Pediatric Spine Disorders and Trauma

A. Noelle Larson, MD

Lindsay M. Andras, MD

Dr. Larson or an immediate family member serves as a paid consultant to or is an employee of Medtronic and serves as a board member, owner, officer, or committee member of the Pediatric Orthopaedic Society of North America and the Scoliosis Research Society. Dr. Andras or an immediate family member is a member of a speakers’ bureau or has made paid presentations on behalf of Biomet, Medtronic, and Nuvasive; serves as a paid consultant to or is an employee of Biomet, Medtronic, Nuvasive and Zimmer; has stock or stock options held in Eli Lilly; and serves as a board member, owner, officer, or committee member of the Pediatric Orthopaedic Society of North America and the Scoliosis Research Society.

ABSTRACT

Spinal deformity is frequently encountered in children. Adolescent idiopathic scoliosis is the most common form of scoliosis, but scoliosis can also present in younger children and in children with congenital vertebral anomalies or associated syndromes. Treatment includes observation, bracing, and surgery. Specialized techniques may be needed in immature children to preserve growth, particularly in children younger than 10 years. Spondylolysis is most commonly seen in ambulatory athletic patients. Although pars repair or fusion surgery may be indicated on occasion, most patients respond to conservative management. High-grade spondylolisthesis may necessitate surgical treatment due to concern for progression and neurologic deterioration. Finally, trauma can result in vertebral fracture and, in rare cases, spinal cord injury. An understanding of pediatric spinal deformities is essential to provide appropriate care, treatment, and referral.

Keywords: congenital scoliosis; pars defect; spine deformity; spondylolisthesis; spondylolysis

Introduction

Adolescent idiopathic scoliosis is the most common spine condition found in children. However, familiarity with other traumatic and nontraumatic causes of spinal deformity is essential for prompt diagnosis, treatment, and referral. Early-onset scoliosis can be life threatening, as can scoliosis associated with neuromuscular conditions. This section will summarize recent developments in the treatment of scoliosis, kyphosis, and spine deformities associated with trauma.

Early-Onset Scoliosis

Early-onset scoliosis (EOS) is defined as a spinal curvature in the coronal plane of greater than 10° with onset under 10 years of age. Children with EOS are at risk for impaired pulmonary function from their spinal deformity due to constraints on the thorax during a critical time of lung development.¹ The natural history of untreated EOS is associated with significant morbidity and potential for cardiopulmonary compromise, including respiratory failure and cor pulmonale.

A Swedish study evaluating children treated between 1927 and 1937 compared expected population death rates and demonstrated more than double the mortality rate by the age of 40 years in patients with EOS compared with that of the general population.² Early spinal fusion was once routine in children with severe progressive EOS, which addressed the scoliosis, but limited spine and thoracic growth resulting in poor pulmonary outcomes.³ Currently, the objective of EOS treatment is to maximize growth of the spine and thorax by controlling the spinal deformity, with the goal of promoting normal lung development and pulmonary function. This population is also challenging due to the diverse and often medically complex nature of these patients. The etiology of the spinal deformity may be idiopathic, associated with underlying systemic syndromes, secondary to a neuromuscular condition, or caused by a structural congenital spinal
deformity. This heterogeneous group of patients may require a variety of treatments. Vitale et al have developed the C-EOS classification system to aid in studying these patients and optimizing their management⁴ (see Figure 1).

Figure 1 Early-onset scoliosis (EOS) classification system by Vitale et al takes into account etiology, curve magnitude, kyphosis, and rate of progression.

Infantile Idiopathic Scoliosis

Unlike adolescent idiopathic scoliosis, infantile idiopathic scoliosis (IIS) is more common in boys (1:1 male to female ratio), is most often a left thoracic curve, and improves spontaneously in the majority of cases. While 74% to 92% of early-onset idiopathic scoliosis in children younger than 2 years spontaneously resolves, some of these curves do not improve and are in fact progressive. Mehta identified predictors of progression including: Cobb angle >20°; rib vertebral angle difference >20°; and rib phase 2 (rib head overlaps the vertebral body). In cases that do not have these risk factors for progression, patients can be observed and reassessed in 6 months.

