Elbow, forearm and wrist part 2 Flashcards
Summarise the fascia of the wrist
The flexor retinaculum forms the roof of the carpal tunnel
Band of connective tissue that protects the tendons running through it
So when you flex and extend the wrist- the tendons don’t bow out- which would reduce the efficiency of the muscle contraction.
Describe how we can classify the forearm muscles into functional groups
Forearm muscles can be classified into functional groups:
Flexors (anterior) and Extensors (posterior)
Movers of the wrist (the “carpi” muscles) act on the radial (radialis) or ulnar (ulnaris) aspects of the forearm.
Movers of the digits:- act on groups of digits (digitorum muscles) or on individual digits (pollicis (thumb), indicis (index finger) digiti minimi (little finger)) (these muscles also contribute to wrist movements).
Also note that if there’s a longus, there’s a brevis; if there’s a superficialis, there’s a profundus.
The main complications are the muscles involved in pronation (anterior) and supination (posterior).
What is meant by the anatomical snuff box
The “anatomical snuffbox” is a term given to the triangular depression formed on the posterolateral side of the wrist and metacarpal I by the extensor tendons passing into the thumb (Fig. 7.97). Historically, ground tobacco (snuff) was placed in this depression before being inhaled into the nose. The base of the triangle is at the wrist and the apex is directed into the thumb.
Describe the borders of the anatomical snuff box
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The lateral border is formed by the tendons of the abductor pollicis longus and extensor pollicis brevis.
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The medial border is formed by the tendon of the extensor pollicis longus.
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The floor of the impression is formed by the scaphoid and trapezium, and the distal ends of the tendons of the extensor carpi radialis longus and extensor carpi radialis brevis.
Which structures pass through the anatomical snuff box
The radial artery passes obliquely (lateral to medial) through the anatomical snuffbox, deep to the extensor tendons of the thumb and lies adjacent to the scaphoid and trapezium.
Terminal parts of the superficial branch of the radial nerve pass subcutaneously over the snuffbox as does the origin of the cephalic vein from the dorsal venous arch of the hand.
Describe the anatomical importance of the anatomical snuff-box
The anatomical snuffbox is an important clinical region. When the hand is in ulnar deviation, the scaphoid becomes palpable within the snuffbox. This position enables the physician to palpate the bone to assess for a fracture. The pulse of the radial artery can also be felt in the snuffbox.
Important in determining if the scaphoid might be fractured: a common injury.
Commonly fractured when trying to break fall
Blood supply is distal to proximal- so fracture may lead to avascular necrosis of the scaphoid- potential for disability in wrist actions.
What is important to remember about the muscles going to the digit
Can contribute to movement of the wrist
List the four joints in the forearm region
Elbow joint
Proximal radio-ulnar joint
Distal radio-ulnar joint
Wrist joint
What are the borders and surfaces of the radius
Throughout most of its length, the shaft of the radius is triangular in cross section, with:
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three borders (anterior, posterior, and interosseous), and
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three surfaces (anterior, posterior, and lateral).
Describe the borders of the radius
The anterior border begins on the medial side of the bone as a continuation of the radial tuberosity. In the superior third of the bone, it crosses the shaft diagonally, from medial to lateral, as the oblique line of the radius. The posterior border is distinct only in the middle third of the bone. The interosseous border is sharp and is the attachment site for the interosseous membrane, which links the radius to the ulna.
Summarise the surfaces of the radius
The anterior and posterior surfaces of the radius are generally smooth, whereas an oval roughening for the attachment of the pronator teres marks approximately the middle of the lateral surface of the radius.
Viewed anteriorly, the distal end of the radius is broad and somewhat flattened anteroposteriorly (Fig. 7.78). Consequently, the radius has expansive anterior and posterior surfaces and narrow medial and lateral surfaces. Its anterior surface is smooth and unremarkable, except for the prominent sharp ridge that forms its lateral margin.
Describe the key features of the surfaces of the radius
The posterior surface of the radius is characterized by the presence of a large dorsal tubercle, which acts as a pulley for the tendon of one of the extensor muscles of the thumb (extensor pollicis longus). The medial surface is marked by a prominent facet for articulation with the distal end of the ulna (Fig. 7.78). The lateral surface of the radius is diamond shaped and extends distally as a radial styloid process.
What is the distal end of the radius marked by
The distal end of the bone is marked by two facets for articulation with two carpal bones (the scaphoid and lunate).
