Os Carpi Centrale

The os carpi centrale (os centrale) is an uncommon accessory carpal bone that is located dorsally between the first and second carpal rows and articulates with the scaphoid, capitate, and trapezoid, but not with the trapezium. It can have the appearance of a segment cut out of the scaphoid that has ossified independently of it. The os carpi centrale is usually round and dense, and lacks an internal trabecular architecture. It can be bilateral and duplicated.

When the os carpi centrale is unossified, it is radiographically occult and can present as a large gap between the distal scaphoid and a groove in the capitate. On the other extreme, the os carpi centrale can fuse with the adjacent scaphoid, capitate, or trapezoid

A similar bone is found in the writs of of the Orangutan, but the os centrale in these primates articulates with the trapezium.

Because of its location, it may be confused with a scaphoid fracture. Patients are usually asymptomatic; however, some may present with painful clicking or pain from osteonecrosis.

The main differential considerations are bipartite scaphoid, scaphoid fracture, and an unfused scaphoid ossification center. Dysplasia epiphysealis hemimelica and congenital hypothyroidism can also be considered but the appearance of these conditions is usually distinct.

References

• Abascal F, Cerezal L, del Piñal F, García-Valtuille R, García-Valtuille A, Canga A, Torcida J. Unilateral osteonecrosis in a patient with bilateral os centrale carpi: imaging findings. Skeletal Radiol. 2001 Nov;30(11):643-7.
• Freyschmidt J, Brossmann J, Wiens J, Sternberg A. Carpus-Scaphoid. In Freyschmidt's Köhler and Zimmer: Borderlands of normal and early pathologic findings in skeletal radiography. Fifth revised edition. Thieme (2003). Pp 155-157.
• Turner W. Some Variations in the Bones of the Human Carpus. J Anat Physiol. 1883 Jan;17(Pt 2):244-9.