What is the scaphoid?
The scaphoid is one of the small bones in the wrist. These bones are called the carpal bones. It is the most commonly broken carpal bone (80 % of carpal injuries involve the scaphoid). The scaphoid is located on the thumb side of the wrist. It lies near the base of the thumb, just above the radius bone of the forearm.
The scaphoid bone can easily be identified by holding the thumb in a "hitch-hiker’s" position and feeling with the opposite index finger in the hollow made by the thumb tendons. Pain or tenderness in this area can be a sign that the scaphoid is broken.
How does a scaphoid fractures occur?
A scaphoid fracture is usually caused by a fall on an outstretched hand, with the weight landing on the palm. Such falls can result in large forces being transmitted to the wrist. Such forces can fracture any of the bones in the wrist, but the scaphoid fracture seems to be particularly vulnerable.
Who does it affect?
Though scaphoid fractures can occur at any age, they are more common in young men aged 20 and 30 years.
What are the symptoms?
Scaphoid fractures usually cause pain and swelling at the base of the thumb. The pain may be severe particularly when you move your thumb or wrist, or when you try to grip something. It may be difficult to pull your wrist back into extension due to pain.
Usually the wrist does not look deformed, so it might not be obvious that there is a broken bone. In some cases, the pain is not severe, and the injury may be mistakenly labeled as a “sprain”.
How is it diagnosed?
The diagnosis is made from the history of injury and the specific features found on clinical examination. X Rays confirm the diagnosis in most cases. Sometimes, however, a broken scaphoid does not show up on an x-ray straight away. In this case, the doctor may apply a cast or splint for a week or two. Then a new x-ray will be taken to see if the fracture has become visible. If no fracture is seen and there is still clinical suspicion, then a magnetic resonance imaging (MRI) scan or Computerized Tomography (CT ) scan may be requested. These are very sensitive and can sometimes shows a fracture of the scaphoid that is invisible on an x-ray.
Can there be problems with healing?
Yes. Fractures of the scaphoid bone are notorious for slow healing or even failing to heal. This is because of the peculiar features of the bone and its blood supply. Most of the scaphoid bone is covered by smooth cartilage where it makes a joint with adjoining carpal bones. Blood vessels cannot enter the scaphoid through these cartilage-covered areas. As a result, the blood supply enters the scaphoid bone from its far end (called the distal end) and travels through the bone to its near end (proximal end). Therefore the distal end of the bone has a better blood supply than the proximal end. Hence the closer a fracture to the proximal or near end, the worse is the healing potential. Fractures can occur anywhere in the scaphoid, but the majority occur through the centre of the scaphoid (waist). These have got a good chance of healing with appropriate treatment (approximately 85%). However, fractures towards the near end (the so-called proximal pole fractures) have a much higher risk of the fracture not healing due to the poorer blood supply to this area of bone. Other risk factors for the fracture not healing are: significant displacement of the fracture fragments, smoking and delay in seeking medical advice.
How are scaphoid fractures treated?
Treatment of scaphoid fractures depends on the location of the break in the bone and whether the fragments have displaced or not.
Fractures in the distal pole (far end or thumb end of the bone)
Scaphoid fractures that are closer to the far end of the bone usually heal in a matter of weeks with proper protection as this part of the scaphoid bone has a good supply of blood, which is necessary for healing.
A plaster cast or fiberglass cast is applied for at least 6 weeks. The cast will usually be below the elbow. It may or may not include the thumb.
The time it takes for the fracture to heal varies from person to person. Your doctor will monitor the healing by taking periodic x-rays or other imaging studies, such as a computed tomography (CT) scan, if there is any doubt whether the bone has healed. The fracture may take 12 weeks or longer to heal.
Fractures in the proximal pole (near end or forearm end of the bone)
If the scaphoid is broken closer to the forearm (proximal pole), healing is more difficult.
These areas of the scaphoid do not have a very good blood supply.
These fractures usually require operative treatment.
Fractures in the waist (middle) of the scaphoid
These fractures are usually treated non-operatively if the fracture fragments are not displaced. If displaced however, then operative treatment is recommended.
What does operative treatment involve?
Surgery is performed under general anaesthetic or regional anaesthesia (in which the arm is numbed) as a day case. The surgery can involve a 3-4 centimetre open incision or sometimes it can be done through a tiny 3-4 millimetre incision (“percutaneous fixation”).
Both types of surgery involve the placement of a bone screw, under x-ray control, across the fracture site in the scaphoid. The screw is buried deep inside the bone and remains there permanently. After this type of surgery the patient is usually mobilised quickly, and plain radiographs or CT scans are performed to ensure the bone has united.
The mini incision technique has the advantage of less surgical dissection and, therefore, less trauma to surrounding structures. As a result post-operative rehabilitation is usually quicker with the percutaneous technique, but the overall healing rate between the two techniques is about the same.
What about after the operation?
The wrist is usually mobilised within the first two weeks. Once good range of movement has been achieved, then strengthening exercises are started. The skin sutures used are absorbable, therefore they do not need to be removed.
When can I return to normal activities and work?
Patients who are treated operatively, particularly with the percutaneous mini-incision technique, can return to driving and many activities of daily living within a couple of weeks. After fixation, scaphoid fractures usually take about 6-8 weeks to heal. It is very important to maintain full finger motion throughout this recovery period. You will be provided with an exercise program, and may require hand therapy to help you regain motion and strength in your wrist. Even with therapy, some people do not recover the same motion and strength in their wrists that they had prior to their injury.
Patients who are treated non-operatively, in a plaster cast or fiberglass cast should not attempt to drive mainly for insurance reasons.
Return to work depends on your profession. Return to heavy manual labour is delayed until after bone healing. Light desk duties can be started within a few days.
What are the possible complications after a scaphoid fracture?Non-union
Failure of the bone to heal or non-union is the main complication of scaphoid fractures. The risk is higher for fractures that are displaced or involve the near end of the bone. The overall non-union rate for scaphoid fractures is about 12-15%.
When the scaphoid bone breaks, especially when the fragments have moved apart (displaced), the blood supply to one of the fragments may get disrupted so that it does not get enough nutrients and the cells in that fragment die. This is called avascular necrosis. A bone graft with its own blood supply (vascularized graft) may be required to treat this condition.
If a non-union or avascular necrosis is left untreated then arthritis in the wrist tends to develop over a number of years.
Symptoms of arthritis in the wrist include:
- Wrist pain
- Decreased range of motion
- Pain and weakness during activities such as lifting or gripping
Treatment is symptomatic initially. This may include taking anti-inflammatory tablets and wearing a wrist splint. Sometimes, a steroid injection into the wrist may be required. If this does not work, surgery may be recommended.
Treatment in a cast has few complications, apart from non-union. Occasionally stiffness can occur in the digits if the fingers are not moved early. Hence it is very important to perform finger exercises regularly.
Surgery for scaphoid fractures is low risk. The possible complications include: infection, damage to blood vessels or nerves, scar tenderness or hypersensitivity, failure of fixation, and finger or wrist stiffness.