What is the scaphoid?

The scaphoid bone is one of the eight smaller carpal bones in your wrist. It lies on the thumb side of your wrist right below the radius, one of the two larger bones in your forearm. It’s involved in moving and stabilizing your wrist. An older name for it is the navicular bone.

You can find your scaphoid bone by holding your thumb up as you look at the back of your hand. The triangular indentation that’s formed by the tendons of your thumb is called the “anatomic snuffbox.” Your scaphoid is located at the bottom of this triangle.

The scaphoid’s position on the side of your wrist and relatively large size make it vulnerable to injury and fracture. In fact, it’s the most frequently fractured carpal bone, accounting for about 70 percentTrusted Source of carpal fractures.

The scaphoid has three parts:

  • proximal pole: the end closest to your thumb
  • waist: the curved middle of the bone that lies under the anatomic snuffbox
  • distal pole: the end closest to your forearm

About 80 percent of scaphoid fractures happen at the waist, 20 percent at the proximal pole, and 10 percent at the distal pole.

The site of the fracture affects how it will heal. Fractures in the distal pole and waist usually heal quickly because they have a good blood supply.

Most of the proximal pole has a poor blood supply that’s easily cut off in a fracture. Without blood, the bone dies, which is called avascular necrosis. Fractures in the proximal pole don’t heal as well or as quickly.

FOOSH stands for “fall onto an outstretched hand.” It’s the mechanism behind many upper limb fractures.

When you sense you are about to fall, you instinctively react by cocking your wrist and extending your arm to try to break the fall with your hand.

This protects your face, head, and back from injury, but it means your wrist and arm take the full force of the impact. When it causes your wrist to bend back farther than it’s meant to go, a fracture may occur.

The angle of your wrist when it hits the ground affects where a fracture happens. The farther your wrist is bent back, the more likely it is that your scaphoid bone will break. When your wrist is less extended, the radius bone takes the force of impact resulting in a distal radius fracture (Colles’ or Smith fracture).

A FOOSH injury commonly affects the scaphoid because it’s the main connection between your hand and forearm. When you fall on your hand, all of the energy produced when your hand hits the ground travels to your forearm through the scaphoid. The force puts a huge amount of stress on this small bone, which can cause a fracture.

FOOSH injuries occur in many sports, especially things like skiing, skating, and snowboarding. Wearing a wrist guard is an easy way to prevent these injuries.

Participating in sports that repeatedly stress your scaphoid bone, such as shot put or gymnastics, can also cause a scaphoid fracture. Other causes include a hard blow directly to your palm and motor vehicle accidents.

Scaphoid fractures often aren’t always obvious and can be hard to diagnose.

The most common symptom is pain and tenderness over the anatomic snuffbox. The pain is often mild. It may get worse with pinching and gripping.

There’s frequently no noticeable deformity or swelling, so it doesn’t look fractured. The pain may even improve in the days and weeks after the fracture. For these reasons, many people think it’s just a sprained wrist and delay getting appropriate treatment.

When not treated with immobilization right away, the fracture may fail to heal. This is called nonunion, and it can cause serious long-term complications. About 5 percentTrusted Source of scaphoid fractures are nonunion. Avascular necrosis can also cause nonunion.

X-rays are the primary diagnostic tool. However, up to 25 percentTrusted Source of scaphoid fractures aren’t seen on an X-ray right after the injury.

If a fracture isn’t seen, but your doctor still suspects you have one, your wrist will be immobilized with a thumb splint until repeat X-rays are taken 10 to 14 days later. By that time, a fracture has begun to heal and is more noticeable.

If your doctor sees a fracture but can’t tell if the bones are aligned correctly or needs further information, a CT scan or MRI can help your doctor determine the proper treatment. A bone scan can also be used but it’s not as widely available as the other tests.

The treatment you receive depends on:

  • alignment of the fractured bones: whether the bone ends moved out of position (displaced fracture) or are still aligned (nondisplaced fracture)
  • time between the injury and treatment: the longer the time, the more likely nonunion is
  • fracture location: nonunion occurs more often with proximal pole fractures

Casting

A nondisplaced fracture in the waist or distal pole of your scaphoid that’s treated soon after injury can be treated by immobilizing your wrist with a cast for six to 12 weeks. Once an X-ray shows the fracture is healed, the cast can be removed.

Surgery

Fractures that are in the proximal pole of the scaphoid, displaced, or not treated soon after injury require surgical repair. The goal is to put the bones back in alignment and stabilize them so they can heal properly.

After surgery, you will usually be in a cast for eight to 12 weeks. The cast is removed once an X-ray shows the fracture is healed.

For nonunion fractures, surgery with bone grafting is required where there’s a long time between the fracture and nonunion, the fractured bone ends aren’t close together, or the blood supply is poor.

When the time between fracture and nonunion is short, the fractured bone ends are close together, and the blood supply is good, a bone stimulator might be used.

Bone growth stimulation

Bone growth stimulation may involve injection of medication. Wearable devices can also stimulate both growth and healing by applying either ultrasound or a low level of electricity to the injured bone. In the right circumstances, these alternative may be helpful.

Whether you need surgery or not, you’ll likely need physical and occupational therapy for two or three months after the cast is removed to regain strength and mobility in your wrist and muscles around it.

When a scaphoid fracture isn’t treated right away, it may not heal properly. Possible complications include:

  • delayed union: the fracture hasn’t completely healed after four months
  • nonunion: the fracture hasn’t healed at all

This can lead to instability of the wrist joint. Years later, the joint will usually develop osteoarthritis.

Other potential complications include:

  • loss of wrist mobility
  • loss of function, such as decreased grip strength
  • avascular necrosis, which occurs in up to 50 percent of fractures in the proximal pole
  • osteoarthritis, especially if nonunion or avascular necrosis occurred

The outcome is usually very good if you see your doctor soon after the fracture, so your wrist is immobilized early. Almost everyone will notice some wrist stiffness after a scaphoid fracture, but most people will regain the mobility and strength they had in their wrist before the fracture occurred.

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