Diaphysis (Long Bones): Bowing

10.1055/b-0034-87936

Diaphysis (Long Bones): Bowing

Bowing may be congenital or acquired. The direction of bowing of the tibia may suggest the etiology. Anterolateral bowing of the tibia is associated with neurofibromatosis, tibial fractures, and congenital pseudarthrosis of the tibia. Posteromedial tibial bowing is an isolated finding not associated with other conditions.

**Table 5.57 Diaphysis: bowing**
Diagnosis	Findings	Comments
Physiologic bowling of toddlers	Femur and tibia are mildly bowed.	Predilection for the first 2 y of life. Corrected within 6 mo of walking. Reaches adult pattern of mild valgus by 6–7 y.
Plastic/bowing fracture	Bowing of radius or ulna are the most common sites.	If the radius is fractured, the accompanying bone (ulna) may be fractured (and vice versa).
Rickets Fig. 5.90	(see Table 5.42 )	Widening of the medial aspect of the growth plate in older children with an ossified distal femoral epiphysis. The weight-bearing part is always the widest.
Recurrent fracture with malposition	Bowing of fragile bones after repeated fractures.	Occurs in all bone disorders with increased bone fragility (e.g., osteogenesis imperfecta and other intrinsic sclerotic bone dysplasias).
Fibrous dysplasia Fig. 5.91a, b, p. 558	Expansile and lucent lesion with a ground-glass matrix.	Typically restricted to the polyostotic variety. Medial bowing of the proximal femur (Shepherd crook deformity).
Intrauterine malposition/congenital bowing of the tibia	Unilateral bowing, mostly involving the tibial diaphysis. Lateral and posterior bowing. Fibula is also bowed.	Believed to result from an abnormal intrauterine position. Usually heals in the neonatal period.
Neurofibromatosis Fig. 5.92a, b, p. 558	Anterolateral bowing.	Ten percent of patients with neurofibromatosis will have pseudarthrosis of the tibia.
Tibia vara (Blount disease) Fig. 5.43, p. 524	Varus angulation of the proximal tibia.	Changes in the posteromedial proximal tibial epiphysis that lead to growth suppression. Any varus angulation at the knee in children > 2 y is considered abnormal.
Pseudarthrosis of the tibia	Anterolateral bowing.	Almost always unilateral. Associated with neurofibromatosis (40%–50% of pseudarthroses of the tibia).
Other syndromes and dysplasias Fig. 5.93, p. 559 Fig. 5.94, p. 559 Fig. 5.95a, b, p. 559		Osteogenesis imperfecta, achondroplasia, and camp-omelic dysplasia, for example.