Abnormal Foot

Janice L. B. Byrne, MD

DIFFERENTIAL DIAGNOSIS

Common

Less Common

Rare but Important

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Is the anomaly an isolated finding?
Are there multiple anomalies?
Bilateral vs. unilateral
Are hands similarly affected?
Is the finding associated with abnormal or lack of fetal movement?
- Lack of movement within the amniotic cavity?
- Does the fetus appear “stuck” to the placenta?

Helpful Clues for Common Diagnoses

Clubfoot
- Plane of imaging important
  - Coronal view: Ankles should be straight
  - Lateral view: Bones of foot and tibia/fibula should not be seen in same plane
  - “Footprint” view: Clubfoot associated with abnormal shape/shortening
- Bilateral vs. unilateral
- Limitations to diagnosis
  - Gestational age: Clubfoot difficult to diagnose past 2nd trimester
  - Oligohydramnios
  - Crowding in multiple gestation
  - Footling breech position limits visualization of feet
Rockerbottom Foot
- Prominent heel associated with rounded bottom of foot
- Best seen in lateral view
- May be associated with dorsiflexed great toe, short hallux
- Look carefully for other anomalies associated with trisomy 18
  - Persistently clenched hands or overlapping digits
Sandal Gap Foot
- Gap between great toe and 2nd toe
- May be normal finding with fetal “flare” of toes while moving feet
- Look for persistence of gap even when fetus at rest
- Most often seen in normal fetuses but is a minor marker in trisomy 21
Edema of Feet and Extremities
- Pattern of edema important for establishing differential diagnosis
- Edema of extremities vs. body edema
- Unilateral edema concerning for obstructive phenomenon such as amniotic bands or tumor

Helpful Clues for Less Common Diagnoses

Amniotic Band Syndrome
- Amputations of digits or feet/hands
- Usually asymmetrical
- Associated disruptions of face, calvarium, body wall
- Constriction rings of extremities
- Adherence to placenta in severe cases
- Extremity edema distal to constriction band is common
Ectrodactyly
- Split hand-split foot malformation
  - Fusion of digits with deep median cleft (“lobster claw”)
- May be unilateral or bilateral
- May involve upper, lower, or both
- Variable appearance between extremities
Abnormal Toes
- Polydactyly
  - Often difficult to diagnose, especially in early gestation
  - Foot usually appears wider than normal
  - Look at hands for extra fingers
  - Post-axial more common than pre-axial except in diabetic embryopathy
- Syndactyly
  - Usually not diagnosed prenatally
  - May be associated with abnormal shape of foot
- Oligodactyly
  - Foot appears narrow
  - Often associated with abnormality of tibia or fibula
  - Abnormal position of foot common
Terminal Transverse Limb Defect
- Varying degree of limb deficiency
- May be seen with congenital varicella infection

Helpful Clues for Rare Diagnoses

Sirenomelia
- Legs may appear “stuck” together
- Single femur or fewer than 4 lower extremity long bones valuable clues
- Foot/feet may be absent, single, or a complex fusion of structures
- Usually associated with bilateral renal agenesis
- May be difficult to visualize due to oligohydramnios
Amelia, Micromelia
- Extremities may be absent (amelia) vs. severely shortened (micromelia)
- May be limited to upper or lower extremities
- Digits may be present
- Symmetrical micromelia associated with severe skeletal dysplasias

Other Essential Information