Tibial Dysplasia (Congenital Tibial Bowing)

Types of tibial bowing

Physiologic bowlegs (genu varum) in toddlers are different: both legs curve at the knees and straighten by about age 3.

Anterolateral bowing and congenital pseudarthrosis

In anterolateral bowing, the tibia is narrowed, sclerotic (hard but brittle) or cystic, often with abnormal fibrous tissue around it. Many children have neurofibromatosis type 1, and about 2 to 4% of people with NF1 have this type of bowing.

When the bone breaks, often with minimal trauma in the first years of life, it may not heal and instead forms a false joint. This is congenital pseudarthrosis of the tibia (see pseudarthrosis). It is one of the most challenging conditions in pediatric orthopedics.

Symptoms

• visible bowing of the lower leg present at or soon after birth
• shortening of the affected leg
• limping when the child starts walking
• pain, swelling or instability if a fracture or pseudarthrosis develops
• signs of NF1, such as cafe-au-lait spots or freckling in skin folds

Diagnosis

• examination: direction of the bow, leg lengths, foot position, skin signs of NF1
• X-rays of the tibia and fibula: show bowing, narrowing, cysts, sclerosis or pseudarthrosis, and help classify severity
• evaluation for NF1 by a geneticist or NF specialist
• MRI occasionally, to assess soft tissue

Treatment

Anterolateral bowing without fracture

• protective bracing: a clamshell brace or a knee-ankle-foot orthosis (KAFO) worn full-time once the child stands, often until skeletal maturity, to reduce fracture risk
• avoid high-impact activities
• regular monitoring with X-rays
• prophylactic surgery in selected cases

Congenital pseudarthrosis

Surgery aims to achieve and maintain bone union:

• removal of abnormal bone and fibrous tissue
• stabilization with an intramedullary rod, sometimes with an external fixator (Ilizarov frame)
• bone grafting, sometimes including a vascularized fibula graft
• cross-union techniques joining the tibia and fibula
• bone-stimulating agents in some centers

Repeat surgeries are common. In severe, unresponsive cases, amputation with a prosthesis can give better function than repeated failed operations.

Posteromedial bowing

Usually observation, with stretching for the foot. The bow tends to improve, but a leg length difference may persist and can be treated with a shoe lift, growth plate surgery (epiphysiodesis) or limb lengthening.

Outlook

Posteromedial bowing has a good outlook. Anterolateral bowing requires long-term care. With modern techniques, most children with pseudarthrosis eventually achieve bone union, though many need multiple surgeries, and leg length differences and ankle problems are common.

Frequently asked questions

What is tibial dysplasia?

Tibial dysplasia is abnormal development of the shinbone, usually present at birth, that causes the lower leg to bow. The type of bowing, anterolateral, posteromedial or anteromedial, determines the cause, risks and treatment.

Is tibial bowing linked to neurofibromatosis?

Yes. Anterolateral bowing of the tibia is strongly associated with neurofibromatosis type 1, and about half or more of children with this type have NF1. Children with this bowing should be evaluated for NF1.

What is congenital pseudarthrosis of the tibia?

It is a fracture of a dysplastic tibia that fails to heal, forming a false joint. It most often develops from anterolateral bowing, usually in early childhood, and requires specialized surgery to achieve healing.

Will my baby's bowed leg straighten on its own?

It depends on the type. Posteromedial bowing usually improves over the first few years. Anterolateral bowing does not straighten and needs bracing and monitoring because of fracture risk. A pediatric orthopedic specialist can identify the type with an exam and X-rays.

How is anterolateral tibial bowing treated?

It is usually treated with a protective brace worn full-time when the child is upright, to prevent fractures. If a fracture or pseudarthrosis occurs, surgery is needed to remove abnormal tissue, stabilize the bone and promote healing.