The carpal boss is a hypertrophied bony protuberance on the dorsal surfaces of the base of the second or third metacarpals, near the capitate and trapezoid. It may be bilateral. It can be symptomatic in some instances 5.
Pathology
The condition may represent one or more of:
- degenerative osteophyte formation
- os styloideum (an accessory ossicle of the wrist)
- bony prominence at the base of the second or third metacarpals (which is often called "styloid process")
Pain may be the result of a ganglion, inflamed bursa or extensor tendon slipping over the bony prominence.
Radiographic features
The radiographic appearance of a carpal boss is characteristic, however optimal visualization of the boss may be difficult to obtain due to superimposed bony structures.
CT may show degenerative disease at a pseudoarthrosis, and MRI may show edema related to abnormal motion.
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