Elbow, forearm and wrist Flashcards
Summarise the bones of the elbow, forearm and wrist
The Humerus
The Radius
The Ulna
The carpal bones
Proximal row: scaphoid, lunate, triquetrum, pisiform
Distal row: trapezium, trapezoid, capitate, hamate
Which structure serves as an important attachment for the forearm muscles
The epicondyles
Which major structures pass between the arm and the forearm
Proximally, most major structures pass between the arm and forearm through, or in relation to, the cubital fossa, which is anterior to the elbow joint (Fig. 7.77). The exception is the ulnar nerve, which passes posterior to the medial epicondyle of the humerus
What does the bony framework of the forearm consist of
The bone framework of the forearm consists of two parallel bones, the radius and the ulna (Figs. 7.77 and 7.78B). The radius is lateral in position and is small proximally, where it articulates with the humerus, and large distally, where it forms the wrist joint with the carpal bones of the hand.
The ulna is medial in the forearm, and its proximal and distal dimensions are the reverse of those for the radius: the ulna is large proximally and small distally. Proximal and distal joints between the radius and the ulna allow the distal end of the radius to swing over the adjacent end of the ulna, resulting in pronation and supination of the hand.
What does the elbow joint consist of
The elbow joint is a complex joint involving three separate articulations, which share a common synovial cavity (Fig. 7.71).
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The joints between the trochlear notch of the ulna and the trochlea of the humerus and between the head of the radius and the capitulum of the humerus are primarily involved with hinge-like flexion and extension of the forearm on the arm and, together, are the principal articulations of the elbow joint.
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The joint between the head of the radius and the radial notch of the ulna, the proximal radio-ulnar joint, is involved with pronation and supination of the forearm.
What are the 3 fossae of the humerus and what is their function
Radial: immediately superior to the capitulum
Coronoid: superior to the trochlea anteriorly
Olecranon: superior to the trochlea posteriorly
These three fossae accommodate projections from the bones in the forearm during movements of the elbow joint.
Describe the radial tuberosity at the proximal end of the radius
The radial tuberosity is a large blunt projection on the medial surface of the radius immediately inferior to the neck. Much of its surface is roughened for the attachment of the biceps brachii tendon. The oblique line of the radius continues diagonally across the shaft of the bone from the inferior margin of the radial tuberosity.
Describe the olecranon of the ulna
The olecranon is a large projection of bone that extends proximally from the ulna. Its anterolateral surface is articular and contributes to the formation of the trochlear notch, which articulates with the trochlea of the humerus. The superior surface is marked by a large roughened impression for the attachment of the triceps brachii muscle. The posterior surface is smooth, shaped somewhat triangularly, and can be palpated as the “tip of the elbow.”
Describe the coronoid process of the ulna
The coronoid process projects anteriorly from the proximal end of the ulna (Fig. 7.63). Its superolateral surface is articular and participates, with the olecranon, in forming the trochlear notch. The lateral surface is marked by the radial notch for articulation with the head of the radius.
Describe the supinator crest and the tuberosity of the ulna
Just inferior to the radial notch is a fossa that allows the radial tuberosity to change position during pronation and supination. The posterior margin of this fossa is broadened to form the supinator crest. The anterior surface of the coronoid process is triangular, with the apex directed distally, and has a number of roughenings for muscle attachment. The largest of these roughenings, the tuberosity of the ulna, is at the apex of the anterior surface and is the attachment site for the brachialis muscle.
Describe the condyles of the humerus
Condoyle: most distal part of the bone, which acts as an articular plate for the bones of the forearm
Capitulum (Lateral): articulates with the radius of the forearm - largely anterior
Trochlea (Medial): articulates with the ulna, and is a smooth anterior to posterior ridge
Describe the epicondyles of the humerus
Epicondyles: medial and lateral bony protuberances
Lateral epicondyle: smaller, lateral to capitulum and rough to allow attachment of muscles in the posterior compartment of the arm
Medial epicondyle: larger, medial to the trochlea, and roughened for attachment of anterior compartment muscles; ulnar nerve passes along posterior surface
Supracondylar ridges: are proximal to their respective epicondyles
What are the articular surfaces of the elbow joint covered in
Hyaline cartillage
Where does the synovial membrane of the elbow joint originate from
The synovial membrane originates from the edges of the articular cartilage and lines the radial fossa, the coronoid fossa, the olecranon fossa, the deep surface of the joint capsule, and the medial surface of the trochlea
Describe the synovial membrane and fat pads of the elbow joint
The synovial membrane is separated from the fibrous membrane of the joint capsule by pads of fat in regions overlying the coronoid fossa, the olecranon fossa, and the radial fossa. These fat pads accommodate the related bony processes during extension and flexion of the elbow. Attachments of the brachialis and triceps brachii muscles to the joint capsule overlying these regions pull the attached fat pads out of the way when the adjacent bony processes are moved into the fossae.
