Unil primary osteoarth of first carpometacarp joint, l hand

This code signifies the presence of primary osteoarthritis affecting the carpometacarpal joint of the thumb on the left hand. This degenerative joint disease is characterized by cartilage breakdown and bone changes, specifically impacting the base of the left thumb.

Apply this code when documentation clearly indicates a diagnosis of primary osteoarthritis localized to the first carpometacarpal joint of the left hand. This is appropriate for patients presenting with pain, stiffness, and functional limitations in the left thumb due to this specific arthritic condition.

• Ensure laterality is explicitly documented as "left hand" for the first carpometacarpal joint.
• Distinguish from secondary osteoarthritis (M18.2-) or other forms of arthritis affecting the hand.
• Confirm the "primary" nature of the osteoarthritis; if a causative factor is identified, a secondary code may be more appropriate.