaphoid and radius articulate to form part of the wrist joint
Which bones articulate to form the wrist joint?
Distal end of radius, and proximal row of carpal bones (except pisiform)
Which three general things contribute to the stability of the wrist joint?
Joint capsule, structure of the joint, and associated ligaments
Describe the two layers of the wrist joint capsule
Fibrous outer layer attaches to the radius, ulna and proximal carpal bones; the internal layer is comprised of a synovial membrane, secreting synovial fluid which lubricates the joint
At the wrist joint, which bony landmark prevents excessive abduction?
Styloid process of the radius
Name the four important ligaments at the wrist joint
Palmar radiocarpal, dorsal radiocarpal, ulnar collateral, radial collateral
Describe the structure and function of the palmar radiocarpal ligament
Found on the anterior side of the hand; passes from the radius to both rows of carpals; adds to stability and ensures hand follows forearm during supination
Describe the structure and function of the dorsal radiocarpal ligament
Found on the posterior side of the hand; passes from the radius to both rows of carpals; contributes to stability and ensures that hand follows forearm during pronation
Describe the location of the ulnar collateral ligament
Runs from the styloid process to the triquetrum
Describe the location of the radial collateral ligament
Runs from the styloid process to the scaphoid
What type of joint is the wrist joint? What movements does it allow?
Synovial ellipsoid; allows for movement along two axes (flexion /extension, adduction/abduction)
Which muscles produce flexion at the wrist joint?
Mainly the flexor carpi radialis and flexor carpi ulnaris, with assistance from the flexor digitorum superficialis, flexor digitorum profundus and palmaris longus
Which muscles produce extension at the wrist joint?
Mainly the extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris, with assistance from the extensor digitorum, extensor pollicis longus and extensor indicis
Which muscles produce adduction at the wrist joint?
Extensor carpi ulnaris and flexor carpi ulnaris
Which muscles produce abduction at the wrist joint?
Abductor pollicis longus, flexor carpi radilias, extensor carpi radialis longus and brevis
How can you suffer an anterior dislocation of the lunate? What can this cause?
Falling on a dorsiflexed wrist; can compress carpal tunnel, causing carpal tunnel syndrome. The lunate can also undergo avascular necrosis
What will happen if there is damage to the radial nerve at the radial groove?
Wrist drop; (unopposed flexion), the radial nerve innervates the extensors. There will be some sensory loss over the dorsal (posterior) surface of the hand and the proximal ends of the lateral 3 and a half fingers dorsally
What are the motor innervations and hence functions of the radial nerve?
Triceps brachii muscle (extension at elbow), posterior compartment of forearm (extension of wrist, and hand joints, and supination)
What motor function loss occurs with damage to the radial nerve in the axilla?
Triceps and muscles in posterior compartment of forearm are paralysed; inability to extend at elbow, wrist, or fingers; unopposed flexion – wrist drop
Why can supination still occur when the radial nerve is damaged?
Action of biceps brachii, innervated by the musculotaneous nerve
What sensory loss will there be with damage to the radial nerve in the axilla?
Whole of cutaneous innervation of radial nerve; most of the back of the arm and hand
How is the radial nerve most commonly damaged in the radial groove?
Midshaft humeral fracture
Why is extension at the elbow still possible in patients with damage to the radial nerve in the radial groove?
Majority of branches have already arisen is the triceps brachii not paralysed with damage
What motor function is lost with damage to the radial nerve in the radial groove?
Extension at the wrist and hand (muscles in posterior compartment paralysed), wristdrop occurs
What sensory loss occurs with damage to the radial nerve in the radial groove?
Forearm cutaneous branches have already arisen, so there is only sensory loss on the dorsum of the hand
How is the deep branch of the radial nerve in the forearm damaged?
Fractures of the radial head, or posterior dislocation of the radius at the elbow joint
Which muscles of the posterior compartment are NOT damaged with damage to the deep branch of the radial nerve in the forearm?
Supinator and extensor carpi radialis longus; wristdrop will not occur (ECRL is a strong extensor)
What sensory loss occurs with damage to the deep branch of the radial nerve in the forearm?
None, it is a motor nerve
How is the superficial radial nerve commonly damaged in the forearm?
Stabbing/laceration
What motor loss occurs with damage to the superficial radial nerve in the forearm?
None, it is a sensory nerve
What type of joint is the elbow? Which actions can it perform?
Synovial hinge; extension and flexion
Which muscles perform extension at the elbow joint?
Triceps brachii and anconeus
Which muscles perform flexion at the elbow?
Brachialis, biceps brachii and brachioradialis
What are the thickenings at the medial and lateral sides of the joint capsule? What purpose do they serve?
Collateral ligaments; stabilise the joint
Describe the location of the radial collateral ligament of the elbow joint
Found on the lateral side, extending from the lateral epicondyle, and blending with the anular ligament
Describe the location of the ulnar collateral ligament of the elbow
Originates from the medial epicondyle, attaches to coronoid process and olecranon of ulna
Name the three important bursae of the elbow joint
Intratendinosus, subtendinous, subcutaneous
Where is the intratendinous bursa of the elbow joint formed?
Within the tendons of the triceps brachii
Where is the subtendinous bursa of the elbow joint found?
Between the olecranon and the tendon of the triceps brachii, reducing friction between the two structures during extension and flexion of the forearm
Where is the subcutaneous bursa of the elbow joint found?
Between the olecranon and overlying connective tissue
Describe subcutaneous bursitis of the elbow
Repeated friction and pressure causes the bursa to become inflamed; because it is relatively superficial it can also become infected and cause inflammation
Describe subtendinous bursitis of the elbow
Caused by repeated flexion and extension of the forearm, commonly seen in assembly line workers; usually flexion is more painful because more pressure is put on the bursa
How does dislocation of the elbow joint usually occur in young children?
Fall on hand with elbow flexed
Describe what happened during an elbow dislocation in a young child. Where does the humerus go? Which ligament is usually torn? Which nerve is at risk?
Distal end of humerus driven through weakest part of the joint capsule, the anterior side; the ulnar collateral ligament is usually torn, and the ulnar nerve can be involved
What is the most common direction of elbow dislocation?
Posterior (elbow dislocations named by position of ulna and radius, not humerus)
What is ‘tennis elbow’?
Pain and inflammation in and around the lateral epicondyle, from the common extensor tendinous origin; an overuse strain
What is ‘golfer’s elbow’?
Pain and inflammation in and around the medial epicondyle, from the common flexor tendinous origin; an overuse strain
What is a ‘pulled’ elbow? Describe what happens
Subluxation or dislocation of the articulating surface of the bones forming the proximal radio-ulnar joint; the injury results when a person is lifted by the upper limb with the forearm in a pronated position; the pulling of the upper limb tears the distal attachment of the annular ligament (surrounding the radial head) where it is loosely attached to the neck of the radius; the radial head moves distally and out of the torn ligament
Why is a ‘pulled’ elbow more common in children?
The radial head an annular ligament have not fully formed
Why is supination more powerful than pronation?
Strength of the biceps brachii is greater than the pronators
Which bony structure can be palpated around the elbow?
Medial and lateral epicondyles, olecranon process of ulna and head of radius
