Flat-foot

Congenital vertical talus (infantile flat-foot)

• Rare.
• Both feet.
• The opposite of club foot: Foot is turned outwards (valgus) and the medial arch curves the opposite way from normal, creating a rocker-bottom foot.
• X-ray: (1) Calcaneum is in equinus, (2) Talus points into the sole, (3) Navicular dislocated dorsally onto the neck of the talus.
• Passive correction impossible.
• Ligaments on dorsolateral side of the foot shortened.
• Only Rx = operation, ideally before age 2y.

Flat foot in children and adolescents

(1) Foot is turned outwards, (2) Heel is in valgus, (3) Medial border of the foot is in contact with the ground.

Flexible

• Appears in toddlers as a normal stage in development; sometimes does not disappear but function is unlikely to be impaired.
  
• Arch is restored by extending the great toe (jack test or great toe extension test); ask patient to stand on tiptoes. During this manoeuvre the tibia rotates externally.
• Many have ligamentous laxity. There may be Fx of flat-feet and joint hypermobility.
• Test the range of movement in the ankle, subtalar and midtarsal joints. A tight Achilles tendon may induce a compensatory flat-foot.
• No Rx needed.
  

Rigid flat-foot

• Cannot be corrected passively.
• Underlying abnormality e.g. tarsal coalition (calcaneum to talus or navicular), inflammatory joint condition, neurological disorder.
• Spasmodic flat-foot: Peroneal and extensor tendons are in spasm. Painful. Relieved by rest in a cast or splint.
  
• In many no specific cause is identified.
• In both flexible and rigid flat-foot, examine spine, hips and knees + general examination for joint hyper mobility and neuromuscular abnormalities.
• Standing AP + lat + oblique X-rays for pathological flat-feet.
• CT is the most reliable way of demonstrating tarsal abnormalities.
• Rx = Splintage or operative correction and muscle rebalancing. Removal of tarsal bar or other bony irregularity. In late cases with pain triple arthrodesis (fusion of TC, TN, CC joints) may be necessary.

Flat-foot in adults

• Constitutional flat-feet which have been mostly asymptomatic for many years may start causing nagging pain after change in daily activities (e.g. new job with a lot of standing and walking).
• Recent-onset flat-foot may be due to an underlying disorder e.g. RA, generalised muscular weakness.
• Unilateral flat-foot should make one think of tibialis posterior synovitis or rupture. Rx = operative repair or replacement of the defective tendon.
• Rx: If no underlying deformity little can be done. Advise about comfortable footwear and arch supports. If painful and rigid more robust splintage is needed.