In cases with these predictors of progression or those who have already demonstrated clinical or radiographic progression, the initial assessment is confirming that the scoliosis is in fact idiopathic. An MRI of the entire spine is warranted to evaluate for any intraspinal anomalies such as a tethered cord, syrinx, or Chiari malformation that may be associated with the scoliosis. Intraspinal anomalies have been shown to be present in 13% to 22% of patients with presumed idiopathic infantile scoliosis.⁵^,⁶ Both Pahys and Dobbs et al reported that a neurosurgical intervention was indicated in 70% of the cases in which these anomalies were identified. Consequently, managing the concomitant intraspinal pathology is of utmost importance, as it may prevent potential neurologic problems in addition to halting progression or even improving curve magnitude.

In IIS cases that are progressing or have risk factors for progression, bracing treatment is sometimes considered, but its efficacy in EOS continues to be a source of debate and compliance with brace wear is often challenging in this age group. Currently, casting is typically the first line in treatment. Mehta et al have demonstrated that casting may not only slow progression, but in some cases may also lead to curve resolution, especially when initiated in younger children with smaller curves (mean Cobb angle 32°, mean age 19 months).⁷ This type of casting is also known as EDF casting for the elongation, derotation, and flexion maneuver that is performed. The positive outcomes seen in Mehta’s series have driven a resurgence of enthusiasm for casting. Alternative techniques include placing the cast with the child suspended instead of in traction, casts that do not go over the shoulder, or even those placed without anesthesia are being trialed in an effort to optimize conservative management.⁸^,⁹^,¹⁰ While many cases of IIS may be successfully managed conservatively, some curves continue to progress despite this, prompting consideration of surgical management with growing spine instrumentation (see Figure 2).

Figure 2 A through C, Radiographs show a patient with IIS and complete resolution of the curve with observation alone. D through F Shows a patient with a similar curve magnitude on presentation but characteristics predictive of progression. The patient’s curve progressed and surgery for growing rod placement has been scheduled.

Congenital Scoliosis

Congenital scoliosis consists of a variety of vertebral anomalies that can be broadly categorized as either defects of vertebral formation or defects of segmentation. These two types of defects may occur separately or in combination, which can be particularly problematic. A unilateral failure of segmentation (bar) opposite a contralateral hemivertebrae is known to progress rapidly. Of note, a true hemivertebrae consists of half the vertebral body, a hemilamina and a single pedicle, but there are many variations of this that may be encountered. Additionally these deformities are often associated with rib deformities that may also impact the child’s pulmonary function.

An important aspect of evaluating the child with congenital scoliosis is evaluating for other concomitant anomalies. For patients with significant or progressive congenital scoliosis, an MRI is recommended due to the high rate of associated intraspinal anomalies, which have a prevalence of up to 37% in some series.¹¹ An additional consideration is the evaluation of the genitourinary system, as anomalies will be found in approximately 20% of children with congenital scoliosis.¹² While many MRI protocols will also image the genitourinary system, this is traditionally evaluated with a renal ultrasonography. Similarly, these patients with congenital scoliosis have around a 25% incidence of cardiac anomalies, so if the child has not had a formal cardiac evaluation an echocardiogram is warranted.

Although bracing treatment will not alter the natural history of the anomalous congenital deformity, it may be of benefit to address the longer, flexible compensatory curves that often surround these deformities. Casting was historically thought to be contraindicated in cases of congenital EOS; however, several series have now shown success in slowing progression of congenital curves and delaying instrumentation.¹³^,¹⁴ For young children with congenital scoliosis that progresses despite casting or whose rib deformity and/or pulmonary status prevent them from being a casting candidate, growing spine instrumentation with growing rods or VEPTR implants is typically the next step in management. Of note, the initial VEPTR description advocated for thoracoplasty in addition to placement of rib anchors, but due to concerns about creating chest wall stiffness and rigidity, most surgeons reserve cutting the ribs for cases in which there are multiple rib fusions.

One notable exception to avoiding early spinal fusion is congenital scoliosis where the spine deformity is limited to a small number of vertebrae. For example, in the case of an isolated hemivertebra causing progressive scoliosis, an early fusion (with or without excision of the hemivertebrae) can often correct the scoliosis in a single surgery between the ages of 3 and 6 years, with a fusion of only two to four vertebrae.

