Tibial torsion, External (Pediatric)

Synonyms
Lateral tibial torsion, ETT

INTRODUCTION

Definition

A condition characterized with external rotation of the lower extremity.

Epidemiology

  • Affects older children or adolescents. Usually worsens during late childhood and early adolescence, since the leg externally rotates with physical growth.
  • Tends to be more often unilateral, primarily affecting the right side.
  • The condition may be bilateral.

Etiology

Unknown etiology.

Relevant Anatomy

  • Tibia externally rotates on average 15° during early childhood.
  • Femoral anteversion decreases on average 25° during early childhood.

Differential Diagnosis

Out-toeing may be caused by:
  • Femoral retroversion.
  • External rotation contracture of the hip.
  • External tibial torsion.
  • Abduction of the forefoot associated with pes planovalgus.
  • Slipped capital femoral epiphysis.
  • Coxa vara.
  • Hip dysplasia.

CLINICAL FEATURES

Symptoms

  • Will cause out-toeing and may lead to disability and decrease physical performance.
  • May be associated with inefficient gait and patellofemoral joint pain, that is presumably due to malalignment of the knee and the line of progression.
  • In contrast to internal tibial torsion which usually improves with growth, ETT becomes worse with time.

Signs

Inspection: The knee is internally rotated and the ankle externally rotated.
Assess the rotational profile:
  • Thigh-foot axis measurement: This is the best way to evaluate tibial torsion.
    • Measurment: The patient lies prone with knee flexed to 90°. The thigh-foot-axis is the angle subtended by the thigh and the longitudinal axis of the foot.
    • Value
      • Average during infancy is 5° internal rotation, that slowly derotates.
      • Average at 8 years of age is 10° external, ranging from -5 to +30°.
  • Transmalleolar axis: This is another way to evaluate tibial torsion.
    • Measurment: The patient lies supine and an imaginary line from medial malleolus to lateral malleolus and another imaginary line from medial to lateral femoral condyle is made. The transmalleolaraxis is the angle made at the intersection of these two lines. It helps to determine the direction and extent of tibial torsion present.
    • Value
      • Average at infancy is 4-5° internal rotation.
      • Average at adulthood is 23° external (range 0-40° external).

Associated Conditions

ETT is associated with:
  • Miserable malalignment syndrome: Defined as external tibial torsion with femoral anteversion.
  • Neuromuscular conditions: Myelodysplasia and polio.
  • Osgood-Schlatter disease
  • osteochondritis dessicans
  • Early degenerative joint disease

DIAGNOSIS

Conventional Radiography

Usually note required.

TREATMENT

Overview

Initially treated with rest and rehab. 

Nonoperative Treatment

Indication: First line of treatment.
Method: Rest, rehab, and activity modifications.
  • Shoe modifications and orthotic devices incorporating twister cables have not been shown to be effective.

Operative Treatment

Indication: External tibial torsion greater than 3 standard deviations above the mean ( > 40° external), in children older than 8-10 years of age.
Method: Supramalleolar derotational osteotomy or proximal tibial derotational osteotomy.
  • Supramalleolar rotational osteotomy is most commonly performed.
  • Proximal tibial osteotomies should be avoided due to higher risk factors associated with these procedures.

Operation Methods

Supramalleolar rotational osteotomy:
  • Osteotomy:
    • It is less likely to be complicated by injury to the vessels or a compartment syndrome.
    • Associated varus or valgus deformities of the ankle can also be corrected at this level.
    • Fibula is obliquely osteotomized if the deformity is severe.
  • Fixation:
    • Internal fixation with two crossed K-wires is adequate.
    • Sometimes fixation is made witha plate.
  • Intramedullary fixation with rotational osteotomy: Reserved for skeletally mature adolescents.
Proximal metaphyseal osteotomy:
  • Indication: ETT with an associated tibia vara in the older child, despite the higher risks of neurovascular injury.

COMPLICATIONS AND PROGNOSIS

Complications

  • May result in lever arm dysfunction.
  • Associated with miserable malalignment syndrome and may have an association with degenerative joint disease.

Prognosis

May cause disability and degrade physical performance, in contrast to internal tibial torsion.
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References