Unit 8 Question Bank
Sourcing: items tagged TMU 2021–22 come from the real final paper. Items tagged
Slide come from the TMU lecture. Items tagged Gray's are built from the textbook to cover
examinable content. Nothing here is invented; answers are verifiable against the cited page — check against
the official marking scheme where one exists.
0 / 20 answered
1The floor of the anatomical snuffbox is formed by the ( ).
Answer: A
The scaphoid and trapezium. This is why snuffbox tenderness after a fall on the outstretched hand means a scaphoid fracture until proved otherwise.Gray's 4e p.798 · TMU Lecture 9 Slide 14
2Which structure crosses the floor of the anatomical snuffbox?
Answer: B
The radial artery crosses the floor. The cephalic vein and superficial branch of the radial nerve cross the roof.TMU Lecture 9 Slide 14
3The medial (posterior) border of the anatomical snuffbox is the tendon of ( ).
Answer: C
Extensor pollicis longus forms the medial border; abductor pollicis longus and extensor pollicis brevis form the lateral border.TMU Lecture 9 Slide 14
4Injury to the radial nerve in the spiral groove produces ( ).
Answer: D
Wrist drop, but triceps is spared because its branches leave the nerve before it enters the groove. Preserved elbow extension is how the lesion is localised.TMU Lecture 9 Slide 4 · Gray's 4e p.758
5How many compartments and tendons pass beneath the extensor retinaculum?
Answer: A
Six compartments containing nine tendons, each in a synovial sheath.TMU Lecture 9 Slide 12
6The first extensor compartment contains the tendons of ( ).
Answer: B
Abductor pollicis longus and extensor pollicis brevis — the two tendons inflamed in De Quervain's tenosynovitis.TMU Lecture 9 Slide 13
7The deep branch of the radial nerve pierces which muscle?
Answer: C
It pierces supinator, winds round the neck of the radius, and emerges posteriorly as the posterior interosseous nerve.TMU Lecture 9 Slide 7
8A posterior interosseous nerve lesion differs from a spiral groove lesion in that it ( ).
Answer: D
The posterior interosseous nerve is purely motor, and extensor carpi radialis longus is supplied before the division — so wrist extension is preserved (with radial deviation) and there is no sensory loss.Gray's 4e p.788
9The cephalic vein begins from which part of the dorsal venous network?
Answer: A
The cephalic vein begins at the radial end and the basilic vein at the ulnar end — the same lateral/medial pairing as the saphenous veins in the leg.TMU Lecture 9 Slide 9
10The radial nerve and profunda brachii artery lie together in the ( ).
Answer: B
The radial (spiral) groove — your TMU slide calls it the humeromuscular tunnel — between the lateral and medial heads of triceps, directly on bone.TMU Lecture 9 Slide 4
11Which muscle is NOT in the superficial layer of the posterior forearm?
Answer: C
Supinator is the most proximal muscle of the deep layer. The superficial layer, from the radial side, is ECRL, ECRB, extensor digitorum, extensor digiti minimi and extensor carpi ulnaris.TMU Lecture 9 Slides 5–6
12De Quervain's tenosynovitis affects which extensor compartment?
Answer: D
The first — abductor pollicis longus and extensor pollicis brevis. Pain at the radial wrist, reproduced by ulnar deviation with the thumb tucked in (Finkelstein's test).Snell's 10e Ch.3 (clinical)
13The long head of triceps brachii arises from the ( ).
Answer: A
The infraglenoid tubercle. The supraglenoid tubercle gives origin to the long head of biceps — a pair worth keeping straight.Snell's 10e Ch.3
14Skin over the lateral part of the dorsum of the hand is supplied by the ( ).
Answer: B
The superficial branch of the radial nerve takes the lateral part; the dorsal cutaneous branch of the ulnar nerve takes the medial part, the boundary running roughly down the middle finger.TMU Lecture 9 Slide 10
15The third extensor compartment contains the tendon of ( ).
