ICD-10-CM > M00-M99 > M65-M67 > M66 > M66.3 > M66.31 M66.31 Spontaneous rupture of flexor tendons, shoulder Non-Billable/Non-Specific Codes M66.311Spontaneous rupture of flexor tendons, right shoulderM66.312Spontaneous rupture of flexor tendons, left shoulderM66.319Spontaneous rupture of flexor tendons, unspecified shoulder