There are eight bones lined up in two rows in the wrist that, as a unit, are referred to as the carpal bones. The row closer to the hand is called the distal row, and the one closer to the forearm is the proximal row. The scaphoid bone is the only one that is part of both rows, which makes it the most likely bone in the wrist to be injured.
Causes of a Scaphoid Fracture
The scaphoid is fractured most often when someone falls and lands on an outstretched hand meant to break the fall. Instead of breaking the fall, the wrist itself painfully fractures. It is rare for any sign of the fracture to show up, and since there is no bruise or extreme swelling, it's easy for someone to think it was just a simple sprain and not have the injury examined by a hand surgeon. Sometimes it may be months or years before the fracture is discovered.
Diagnosis of the Wrist
X-rays of the wrist are the usual way to diagnose a scaphoid fracture, but unless the scaphoid was moved out of place, x-rays taken in the week after the injury may not show the fracture and it may be considered a sprain.
If the area right above the scaphoid, in the hollow "snuffbox" where the thumb meets the wrist, is very tender, a scaphoid fracture is likely and a splint should be used to protect the bone. A couple weeks after the injury, a second x-ray will usually confirm whether or not the scaphoid was fractured by showing changes in the bone at the sight of the fracture.
Sometimes it may be hard to wear a splint for two weeks, or the second x-ray might still fail to show the fracture even though the hand surgeon feels it is likely. While they cost more than an x-ray, an MRI, CT, or bone scan can often show if the scaphoid was fractured.
Treatment of a Fractured Scaphoid
If a fractured scaphoid didn't move, a cast that covers the forearm, hand, and thumb is used to keep the wrist stable until the bone heals. This can take as few as six weeks, but since the supply of blood to different parts of the scaphoid can be so different and may have been changed by the injury, it may take longer for the bone to heal.
The part of the scaphoid that is closest to the forearm is the most susceptible to having its blood supply reduced or eliminated. This can lead to that part of the scaphoid dying. To correct that, or if the fracture happened in that part of the bone, or the scaphoid was moved by the injury, surgery may be needed to repair the fracture. During the surgery, the hand surgeon will use pins or a screw to hold the bone together, and may graft some additional bone onto the scaphoid.
Using pins or screws to keep the bone stable may be the better treatment even when the scaphoid hasn't moved or has adequate blood supply.
Complications of the Fracture
- Scaphoid Non-Union: Unless the fracture is identified and treated, the scaphoid isn't likely to heal on its own. Since the supply of blood can be affected by the injury, even with treatment, the scaphoid may not get enough blood to heal, and this can lead to eventual arthritis if it fragments or becomes mis-aligned. Surgery can correct the scaphoid and help it heal if the fracture is treated before the arthritis develops.
- Avascular Necrosis: If the supply of blood to the scaphoid is reduced enough, part of it may die. This usually causes the scaphoid to collapse in fragments and results in arthritis. Surgery to repair the blood supply can keep this from happening, but only if the surgery is attempted before arthritis presents itself.
- Post-Traumatic Arthritis: If not caught before arthritis develops, surgery to remove dead or dying bone, or to fuse part of the wrist joint, might be considered just to save what is left and keep it from getting worse.