FLEXIBLE FLATFOOT
Pes Planus | Physiological | Jack's Test
TYPES OF FLATFOOT
Critical Must-Knows
- Natural History: Most infants have flat feet. The arch develops spontaneously within the first decade of life. 90% resolve by age 10.
- Physiological vs Pathological: Flexible, painless flatfoot is physiological. Painful or rigid flatfoot is pathological.
- Jack's Test: Passive extension of the big toe engages the Windlass mechanism. If the arch reconstitutes, it is flexible.
- Treatment: Asymptomatic flexible flatfoot requires NO treatment (no orthotics). Symptomatic cases start with calf stretching.
Examiner's Pearls
- "Look at the parents' feet. It is often familial.
- "Always check the shoes for wear patterns. Uneven medial wear suggests significant pronation.
- "Don't forget to assess generalized ligamentous laxity (Beighton Score).
Rigid Flatfoot Alert
Tarsal Coalition
It's not flexible. If the arch stays flat on toe-raise, suspect Tarsal Coalition. Look for peroneal spasm ("Peroneal Spastic Flatfoot").
Vertical Talus
Rocker Bottom. In congenital vertical talus (CVT), the foot is rigid and the sole is convex. This is NOT a flexible flatfoot.
At a Glance: Flexible vs Rigid Flatfoot
| Feature | Flexible | Rigid (Coalition/CVT) |
|---|---|---|
| Toe Raise Test | Arch Reappears | Flat remains |
| Jack's Test | Arch Reappears | Flat remains |
| Subtalar Motion | Normal / Hypermobile | Restricted / Absent |
| Pain | Usually Painless | Often Painful |
JACKAssessment Steps
Memory Hook:Know JACK about flat feet.
CALMSurgical Options
Memory Hook:CALM the painful foot.
PAINRed Flags
Memory Hook:PAIN is not normal.
Definitions
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.
Overview and Epidemiology
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").
Pathophysiology and Mechanisms
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.
- Spring Ligament:
- 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.
Classification
Harris and Beath (1947)
Classified based on talo-calcaneal overlap on weight bearing footprint (Harris Mat).
- Type I: Arch present.
- Type II: Arch absent, heel valgus. (Flexible).
- Type III: Rigid flatfoot (Coalition).
Most flexible feet are Type II.
Clinical Assessment
Clinical Flow
- Pain: Where? (Sinus tarsi impinging vs Medial strain).
- Activity: "Tired legs", "Refuses to walk distances".
- History: Prematurity? Developmental delay? Family history.
- Too Many Toes Sign: Viewed from behind. Seeing greater than 1.5 toes laterally suggests forefoot abduction.
- Heel Valgus: Assess relationship of heel to leg.
- Arch: Is it absent?
- Toe Raise Test: Ask child to stand on tiptoes. Heel should invert (varus) and arch usually appears.
- Jack's Test: Passively extend big toe in standing. Arch should rise.
- Gait: Check for antalgic gait or internal rotation.
- Silfverskiold Test: Differentiate Gastroc vs Soleus tightness. (Dorsiflexion with knee straight vs bent).
- Subtalar ROM: Must be free.
- Correction: Can you passively correct the foot to neutral?
Achilles Contracture
A tight Achilles (Gastrocnemius) is the most common cause of Symptomatic flexible flatfoot. The tight triceps surae prevents dorsiflexion at the ankle, so the midfoot "breaks" (dorsiflexes) to allow the foot to clear the ground, worsening the flatfoot.
Investigations
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.
Radiographic Angles
| Angle | Normal | Flatfoot |
|---|---|---|
| Meary's Angle (Lat) | 0 degrees (Straight line) | Convex downwards (Sag) |
| Calcaneal Pitch (Lat) | 20-30 degrees | Decreased (less than 15 even negative) |
| Talonavicular Coverage (AP) | Aligned | Lateral subluxation of Navicular |
CT/MRI:
- Only if suspecting coalition (CT) or tendon pathology (MRI). Not routine.
Management Algorithm
The Painless Flatfoot
- Reassurance: Explain natural history.
- Education: "The arch is like height - some are tall, some are short. Flat is just a variant."
- No Orthotics: Evidence shows orthotics do NOT change the shape of the foot or arch development (Wenger et al 1989). They are expensive and uncomfortable.
