Short thumb Thumb hypoplasia grade 3B 2024-07-06T11:45:23Z Hypoplasia of the thumb grade IIIB A type of developmental undergrowth of the thumb, whereby there are musculotendinous and osseous deficiencies characterized by basal metacarpal aplasia with deficient carpometacarpal (CMC) joint, and absence of metacarpophalangeal (MCP) or interphalangeal (IP) joint.