Hand Injuries - pediagenosis
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Thursday, September 12, 2019

Hand Injuries

Hand Injuries
Hand injuries are a common presentation to the Emergency Department, and the importance of good hand function in day-to-day life requires excellent results. The spectacular range of hand function relies on complex interplay between muscles, tendons, bones and ligaments, all of which may be damaged.

Metacarpal neck fractures

History and examination
Hand dominance, job and hobbies are essential parts of the history. The mechanism of injury may suggest a likely pattern of injury, e.g. a fifth metacarpal fracture following a fight. If there is no history of injury, consider infection (e.g. septic arthritis) or inflammation (e.g. rheumatoid arthritis).
It can be confusing to describe lesions in relation to the anatomical position, so the terms volar or palmar, and dorsal are used, rather than anterior and posterior. Similarly, radial and ulnar are used rather than medial or lateral. Names of digits (thumb/index/middle/ring/little) should be used, rather than numbers.
Look Look for swelling/bruising and compare hands. Check the skin over the knuckles for wounds: human ‘bites’ need treatment (Chapter 12).
Feel Feel the carpal and metacarpal bones and joints and the ‘anatomical snuff box’ (Chapter 15).
Move Ask the patient to make a fist: check the fingers are in line, pointing to the scaphoid.
        Check sensory and motor function. Two-point discrimination testing can reveal subtle sensory loss.
        Check the extensor and flexor tendon function.
        Test the thumb ligaments.
        Ask the patient to grip your index and middle fingers ‘as tight as they can’.

Immobilise and elevate
Neighbour/buddy strapping involves strapping an injured finger to an adjacent finger, providing protection against hyperextension while still allowing good function.
Volar slab: a strip of plaster on the palmar/volar side of the hand with the wrist in extension and the metacarpophalangeal joints (MCPJs) in flexion provides support and prevents contraction of tendons or muscles.
Multiple layers of elastic or plaster strapping around the thumb is called a thumb ‘spica’, and provides protection against abduction or hyperextension.
The compartments of the hand have little room to accommodate soft tissue swelling, so elevation in a sling is used to keep the hand above the heart. Rings should be removed.
The majority of hand injuries can be managed as outpatients or by GPs; however, open fractures, or those listed below under ‘Do not miss’, should be reviewed by the inpatient team.

Common injuries
Metacarpal neck fractures
Little or ring finger metacarpal neck fractures caused by punch injuries are quite stable. Angulation <30° gives a good functional outcome. If  more  angulated, the  fracture may be  reduced by flexing the MCPJ to 90° and pushing dorsally.

Fractures and dislocations of the phalanges
Dislocations and fractures with marked deformity should be reduced in the Emergency Department using N2O/O2 or a ring block. Mid-shaft or spiral fractures may be unstable due to fracture pattern or muscle action, and require operative fixation, particularly if there is any rotational deformity.

Hammer/mallet finger
Forced flexion of the extended distal phalanx pulls a flake of bone off the distal phalanx. Treat with a mallet splint to ensure the patient does not flex their distal phalanx at all for 6 weeks.

Thenar eminance sprain
The powerful muscles of the thenar eminence can be torn by forced abduction of the thumb – a common injury when falling on a slippery surface, e.g. skiing or skating. More serious injuries, e.g.
Bennett’s/scaphoid fractures must be excluded.

Nail and fingertip injuries
Injuries to the fingertip are common, and require X-ray to exclude bone injury, but rarely need operative treatment. If the nail is displaced, remove under ring block, trim, and use as a dressing for the nailbed. Nailbed injuries rarely need treatment.

Uncomplicated lacerations (that do not involve underlying structures) on the hand and digits less than 2 cm long do not require suturing, providing the wounds are not at high risk of infection (Chapter 12). Clean, dress and consider topical antibiotic ointment. Above this size, sutures are usually used. Ensure that distal neurovascular function is documented.

Fish-hook injury
Fish-hooks have a barb to prevent fish (or humans) from pulling the hook out. After anaesthetising the area, it may be necessary to advance the hook through the skin to cut off the barb and allow removal.

Diagnoses not to miss
Bennett’s fracture
This is a fracture of the base of the thumb or first metacarpal bone, caused by thumb hyperextension. It is unstable and needs operative fixation.

Gamekeeper’s thumb
Gamekeeper’s thumb is a tear of the ulnar collateral ligament of the thumb at MCPJ level by forced abduction. Complete tears do not heal without surgery.

Tendon injuries
Tendon injuries are easy to miss unless the tendons are individually tested. Tendon lacerations can occur when an extensor, or less commonly, a flexor tendon hits a sharp object, particularly when the is running over a bony prominence. Complete tendon division requires operative repair.

Tendon sheath infection
Tendons run in fibrous sheaths that protect and lubricate the tendon. If infection penetrates the sheath, it may track down the finger and into the hand. Such infections need urgent drainage, washout and antibiotic treatment.

All amputations involving bone loss should be referred and reimplantation considered, especially for thumb and index fingers. The amputated part should be wrapped in clean cloth, and then put in a plastic bag inside an ice bath. The amputated part should not touch ice. Successful reimplantation of digits severed distal to the distal interphalangeal joint (DIPJ)

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