Juvenile Hallux Valgus

Juvenile Hallux Valgus is defined as the onset of hallux valgus deformity before skeletal maturity (usually less than 14-16 years).

• Epidemiology: Strong female preponderance (around 88% in Coughlin's series) and early onset (40% present at age 10 or younger). Distinct from congenital hallux valgus (present at birth) and adult acquired hallux valgus.
• Genetics: High familial penetrance (autosomal dominant with incomplete penetrance). Maternal transmission was recorded in 72% of patients in Coughlin's landmark cohort.
• Pathomechanics: Often related to Metatarsus Primus Varus (medial deviation of the first metatarsal) and a sloping distal articular surface (high DMAA). Ligamentous laxity allows the first ray to drift medially while the toe stays laterally. An elevated DMAA was present in roughly half of juvenile cases and is higher in early-onset and congruent-joint deformities.

Key Deforming Forces:

1. Metatarsus Primus Varus: The primary deformity is the varus of the first metatarsal.
2. DMAA (Distal Metatarsal Articular Angle): This defines the orientation of the cartilage of the metatarsal head relative to the shaft. In juveniles, this is often "dysplastic" (tilted laterally).
3. Congruency: Because the articular surface is tilted, the joint surfaces remain parallel (congruent) despite the valgus appearance.
4. Pes Planus: Pronation of the foot unlocks the midtarsal joint, increasing mobility of the first ray and effectively increasing the IMA.

Growth Plates:

• The first metatarsal physis is PROXIMAL.
• The proximal phalanx physis is PROXIMAL.
• Distal metatarsal osteotomies (Chevron/Mitchell) are performed distal to the physis, but care must be taken not to violate it if still open.

The topic flags the flat/pronated foot again and again - the FLATS mnemonic, the pathophysiology ("pronation unlocks the midtarsal joint, increasing the IMA"), the examination ("correct the heel valgus - does the bunion improve?") and the recurrence-prevention list ("address pes planus") - but never develops the link or its genuine controversy.

The balanced, exam-safe position: a flat, pronated foot is biomechanically plausible as a driver and is worth controlling with orthoses (it offloads the medial column and may reduce a dynamic component), but the evidence that it causes or recurs the deformity is weak - so orthoses relieve symptoms rather than cure the bunion, and a flatfoot should not by itself dictate surgery.

Plain Radiographs (Weightbearing is Mandatory):

• IM Angle (Intermetatarsal): Separation between 1st and 2nd metatarsal shafts.
• HV Angle (Hallux Valgus): Angle between 1st metatarsal and proximal phalanx.
• DMAA: Angle between the articular surface of the head and the shaft axis. Normal is less than 10 degrees. In Juvenile HV, often 20-30 degrees.
• Physeal Status: Are the growth plates open or closed?

Sesamoid View:

• Check for subluxation and rotation of the metatarsal head (Crista erosion is rare in kids).

• Immobilization: Heel-wedge shoe or Cast for 6 weeks.
• Weightbearing: Heel weightbearing allowed usually (if stable osteotomy).
• X-rays: Check at 2 weeks (position) and 6 weeks (union).
• Return to Sport: 3-4 months.

• Satisfaction: Generally lower than adults due to unrealistic cosmetic expectations and stiffness.
• Long Term: Recurrence is the major issue. Many require revision in adulthood.
• Function: Most return to sport, but range of motion is often permanently reduced compared to normal.

Global epidemiology

• Strong female preponderance (around 80-90% across series) and frequent positive family history with maternal transmission. There is no implant registry for juvenile hallux valgus, so evidence rests on retrospective cohorts and small comparative series.

Society guidance, side by side There is no dedicated international guideline for juvenile hallux valgus; recommendations are extrapolated from paediatric forefoot and adult bunion consensus. Common threads across bodies:

Practice variation by resource setting

• High-resource: Weightbearing radiographs, biplanar/double osteotomies with screw fixation, and growth-modulation (hemiepiphysiodesis) for selected young patients.
• Limited-resource: Greater reliance on simple distal osteotomies with Kirschner-wire fixation and percutaneous/minimally invasive (e.g. SERI) techniques where fluoroscopy is available; emphasis on conservative management and footwear given cost and follow-up constraints.

1. Respect the Physis If performing a distal chevron osteotomy in a child with an open physis:

• The cut must remain DISTAL to the physis (which is proximal in the metatarsal, but wait - the metatarsal head physis is PROXIMAL? No, 1st Metatarsal physis is PROXIMAL. The Head physis is in the lesser metatarsals. This is a common exam trap).
• Correction: 1st Metatarsal Physis is PROXIMAL. Lesser Metatarsals are DISTAL.
• So a Distal Chevron is SAFE from the physis.
• However, a PROXIMAL osteotomy (Scarf/Base Wedge) puts the physis at risk.

