Use of casting, ideal timing of intervention, accurate syndromic diagnosis can lead to optimal outcomes
In considering treatment strategies for young patients with early onset scoliosis, orthopaedic spine surgeons must think "beyond the curve," said Suken A. Shah, MD, during the Scoliosis Research Society (SRS) session of the Federation of Spine Association's 2017 Specialty Day.
The SRS has changed its definition of early onset scoliosis to include all the deformities diagnosed before age 10 years, said Dr. Shah, who is the division chief of the Spine and Scoliosis Center at Nemours Alfred I. duPont Hospital for Children in Wilmington, Del.
"Most of these patients are very young with a great deal of remaining growth," he noted, "and the patient group is heterogeneous, with causes that may be congenital, idiopathic, syndromic, or not classifiable."
"These conditions are challenging," asserted Dr. Shah. "There is a natural history of progressive deformity that causes pulmonary compromise. We have to think of these conditions in a different way—beyond the curve. We should avoid just looking at the spine and try to appreciate everything else."
Dr. Shah referred to a description of spinal column growth offered by Dimeglio* and indicating that from birth to age 5, T1-S1 length will increase by about 10 cm. This works out to a spinal column growth velocity of about 2 cm/year from birth to 5 years. The remaining growth in T1-S1 from age 5 years to skeletal maturity is about 15 cm. As a result, Dr. Shah noted, a long spinal arthrodesis at 5 years of age could cause a sitting height deficit of 15 cm and result in significant pulmonary impairment. He also showed new data from James O. Sanders, MD, indicating that while T1 to S1 growth is 1.5 cm/year in childhood, it is 2.5 to up to 3 cm/year during the growth spurt—"much higher than shown in prior cross sectional studies."
"If we are intervening in the 5- to 10-year age group, we have an opportunity to catch up with growth," Dr. Shah said. "Newer data show there is a lot of variability on the low end and the high end, but during peak height velocity, both girls and boys are very predictable and the variability is small. We can time their peak height velocity in a very narrow band. And we can perhaps intervene just before that or during that period, when we know that these deformities are going to progress."
Intervening at the right time, he concluded, "has important implications for growth modulation. We can actually program the lengthening intervals and the lengthening amount as we go forward in a much more precise and customized way rather than the 'one for all' approach we have used in the past."
The pulmonary priority
Issues involving thoracic growth and potentially serious pulmonary implications that can arise are important considerations in treating patients with early onset scoliosis, Dr. Shah said.
Patients undergoing early fusion, Dr. Shah said, have poor pulmonary function, shorter spines, more pain, and poorer quality of life. Several studies document the various dangers of ignoring growth associated with early fusion. "Early fusion is demonstrated in studies to be terrible for pulmonary function," Dr. Shah said, noting that the data show that the more that is fused and the higher the fusion, the worse the effects—ie, the more progressive the decline in forced vital capacity.
Given its effect on the thorax, "early onset scoliosis is a life-threatening concern," Dr. Shah said. "It's not a quality-of-life issue or a question of whether these patients can return to sports. It's about keeping them alive, because progressive deformity can create thoracic insufficiency syndrome by inhibiting spinal and chest wall growth. The natural history of these patients is terrible—worse than asthma, juvenile rheumatoid arthritis, or congenital heart disease."
At birth, he explained, the thoracic volume is about 6.7 percent of an adult's thoracic volume. At 5 years, the thoracic volume is about 30 percent, and at 10 years, the remaining thoracic volume is about 50 percent of an adult."
"At age 5, the remaining sitting height is about 35 percent and the remaining growth of the thorax is about 70 percent," Dr. Shah said. "The volumetric growth of the thorax—'the fourth dimension of the spine'—is very important. Because the thoracic cage doubles in volume after puberty, monitoring its development is critical in avoiding thoracic insufficiency syndrome."
In view of a study by Karol, he said, "Our goalpost now is that a T1 to T12 height of 22 cm results in near-normal pulmonary function. So when is the road over for some of these lengthening patients and growth modulation patients? Perhaps when they get a spinal height T1 to T12 of 20 cm."
Goals of treatment, he said are to "control curve progression and avoid fusion so that we can optimize pulmonary function, maintain spinal growth, limit complications, and facilitate the care of the patient and the family so we can improve their quality of life."
To accomplish these goals in a safe and predictable manner, a systematic approach is important, Dr. Shah said. Various studies may be ordered. "In addition to full length standing X-rays, we may get an MRI to rule out spinal cord dysraphism," he noted. "Occasionally we'll get a computed tomography scan to outline complex vertebral anatomy." However, he said, one should be cognizant of a child's exposure to ionizing radiation.
According to Dr. Shah, surgeons should collaborate with medical colleagues to identify comorbidities and manage them throughout the intraoperative process to optimize pulmonary function.
"Identify syndromes and get consults from medical partners," said Dr. Shah, who typically holds a preoperative conference with medical colleagues to optimize the patient. "In the operating room (OR), you need to have your 'A team.'" The team should be prepared for positioning challenges, neurologic monitoring changes, and excessive bleeding, with intravenous access, blood products, warmers, and antifibrinolytics.
Know the syndrome, consider the cast
When the surgeon makes a diagnosis of a specific syndrome, he or she should be knowledgeable about that condition, including comorbidities, risks, and predilections, as well as orthopaedic and other medical manifestations of the syndrome. A dysmorphic child with "undiagnosed syndrome" should be considered for a consultation with a geneticist, Dr. Shah said. "I get concerned about a patient who shows up looking dysmorphic but never really had a diagnosis."
