Wrist And Forearm Injuries - pediagenosis
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Friday, November 8, 2019

Wrist And Forearm Injuries

Wrist And Forearm Injuries
Injuries to the wrist and forearm are common, often resulting from a fall onto an outstretched hand (FOOSH). It can be difficult to distinguish subtle fractures from soft tissue injury on clinical history and examination alone, so X-ray is usually necessary.

Fractures of normal bones imply high-energy injuries, whereas a fracture occurring as a result of a low-energy injury implies poor bone quality – a ‘fragility fracture’, and the need to screen for osteoporosis.
In any injury affecting the upper limb, dominance (handedness) and occupation and hobbies must be recorded. If the injury is the result of a fall, consider further investigations (Chapter 30).

Wrist And Forearm Injuries

Examination: look, feel, move
Compare with opposite side, and look for swelling/bruising. A full range of elbow flexion, pronation and supination makes significant injury unlikely. The radial, median and ulnar nerve function in the hand should be checked (Chapter 14).

Management of fractures: principles
Pain should be controlled by splintage and analgesic drugs before imaging. Elevation of the arm in a sling reduces soft tissue swelling and pain. If there is any evidence of neurovascular deficit or tenting of the skin by fractures, urgent reduction will be necessary.
If there is a skin wound over a fracture, this makes it an open fracture. Antibiotics ± anti-tetanus treatment must be given immediately. The wound should be covered with a saline-soaked dressing, and the patient should go to theatre for debridement as soon as possible.
Plaster of Paris casts are used to hold the fracture in position while it heals. Rings should be removed before plaster is applied, as the digits will swell.
Compartment syndrome results from swelling of muscle within fascia compartments, e.g. of the forearm, leg or foot. If untreated, the muscle dies, resulting in untreatable ischaemic contracture. Patients should be warned about the symptoms: numbness, pain and cold digits. If a patient has pain on passive stretching of a muscle, compartment syndrome is likely; a palpable pulse does not exclude compartment syndrome. If elevation does not solve the problem, the plaster must be released, and a surgeon must review.

Common diagnoses
Colles’ fracture
This is a fracture of the distal radius occurring in osteoporotic bone resulting from low-energy impact, e.g. FOOSH. The fracture may be impacted and the tip of the ulna is often avulsed. Dorsal angula- tion gives the wrist a ‘dinner fork’ appearance.
The fracture should be reduced in the Emergency Department using haematoma block and nitrous oxide, or intravenous regional anaesthesia (Chapter 5). Good wrist function depends on restoration of the length of the radius, and avoidance of steps in the articular surface. On the lateral X-ray view, the articular surface of the radius is normally 10° angulated towards the palm. This is often difficult to achieve by reduction, but a neutral (0°) position is satisfactory.

High-energy distal radius fracture
This injury occurs in normal bones as a result of high-energy impact, e.g. falling off a bicycle. In comparison to a Colles’ fracture, there is more likely to be comminution (multiple bone fragments), more soft tissue damage and more pain: intravenous opiates are necessary.
To achieve good function, these fractures need excellent (‘anatomical’) reduction and may ultimately require operative fixation with plates or wires. A good reduction in the Emergency
Department using intravenous regional analgesia or procedural sedation (Chapter 6) minimises soft tissue swelling and may avoid the need for further intervention.

Smith’s fracture
A Smith’s fracture is sometimes called a reverse Colles’ fracture: it is a distal radius fracture, but instead of dorsal angulation, there is volar (palmar) angulation. However, Smith’s fractures often occur in normal bone, when they are high-energy injuries. The structures on the volar (palmar) side of the wrist are at risk of injury, particularly the median nerve.
A Smith’s fracture is inherently unstable, and almost always needs open reduction and internal fixation (ORIF) (e.g. with a plate and screws), although a good reduction in the Emergency Department is usually the first step in the management.

Diagnoses not to miss
Scaphoid fractures
The difficulty in diagnosis and the consequences of failure to diagnose make this fracture a frequent source of litigation. The history is usually FOOSH, and clinical signs are pain:
   In the ‘anatomical snuffbox’ between extensor pollicis longus (EPL) and abductor pollicis longus (APL).
      On axial thumb compression.
      On pressing over the scaphoid tubercle.
A patient with clinical signs of scaphoid injury requires a ‘scaphoid view’ X-ray. If this demonstrates a fracture, the joint should be immobilised as shown opposite.
Even if the X-ray does not show a fracture, the patient should still be immobilised in a splint or plaster cast, and sent home to have a definitive investigation, e.g. repeat X-ray, in 1 week, or CT or MR scan, to prove or refute the diagnosis of scaphoid fracture.
The reason for this approach is that 20% of patients have fractures of the scaphoid that are not visible on plain X-ray until at least 1 week after injury. If the scaphoid fracture is missed, avascular necrosis and non-union can result in early osteoarthritis and disabling stiffness of the wrist.
If you perform an X-ray of the scaphoid, it is illogical and therefore medicolegally indefensible not to follow up with a definitive investigation.

Fractures of shaft of radius and ulna
The X-ray must include the joint above and below to ensure that there is no dislocation. These fractures need ORIF.
       Nightstick fracture: a mid-shaft transverse fracture of the ulna, usually a ‘defence injury’ when the forearm is raised to protect the head (‘nightstick’ is the US term for a police truncheon). Consider possible causes, e.g. domestic violence.
      Monteggia fracture: fracture of proximal third of ulna and dislocation of the head of the radius at the elbow.
    Galeazzi fracture: fracture of distal third of radius with associated dislocation of distal radio-ulnar joint; rare.

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