Answer: C
Extensor pollicis longus, which hooks around the dorsal tubercle of the radius — and is the tendon that may rupture after a Colles' fracture.TMU Lecture 9 Slide 13
16Why is a normal initial X-ray insufficient to exclude a scaphoid fracture?
Answer: D
Scaphoid fractures are frequently invisible on the first film. The blood supply enters distally, so a waist fracture may devascularise the proximal fragment, causing avascular necrosis and non-union. Patients are immobilised and re-imaged in 10–14 days.Gray's 4e p.794 (clinical application)
17Extensor carpi radialis longus is spared in a posterior interosseous nerve lesion because ( ).
Answer: A
Its branch leaves the radial nerve proximal to the division into superficial and deep branches, so wrist extension persists — though with radial deviation, because extensor carpi ulnaris is paralysed.Gray's 4e p.788
18The extensor retinaculum functions to ( ).
Answer: B
It holds the extensor tendons down against the bone so they do not bowstring away from the wrist during extension — the same principle as the flexor retinaculum on the other side.TMU Lecture 9 Slide 12
19Which nerve injury produces a claw hand?
Answer: C
The ulnar nerve supplies most intrinsic hand muscles; their loss leaves the long flexors and extensors unopposed, producing the clawed posture of the medial two fingers.Snell's 10e Ch.3
20'Saturday night palsy' refers to compression of the ( ).
Answer: D
Prolonged pressure on the radial nerve in the spiral groove — classically an arm hung over a chair back while asleep or intoxicated — causing wrist drop.Gray's 4e p.758 (clinical application)
1 Anatomical snuffbox — 3′+
A triangular depression on the lateral part of the proximal dorsum of the hand, visible when the thumb is extended.
Lateral border: tendons of abductor pollicis longus and extensor pollicis brevis.
Medial border: tendon of extensor pollicis longus.
Proximal border: distal end (styloid process) of the radius.
Floor: scaphoid and trapezium.
Contents: the radial artery crosses the floor; the superficial branch of the radial nerve and the beginning of the cephalic vein cross the roof.
Clinical: tenderness here indicates a scaphoid fracture until proved otherwise.TMU Lecture 9 Slide 14 · Gray's 4e p.798
Lateral border: tendons of abductor pollicis longus and extensor pollicis brevis.
Medial border: tendon of extensor pollicis longus.
Proximal border: distal end (styloid process) of the radius.
Floor: scaphoid and trapezium.
Contents: the radial artery crosses the floor; the superficial branch of the radial nerve and the beginning of the cephalic vein cross the roof.
Clinical: tenderness here indicates a scaphoid fracture until proved otherwise.TMU Lecture 9 Slide 14 · Gray's 4e p.798
2 Extensor retinaculum — draw a figure+
A strong transverse fibrous band at the back of the wrist that prevents bowstringing of the extensor tendons.
Septa from its deep surface create six compartments carrying nine tendons in synovial sheaths:
1. abductor pollicis longus + extensor pollicis brevis · 2. extensor carpi radialis longus + brevis · 3. extensor pollicis longus · 4. extensor digitorum + extensor indicis · 5. extensor digiti minimi · 6. extensor carpi ulnaris.TMU Lecture 9 Slides 12–13
Septa from its deep surface create six compartments carrying nine tendons in synovial sheaths:
1. abductor pollicis longus + extensor pollicis brevis · 2. extensor carpi radialis longus + brevis · 3. extensor pollicis longus · 4. extensor digitorum + extensor indicis · 5. extensor digiti minimi · 6. extensor carpi ulnaris.TMU Lecture 9 Slides 12–13
3 Radial (spiral) groove — 3′+
An oblique groove on the posterior surface of the shaft of the humerus, between the lateral and medial heads of triceps brachii, transmitting the radial nerve and the profunda brachii (deep brachial) artery.
Your TMU slide calls it the humeromuscular tunnel.
