Posteromedial bowing of the tibia is a unilateral lower extremity deformity present at birth. It is characterized by varying degrees of apex medial and apex posterior deformity of the tibia and fibula. The exact etiology remains unknown
- This deformity, present at birth, is usually unilateral (left > right).
- Boys and girls are affected equally.
- By definition, apex posterior and apex medial bowing exists in the tibia and fibula, with the posterior bow > medial bow.
- A dimple at the apex of the angulation may also be present.
- A calcaneovalgus alignment of the ipsilateral foot is often noted at initial presentation.
- Ankle range of motion may show increased dorsiflexion and reduced plantarflexion.
- The patient may have a smaller calf circumference and smaller size foot (width and length) on the involved limb.
- Posteromedial bowing of the tibia is considered a benign condition because the bowing tends to correct spontaneously, although there is usually a residual leg length discrepancy.
- The reduction in angulation of the bowing in both planes occurs most rapidly in the first year of life and then slows.
- The posterior bow tends to correct faster than the medial bow.
- The tibial shortening ranges from 15% to 40% at initial presentation and progresses to an average leg length discrepancy from 3 to 7 cm.
- Children with increasing severity of bowing at presentation develop larger limb length discrepancies than those with less severe initial bowing.
- Ankle valgus is common for the following reasons: Under age 2, eccentric ossification of the distal tibial epiphysis is common, and over age 2, wedging of the distal tibial epiphysis is common. The lateral malleolus may also be proximally located.
- Anterolateral bowing – congenital pseudarthrosis of the tibia
- Anteromedial bowing – fibular hemimelia
- At birth, no treatment is necessary for bowing, only observation over the first 2 years. Significant deformity should correct spontaneously (Figures 1-4).
Figure 1. Infant with posteromedial bowing of the tibia
Figures 2-3. AP (left) and lateral views of the same child's leg 7 years later. The deformity has spontaneously corrected itself.
Figure 4. Residual leg length discrepancy
- Gentle stretching exercises may be utilized to correct dorsiflexion contracture of the calcaneovalgus foot deformity.
- A shoe lift may be necessary to equalize leg lengths in the young child.
- The role of surgical intervention is to correct residual bowing of the tibia, limb length inequality, and ankle valgus.
- Bowing and limb length discrepancy can be corrected simultaneously with an external fixator.
- Hemi-epiphysiodesis is effective at correcting ankle valgus in skeletally immature patient.
Hofmann A, Wenger DR. Posteromedial bowing of the tibia. J Bone Joint Surg 1981;63-A:384-388.
De Maio F, Corsi A, Roggini M, et al. Congenital unilateral posteromedial bowing of the tibia and fibula: Insights regarding pathogenesis from prenatal pathology. J Bone Joint Surg 2005;87-A:1601-1605.
Shah H, Doddabasappa S, Joseph B. Congenital posteromedial bowing of the tibia: a retrospective analysis of growth abnormalities in the leg. J Ped Orthop B 2009;18:120-128.