SCIENTIFIC ARTICLE
Incidence of Carpal Boss and Osseous Coalition:
An Anatomic Study
Amir M. Alemohammad, MD, Koji Nakamura, MD, Maged El-Sheneway, MD, Steven F. Viegas, MD
Purpose To determine the incidence of a clinically evident carpal boss (bony prominence on
the dorsal aspect of the second and/or third carpometacarpal joint) and by means of
dissection to determine the incidence of osseous coalitions and any abnormality or absence
of associated ligament anatomy in the second through fifth carpometacarpal joints in a
cadaver population.
Methods The area of the second through fifth carpometacarpal joints was dissected in 202
cadaver wrists.
Results Thirty-nine of the wrists had a bony prominence and partial osseous coalition
between 2 or more of the capitate, trapezoid, second metacarpal, and third metacarpal bones.
When an osseous coalition was present it was incomplete, located at the dorsal aspect of the
joint, and there was an absence of the normal dorsal ligaments at that joint. Ten of the 87
pairs of wrists were found to have bilateral carpal bosses with partial dorsal osseous
coalition. The most common location of the osseous partial coalition was between the second
metacarpal and the trapezoid. There were no osseous coalitions or absence of the normal
dorsal ligaments at the fourth and/or fifth carpometacarpal joints.
Conclusions This study showed that there was a high percentage of partial osseous coali-
tions with an associated prominence of the skeletal anatomy in the general cadaver popu-
lation. The etiology of the carpal boss remains unclear. (J Hand Surg 2009;34A:1 –6.
Copyright © 2009 by the American Society for Surgery of the Hand. All rights reserved.)
Key words Carpal boss, coalition, wrist anomaly.
T
HE CARPAL BOSS is a bony prominence on the
dorsum of the hand at the third and/or second
carpometacarpal (CMC) joint.
1
The etiology
has been speculatively suggested to be traumatic or
degenerative. Previous reports have suggested that the
cause of a carpal boss is trauma, minor stress, instabil-
ity, ganglion, and/or an accessory ossicle and that
symptoms can be caused by arthritis and/or extensor
tendon subluxation over the bony prominence.
2–10
Na-
kamura et al. raised the question of whether the carpal boss
is in fact a congenital carpal coalition.
11
Nevertheless,
the etiology of the carpal boss is still unclear.
Despite the numerous proposed etiologies and varied
treatment recommendations, there has not been a de-
tailed study to determine the incidence of carpal bossing
and/or osseous coalitions in the area of the second
and/or third CMC joints in a cadaver population. This
study was performed to investigate the location and
incidence of any bony prominence that could be clas-
sified as a carpal boss and the presence and incidence of
any osseous coalitions between 2 or more of the second
metacarpal, third metacarpal, capitate, and trapezoid
and the presence or absence of the dorsal CMC liga-
ments
11
in cadaver wrists.
FromAriaPrivate Hospital, Ahwaz, Iran; Department of Hand Surgery, St. Mariana Univer-
sity, Tokyo, Japan; Department of Orthopaedic Surgery, Mansoura University, Mansoura,
Egypt; and the Department of Orthopaedic Surgery and Rehabilitation, The University of
Texas Medical Branch, Galveston, TX.
Received for publication May 16, 2008; accepted in revised form August 29, 2008.
No benefits in any form have been received or will be received related directly or indirectly to the
subject of this article.
Corresponding author: Steven F. Viegas, MD, Department of Orthopaedic Surgery and Rehabil-
itation, The University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-0165;
e-mail: sviegas@utmb.edu.
0363-5023/09/34A01-0001$36.00/0
doi:10.1016/j.jhsa.2008.08.025
© ASSH Published by Elsevier, Inc. All rights reserved. 1