Clinical: a mid-shaft humeral fracture or prolonged pressure here injures the radial nerve, causing wrist drop with preserved elbow extension.TMU Lecture 9 Slide 4
Your TMU slide calls it the humeromuscular tunnel.
Clinical: a mid-shaft humeral fracture or prolonged pressure here injures the radial nerve, causing wrist drop with preserved elbow extension.TMU Lecture 9 Slide 4
4 Posterior interosseous nerve — 3′+
The continuation of the deep branch of the radial nerve after it pierces supinator and winds round the neck of the radius, descending on the interosseous membrane with the posterior interosseous artery.
It is purely motor, supplying the deep extensors. A lesion causes finger drop with preserved wrist extension and no sensory loss.TMU Lecture 9 Slide 7 · Gray's 4e p.788
It is purely motor, supplying the deep extensors. A lesion causes finger drop with preserved wrist extension and no sensory loss.TMU Lecture 9 Slide 7 · Gray's 4e p.788
5 Wrist drop — 2′+
Inability to extend the wrist and fingers, so the hand hangs limp, caused by injury to the radial nerve — most often in the radial (spiral) groove from a mid-shaft humeral fracture or prolonged pressure.
Triceps is usually spared because its branches leave the nerve before the groove; there is sensory loss over the lateral dorsum of the hand.TMU Lecture 9 Slide 4
Triceps is usually spared because its branches leave the nerve before the groove; there is sensory loss over the lateral dorsum of the hand.TMU Lecture 9 Slide 4
6 Dorsal venous network of the hand — 2′+
A network of superficial veins on the dorsum of the hand, in the superficial fascia.
The cephalic vein arises from its radial end and the basilic vein from its ulnar end. It is the standard site for intravenous cannulation.TMU Lecture 9 Slide 9
The cephalic vein arises from its radial end and the basilic vein from its ulnar end. It is the standard site for intravenous cannulation.TMU Lecture 9 Slide 9
1
Draw and describe the extensor tendons beneath the extensor retinaculum.
8′
Set as the drawing homework in TMU Lecture 9.
The retinaculum
A strong transverse fibrous band at the back of the wrist, continuous with the deep fascia of the forearm. It holds the extensor tendons against the bone and prevents them bowstringing during wrist extension. Septa pass from its deep surface to the radius and ulna, creating six compartments containing nine tendons, each in a synovial sheath.
| Compartment | Tendons |
|---|---|
| 1 | Abductor pollicis longus · extensor pollicis brevis |
| 2 | Extensor carpi radialis longus · extensor carpi radialis brevis |
| 3 | Extensor pollicis longus |
| 4 | Extensor digitorum · extensor indicis |
| 5 | Extensor digiti minimi |
| 6 | Extensor carpi ulnaris |
Clinical points
- De Quervain's tenosynovitis — inflammation of compartment 1
- The tendon of extensor pollicis longus (compartment 3) hooks round the dorsal tubercle of the radius and may rupture after a Colles' fracture
Marking guide: function of the retinaculum 1 · six compartments named 1 · nine tendons correctly allocated 5 · one clinical point 1.
2
Define the anatomical snuffbox and explain its clinical importance.
6′
Definition
A triangular depression on the lateral part of the proximal dorsum of the hand, made visible by extending the thumb.
Boundaries
- Lateral (anterior): tendons of abductor pollicis longus and extensor pollicis brevis
- Medial (posterior): tendon of extensor pollicis longus
- Proximal: styloid process of the radius
- Floor: scaphoid and trapezium
Contents and relations
- The radial artery crosses the floor — its pulse can be felt here
- The superficial branch of the radial nerve and the beginning of the cephalic vein cross the roof
Clinical importance
- Tenderness in the snuffbox indicates a scaphoid fracture until proved otherwise, typically after a fall on the outstretched hand
- The scaphoid's blood supply enters distally, so a fracture through the waist may devascularise the proximal fragment → avascular necrosis and non-union
- The fracture is often invisible on the initial X-ray, so the patient is immobilised and re-imaged in 10–14 days
Marking guide: three borders 2 · floor 1 · radial artery 1 · scaphoid significance 1 · avascular necrosis or delayed imaging 1.
