» Why Do Growing Rods Used for Scoliosis Break
Why Do Growing Rods Used for Scoliosis Break

Children with severe scoliosis (curvature of the spine) may have surgery to insert a rod along the spine. The rod helps keep the spine straight. It's actually a growing rod, which means it operates like a telescope and can lengthen as the child grows. The vertebrae are not fused so the rod spans long sections of the spine.

One of the main problems with growing rods is that they fracture (break). To understand more about growing rod fractures and ways to prevent problems, a group of 10 pediatric orthopedic centers put together a growing rod database. They combined all the information they had from 327 children treated with growing rods throughout all 10 centers.

By putting information about each case into a computer database, they could study and analyze the data. In this study, they looked for risk factors for rod breakage. The hope was to find ways to prevent this complication.

The first thing they noticed was the percentage of children who experienced growing rod fractures: 15 per cent. Then by comparing children with breakage against children without rod fractures, they isolated the risk factors. Here's what they found:

  • Children with scoliosis as a part of other problems (called a syndrome) had the highest rate of fracture. This was much higher than for children with scoliosis as a result of a neuromuscular problem such as cerebral palsy or muscular dystrophy.
  • Children who could stand upright and walk had a higher risk of rod fracture.
  • Children with single rods (only on one side of the spine) rather than dual rods (placed on both sides of the spine) were at greater risk for rod breakage.
  • When dual rods broke, both sides fractured at the same time in 26 per cent of all cases.
  • Titanium rods break less often than stainless steel rods.
  • Thicker rods were less likely to break compared with thinner diameter rods.
  • This is actually the first study to examine growing rod breakage. All manner of potential risk factors were considered (e.g., age, sex, weight, use of bracing before or after surgery, level of rod fracture, location and severity of the scoliosis). But the ones with the greatest significance are listed above.

There was one other risk factor not previously mentioned. Children who had repeat fractures were much more likely to have a single rod in place (13 per cent for single rods as opposed to two per cent for dual rods).

Fractures didn't usually occur right away. Some children did have a rod fracture as early as four months after rod insertion. But the more times the rod was lengthened, the greater the risk for breakage.

Most of the fractures occurred at places along the spine where the rod was connected to the bone. When they took a closer look, they saw that the type of connector made a difference. Rod fractures occurred more often with hooks (as opposed to screws or hooks and screws combined).

Age, weight, and severity of scoliosis did not appear to be risk factors. Wearing a brace at any time before or after surgery did not provide protection from rod fractures.

What can be done to prevent this common complication? The authors don't know yet without further study but they offer some thoughts. It's possible that replacing rods sooner in the process might help. The downside of that suggestion is the added surgery and increased risk of other complications like infections and blood clots.

Finding a better way to attach the rods might help. Using thicker, dual titanium rather than single stainless steel rods may be advised. Since metal fatigue may be part of the reason rods break, studies to find a better rod design might be helpful.

Surgeons are advised to consider making gradual bends in the rod rather than single angles when adjusting the rods to the curves. It might be better if broken rods were replaced rather than repaired. And it may be a good idea to warn families about the risk of complications including rod fracture.

The authors point out several other areas that were not specifically studied in this database project. One was the child's compliance with bracing. It's possible that bracing does provide some protection but we won't know that unless actual wearing is confirmed and compared with rod fracture rates.

Not all centers collected the same information. So some things like curve flexibility (or rigidity), curve location, complications, and specific diagnosis were not compared between the group of children with and without rod fractures. But for a start, this database did provide some very helpful information about incidence and risk factors for growing rods used in the treatment of severe scoliosis in children.

Reference: Justin S. Yang, MD, et al. Growing Rod Fractures. In Spine. September 15, 2011. Vol. 36. No. 20. Pp. 1639-1644.