Hallux Varus

Hallux varus is defined as medial deviation of the great toe at the first metatarsophalangeal (MTP) joint, with the hallux angulated medially relative to the long axis of the first metatarsal by more than 10 degrees. [1] In contrast to hallux valgus (bunion), the normal hallux has 5-15 degrees of valgus alignment. [2]

Epidemiology:

• Iatrogenic hallux varus occurs in approximately 5-15% of patients following hallux valgus correction surgery, making it the most common cause in adults. [3]
• Congenital hallux varus is rare, often associated with metatarsus adductus or as part of polydactyly syndromes. [4]
• Traumatic hallux varus follows crush injuries, burns, or medial soft tissue trauma with subsequent contracture.
• Gender distribution: Iatrogenic cases mirror bunion surgery demographics (predominantly female), while congenital cases have equal distribution.

Historical context: The term "hallux varus" was first described in relation to overcorrection following bunion surgery in the mid-20th century. Early bunion operations often involved aggressive medial eminence resection and medial capsulorrhaphy without balancing lateral structures, leading to high rates of iatrogenic varus deformity. Modern bunion surgery emphasizes preservation of sesamoid balance and judicious soft tissue releases. [6]

Etiology Classification

Hallux varus can be classified by etiology into three main categories:

Iatrogenic Causes (Most Common)

The most frequent cause of hallux varus in adults is overcorrection during hallux valgus surgery. [7] Specific technical errors include:

1. Excessive Medial Eminence Resection:

• Removing too much medial bone eliminates the medial buttress.
• The unopposed pull of the abductor hallucis and extensor hallucis longus (EHL) pulls the toe medially.
• Risk increases if resection extends beyond the sagittal sulcus of the metatarsal head.

2. Overtightening of Medial Capsule:

• Aggressive medial capsulorrhaphy or plication creates excessive medial tension.
• Combined with inadequate lateral release, this imbalances soft tissue forces.
• Common in older McBride-type procedures.

3. Fibular (Lateral) Sesamoidectomy:

• The fibular sesamoid acts as a lateral buttress.
• Its removal eliminates lateral support and allows medial deviation.
• Risk is higher if combined with other medial-sided procedures.

4. Disruption of Lateral Structures:

• Injury to the lateral capsule, lateral collateral ligament, or adductor hallucis during exposure.
• Overzealous lateral soft tissue release in an attempt to correct severe bunion.

5. Overcorrection with Osteotomy:

• Excessive varus angulation with distal metatarsal osteotomy (Chevron, scarf).
• Malunion in varus after proximal osteotomy.

Congenital Causes

Congenital hallux varus is rare and typically presents in infancy or early childhood. [8] Causes include:

• Metatarsus adductus: The first metatarsal is deviated medially, creating relative hallux varus.
• Delta (trapezoid) phalanx: Abnormal wedge-shaped proximal phalanx drives progressive varus angulation.
• Polydactyly remnants: Incomplete resection or scarring after polydactyly excision.
• Congenital contracture: Tight abductor hallucis or medial capsular structures.

Most congenital cases are flexible and may improve with growth. Rigid cases or those with structural bone abnormalities require surgical correction.

Traumatic Causes

Post-traumatic hallux varus results from:

• Soft tissue contracture: Burns, crush injuries, or lacerations causing medial scar contracture.
• Disruption of lateral stabilizers: Rupture of lateral collateral ligament or adductor hallucis tendon.
• Malunion: Fractures of the first metatarsal or proximal phalanx healing in varus.
• Loss of fibular sesamoid: Traumatic excision or loss of sesamoid in severe injuries.