Syndromic early onset scoliosis may involve Marfan, neurofibromatosis, Goldenhaar, arthrogryposis, osteogenesis imperfecta, skeletal dysplasias, or other named syndromes, a number of which are associated with a small thorax and stiff curves. "With syndromic scoliosis, we need to prepare and optimize the patient for surgery," Dr. Shah said. "They have stiff curves, they bleed more, and they typically don't have reliable neuromonitoring signals in the OR."
Casting has reemerged as a treatment for early onset scoliosis, Dr. Shah explained. The typical cast has a derotation component and a posterior window to allow the concave ribs to derotate posteriorly and achieve correction in the axial plane (Fig. 1). The cast is applied using the elongation, derotation, and flexion technique, and anterior and posterior windows are made in the cast to allow abdominal/chest expansion and curve derotation. "Children are not disabled in a cast; they work around it."
"The best results with casting occur when the patient is treated early, has flexible curves, and doesn't have a syndrome," Dr. Shah explained. "In patients who don't meet these criteria, we've been successful in delaying intervening treatment and pushing growth modulation out a little farther. There are data suggesting that delaying surgery is of benefit in these patients. These [older] kids get bigger, have better nutritional status, and gain weight. Their complications are decreased."
Mechanical strategies may involve posterior distraction with growing rods. Every 6 months, rods are distracted, as the spine grows. "Dual growing rods do better than single," Dr. Shah said. "Submuscular rods do better than subcutaneous, but we still have many issues."
Growth is guided along rods with a Luque trolley and sliding screws procedure. Convex anterior growth is slowed with stapling, tethering, and arrest of neurocentral junction growth. Dr. Shah noted that the use of growing rods may be associated with the following:
- improved sagittal balance
- decreased thoracic kyphosis after index surgery and increased thoracic kyphosis between post–index surgery and latest follow-up
- increased proximal junction kyphosis
- no significant change in lumbar lordosis
- no deterioration in sagittal plane parameters caused by the number of lengthenings
Complications with rods may include infection, rod breakage, anchor failure, and failure to achieve lengthening, he noted.
Surgeons should be mindful of issues involving anesthesia, repeated exposure to anesthetic agents and effects on the developing nervous system and other functions, said Dr. Shah, noting that there is evidence that repeated surgery and anesthesia may cause posttraumatic stress, increased anxiety, cognitive deficits, and increased incidence of attention deficit disorder.
"This is not just related to surgical actions, but also applies to sedation of children for tests and other procedures." he noted. To reduce anesthetic episodes, he recommended use of technology that does not involve surgery to distract the rods. "What really has changed the game are magnetically controlled growth rods (MCGRs)," he added, "which don't need surgery to lengthen." These devices were approved by the U.S. Food and Drug Administration in 2014 and have become a mainstay, he said, and they "enable us to lengthen the spine—without anesthesia—while the child is doing something such as playing on a smart phone, and confirm lengthening under ultrasound" (Fig. 2).
On timing of surgery, there is "not a lot of consensus," Dr. Shah said. "Some surgeons say a child should be at least 7 years old and have at least a 60-degree curve. But with younger children with greater deformities, we may be forced to operate earlier." In practice, patients who undergo surgery have a mean curve of 73 degrees ± 20 and are age 6.0 years ± 2.5 years (source: Growing Spine Study Group). The common reasons surgery is performed include curve rigidity, brace/cast intolerance, and syndromic diagnosis.
Dr. Shah acknowledged some controversies regarding variability in decision making and noted that gaps in guiding evidence exist. In addition, questions linger regarding when treatment is properly concluded, timing of rod lengthening, whether a final fusion is necessary, and indications for use of spine-based versus rib-based anchors. "With lengthening, we don't know how often to do it and when to stop, but we are trying to get there on a customized basis with more data," he said.
Terry Stanton is the senior science writer for AAOS Now. He can be reached at firstname.lastname@example.org
- Summarizing current management trends for early onset scoliosis, Dr. Shah advised the following:
- Conduct a multimodality workup, involve medical colleagues, and delay surgery with casting or bracing for as long as possible.
- Radiation and anesthetic exposure should be minimized, and "later implantation is better."
- Lengthening of T1-T12 should be accomplished to improve pulmonary function, and complications may be reduced with use of dual rods.
- The number of surgeries for lengthening may be reduced with the use of sliding screws and with magnetically controlled growth rods.
- Dimeglio A, Bonnel F, Canavese F: Normal growth of the spine and thorax, in Akbarnia B, Yazici M, Thompson GH, eds: The Growing Spine New York, Springer 2009, pp 11–41.
- Getting info from Sanders for a reference. But may just have to use "data from James Sanders"
- Karol LA, Johnston C, Miladenov K, Schochet P, Walters P, Browne RH: Pulmonary function following early thoracic fusion in non-neuromuscular scoliosis. J Bone Joint Surg Am 2008;90(6):1272-1281.
- Shah SA, Karatas AF, Dhawale AA, et al: The effect of serial growing rod lengthening on the sagittal profile and pelvic parameters in early onset scoliosis. Spine (Phila Pa 1976) 2014;39(22):E1311-1317.