Frattura del polso scafoide

What is a scaphoid fracture?

A scaphoid fracture occurs when you break your scaphoid bone. It is the type of fracture that most commonly happens after a fall on to your outstretched hand. That is, when your palm is flat and stretched out and your wrist is bent backwards as you fall to the ground. Instinctively, you will usually put your hands out in this position for protection if you fall forwards.

Sometimes a direct blow to the palm of your hand can cause a scaphoid fracture. Rarely, repeated 'stress' on the scaphoid bone can lead to a fracture. This can occur, for example, in gymnasts and shot putters.

Commonly you will fracture only your scaphoid bone but sometimes other bones around the wrist area may be broken at the same time.

Scaphoid fractures may be non-displaced (the fragments of the broken bone haven't moved out of position) or displaced (there is some movement of the bone fragments).

The scaphoid bone is the most commonly broken (fractured) carpal bone. This is because of its size and position in the two rows of carpal bones in the wrist.

Usually, most people who break (fracture) a scaphoid bone will remember a specific injury or fall. Symptoms of a scaphoid fracture include:

• Pain around the wrist area after the injury.

• Bruising or swelling around the wrist on the affected side.

In some people, symptoms may be milder. Quite commonly, people with a scaphoid fracture just assume that they have a wrist sprain and don't seek medical attention for some time afterwards. The fracture may only be diagnosed when they see a doctor some weeks later because of pain that is not settling or reduced movement around their wrist.

A doctor will usually suspect a scaphoid break (fracture) by the mechanism of the injury that has happened - for example, a fall on to an outstretched hand. Also, when they examine your wrist and hand, there is a specific point where you are likely to be tender if you have a scaphoid fracture. This is known as the anatomic snuffbox. It is a depression in your skin on the back of your hand near to the base of your thumb. Movement of your wrist in certain directions may also be painful if you have fractured your scaphoid.

It can sometimes be quite difficult to diagnose a scaphoid fracture. However, it is important to recognise and treat a scaphoid fracture as soon as possible because the complication of non-union (see below) is more likely if treatment is delayed.

Wrist X-ray

Standard X-rays may not pick up all scaphoid fractures. This is because the scaphoid bone can 'hide' behind the other carpal bones on an X-ray. Special scaphoid view X-rays taken with your hand and wrist in a certain position may help to show up a scaphoid fracture. However, about 2 in every 10 scaphoid fractures may not be seen on X-ray at first.

In some cases, a scaphoid fracture will not show up on an X-ray until around 10-14 days after the initial injury. At this time, the healing process will have started in the bone, which will help the fracture site to show up. So, if a scaphoid fracture is suspected but not confirmed on an initial X-ray, you will usually be treated as if you have a scaphoid fracture (see below). A repeat X-ray may be suggested after 10-14 days.

Ultrasound, CT or MRI scan

Sometimes, at this time, it is still not clear whether you have had a scaphoid fracture. If this is the case, a tomografia computerizzata oppure Risonanza magnetica may be suggested to look for the fracture. A radionuclide bone scan is occasionally used as an alternative but this is used less often, as MRI and CT scans are more widely available and expose you to less radiation.

There is currently some debate as to whether there is benefit of doing further investigations such as an ultrasound, CT or MRI scan earlier if a scaphoid fracture is suspected but has not shown up on the initial X-ray. You will usually be followed up by an orthopaedic surgeon in the outpatient clinic if a scaphoid fracture is diagnosed or suspected. They will be able to advise whether and when further investigations are needed.

If a non-displaced scaphoid break (fracture) is confirmed on X-ray or is suspected, it is usually treated by putting your arm in a cast (commonly referred to as a plaster cast but actually made of fibreglass or another similar synthetic material) up to your elbow. This is not the same as wearing a splint - a splint can be removed and put back on, whereas a cast stays on for the whole time. The cast is usually worn for 6-12 weeks until the scaphoid bone heals. In some cases, it may be needed for longer.