Soft Tissue Imbalance

The hallux is maintained in physiologic valgus alignment by a balance of forces:

Medial (varus-producing) forces:

• Abductor hallucis (inserts on medial base of proximal phalanx)
• Extensor hallucis longus (EHL) when toe is in varus position
• Medial capsule and collateral ligament

Lateral (valgus-producing) forces:

• Adductor hallucis (inserts on lateral base and fibular sesamoid)
• Flexor hallucis brevis (via both sesamoids)
• Lateral capsule and collateral ligament
• Fibular sesamoid acting as lateral buttress

In flexible hallux varus, the medial forces overpower the lateral forces, but the joint remains mobile and passively correctable. The EHL tendon, which normally runs in a straight line, now has a medial bowstring effect, acting as a dynamic deforming force. [9]

In rigid hallux varus, chronic imbalance leads to capsular contracture, adaptive shortening of medial structures, and eventual joint stiffness or arthrosis. The deformity becomes fixed and non-correctable.

History

Key elements to elicit:

Chief complaint:

• Cosmetic concern (visible medial deviation)
• Difficulty with shoe wear (toe rubs on adjacent toe or medial shoe)
• Pain at MTP joint (especially if arthritic)
• Transfer metatarsalgia (pain under lesser metatarsal heads due to altered loading)
• Functional limitation (difficulty with push-off, sports)

History of present illness:

• Duration of deformity (congenital vs acquired)
• Progressive vs stable
• Inciting event (surgery, trauma, or insidious onset)
• Previous treatments attempted

Past surgical history:

• Prior bunion surgery (timing, procedure type, complications)
• Revision surgeries
• Other foot procedures

Associated symptoms:

• Numbness or tingling (nerve injury from prior surgery)
• Stiffness (suggests rigid deformity)
• Lesser toe pain (transfer metatarsalgia)

Physical Examination

Inspection:

• Standing alignment: Assess varus angle of hallux relative to first metatarsal
• Skin condition: Scarring from prior surgery or trauma, calluses on medial hallux or lateral lesser toes
• Adjacent toes: Crossover or crowding of second toe
• Hindfoot alignment: Assess for associated pes planus or cavus

Palpation:

• First MTP joint: Tenderness, effusion, crepitus (suggests arthritis)
• Medial eminence area: Prominence or deficiency (over-resection)
• Sesamoids: Palpate plantar aspect for tenderness, assess position
• Lesser metatarsal heads: Tenderness suggests transfer metatarsalgia

Range of Motion:

• MTP joint: Measure dorsiflexion and plantarflexion (normal 70-80° dorsiflexion, 20-30° plantarflexion)
• Interphalangeal (IP) joint: Assess flexion/extension
• Pain with motion: Crepitus or pain indicates arthritis

Special Tests:

Neurovascular examination:

• Pulses (dorsalis pedis, posterior tibial)
• Sensation (distribution of deep peroneal, medial plantar, saphenous nerves)
• Motor function (EHL, FHL, intrinsics)

Gait assessment:

• Stance phase: Assess weight distribution, tendency to offload hallux
• Push-off: Observe for diminished hallux contribution, lateral forefoot loading

Functional Impact

Hallux varus impairs forefoot mechanics:

• Reduced push-off power: The hallux generates up to 85% of push-off force in normal gait. [10]
• Transfer metatarsalgia: Load shifts from first to lesser metatarsal heads, causing pain and calluses.
• Gait instability: Loss of medial tripod support reduces balance.
• Shoe wear difficulty: Varus toe crowds second toe and creates abnormal pressure points.

Radiographic Assessment

Standard radiographs are essential for diagnosis and surgical planning:

Weight-bearing AP foot:

• Hallux varus angle: Measure angle between long axis of first metatarsal and proximal phalanx. Greater than 10° medial deviation confirms hallux varus. [11]
• First metatarsal position: Assess metatarsus primus varus (increased intermetatarsal angle may predispose to recurrence).
• Sesamoid position: Normally, sesamoids are centered beneath the metatarsal head. In varus, they shift laterally. Assess for absent fibular sesamoid.
• Joint space: Narrowing, osteophytes, or subchondral sclerosis indicate degenerative joint disease.
• Previous surgery evidence: Hardware, bone resection patterns.

Weight-bearing lateral foot:

• First MTP joint congruency: Assess for subluxation.
• Dorsal osteophytes: May limit dorsiflexion.
• Metatarsal declination: First ray position relative to lesser metatarsals.