- Shoe Wear: Supportive heel counter shoes are fine, but barefoot walking is also healthy.
Do not treat X-rays.
Surgical Technique
Surgery aims to realign the foot. It is often a "A la carte" menu depending on the deformity.
Joint Sparing Osteotomies (Preferred)
Realigns anatomy without fusing joints.
-
Calcaneal Lengthening (Evans):
- Concept: Lengthens the lateral column. Pushes the navicular (and forefoot) medially, reducing abduction.
- Technique: Osteotomy 1.5cm proximal to CC joint. Insert trapezoidal bone graft.
- Effect: Corrects Forefoot Abduction AND Hindfoot Valgus.
- Risk: CC joint arthritis (increased pressure).
-
Medial Slide (Koutsogiannis):
- Concept: Translates posterior calcanues medially. Changes the pull of Achilles from evertor to invertor.
- Effect: Corrects Hindfoot Valgus only. Little effect on arch height.
-
Cotton Osteotomy:
- Concept: Opening wedge plantarflexion osteotomy of the Medial Cuneiform.
- Effect: Restores the medial column height (Arch).
- Indication: Persistent forefoot varus (supination) AFTER the heel is corrected. If you fix the heel and the big toe creates a "tripod" effect off the ground, you need to bring the ray down (Cotton).
- Graft: Use a wedge (Allograft or Autograft). Fix with a staple or plate.
-
Mosca Procedure:
- Combination of Evans + Soft tissue plication.
- Gold standard for severe deformity.
- Steps:
- Approach lateral calcaneus.
- Osteotomy and graft (Evans).
- Medial approach.
- Plication of Talonavicular capsule (advancing the spring ligament).
- TAL (Percutaneous).
Complications
Surgical Risks
| Procedure | Specific Risk | Prevention |
|---|---|---|
| Evans Osteotomy | CC Joint Arthritis / Dorsal Subluxation | Don't over-stuff the graft. |
| Medial Slide | Sural Nerve Injury | Careful dissection laterally. |
| Arthroereisis | Sinus Tarsi Pain | Remove implant. |
| All | Under-correction | Address both limited Equinus and Valgus. |
Postoperative Care and Rehabilitation
Protocol (Osteotomy)
- Non-Weight Bearing (NWB): Cast applied.
- Elevation: Critical for swelling control.
- X-ray: Check graft healing at 6 weeks.
- Aircast Boot: Weight bearing as tolerated (guided by X-ray).
- ROM: Start Ankle and Subtalar ROM.
- Transition: Into supportive runners.
- Physio: Gait training, calf stretching (prevent recurrence of equinus).
- Return to Play: When fusion solid and strength regained.
- Plyometrics: Hopping, skipping to recruit peroneals and tib post.
- Orthotics?: Generally NOT needed post-op, but some surgeons use arch supports for transition.
Physiotherapy Focus
| Muscle Group | Exercise | Rationale |
|---|---|---|
| Gastrocnemius | Wall Stretch / Night Splint | Corrects Equinus driver |
| Tibialis Posterior | Heel Raises with Ball squeeze | Dynamic arch support |
| Intrinsics | Towel gather / Marble pick-up | Core strength of foot |
| Peroneals | Balance Board | Ankle stability |
Outcomes
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.
Evidence Base
Natural History of Flatfoot
- Randomized trial of Orthotics vs Shoes vs Barefoot in children.
- Found NO difference in arch development between groups.
- Concluded that corrective shoes/inserts do not change the natural history.
- Treatment should be reserved for symptomatic patients only.
Evans Osteotomy Long Term
- Long term results of lateral column lengthening.
- Excellent correction of all components of deformity.
- Functional satisfaction high.
- Some radiographic evidence of CC joint arthrosis but usually asymptomatic.
Arthroereisis Outcomes
- Systematic review of subtalar arthroereisis.
- High complication rate (pain), with implant removal rates up to 30%.
- Evidence quality is generally poor.
- Recommended caution.
Obesity and Flatfoot
- Prevalence of flatfoot in preschool children.
- Strong correlation with obesity.
- Boys more affected than girls.
- Most resolve with age, but obesity is a barrier.
