Imaging description

Tibial bowing is a collective term to describe congenital abnormalities associated with tibial bowing deformity. Straight AP and lateral radiographs are diagnostic to document direction of the bowing (apex side) and associated findings such as a skin dimple and foot deformity.

Importance

Identifying the direction of the apex side of the bowing is important to suggest the underlying conditions and, therefore, to predict the prognosis. For most of the cases, the bowing is the result of intrauterine positioning (deformation), in which postero-medial (or postero-lateral) bowing of the tibia and fibula occurs (Figure 57.1). Thickening of the bone on the concave side and thinning and dimpling of the skin on the convex side may be seen. This is considered to be a benign, self-resolving condition. Anterolateral bowing of the tibia is rare and may lead to pseudoarthrosis. Anterolateral bowing is commonly associated with neurofibromatosis type I (NF1) (Figure 57.2). Anteromedial bowing is also a rare condition, which may be associated with fibular hemimelia (postaxial hypoplasia of the lower extremity).

Typical clinical scenario

In congenital postero-medial bowing of the tibia and fibula, the bowing is seen at birth with a calcaneovalgus deformity. It corrects spontaneously for most of the cases. Rapid resolution of angulation occurs in the first year of life. However, persistent residual deformity may require surgical intervention. Anterolateral bowing of the tibia and fibula is most likely a presentation of tibial dysplasia in infancy or early childhood in patients with NF1. This form is considered as part of infantile pseudarthrosis since fracture and non-union commonly follow.