Infantile Scoliosis 

Updated: Nov 01, 2019
Author: Palaniappan Lakshmanan, MBBS, MS, AFRCS, FRCS(Tr&Orth); Chief Editor: Jeffrey D Thomson, MD 

Overview

Practice Essentials

The term scoliosis is derived from the Greek word skolios ("twisted") and refers to a sideward (right or left) curve in the spine. Scoliosis is not a simple curve to one side but, in fact, is a more complex three-dimensional deformity that often develops in childhood.

The term infantile scoliosis is used specifically to describe scoliosis that occurs in children younger than 3 years.[1] Other terms for scoliosis also depend on the age of onset, such as juvenile scoliosis (4-9 years) and adolescent scoliosis (10-18 years). These terms, however, are now being replaced by the broader terms early-onset scoliosis and late-onset scoliosis, depending on whether the scoliosis occurs before or after the age of 10 years.[2]

In 80% of cases of scoliosis, there is no obvious cause; this is termed idiopathic scoliosis. In the remaining 20% of cases, a definite cause can be found. These cases are divided into the following two types:

  • Nonstructural (functional) scoliosis
  • Structural scoliosis, which could be part of a well-recognized syndrome (syndromic scoliosis) or could involve congenital spinal column abnormalities (congenital scoliosis), neurologic disorders, or genetic conditions

Evidence in the literature from two major centers in the United Kingdom suggests that the association of neural axis anomalies with early-onset idiopathic scoliosis is only 11.1%.

The syndromes that can produce structural scoliosis are VATER syndrome (vertebral anomalies, anorectal anomalies, tracheoesophageal fistula, and renal anomalies), VACTERL syndrome (vertebral anomalies, anorectal anomalies, tracheoesophageal fistula, renal and vascular anomalies, and cardiac and limb defects), Jarcho-Levin syndrome, Klippel-Feil syndrome, Alagille syndrome, Wildervank syndrome, Goldenhar syndrome, Marfan syndrome, and MURCS association (müllerian, renal, cervicothoracic, and somite abnormalities).

The congenital anomalies of the vertebral spinal column include defects of segmentation (block vertebra, unilateral bar) and defects of formation (hemivertebra—fully segmented, semisegmented, incarcerated and nonsegmented, wedge vertebra).

The neurologic deficits in structural scoliosis may be secondary to the spinal deformity or may be associated with vertebral anomalies (spinal dysraphism—diastematomyelia, myelocele, myelomeningocele, meningocele).

A higher incidence of idiopathic scoliosis has been reported in families of children with congenital scoliosis. Spondylocostal dysostosis (Jarcho-Levin syndrome) has a genetic etiology.[3, 4, 5, 6]  Research is ongoing to identify any scoliosis-related genes.[3, 4]

Infantile scoliosis usually is detected during the first year of life either by the parents or by the pediatrician during routine examination of the infant. Usually, a single long thoracic curve to the left is present; less often, a thoracic and lumbar double curve is noted. 

There are three management options for infantile scoliosis: observation, orthosis, and operation (see Treatment). The decision when to use each of these is based on the rib-vertebral angle difference (RVAD). The RVAD is a useful guide in distinguishing between resolving and progressive idiopathic infantile scoliosis.

Anatomy

The spine is made up of 33 individual vertebrae that form a column. The spine is divided into the following five regions, starting from the top:

  • Cervical spine (C1-C7)
  • Thoracic spine (T1-T12)
  • Lumbar spine (L1-L5)
  • Sacrum (S1-S5)
  • Coccyx (Co1-Co4)

In adults, the sacrum and the coccyx are fused.

The spine provides a protective function for the spinal cord, bears and distributes the weight of the body, provides an area for attachment of ligaments and muscles, and is the site for production of red blood cells. Together, all the vertebrae form a flexible structure providing mobility for the body to bend forward or sideward.

