2. MSK p148-154 (Trauma/Acquired - Upper Limbs)

Question 1

Stress fracture - definition

Answer 1

Abnormal stress on normal bone

Question 2

Insufficiency fracture - definition

Answer 2

Normal stress on abnormal bone

Question 3

Bone healing - features (2)

Answer 3

Takes 6-8 weeks usually (months for tibia).
Osteolytic phase precedes new bone formation.

Question 4

Scaphoid fractures - trivia (3)

Answer 4

Most common carpal bone fracture.
70% occur at the waist.
Avulsion fractures most common at distal pole.

Question 5

Scaphoid fracture -complications (4)

Answer 5

Proximal fractures most prone to AVN and non-union.
Blood supply is distal to proximal, so proximal pole is most prone to AVN.
First sign of AVN is sclerosis (dead bone can’t turnover).
AVN appearance on MRI is disputed. Most reliable sign is dark on T1.

Question 6

SLAC wrist - definition/cause (2)

Answer 6

Scapho-lunate advanced collapse.
Occurs due to scapho-lunate ligament injury.

Question 7

SNAC wrist - definition/cause (2)

Answer 7

Scaphoid Non-union Advanced Collapse.
Occurs due to scaphoid fracture.

Question 8

SLAC/SNAC wrist - anatomy/complications (4)

Answer 8

Scaphoid wants to rotate in flexion, prevented by scapho-lunate ligament.
If this ligament is injured, the radial scaphoid space will narrow and the capitate will migrate proximally.
Radio scaphoid joint is therefore the first to develop degenerative changes.
Capitate migrates proximally, eventually leading to DISI

Question 9

SLAC wrist Rx (2)

Answer 9

Depends on occupation of pt and their needs.
- Wrist fusion: Max strength, loss of ROM
- Proximal row carpectomy: Maintain ROM, loss of strength

Question 10

Carpal dislocation - spectrum (8)

Answer 10

Scapholunate dissociation:
- SL >3mm, clenched fist view exaggerates this.
- Chronic SL dissociation leads to SLAC wrist.
Perilunate dislocation
- capitate is dorsally displaced, scaphoid and lunate correctly positioned
- 60% associated with scaphoid fractures.
Midcarpal dislocation
- Lunate is ventrally dislocated & capitate dorsally dislocated. Scaphoid is correct.
- Associated with triquetriolunate interosseous ligament disruption and with triquetrial fracture
Lunate dislocation
- lunate ventrally dislocated, scaphoid and capitate OK
- Happens with dorsal radiolunate ligament injury

Question 11

DISI deformity (5)

Answer 11

Dorsal intercalated segmental instability.
Associated with Radial Sided Injury (Scapholunate side).
Lunate becomes free of stabilising force of scaphoid, and can rock dorsally.
SL injury is common, so this is common.
Causes widening of the SL angle (>60 degrees).

Question 12

VISI deformity (5)

Answer 12

Volar intercalated segmental instability.
Associated with ulnar sided injury (Lunotriquetrial side).
Lunate no longer stabilised by lunotriquetrial ligament, and gets tilted volar by the scaphoid.
LT injury less common, so this is less common.
Causes narrowing of the SL angle (<30 degrees)

Question 13

Bennett vs Rolando fractures (3)

Answer 13

Both fractures of base of first metacarpal.
Rolando is comminuted, Bennet is not.
Dorsolateral dislocation of Bennett fracture is caused by pull of the Adductor Pollicis Longus tendon.

Question 14

Gamekeeper’s thumb (3)

Answer 14

Avulsion fracture of base of first proximal phalanx, with ulnar collateral ligament (UCL) disruption.
Stener lesion - adductor tendon gets caught in the torn edges of the UCL. Displaced ligament won’t heal and needs surgery.
Yo-yo appearance on MRI.

Question 15

Carpal Tunnel Syndrome (4)

Answer 15

Median nerve distribution (thumb to radial aspect of 4th digit), often bilateral and may have thenar muscle atrophy.
Enlargement of median nerve on USS.
Usually due to repetitive trauma.
Also associated with dialysis.

Question 16

Guyon’s canal syndrome (3)

Answer 16

Entrapment of ulnar nerve as it passes through Guyon’s canal (formed by pisiform and hamate).
Classically caused by handle bars (handle bar palsy).
Fracture of hook of hamate can also damage ulnar nerve.

Question 17

Elbow/forearm fractures trivia (3)

Answer 17

Radial head fractures commonest in adults.
Supracondylar fractures commonest in kids (Sail sign, posterior is positive).
Capitulum fractures are associated with posterior elbow dislocation.

Question 18

Essex-lopresti fracture

Answer 18

Radial head fracture with anterior dislocation of the distal radial ulnar joint.

Question 19

Monteggia fracture

Answer 19

Proximal ulnar fracture with anterior dislocation of the radial head.

Question 20

Galeazzi fracture

Answer 20

Radial shaft fracture with anterior dislocation of the ulna at the distal radial ulnar joint.

Question 21

Cubital tunnel syndrome (3)

Answer 21

Due to repetitive valgus stress.
Ulnar nerve passes beneath the cubital tunnel retinaculum at the epicondylo-olecranon ligament or Osbourne band.
Can be due to tumour, haematoma, or accessory muscle, classically anconeus epitrochlearis (accessory anconeus).

Question 22

Shoulder dislocation - types (3)

Answer 22

Anterior - by far most common
Posterior - Uncommon, usually seizure or electrocution
Inferior - Uncommon, Arm sticking above head, 60% nerve injury, usually axillary

Question 23

Anterior shoulder dislocation - imaging (3)

Answer 23

Hill Sachs - posterolateral humeral head impaction fracture (best seen on internal rotation view)
Bankart - Anterior glenoid rim fracture (bony) or anterior inferior labrum tear
Greater tuberosity avulsion fracture (10-15% of over 40s)

Question 24

Posterior shoulder dislocation - imaging (4)

Answer 24

Reverse Hill Sachs (aka trough sign) - anterior humeral head impaction fracture
Reverse bankart - Posterior glenoid rim
Rim sign - no overlap between glenoid and humeral head.
Arm may be locked in internal rotation on all views

Question 25

Proximal humerus fracture (2)

Answer 25

Old lady falling on stretched arm.
Neer classification (how many parts humerus is in), 3 or 4 parts tend to do worse.

Question 26

Shoulder replacement - types & when used (4)

Answer 26

Depends if rotator cuff is intact and if glenoid fossa is intact.
Cuff and Glenoid intact - resurfacing or hemi-arthroplasty
Cuff deficient - Hemi-arthroplasty or reverse total arthroplasty
Glenoid deficient - total shoulder arthroplasty
Cuff and glenoid deficient - reverse shoulder arthroplasty

Question 27

Complications of shoulder replacement (4)

Answer 27

Total shoulder arthroplasty - commonest complication is loosening of glenoid component.
- Can also get “Anterior escape”, anterior migration of humeral head after subscapularis failure
Reverse total shoulder arthroplasty - Posterior Acromion Fracture from excessive deltoid tugging (Reverse relies heavily on deltoid as it doesn’t need intact rotator cuff

Question 28

Femoral neck fractures - trivia (anatomy) (2)

Answer 28

Medial is classic stress fracture location.
Lateral is classic bisphosphonate fracture location.