Oblique foot:

• Better visualization of sesamoids and first MTP joint articular surfaces.

Advanced Imaging

MRI:

• Rarely indicated for routine cases.
• Useful for:
  • Assessing integrity of lateral soft tissue structures (adductor hallucis, lateral collateral ligament) in traumatic cases.
  • Identifying occult osteonecrosis of sesamoids or metatarsal head.
  • Pre-operative planning for complex revisions.

CT scan:

• Rarely needed.
• Can assess bone stock and prior screw tracts in multiply-operated feet.
• Useful for three-dimensional planning in severe deformities.

Classification Systems

There is no universally accepted classification for hallux varus. However, categorization by etiology (congenital, iatrogenic, traumatic) and flexibility (flexible vs rigid) is clinically most useful.

📊 Management Algorithm

Click to expand

Non-Operative Management

Indications:

• Asymptomatic or minimally symptomatic deformity
• Congenital cases in young children (high rate of spontaneous improvement)
• Medical comorbidities precluding surgery
• Patient preference

Treatment options:

• Observation: Many congenital cases improve with growth.
• Shoe modifications: Wide toe box shoes, soft uppers, custom orthotics to accommodate deformity.
• Toe spacers: Soft silicone spacers between hallux and second toe to provide lateral corrective force (limited efficacy).
• Taping/splinting: Dynamic splinting to hold toe in corrected position (may slow progression in flexible cases).
• Activity modification: Avoid aggravating activities.

Limitations: Non-operative treatment does not correct the deformity but may reduce symptoms. Flexible deformities may progress to rigid over time despite conservative measures. [12]

Operative Management - Decision Algorithm

Surgical Options Overview

Complications of Hallux Varus Itself (Untreated)

• Transfer metatarsalgia: Lateral shift of weight-bearing load causes pain under second and third metatarsal heads. [18]
• Progression to rigidity: Flexible deformities become rigid over time due to capsular contracture.
• Arthritis: Abnormal joint mechanics accelerate degenerative changes.
• Shoe wear difficulty: Cosmetic and functional impairment.
• Gait dysfunction: Reduced push-off power, compensatory gait patterns.

Surgical Complications

General complications:

• Infection: 1-3% with standard precautions. Higher risk in revision surgery or compromised soft tissues.
• Wound healing problems: Dorsal foot has thin skin and limited vascularity. Risk increases with multiple prior surgeries or smoking.
• Nerve injury: Dorsal cutaneous nerves at risk during incision. Causes numbness or neuroma.
• Deep vein thrombosis/pulmonary embolism: Rare in foot surgery but consider prophylaxis in high-risk patients.

Procedure-specific complications:

EHL Transfer:

• Recurrence of varus deformity: 10-20% if inadequate transfer tension, poor patient selection (rigid deformity), or failure to address all deforming forces. [19]
• Loss of IP extension strength: The EHL normally extends the IP joint. After transfer, IP extension is weaker (though extensor hood mechanism preserves some function). Usually well-tolerated.
• Overcorrection to valgus: Rare. Occurs if transfer is too tight or combined procedures create excessive valgus force.
• Tendon pull-out or failure: If fixation is inadequate. Use strong suture technique and bone tunnel or solid anchor.

Arthrodesis:

• Non-union: 5-10% overall. Higher with smoking, poor bone quality, inadequate fixation, or infection. [20]
• Malunion: Fusion in incorrect position (excessive or insufficient dorsiflexion, persistent varus, rotation). Requires revision arthrodesis or osteotomy.
• Hardware complications: Prominent screws or plates causing irritation, requiring removal.
• Transfer metatarsalgia: Loss of MTP motion shifts load to lesser metatarsals. Occurs in 10-20% long-term.
• Hallux IP joint arthritis: Increased stress on IP joint over time due to loss of MTP motion.
• Shortening: Excessive bone resection during joint preparation can shorten hallux.

Reverse Akin Osteotomy:

• Non-union: Rare in metaphyseal bone.
• Malunion: Incorrect wedge size causing under- or overcorrection.
• Fracture: Proximal phalanx fracture if osteopenic bone or trauma.