Each vertebra has a cushionlike fibrous structure called a disk, which acts like a shock absorber during movements of the spine. The disk is made up of a soft, jellylike central nucleus pulposus surrounded by a ring of fibrous tissue called an anulus, which is actually a strong ligament between two adjacent vertebrae.

Developmentally, the spine of the fetus is C-shaped, with concavity in the front (kyphotic) of the thoracic region; this is called the primary curve. Two secondary curves develop after birth, with concavity occurring anteriorly (lordosis); one of the secondary curves develops in the cervical region as the infant starts to hold up the neck, and the second curve develops in the lumbar region when the child starts to walk. Normally, there are no sideward (scoliosis) curves, so that the spine looks straight when viewed from behind or from the front.

Pathophysiology

Most of the curves in the spine develop during the first year of life, and strong correlation has been found between the nursing posture of the infant and development of the curve. It is less common in the United States than in Europe, where babies are nursed in the supine position. Infants have a natural tendency to turn toward the right side, and because of plasticity of the infant's axial skeleton, this can lead to development of plagiocephaly, bat ear on the right side, and curvature of the spine toward the left side.[7]

Etiology

Although the exact cause of idiopathic infantile scoliosis is not known, hypotheses have been proposed on the basis of epidemiologic evidence[3, 4, 5, 7, 8] :

  • One theory holds that the mechanical factors during intrauterine life are responsible for the higher incidence of plagiocephaly, developmental dysplasia of the hip, and scoliosis on the same side of the body
  • A second hypothesis suggests multifactorial causes, including predisposing genetic factors that are either facilitated or inhibited by external factors such as defective motor development or collagen disorders, joint laxity, and nursing posture of the infant
  • Other associations include older mothers from poorer families, breech presentation, and premature and male low-birth-weight babies

 

Epidemiology

Infantile scoliosis is a rare condition, accounting for fewer than 1% of cases of idiopathic scoliosis in North America; in Europe, the rate is 4%.

Males account for 60% of the cases of early-onset scoliosis; 90% of the cases of early-onset scoliosis resolve spontaneously, but the other 10% progress to a severe and disabling condition. Females constitute 90% of late-onset cases and need close monitoring to allow intervention at appropriate times.

Prognosis

More favorable outcomes have been associated with male sex, a left-side curve, a low initial curve measurement, an RVAD of less than 20° in the initial radiograph (see Workup), and the onset of scoliosis in the first year of life.

A study by Gomez et al evaluated 68 patients in the Children's Spine Study Group and Growing Spine Study Group registries who underwent cast treatment for idiopathic scoliosis and were followed for a minimum of 1 year.[9] The prognosis was best for those patients who underwent casting at an earlier age, had smaller major curves, and showed a greater percent major curve correction in initial casting.

 

Presentation

History and Physical Examination

Infantile scoliosis usually is detected during the first year of life either by the parents or by the pediatrician during routine examination of the infant. Usually, a single long thoracic curve to the left is present; less often, a thoracic and lumbar double curve is noted. A child who is diagnosed with scoliosis requires a thorough clinical and radiologic examination to exclude any congenital, muscular, or neurologic causes.

Complications

Other conditions may occur in conjunction with infantile scoliosis. In a review that included 81 patients who were treated with casting for idiopathic early-onset scoliosis (mean age at first cast, 19.3 ± 7.5 months; mean Cobb angle, 53.6º ± 18.8º), Talmage et al reported nine patients (11.1%) who met radiographic criteria for hip dysplasia, 36 (44.4%) who met the criteria of having at least one hip "at risk" for hip dysplasia. 10 (12.3%) who were diagnosed with torticollis, 13 (16.0%) who were diagnosed with plagiocephaly, and three patients (3.7%) who were diagnosed with metatarsus adductus or clubfoot. In all, 30.9% of patients (25/81) had at least one of these comorbid conditions.[10]

 

Workup

Radiography

Radiographs of the spine in infants are taken with the child held up by the arms. Because the patients are very young, radiographs usually are obtained either with a parent holding the child or with the use of a pediatric immobilizer and positioner (eg, Pigg-O-Stat). The severity of the scoliosis is established by calculating the rib-vertebral angle difference (RVAD) in the radiographs (see the image below).[11]

RVAD (rib-vertebral angle difference) measurement RVAD (rib-vertebral angle difference) measurement at apical vertebra: RVAD = b - a (concave - convex side).

