Early Onset Scoliosis
Scoliosis is defined as a three-dimensional deformity of the spine that includes not only a more noticeable lateral deviation, but also rotation of the vertebrae within the (lateral) curvature. Scoliosis can be further classified by the age of a patient. Early onset scoliosis is defined as scoliosis diagnosed before the age of 10 years old due to any cause (Figure 1). Early onset scoliosis can be categorized by etiology: namely, congenital, syndromic, neuromuscular and idiopathic. The scoliosis might be present without a known cause too; this is termed idiopathic scoliosis. Idiopathic scoliosis is rare in children under the age of 10. (Adolescent idiopathic scoliosis is discussed in its own chapter.)
Structure and Function
Growth of the spine and the chest wall are critical for lung growth and development. Without normal growth, alveolar hypoplasia and disturbance of chest wall function causes a restrictive lung disease and possible respiratory failure.
The “golden time” for lung growth is from birth to the age of 5 years old and coincides with the period of most rapid growth of the thoracic spine and rib cage. Bronchial tree and alveolar complement are maximally developed by 8 years of age, and the thoracic volume at 10 years of age is 50% of the expected adult volume.
Patients with congenital anomalies causing their early onset scoliosis often have rib fusions or other anomalies that can disturb the normal biomechanics of chest wall, leading to decreased forced vital capacity (FVC). The term thoracic insufficiency syndrome (TIS) has been coined to describe the inability of the thorax to support normal respiration and lung growth.
Because the earlier that a spinal deformity appears, the greater the disturbance on thoracic cage, patients with early onset scoliosis have greater lung dysfunction and increased mortality rates compared to the general population, in proportion to the magnitude of the spinal deformity.
Early onset scoliosis can be categorized by etiology, as follows: congenital, syndromic, neuromuscular and idiopathic.
Congenital early onset scoliosis
Congenital scoliosis (Figure 2) is defined as scoliosis caused by at least one bony anomaly of the spine which is present at birth (though the diagnosis may not be made until later in childhood). Congenital anomalies include failure of vertebral formation, such as hemivertebrae or wedged vertebrae, or failure of separation or segmentation, such as block vertebrae or unilateral bars. A unilateral unsegmented bar with a contralateral hemivertebrae is the anomaly known for the worst risk of progression of congenital scoliosis. A positive family history is found in 1% of patients with congenital spinal deformities, but a genetic cause has not been discovered.
The neural axis, vertebral column, and other organ systems develop simultaneously at about five to eight weeks of gestation. Thus, congenital scoliosis may be associated with an intraspinal anomaly such as a tethered cord, diastematomyelia (a longitudinal cleft in the spinal cord), diplomyelia (duplication of the spinal cord), syringomyelia (fluid-filled cavity in the spinal cord), or Arnold-Chiari malformation (herniated cerebellar tonsils at the foramen magnum). Because the vertebral malformations form during embryogenesis at the same time the heart and kidneys are also developing, about 60% of patients will have abnormalities affecting these systems. Accordingly, a renal ultrasound and echocardiogram is often obtained to evaluate for concomitant pathology.
A constellation of symptoms often diagnosed in patients with congenital scoliosis is the VACTERL syndrome, consisting of: vertebral defects, anal atresia, cardiac defects, tracheo-esophageal fistula, renal anomalies, and limb abnormalities. A patient must have at least three of the features to be diagnosed with VACTERL syndrome.
Syndromic early onset scoliosis
Syndromic scoliosis is defined as scoliosis that appears in conjunction with a recognized pediatric syndrome, such as Marfan’s, Ehlers-Danlos, trisomy 21 (Downs syndrome), Prader-Willi, Retts, neurofibromatosis, Noonan, or osteoporosis imperfecta.
When a child is diagnosed with a syndrome known to be associated with scoliosis, it is important that physicians screen for scoliosis. The natural history of scoliosis associated with these syndromes varies, so the curves they cause progress at different rates and require personalized treatment approaches.