Prevention Strategies

Preventing iatrogenic hallux varus (during bunion surgery):

1. Limit medial eminence resection: Stay within sagittal sulcus.
2. Preserve fibular sesamoid: Avoid routine sesamoidectomy.
3. Balance soft tissue releases: Proportional medial and lateral releases.
4. Avoid overtightening medial capsule: Plication should restore anatomy, not overcorrect.
5. Assess intraoperative sesamoid position: Sesamoids should be centered under metatarsal head.
6. Aim for slight valgus: Target 10-15° valgus, not neutral.

Preventing recurrence after hallux varus correction:

1. Correct patient selection: Flexible cases for soft tissue procedures, rigid for arthrodesis.
2. Address all deforming forces: EHL transfer alone may fail if medial contractures not released.
3. Adequate fixation: Strong suture technique for tendon transfers, rigid fixation for osteotomies.
4. Post-operative protection: Maintain correction with splinting during healing phase.

Immediate Post-operative Period (0-2 weeks)

Dressing and immobilization:

• Bulky compressive dressing with gauze between hallux and second toe to maintain corrected position.
• Posterior splint or CAM boot for protection.
• Elevate foot above heart level to reduce swelling.

Weight-bearing:

• Non-weight-bearing for soft tissue procedures (EHL transfer, releases) for first 2 weeks.
• Non-weight-bearing for arthrodesis if screw fixation; protected weight-bearing may be allowed with rigid plate fixation (surgeon preference).

Wound care:

• Keep dressing clean and dry.
• First dressing change at 10-14 days with suture removal.

Pain management:

• Multimodal analgesia: acetaminophen, NSAIDs (if not contraindicated for bone healing), opioids as needed for first few days.

Early Rehabilitation Phase (2-6 weeks)

Soft tissue procedures (EHL transfer):

• Week 2-6: Transition to protected weight-bearing in stiff-soled shoe or CAM boot.
• Continue toe spacer (gauze or silicone) between hallux and second toe.
• Begin gentle IP joint ROM exercises at 2 weeks to prevent stiffness (EHL still functions to IP via extensor hood).
• Avoid forceful MTP motion until 6 weeks (allow soft tissues to heal).

Arthrodesis:

• Week 2-6: Protected weight-bearing in CAM boot or post-op shoe.
• No MTP joint motion (fusion is the goal).
• Radiographs at 6 weeks to assess early healing.

Late Rehabilitation Phase (6-12 weeks)

Soft tissue procedures:

• Week 6+: Progressive return to normal shoe wear.
• Begin active MTP ROM exercises (if not arthrodesis).
• Strengthening exercises for intrinsic muscles.
• Return to athletic activities at 10-12 weeks if healing is adequate.

Arthrodesis:

• Week 6-12: Continue protected weight-bearing until radiographic union (typically 8-12 weeks).
• Once fused, transition to normal shoe wear.
• Return to full activities at 12-16 weeks.

Long-term Follow-up

• Radiographs: At 6 weeks, 12 weeks, and 6 months to assess alignment, hardware, and union (for arthrodesis).
• Functional assessment: Gait analysis, shoe wear patterns, pain levels, patient satisfaction.
• Monitor for complications: Recurrence, transfer metatarsalgia, hardware prominence.

Clinical Management: Hallux varus is an uncommon condition in Australia, most frequently seen as a complication of hallux valgus surgery. Management is typically performed by foot and ankle orthopaedic surgeons with fellowship training.

Conservative Management: Initial conservative treatment includes toe spacers, strapping, and footwear modification. Podiatry input through Enhanced Primary Care (EPC) referrals provides custom orthotic devices and ongoing monitoring.

Surgical Care: Surgical correction is performed as day surgery or short-stay procedures. Complex reconstructive cases may require tertiary centre referral to surgeons with specific forefoot reconstruction expertise.

Prevention: Australian orthopaedic training emphasises prevention of iatrogenic hallux varus through appropriate technique selection, preservation of the lateral structures, and meticulous surgical planning for hallux valgus correction.

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