Summarise the shaft and distal end of the ulna
The shaft of the ulna is broad superiorly where it is continuous with the large proximal end and narrow distally to form a small distal head (Fig. 7.79). Like the radius, the shaft of the ulna is triangular in cross section and has:
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three borders (anterior, posterior, and interosseous), and
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three surfaces (anterior, posterior, and medial).
Describe the borders of the distal ulna
The anterior border is smooth and rounded. The posterior border is sharp and palpable along its entire length. The interosseous border is also sharp and is the attachment site for the interosseous membrane, which joins the ulna to the radius.
Describe the surfaces of the distal ulna
The distal end of the ulna is small and characterized by a rounded head and the ulnar styloid process (Fig. 7.79). The anterolateral and distal part of the head is covered by articular cartilage. The ulnar styloid process originates from the posteromedial aspect of the ulna and projects distally.
Describe the head and neck of the radius
The head of the radius is a thick disc-shaped structure oriented in the horizontal plane. The circular superior surface is concave for articulation with the capitulum of the humerus. The thick margin of the disc is broad medially where it articulates with the radial notch on the proximal end of the ulna.
The neck of the radius is a short and narrow cylinder of bone between the expanded head and the radial tuberosity on the shaft.
Describe the radial tuberosity
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.
What are the main ligaments found at the elbow joint
Radial collateral ligament
Ulnar collateral ligament
Anular ligament
What are the 3 parts of the ulnar collateral ligament
Anterior band (cord-like) Posterior band (fan-like) Oblique band
What is the role of the anular ligament
It goes around just under the head of the radius and it helps hold the radius in place
It allows the radius to rotate
Ultimately, how are the ligaments at the elbow joint arranged
Ligaments at the elbow joint are arranged to stabilise the joint, but allow pronation/supination movements.
What is meant by the carrying angle, and explain how it differs between male and females
Angle between arm and forearm in anatomical position
Men – 10-15 degrees
Women - > 15 degrees
Women have wider hips- explaining why they have a more obtuse carrying angle
Summarise the proximal radio-ulnar joint
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.
Synovial joint- encapsulated by anular ligament of radius
radial head held in place by the anular ligament
Summarise the distal radio-ulnar joint
The distal radio-ulnar joint occurs between the articular surface of the head of the ulna, with the ulnar notch on the end of the radius, and with a fibrous articular disc, which separates the radio-ulnar joint from the wrist joint
Synovial joint
Describe the articular disk of the distal radio-ulnar joint
The triangular-shaped articular disc is attached by its apex to a roughened depression on the ulna between the styloid process and the articular surface of the head, and by its base to the angular margin of the radius between the ulnar notch and the articular surface for the carpal bones.
Describe the synovial membrane of the distal radio-ulnar joint
The synovial membrane is attached to the margins of the distal radio-ulnar joint and is covered on its external surface by a fibrous joint capsule.
What does the distal radio-ulnar joint allow for
The distal radio-ulnar joint allows the distal end of the radius to move anteromedially over the ulna.
What is important to remember about the distal end of the ulna
The distal ulna does not articulate directly with the triquetrum carpal bone. An articular disc intervenes
Describe the articulation of the radius and ulna with the carpal bones.
The distal end of the radius articulates with scaphoid and lunate (more medial)
The distal end of the ulna does not directly articulate with the carpal bones, it articulates with an articular disc
What is the name given to the joint between the first and second rows of carpal bones?
Midcarpal joint
Describe the structure of the interosseous membrane
The interosseous membrane is a thin fibrous sheet that connects the medial and lateral borders of the radius and ulna, respectively (Fig. 7.80). Collagen fibers within the sheet pass predominantly inferiorly from the radius to the ulna.
The interosseous membrane has a free upper margin, which is situated just inferior to the radial tuberosity, and a small circular aperture in its distal third. Vessels pass between the anterior and posterior compartments superior to the upper margin and through the inferior aperture.
Describe the function of the interosseous membrane
The interosseous membrane connects the radius and ulna without restricting pronation and supination and provides attachment for muscles in the anterior and posterior compartments. The orientation of fibers in the membrane is also consistent with its role in transferring forces from the radius to the ulna and ultimately, therefore, from the hand to the humerus.
Describe the anatomy of the wrist joint
The wrist joint is a synovial joint between the distal end of the radius and the articular disc overlying the distal end of the ulna, and the scaphoid, lunate, and triquetrum (Fig. 7.92). Together, the articular surfaces of the carpals form an oval shape with a convex contour, which articulates with the corresponding concave surface of the radius and articular disc.