3
Trace the radial nerve through the upper limb and describe the effects of injury at different levels.
8′
Course
- Arises from the posterior cord of the brachial plexus (C5–T1)
- Leaves the axilla through the triangular interval with the profunda brachii artery
- Winds round the back of the humerus in the radial (spiral) groove, between the lateral and medial heads of triceps
- Pierces the lateral intermuscular septum and enters the cubital fossa deep and lateral, under brachioradialis
- At the level of the lateral epicondyle divides into a superficial (sensory) and a deep (motor) branch
- The deep branch pierces supinator and becomes the posterior interosseous nerve
Effects of injury by level
| Level | Motor loss | Sensory loss |
|---|---|---|
| Axilla (e.g. crutch palsy) | Triceps + all extensors — elbow extension lost, wrist drop | Posterior arm, forearm and dorsum of hand |
| Spiral groove (mid-shaft fracture, Saturday night palsy) | Wrist drop; triceps spared | Lateral dorsum of hand |
| Posterior interosseous (radial neck, supinator) | Finger extension lost; wrist extension preserved with radial deviation | None |
The level is localised by two questions: is elbow extension preserved, and is there sensory loss?
Marking guide: course through triangular interval and spiral groove 2 · division at lateral epicondyle 1 · posterior interosseous 1 · three levels of injury with correct deficits 4.
4
Describe the muscles of the posterior compartment of the forearm.
6′
Superficial layer, from the radial side
- Extensor carpi radialis longus
- Extensor carpi radialis brevis
- Extensor digitorum
- Extensor digiti minimi
- Extensor carpi ulnaris
Deep layer, from the radial side
- Supinator
- Abductor pollicis longus
- Extensor pollicis brevis
- Extensor pollicis longus
- Extensor indicis
Common features
- The superficial muscles arise largely from the lateral epicondyle by a common extensor origin — the mirror of the flexors on the medial side
- All are supplied by the radial nerve or its deep branch (the posterior interosseous nerve)
- Blood supply is from the posterior interosseous artery, a branch of the common interosseous from the ulnar artery
Clinical
Lateral epicondylitis (tennis elbow) is degeneration at the common extensor origin, giving pain on resisted wrist extension — the counterpart of golfer's elbow at the flexor origin medially.
Marking guide: superficial layer 2 · deep layer 2 · common origin and nerve 1.5 · one clinical point 0.5.
5
Compare the flexor and extensor retinacula of the wrist.
6′
| Flexor retinaculum | Extensor retinaculum | |
|---|---|---|
| Position | Anterior (palmar) surface of the wrist | Posterior (dorsal) surface of the wrist |
| Attachments | Scaphoid and trapezium laterally; pisiform and hook of hamate medially | Radius laterally; ulnar styloid, triquetral and pisiform medially |
| Forms | Roof of the carpal tunnel | Six osteofibrous compartments |
| Transmits | Nine flexor tendons + the median nerve | Nine extensor tendons |
| Passes superficial | Ulnar nerve and artery; palmaris longus; palmar cutaneous branch of median nerve | Superficial branch of radial nerve; dorsal branch of ulnar nerve; cephalic and basilic veins |
| Classic lesion | Carpal tunnel syndrome — median nerve | De Quervain's tenosynovitis — compartment 1 |
Shared principle
Both are thickenings of deep fascia that hold long tendons against bone, preventing bowstringing as the wrist moves. Both create tunnels that cannot expand — which is precisely why swelling inside them produces compression syndromes.
Marking guide: positions and attachments 2 · contents of each 2 · one structure passing superficial to each 1 · shared functional principle 1.