Describe the fibrous membrane of the elbow joint capsule
The fibrous membrane of the joint capsule overlies the synovial membrane, encloses the joint, and attaches to the medial epicondyle and the margins of the olecranon, coronoid, and radial fossae of the humerus (Fig. 7.73). It also attaches to the coronoid process and olecranon of the ulna. On the lateral side, the free inferior margin of the joint capsule passes around the neck of the radius from an anterior attachment to the coronoid process of the ulna to a posterior attachment to the base of the olecranon.
Describe the reinforcements of the elbow joint
The fibrous membrane of the joint capsule is thickened medially and laterally to form collateral ligaments, which support the flexion and extension movements of the elbow joint
In addition, the external surface of the joint capsule is reinforced laterally where it cuffs the head of the radius with a strong anular ligament of the radius. Although this ligament blends with the fibrous membrane of the joint capsule in most regions, they are separate posteriorly. The anular ligament of the radius also blends with the radial collateral ligament.
The anular ligament of the radius and related joint capsule allow the radial head to slide against the radial notch of the ulna and pivot on the capitulum during pronation and supination of the forearm.
Describe the deep surface of the fibrous membrane of the elbow joint
The deep surface of the fibrous membrane of the joint capsule and the related anular ligament of the radius that articulate with the sides of the radial head are lined by cartilage. A pocket of synovial membrane (sacciform recess) protrudes from the inferior free margin of the joint capsule and facilitates rotation of the radial head during pronation and supination.
Describe the separation of the anterior and posterior compartments in the forearm
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a lateral intermuscular septum, which passes from the anterior border of the radius to deep fascia surrounding the limb;
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an interosseous membrane, which links adjacent borders of the radius and ulna along most of their length; and
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the attachment of deep fascia along the posterior border of the ulna.
What are the two ridges running down the anterior and posterior of the radius?
Anterior Oblique Line
Posterior Oblique line
Describe the interosseous membrane of the forearm
The interosseous membrane separates the anterior and posterior compartments, and is a site of attachment for muscles in the forearm.
Name the carpal bones.
1st row – scaphoid, lunate, triquetrum, pisiform
2nd row – hamate, capitate, trapezoid, trapezium
What is important to remember about the pisiform
it is a sesamoid bone, and so is not involved in articulation at the wrist joint
embedded in a tendon or a packet of muscle
It is within the flexor carpi ulnaris tendon
The patella is also a sesamoid bone
Which muscles in the anterior compartment of the arm act over the elbow joint and what are they innervated by
Biceps
Brachialis
Coracobrachialis (does not act over elbow)
Musculocutaneous nerve (C5,C6)
Describe the functions of the biceps and brachialis
Biceps- Flexor of the forearm at the elbow (accessory flexor of arm at GHJ)
Brachialis- Flexor of the forearm at the elbow joint
Which muscles in the posterior compartment of the arm act over the elbow joint and what are they innervated by
Triceps
Anconeus
Radial nerve (C7,8)
Describe the functions of the triceps and anconeus muscles
Triceps- Extension of the forearm at the elbow joint
Anconeus- Extension and stabilisation of the forearm at the elbow joint
Summarise the muscles of the forearm
The hand and wrist are operated by ‘remote control’ by these muscles
The forearm muscles actually take origin from the distal humerus as well as the radius and ulna
Flexors (and pronators) anteriorly
Extensors (and supinators) posteriorly
What can the anterior compartment of the forearm be divided into
A superficial and deep compartment
List the muscles found in the superficial anterior compartment of the forearm
Pronator teres (PT) Flexor carpi radialis (FCR) Palmaris longus (PL) Flexor digitorum superficialis (FDS) Flexor carpi ulnaris (FCU)
List the muscles found in the deep anterior compartment of the forearm
Flexor digitorum profundus (FDP) Flexor pollicis longus (FPL) Pronator quadratus (PQ)
Describe the proximal and distal attachments of the flexor carpi ulnaris
Proximal: Humeral head: medial epicondyle of humerus
Ulnar head: olecranon and posterior border of ulna
Distal: Pisiform bone, and then via pisohamate and pisometacarpal ligaments into the hamate and base of metacarpal V
Describe the innervation and function of the flexor carpi ulnaris
Innervation- Ulnar nerve (C7-T1)
Function- Flexes and adducts the wrist joint
Describe the proximal and distal attachments of the palmaris longus muscle
