The wrist is the most commonly injured part of the arm and three-quarters of wrist injuries are wrist fractures of the ends of the radius and ulna. The small wrist bones are much less commonly injured.
Wrist fractures can be simply classified into extension fractures of the radius, flexion fractures of the radius and fractures of the carpal or wrist bones.
Severity of a broken wrist is judged by how far the fragments have been displaced from their normal position and by how many fragments there are. The greater number of fragments and the more the bones are out of place the worse the injury is.
Wrist Fracture Classification
Fractures are initially classified as being stable or unstable. Undisplaced breaks, where the bones are still aligned, are often stable and will maintain their position during immobilisation. Displaced breaks, where the bone fragments have moved out of their normal positions, may be stable once they have been set or “reduced” back to normal alignment.
Unstable fractures won’t keep their alignment even after reduction of the fragments and placement in a cast. The bone parts shift out of position and if they heal in that position, the healed wrist may look crooked and have limited function or pain. These fractures may need surgical fixation to maintain their position while the bone heals.
Fractures can be more or less severe in various ways. Fractures that run into the smooth cartilage joint surfaces or that break into many pieces (a comminuted fracture) are often unstable. Surgery is usually required to stabilise these fractures. All these fractures are called “simple fractures” which refers to the fact that the skin is intact and not that they aren’t complicated.
Compound or open fractures can occur when a bone fragment breaks through the skin and this can allow bacteria into the wound and cause infection. Any break of the skin over or near a fracture should be treated as a compound fracture even if the bone was not the agent that caused the wound.
Greenstick fractures occur in children. Their bones are less brittle and more plastic than adults, so a fracture results in the bone bending or crumpling rather than breaking.
Distal Radius Fracture - Extension Type
A fall on an outstretched hand, impacting on the palm with the palm facing downwards is the commonest method of injury. In adults this typically results in a distal radius fracture within an inch of the wrist joint. The end fragments of bone are pushed up and backwards. The ulna may also be fractured. A Colles Fracture is the commonest type.
Distal Radius Fracture – Flexion Type
Much less common than the Colles Fracture, the reverse Colles or Smith Fracture is due to a fall on the hand with the palm upwards. The hand is then forced into full flexion (bend) by the weight of the body. The bone fragments are pushed downwards and towards the palm.
Carpal Bone Fractures
There are a large number of injuries, including fractures, dislocations and sprains, which can occur to the carpal bones.
- Scaphoid fracture. The scaphoid is the most frequently injured of the wrist bones at around 60-70% of all such injuries. This fracture is also easy to miss, as it doesn’t show up on x-ray in about 10-15% of cases.
- Lunate fracture. The lunate is in the centre of the wrist bones and moves against the radius. A fall on the hand with the wrist right back or a fall on the heel of the hand can be the cause.
- Triquetrum fracture. This bone is quite commonly injured forced hyperextension (bending right back) of the wrist and movement inwards towards the ulnar direction. The local ligaments can be ruptured and a chip fracture of the bone caused.
- Capitate fracture. The capitate is the largest wrist bone. A direct blow or crushing force on the back of the hand or a fall on the outstretched hand can result in this injury.
- Hamate fracture. The hook of the hamate, a protruding part of the bone towards the palm side, is most commonly injured. Typical causes are hitting an object while holding a racquet, bat or club. Gripping causes pain in this injury.
- Trapezium fracture. Not common and occurs when the thumb is forced against the nearby wrist bone when it’s close to the palm.
- Trapezoid fracture. This is a rare fracture and can occur when a force is applied along the line of the second metacarpal, the bone that joins further up the hand with the index finger.
- Pisiform fracture. The pisiform is a small bone, which sits inside the tendon of a forearm muscle. This kind of bone is known as a sesamoid bone. A fall on the little finger side of the palm may cause a pisiform fracture.
- Dislocations. A large number of injury patterns can occur and often involve the lunate bone. Difficult to diagnose, it is important to get an expert opinion and the right management for future function of the wrist.
Treatment of Wrist Fracture
As with all suspected fractures, medical attention should be sought as soon as possible. X-ray will help confirm the nature of the injury and manipulation, plaster cast, surgery or a combination of treatments may be required.
After the injury has healed sufficiently, the cast or brace will be removed. Physiotherapy may be useful to regain any limited range of motion and to restore strength and normal function after a broken wrist.
- Distal Radius Fractures – Broken Wrist. OrthoInfo. http://orthoinfo.aaos.org/topic.cfm?topic=a00412
- Wrist Fractures and Dislocations. Medscape. http://emedicine.medscape.com/article/1285825-overview#a5