Neuromuscular early onset scoliosis
Neuromuscular scoliosis is defined as scoliosis caused by a neurologic disorder of the central nervous system or muscle, such as muscular dystrophy, cerebral palsy, spina bifida, spinal muscular atrophy, or Freidrich’s ataxia.
The likelihood of developing neuromuscular scoliosis usually depends on the extent of nerve and muscle involvement with a specific disorder. Not all children with a neuromuscular disorder will develop scoliosis, but it is especially common in those who are not able to walk.
Neuromuscular scoliosis differs in particular from other types of scoliosis as the deformity is often a long, sweeping curve, typically involving the thoracic spine, the lumbar spine, as well as the pelvis.
Idiopathic early onset scoliosis
Idiopathic scoliosis is defined as scoliosis without known cause; that is, when congenital, syndromic and neuromuscular causes have been excluded. Children with idiopathic early onset scoliosis are considered otherwise healthy.
Idiopathic scoliosis can be of the infantile type (diagnosed at less than 3 years of age). This is very rare. Juvenile Idiopathic scoliosis is that diagnosed between 3 years and 10 years of age. (The most common form of idiopathic scoliosis, the Adolescent type, refers to scoliosis occurring after 10 years of age in the setting of an otherwise healthy child. This, by definition, is not a type of early onset scoliosis.)
Patient Presentation
Evaluation of a patient with concern for early onset scoliosis begins with a comprehensive prenatal and birth history, as well as a detailed review of other medical conditions.
It is important that neurologic, pulmonary, urogenital, cardiovascular, and gastrointestinal systems have been evaluated if there is concern for congenital scoliosis.
If surgery is ultimately planned, evaluation should also include the current nutritional and pulmonary status of the patient.
A physical exam should start with measurements of height and weight. A full neurologic exam tests sensation, motor function and reflexes in the upper and lower extremities. Increased or decreased tone should be noted in patients with neuromuscular conditions. The skin should be examined for cafe-au-lait spots associated with neurofibromatosis, hair tufts or skin dimples near the sacrum associated with congenital scoliosis, and hypermobility associated with connective tissue disorders.
Coronal and sagittal balance is assessed by observing the patient from the front and the side, to see if they are tilted to one side (coronal imbalance), or have increased or decreased lordosis or kyphosis (sagittal imbalance). The examiner should also assess whether the torso is level, by palpating the iliac crests and the top of the shoulders.
The Adams forward bend test (Figure 3) has the patient bend at the waist, reaching toward their toes while the examiner stands behind the patient, looking at the back for asymmetric axial rotation of the trunk. If present, this will appear as a rib prominence on one side of the back. When the patient bends forward with the shoulders level with the hips, a scoliometer –a device similar to a carpenter’s level, with a cutout to rest on the spine and markings to indicate the angular deviation from the horizontal– is laid to rest atop the most severe part of the deformity. A scoliometer reading of seven degrees or more warrants a referral to a pediatric orthopaedist.
Note that performing the Adams forward bend test can be challenging in many children with EOS that are not independently ambulating; others may be unable to stay still for the scoliometer readings. In these cases, the spine exam can be performed while the child is sitting, with the examiner paying particular attention to shoulder or waistline asymmetry
Objective Evidence
The diagnosis of scoliosis is established with a plain radiograph in the posteroanterior plane. A lateral radiograph is also useful for evaluating for sagittal plane abnormalities and where a diagnosis of scoliosis is suspected. These two views should be obtained in most cases.
Radiographs are important to the diagnosis of congenital scoliosis because bony anomalies can be identified that are causing scoliosis to occur. In the absence of congenital anomalies, plain radiographs are useful for assessing the severity of scoliosis and the risk of progression.
The Cobb angle (Figure 4) describes the angle of the spinal curvature for each curve present in the spinal column resulting in a scoliosis. A patient may have cervicothoracic, thoracic, thoracolumbar, or lumbar curve(s) depending on which region of the spine is involved in scoliosis.