proximal- Medial epicondyle of humerus
Distal- palmar aponeurosis of hand
Describe the function and innervation of the palmaris longus muscle
Median nerve (C7-8) Flexes wrist joint;
Contraction of the muscle resists shearing forces when gripping
What is important to remember about the palmaris longus muscle
The palmaris longus muscle, which is absent in about 15% of the population
Attaches to palmar aponeurosis and flexor retinaculum
However palmar aponeurosis exists even if the palmaris longus is not present- so it’s not simply an extension of the palmaris longus tendon
You can test for the palmaris longus muscle by asking the patient to oppose their thumb and flex the wrist joint (if present you will see a tendon pop out in the middle of the wrist)
Describe the proximal and distal attachments of the flexor carpi radialis
Proximal- Medial epicondyle of humerus
Distal- Base of metacarpals II and III
Describe the function and innervation of the flexor carpi radialis
Median nerve (C6-7) Flexes and abducts the wrist
What is important to remember about the flexor carpi radialis
Unlike the tendon of the flexor carpi ulnaris, which forms the medial margin of the distal forearm, the tendon of the flexor carpi radialis muscle is positioned just lateral to the midline. In this position, the tendon can be easily palpated, making it an important landmark for finding the pulse in the radial artery, which lies immediately lateral to it.
Describe the proximal and distal attachments of the pronator teres muscle
proximal: Humeral head: medial epicondyle and epicondylar ridge
Ulnar head: medial side of coronoid process
Distal: Lateral surface of radius midshaft
Describe the function and innervation of the pronator teres muscle
Median nerve (C6-7) Pronation
What is important to remember about the pronator teres muscle
The median nerve often exits the cubital fossa by passing between the humeral and ulnar heads of this muscle
Doesn’t cross the wrist joint.
The pronator teres forms the medial border of the cubital fossa and rotates the radius over the ulna during pronation
Describe the proximal and distal attachments of the flexor digitorium superficialis
Proximal; Humero-ulnar head—medial epicondyle of humerus and adjacent margin of coronoid process; radial head—oblique line of radius
Distal: Four tendons, which attach to the palmar surfaces of the middle phalanges of the index, middle, ring, and little fingers
Describe the innervation and function of the flexor digitorium superficialis
Innervation: Median nerve (C8, T1)
Function: Flexes proximal interphalangeal joints of the index, middle, ring, and little fingers; can also flex metacarpophalangeal joints of the same fingers and the wrist joint
What is important to remember about the flexor digitorium superficialis
The median nerve and ulnar artery pass deep to the flexor digitorum superficialis between the two heads.
In the distal forearm, the flexor digitorum superficialis forms four tendons, which pass through the carpal tunnel of the wrist and into the four fingers. The tendons for the ring and middle fingers are superficial to the tendons for the index and little fingers.
In the forearm, carpal tunnel, and proximal regions of the four fingers, the tendons of the flexor digitorum superficialis are anterior to the tendons of the flexor digitorum profundus muscle.
Near the base of the proximal phalanx of each finger, the tendon of the flexor digitorum superficialis splits into two parts to pass posteriorly around each side of the tendon of the flexor digitorum profundus and ultimately attach to the margins of the middle phalanx
Describe the proximal and distal attachments of the flexor digitorium profundus
Proximal: Anterior and medial surfaces of ulna and anterior medial half of interosseous membrane
Distal: Four tendons, which attach to the palmar surfaces of the distal phalanges of the index, middle, ring, and little fingers
Describe the function and innervation of the flexor digitorium profundus
Innervation: Lateral half by median nerve (anterior interosseous nerve); medial half by ulnar nerve (C8, T1)
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The lateral half (associated with the index and middle fingers) is innervated by the anterior interosseous nerve (branch of the median nerve).
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The medial half (the part associated with the ring and little fingers) is innervated by the ulnar nerve.
Function: Flexes distal interphalangeal joints of the index, middle, ring, and little fingers; can also flex metacarpophalangeal joints of the same fingers and the wrist joint
What is important to remember about the flexor digitorium profundus
It gives rise to four tendons, which pass through the carpal tunnel into the four medial fingers. Throughout most of their course, the tendons are deep to the tendons of the flexor digitorum superficialis muscle.
