ICD-10-CM > M00-M99 > M65-M67 > M66 > M66.2 > M66.22 M66.22 Spontaneous rupture of extensor tendons, upper arm Non-Billable/Non-Specific Codes M66.221Spontaneous rupture of extensor tendons, right upper armM66.222Spontaneous rupture of extensor tendons, left upper armM66.229Spontaneous rupture of extensor tendons, unspecified upper arm