S10: the upper limb (3)

Question 1

Which bones constitute the wrist joint?

Answer 1

Distal radius
Triangular fibrocartilage complex
Scaphoid
Lunate

Question 2

List factors which stabilise the wrist joint

Answer 2

Ligaments attaching the radius to the carpal bones on the dorsal & palmar surface (radiocarpal ligaments)
-important role in ensuring the hand follows the radius during pronation & supination of the forearm
Ulnar & radial collateral ligaments

Question 3

List the eight carpal bones

Answer 3

Proximal row (radial to ulnar) = scaphoid, lunate, triquetrum, pisiform
Distal row (radial to ulnar) = trapezium, trapezoid, capitate & hamate 
Straight line to pinky, here comes the thumb

Question 4

Describe the blood supply of the scaphoid bone

Answer 4

Major blood supply = dorsal carpal branch of radial artery
Enters the dorsal surface of the scaphoid distally & supplies the proximal 80% of the scaphoid by retrograde flow
Important in understanding why scaphoid fractures have a high rate of non-union

Question 5

Describe the boundaries and contents of the carpal tunnel

Answer 5

Deep border = carpal bones which form a concavity
Superficial border = flexor retinaculum
Structures passing through the carpal tunnel:
1) Flexor pollicis longus tendon
2) Flexor digitorum superficialis tendons x4
3) Flexor digitorum profundus tendons x4
4) Median nerve (palmar cutaneous branch of the median nerve is given off proximal to the carpal tunnel)

Question 6

Describe Guyon’s canal (ulnar canal)

Answer 6

Allows passage of the ulnar nerve & artery into the hand
Superficial to the flexor retinaculum
Site of ulnar nerve compression

Question 7

Describe the borders and contents of the anatomical snuffbox

Answer 7

Radial border = tendons of abductor pollicis longus & extensor pollicis brevis
Ulnar border = tendon of extensor pollicis longus
Proximal border = styloid process of the radius
Floor = scaphoid & trapezium
Roof = skin
Contents = radial artery, superficial branch of radial nerve & cephalic vein

Question 8

Name the origins, insertions, innervations & actions of the thenar eminence

Answer 8

Innervation = median nerve (MEat LOAF)
Opponens pollicis: origin = trapezium & flexor retinaculum, insertion = lateral edge of 1st metacarpal, actions = opposition of thumb
Abductor pollicis brevis: origin = scaphoid, insertion = lateral proximal phalanx of thumb, action = thumb abduction
Flexor pollicis brevis: origin = 1) superficial head -> trapezium & flexor retinaculum, 2) deep head -> capitate & trapezoid, insertion = proximal phalanx of thumb, actions = flexion of MCP joint of thumb

Question 9

Name the origins, insertions, innervations & actions of the adductor pollicis and palmaris brevis muscles

Answer 9

Innervation = ulnar nerve
Adductor pollicis: origin = 1) transverse head -> 3rd metacarpal, 2) oblique head -> capitate & parts of 2nd/3rd metacarpal, insertion = proximal phalanx of thumb, actions = thumb adduction
Palmaris brevis: origin = palmar aponeurosis & flexor retinaculum, insertion = dermis of medial side of hand, actions = winkles the skin of the hypothenar eminence, deeps the curvature of the palm (increasing grip)

Question 10

Name the origins, insertions, innervations & actions of the hypothenar eminence

Answer 10

Origin (except ADM) = hook of hamate & flexor retinaculum
Insertion (except ODM) = base of proximal phalanx of 5th digit
Opponens digiti minimi: insertion = medial border of 5th metacarpal, actions = rotation of little finger towards palm, enabling opposition
Abductor digiti minimi: origin = pisiform & tendon of FCU, actions = abduction of little finger
Flexor digiti minimi brevis: action = flexion of MCP joint of little finger

Question 11

Name the origins, insertions, innervations & actions of the lumbricals

Answer 11

4 lumbricals, one for each finger
Origin = tendon of FDP, then pass dorsally & laterally round their digit
Insertion = extensor hood
Innervation = 1&2 -> median nerve, 3&4 -> ulnar nerve
Actions = flexion at the MCP joint, extension at IP joints

Question 12

Name the origins, insertions, innervations & actions of the interossei

Answer 12

DAB PAD = dorsal abducts, palmar adducts 
Innervation = ulnar nerve
Dorsal interossei (4 muscles): origin = lateral & medial surfaces in between metacarpals, insertion = extensor hoods on each side, action = finger abduction 
Palmar interossei (3 muscles): origin = 1) 1st -> shaft of 1st metacarpal, 2) 2nd/3rd -> shaft of 4th/5th metacarpal respectively, insertion = 1) 1st -> base of proximal phalanx to index finger/extensor expansion, 2) 2nd -> proximal phalanx to ring finger/extensor expansion, 3) 3rd -> proximal phalanx to little finger, actions = finger adduction