Neuromuscular/Syndromic Scoliosis

Neuromuscular and syndromic scoliosis comprises a diverse group of conditions, many of which have their own unique considerations. While treatment with bracing treatment or casting is generally the initial management in these cases, there are some diagnoses where this is either ineffective or contraindicated. For example, in patients with spinal muscular atrophy (SMA), scoliosis will develop in over 90% of patients. In these SMA patients, bracing treatment has been unable to prevent scoliosis development and can lead to respiratory complications.¹⁵ Although a soft TLSO is sometimes used for positional support in these flaccid curves, the treatment to address the SMA scoliosis is typically surgical. In cases of slow progression and stable pulmonary function, this may be delayed until the child is old enough for spinal fusion, though many of these children experience rapid progression and undergo treatment with growing spine instrumentation. A notable consideration in the SMA population is skipping fusion levels or performing a laminectomy in the lumbar spine as the only currently available treatment for this condition requires intrathecal drug delivery which can be more difficult with a solid fusion.

In patients with cerebral palsy, scoliosis commonly develops and is more frequently observed in patients with greater functional involvement, with 30% of GMFCS V cerebral palsy patients having a moderate to severe curve by the age of 10 years.¹⁵ There are limited data on the impact of bracing treatment on these curves in the early-onset scoliosis population, though it has been shown to be ineffective in preventing progression in the adolescent cerebral palsy population.¹⁶ Although there are limited data on casting for patients with cerebral palsy for early-onset scoliosis, these patients have been included in other studies of neuromuscular EOS patients in general and casting is often used in attempt to postpone surgical management though this would not be expected to be curative.¹⁴^,¹⁷ In patients with continued, severe progression, growing rods have been shown to be an effective treatment though the deep infection rate is reportedly as high as 30%.¹⁸ A frequent question in both the EOS and adolescent neuromuscular patients with progressive spinal deformity is whether the benefits of surgical management exceed the risks given the frequently severe medical comorbidities. Though each case must be evaluated individually in this respect, most series favor surgical intervention despite a high complication rate with a preference for early fusion when patient size permits.⁷^,¹⁹^,²⁰

Growing Spine Instrumentation

In many EOS cases, management with observation, bracing treatment or casting is sufficient to either prevent the need for instrumentation or postpone surgical intervention until an age where a definitive fusion can be performed. Nevertheless, when the scoliosis progresses aggressively despite these conservative measures or the child is not a candidate for bracing treatment or casting due to concomitant medical comorbidities,
earlier intervention may be necessary. Fusion of the very young child with a spinal deformity was once standard but has fallen out of favor as this approach resulted in small lung volumes and subsequent restrictive lung disease.³ The last decade has witnessed the development of several “growth-friendly” alternatives. The objectives of these implants are to maximize growth of the spine and facilitate development of the thorax and lungs while controlling curve progression. Nevertheless, use of these modern implants should be delayed for as long as possible as early instrumentation is fraught with both a high complication rate and a decrease in the amount of growth or expansion over time.²¹^,²² These “growth-friendly” implants can be classified into three distinct subtypes including distraction-based, guided growth, and compression-based strategies.²³ Of note, due to the relatively rare nature of these curves, the majority of studies of “growth-friendly” instrumentation are comprised of series of patients with not only IIS but a diverse group of patients with early onset scoliosis.

Of the “growth-friendly” techniques, distraction-based strategies are the most commonly used including traditional growing rods, vertical expandable prosthetic titanium rib (VEPTR) device, and magnetically lengthening growing rods. Traditional growing rods consist of a proximal and distal anchor with either a screw or hook attached to the spine. These anchors are then connected by either a single rod, or preferably dual rods, with expandable segments in the middle. This segment between the anchors is intentionally not fused to allow for growth and expansion and is surgically lengthened at approximately 6 month intervals. In a series of 24 patients by Akbarnia et al. with a mean of 4-year follow-up, there was an improvement of coronal plane scoliosis curve from 82° to 36° and an average of 1.2 cm growth in T1-S1 length per year.²⁴ An additional series found that patients who were lengthened at ≤6 month intervals had significantly higher annual T1-S1 growth rate of 1.8 cm/yr compared with 1.0 cm/yr in patients lengthened less frequently, leading many to believe that distraction may in fact promote growth of the spine.²⁵ An alternative to the traditional growing rod is the vertical expandable prosthetic titanium rib (VEPTR) device developed by Robert Campbell who furthered our understanding of the chest wall deformity and resultant thoracic insufficiency syndrome that many of these children endure. VEPTRs consist of rib anchors and were initially described for the primary purpose of chest expansion. However, as the thorax and spinal development are closely linked, they have also demonstrated the ability to control the coronal curve while promoting spinal growth.²⁶^,²⁷