Which movements does the wrist joint allow
The wrist joint allows movement around two axes. The hand can be abducted, adducted, flexed, and extended at the wrist joint.
Because the radial styloid process extends further distally than does the ulnar styloid process, the hand can be adducted to a greater degree than it can be abducted.
Describe the reinforcement of the wrist joint
process, the hand can be adducted to a greater degree than it can be abducted.
The capsule of the wrist joint is reinforced by palmar radiocarpal, palmar ulnocarpal, and dorsal radiocarpal ligaments. In addition, radial and ulnar collateral ligaments of the wrist joint span the distance between the styloid processes of the radius and ulna and the adjacent carpal bones. These ligaments reinforce the medial and lateral sides of the wrist joint and support them during flexion and extension.
List the muscles responsible for flexion at the elbow joint and the spinal nerve levels involved
Brachialis
Biceps
(Brachioradialis)
(Pronator teres)
C5,6
List the muscles responsible for extension at the elbow joint and the spinal nerve levels involved
Triceps
(Anconeus)
C6,7
Which spinal nerve levels are involved for both flexion and extension at the wrist joint
C6 and C7
Which two movements occur at the radio-ulnar joints
Supination and pronation
List the muscles involved in supination of the radio-ulnar joint
Supinator
Biceps
(EPL, ECRL)
What do pronation and supination involve
Pronation and supination of the hand occur entirely in the forearm and involve rotation of the radius at the elbow and movement of the distal end of the radius over the ulna
Supinated position: palms upwards - ulna and radius are linear and parallel
Pronated position: palms downwards - radius crosses anteromedially over the ulna
What holds the bones together during pronation and supination movements
At the elbow, the superior articular surface of the radial head spins on the capitulum while, at the same time, the articular surface on the side of the head slides against the radial notch of the ulna and adjacent areas of the joint capsule and anular ligament of the radius. At the distal radio-ulnar joint, the ulnar notch of the radius slides anteriorly over the convex surface of the head of the ulna. During these movements, the bones are held together by:
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the anular ligament of the radius at the proximal radio-ulnar joint,
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the interosseous membrane along the lengths of the radius and ulna, and
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the articular disc at the distal radio-ulnar joint
Essentially, which bone moves in pronation and supination
Because the hand articulates predominantly with the radius, the translocation of the distal end of the radius medially over the ulna moves the hand from the palm-anterior (supinated) position to the palm-posterior (pronated) position.
Two muscles supinate and two muscles pronate the hand
Radius essentially pivots over the stationary articular disk of the head of the ulna
Describe the role of the biceps brachii in supination
The biceps brachii muscle, the largest of the four muscles that supinate and pronate the hand, is a powerful supinator as well as a flexor of the elbow joint. It is most effective as a supinator when the forearm is flexed.
The biceps tendon inserts into the radial tuberosity
When prone, the radial tuberosity is turned posteriorly
So then when the biceps contract, it will pull the tuberosity back around
Describe the role of the supinator muscle in supination
The supinator muscle curves around the posterior surface and the lateral surface of the upper third of the radius to attach to the shaft of the radius superior to the oblique line.
The tendon of the biceps brachii muscle and the supinator muscle both become wrapped around the proximal end of the radius when the hand is pronated (Fig. 7.81). When they contract, they unwrap from the bone, producing supination of the hand.
List the muscles involved in pronation and describe how pronation is achieved
Pronator quadratus
Pronator teres
(FCR, PL, brachioradialis)
When these muscles contract, they pull the distal end of the radius over the ulna, resulting in pronation of the hand
Describe the role of the anconeus muscle in pronation and supination
In addition to hinge-like flexion and extension at the elbow joint, some abduction of the distal end of the ulna also occurs and maintains the position of the palm of the hand over a central axis during pronation (Fig. 7.82). The muscle involved in this movement is the anconeus muscle, which is a triangular muscle in the posterior compartment of the forearm that runs from the lateral epicondyle to the lateral surface of the proximal end of the ulna.
List the muscles involved in flexion of the wrist joint
Flexion
FCR and FCU – important
Long flexors of thumb and fingers
(PL, APL)
List the muscles involved in extension of the wrist joint
ECRL, ECRB, ECU – important
Long extensors of the thumb and fingers
List the muscles involved in radial deviation (abduction) of the wrist joint
APL, FCR, ECRL, ECRB
List the muscles involved in ulnar deviation (adduction) of the wrist joint
ECU, FCU
What is important to remember about adduction and abduction of the wrist
Flexors and extensors work together