Opposite the proximal phalanx of each finger, each tendon of the flexor digitorum profundus passes through a split formed in the overlying tendon of the flexor digitorum superficialis muscle and passes distally to insert into the anterior surface of the base of the distal phalanx.
In the palm, the lumbrical muscles originate from the sides of the tendons of the flexor digitorum profundus
Describe the proximal and distal attachments of the flexor pollicis longus
Proximal: Anterior surface of radius and radial half of interosseous membrane
Distal: Palmar surface of base of distal phalanx of thumb
Describe the innervation and function of the flexor pollicis longus
Innervation: Median nerve (anterior interosseous nerve) (C7, C8)
Function: Flexes interphalangeal joint of the thumb; can also flex metacarpophalangeal joint of the thumb
Describe the passage of the flexor pollicis longus through the carpal tunnel
It is a powerful muscle and forms a single large tendon, which passes through the carpal tunnel, lateral to the tendons of the flexor digitorum superficialis and flexor digitorum profundus muscles, and into the thumb where it attaches to the base of the distal phalanx.
Describe the proximal and distal attachments of the pronator quadratus muscle
Proximal: Linear ridge on distal anterior surface of ulna
Distal: Distal anterior surface of radius
Describe the innervation and function of the pronator quadratus muscle
Innervation: Median nerve (anterior interosseous nerve) (C7, C8)
Function: Pronation
Summarise the extensor compartment of the forearm
Muscles that move the wrist joint
Extensor carpi radialis longus (ECRL)
Extensor carpi radialis brevis (ECRB)
Extensor carpi ulnaris (ECU)
Muscles that move the digits
Extensor digitorum (ED)
Extensor indicis (EI)
Extensor digit minimi (EDM)
Muscles that move the thumb
Abductor pollicis longus (APL)
Extensor pollicis brevis (EPB)
Extensor pollicis longus (EPL)
Other muscles
Brachioradialis
Supinator
Describe the proximal and distal attachments of the brachioradialis muscle
proximal:Proximal part of lateral supraepicondylar ridge of humerus and adjacent intermuscular septum
Distal: Lateral surface of distal end of radius
Describe the innervation and function of the brachioradialis muscle
Innervation: Radial nerve (C5, C6) before division into superficial and deep branches
Function: Accessory flexor of elbow joint when forearm is midpronated- In the anatomical position, the brachioradialis is part of the muscle mass overlying the anterolateral surface of the forearm and forms the lateral boundary of the cubital fossa.
Because the brachioradialis is anterior to the elbow joint, it acts as an accessory flexor of this joint even though it is in the posterior compartment of the forearm
Describe the proximal and distal attachments of the extensor carpi radialis longus
Proximal: Distal part of lateral supraepicondylar ridge of humerus and adjacent intermuscular septum
Distal: Dorsal surface of base of metacarpal II
Describe the innervation and function of the extensor carpi radialis longus
Innervation: Radial nerve (C6, C7) before division into superficial and deep branches
Function; Extends and abducts the wrist
Describe the relationship of the extensor carpi radialis muscle with the brachioradialis
In proximal regions, it is deep to the brachioradialis muscle.
Describe the proximal and distal attachments of the extensor carpi radialis brevis muscle
Proximal: Lateral epicondyle of humerus and adjacent intermuscular septum
Distal: Dorsal surface of base of metacarpals II and III
Describe the innervation and function of the extensor carpi radialis brevis muscle
Innervation: Deep branch of radial nerve (C7, C8) before penetrating supinator muscle
Function: Extends and abducts the wrist
Describe the proximal and distal attachments of the extensor digitorium muscle
Proximal: Lateral epicondyle of humerus and adjacent intermuscular septum and deep fascia
Distal: Four tendons, which insert via extensor hoods into the dorsal aspects of the bases of the middle and distal phalanges of the index, middle, ring, and little fingers
Describe the innervation and function of the extensor digitorium muscle
Innervation: The extensor digitorum muscle is innervated by the posterior interosseous nerve, which is the continuation of the deep branch of the radial nerve after it emerges from the supinator muscle (C7,C8)
Function:Extends the index, middle, ring, and little fingers; can also extend the wrist
Describe the proximal and distal attachments of the extensor digiti minimi
Proximal: Lateral epicondyle of humerus and adjacent intermuscular septum
Distal: Extensor hood of little finger
Describe the innervation and function of the extensor digiti minimi
Innervation:Posterior interosseous nerve (C7-8)
Function: Extends the little finger
Describe the proximal and distal attachments of the extensor carpi ulnaris
Proximal: Lateral epicondyle of humerus and posterior border of ulna
Distal: Tubercle on the base of the medial side of metacarpal V
Describe the innervation and function of the extensor carpi ulnaris
Innervation: Posterior interosseous nerve (C7-8)
Function: Extends and adducts the wrist
Describe the proximal and distal attachments of the anconeus muscle
Proximal: Lateral epicondyle of humerus
Distal: Olecranon and proximal posterior surface of ulna
Describe the innervation and function of the anconeus muscle
Innervation: Radial nerve (C6, C7, C8) (via branch to medial head of triceps brachii)
Function: Abduction of the ulna in pronation; accessory extensor of the elbow joint
The anconeus abducts the ulna during pronation to maintain the center of the palm over the same point when the hand is flipped
Summarise the deep muscles of the extensor forearm compartment
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Three of these muscles—the abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus—emerge from between the extensor digitorum and the extensor carpi radialis brevis tendons of the superficial layer and pass into the thumb.
