CONGENITAL BOWING OF THE TIBIA

1. Posteromedial bowing of the tibia and fibula (1-3).

· Tibia and fibula are angulated posteriorly and medially.

· Usually middle or distal third of the shaft.

· Calcaneovalgus deformity (dorsum of the foot touches the lower part of the leg).

· Foot and ankle are normal.

· Always unilateral.

· No side predilection.

· Cause is unknown? Suggested causes include abnormal fetal position or intrauterine fracture, or a primary defect in the embryological development of the lower leg and the tibial or fibular shafts.

· Prognosis is good. There is usually spontaneous, although incomplete correction of the bowing within the first four years of life.

2. Bilateral congenital shortening and bowing of the long bones.

· May be associated with skeletal dysplasias.

· Larsen’s syndrome (shortening and bowing of the bone is due to dislocation or subluxation of the knees.

· Campomelic dysplasia.

3. Anterolateral angulation of the tibia (3,4).

· High risk of spontaneous fracture and subsequent pseudoarthrosis of the tibia, fibula, or both.

· Anatomy and position of the foot are normal.

· Strongly associated with neurofibromatosis.

CAMPOMELIC DYSPLASIA – BOWING OF THE TIBIA

• Sporadic.
• Autosomal recessive.

ULTRASOUND

• Bowing of tibia + femur.
• Hypoplastic fibula.
• Macrocephaly, Holoprosencephaly.
• Cloverleaf skull (rarely).
• Micrognathia (90-99%).
• ± Cleft palate.
• Chest and spine.
• Hypoplastic scapulae (92%).
• Narrow bell chest.
• Hypoplastic vertebral bodies.
• Clubfoot.

ASSOCIATED ANOMALIES

• Hydrocephalus (23%).
• Congenital heart disease (30%).
• ASD, VSD, Tetralogy of Fallot, Aortic Stenosis.
• Hydrocephalus (30%).

DIFFERENTIAL DIAGNOSIS

• Non lethal forms of osteogenesis imperfecta.
• Features favoring a diagnosis of osteogenesis imperfecta
• Arm fractures with callous.
• Cranial compressibility.
• Lack of cranial ossification.
• Variable and asymmetric leg lengths.
• Features favoring a diagnosis of campomelic dysplasia.
• Club feet.

REFERENCES

1. Papas AM. Congenital posteromedial bowing of the tibia. J Pediatr Orthop 1984;4:525-531.
2. Yadav SS, Thomas S. Congenital posteromedial bowing of the tibia. Acta Orthop Scand 1980;51:311-313.
3. Zollinger PE, Wessels MW, Wladimiroff JW, Diepstraten AFM. Prenatal ultrasonographic diagnosis of posteromedial bowing of the legs: two case reports. Ultrasound Obstet Gynecol 2000;15:150-153.
4. Adamsbaum C, Kalifa G, Seringe R, Bonnet J-C. Minor tibial duplication: a new cause of congenital bowing of the tibia. Pediatr Radiol 1991;21:185-188.