Anatomy of the Scaphoid Bone

The wrist consists of two rows of carpal bones, one row on top of the other. The scaphoid bone is one of the eight small wrist bones.

Because of its location and size, the scaphoid bone is the most common wrist bone to fracture. In most cases, falling causes the fracture. The location and severity of the break will dictate if casting or surgery is required for treatment of a scaphoid fracture.

Anatomy

Some say the scaphoid bone is boat-shaped. Actually, the word scaphoid comes from the Greek word skaphos, meaning ‘boat’. Others describe the scaphoid bone as looking similar to a cashew nut in size and shape. It's one of the largest carpal bones and is located in the second row below the thumb, next to the radius.

You can find this bone by holding your thumb in a ‘hitchhiking’ position. It's located at the base of the hollow made by the stretched thumb tendons. This hollow area, called the ‘anatomic snuffbox’, is typically tender or painful when the scaphoid bone is fractured.

Function

The scaphoid bone is particularly important because it links the two rows of wrist bones together, helping to stabilize the wrist.  

Associated Conditions

When falling on an outstretched hand, the scaphoid bone is the most likely wrist bone to sustain the greatest impact, which can result in a scaphoid fracture.

When we fall, we instinctively try to protect ourselves. While falling, we bend our wrists and open our hands flat so that our hand hits the ground first, cushioning our bodies from the fall. A wrist fracture can happen whether we fall forward or backward.

There are no specific risk factors or diseases that make a scaphoid fracture more likely. Falling is by far the most common cause of fracture. However, injury can result from a direct blow to the wrist or trauma from accidents, such as motor vehicle accidents. Repeated stress can also lead to fracture, as can be the case with gymnasts.

Some doctors recommend wrist guards if you participate in high-energy activities where falling is common, like skating, skateboarding, and snowboarding. 

As with any fracture, the severity of fracture is dependent on bone movement. Scaphoid fractures may be non-displaced or displaced.

• Non-displaced fracture: When the bones remain aligned
• Displaced fracture: When the bones have moved and are no longer aligned properly. Pieces of bone may overlap or be separated by gaps.

Symptoms of Scaphoid Fracture

Pain and swelling on the thumb side of the wrist and in the anatomic snuffbox area typically are the first indication of a scaphoid fracture. Most people will recall a specific incident that occurred—falling, injury, and/or trauma.

Doctors will take an extensive history when evaluating potential scaphoid fractures. They will also look for:

• Pain
• Swelling
• Bruising
• Loss of wrist motion

For some people, the pain and swelling are mild. Some assume a wrist sprain rather than a fracture and only seek medical advice when the pain doesn’t subside with time.

While a wrist sprain is possible, a good indicator of a more severe injury is a significant increase in pain when grasping or pinching objects or moving your thumb. 

A delay in diagnosing a scaphoid fracture can cause complications that include:

• Fracture not healing properly
• Delayed healing
• Decreased grip strength
• Decreased range of motion
• Osteoarthritis

Prompt diagnosis and treatment of a scaphoid fracture will help avoid potential complications.

Diagnosing a Scaphoid Fracture

Diagnostic options for a scaphoid fracture include:

• Radiographs (X-rays): These are used to provide images of bones and diagnose fractures. However, some scaphoid fractures are difficult to see in an X-ray because of the multiple small wrist bones. If a scaphoid fracture is suspected, some doctors will recommend a follow-up X-ray after wearing a splint or cast for 2 to 3 weeks. At this time, some fractures become more evident.
• Magnetic resonance imaging (MRI): This can show both the soft tissues and bones. An MRI can often show fractures that are not evident on X-rays.
• A computerized tomography (CT) scan: This can also show fractures that are not seen on X-rays. CT scans can show details of a displaced fracture enabling a comprehensive treatment plan to be formed.

Treatment

The treatment recommendations for scaphoid fractures will depend on:

• Location of the break
• Displaced or non-displaced fracture
• Blood supply to the injured area
• Time elapsed since the injury

A good blood supply to the bones enables healing since blood carries oxygen and nutrients needed for healing. Unfortunately, the wrist bones have a limited blood supply that can hinder healing.

Prompt treatment of a scaphoid fracture will help avoid potential complications.

According to the American Society for Surgery of the Hand maximizing function, relieving pain, and preventing arthritis are the primary goals of treatment. Treatment for a scaphoid fracture ranges from casting to surgery.

Non-Surgical Treatment

Casting or splinting is the usual non-surgical treatment for a scaphoid fracture that is recent, non-displaced, and near the thumb so that it has an adequate blood supply.

For this type of fracture, the cast or splint is placed on the forearm and hand, from below the elbow to include the thumb.

Immobilization is especially effective in treating scaphoid fractures in children.

Healing time varies from person to person. Healing of the fracture is monitored with radiographs. A cast is typically worn from six to 12 weeks. Removal of the cast is based on when the bones appear to form a union.

Surgical Treatment

The goal of surgery is to realign and stabilize the fracture. Surgery increases the chance of proper healing.

Non-displaced fractures in areas with limited blood supply often heal better with surgery. Fractures, with even small amounts of displacement, are prone to heal improperly. Therefore, surgery is the recommended course of action.

With surgical treatment, a small pin or screw is used to join the bone fragments and hold the fragments together. Typically, you would be referred to an orthopedic surgeon for this procedure.

Surgery can reduce the time a cast is worn or eliminate the need for a cast. Some believe surgical intervention enables normal wrist movement to return more quickly than non-surgical treatment.

Alternative Treatment

A bone stimulator, a small device that delivers pulsed electromagnetic waves or low-intensity ultrasonic waves, can assist in healing. These treatments encourage calcification so that the two ends of the bone come together, forming a union.

Recovery

While the fracture is healing you should avoid:

• Lifting and carrying more than one pound
• Pushing or pulling objects heavier than one pound
• Participating in high impact activities
• Participating in activities with a high chance of falling
• Throwing with the injured arm
• Using machinery that vibrates

The lack of blood supply to the wrist bones causes scaphoid fractures to heal more slowly than most fractures. Some patients require six months or more to heal and need to keep the wrist immobile during this time.

It is important that fingers are intentionally moved and exercised during healing to maintain strength and range of motion. 

A hand therapist can assist with recovery and help with returning to normal activities once healing is complete.

Possible Complications

The possible complications that can occur after a scaphoid fracture include:

• Delayed union: The fracture not completely healed after 4 months of wearing a cast.
• Non-union: No healing of separated bone fragments.
• Malunion: When the fracture heals incorrectly, bones are misaligned, possibly leading to pain with gripping or wrist movement.

These complications can be corrected with surgery. 

Osteoarthritis occurs when cartilage in the joint, which provides a cushion between bones, becomes worn and frayed. The cartilage can be so worn that bone rubs on bone causing pain. Osteoarthritis can develop after any joint fracture but is more likely to develop with reoccurring injury and imperfect healing.

A Word From Verywell

While a minor fall and a sore wrist may not seem cause for concern, it's important to seek medical attention. What you may think is a sprain could indeed be a fracture, which will more successfully heal the sooner you receive treatment.