Hallux Valgus Correction - Comprehensive Decision-Making Guide (Chevron, Scarf, Lapidus)

Indication. Symptomatic hallux valgus - pain over the medial eminence (bunion), over the prominent first MTP joint, and often under the second metatarsal head (transfer metatarsalgia) - that has failed a minimum of three to six months of conservative care: wide toe-box shoes, accommodative orthotics, activity modification and NSAIDs. Surgery is elective and is offered for pain and functional limitation, not cosmesis alone. The whole decision turns on three things, assessed before you book a list. 1. Deformity severity on a weight-bearing AP radiograph - measure the HVA, IMA and DMAA. Non-weight-bearing films underestimate the deformity and lead to the wrong procedure. 2. First TMT mobility - assessed clinically (and, if equivocal, on a stress lateral view). Greater than 9 mm of dorsoplantar translation is abnormal. 3. Patient factors - age, activity level, bone quality, and tolerance of the recovery, since a Lapidus is roughly twice as long as a distal osteotomy. Procedure selection. The three operations are not interchangeable - they correct at different levels of the ray and suit different severities.

Assess first TMT mobility - the single most missed factor. Stabilise the hindfoot and midfoot with one hand, grasp the first metatarsal head with the other, and translate it dorsally and plantarly. Normal is less than 5 mm; 5-9 mm is borderline; greater than 9 mm is abnormal and pushes toward a Lapidus regardless of the IMA - a distal osteotomy on a hypermobile ray drifts back into varus and recurs. Modern caveat (high-yield). First-ray "hypermobility" is now a supportive rather than absolute Lapidus indication. Coughlin and Jones showed mobility does not correlate with deformity magnitude, and much apparent instability reduces once the IMA is corrected. In a viva, present hypermobility as one factor alongside a severe IMA, metatarsus primus varus, recurrence and TMT arthritis - not as a stand-alone mandate. Additional factors that favour a Lapidus: metatarsus primus varus (a structural deformity at the TMT level), revision after a failed Chevron or Scarf, a young active patient wanting definitive correction, MTP joint varus with lateral joint-space widening, and established TMT arthritis. Sesamoid position drives the lateral release. Reduced sesamoids under the metatarsal head are the shared correction endpoint of all three procedures. Grade 3-4 lateral subluxation that persists after bony correction needs a lateral release (see the grading in Background). Consent specifically for recurrence (roughly 1 in 20 across techniques), transfer metatarsalgia (10-20 percent), hallux varus from overcorrection (2-5 percent), dorsomedial numbness or a painful neuroma (5-10 percent), stiffness, and - for a Lapidus - nonunion (5 percent with a plate, 10-15 percent with screws alone) and a recovery roughly twice as long as a distal osteotomy. Setup. Supine with the foot at the end of the table, a small bump under the ipsilateral hip to externally rotate the limb, ankle block or general anaesthetic, and an ankle or thigh tourniquet at 250 mmHg. Mark the first MTP joint line, the metatarsal shaft (for a Scarf), the TMT joint (for a Lapidus), and the course of the dorsomedial cutaneous nerve.

The goal is the same for all three procedures: reposition the first metatarsal - and through it the sesamoids - under the hallux, restore a plantigrade first ray, and balance the soft tissues so the correction holds. They differ in where along the ray the bony correction is made: at the head (Chevron), in the shaft (Scarf), or at the TMT joint (Lapidus). The exposure and the early steps are shared; the osteotomy and fixation are procedure-specific.

