ICD-10-CM > M00-M99 > M65-M67 > M66 > M66.2 > M66.23 M66.23 Spontaneous rupture of extensor tendons, forearm Non-Billable/Non-Specific Codes M66.231Spontaneous rupture of extensor tendons, right forearmM66.232Spontaneous rupture of extensor tendons, left forearmM66.239Spontaneous rupture of extensor tendons, unspecified forearm