Scaphoid fractures

What is the scaphoid bone?

The scaphoid bone is the largest of eight small bone found in the wrist. Its name is derived from Greek, which means boat shaped, but actually it resembles a monkey nut. The scaphoid bone is important in wrist function and it forms a link between two rows of bones in the wrist. The scaphoid bone is mostly covered by articular cartilage and it has a poor blood supply, which means that fractures are prone to not healing. The scaphoid bone is the most commonly injured bone in the wrist.

Figure 1: scaphoid bone seen on an x-ray (circled). This links two rows of bones in the wrist. The 3D image shows the 'peanut' shape

Presentation of a scaphoid fracture:

The scaphoid bone usually fractures (breaks) after a fall onto an outstretched hand. The symptoms are often minor and often people think that they have only sprained their wrist and do not seek medical attention. Typical symptoms experienced are:

• pain. This is typically felt over the back of the wrist towards the side of the thumb
• swelling. This is often minor.
• wrist stiffness. This is usually due to the wrist pain.

Diagnosis:

X-rays are helpful in diagnosing a scaphoid fracture. Sometimes a fracture will not be seen on the first x-rays and if a scaphoid fracture is suspected, it is usual to immobilise the wrist and review with a further x-ray 10-14 days later. In some cases it there remains suspicion that the scaphoid has fractured despite normal x-rays. In these cases further imaging can be helpful and this usually involves either a bone scan, CT scan or MRI scan.

Figure 2: Scaphoid fracture - grey line crossing the scaphoid bone

What else could it be?

Some people who are thought to have a scaphoid fracture immediately after their injury, are not found to have a fracture after imaging. In these patients the following my have caused their symptoms:

• a wrist ligament sprain. This is common
• a wrist ligament tear. Less common and includes the scapholunate ligament
• tendon disorders such as DeQuervain's disease.
• thumb arthritis

What are the problems with scaphoid fractures?

The problems with acute scaphoid fractures include;

1. they may be difficult to diagnose
2. they are prone to not healing. This is more likely without treatment but it does occur even with treatment
3. un-united fractures (a scaphoid non-union) may cause continued wrist pain and risk future wrist arthritis

Non-surgical Treatment:

Most scaphoid fractures can be treated non-surgically by immobilising the wrist in a cast. The type of cast used and duration of immobilisation varies depending on the site of the scaphoid fracture. In the UK most surgeons immobilise the wrist in a below elbow cast for between 6 - 12 weeks. Fractures that involve the proximal part of the bone (the part nearest the wrist joint) take longer to heal and they are more likely not to heal even with prolonged immobilisation in a cast.

Surgical Treatment:

Surgery is necessary to treat some scaphoid fractures. Indications for surgery include those fractures which are

• displaced
• unstable
• have associated injuries to the surrounding bones or ligaments
• involve the proximal pole of the scaphoid bone

These fractures have a higher chance of not healing with non-operative treatment. Surgery involves reducing the displaced bone fragments and the fracture is fixed usually with a screw. There are several different surgical techniques and types of screws used, and your surgeon will discuss these with you.

In some cases it is reasonable to operate on undisplaced fractures. A small screw can be inserted through a small stab incision made in the skin. This is called percutaneous fixation and it offers some benefits over non-surgical treatment. The surgery does not necessarily increase the chance of the fracture healing, but it enables earlier removal of the cast and mobilisation.

Figure 3: Scaphoid fracture treated with a headless screw which is buried in the bone.

There are several recognised postoperative complications:

• wound infection (approximately 1%)
• a small visible scar which may be tender for a period
• stiffness of the fingers or wrist (uncommon)
• failure of the fracture to heal (scaphoid non-union) despite successful surgical treatment. This is thought to be as a consequence of the poor blood supply to the scaphoid bone.