Lateral Column Lengthening
- Original description of the procedure.
- Elongation of the lateral column pushes the navicular medially.
- Corrects all components of the deformity (Valgus, Abduction, Sag).
- Good functional results in severe cases.
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
"A worried mother brings her 2-year-old son. He has flat feet. 'His dad has flat feet too'. He runs and plays without pain."
"A 12-year-old boy has painful flat feet. Medial arch pain. Short calf muscles. Flexible on exam."
"Discuss the role of Arthroereisis (Subtalar screw)."
MCQ Practice Points
Most Common Complication
Q: What is the most common potential complication of a lateral column lengthening (Evans)? A: Calcaneocuboid joint arthritis (due to increased joint pressure) or Dorsal subluxation of the CC joint.
Natural History
Q: At what age do most flexible flat feet resolve? A: By age 10 years. The arch development curve plateaus at this age. If it hasn't formed by 10, it likely won't.
Jack's Test
Q: What mechanism is tested by passive extension of the hallux? A: The Windlass Mechanism (Shortening of plantar fascia elevates the arch).
Coalition Screen
Q: If the arch does NOT reconstitute on toe standing, what is the likely diagnosis? A: Rigid Flatfoot (Tarsal Coalition or Vertical Talus).
Equinus
Q: What soft tissue contracture is most strongly associated with symptomatic flatfoot? A: Gastrocnemius-Soleus complex (Achilles) tightness. Always test with the knee straight (Gastroc) and bent (Soleus) - Silfverskiold Test.
Vertical Talus
Q: How do you clinically differentiate Oblique Talus (Severe Flatfoot) from Vertical Talus (CVT)? A: In CVT, the foot is rigid and the hindfoot is in valgus but the forefoot is dorsiflexed (Rocker Bottom). You can palpate the head of the talus in the sole. In flexible/oblique talus, the deformity reduces.
Surgical Anatomy
Q: Which nerve is at risk during the lateral approach for a Medial Slide calcaneal osteotomy? A: The Sural Nerve. It runs with the small saphenous vein posterior to the lateral malleolus.
Tarsal Coalition Sign
Q: What is the 'C-Sign' on a lateral foot X-ray indicative of? A: Talocalcaneal coalition. It represents a bony bridge between the talus and calcaneus.
Variable Pitch
Q: What happens to the calcaneal pitch angle in flatfoot? A: It decreases (flattens), often becoming less than 15 degrees or even negative (rocker bottom).
Australian Context
Epidemiology:
- Extremely common. One of the most common referrals to outpatient clinics.
- Often "Grandmother Syndrome" (Grandmother thinks the foot looks flat).
- Choosing Wisely Australia:
- Do not order X-rays for painless flexible flatfeet.
- Do not prescribe orthotics for painless flexible flatfeet.
- Do not refer unless symptomatic or rigid.
Public vs Private System:
- Public: Long waitlists. Most referrals are triaged to non-op "Podiatry/Physio" clinics first. Surgery is focused on functional disability.
- Private: Parents often seek second opinions for "appearance". Ethical counselling is paramount. "We treat patients, not X-rays."
Referral Guidelines (RCH Melbourne):
- GP Management: Reassurance, calf stretches, simple pharmacy insoles if mild pain.
- When to Refer:
- Rigid foot (Coalition).
- Severe pain limiting sport.
- Unilateral deformity.
- Failed 6 months of physio/stretching.
Medicare Codes:
- 48403: Osteotomy of calcaneus (Evans/Slide).
- 49728: Foot, arthroereisis.
- 47960: Tenotomy, lengthening (Achilles).
High-Yield Exam Summary
Diagnosis
- •Flexible: Arch restores on tiptoe
- •Rigid: Arch stays flat (Coalition)
- •Physiological: Painless
- •Pathological: Painful / Rigid
- •Vertical Talus: Rocker Bottom
Assessment
- •Jack's Test (Windlass)
- •Toe Raise Test
- •Silfverskiold (Equinus)
- •General Laxity (Beighton)
- •Too Many Toes Sign
Management
- •Asymptomatic: Reassurance
- •Symptomatic: Stretch & Orthotics
- •Surgery: Evans Osteotomy
- •Always lengthen Achilles
- •Avoid Arthroereisis (Risk)