Spine I: Early-Onset Scoliosis

Early-onset scoliosis (EOS) presents many opportunities for trouble in diagnosis and treatment, even in the most experienced hands. Defined as the development of scoliosis before the age of 10 years,¹ EOS is associated with four general etiologies: congenital or structural, syndromic, neuromuscular, and idiopathic. Remember the most important factors for making decisions about how best to treat children with EOS are the age of the child and the rate of progression. One may observe a 60° curve or even larger curves in young children if progression is very slow. On the other hand, if a curve progresses rapidly and repeatedly, it may be time to intervene even in smaller curves.

EOS is different from adolescent scoliosis because of the relationship between lung development and spinal deformity. Spine deformity in young children can negatively affect lung development and function. Young children with large curves can develop severe respiratory issues that may affect quality and even quantity of life. We all have seen the graph showing how children with severe EOS have decreased life expectancy as they age. Knowing that natural history is often not great, a number of strategies have been developed to try to improve outcomes in these kids, although complications of treatment remain a challenge.²,³,⁴,⁵,⁶

As observation of a severe and progressive curve is likely to lead to a bad outcome, we face pressure to “do something.” In the past, spine fusion for young children with EOS led to a straight spine, and X-rays surgeons could be proud of. Unfortunately, early fusion also led to a thoracic spine, thorax, and lungs that were stunted in growth. As one could imagine, early fusion of the thoracic spine drastically hurts pulmonary function and is not recommended. “Growth-friendly” techniques such as distraction-based growing rods that are periodically lengthened offer the hope of promoting growth while controlling scoliosis. Unfortunately, we have discovered that anytime metal is put over a long segment of a child’s spine, spontaneous fusion is highly likely at somewhere around 5 years after implantation. In addition, growth-friendly techniques do not prevent crankshaft phenomenon, which makes sense if they slow the posterior growth but not the anterior growth. After seeing the problems that occur in these kids over time, many experienced (humbled) EOS surgeons temper expectations of families and surgeons.

Idiopathic Early-Onset Scoliosis

Infantile idiopathic scoliosis (IIS) describes that group of children generally diagnosed within the first 18 months of life, where no other cause is known. Our job in presumed idiopathic EOS is to make certain that there is no underlying cause of the EOS. Truly idiopathic EOS is a diagnosis of exclusion. This means a careful history and physical examination, close inspection of X-rays to look for subtle congenital differences, and in most cases, a screening MRI to rule out underlying intraspinal anomalies. Any change in the skin over the spine (hairy patch, significant dimple above the gluteal cleft, birthmark) should be a warning sign about a potential change underneath as well, prompting an MRI⁷ (Fig. 21-1).

When ordering an MRI of the cervical, thoracic, and lumbar spine for EOS, consider ordering limited sequences of only sagittal T1 and T2. This saves lots of time in the MRI, which may reduce anesthesia time in this at-risk population, with no loss in sensitivity.⁸

While progression may be the most important variable affecting the need for treatment, be aware that there can be some “false progression” in X-rays when children transition from lying down or sitting to standing radiographs. X-rays are really comparable only when performed in the same position, and the “clock
resets” when the first erect (sitting or standing) X-ray is taken. Warn parents about this to allay anxiety before the first erect X-ray.

Figure 21-1 Examples of common spinal dysraphism seen in some children with early-onset scoliosis. A: MRI demonstrating a large cervical syrinx with Arnold Chiari malformation. B, C: CT and MRI, respectively, demonstrating diastematomyelia (split cord malformation).

Children with idiopathic EOS under age 2 have a roughly 85% chance of spontaneous resolution within the first 18 months of life, and close observation is generally the most appropriate initial treatment. Mehta showed that children with a rib-vertebral angle difference (RVAD) greater than 20° and curves greater than 20° demonstrated higher rates of progression⁹ (Fig. 21-2). For patients who show continued progression past 12 to 15 months of age, MRI is obtained to rule out spinal dysraphism.