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Rehabilitation | Procedure | 0-2 weeks | 2-6 weeks | 6-12 weeks | 3-6 months | |-----------|-----------|-----------|------------|------------| | Chevron / Scarf | Bunion dressing; heel weight-bearing in a stiff-soled shoe | Sutures out at 10-14 days; start MTP ROM at 2-3 weeks; continue heel weight-bearing | Transition to supportive shoes at 6-8 weeks | Normal shoes 8-12 weeks; full activity at 3-4 months | | Lapidus | Non-weight-bearing cast or CAM boot | Non-weight-bearing; sutures out; 6-week X-ray | Protected weight-bearing boot if healing | Supportive shoes at 12 weeks; full activity at 4-6 months; union at 3-4 months | Serial radiographs at 6 weeks, 12 weeks and 6 months. Across all procedures avoid high heels for 6 months and NSAIDs for 3 months (they impair healing); smoking cessation is mandatory, especially for a Lapidus, where it triples the nonunion risk. Complications

Lower-frequency complications include wound problems (5-10 percent, higher in smokers, diabetics and revision), hardware prominence (10-15 percent with non-headless screws, 5 percent headless, 5-10 percent with Lapidus plates - removed after union), infection (1-2 percent primary, higher in revision) and complex regional pain syndrome (1-2 percent).

Epidemiology. Hallux valgus is the commonest forefoot deformity, with a strong female predominance and a peak in the fifth to seventh decades. Coughlin and Jones, in a prospective series of 122 feet with moderate-to-severe deformity, found 83 percent had a positive family history and 84 percent were bilateral. First-ray mobility (mean 7.2 mm by the Klae device) did not correlate with deformity magnitude - the finding that reframed "hypermobility" as a supportive rather than absolute indication. Pathoanatomy. The deformity is a progressive lateral deviation of the hallux with medial deviation of the first metatarsal (metatarsus primus varus). The sesamoid apparatus, anchored to the second metatarsal by the transverse metatarsal ligament, is left lateral to the first metatarsal head; the adductor hallucis pulls the hallux further into valgus and the medial capsule attenuates. The result is a bunion (the prominent medial eminence and bursa), a pronated great toe, and overload of the lesser rays (transfer metatarsalgia). Radiographic classification. Everything about procedure selection flows from three angles and the sesamoid position, all measured on a weight-bearing AP film.

Guidelines, registries and global practice. | Theme | Global consensus / variation | |-------|------------------------------| | Imaging | Weight-bearing AP + lateral mandatory worldwide (AOFAS, EFAS, BOFAS, AO). Weight-bearing CT increasingly quantifies rotation and sesamoid position but is not yet standard of care. | | Procedure family | Severity-stratified: distal osteotomy (chevron) for mild-moderate, diaphyseal (scarf) for moderate-severe, first TMT fusion (Lapidus) for severe, unstable or recurrent deformity - concordant across AOFAS, EFAS and AO. | | Hypermobility | First-ray instability is a supportive, not absolute, Lapidus indication (Coughlin/Jones); many "hypermobile" rays reduce once the IMA is corrected. | | Lateral release | No longer routine; reserved for sesamoids unreduced after bony correction (lowers hallux-varus and AVN risk). | | MIS | Third/fourth-generation minimally invasive chevron (MICA/PECA) is gaining ground in Europe and the UK with comparable correction; it has not yet displaced open techniques globally. | | Outcomes data | Pooled recurrence is about 5 percent (Barg et al, JBJS 2018); there is no large national bunion registry equivalent to the arthroplasty registries, so the evidence base is RCT and case-series driven. | Key evidence. Barg and colleagues' systematic review of 229 studies (JBJS 2018) set the global counselling benchmark: recurrent deformity in 4.9 percent, dissatisfaction in 10.6 percent, persistent first MTP pain in only 1.5 percent - so recurrence, not pain or AVN, is the headline risk, and correct procedure selection by severity is the central point. Mahadevan and colleagues' randomised trial (Foot and Ankle Surgery, 2015/2016) showed a modified long-plantar-limb chevron rivalled the Scarf for IMA correction in moderate deformity, challenging rigid angle cut-offs. Cottom and Vora (JFAS 2013) showed a plantar interfragmentary screw plus medial locking plate gave a 2 percent nonunion rate and supported early weight-bearing - the rationale for the contemporary plate-plus-lag-screw Lapidus construct. The classic technique descriptions remain Austin and Leventen (chevron, 1981), Weil (scarf, 2000) and Lapidus (1931-1959); Coetzee (2003) catalogued the Scarf's "dark side" complications.