2. The DMAA Correction How to correct a high DMAA intra-operatively?

• Biplanar Chevron: Instead of just shifting the head lateral, you must tilt it medially (take a wedge out of the medial side of the chevron limb) to reorient the cartilage.
• Reverdin Procedure: A specific wedge osteotomy behind the articular surface to correct DMAA.

3. Modified McBride

• Avoid extensive lateral release in congruent joints. It causes instability.
• Avoid excision of the lateral sesamoid.

• Timing of surgery: Whether to operate before skeletal maturity for severe symptomatic deformity, or wait to reduce recurrence, remains debated. Comparative data (Bard et al, 2024) show recurrence and complications are common regardless of physeal status, supporting a cautious, pain-driven threshold.
• Optimal osteotomy: No single osteotomy is proven superior. Edmonds et al (2015) found double osteotomy corrects all three angles best but overcorrects DMAA most often, while single distal osteotomy is most consistent with fewest complications.
• Role of hemiepiphysiodesis: Growth modulation is low-morbidity but the radiographic correction is modest and it does not address the DMAA; patient selection (young age, adequate remaining growth, predominantly IMA deformity) is critical and outcomes are variable.
• Hypermobility and Lapidus: Whether a hypermobile first ray mandates a first tarsometatarsal fusion in adolescents is unsettled; the procedure risks the physis and is generally deferred to maturity or recurrence.
• Minimally invasive techniques: Percutaneous/SERI and other MIS osteotomies report good short-term results, but long-term comparative evidence in skeletally immature patients is limited.
• DMAA measurement reliability: DMAA has substantial inter-observer variability and rotational sensitivity on radiographs, which complicates both classification and surgical planning.

The Silent Killer of Success The Distal Metatarsal Articular Angle (DMAA) represents the "tilt" of the cartilage on the metatarsal head.

• Normal: less than 10 degrees (Cartilage faces straight).
• Abnormal: greater than 15-20 degrees (Cartilage faces lateral).
• Mechanism: If you act like a carpenter and just straighten the shaft (move the head lateral), but don't change the TILT, the toe will point medial but the joint will be crooked (incongruent). The toe will naturally drift back into valgus to make the joint happy (congruent).
• Solution: You must cut a wedge out of the bone to rotate the articular surface back to neutral (Reverdin or Biplanar Chevron).

Measuring DMAA

1. Draw the axis of the first metatarsal.
2. Draw a line connecting the medial and lateral margins of the articular surface.
3. The angle should be less than 10 degrees. If it is 20-30 degrees, it is dysplastic.

The Historical Answer to DMAA Described by Jacques Reverdin in 1881, long before the Chevron.

• Concept: A closing wedge osteotomy of the metatarsal HEAD (sub-capital).
• Goal: Solely changes the orientation of the articular surface (DMAA). It does NOT correct the IMA.
• Modern Use: Rarely used in isolation. Often combined with a shaft osteotomy (double osteotomy) or modified (Reverdin-Laird) to shift the head as well.
• Technique: Remove a medial wedge of bone just behind the cartilage. Close it down. This rotates the cartilage to face medially.

The double-osteotomy section lists an "Aiken (phalangeal)" osteotomy and the quiz notes the Akin "corrects hallux valgus interphalangeus", but the topic never explains this distinct deformity or why its corrective osteotomy is only ever an adjunct. It is a common reason a great toe still looks bent after the metatarsal has been corrected.

Hallux valgus interphalangeus (HVI) is valgus angulation within the hallux itself - distal to the metatarsophalangeal joint, at the level of the proximal phalanx/interphalangeal joint - rather than at the MTP joint. It is measured by the hallux valgus interphalangeus angle (between the long axes of the proximal and distal phalanges) and usually arises from a trapezoidal/asymmetric proximal phalanx (the distal articular surface is tilted in valgus). It is common in juveniles and adds to the apparent lateral deviation of the toe, but a metatarsal osteotomy does nothing to it.

The Akin osteotomy is the correction for HVI: a medial closing-wedge osteotomy of the proximal phalanx.

The key teaching point is that the Akin is an adjunct, never a stand-alone bunion operation: used alone it cosmetically straightens the toe while leaving the metatarsus primus varus, the high DMAA and any MTP subluxation uncorrected - so the bunion persists and recurs. It is added to a metatarsal procedure to fine-tune the final alignment once the IMA and DMAA have been addressed, and it is particularly useful in juveniles in whom HVI is common.