Flatfoot Deformities

Introduction & Anatomy - Fallen Arches 101

Pes planus, or "fallen arches," signifies the collapse or flattening of the medial longitudinal arch (MLA) of the foot. This common deformity can be flexible or rigid.

• Core Anatomical Components:
  • Medial Longitudinal Arch (MLA): Keystone arch; primary shock absorber.
  • Tibialis Posterior Tendon (TPT): Crucial dynamic stabilizer; its dysfunction is a common cause.
  • Spring Ligament (Plantar Calcaneonavicular): Major static supporter of the talar head.
  • Deltoid Ligament Complex: Provides medial ankle stability; can attenuate in progressive deformity.

⭐ The tibialis posterior tendon is the primary dynamic stabilizer of the medial longitudinal arch; its insufficiency is a hallmark of adult-acquired flatfoot.

Etiology & Classification - Why Feet Flatten

• Etiological Types:

  • Congenital:
    • Tarsal Coalition: Bony fusion (calcaneonavicular, talocalcaneal). "Painful peroneal spastic flatfoot".
    • Congenital Vertical Talus.
  • Acquired: Develops later.

    ⭐ Posterior Tibial Tendon Dysfunction (PTTD) is the most common cause of adult acquired flatfoot.

    • Charcot Arthropathy: Neuropathic joint destruction (common in diabetes).
    • Ligamentous laxity (e.g., Ehlers-Danlos).
    • Trauma, Inflammatory arthritis (e.g., RA).

• Classification by Flexibility:

  Feature	Flexible Flatfoot	Rigid Flatfoot
  Arch	Collapses on load, reforms off-load	Stiff, always flat
  Key Causes	Laxity, early PTTD	Tarsal coalition, advanced arthritis

• PTTD Stages (Johnson & Strom Classification):

Clinical Assessment - Spotting the Signs

• Symptoms:
  • Medial ankle/hindfoot pain, fatigue.
• Key Physical Signs:
  • "Too many toes" sign: >2-3 toes visible laterally (posterior view) → forefoot abduction.
  • Heel Rise Test (Single/Double): Difficulty/pain, hindfoot remains in valgus (Posterior Tibial Tendon Dysfunction - PTTD).
  • Forefoot abduction, Hindfoot valgus.
• Radiographic Evaluation (Weight-bearing views):
  • Views: AP, Lateral, Hindfoot alignment (e.g., Saltzman).
  • Key Angles:
    • Meary's Angle (Lat): $angle(talus_long_axis, first_metatarsal_long_axis)$. Normal: 0°. Apex plantar in flatfoot.
    • Talonavicular Coverage Angle (AP): Normal: < 7°. ↑ indicates talar subluxation.
    • Calcaneal Pitch (Lat): Normal: 20-30°. ↓ in flatfoot (e.g., < 18°).

⭐ The "too many toes" sign, seen from posterior, is indicative of forefoot abduction and hindfoot valgus.

Management Strategies - Fixing Flat Feet

Conservative:

• Activity modification, NSAIDs
• Orthotics: UCBL, SMO
• Physiotherapy

Surgical (Indications: Failed conservative, progressive deformity, pain):

• Soft Tissue:
  • PTT repair/debridement
  • FDL transfer to navicular
  • Spring ligament repair
• Osteotomies:
  • MDCO
  • LCL (Evans)
  • Cotton (medial cuneiform)
• Arthrodesis: Subtalar, talonavicular, double, triple

PTTD Stage-Specific Management:

• I: Conservative (NSAIDs, orthotics, PT).
• II (Flexible deformity):

  ⭐ FDL (Flexor Digitorum Longus) tendon transfer is commonly used to substitute for the dysfunctional PTT in flexible flatfoot (Stage II PTTD).

  • FDL transfer, PTT debridement/repair, spring lig. repair ± osteotomies (MDCO, Evans, Cotton), ± gastroc recession.
• III (Rigid deformity): Arthrodesis (e.g., triple).
• IV (Ankle valgus/arthritis): Arthrodesis (triple/pantalar) ± deltoid repair.

High‑Yield Points - ⚡ Biggest Takeaways

• Flexible flatfoot is common in children, often self-correcting; rigid flatfoot is pathological.
• Posterior Tibial Tendon Dysfunction (PTTD) is the most common cause of Adult Acquired Flatfoot Deformity (AAFD).
• "Too many toes" sign is a key indicator for AAFD/PTTD.
• Tarsal coalition (e.g., talocalcaneal) is a primary cause of adolescent rigid flatfoot.
• Jack's test assesses hindfoot flexibility; arch restoration indicates flexible flatfoot.
• Important radiographic angles: Meary's angle, calcaneal pitch, talar declination angle.