Congenital Scoliosis

Congenital scoliosis is classified as either a failure of formation (hemivertebra and wedge vertebra) or a failure of segmentation (block vertebra and unilateral bar) or both. If the hemivertebra has growth plates, it is called “segmented” and this
generally has a higher chance of progression. Highest rates of progression are seen with fully segmented hemivertebra (both growth plates intact), especially opposite a contralateral bar. Hemivertebra in the lumbosacral junction causes significant deformity, affecting the overall balance of the spine. This often requires surgical treatment.

Figure 21-2 A: Measurement of Mehta’s rib-vertebral angle difference (RVAD) can be calculated by subtracting the convex value (B) from the concave value (A) at the apical vertebra of a thoracic curve. B: X-ray showing small RVAD in a patient with idiopathic infantile scoliosis. RVAD less than 20° predicts a higher likelihood of spontaneous resolution of the scoliosis. (A: Adapted with permission from Lenke LG, Dobbs MB. Idiopathic scoliosis. In: Frymoyer JW, Wiesel SW, eds. The Adult and Pediatric Spine. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2004:337-361. Figure 15-3.)

The mesodermal layer that is responsible for vertebral body formation is also responsible for the urogenital, cardiac, and pulmonary systems. Perhaps because of this, there is approximately a 15% chance of a cardiac abnormality or renal abnormality in children with congenital scoliosis. Consider a cardiac echo and renal ultrasound in every child with congenital scoliosis. Spinal dysraphism (most commonly a tethered cord or Chiari malformation and less commonly a diastematomyelia) can be present in up to a third of patients with congenital spinal anomalies. An MRI requires general anesthesia in young children, so the downside of anesthesia to the developing brain must be considered. As long as there is no significant progression, or neurologic signs or symptoms, one may delay the MRI as long as there is regular assessment, but it should always be done before surgery, if there are signs or symptoms of neurologic problems, or a curve is rapidly progressive.¹⁰

TREATMENT

In general, we prefer to stall surgical treatment unless progression is constant and obvious and curves are greater than 50°, or an overall deformity is significantly progressing, such as a hemivertebra above the sacrum. In children less than 2 years of age, bone quality is so soft that anchors can plow through the bone, which can make intraoperative correction challenging, as well as lead to postoperative loss of fixation. Unsegmented vertebra generally demonstrates lower rates of progression, and surgery can often be delayed.

One of the few times surgical intervention is indicated immediately in the young child is in cases of a fully segmented hemivertebra opposite a unilateral bar. (This is a frequent test question.) We know this will progress, and we should prevent it from getting too much worse. If the child is too young and vertebrae too weak for a resection, consider a fusion in situ with cervical implants. You can always come back later and do a resection.

The precise anatomy of congenital scoliosis can be unclear. A CT scan can be very helpful in planning the surgical approach (sometimes with 3D model fabrication). When ordering CT scans in small children, make sure to limit the levels to the area of interest to decrease radiation. In an isolated hemivertebra, we generally perform a complete excision with limited two-level fusion (Fig. 21-3). Results are generally good although the chance of future surgery (generally related to progression above or below the limited fusion) has been reported to be up to 40%, especially in younger children. If a hemivertebra resection is performed, it is important to do a complete resection in all planes and to obtain as much segmental correction as possible. Hooks are sometimes used as an adjunct to obtain correction given the poor quality of pedicle bone.

A technical trick for closing a wedge after removing a thoracic hemivertebra is to place rib hooks above and below the removed segment, and compress the rib anchors, not the spine anchors (Fig. 21-4). Another option is to share the load with both pedicle screws and laminar hooks above and below the removed hemivertebrae. In young kids, laminar hooks often seem to plow less than pedicle screws. Instrumented hemiepiphysiodesis has been used in more extensive anomalies with reasonable, but with mixed results.

Figure 21-3 A, B: Congenital scoliosis characterized by progressive scoliosis around semisegmented hemivertebra. C, D: Treated with isolated hemivertebra resection with instrumentation. Bilateral instrumentation is more often used in most constructs. Complete resection of the hemivertebra is important to get correction, balance, and fusion.

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