Os centrale

The os centrale (os centrale carpi) is an accessory carpal bone of the wrist — the most common of roughly 30 described accessory carpal elements, and the only one listed in the official anatomical nomenclature (Terminologia Anatomica). When present, it is a small, separate ossicle situated in the central region of the carpus, typically interposed between the scaphoid, trapezoid, trapezium, and the head of the capitate, forming part of the midcarpal complex.

Embryology. It represents a normally transient cartilaginous element of the developing carpus that usually fuses with the dorsal aspect of the scaphoid; failure of this fusion leaves a persistent separate ossicle.

Nomenclature. Because several other "central" accessory bones exist (e.g., os centrale volare/praescaphoid, os epilunatum/os centrale II, os hypolunatum/os centrale III), it has been proposed that the classic ossicle be more precisely termed os centrale dorsale (synonyms: os centrale carpi, os episcaphoideum) to describe its dorsal position.

Clinical relevance. Accessory carpal bones are usually asymptomatic and of no clinical significance, but a persistent os centrale carpi can occasionally cause dorsal/radial wrist pain, painful clicking or crepitus (especially if mobile), and has rarely been associated with osteonecrosis and secondary degenerative change; symptomatic cases have been treated with excision, including arthroscopic removal. On imaging, it can be mistaken for a scaphoid fracture fragment or, when contused, simulate an acute scaphoid fracture.