Download Size [623kb]
Fracture and nonunion of the scaphoid
What is it?
The scaphoid is one of the eight carpal bones in the wrist. The wrist itself is a complex joint that has the carpal bones arranged in two rows. These bones articulate with one another and the two-forearm bones - the radius on the thumb side and the ulna on the little finger side. The scaphoid is on the thumb side of the wrist and is an important bone as it transmits large forces across the joint.
What is its cause the fracture and subsequent non-union?
The scaphoid is the most commonly fractured carpal bone in the young, perhaps after a fall on an outstretched hand. This is because it lies across the two rows.
When a bone fails to heal it is called a ‘non-union’. Scaphoid fractures frequently go into a non-union. This is because the scaphoid also has a unique anatomy. First of all it has an unusual blood supply. Blood supply to any bone is very important to its healing as the blood will carry oxygen and nutrients to the site of the fracture. The scaphoid has poor blood supply as it is entirely covered by cartilage (gristle) and has with no soft tissue attachments through which blood vessels can enter the bone. It is supplied by a blood vessel that enters the bone from its far end and then heads backwards to its near end. For descriptive purposes the scaphoid is divided into three equal parts – distal (far end), middle (waist of the bone) and proximal (near end). Because of the poor blood supply, the more the fracture is to the near end, the more likely it will fail to unite. Sometimes, the blood supply to one of the fragments is so poor, that the cells in that fragment die. This is called ‘avascular necrosis’.
The other factor that contributes to non-union is when the scaphoid lies across the two rows and so its ends are attached to different rows. The mechanical forces within the wrist will thus tend to displace the two halves of the broken bone, even while it is held in plaster.
What are the symptoms and how is the condition diagnosed?
A fracture of the scaphoid is suspected if there is pain in the wrist after a fall. The area in the hollow between the thumb base and the wrist (anatomical snuffbox) will be tender.
The diagnosis can only be confirmed by an x-ray, though the fracture may not be seen on the initial x-rays. If there is a clinical suspicion of a scaphoid fracture, the wrist is treated as if a fracture has been sustained.
Patients with a scaphoid non-union will complain of persisting wrist pain with reduced movement. It is not unusual to see such patients who sustained a wrist injury months earlier, and thought they had just sprained the wrist. They will be tender in the anatomical snuffbox. The diagnosis will be confirmed by an x-ray.
Will further tests or investigations be needed?
In addition to the initial x-ray the specialist may advise further investigations (usually CT or MR scan) to confirm the fracture, and assess the fracture level and displacement.
What is the treatment for acute fractures and non-union?
- Treatment of acute fractures is dependent on many factors. The location of the fracture in the bone (distal, middle or proximal); if the fracture fragments have moved apart (displacement); fractures fragments (comminution); and functional demands of the patient.
- Conservative (non-surgical) treatment:
This is the conventional treatment of scaphoid fractures and is practiced in fractures that are not displaced and located in the distal or middle (waist) part of the bone. Treatment consists of immobilizing the wrist in a plaster cast for 6-12 weeks. Following such treatment 90% of these fracture types will unite. If fractures that are displaced and comminuted are treated too conservatively, the fractures may not unite.
- Surgical treatment by percutaneous fixation with a screw:
This is an alternative form of treatment for fractures that are not displaced and located in any part of the bone. The procedure involves one stab incision, then a specially designed screw (of a differential pitch that can be buried in the bone) is used to stabilise the fracture. The procedure is carried out under x-ray control. The advantage of this procedure is that splintage is needed for a shorter time and the healing time is quicker. Thus there is potential to return sooner to normality.
- Surgical treatment of acute fractures by open reduction and fixation with a screw: This type of surgery is practiced for fractures that are significantly displaced and comminuted. An open operation with an incision of about 5 cm is needed. The fracture is reduced and a similar screw described above is used to stabilize the fracture.
- Surgical treatment of a scaphoid non-union by open reduction, bone grafting and fixation with a screw:
During this surgery the site of the scaphoid non-union is accessed by a 5-7 cm incision. The ends of the scaphoid bone are freshened. A piece of bone (graft) from the iliac crest (part of the hip where the trouser belt rests on) is taken and inserted in the non-union. The bone graft produces new cells that will help heal the non-union, but also correct the deformity caused by the non-union. The scaphoid bone fragments and the bone graft are then stabilised with a differential pitch screw (described above) which is used to stabilize the fracture (see picture below).
- Surgical treatment of a scaphoid non-union by open reduction, vascularised bone grafting and fixation with a screw:
During this surgery, the bone graft is taken from the end of the radius bone with its blood vessel. As the blood supply to the bone graft is preserved, it has the advantage of setting up a new blood supply to the scaphoid bone. The scaphoid bone fragments and the bone graft are then stabilised with a similar differential pitch screw (described above) which is used to stabilize the fracture.
What happens if it is not treated?
If the scaphoid fracture is not appropriately treated it will not heal. Non-union of the bone will change the biomechanics of the wrist due to shortening (carpal collapse), which will inevitably lead to osteoarthritis (SNAC wrist).
What is the success of surgical treatment?
It is very difficult to predict union rates for scaphoid fractures but generally union rates after internal fixation for acute fractures is about 80%. Similarly there is a reasonable chance of achieving bony union after surgery for scaphoid non-unions that have occurred in the middle (waist) level. Success rate for non-unions at the proximal scaphoid are less favourable.
Smokers have a significantly poorer union rate as the toxins affect blood vessels.
What are the complications of surgical treatment?
- Infection of the wound is possible and can usually be successfully treated with antibiotics.
- Wrist stiffness
- Unsightly scar and scar tenderness.
- The operation may fail to achieve union.
- The operation may fail to improve symptoms.
- It is not a technically easy operation. The screw could be inserted incorrectly or it may fail to get a good purchase in the bone.
- Severe complex regional pain syndrome (CRPS) is a rare but serious complication after hand surgery. Unfortunately it is not possible to predict this problem but it needs to be monitored and treated (usually with just physiotherapy) if it develops.
- Any surgical intervention has the risk of developing complications that are unpredicted. These complications may have the potential to leave the patient worse than before surgery.
Is there anything I can do to improve the outcome?
- Keep the wounds dry and clean until they have healed.
- Be compliant with usage of the splint.
- Carry out any prescribed exercises regularly.
- It is advised against wearing rings on the operated hand for 4-6 weeks after surgery.
When can I do various activities?
- Return to work depends on many factors including the nature of the job and hand dominance.
- After percutaneous fixation of a scaphoid fracture, you should be able to return to a desk job within 1 week of the operation and perform reasonable tasks with the limb in 2 weeks. Manual work should be avoided for 6 - 8 weeks.
- Driving should be possible within a few days of the operation. Before driving, do check that you can manage all controls and start with short journeys.
- Return to work following open surgery (or open surgery for scaphoid non-union), will vary individually.