The rib-vertebral angle is measured by (1) drawing a line perpendicular to the middle of the upper or lower border of the apical vertebrae of the curve and then (2) measuring the angle this line makes with medial extension of another line drawn from the midpoint of the head to the midpoint of the neck of the rib, just medial to the beginning of the shaft of the rib. The difference between the right side and the left side (ie, between the concave side and the convex side) is the RVAD.

The apical vertebrae are the vertebrae at the curve of the apex. If there are the same number of vertebrae between the superior and the inferior end vertebrae, there will be two apical vertebrae.

Radiographs and RVAD calculations should be repeated every 2-3 months to determine whether the curve is progressing or regressing.

Anteroposterior (AP) radiographs may also be used to evaluate the severity of the curve; however, they may not be accurate, because they assess a three-dimensional (3D) deformity in a two-dimensional (2D) projection. Still, they provide a reasonable estimation of severity and hence are used commonly in the evaluation of scoliosis.

The angle between the superior endplate of the superior end vertebra and the inferior endplate of the inferior end vertebra is assessed. Because lines drawn along these endplates normally pass beyond the edge of the radiograph, a second set of lines is drawn perpendicular to these lines, and the angle subtended between them is measured; this is the Cobb angle (see the image below).

Preoperative scoliogram showing Cobb angle. Preoperative scoliogram showing Cobb angle.

The end vertebrae are the most superior and inferior vertebrae in the curve; they are differentiated by the opening of the intervertebral disk space caused by crowding on the concave surface. These vertebrae are the least displaced and rotated, and they have maximally tilted endplates.[12, 13]

A study by Redding et al reviewed the frequency of asymmetric lung perfusion and ventilation in children with congenital or infantile thoracic scoliosis before surgical treatment and the relation between the Cobb angle and asymmetry of lung function.[14] In this study, asymmetric ventilation and perfusion between the right and left lungs occurred in more than half of the children with severe congenital and infantile thoracic scoliosis, but the severity of this asymmetry did not relate to Cobb angle measurements. Asymmetry in lung function was influenced by deformity of the chest wall in multiple dimensions and could not be ascertained by chest radiography alone.

Computed Tomography

Computed tomography (CT) can be used to get a detailed picture of the scoliosis curve. Because spinal fusion is a major surgical treatment modality, patients must be assessed with respect to their ability to withstand a major surgical procedure, and tests must be done for hemoglobin level and respiratory function.[15]

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is necessary in moderate-to-severe infantile scoliosis because the reported frequency of neural axis abnormalities associated with infantile scoliosis has been high (21-50% in some sources). The common abnormalities are Arnold-Chiari type I malformation and syringomyelia. Hence, whole-spine MRI is indicated before surgery. The current recommendation is for patients with infantile scoliosis with a Cobb angle greater than 20º.

In a retrospective case series assessing MRI findings in 54 patients with presumed infantile idiopathic scoliosis,[16] a neural axis abnormality was revealed in seven patients (13%), of whom five (71.4%) required neurosurgical intervention. Tethered cord requiring surgical release was identified in three patients, Chiari malformation requiring surgical decompression in two, and a small nonoperative syrinx in two. The authors concluded that close observation may be a reasonable alternative to an immediate screening MRI in patients presenting with presumed infantile idiopathic scoliosis and a curve greater than 20º.