If a scaphoid fracture is displaced, surgery may be advised. A small screw or a special pin is inserted into the scaphoid bone to hold the bone fragments together in the correct position. This can often be done via a small cut in your skin.

Sometimes surgery may be an option for some people even if a scaphoid fracture is non-displaced. The idea is that it avoids you having to wear a cast for a long period of time. In some cases it may remove the need for wearing a cast altogether.

Some also argue that it allows normal movement of your wrist to return more quickly than if you had just been treated with a cast. This means that you can return to your usual activities more quickly. For example, if you are an athlete, a musician, or if there is another reason why you have significant pressure to return to high-level activity quickly, this treatment option may be a consideration. However, this does mean going through a surgical procedure that does carry some small risks.

What happens if a scaphoid fracture is left untreated?

If the fracture is left untreated, there may be non-union and/or avascular necrosis - these are described in more detail below. Longer term consequences can include chronic pain and a loss of function.

A scaphoid break (fracture) will usually heal well if it is recognised and treated early. However, occasionally, complications can occur after a scaphoid fracture. These can include the following:

Delayed union or non-union

Delayed union occurs when the scaphoid bone has not healed completely after four months of being treated in a cast. Non-union occurs when the scaphoid fracture has not healed at all. In non-union, the bony fragments are still completely separated.

Delayed and non-union may be more likely if treatment of a scaphoid fracture is delayed for some reason. So, this is the main reason why a scaphoid fracture needs to be recognised and treated promptly. However, the exact position of the fracture in the scaphoid bone, whether the fracture is displaced of not, and whether or not there is avascular necrosis (see below), can also affect the healing of a scaphoid fracture.

If delayed or non-union occurs, various treatments may be suggested, including wearing a cast for a longer period or surgery to help join the bone fragments together. Surgery may involve a bone graft to help with fracture healing. This is a procedure where bone tissue is taken from another area of bone in the wrist and inserted into the fracture site.

Malunione

This occurs when the fragments of the scaphoid bone heal in an incorrect position - for example, at a slight angle. If this happens, it may affect the movement of the wrist and lead to pain and problems gripping and holding objects.

Malunion may be seen on an radiografia or scans of the scaphoid bone. Surgery is usually needed to correct this complication. The scaphoid bone is re-broken, aligned correctly and a bone graft used to correct the deformity and encourage healing.

Necrosi avascolare

Most commonly, a fracture occurs at the narrowest part of the scaphoid (known as the waist). This is where the blood supply enters the scaphoid bone. So, there is a risk that if you have a fracture in this area, it can sometimes stop the blood supply to part of the scaphoid bone, leaving part of the bone without a blood supply. This means that the scaphoid will not be able to heal properly and part of the scaphoid bone 'dies', collapses and breaks up. ('Avascular' refers to having no blood supply and 'necrosis' means death.)

If it occurs, avascular necrosis can be seen on an X-ray of the scaphoid bone some months after the initial injury. However, avascular necrosis does not occur with all fractures around the waist of the scaphoid.

Osteoartrite

Osteoarthritis can develop some time after a scaphoid fracture in some people. It is more likely if there have been complications of non-union, malunion or avascular necrosis.

Diagram showing scaphoid position

There are two bones in the part of the arm between the elbow and the wrist (the forearm). These bones are called the radius and the ulna.

The radius is on the thumb side of the wrist and the ulna is on the little finger side.

In the hand, there are eight small bones known as the carpal bones. They are arranged in two rows, one on top of the other.

The proximal row is the row that is closest to the arm. In the proximal row are the scaphoid, lunate, triquetrum and pisiform bones. The distal row is the row below this nearest to the hand. In the distal row are the hamate, capitate, trapezoid and trapezium bones.

The scaphoid bone is one of the largest of the carpal bones and is on the thumb side of the wrist. It looks a bit like a cashew nut and is roughly the same size. It links the two rows of carpal bones together and actually helps to stabilise them. The scaphoid bone and the lunate bone connect with the radius at the wrist joint.