Understanding Scaphoid Fracture: Diagnosis, Classification, and Treatment Options

Scaphoid fracture is the most common carpal bone fracture, which occurs when the wrist is forcefully dorsiflexed, pronated, and ulnarly deviated. It is most common in the third decade of life, and the waist of the scaphoid is the most common location for the fracture.

The diagnosis of scaphoid fracture is usually made by radiographs, but CT or MRI may be needed for confirmation. Treatment depends on the severity of the fracture, but may involve a prolonged period of cast immobilization, percutaneous surgical fixation, or open reduction and internal fixation.

Epidemiology

• Incidence: Scaphoid fracture is the most common carpal bone fracture, accounting for 15% of acute wrist injuries and 60% of all carpal fractures.
• Demographics: Scaphoid fracture is more common in males than females, with a male-to-female ratio of 2:1. The most common age group for scaphoid fracture is the third decade of life.
• Anatomic location: The most common location for scaphoid fracture is the waist, accounting for 65% of all scaphoid fractures. The proximal third and distal third of the scaphoid are the other two common locations, accounting for 25% and 10% of scaphoid fractures, respectively.

Etiology

5. Pathophysiology: The most common mechanism of injury for scaphoid fracture is axial load across a hyper-dorsiflexed, pronated, and ulnarly deviated wrist. This mechanism of injury is common in contact sports, such as football and hockey.
5. Associated conditions: Scaphoid nonunion advanced collapse (SNAC) is a complication of scaphoid fracture that can occur if the fracture does not heal properly. SNAC is characterized by collapse of the scaphoid and arthritis of the wrist.

Anatomy

• Osteology: The scaphoid is a complex 3-dimensional bone that is described as resembling a boat, skiff, and twisted peanut. It is the largest bone in the proximal carpal row and is covered by articular cartilage on more than 75% of its surface. The scaphoid articulates with the radius, lunate, trapezium, trapezoid, and capitate.
• Blood supply: The scaphoid has a poor blood supply. The major blood supply is the dorsal carpal branch of the radial artery, which enters the scaphoid in a nonarticular ridge on the dorsal surface. This blood supply supplies the proximal 80% of the scaphoid via retrograde blood flow. The distal 20% of the scaphoid is supplied by the superficial palmar arch.
• Biomechanics: The scaphoid is the link between the proximal and distal carpal rows. It flexes with wrist flexion and radial deviation and extends during wrist extension and ulnar deviation.

Scaphoid Fracture Classifications:

Herbert and Fisher Classification

This classification is based on the stability of the fracture.

• Type A: Stable, acute fractures. These fractures are usually non-displaced and have a good prognosis for healing.
• Type B: Unstable, acute fractures. These fractures are displaced or have a high risk of displacement. They may require surgery to stabilize the fracture.
• Type C: Delayed union. These fractures have not healed after 6-8 weeks. They may require surgery to promote healing.
• Type D: Nonunion. These fractures have not healed after 12 weeks. They may require surgery to repair the fracture.

Mayo Classification

This classification is based on the location of the fracture line.

• Type I: Distal tubercle fracture. This fracture occurs at the tip of the scaphoid.
• Type II: Distal articular surface fracture. This fracture occurs on the surface of the scaphoid that articulates with the radius.
• Type III: Distal third fracture. This fracture occurs in the distal third of the scaphoid.
• Type IV: Middle third fracture. This fracture occurs in the middle third of the scaphoid.
• Type V: Proximal third fracture. This fracture occurs in the proximal third of the scaphoid.

Russe Classification

This classification is based on the fracture pattern.

• Type I: Horizontal oblique fracture line. This fracture line runs horizontally across the scaphoid.
• Type II: Transverse fracture line. This fracture line runs across the scaphoid perpendicular to the long axis of the bone.
• Type III: Vertical oblique fracture line. This fracture line runs vertically across the scaphoid.

 

Scaphoid Fracture Presentation:

History: The patient typically reports a high or low energy fall onto an outstretched hand.

Symptoms: The patient may experience variable level of pain over the wrist.

Physical exam: The physical exam may reveal wrist swelling, but rarely any ecchymosis, hematoma, or gross deformity. The patient may also have pain with resisted pronation and circumduction of the wrist.

Provocation tests: The scaphoid compression test is a positive test when pain is reproduced with axial load applied through the thumb metacarpal. This test has a sensitivity and specificity of 87-100% and 74%, respectively, when all three tests are positive within 24 hours of injury.

Imaging: The recommended radiographic views for scaphoid fracture are neutral rotation PA, lateral, and semi-pronated (45°) oblique. The scaphoid view, which is taken with the wrist in 30 degrees of extension and 20 degrees of ulnar deviation, is the best view to visualize waist fractures. If the radiographs are negative and there is a high clinical suspicion of scaphoid fracture, repeat radiographs can be done in 14-21 days.

Bone scan: Bone scan is indicated for occult fractures in the acute setting. It has a specificity of 98% and sensitivity of 100% when done at 72 hours.

MRI: MRI is the most sensitive imaging modality for scaphoid fracture, especially in the acute setting. It can also be used to assess the vascular status of the bone and to diagnose proximal pole avascular necrosis (AVN).

CT scan: CT scan is the best modality to evaluate fracture location, angulation, displacement, fragment size, extent of collapse, and progression of nonunion or union after surgery. However, it is less effective than bone scan and MRI to diagnose occult fracture.

Scaphoid Fracture Treatment:

The treatment of scaphoid fracture depends on the stability of the fracture. Stable, nondisplaced fractures can be treated with cast immobilization. Unstable fractures may require surgery, such as percutaneous screw fixation or open reduction internal fixation.

Cast immobilization is the most common treatment for scaphoid fracture. The cast is typically worn for 8-12 weeks, or longer for high-risk fracture patterns.

Percutaneous screw fixation is a minimally invasive surgery that involves inserting a screw through the skin and into the scaphoid to stabilize the fracture. This surgery can shorten the time to healing and allow for a faster return to activities.

Open reduction internal fixation is a more invasive surgery that involves making an incision in the wrist to visualize the fracture and reduce it (align the bones). This surgery is typically reserved for unstable fractures or fractures that have not healed with cast immobilization.

The complications of scaphoid fracture treatment include:

• Scaphoid nonunion: This is a condition in which the fracture does not heal. The risk of nonunion is higher for proximal pole fractures and fractures that are displaced or unstable.
• Osteonecrosis: This is a condition in which the bone dies due to lack of blood supply. The risk of osteonecrosis is higher for proximal pole fractures.
• Malunion: This is a condition in which the fracture heals in an incorrect position.
• Subchondral bone penetration with arthrosis due to prominent hardware: This is a condition in which the screw penetrates the subchondral bone and causes arthritis.
• SNAC wrist: This is a condition in which the scaphoid collapses and the lunate dislocates.

The prognosis for scaphoid fracture treatment is generally good. The majority of fractures will heal with appropriate treatment. However, there is a risk of complications, such as nonunion, osteonecrosis, and malunion.