Tension banding or guided growth is a new surgical technique for the treatment of angular deformities. Angular deformities include too much outward bowing of the bones that make up the knee joint or an excess inward angle we refer to as being “knock-kneed.” Guided growth is replacing the previous “gold standard” treatment of surgical osteotomy.
Instead of cutting a piece of bone out and realigning the affected bones and joints (that’s what an osteotomy does), a special device called a flexible tension band is used instead.
The band spans each side of the knee joint and is held in place with two screws. The band doesn’t prevent bone growth but it slows growth down. This treatment makes it possible to slowly but safely correct the alignment problem. This can be done without surgery and without halting growth altogether.
The flexible band and screws can be taken out when the child has reached neutral alignment and/or full skeletal maturity. Skeletal maturity means the growth plates at the ends of the bones have closed, and the child is no longer growing.
Sometimes the guided growth system is removed when the bones are in neutral alignment but the child is still growing. If X-rays show the problem (angular deviation) is coming back, the procedure can be repeated.
X-rays are also used to estimate bone growth and plan the guided growth process. The goal is to find the most optimal time while there is still enough bone growth left to make a difference. At least one year of bone growth left is ideal. It may be best to use this approach earlier than later but the exact best timing is still unknown.
In order to avoid recurrence, orthopedic surgeons look for any other problems that might contribute to the angular deformity. They check both sides as well as the joints above (hips) and below (ankles and feet). The child’s gait (walking) pattern is examined and corrected.
Early results of the guided growth system are positive. The technique is much less invasive than surgical osteotomies. Unlike an osteotomy (which is permanent), guided growth is reversible (by removing the band). No bone is lost or destroyed with guided growth. In essence, bone growth is only “restrained” or slowed down.
We don’t have long-term studies yet to show what happens over time using this management technique. Children grow at different rates and that variability may affect the long-term results. Likewise, putting weight on the leg alters bone growth. More active children may have a different final outcome than less active children.
Predicting bone growth is not an exact science and can be inaccurate. The effect of the guided growth system on the patella (knee cap), ligaments, and other surrounding soft tissues has not been assessed either. These are all factors that will be investigated and studied in depth. The potential for correction of angular deformities without osteotomies makes this technique worth pursuing.