Table 1.

Stages of PTTI Summarized by Deland.¹⁷

Stage	Deformity	Surgical Treatment
I	No deformity from adult-acquired flatfoot deformity (may have preexisting flatfoot)	Tenosynovectomy, possible tendon transfer, and/or medial slide osteotomy
IIa	Mild/moderate flexible (minimal abduction through talonavicular joint, <30% talonavicular uncoverage)	Tendon transfer, medial slide osteotomy, possible Cotton procedure
IIb	Severe flexible deformity (abduction deformity through talonavicular joint, >30% talonavicular uncoverage)	Tendon transfer, medial slide osteotomy, and possible lateral column lengthening hindfoot fusion (subtalar or talonavicular and calcaneocuboid fusion) Cotton procedure or metatarsal–tarsal fusion performed as needed for elevation of the first ray
III	Fixed deformity (involving the triple-joint complex)	Hindfoot fusion, most commonly triple arthrodesis. Correction requires fusion of all 3 joints
IV	Foot deformity and ankle deformity (lateral talar tilt)	Complete resection of foot deformity, possible deltoid reconstruction. For severe arthritis, perform ankle fusion or total ankle arthroplasty, including correction of foot deformity
IVa	Flexible foot deformity	Foot deformity corrected as with stage IIb
IVb	Fixed foot deformity	Foot deformity corrected as with stage III

Abbreviation: PTTI, posterior tibialis tendon insufficiency.