Scaphoid fractures comprise 2,5% of wrist fractures and up to 60% of carpal (the 8 small bones in wrist) fractures. The scaphoid links the base of the thumb to the wrist, and fractures are commonly seen in the younger sport playing population who fall on an outstretched wrist, putting their hand out and hitting the ground on the thenar (thumb) side of the palm. This is commonly seen in cyclists, skateboarders and athletes who fall on hard surfaces. Pain is typically at the base of the thumb on the palm as well as the back side of the wrist. There is swelling of the joint due to bleeding inside the joint. All wrist movements are painful and weight bearing on the wrist is very tender.
The scaphoid is the most problematic bone in the body with regards to its ability to heal. There are more papers written on the union process of the scaphoid than any other bone in the body. This is because the blood supply to the scaphoid arises from distal to proximal (reversed from conventional anatomy), the scaphoid is completely covered with cartilage, and the fact that the scaphoid moves with every inch of wrist movement, balancing complex torsional forces.
The scaphoid is boat shaped and most fractures (65%) go through the waist of the scaphoid i.e. through the middle of the bone. The more proximal (closer to wrist) the fracture, the greater the chance that the blood supply is cut off (avascular necrosis) and the fracture does not heal (non-union). There is a 10-16% risk that the fracture does not unite (heal) in spite of cast immobilisation.
The diagnosis of a scaphoid fracture is usually easily made with plain X-rays with clinical stigmata. Some patients present with a clinical picture that is very suggestive of a scaphoid fracture but X-rays are normal. In this group, an MRI scan is very useful to diagnose a hidden (occult) fracture, with bone swelling seen on T2 sequence. CT scans are useful to show displacement and deformity, especially in a chronic setting.
Undisplaced scaphoid fractures can be treated with cast immobilisation for 8-12 weeks. Recent data suggests that even undisplaced fractures can be unstable and there is a tendency to operate (putting a compression screw across fracture) these cases early, particularly in the active sportsman. Fractures that are displaced more than 1mm should be treated surgically as early as possible. A scaphoid non-union is treated surgically with bone grafting and screw fixation.