M18.5Other unilateral secondary osteoarthritis of first carpometacarpal joint

M18.5 is the ICD-10-CM diagnosis code for other unilateral secondary osteoarthritis of first carpometacarpal joint. It belongs to category M18 (osteoarthritis of first carpometacarpal joint), block M15-M19 (osteoarthritis) and chapter 13 (diseases of the musculoskeletal system and connective tissue). It is a header code, so it can't be reported by itself; one of its 3 subcodes must be used instead.

Within M18, choose M18.5 (Other unilateral secondary osteoarthritis of first carpometacarpal joint) only when documentation doesn't support a more specific option: bilateral primary osteoarthritis of first carpometacarpal joints (M18.0), unilateral primary osteoarthritis of first carpometacarpal joint (M18.1), bilateral post-traumatic osteoarthritis of first carpometacarpal joints (M18.2), unilateral post-traumatic osteoarthritis of first carpometacarpal joint (M18.3), other bilateral secondary osteoarthritis of first carpometacarpal joints (M18.4) and unspecified (M18.9).

To report this condition, pick the subcode that matches the documentation: M18.50 (unspecified hand), M18.51 (right hand) and M18.52 (left hand).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.