Surgical treatment of iatrogenic hallux varus.

Iatrogenic hallux varus is a dreaded complication of hallux valgus surgery, consisting in 1st-ray deformity in the form of medial malalignment of the 1st phalanx with respect to the metatarsal axis. Such over-correction results from imbalance between excessive medial capsule retraction or tensioning and excessive lateral laxity or soft-tissue release. There may be loss of medial stability of bone origin due to excessive "exostosectomy" or excessive intermetatarsal angle closure. Following excessive lateral release, the imbalance gradually induces a varus deformity of the 1st phalanx due to traction by the medial muscles: abductor hallucis and medial head of flexor hallucis brevis inserting to the medial sesamoid. The deformity comprises 3 components, of varying importance: medial deviation of the hallux at the 1st metatarsophalangeal joint, supination of the phalanx, and interphalangeal flexion (i.e., claw deformity of the hallux). Treatment strategy is determined by the various clinical and radiological data explaining the postoperative hypercorrection. The clinical analysis is decisive, while radiology contributes more technical factors once the treatment option has been decided on. There are two main options for surgical revision to restore 1st ray propulsion: 1) static or dynamic reconstruction of the ligamentous structures, conserving metatarsophalangeal motion; or 2) metatarsophalangeal and/or interphalangeal fusion. Factors guiding choice are mainly range of motion, and reducibility of the metatarsophalangeal and interphalangeal deformity. We describe the procedures in detail, emphasizing the essential points for success. Joint sparing is to be sought in flexible deformities and young patients. Ligament reconstruction can be anatomic or palliative by tenodesis effect, which makes adjustment difficult. Alongside soft-tissue reconstruction, the metatarsal osteotomy should also be revised if the intermetatarsal angle has been unduly closed. Metatarsophalangeal fusion is the most reliable solution and is unavoidable if the joint is stiff or degenerative; it undoubtedly reduces risk of failure. LEVEL OF EVIDENCE: V, expert opinion.