Another option is a hybrid construct, combining both the traditional concept of growing rods and VEPTR using rib anchors as the proximal attachment for a growing rod construct. This allows the theoretical advantage of avoiding any fusion of the spine at the proximal anchor site. Additionally the flexibility of the ribs as upper anchors may reduce the rigidity of the construct and help protect against rod fractures. While all of these options initially require surgical lengthenings through the growth period, a magnetically lengthening option has now obtained FDA approval. While the overall construct is similar to prior growing rods, this allows the implants to be lengthened in an office setting. The initial studies of magnetically lengthening growing rods (MCGR) appear promising with regard to achieving similar curve correction and increases in spine length with far fewer surgical procedures.²⁸ For example, a case-control study comparing 12 matched MCGR and traditional growing rod patients demonstrated no significant difference in spine length gains, though 57 fewer surgical procedures were performed in the MCGR group.²⁹ While implant complications continue to occur with MCGR, avoiding the need for routine surgical lengthening will likely have both physical and psychosocial benefits for this patient population (Figure 3).

Although distraction-based techniques remain the most popular option for “growth-friendly” instrumentation, there are also guided growth and compression-based alternatives. Guided growth techniques aim to straighten the spine with instrumentation that allows the vertebrae to continue to grow along the path of the implants. Authors have described the Shilla technique in which there is an apical fusion and sliding screws at either end placed with minimal dissection in the hopes of avoiding spontaneous fusion.³⁰ The major theoretical advantage of growth guidance techniques over growing rods is that children avoid multiple surgical lengthenings though there is some evidence that less spinal growth and less correction of scoliosis is seen with Shilla compared with growing rods.³¹

Another alternative approach is compression-based implants which aim to correct the scoliosis by stopping the growth of the convex side of the scoliosis without fusion and allowing growth of the concave side of the curve. This is performed via an anterior approach typically thoracoscopically in which staples, tethers, or other devices are placed across the vertebral epiphyseal plate on the convex side of the scoliosis. Although several case series on compression-based implants have demonstrated improvement in curve magnitude in scoliosis patients, due to the risk of overcorrection, these techniques are generally
reserved for patients with more limited growth potential, such as those aged 9 years or above.³² Prospective studies are underway to study efficacy and complications. Data on thoracoscopic anterior spinal instrumentation have shown minimal effect on pulmonary function, but there are concerns regarding the pulmonary impact of one or more transthoracic surgeries if performed through an open approach. Open anterior surgery should be avoided as serial measures of lung function in older children with scoliosis treated with anterior open spine surgery have shown greater loss of pulmonary function postoperatively than with posterior spinal instrumentation.³³

Figure 3 A through C, Preoperative, postoperative, and most recent radiographs of a patient with early-onset scoliosis associated with spinal muscular atrophy (SMA) who underwent magnetically lengthening growing rods (MCGR) which allows for lengthening in the clinic setting as shown (red arrows showing device distraction).

Adolescent Idiopathic Scoliosis

Adolescent idiopathic scoliosis (AIS) is the most common type of scoliosis in children. Mild curvatures are present in up to 1 in 20 children. Moderate scoliosis is found in up to one in 300 children and one in 3,000 children require surgical management for severe curves over 45° to 50° due to concern of ongoing progression in adulthood. Treatment options include observation, bracing treatment, and surgery. The etiology is unknown, but genetic and structural factors are actively being explored. Up to 30% of patients with AIS have been shown to have lower bone mineral density than population controls, which is associated with increased risk of curve progression and corrects with calcium and vitamin D treatment.³⁴