A study by Zhang et al used MRI to examine 504 infantile and juvenile patients diagnosed with "presumed idiopathic" scoliosis for neural axis abnormalities.[17]  Such abnormalities were found in 94 of the 504 patients (18.7%). The authors concluded that routine MRI evaluation appeared to be warranted for patients with "presumed idiopathic" scoliosis if they were younger than 10 years, were male, or had a left thoracic or right lumbar curve. 

 

Treatment

Approach Considerations

There are three management options for infantile scoliosis[18] :

  • Observation
  • Orthosis
  • Operation

The decision when to use each of these is based on the rib-vertebral angle difference (RVAD; see Workup), established by Mehta in 1972 (see the image below).[19]  The RVAD is a useful guide in distinguishing between resolving and progressive idiopathic infantile scoliosis.

RVAD (rib-vertebral angle difference) measurement RVAD (rib-vertebral angle difference) measurement at apical vertebra: RVAD = b - a (concave - convex side).

For scoliosis curves with an RVAD of less than 20°, observation every 4-6 months is sufficient. If the RVAD is more than 20° or if it is not flexible clinically (ie, curve cannot be corrected even slightly with different postures, especially lateral bending), then it is considered to be progressive until proven otherwise.

Normally, there are interobserver and intraobserver variations with these radiographic parameters. Corona et al found that even though variations are present in the radiographic parameters of RVAD, Cobb angle, and space available for lung (SAL), these radiographic parameters are useful tools for planning management options.[11] According to the authors, even though these parameters are not devoid of variability, they are not excessively skewed, and the RVAD and the Cobb angle are highly useful for accurately and reliably suggesting the best course of treatment.

Management with orthosis is necessary when the curve is considered to be progressive or if a compensatory curve has developed.[20]  Various types of orthosis are available for children younger than 3 years. The most commonly used orthoses are the following:

  • Hinged Risser jacket
  • Plaster spinal jacket (Cotrel EDF [elongation, derotation, flexion] type) applied under anesthesia
  • Milwaukee brace
  • Boston brace

The brace should be used for 23.5 hours a day and should be removed only for exercises and swimming. It should be used until skeletal maturity is attained, because curves usually do not progress after skeletal maturity; however, curves may progress despite the use of a brace.[21, 22, 23]

Spinal deformity in scoliosis progresses during periods of peak growth velocity. The first spinal growth peak occurs at 2 years of age, and the second peak occurs during the prepubescent period.

Operatitive treatment is usually an option only for children in older age groups (ie, around age 10 years), and segmental posterior wiring to two L-rods without fusion is preferable until combined posterior and anterior fusion can be done. These procedures, however, have been associated with complications in 50% of patients.

Because of advances in instrumentation, pedicle screw instrumentation can be performed for children with further growth potential.[24]  In these patients, a growing rod is used, which is associated with fewer complications than surgical fixation using L-rods. The disadvantage associated with the growing rod is that every 6 months the posterior aspect must be opened to lengthen the rod, which increases the risk of infection; however, if the curve is severe or increases despite the use of orthosis, a short anterior and posterior fusion is recommended to prevent crankshaft phenomenon.

Surgical Therapy

Surgical options

The decision whether to operate on a patient with scoliosis depends on many factors, such as the following:

  • Time of onset of the curve (early-onset curves most often warrant surgery)
  • Degree and site of the curve (a thoracic curve greater than 40° or a lumbar curve greater than 60° in a child aged 10-12 years often requires surgery)
  • Response to conservative treatment with a brace
  • Rate of progression of the curve
  • Acceptability of the cosmetic appearance of the spine to parents and patient

Growing rods without fusion is preferable until combined posterior and anterior fusion can be done. Growing-rod systems (eg, pediatric Isola instrumentation) may be utilized to prevent curve progression; extensions are needed every 6 months to keep pace with the child's growth until the child has adequate trunk length, which is usually between the ages of 11 and 15 years.

