title: Characterization and Epidemiology of the Carpal Boss Utilizing Computed Tomography.
abstract: BackgroundThe carpal boss is an osseous protuberance occurring variably along the dorsum of the second or third metacarpal base, lacking a standardized definition.AimWe sought to characterize the dorsal second and third carpometacarpal joints in the general population on computed tomography (CT) to better define this variant anatomy.Patients and MethodsA total of 129 wrist CT studies were reviewed. Note was made of the dorsal second/third carpometacarpal osseous anatomy, the presence of regional bursitis or tenosynovitis, and relationship of the extensor carpi radialis brevis attachment to the base of the third metacarpal.ResultsOut of the 129 wrists, 106 (82.2%) demonstrated a dorsal protuberance arising from the base of the third metacarpal, in isolation. Out of the 129 wrists, 14 (10.9%) lacked a dorsal protuberance or nonunited ossicle at the level of the second or third carpometacarpal joint. Out of the 129 wrists, 9 (7%) wrists demonstrated more complex anatomy-8 wrists (6.2%) with a dorsal protuberance at the base of the third metacarpal seen in combination with an adjacent nonunited ossicle and/or dorsal protuberance arising from the capitate, and 1 wrist (0.8%) with an isolated ossicle at the base of the third metacarpal. Of these nine wrists, eight (6.2%) demonstrated arthritis at the resultant pseudoarticulation(s).ConclusionThe majority of wrists demonstrated an isolated protuberance arising from the dorsal base of the third metacarpal, with a small minority with a nonunited ossicle at this level and/or dorsal protuberance of the capitate. The presence of secondary arthritis (8 out of 129 wrists, 6.2%) may reflect a pain generator.Level of EvidenceCross-sectional study; level 2.
authors.affiliation: Department of Radiology, University of Washington, Seattle, Washington.
authors.forename: Christopher
authors.initials: C
authors.lastname: Goiney
authors.affiliation: Department of Radiology, University of Washington, Seattle, Washington.
authors.forename: Jack
authors.initials: J
authors.lastname: Porrino
authors.affiliation: Department of Radiology, University of Washington, Seattle, Washington.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Richardson
authors.affiliation: Department of Radiology, University of Washington, Seattle, Washington.
authors.forename: Hyojeong
authors.initials: H
authors.lastname: Mulcahy
authors.affiliation: Department of Radiology, University of Washington, Seattle, Washington.
authors.forename: Felix S
authors.initials: FS
authors.lastname: Chew
keywords: carpal boss; carpometacarpal joints; computed tomography; os styloideum; wrist