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Two of the three “outcropping” muscles (the abductor pollicis longus and extensor pollicis brevis) form a distinct muscular bulge in the distal posterolateral surface of the forearm.
Describe the proximal and distal attachments of the supinator muscle
Proximal: Superficial part—lateral epicondyle of humerus, radial collateral and anular ligaments; deep part—supinator crest of the ulna
Distal: Lateral surface of radius superior to the anterior oblique line and to the insertion of the pronator teres muscle
Describe the innervation and function of the supinator muscle
Innervation: Posterior interosseous nerve (C6, C7)
Function: Supination
Describe the proximal and distal attachments of the abductor pollicis longus muscle
Proximal: Posterior surfaces of ulna and radius (distal to the attachments of supinator and anconeus), and intervening interosseous membrane
Distal: Lateral side of base of metacarpal I
Describe the innervation and function of the abductor pollicis longus muscle
Innervation: Posterior interosseous nerve (C7, C8)
Function: Abducts carpometacarpal joint of thumb; accessory extensor of the thumb (metacarpal I and trapezium bones)
Describe the passage of the abductor pollicis longus muscle
In the distal forearm, it emerges between the extensor digitorum and extensor carpi radialis brevis muscles to form a tendon that passes into the thumb and inserts on the lateral side of the base of metacarpal I. The tendon contributes to the lateral border of the anatomical snuffbox at the wrist.
Describe the proximal and distal attachments of the extensor pollicis brevis muscle
Proximal: Posterior surface of ulna (distal to the abductor pollicis longus) and the adjacent interosseous membrane
Distal: Dorsal surface of base of distal phalanx of thumb
Describe the innervation and function of the extensor pollicis brevis muscle
Innervation: Posterior interosseous nerve (C7, C8)
Function: Extends interphalangeal joint of the thumb; can also extend carpometacarpal of the thumb
Describe the passage of the extensor pollcis brevis
Together with the abductor pollicis longus, it emerges between the extensor digitorum and extensor carpi radialis brevis muscles to form a bulge on the posterolateral surface of the distal forearm. The tendon of the extensor pollicis brevis passes into the thumb and inserts on the dorsal surface of the base of the proximal phalanx. At the wrist, the tendon contributes to the lateral border of the anatomical snuffbox.
Describe the proximal and distal attachments of the extensor pollicis longus
Proximal: Posterior surface of ulna (distal to the abductor pollicis longus) and the adjacent interosseous membrane
Distal: Dorsal surface of base of distal phalanx of thumb
Describe the innervation and function of the extensor pollicis longus
Innervation: Posterior interosseous nerve (C7, C8)
Function: Extends interphalangeal joint of the thumb; can also extend carpometacarpal and metacarpophalangeal joints of the thumb
Describe the passage of the extensor pollicis longus
Like the abductor pollicis longus and extensor pollicis brevis, the tendon of this muscle emerges between the extensor digitorum and the extensor carpi radialis brevis muscles. However, it is held away from the other two deep muscles of the thumb by passing medially around the dorsal tubercle on the distal end of the radius. The tendon forms the medial margin of the anatomical snuffbox at the wrist.
Describe the proximal and distal attachments of the extensor indicis muscle
proximal: Posterior surface of ulna (distal to extensor pollicis longus) and adjacent interosseous membrane
Distal: Extensor hood of index finger
Describe the innervation and function of the extensor indicis muscle
Innervation: Posterior interosseous nerve (C7, C8)
Function: Accessory extensor of index finger
