Fractures

What’s the Cause of This Boy’s Pain in the Wrist?

Roli Agrawal, MD

A 15-year-old previously healthy boy presented to the emergency department with a left wrist injury that had occurred 2 to 3 months ago. He had slipped on ice and had fallen with his hand flexed. After the injury, he had developed intermittent pain in his left wrist. Over time, the pain had increased, and he now was experiencing pain every time he flexed or extended the wrist. He is an avid baseball and softball player. He had kept up with his sports despite the pain.

Physical examination showed tenderness and swelling directly over the left anatomic snuffbox. He had a weak and painful grip. His range of motion also was decreased in all planes, especially the flexion and radial deviation of the wrist.

Anteroposterior and oblique radiographic views of his wrist are shown here.

 wrists

What is the cause of this boy’s persistent wrist pain?

A. Fracture and dislocation of the distal radius

B. Osteomyelitis of the radius

C. Fracture of the scaphoid

D. Aggressive lytic lesion of the scaphoid

E. Rickets

Answer: Fracture of the scaphoid

Plain radiographs of the left wrist demonstrate a fracture through the waist of the scaphoid (arrows, Figures 1 and 2). There also is increased lucency and marginal sclerosis. These findings suggest nonunion of the scaphoid with avascular necrosis.

Scaphoid bone fracture is the most common fracture of the carpal bones. It usually is caused by a fall on the outstretched hand (FOOSH) or forced dorsiflexion of the wrist. The diagnosis of scaphoid fracture can be challenging. However, a timely diagnosis is critical, since delay in treatment is associated with complications such as nonunion, avascular necrosis, and early-onset degenerative arthritis of the wrist.

In children, the incidence of scaphoid fracture peaks at 15 years of age. This fracture is uncommon in the first decade of life due to a protective cartilage around the ossification nucleus of the immature bone.

wristsScaphoid fractures are commonly classified by the location of the fracture: distal pole (distal third), waist (middle third), and proximal pole (proximal third). Waist fractures are most common (60% to 80%), followed by distal (15%) and proximal (5%) fractures. However, in preadolescent children, distal fractures are most common. The blood supply of the scaphoid bone is tenuous and is at risk of disruption by the fracture. This can have a negative impact on its healing and increase the risk of nonunion and avascular necrosis of the bone. Nonunion complicates 5% to 10% of scaphoid fractures, while avascular necrosis is associated with 13% to 50% of scaphoid fractures.

Scaphoid fractures may cause very little pain, swelling, or limitation of motion at the joint. A high index of suspicion is therefore needed. Any patient who presents with tenderness over the anatomic snuffbox after FOOSH should be evaluated for a scaphoid fracture. Other suspicious signs include pain on radial deviation and active range of motion at the wrist.

Plain radiographs often are the first step in evaluation of these fractures. Their sensitivity, however, is only 65% to 70%. Anteroposterior, lateral, and oblique views should be done in any patient with wrist trauma. If the radiographs are negative for fracture despite a high clinical suspicion, it is recommended to either treat empirically or pursue further imaging.

Magnetic resonance imaging (MRI) is considered the gold standard for diagnosing occult fractures, given its sensitivity of 95% to 100% and specificity of 100%. MRIs also are useful in diagnosing associated ligamentous and soft tissue injuries. Bone scans and computed tomography scans can be considered to aid in the diagnosis when MRI is unavailable. If the patient is treated empirically with a cast, the radiographs should be repeated in 2 weeks; bone resorption at the site of the fracture is expected to make the fracture visible.

The prognosis of the fracture depends on the site involved. Distal fractures usually heal without complications. Waist fractures are at risk of nonunion and avascular necrosis. Proximal pole fractures have the poorest healing (averaging 3 to 6 months) and are at the highest risk of nonunion and avascular necrosis due to the nature of their blood supply. Displacement and angulation of the fracture and late diagnosis also are indicators of a poor prognosis.

Ninety percent of acute nondisplaced scaphoid fractures in children heal nonoperatively with cast immobilization. The duration of immobilization depends on the location of the fracture. Proximal fractures also require evaluation for surgical intervention. One-third of patients with scaphoid fracture present late with nonunion. In these patients, surgical reduction and internal fixation usually is considered.

Our patient presented late, with nonunion and avascular necrosis. He was treated with autogenous distal radius bone graft and internal fixation with a single screw through the carpal bone. Additionally, he wore a thumb spica cast for approximately 2 weeks.

Since scaphoid fractures result from a relatively minor trauma, and because the initial radiographs may be falsely negative, one needs to have a high index of suspicion to make the diagnosis.

Dr Agrawal is a general radiologist at Detroit Medical Center in Michigan.

William Yaakob, MD—Series Editor:Dr. Yaakob is a radiologist in Tallahassee, Florida.