The scaphoid is the most commonly fractured carpal bone. Although the scaphoid is named for its resemblance to a boat shape (Greek skafos = boat), it is often referred to as a twisted peanut shape (Figure 14.1).¹,² The scaphoid spans both the proximal and distal carpal rows and plays a key role in stability of the carpus. The scaphoid comprises three regions: distal pole (tubercle), waist, and proximal pole. The diagnosis of a scaphoid fracture can be challenging due to delayed patient presentation or the occult nature of the fracture on early radiographs. Malunion or nonunion of scaphoid fractures can lead to altered carpal kinematics, diminished grip strength, and radiocarpal arthritis.

Mechanism of injury—Injury to the scaphoid is typically from a fall on an outstretched hand (35%), which causes extreme wrist extension and compression of the scaphoid against the distal radius. Similar forces can also be generated during athletic competition (59%). High-energy mechanisms such as a fall from height or motor vehicle collision contribute to the remaining scaphoid fractures.

Epidemiology—The scaphoid is the most frequently fractured bone in the carpus. The most common demographic for this injury are males in their 20s to 30s.³,⁴ The reported incidence in the United States is 1.47 per 100 000 person-years, although a study of the U.S. military found a higher incidence of scaphoid fractures with 121 per 100 000 person-years. This injury is relatively rare in children and elderly adults.

Blood supply—The scaphoid receives blood from two main sources.⁵ The proximal pole of the scaphoid is notoriously high risk for avascular necrosis (AVN) because it receives its blood in a retrograde fashion from the dorsal scaphoid branches of the radial artery. These branches supply approximately 80% of the bone and enter the scaphoid via the nonarticular dorsal ridge and distal tubercle. The second source of blood is from the volar scaphoid branches of radial artery, which enter the bone at the scaphoid tubercle and supply the distal 20% of the scaphoid.

Presentation—Patients often present with radial-sided wrist pain that localizes to the anatomic snuffbox and is worse with gripping or squeezing. They may recall a specific traumatic event that coincides with the onset of pain. If patients present early, they may report swelling or ecchymosis around the wrist. If the injury is chronic, then the patient may complain of loss of wrist range of motion (ROM), weakness, and difficulty performing push-ups.

Physical examination—On examination, tenderness to palpation in the anatomic snuffbox or distal tubercle of scaphoid should raise suspicion for a scaphoid fracture (Figure 14.2). In addition, compression of the thumb metacarpal against the scaphoid can be performed to elicit pain. Careful evaluation of remaining wrist and elbow should be performed to rule out any concomitant injuries.

Imaging—Posteroanterior (PA) in neutral and ulnar deviation (scaphoid), lateral, and 45° oblique radiographs (Figure 14.3) should be obtained.
Note: Up to 25% of nondisplaced fractures may not be visible on plain radiographs until 7 to 14 days after initial injury.

Differential diagnosis

Classification—Scaphoid fractures can be classified by location, chronicity, and stability.⁶ The stability has been stratified according to the Herbert’s classification system, which divides fractures into four groups: Type A = stable acute, Type B = unstable acute, Type C = delayed union, and Type D = nonunion. Fractures with >1 mm of displacement are considered unstable.

If a scaphoid fracture is suspected but not evident on initial radiographs, then the patient is provisionally treated as if a scaphoid fracture is present and is placed into a thumb spica splint (TSS).³ At this point, either an early MRI is obtained or radiographs are repeated in 2 weeks. The provisional treatment of a suspected fracture is based on evidence that failure to treat a stable scaphoid fracture within 4 weeks increases the nonunion rate.