Magnetic technology for early onset scoliosis
In October this year Ella Hammond was booked in to see her orthopaedic surgeon in Sydney for a procedure that had her mother excited but edgy.
The surgery was to lengthen the rods that had been implanted in the three-year-old’s back months earlier to help straighten a severe spinal deformity threatening to crush her tiny heart.
Ella has early onset scoliosis (EOS), a rare spinal disorder that affects about one in 1000 children aged under 10. Major surgery can correct the curve, but traditionally it requires repeated operations – sometimes up to 20 – to lengthen the rods to keep up with a child’s growth.
For Ella, however, the treatment was vastly different: her implanted rods grew inside her at the tap of a button with the whole procedure over in five minutes.
“It was amazing,” says her mother, Sheree Hammond, of Maitland near Newcastle. “Ella sat on the edge of the bed while her surgeon dialled up a few numbers on a hand-held device and ran it down her back.
“It sounded a bit like a vacuum cleaner, and you could actually see the rods extend under Ella’s skin.”
The Magec system used on the infant relies on “live” rods that can be magnetically lengthened by an external remote control. First used in Australia in 2011, the American technology is proving to be the most significant breakthrough in EOS in the past 50 years, with potential for further medical applications.
Rare earth magnets inside the Magec rods communicate with the hand-held controller allowing up to 4.5 centimetres of growth on a standard-issue rod before they need replacing.
“They have been transformative for young children with scoliosis,” says Australian Orthopaedic Association president Ian Incoll. “They circumvent the trauma and cost of multiple operations and lengthy admissions required with the older implant technology.”
Idiopathic scoliosis, which is characterised by a sideways curvature of the spine with no known cause, is broken down into many varieties.
The most common, adolescent idiopathic scoliosis, affects mainly teenage girls. While their curves should never be ignored, intervention in the form of bracing or surgery is only required in about one in 100 patients. And usually for cosmetic reasons or pain relief.
However, in small children the early onset variety can cause serious health and developmental problems if not corrected.
“It is rare but it is the most vexing scoliosis to treat,” says Ella’s surgeon, Dr Angus Gray, who is attached to Sydney Children’s Hospital at Randwick. “The problem we have is that scoliosis is a spinal deformity driven by growth, and the more growth you have left, then the more opportunity for that deformity to go bad.
“Some of these little kids will die in their middle adult years because the normal development of their hearts and lungs has often been constrained.”
The Magec system was specifically designed for this age group with the help of world-renowned pioneer in advanced treatments for scoliosis, Dr Behrooz Akbarnia, who is based in California.
Gray had met Akbarnia at an orthopaedic conference in the United States in 2009 and shared his enthusiasm for the innovative magnetic technology.
As it turned out, Gray was able to use the Magec system for the first time in 2011, three years before the Food and Drug Administration in the US gave its long-awaited approval.
“I had been in contact with New Zealand surgeons who had put in a few already,” he says. “On that basis, I thought it reasonable to recommend the new rods to the parents of my first patient.”
With special circumstances approval from the Therapeutic Goods Administration (TGA), Gray surgically implanted the Magec rods into a Melbourne eight-year-old.
“I was sort of intrigued,” says Gray, who had been operating with the old rods since 2000. “Josh’s curve was severe, around 80 degrees, and it had not responded to bracing or plaster cast.
“He turned up months after the surgery with his parents … I dialled up how much length we wanted to put on his back, the machine made a funny whirring noise and you can see the numbers coming up on the LCD display – it went fine.
“Josh said what is commonly said by other patients since, that he felt a slight odd burning sensation between his shoulder blades, but it quickly disappears. I took him down the corridor to X-ray and you could see the rods had elongated. It was very, very satisfying.”
Josh is now 14, and only weeks ago reached an important milestone when he was transferred to a fusion system.
“The rods have done their job and the fusion will give Josh better and stronger correction for the final phase of growth,” says Gray.
One of the difficulties for surgeons operating on young children with scoliosis, whether using old or the new “live” rods, is bending the rod to the shape needed when these children are very small and have stiff spinal curves.
“The added challenge with the Magec rods is that you can’t bend the section that holds the motor,” says Gray. “That section is about 120 millimetres long, which is quite long in a little back, so you have to be a bit clever on how you bend the rod above and below that section.
“After each bend we have to put the magnet back on the rod and spin it to confirm the rod mechanism is still intact so it takes a lot of fine-tuning to ensure it will do the job when required.”
Of Gray’s eight young patients who have so far received the implants, three have had to have revision surgery: one because the hooks holding the rod had pulled out, one failed to telescope and the other had jammed.
“I can bear those failures because it’s much better than repeatedly taking these kids back to theatre for a two-hour lengthening operation and two or three days in hospital,” he says.
“It was awful on the kids because they remember.
“Under the old system surgeons had to repeatedly cut through old scar tissue, and you have to create more scar tissue every time you go back which increases the chance of infection.”
Despite Magec’s advantages, the cost – $22,000 a rod – did not initially excite the health insurance sector, but they soon came on board.
“Magec rods are far more cost-effective when you consider a five-year-old needing this system until he or she is 11 will now undergo about two rod replacements compared to about 11 or 12 lengthenings of the past,” says Gray.
California-based NuVasive, which has taken over from Ellipse Technologies – the first company to adapt the magnetic technology into a reproducible and commercially viable product – says the Magec system is a work in progress.
“We are continually working to make the devices smaller and less invasive, which would potentially decrease the need for replacement,” says senior director of marketing Ross Sylvia.
He says the technology is expected to have further applications and is already being used in non-invasive limb-lengthening procedures for the femur and tibia in cases of chronic fractures, congenital abnormalities and malunions.
Meanwhile, little Ella Hammond’s world has opened up beyond her mother’s expectations.
“Ella’s a different kid now because after three years of hell she’s relatively free of pain and has been fitted with special shoes to help her learn to walk, something we never thought she’d do,” Sheree says.
“Our hope is to have her walk through the door when she starts kindy in just over a year, and her surgeon believes that’s achievable.”
This article was first published in the print edition of The Saturday Paper on Nov 5, 2016 as "Great lengths". Subscribe here.