Sept. 23, 2017
Pediatric spine deformity encompasses a range of conditions, from mild scoliosis to complex anatomical abnormality, in patients from infancy to adulthood. Treatment options — casting, growing rods and surgical correction — pose challenges for young, growing patients and for physicians striving for optimal outcomes that avoid complications and the need for future surgery.
Mayo Clinic in Rochester, Minnesota, has a comprehensive pediatric spine deformity treatment program with state-of-the-art spinal care for children from birth to adulthood. "Mayo is unusual in providing the full complement of care with a high degree of specialization. Our surgical teams are orthopedic pediatric teams, not general pediatric teams," says A. Noelle Larson, M.D., a consultant in pediatric Orthopedic Surgery at Mayo Clinic's campus in Minnesota.
"For any type of spine deformity, we have the resources and staff to provide the highest level of patient experience in terms of safety, comfort and outcomes," adds William J. Shaughnessy, M.D., a consultant in pediatric Orthopedic Surgery at Mayo's Minnesota campus.
Elongation, derotation, flexion (EDF) casting — also known as Mehta casting — is used to treat early-onset scoliosis in infants and children up to age 4. The treatment utilizes a custom-made thoracolumbar cast that acts simultaneously in the frontal, sagittal and coronal planes. Early-onset scoliosis can sometimes spontaneously resolve. "But based on criteria such as the severity of the curve and the rib vertebra angle difference, we can identify kids whose curves are going to get worse and who can benefit from this casting," says Todd A. Milbrandt, M.D., a consultant in pediatric Orthopedic Surgery at Mayo's Minnesota campus.
About half the children who have EDF casting achieve a curve of less than 20 degrees after two years of treatment. Occasionally, outcomes are dramatic. Dr. Larson cites the example of a Mayo Clinic patient with a 75-degree curve who had EDF casting from age 12 months to 3 years. "She's now 7, she's not in a brace and her curve is under 20 degrees," Dr. Larson says.
More frequently, EDF casting allows surgery to be postponed until the child is older. "Often scoliosis will progress 20 to 30 degrees per year without treatment," Dr. Larson notes. "So even if we start with a 70-degree curve and with casting we get it down to 40 degrees, that's a success."
Magnetic growing rods
Growing rods have become the mainstay of treatment for children with scoliosis. After initial surgical implantation, patients typically must undergo several additional surgeries to lengthen the rods to accommodate growth.
Magnetically controlled growing rods can be adjusted externally, avoiding the need for repeated surgeries. The rods incorporate small, magnetic gear mechanisms; a magnetic actuator is passed over the rods to lengthen them.
"Adjusting traditional rods may be an outpatient procedure or might require an overnight hospital stay. But it's still surgery that's needed every six to nine months," Dr. Larson says. The procedures are especially problematic for children with poor heart or lung function due to conditions such as spinal muscle atrophy.
In a study published in the December 2015 issue of Spine, Dr. Larson and colleagues found that although magnetic rods are initially more costly than conventional rods, the costs equalize after about three years, due to the lack of repeat surgeries. "The magnetic rods have a relatively high revision rate, like regular rods," Dr. Larson says. "But this new technology has been a real game-changer in terms of patient comfort."
Exposure to diagnostic radiation during childhood poses enhanced risk of breast cancer in female patients with scoliosis, and has been associated with other cancers. Mayo Clinic was among the first centers in the United States to offer EOS, a low-radiation imaging technology.
In a study of skeletally immature patients with scoliosis published in the March 2015 issue of Spine Deformity, the pediatric orthopedic group worked closely with Mayo Clinic's radiation physicist to determine that an EOS posteroanterior (PA) radiograph results in four times less radiation to the thyroid and eight times less radiation to the breasts than conventional X-rays. Radiation to the breast and thyroid is higher with the anteroposterior view, so the researchers recommend using the PA view in the EOS machine for standard imaging protocols.
In addition to low radiation, EOS provides high-quality images. "EOS images are more uniform than our previous low-dose filtered X-rays and provide us with more-accurate measurements," Dr. Shaughnessy says. "And by reducing radiation doses, we can in theory reduce that risk of cancer for our patients."
Intraoperative imaging and navigation
For complex spinal surgeries, Mayo Clinic orthopedic surgeons can use intraoperative CT-guided navigation. The system provides real-time, multidimensional intraoperative imaging of a patient's anatomy.
In a study published in the April 2016 issue of Clinical Spine Surgery, Mayo Clinic researchers found that intraoperative image-guided navigation resulted in a 97.8 percent rate of accurate screw placement in patients ages 10 years or younger. Previous studies have noted that up to 15 percent of free-hand pedicle screws in children are reported to be malpositioned.
"These technical innovations in intraoperative imaging and navigation are very helpful for placing screws more safely and efficiently," says Anthony A. Stans, M.D., a consultant in pediatric Orthopedic Surgery at Mayo's Minnesota campus.
To minimize radiation exposure from intraoperative CT, Mayo Clinic developed a protocol for pediatric patients using a lower radiation dosage than that recommended by the manufacturer. In the September 2016 issue of Journal of Pediatric Orthopaedics, Mayo researchers reported that the pediatric protocol reduces radiation from intraoperative CT to less than one-fourth the mean annual natural background radiation. "We can obtain an intraoperative CT scan for about the same radiation as two scoliosis X-rays, with acceptable quality of images," Dr. Larson says.
Utilizing CT scans and 3-D printing technology, Mayo Clinic has the capability to construct precise 3-D models of patients' spines. "We use these models for patients with unusual abnormalities that are difficult to understand even with a 3-D image on a screen," Dr. Stans says.
Additional software allows surgeons to place virtual screws in a screen image of a patient's spine and then print a 3-D model of the spine incorporating those screw placements. "This helps us to do the surgery more safely and efficiently, with shorter time under anesthesia and better outcomes," Dr. Stans says.
Expertise through teamwork
Mayo Clinic's broad expertise allows it to provide innovative patient care. Radiologists are key members of the treatment team, providing images and at times physical models that guide treatment plans and surgery. Anesthesiologists have devised a special protocol for pediatric spinal surgeries.
"Our collaborative approach provides maximum safety, improves our patients' comfort postoperatively and markedly reduces their length of hospital stay," Dr. Stans says. "At Mayo Clinic, we have like-minded people working together on complicated cases to meet the needs of patients."
For more information
Su AW, et al. Magnetic expansion control system achieves cost savings compared to traditional growth rods: An economic analysis model. Spine. 2015;40:1851.
Luo TD, et al. Cumulative radiation exposure with EOS imaging compared with standard spine radiographs. Spine Deformity. 2015;3:144.
Luo TD, et al. Accuracy of pedicle screw placement in children 10 years or younger using navigation and intraoperative CT. Clinical Spine Surgery. 2016;29:E135.
Su AW, et al. Switching to a pediatric dose O-arm protocol in spine surgery significantly reduced patient radiation exposure. Journal of Pediatric Orthopaedics. 2016;36:621.