Unstable occult scaphoid fracture diagnosed by dynamic point-of-care ultrasound: a case report and review.

Background: The scaphoid is the most frequently fractured carpal bone, yet its diagnosis remains a significant clinical challenge. A substantial percentage of non-displaced fractures are missed on initial radiographs, leading to delays in treatment and an increased risk of serious long-term complications such as non-union and avascular necrosis. While advanced imaging like CT and MRI are highly accurate, they are associated with higher costs, radiation exposure (CT), and limited immediate availability. High-resolution musculoskeletal ultrasound has emerged as a rapid, non-invasive, and cost-effective alternative. Its unique ability to perform dynamic, real-time assessment of fracture stability offers a significant advantage over static imaging modalities. Case presentation: A 29-year-old woman presented to our outpatient clinic with acute left wrist pain following a traction-fall injury. An initial four-view radiographic series of the wrist revealed no definitive evidence of a fracture. Despite the negative imaging, clinical suspicion remained high due to persistent, exquisite point tenderness over the anatomical snuffbox. A point-of-care musculoskeletal ultrasound examination was performed, which revealed a clear hypoechoic cortical breach at the scaphoid waist. To assess mechanical stability, a dynamic stress maneuver-defined as a gentle, controlled "heel-toe" probe rocking that applies focal pressure across the fracture-was performed under real-time sonographic visualization. Gentle probe pressure combined with passive ulnar deviation of the wrist demonstrated visible gapping and micromotion at the fracture site, confirming it as mechanically unstable. Based on this definitive finding, the diagnosis was revised to an unstable occult scaphoid waist fracture, and the management plan was immediately upgraded to a rigid thumb spica splint. Long-term follow-up over 2 years showed radiographic and sonographic evidence of a stable fibrous union. Conclusion: This case report highlights the pivotal role of dynamic musculoskeletal ultrasound as an adjunct in the diagnostic algorithm for acute wrist trauma. It demonstrates its ability not only to identify a radiographically occult scaphoid fracture but, more critically, to provide immediate functional information about mechanical stability. This information is paramount for guiding appropriate and timely management to mitigate the risk of long-term complications. We advocate for the broader integration of dynamic ultrasound into the initial assessment of suspected scaphoid fractures.