Spontaneous rupture of flexor tendons, unspecified forearm

This code signifies a non-traumatic tear of the flexor tendons within an unspecified forearm. This rupture occurs without an external force or injury, often due to underlying degenerative changes or inflammatory processes. It results in impaired ability to flex the fingers or wrist.

Apply this code when documentation clearly states a spontaneous rupture of a flexor tendon in the forearm, and the specific forearm (left or right) is not documented. This code is appropriate when the physician's notes indicate a non-traumatic etiology for the tendon tear.

• Ensure documentation explicitly states "spontaneous" or "non-traumatic" to differentiate from traumatic ruptures.
• Avoid using this code if the laterality (left or right forearm) is specified; instead, use the more specific M66.331 or M66.332.
• Consider co-reporting with codes for underlying conditions like rheumatoid arthritis (M05.-, M06.-) or other inflammatory arthropathies if documented as contributing factors.