Imaging description

Plain radiography is the first step in the evaluation of carpal bone injuries such as a scaphoid fracture, and it is effective in diagnosing most but not all carpal fractures. If radiography is negative, and clinical suspicion persists, further investigation with special radiographic views, CT scan, or MR imaging is necessary. Criteria for an occult fracture on multi-detector CT are the presence of a sharp lucent line, a discontinuity in the trabecular meshwork, and a break or step-off in the cortex. MR imaging is exquisitely sensitive to bone marrow abnormalities and therefore renders even non-displaced fractures obvious (Figure 34.1). MR imaging helps in detecting non-displaced fractures by showing a hypointense fracture line on T1-weighted images and increased signal intensity in areas of trabecular injury on fluid-sensitive sequences.

Importance

Detection of the occult fracture can be crucial for treatment planning. In many clinical settings, the diagnosis of a scaphoid fracture on the basis of radiography is delayed up to 2 weeks or more after the injury. Follow-up radiography demonstrates the initially occult scaphoid fracture because hyperemia and bone resorption at the fracture site make the fracture line more visible.