Nonsurgical Management of Adolescent Idiopathic Scoliosis

Bracing treatment in a corrective TLSO for curves between 20° and 40° is recommended for children with growth remaining either Risser 2 or less or Sanders Stage 5 or less. The greatest risk for curve progression is at peak growth velocity or Sanders Stage 3. The simplified Tanner-Whitehouse (Sanders digital maturity stage classification, Table 1, Figure 4) has been found to be highly predictive of peak growth velocity with good inter-and intraobserver reliability and is preferred over Risser staging.³⁵^,³⁶^,³⁷^,³⁸ At peak growth velocity, all digital physes are capped (Sanders Stage 3) and children are 90% of final adult height. At Sanders Stage 4, children are 96% of their final adult height (Figure 5).

Increased hours of brace wear and correction in brace are predictive of a successful brace outcome.³⁹ Standing radiographs should be obtained in brace to ensure at least 25% to 50% curve correction in brace. The BrAIST study was a prospective randomized controlled study which was stopped early by the data safety monitoring board due to the efficacy of bracing treatment, which found it unethical to withhold full-time bracing treatment from enrolled patients in the control
group. Treatment failure (progression to curve 50° or greater) was 28% with bracing treatment versus 52% without bracing treatment, with a mean of 12 hours of daily brace wear.

Table 1 Key Findings of the Simplified Tanner-Whitehouse III Skeletal Maturity Assessment

Stage	Key Features	Greulich and Pyle Reference Related	Maturity Signs
1. Juvenile slow	Digital epiphyses are not covered.	Female 8 yr + 10 mo Male 12 yr + 6 mo (note fifth middle phalanx)	Tanner stage 1
2. Preadolescent slow	All digital epiphyses are covered.	Female 10 yr Male 13 yr	Tanner stage 2. starting growth spurt
3. Adolescent rapid—early	The preponderance of digits are capped. The second through fifth metacarpal epiphyses are wider than their metaphyses.	Female 11 and 12 yr Male 13 yr + 6 mo and 14 yr	Peak height velocity, Risser stage 0, open pelvic triradiate cartilage
4. Adolescent rapid—late	Any of distal phalangeal physes are clearly beginning to close (see detailed description in the text).	Female 13 yr (digits 2,3, and 4), male 15 yr (digits 4 and 5)	Girls typically in Tanner stage 3, Risser stage 0, open triradiate cartilage
5. Adolescent steady—early	All distal phalangeal physes are closed. Others are open.	Female 13 yr + 6 mo Male 15 yr + 6 mo	Risser stage 0, triradiate cartilage closed, menarche only occasionally starts earlier than this
6. Adolescent steady—late	Middle or proximal phalangeal physes are closing.	Female 14 yr Male 16 yr (late)	Risser sign positive (stage 1 or more)
7. Early mature	Only distal radial physis is open. Metacarpal physeal scars may be present	Female 15 yr Male 17 yr	Risser stage 4
8. Mature	Distal radial physis is completely closed.	Female 17 yr Male 19 yr	Risser stage 5
Reprinted with permission from Sanders JO, Khoury JG, Finegold DN: Predicting scoliosis progression from skeletal maturity: A simplified classification during adolescence. J Bone Joint Surg Am 2008;90[3]:540-553. doi: 10.2106/JBJS.G.00004.

Latest studies show bracing treatment with a TLSO does not adversely affect patient quality of life, although historic studies showed permanent decrease in body image from Milwaukee brace treatment. Counseling using a brace monitor may increase daily hours of brace wear by a mean of 3 hours.⁴⁰ Interest in Rigo Cheneau bracing treatment is high, but currently there is no comprehensive data showing superiority of these braces over a standard TLSO or Boston brace. Minsk et al showed lower rates of surgery in the Rigo Cheneau group at 0% (0 out of 13 patients) versus 32% (32 out of 95 patients) in a retrospective group of patients with a mean of 16 to 17 hours of daily brace wear; however, there may be selection bias in these cohorts.⁴¹ Further interest exists in the role of scoliosis-specific exercises. Limited short-term preliminary data show potentially less curve progression and improved health-related quality of life scores in those who participate in scoliosis-specific exercises.⁴² Similarly, data regarding the role and efficacy of night-time hypercorrection bracing treatment are forthcoming.

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