A fracture of this carpal bone is most common in adolescents and young adults. The scaphoid bone is located on the radial side (thumb) of the wrist in an area.
Scaphoid fractures are often mistaken for sprained wrists
The scaphoid is unique in that it spans the two rows of bones that make up your wrist. Due to its position, it is the most commonly broken bone in the wrist and because symptoms can be minimal, scaphoid fractures are frequently mistaken as sprained wrists. There is often only a little swelling which usually goes away in a few days and a variable amount of pain may be present.
Unlike the forearm, hand and finger bones, fractures of the scaphoid almost never show any obvious deformity of the wrist. These factors can make it common for the diagnosis to be delayed for weeks, months or occasionally even years after the initial injury because this injury can be overlooked or thought to be a common wrist sprain. Scaphoid fractures will require casting or surgery.
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To diagnose a scaphoid fracture we begin by examining your wrist and taking specific x-rays. Sometimes scaphoid fractures do not show up on initial x-rays unless specifically dedicated views are taken. Any patient who has fallen on an outstretched hand and has swelling or tenderness on the thumb side of the wrist should be assumed to have a scaphoid fracture, until tests prove otherwise.
X-rays taken immediately after the injury may not show a fracture. If there remains a high degree of likelihood, the wrist should be immobilised in a splint and further imaging should be done by repeating dedicated x-rays of the scaphoid at 10-14 days after the injury or performing an MRI scan.
Repeating plain x-rays after 10-14 days will often reveal a fracture that was not initially apparent, as the fracture gap widens initially as part of the normal healing process. An MRI scan is extremely sensitive and will identify a fracture, even if it still is not visible on x-ray at two weeks. An MRI however also has the advantage of identifying other injuries, for example, significant ligament injuries that may present in a similar fashion.
As part of treatment, Computerised Tomography (CT) scans also have a role. These can be used to assess the success of the union but also can assess the 3D anatomy of the scaphoid bone, particularly when the bone has failed to unite. The shape of the bone ultimately is also important in allowing the complex mechanics of the wrist to function well.
Symptoms that indicate a scaphoid fracture
A scaphoid fracture causes tenderness directly over the bone and the pain may increase when you move your thumb or grip things. Your initial pain may decrease over days or weeks and because there is no significant bruising or swelling they are often mistaken for a sprained wrist.
Symptoms of a non-union of the scaphoid bone may be more subtle i.e. you may have pain when you use your wrist but this can be minimal. Still, the most common symptom of a non-union is a gradual increase in pain and over several years the non-union can lead to degenerative arthritis in the wrist joint.
Causes: how does a scaphoid fracture develop?
A scaphoid fracture most commonly results from a fall on an outstretched hand. When a scaphoid fracture is recognised on the first X-ray, treatment begins immediately. Since patients often assume that the injury is just a sprain it is often the case that they wait for it to heal on its own. In some instances, the wrist gets better however, in many cases the bone fails to heal. This can result in the scaphoid fracture developing into what surgeons call a non-union.
A non-union can occur in two ways i.e. a simple non-union, the two pieces of bone fail to heal together or the second type which is much more serious when the lower half of the fractured bone loses its blood supply and dies e.g. avascular necrosis. Only one small artery enters the bone, at the end that is closest to the thumb therefore, if the fracture tears the artery, the blood supply is lost. If a scaphoid fracture is left untreated, the bone is at risk of avascular necrosis.