Review Question - QID 107092

The two bones indicated by the arrows are the scaphoid and capitate bone.

The scaphoid bone is the most commonly fractured carpal bone. Practitioners must have a high index of suspicion for scaphoid fracture, as it may commonly be misdiagnosed as a wrist sprain. MRI is the most sensitive radiological means to diagnose a scaphoid fracture. Plain radiographs may take 1-2 weeks to show evidence of scaphoid fracture. A popular mnemonic for remembering the order of the carpal bones is “Some Lovers Try Positions That They Can’t Handle.”

Daniels et al. discuss the bony anatomy of the hand and wrist. The bony structures include eight carpal bones, five metacarpals, and 14 nonsesamoid bones comprising the phalanges. The proximal carpal row includes the scaphoid, lunate, triquetrum, and pisiform (the first half of the mnemonic above). The distal carpal row includes the trapezium, trapezoid, capitate, and hamate (the second half of the mnemonic above).

Cheung et al. discuss the biomechanics of a wrist injury. The most common mechanism involves a fall onto an outstretched hand, resulting in forced excess dorsiflexion. Cheung reports that cadaveric studies have shown that when the wrist is kept in 95-100 degrees of extension, and then a dorsiflexion force is applied radially, this can lead to fractures of the scaphoid bone.

Figure A is a radiograph of the hand. The red arrows point to scaphoid and capitate, as described above. Illustration A depicts a cartoon with labeled bones of the hand next to a mirrored hand radiograph for correlation.

Incorrect Answers:
Answers 1-2, 4-5: As discussed above and displayed in the illustration, the indicated bones are scaphoid and capitate.