Thumb deformities rheumatoid classification

RHEUMATOID THUMB CLASSIFICATION
I	Boutonniere	IA	MP and IP passively correctable
		IB	MP flexion contracture , IP correctable
		IC	MP flexion and IP extension contractures
II	Combination I and III	IP hyperextension, MP flexion CMC subluxation or dislocation
III	Swan	IIIA	Minimal CMC deformity, MP correctable
		IIIB	CMC subluxation, MP correctable
		IIIC	CMC dislocation, MP extension contracture
IV	Gamekeeper's	CMC adduction contracture MP abduction contracture