Question: I have an operative report for an excision of "bossing of the dorsal aspect of the navicular." What is this, and what is the diagnostic code? Mississippi Subscriber Answer: A carpal boss is a round, bony prominence that is visible under the skin. They are sometimes referred to as "kissing osteophytes," an osteophyte at the base of the metacarpal and one on the abutting carpal bone. A carpal boss becomes a problem by causing chronic extensor tendon irritation when the tendon flips back and forth over the top of the boss. The American Society for Surgery of the Hand advises reporting this condition with 726.91 (Exostosis of unspecified site).