Thumb hypoplasia Blauth classification

Modified Blauth classification of hypoplastic thumb
I	Minimal shortening and narrowing
II	Thumb-Index web space narrowing Hypoplastic intrinsic thenar muscles Metacarpophalangeal joint instability
III	A	Type II features, plus extrinsic tendon abnormalities and Hypoplastic metacarpal, stable carpometacarpal
	B	Type II features, plus extrinsic tendon abnormalities and Partial metacarpal aplasia, unstable carpometacarpal
IV	Floating thumb
V	Absent thumb