Anatomy of hand and wrist

Question 1

Describe clinical issues with wrist bones

Answer 1

Scaphoid fractures
- Scaphoid within the wrist
- has minimal soft tissue attachment
- Limited blood supply
- Retrograde supply to proximal pole
- Fracture difficult to diagnose
- Easily missed: b/c not very painful
- Develops avascular necrosis and arthritis untreated
- May require internal fixation

Lunate avascular necrosis,
also known as Keinboch’s disease. Occurs spontaneously in 30-40 year old males.

Other issues include the trapezium developing arthritis, , arthritis developing in the junction between the pisiform and triquetral bones, hook of hamate issue causing tendon rupture.

Question 2

Describe the ligaments of the wrist and hand

Answer 2

There are many ligaments of the wrist.
Proximally is the interosseous membrane between radius and ulna.
Damage e.g. to the wrist results in fractures e.g. anterior dislocation of radial head.
The most clinically significant one (for now) is the radioscapholunate ligament, which tethers the scaphoid to the lunate.
Scapholunate ligament can tear:
- Fall or twisting Injury
- Sprained or weak wrist
- Clunk or pop with activity, weak wrist
- Predictable arthritic pattern
- Needs repair

Another important ligament is the triangular fibrocartilage complex, which keeps the radius attached to the ulna and provides stability to the wrist.

Key ligaments of the fingers include:
- radial: which prevents the finger going ‘onward’
- ulnar collateral ligaments which prevents the finger moving radially
- volar plate: prevents PIP joint overextension

Damage to the ligaments of the fingers can cause several issues including:
- PIP dislocation, subluxation

Question 3

Describe the carpal tunnel and its contents

Answer 3

The contents of the carpal tunnel are as follows:
- 4 Profundus tendons
- 4 superficialis tendons
- flexor pollicis longus
- median nerve
Carpal bones make up the walls and the floor. The tunnel was roofed by the flexor retinaculum.

Question 4

Describe carpal tunnel syndrome

Answer 4

• Median nerve compression due to either reduced volume or increase in the size of structures passing through the carpal tunnel
• Intermittent paraesthesia median nerve distribution
• Wasting of thenar muscle when severe and longstanding

Question 5

Describe the extensor tendons and tunnel

Answer 5

Extensor reticulum
- Dorsal Surface of the Finger
- EDC extends the Proximal Phalanx
- Central slip from intrinsics extend the Middle phalanx
- Lateral Band extends the distal Phalanx

Extensor Tendons
- Wrist has 6 extensor compartments
- Extensor Retinaculum covers the tendons
- Prevents Bowstringing of the tendons
- Improved mechanical advantage
- Tendons are susceptible to compression friction or attrition rupture within the compartments

Extensor tendons: compartments
1. Abductor Pollicis Longus and Extensor Pollicus Brevus
2. Extensor Carpi Radialis Longus and Brevus
3. Extensor Pollicis Longus
4. Extensor Digitorum Longus and Extensor indicis Proprius
5. Extensor Digiti Minimi
6. Extensor Carpi Ulnaris

Question 6

Descrieb clinical issues with the extensor tendons

Answer 6

De Quervain’s Tendonitis
- Common Cause of radial wrist pain
- Over use or narrow compartment
- Treatment : Rest, Physio, stretching NSAID gel, Injection with Steroid
- Surgery if resistant

Extensor pollicis longus rupture
- Uncommon
- Usually after minimally displaced radial fractures
- Loss of thumb extension
- Treatment : Tendon transfer

Extensor digiti minimi rupture
- EDM passes over the Distal Radio Ulna Joint
- Common in Rheumatoid arthritis
- Three causes of rupture
- Vascular
- Bony spur
- Direct synovial invasion
- Often a warning of further tendon damage
- Treatment:
- Surgery- Synovectomy , re-routing extensor retinaculum and tendon transfer

Question 7

Describe the intrinsic tendons

Answer 7

• Common insertion of Lumbrical Palmar and dorsal Interossei
• Each finger Has a radial and Ulna intrinsic tendon

Flexor tendons and finger pulley system
- Fibrous bands in the finger flexor sheath
- Synovial fluid lubricates the flexor tendon
- Pulleys hold down the flexor tendon to allow full flexion
- Superficialis starts superficial in the finger and spirals around the profundus to insert into the volar middle phalanx

Question 8

Describe the clinical issues associated with the intrisicn tendons

Answer 8

Trigger finger
- Very common
- Almost always at the A1 Pulley
- Catching, locking or pain
- Treatment with rest, anti inflamatories, and injection
- Surgery to release the A1 Pulley

Tendon rupture
- Avulsion of Flexor Tendon FDP
- Need to diagnose early
- Primary repair if within two weeks
- Two stage repair after that
- Even very sore fingers can flex DIP

Question 9

Describe the nerves of the hand and the territory they innervate

Answer 9

Three main nerves:
- median nerve - test with thumb opposition
- Sensory functions: Gives rise to the palmar cutaneous branch, which innervates the lateral aspect of the palm, and the digital cutaneous branch, which innervates the lateral three and a half fingers on the anterior (palmar) surface of the hand.
- Motor functions: Innervates the flexor and pronator muscles in the anterior compartment of the forearm (except the flexor carpi ulnaris and part of the flexor digitorum profundus, innervated by the ulnar nerve). Also supplies innervation to the thenar muscles and lateral two lumbricals in the hand.
- ulnar nerve - finger abduction
- - Motor functions:
- Two muscles of the anterior forearm – flexor carpi ulnaris and medial half of flexor digitorum profundus
- Intrinsic muscles of the hand (apart from the thenar muscles and two lateral lumbricals)
- Sensory functions: Medial one and half fingers and the associated palm area.
- radial nerve - finger MCP extension
- - Sensory – Innervates most of the skin of the posterior forearm, the lateral aspect of the dorsum of the hand, and the dorsal surface of the lateral three and a half digits
- Motor –Innervates the triceps brachii and the extensor muscles in the forearm.