Intramedullary distraction for lower limb lengthening

The condition

3.1 People may have different limb lengths because of trauma or infection (acquired) or, more rarely, because of hypoplasia or dysplasia of the femur or tibial (congenital). Unequal leg length can cause a limp and limit functional ability.

Current treatments

3.2 Lengthening of an abnormally short lower limb can be done using an external fixation device. This exerts force along the long axis of the bone to induce new bone formation (distraction osteogenesis). Problems with external fixation include: infection of the pin tracts, pain, hip and knee subluxation or dislocation, angulation, bone deformity and neighbouring joint stiffness. People may also find that external fixation devices are impractical and aesthetically unacceptable. Often, once the external fixation is removed, the new bone is augmented by either an internal plate fixation or an intramedullary nail.

The procedure

3.3 Intramedullary distraction systems are used for managing fractures. Once inserted and fixed they can be mechanically lengthened over time using different techniques. The aim is to lengthen the bone in a controlled manner.

3.4 With this procedure, under general anaesthesia, an osteotomy is done while avoiding damage to the periosteum and its blood supply. The adjustable intramedullary nail-like device is then implanted into the intramedullary space. Its proximal and distal sections are fixed to the relevant section of the bone with sterile locking screws. Once implanted and fixed, the device can be adjusted in length to provide an appropriate amount of compression and allow bony alignment at the osteotomy site. It exerts a force along the long axis of the bone, which stimulates new bone formation (distraction osteogenesis) in the gap, causing bone lengthening. Over days, weeks or months, sequential distractions are used to produce the target limb length.

3.5 Different devices achieve distraction in different ways. For example, some work mechanically by releasing a preloaded spring or using a motor driven extension. Others are non-invasive and use an external electromagnetic device.

3.6 Soon after the procedure, with help from the physiotherapy team, people are able to partially weight bear. The intramedullary device then remains implanted until bone consolidation is complete. When there is radiological evidence of adequate bone consolidation across the gap, full weight bearing is possible. The device is then usually removed using standard surgical techniques.