Thumb Hypoplasia: Modified Blauth Classification chart form

__I. Minimal shortening and narrowing

__II. Thumb-Index web space narrowing

__Hypoplastic intrinsic thenar muscles

__Metacarpophalangeal joint instability

__III. Type II features, plus extrinsic tendon abnormalities and:

__IIIA. Hypoplastic metacarpal, stable carpometacarpal

__IIIB. Partial metacarpal aplasia, unstable carpometacarpal

__IV. Floating thumb

__V. Absent thumb