What is the scaphoid bone?
Background
The scaphoid bone is one of the carpal bones in the hand. It is in the thumb area and is the first bone of the first row of the carpus. The scaphoid is one of the bones that is injured the most.
What is its function?
The carpal bones are a unit that provides a bony structure to the hand. Along with the lunate, it articulates with the radius and ulna to form the main bones involved in wrist movement. The scaphoid is a link between the two carpal bone rows.
Scaphoid bone injuries
A hand scaphoid fracture is one of the most common injuries due to its proximity to the two rows of carpal bones. Fractures tend to happen due to falling on an extended hand or due to a bad stretch. Pain and wrist swelling are the most common symptoms. Any pressure on the bone can cause intense pain. Sometimes a scaphoid fracture only causes mild discomfort and pain in the area. A scaphoid fracture can be difficult to diagnose as it is often confused with a wrist sprain.
Another condition that affects the scaphoid is scapholunate instability, which occurs when the scapholunate ligament (that connects the scaphoid with the lunate bone) and other surrounding ligaments rupture. When this happens, the gap between the scaphoid and the lunate bones increases.
Preiser disease is a rare condition that is also known as idiopathic avascular necrosis of the scaphoid. It causes bone ischemia and necrosis without a previous fracture.
What are the treatments?
Treatment for a scaphoid bone fracture involves putting a cast on the hand to immobilise the wrist, although in some cases, surgery may be resorted to. Treatment for scapholunate instability can be treated by following the following guidelines:
• Apply ice regularly.
• Immobilise the area.
• Raise the arm to prevent oedema.
• Contrast baths (hot and cold water).
• Active and passive wrist movements.
• Proprioception.
• Strengthen muscle.
• Using Kinesio tape bandage.
If carpal instability is due to an architectural bone alteration, the bone defect should be corrected by osteotomies, bone wedge grafts, or osteosynthesis. Severe joint degeneration can be caused by wrist instabilities, which can be radiocarpal or midcarpal, and normally requires more radical treatment. Treatment for Preiser disease is normally conservative treatment, which involves immobilisation using a cast. Surgery may also be resorted to.
Non-operative treatment
Some fractures of the scaphoid can be treated in a plaster cast. These are usually the fractures through the waist, which are undisplaced. However, scaphoid fractures that are displaced (i.e. the fracture fragments have moved apart) or fractures in the so-called proximal pole have a higher risk of not uniting and are often treated operatively. Scaphoid fractures that are treated non-operatively usually involve a plaster of Paris immobilisation for a period of six to twelve weeks. Careful x-ray, follow up, and CT scanning may be required to ensure the fracture has united.
Operative treatment
Scaphoid fractures that occur in the proximal pole of scaphoid fractures that are displaced often require operative treatment. Surgery is performed under general anaesthetic or regional anaesthesia (only the arm is made numb). The surgery takes between thirty and forty minutes. A tourniquet is used, which is like a blood pressure cuff around the upper arm, which prevents blood from obscuring the surgeon’s view. There are two main types of scaphoid surgery for fractures.
The first is the traditional ‘open’ surgery. This usually involves a three to four-centimetre incision either on the front or the back of the wrist, depending on the site of the fracture. The surgeon identifies the fracture under direct vision and places a bone screw, under x-ray control, into the scaphoid. The screw is buried deep inside the bone and is a permanent implant. 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 second type of surgery is a more modern type of technique, which involves small (two or three millimetre incisions). This is called the ‘percutaneous fixation technique’; this can only be done in the first few weeks after injury. This had the added advantage of less surgical dissection and, hopefully, less trauma to the surrounding structures. However, the overall healing rate between the percutaneous and open techniques is probably similar. Post-operatively the rehabilitation is often quicker with the percutaneous technique due to less soft tissue trauma.
Post-operative rehabilitation
The patients are usually mobilised within the first ten to fourteen days’ time. The range of movement rapidly returns before strengthening procedures occur. Sutures are often buried under the skin, and the ends of the suture need to be snipped, usually at ten days. Scaphoid fractures usually require six to eight weeks to heal, and this is confirmed with x-ray or CT scans.
Return to activities of daily living
Patients who are treated operatively, particularly with the percutaneous techniques, can return to driving and many activities of daily living within the first few days. Patients who are treated with more conventional, open four-centimetre incisions usually return to driving within two to three weeks. Patients who are treated non-operatively in a plaster of Paris often find it difficult to drive whilst the cast is on. Indeed, many insurance companies prevent patients from driving in a cast.
Return to work
Everyone has different work environments. Return to heavy manual labour often occurs after bone healing. Light duties can be tolerated within the first few days.
Complications
Non-union is the major complication of scaphoid fractures. This is an inability of the fracture to heal. It is more common in the proximal pole fractures and those fractures that have significantly displaced. Overall, the non-union rate for scaphoid fractures is about 15%. An untreated scaphoid non-union is likely to go on to develop osteoarthritis over a ten to fifteen-year period. Treatment in plaster of Paris has very few complications, apart from non-union. Occasionally stiffness can occur in the digits if the fingers are not moved early.