Pediatric Limb Length Discrepancies

By: Jason Malone, DO

Q: HOW COMMON ARE PEDIATRIC LIMB LENGTH DISCREPANCIES?

A: Limb length discrepancies are very common. Up to twothirds of the population have a leg length difference of less than 2 cm (0.79 inch). Luckily, most people do not have symptoms unless the difference is greater than 2 cm.

Q: WHAT ARE CAUSES OF LIMB LENGTH DISCREPANCIES?

A: Limb length discrepancies can be categorized into two major groups: congenital and acquired.

Congenital causes range from longitudinal deficiencies such as congenital short femurs, proximal focal femoral deficiencies, tibia hemimelia, fibular hemimelia, hemihypertrophy, unilateral clubfoot, skeletal dysplasias, and hip dysplasia. Acquired causes range from idiopathic, paralytic disorders such as cerebral palsy or polio and physeal injury from trauma, infection or tumors.

Q: WHAT TECHNIQUES DO YOU USE TO TREAT THESE PATIENTS?

A: Symptomatic leg length differences less than 1 cm can be treated with a shoe insert. A difference greater than 1 cm can be addressed with nonsurgical treatment with a customized shoe lift. However, some patients or families do not wish to use a brace or shoe insert for the rest of their life.

Leg differences can be treated with a shortening procedure on the long side or a lengthening procedure on the short side or a combination of the two. Shortening procedures are smaller surgeries that are quicker to recover from but do lead shorter stature. Lengthening procedures are classically done for differences greater than 5 cm but many deformity specialists are now treating smaller leg length differences down to 3 cm in skeletally mature patients.

Q: HOW DOES THE PROCESS WORK?

A: Limb Lengthening procedures were first described by Dr. Gavriil Ilizarov in the 1950s. He called the process distraction osteogenesis. The process entails making a fracture in a bone, having the patient rest for 5-7 days, then distracting the bone ends about 1 mm per day. The bones can be distracted with an external fixator, a mechanical intramedullary nail, and soon with an expanding plate. We can safely lengthen a bone about 5 cm per treatment.

External fixators are better for legs that have an associated large deformity or children with open growth plates. Intramedullary nails are better tolerated but can only be placed in the femur of children at least 8 years old once the growth plate is closed in the tibia. The new lengthening plates that should be out in the summer of 2021 will allow us to lengthen internally even when a child has an open growth plate.

Shortening procedures usually are done in growing children. This is done through a timed epiphysiodesis. I prefer to perform a percutaneous epiphysiodesis as it leaves small scars and is associated with less complications than other techniques. This is done for leg difference of 2-5 cm.

Q: HOW LONG DOES THE PROCESS TAKE?

A: Distraction osteogenesis is a long process. After the initial surgery we wait about a week for the bony callus or regenerate to develop. We then lengthen 1 mm per day. Then the bone takes about 8-12 weeks to fully heal the regenerate. A large 5 cm lengthening can take about 100 days to fully heal.

Q: WHAT ARE THE POTENTIAL COMPLICATIONS INVOLVED?

A: Distraction osteogenesis is safe if performed and monitored by an experienced physician, but it can also be associated with multitude problems. The bones, tendons, muscles and neurovascular structures are growing faster than the body is used to growing, so patients can develop joint contractures, joint dislocations and nerve stretch. We combat this by using nighttime braces, starting physical therapy right away, and stopping the lengthening process if any major complication develops. We can also lengthen more in the future. You also have your standard complication that can happen with any orthopedic procedure such as infection, nonunion, malunion or hardware failure.

An epiphysiodesis can also have its complications such as fracture at the physis, continue growth, angular deformity if the entire growth plate is not fully removed and continues to grow, not timing the surgery right and not achieving the desired correction or even overcorrecting and needing to perform an epiphysiodesis on the contralateral side.

Q: WHEN SHOULD A CHILD SEE A SPECIALIST TO ADDRESS THE DISCREPANCY?

A: A child should see a pediatric orthopedic surgeon specialized in deformity correction when they have a congenital leg length difference, when they have a physeal injury, or an idiopathic leg length difference that is symptomatic or over 2 cm.

Q: ARE YOU CURRENTLY DOING ANY RESEARCH IN THE FIELD?

A: I just finished a research paper looking through a nationwide database from 1997-2016 on trends in femoral lengthenings in pediatric patients. What we found are that most of the surgeries are performed in large urban teaching hospitals. The South does more lengthenings than any other region in the country. The surgery has become safer over the years with shorter hospital stays but like most of medicine, the costs have risen substantially through the years. We currently have the paper submit for publication.

Jason Malone, DO, is a fellowship-trained pediatric orthopedic surgeon at Nemours Children’s Health who specializes in treating limb length discrepancies and deformities. Call (407) 650-7715 for more information.

9-year-old boy had a physeal injury to his left tibia. He sustained a 5 cm leg length difference with a flexion deformity of his knee. He had a projected leg length difference 9.6 cm.

He was treated with a hexapod external fixator to lengthen his leg 5 cm and correct his deformity.

16-year-old boy with an idiopathic 4 cm leg length difference, right genu valgum and an osteochondroma.

He was treated with a lengthening intramedullary nail, acute correction of his knee dormity and excision of his osteochondroma.