Flexible Flatfoot (Pediatric)

Pes Planus: Flat foot. Technically defined as valgus of the hindfoot, abduction of the forefoot, and depression of the medial longitudinal arch.

Pes Planovalgus: Emphasizes the valgus component of the heel.

Flexible: The deformity is reducible. The joints (Subtalar, TN, CC) are mobile.

Calcaneal Lengthening (Evans): A lateral column lengthening procedure. The "Workhorse" for severe flatfoot correction.

Arthroereisis: "To prop up". Surgical limitation of joint motion (without fusion) using an implant.

Flexible Flatfoot (Pes Planus) is the most common reason for referral to a pediatric orthopaedic clinic.

• Definition: Loss of the medial longitudinal arch that is present only during weight bearing, and resolves when non-weight bearing or during the Windlass maneuver.
• Natural History:
  • The arch is naturally flat in neonates due to a fat pad and laxity.
  • As the neuromuscular system matures, the arch develops.
  • Morley (1964) showed 97% of 2-year-olds are flat, but only 4% of 10-year-olds.
  • Therefore, spontaneous resolution is the rule.

Etiology:

• Ligamentous Laxity: Generalized (Ehlers-Danlos, Marfan, Down Syndrome) or isolated familial laxity.
• Obesity: Increases load on the arch.
• W-sitting: Associated with femoral anteversion and external tibial torsion ("Miserable Malalignment").

The Keystone: The Talonavicular joint is the keystone of the arch. In flatfoot, the talus head uncovers medially and plantarward (Peritalar subluxation).

Pathomechanics:

• Hindfoot Valgus: The calcaneus goes into valgus.
• Forefoot Abduction: The midfoot breaks, and forefoot abducts relative to hindfoot.
• Achilles Tension: With the hindfoot in valgus, the Achilles tendon becomes a DEFORMING force (it is now lateral to the axis of the subtalar joint), acting as an evertor.
• Medial Column: The Spring Ligament (Calcaneonavicular) and Tibialis Posterior stretch out.
  • Spring Ligament:
    • Superomedial band: The most important stabilizer.
    • Inferoplantar band: Supports the head of talus.
  • Tibialis Posterior:
    • Primary dynamic stabilizer of the arch.
    • Inserts on the Navicular tuberosity + slips to cuneiforms/cuboid/metatarsals (2,3,4).
    • Failure leads to flatfoot (Adult Acquired), but in kids, it's usually laxity not rupture.
• Lateral Column: Theoretically shortened relative to the medial column in flatfoot (hence lengthening corrects it).

Gait Cycle Mechanics:

• Heel Strike: Calcaneus everts (unlocking subtalar joint) for shock absorption.
• Mid-Stance: Subtalar joint inverts (locking MTJ) to create a rigid lever for push-off.
• In Flatfoot, the foot remains everted and unlocked throughout stance, leading to inefficient gait.

The Windlass Mechanism:

• Extending the Hallux pulls the Plantar Aponeurosis.
• This shortens the distance between calcaneus and metatarsal heads.
• This elevates the arch and inverts the hindfoot.
• In Flexible Flatfoot, this mechanism is INTACT.
• In Rigid Flatfoot, it is blocked.

X-rays (Weight Bearing): Usually not needed for physiologic flatfoot, but indicated for pain or rigidity.

• Views: AP and Lateral Weight Bearing. Harris (Saltzman) view for hindfoot alignment.

CT/MRI:

• Only if suspecting coalition (CT) or tendon pathology (MRI). Not routine.

The key clinical task is separating benign physiological flexible flatfoot from the pathological mimics that share a "flat" appearance. Flexibility (arch restores on toe-raise/Jack's test) and painlessness are the great discriminators.

Surgery aims to realign the foot. It is often a "A la carte" menu depending on the deformity.

Surgical Outcomes (Evans):

• Pain Relief: Reported as 90% good/excellent in long term studies (Mosca).
• Deformity Correction: Excellent restoration of arch and alignment.
• Complications:
  • Calcaneocuboid OA: Due to increased joint pressure from the graft. Often asymptomatic.
  • Lateral column pain: Hardware prominence or graft non-union.
  • Under-correction: If the Equinus is not addressed (TAL).

Natural History:

• Asymptomatic flexible flatfoot does NOT lead to disability in adulthood.
• It is a variant of normal.

Unresolved questions for higher-level study:

• Lack of validated, disease-specific paediatric patient-reported outcome measures hampers comparison across procedures.
• The relative contribution of each "a la carte" component (lengthening vs medial column vs soft tissue vs gastrocnemius recession) is poorly isolated because procedures are usually combined.
• Optimal management of the borderline symptomatic adolescent (mild pain, very flexible foot) remains opinion-based.

Evidence below verified against PubMed. DOIs link to the primary record where one exists.

Global Epidemiology:

• One of the commonest reasons for paediatric orthopaedic referral worldwide; the great majority are physiological.
• Prevalence is strongly age-dependent: ~44% at ages 3-6 falling to ~24% by age 6 (Pfeiffer, Pediatrics 2006), and only a few percent of 10-year-olds retain a flat arch as the medial arch matures through the first decade.
• Higher prevalence with male sex, overweight/obesity, and generalised ligamentous laxity; pathological (rigid) flatfoot accounts for under 1%.
• Often presents as "grandmother concern" — a normal-looking variant raised by an anxious family member rather than a symptomatic child.

Side-by-Side Society Guidance:

The major point of genuine international divergence is subtalar arthroereisis: relatively popular in parts of continental Europe, but viewed with caution in the UK, North America and Australasia given low-level evidence and removal rates of roughly 7-19% (Metcalfe, Foot Ankle Int 2011).

Registry Note:

• There is no dedicated implant registry for paediatric flatfoot. Arthroereisis "spacers" are device implants, so where national implant or device registries exist (e.g. orthopaedic device tracking schemes), outcomes and removal events should be captured the same way as any implant; the absence of long-term registry data is itself a reason for caution.

High-Resource vs Limited-Resource Practice:

• High-resource settings: Risk is over-investigation and over-treatment (unnecessary X-rays, custom orthoses, premature surgery) for what is usually a normal variant; ethical counselling — "we treat the child, not the radiograph" — is the priority.
• Limited-resource settings: Custom orthoses and elective reconstruction may be unaffordable; emphasis falls on examination-based diagnosis, reassurance, simple calf-stretching programmes, and reserving theatre time for genuinely disabling or rigid deformity.

Universal Referral Triggers (resource-independent):

• Rigid foot or absent subtalar motion (suspect tarsal coalition or congenital vertical talus).
• Unilateral or asymmetric deformity.
• Pain or callosity limiting walking/sport.
• Failure of a supervised calf-stretching programme over roughly 6 months.