Spontaneous rupture of extensor tendons, unspecified forearm

This code signifies the non-traumatic tearing of extensor tendons in the forearm, occurring without an external force or injury. It describes a spontaneous rupture affecting the muscles responsible for extending the wrist and fingers, with the specific forearm (right or left) not documented.

Apply this code when documentation clearly indicates an extensor tendon rupture in the forearm that is not attributed to an acute injury or trauma. This diagnosis is supported by findings such as sudden pain, loss of extension function, and imaging (e.g., MRI) confirming a tendon tear without evidence of external force.

• Ensure documentation specifies "spontaneous" or "non-traumatic" to differentiate from traumatic ruptures.
• Avoid using this code if the laterality (right or left forearm) is specified; use the more specific M66.231 or M66.232.
• Consider sequencing this code with any underlying systemic conditions (e.g., rheumatoid arthritis) that may predispose to spontaneous tendon ruptures.