Scaphoideum

Scaphoideum, also known as the scaphoid bone or os scaphoideum, is one of the eight carpal bones of the human wrist. It lies on the radial (thumb) side of the proximal carpal row and is boat-shaped, acting as a bridge between the proximal and distal carpal rows. The bone forms the floor of the anatomical snuffbox and plays a key role in wrist stability and motion.

Anatomy and articulations

The scaphoid has a proximal pole, a narrow waist, and a distal pole. It articulates with several neighboring bones: proximally with the radius, medially with the lunate, laterally with the trapezium and trapezoid, and distally with the capitate. This arrangement helps coordinate movements between the two carpal rows and the forearm.

Blood supply

The primary arterial supply to the scaphoid comes from branches of the radial artery, entering the bone distally and traveling in a retrograde pattern toward the proximal pole. This retrograde flow makes the proximal portion particularly susceptible to avascular necrosis after fracture if blood flow is disrupted.

Clinical significance

Fractures of the scaphoid are common wrist injuries, especially after a fall on an outstretched hand. Classic signs include tenderness in the anatomical snuffbox and swelling. Initial radiographs may be negative, and occult fractures can be detected with MRI or CT or by repeat imaging after a short interval. Treatment depends on fracture location and stability: non-displaced fractures are typically immobilized in a thumb spica cast for several weeks, while displaced or unstable fractures may require surgical fixation with a screw or other hardware. The waist and proximal pole fractures carry higher risks of nonunion and, in proximal pole fractures, avascular necrosis due to the peculiar blood supply.

Imaging and prognosis

With timely diagnosis and appropriate management, many scaphoid fractures heal well. Delayed treatment or fracture nonunion can lead to chronic wrist pain and degenerative arthritis.