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If your child has a leg length discrepancy (LLD) that is expected to be more than 2cm at the time he/she reaches their final height, your surgeon may offer surgery to shorten the bone by stopping growth on the longer side. But another option is to have the shorter leg lengthened with an internal lengthening device.^1,2

How Is Bone Lengthening Surgery Done?

To lengthen a bone, the surgeon must do an osteotomy, which is a complete cut in the bone. The second stage involves slowly pulling apart the two bone ends so as the body ties to heal the bone cut new bone grows in the space between them. This process of creating new bone is called distraction osteogenesis in medical terms.^3,4

The first devices to be used for bone lengthening, and still applied today, are the external fixators. They, as the name indicates, are a frame that stays outside the body, being attached to the bone through pins and wires. Another more modern option is to use an internal fixation method. In this method, the surgeon inserts an intramedullary (IM) nail, like the Orthofix Fitbone™ Intramedullary Lengthening Nail, completely inside the bone after performing the osteotomy.

The growth of new bone takes time, so the bone ends have to be separated slowly, typically 1mm/day or slower. To achieve this, the lengthening IM nails have a small motor inside to power the telescopic nail. When activated, the motorized IM nail slowly separates the two bone ends to allow the creation of new bone in the gap, thus lengthening the bone.³ When it is not activated, the IM nail remains in a fixed position, supporting the operated bone.

What Happens After Surgery?

Right after surgery, there is a latency period for recovery of about 1 week. After this, the bone lengthening phase starts, usually a total of .75-1 mm of bone separation (distraction) per day. For this, a controller is given to the patient (or the parents), to activate the nail and control the lengthening, which is performed in several sessions per day.^5,6

The lengthening phase will last several weeks or months, depending on how much the bone has to grow. During this stage, the child will use crutches or a walker as they should not put their entire weight on the operated leg. However, they do not need a cast or immobilization and are encouraged to move their joints. There will be frequent visits to your surgeon’s clinic to be evaluated and obtain x-rays. Regular physical therapy is mandatory during the lengthening phase.⁵

Once goal length is achieved, the daily lengthening sessions are stopped and you enter the consolidation phase, when the new bone gradually fills in and strengthens over time. Office appointments become less frequent, but physical therapy continues to strengthen muscles and prevent contractures. Your child will be permitted to start fully weightbearing during the consolidation phase. About 1 year after the radiographs show that the new bone is fully consolidated (united and solid), the IM nail can be safely removed from the bone.⁵

References

1. Vogt B, Gosheger G, Wirth T, Horn J, Rödl R. Leg Length Discrepancy- Treatment Indications and Strategies. Dtsch Arztebl Int. Jun 12 2020;117(24):405-411. doi:10.3238/arztebl.2020.0405
2. Gurney B. Leg length discrepancy. Gait & Posture. 2002/04/01/ 2002;15(2):195-206. doi:https://doi.org/10.1016/S0966-6362(01)00148-5
3. Wynes J, Schupp A. Assessment of Pediatric Limb Length Inequality. Clinics in Podiatric Medicine and Surgery. 2022/01/01/ 2022;39(1):113-127. doi:https://doi.org/10.1016/j.cpm.2021.09.004
4. Thomas A, Round J. Basic principles of lower limb deformity correction. Surgery (Oxford). 2023/04/01/ 2023;41(4):255-261. doi:https://doi.org/10.1016/j.mpsur.2023.02.015
5. Dahl MT, Georgiadis AG, Morrison SG. Motorized Internal Limb Lengthening: An Updated Review. Journal of the Pediatric Orthopaedic Society of North America. 2020/05/01/ 2020;2(1):67. doi:https://doi.org/10.55275/JPOSNA-2020-67
6. Pejin Z. Femoral lengthening in children and adolescents. Orthopaedics & Traumatology: Surgery & Research. 2017/02/01/ 2017;103(1, Supplement):S143-S149. doi:https://doi.org/10.1016/j.otsr.2016.05.020