To measure the Cobb angle, one must first decide which vertebrae are the end vertebrae of the curve deformity, which means the vertebra whose endplates are most tilted towards each other. Lines are then drawn along the endplates, and the angle between where the two lines intersect is the Cobb angle.
The vertebrae are also evaluated for the presence or absence of rib head overlap with the vertebral body at the apex of the curve (the vertebra that is located at the farthest point laterally from the midline of the body on the convexity of the curve). This assessment is termed the rib phase (Figure 5).
Phase 1 ribs do not overlap the vertebral bodies, while Phase 2 ribs do overlap the vertebral bodies. Patients with Phase 2 ribs are more likely to have progressive scoliosis, and therefore should be treated more aggressively.
An MRI of the entire spine is indicated for all patients with early onset scoliosis to evaluate for intraspinal abnormalities that may not yet be detectable based on clinical exam. About 20-40% of early onset scoliosis patients will have an abnormality, such as a tethered cord, Chiari malformation, or syrinx. A CT, especially with a three-dimensional reconstruction, can be useful to better delineate bony abnormalities and for surgical planning.
Epidemiology
More than 100,000 children in the United States are diagnosed with scoliosis annually. The majority of those children are diagnosed with adolescent idiopathic scoliosis rather than early onset scoliosis. Because early onset scoliosis comprises a group of conditions with diverse etiologies and natural histories, the exact prevalence of early onset scoliosis is unknown. Idiopathic early onset scoliosis is estimated to account for less than one percent of all scoliosis.
Red Flags
There are several “red flags” in the history, physical exam, and radiographs of a patient that should concern the treating provider.
An abnormal neurologic finding or a left thoracic curve can be predictive of an underlying pathologic condition of the spinal cord, although in early onset scoliosis, left thoracic curves are more common and less likely to be pathologic than in AIS.
A painful scoliosis should prompt suspicion for an osteoid osteoma, a benign bone tumor that in the spine is most commonly found in the thoracic and lumbar posterior elements and releases prostaglandin.
A rapidly-progressing scoliosis should raise concern for a tethered cord, also known as “tethered spinal cord syndrome.” A tethered cord syndrome is present when there is a pathological development of excess fibrous connective tissue (fibrosis) in the filum terminale that fixes (or tethers) on the caudal spinal cord to the sacrum, limiting its movement. When a child grows, this abnormal attachment causes stretching and tension on the spinal cord. This can cause scoliosis, motor and sensory changes in the legs, back pain, foot deformities, and urinary dysfunction. Scoliosis can be one of the early signs of a tethered cord, so if there is any concern then an MRI should be ordered.
Treatment Options and Outcomes
Historically, the standard of care for severe, progressive early onset scoliosis was early definitive anterior and posterior spinal instrumented fusion. It was thought that a short but straight spine was superior to a long but curved spine, but now our understanding is that a well-aligned spine with a thoracic cavity large enough to support pulmonary development is the proper goal.
Nutrition is important in early onset scoliosis patients independent of treatment. Patients with severe spine deformity are often underweight, have poor soft tissue coverage over rib or spinal bony prominences/implants, and thus are a setup for complications. A nutrition consult can be helpful in advance of any treatment or at the time of the occurrence of wound complications in order to best optimize the patient pre-operatively or promote healing moving forward.
Non-operative Treatment
The first approach to a patient with early onset scoliosis is to use non-operative methods in an attempt to delay surgery. Some patients will in fact improve with non-operative treatment alone, such that later surgery is not needed. About 80% of children with idiopathic infantile scoliosis, for instance, will have resolution of scoliosis.
Serial casting and bracing have both been used. The concept of serial casting is based on the fact that growth can drive correction of the three-dimensional deformity. Patients with documented progression of scoliosis but low magnitude curvature (less than 60 degrees) or low risk for anticipated progression are candidates for serial casting.
