Introduction:
The scaphoid bone is one among the carpal bones of the wrist. The word “scaphoid” is derived from a Greek word meaning “boat” because the scaphoid bone resembles a boat with its long and curved shape. Scaphoid fractures are a possible cause of hand or wrist pain. These fractures account for about 70% to 80% of all carpal bone fractures. Though it can occur at any age, adolescents and young adults are most commonly affected.
What Is a Scaphoid?
The wrist is formed by two bones- the radius, the ulna, and small carpal bones. There are eight smaller carpal bones in the wrist, and the scaphoid bone is one among them. These bones allow movements of the hands and wrist. This scaphoid bone is located on the thumb side of the wrist, right below the radius. The scaphoid bone is involved in moving and stabilizing the wrist. It was before called the navicular bone. There is a triangular indentation that is formed by the tendons of the thumb called the anatomic snuffbox, and scaphoid bone is located at the bottom of this triangle.
The scaphoid bone has three parts:
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Proximal pole.
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Waist.
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Distal pole.
The proximal pole is the end that is closest to the thumb.
The waist is the curved part, and it is the middle of the bone that lies under the anatomic snuffbox.
The distal pole is the end that is closest to the forearm.
What Is a Scaphoid Fracture?
A scaphoid fracture happens when there is a break or injury to the scaphoid bone. This scaphoid fracture usually happens due to a fall onto an outstretched hand. Scaphoid fractures are the most common fractures of the carpal bones. And healing of scaphoid fracture takes a long time, sometimes the fractured bone does not completely heal in a condition known as nonunion.
Why Are Scaphoid Bones More Prone to Fracture?
The location of the bone on the side of the wrist and its large size make it vulnerable to injuries and fractures. About 80 % of scaphoid fractures occur at the waist, and 20 % of the scaphoid fractures occur at the proximal part of the scaphoid bone.
How Does a Scaphoid Fracture Occur?
Scaphoid fractures are usually caused by a fall onto the outstretched hand. The force of the injury causes damage to the scaphoid bone. The injury can happen during any sports activity or motor vehicle collision. There are no particular risk factors that can increase the risk of developing the fracture. There are two types of scaphoid fractures:
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Displaced scaphoid fracture.
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Non displaced scaphoid fracture.
Displaced Scaphoid Fracture:
Scaphoid fractures are called displaced when the bones have shifted out of position. These types of displaced fractures require invasive treatment because healing is less predictable.
Nondisplaced Scaphoid Fractures:
When the bones have not shifted out of position, then it is called nondisplaced scaphoid fractures.
What Are the Signs and Symptoms of a Scaphoid Fracture?
Scaphoid fractures cause pain and swelling in the anatomic snuffbox and on the thumb side of the wrist following the fall. The pain gets severe when you try to pinch or grasp something. There will be no visible deformity, and people may assume the pain to be due to a wrist sprain. If the pain in the wrist does not go away in a day or two, it can be indicative of a fracture.
The other symptoms of a scaphoid fracture include:
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Localized wrist swelling.
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Localized bruising.
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Pain on the wrist on palpation.
How Long Does Scaphoid Fractures Take to Heal?
The scaphoid bone has a retrograde blood supply. Retrograde blood supply means the blood flows from a small vessel, enters the most distant part of the bone, and then flows back through the bone to offer nutrition to the cells of the bone. This blood flow gets disturbed in case of a scaphoid fracture. Because of this, necessary oxygen and nutrients are not supplied to the bone cells.
According to the location of the fracture, the recovery period varies. The fractures in the distal pole and the waist usually heal quickly as these locations have reasonable amounts of blood supply, whereas it may take a long time for fractures on the proximal pole due to insufficient blood supply. And the blood supply gets easily cut off in a fracture. When there is no blood supply to the bone, then the bone dies, resulting in a condition known as avascular necrosis.
How Are Scaphoid Fractures Diagnosed?
The diagnosis of scaphoid fractures is quite difficult because the bone fractures do not show up on the X-ray taken right after the injury. Particularly, the nondisplaced type of scaphoid fracture does not show up on an X-ray.
And if the doctor detects a fracture in the scaphoid bone and wants to see if the bones are in position, a few other diagnostic tests may be suggested, such as an MRI or CT (computed tomography). Magnetic resonance imaging (MRI) may be recommended to plan proper treatment.
Though 25 % of the scaphoid fractures are not seen on an X-ray right after the injury, X-ray is considered the primary diagnostic tool.
How to Treat Scaphoid Fractures?
The treatment for scaphoid fractures depends on the following conditions:
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Location of the fracture.
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The duration between the injury and the treatment.
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Position of the fractured bones.
The treatment options are:
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Casting.
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Surgery.
Casting:
The casting procedure is done when the fracture is a nondisplaced one and when treated soon after the injury. The wrist is immobilized with a cast for six to twelve weeks. Later, when an X-ray is taken to ensure that the fracture is healed, the cast is removed.
Surgery:
Surgery is preferred in the following scenarios:
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Fractures that occurred in the proximal pole of the scaphoid.
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If it is a displaced type of fracture.
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If not treated soon after the injury.
The foremost aim of the surgery is to bring back the fractured bones in position and to stabilize them for better healing. After the surgery is done, a cast is placed for eight weeks to twelve weeks. And the cast is removed once the X-ray shows that the fracture has healed.
In the case of nonunion fractures, surgery along with bone grafting is required.
What Are the Complications of Scaphoid Fractures?
When the scaphoid fractures are not treated right away, the possible complications are:
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Delayed union- Fracture that does not completely heal even after four months.
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Nonunion- fractures that have not healed at all.
The other complications include:
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Wrist immobility.
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Not being able to hold or grasp anything.
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Avascular necrosis.
Conclusion:
Though scaphoid fractures are common, they present unique challenges like the geometry of the fractures and the difficulty in diagnosis. However, timely diagnosis with appropriate immobilization, and referral to a surgical opinion when indicated can decrease the likelihood of severe adverse outcomes.