Table 1.

Trigger thumb classifications according to Sugimoto and Watanabe.

Sugimoto’s Classification [22]
Stage I	Palpable Notta’s nodule without passive or active triggering
Stage II	Triggering occurs with an active extension of the thumb IP joint
Stage III	The thumb cannot be actively extended and triggering occurs with passive extension
Stage IV	The IP joint cannot be extended passively; fixed flexion deformity exists
Watanabe’s Classification [23]
Stage 0	Normal
Stage 1	Locking in flexion or extension/active movement with a trigger
Stage 2	Locking in flexion or extension/Passive movement with a trigger
Stage 3	Locking in flexion or extension