A cast is applied on a special table that applies traction to the patient’s head and legs while anesthetized. The traction distracts the facet joints so that there can be increased movement between vertebrae, then the cast is applied with a mold over the ribs in order to rotate the spine and chest wall opposite the direction of the deformity. Windows are made in the cast anteriorly and posteriorly to allow room for normal expansion of the thoracic and abdominal cavities with respiration and eating. Casts are changed every 2 to 4 months based on age and growth and can be eventually replaced by a brace if the curve reduces to 10 to 20 degrees.
Outcomes of casting are best when casting is initiated at a younger age and when performed for less severe, idiopathic curves. Concerns and potential complications of casting include skin breakdown, negative effects on quality of life, repetitive anesthesia events for cast changes, and superior mesenteric artery or brachial plexus compression from the cast. Casts may not be tolerated in patients with poor pulmonary function or sensory disorders. Bracing can be similarly used to control non-congenital early onset scoliosis deformities with a goal of delaying surgery, or after serial casting is successfully completed. When a brace is used in a rapidly growing child younger than 5 years old, the patient may develop rib deformity or loss of the normal sagittal profile from pressure from the brace.
Operative Treatment
Currently, the concept of allowing continued growth of the spine and chest instead of performing a spinal fusion, while still managing spinal deformity, is of great interest in early onset scoliosis patients. Growth-sparing techniques have been classified into distraction-based techniques (meaning distracting posteriorly on the spine to lengthen the spine and enlarge the thoracic cavity), convex compression-based growth inhibition (meaning inhibiting vertebral body growth on the convexity of the curve to correct a curve), and guided growth (meaning directing growth to correct a curve over time). Spinal fusion is typically delayed until at least age 10, at which point the thoracic cavity is sufficiently developed to support the child through adult life.
Distraction-based techniques involve attaching rods to the spine or ribs proximally and to the spine or pelvis distally, while avoiding the spine in between the anchored segments. The rods are then distracted or lengthened by various mechanisms in order to produce growth of the spine and in turn the thoracic cavity. The options for distraction-based instrumentation include the “vertical expandable prosthetic titanium rib,” also known as the VEPTR, (Figure 6); a “traditional growing rod” (TGR) (Figure 7); and the magnetically-controlled growing rod (MCGR) (Figure 8).
Complications of these techniques include implant prominence which can eventually result in skin breakdown, surgical site infection, implant breakage, implant migration, and failure to lengthen, all of which result in return trips to the operating room and additional anesthetic events. Repeat lengthening surgery is problematic as with each additional surgical procedure the likelihood of a complication rises in an already risky/sick patient population. (This makes the MCGR so appealing: it helps avoid trips to the operating room.)
Convex compression-based growth inhibits deformity progression by applying a compressive force on the convex side of the scoliosis deformity.
Guided growth (Shilla system) relies on fixation at the apex of a scoliosis curve with gliding fixation proximally and distally so that the spine can continue to grow above and below while gradually correcting the scoliosis. Osteotomies are performed at the apex to correct as much deformity as possible and pedicle screws are placed at the apex over three or four vertebral segments.
Resection and short fusion can be the treatment methodology employed when attempting to manage specific types of congenital scoliosis. A hemivertebra causing a progressive scoliosis in a very young child may be completely resected with a short (2-level) spinal fusion using pedicle screws/hooks to correct deformity and minimize the need for repeat surgical procedures. However, there are risks of neurological injury with hemivertebra resection, thus the decision to resect versus growth-sparing techniques may be a complicated one.
Key Terms
Early onset scoliosis, congenital scoliosis, neuromuscular scoliosis, syndromic scoliosis, idiopathic scoliosis, casting, growth-sparing spine surgery
Skills
Name the etiologies of early onset scoliosis. Understand the importance of spinal growth on thoracic cavity growth and pulmonary development. Describe the Adams forward bend test and how to use a scoliometer. Describe VACTERL syndrome. Understand the work-up, associated conditions or syndromes, and red flags important for a patient with concern for early onset scoliosis. Understand the measurements used in radiographic assessment of early onset scoliosis and measure the Cobb angle in plain x-rays.