Once skeletal maturity is reached, the child needs a definitive fusion[25] ; this involves removal of implants and reinstrumentation. If there is evidence of congenital problems or thoracic insufficiency, another type of growing-rod system (eg, the vertical expandable prosthetic titanium rib [VEPTR]) may first be used.[26, 27, 28, 29, 30]

There is, however, an alternative in very young children in whom the curve progresses: application of a localizer cast.[31, 32] A localizer cast can hold the curve and prevent it from progressing further. However, application of localizer casts is a dying art, and it requires proper care and frequent change of the plaster.

The localizer cast is applied to the child's trunk under general anesthesia, with traction to the head and neck via a sling across the mandible and the occiput and countertraction to the pelvis through another sling. The plaster jacket is applied around the trunk, with care taken to ensure that there is enough room for hip movements by stopping just below the level of the iliac wings. Superiorly, the plaster goes around the axillae, leaving the arms and the shoulders free.

If needed, in higher thoracic curves, a neck support can be included by extending the plaster. However, such support is seldom required, and consideration for surgery should be given in such cases.

A window is cut in the front for abdominal expansion. After the first cast, a radiograph is performed to confirm better correction of scoliosis. If satisfactory control is not obtained, casting can be tried once more with proper moulding of the cast only if the treating surgeon is confident that the curve is flexible and that the original cast was not applied properly. If the child feels uncomfortable, especially with regard to breathing, then the cast should be removed immediately.

The localizer cast must be changed every 3 months as the child grows in height and also as the plaster wears off and the cast loosens. It is not tolerated well by older children and hence is usually best suited to children younger than 5 years. Localizer casts can produce pressure sores, especially in children with underlying neurologic problems. Foreign objects that find their way into the cast can also cause pressure sores in normal children as well as in neurologically impaired children.

A 2012 study found that serial casting delayed surgery by an average of 39 months in moderate-to-severe early-onset scoliosis.[33]

A retrospective study reviewed 31 consecutive patients (average age, 25 months) with a primary diagnosis of idiopathic infantile scoliosis who were treated with bracing, serial body casting, or VEPTR.[34] Of the 17 patients treated with a brace, nine had curve progression and went on to receive other treatments; the remaining eight showed an overall improvement of 51.2%.

The 10 patients who received body casts had a mean preoperative Cobb angle of 50.4º and an average correction of 59.0%.[34] The 10 patients who were treated with VEPTR had a mean preoperative Cobb angle of 90º and an average correction of 33.8%. The study results suggested that body casting is useful in cases of smaller, flexible spinal curves and that VEPTR is a viable alternative for larger curves.

A study by Iorio et al, which included 21 patients with an average Cobb angle of 48º (range, 24-72º) who underwent initial casting at an average age of 2.1 years (range, 0.7 to 5.4 years, found that potential determinants of the success of serial casting included (1) age of less than 1.8 years at the initiation of casting and (2) derotation of the spine to correct RVAD less than 20º.[35]

Preparation for surgery

The general condition of the child should be improved by providing appropriate nutrition and making sure the child is capable of undergoing general anesthesia. Any infections should be treated appropriately.

Flu prophylaxis is indicated for any child with lung problems. Pneumonia prophylaxis is required for any child on a ventilator.

Vertical expandable prosthetic titanium rib

VEPTR is is employed in the management of severe scoliosis in skeletally immature patients. (See the images below.)

Preoperative and postoperative radiographs show in Preoperative and postoperative radiographs show increase in space available for lung (SAL) after correction of scoliosis by VEPTR (vertical expandable prosthetic titanium rib).
Preoperative and postoperative radiographs show in Preoperative and postoperative radiographs show increase in space available for lung (SAL) after correction of scoliosis by VEPTR (vertical expandable prosthetic titanium rib).

VEPTR usually is indicated in patients with thoracic insufficiency syndrome (TIS).[36] Apart from having a spinal deformity, patients may have a deformity of the thoracic cage, such as fused ribs or a hypoplastic thorax. VEPTR helps rebuild the chest wall and correct the spinal deformity, thereby allowing the lungs to expand to achieve normal functioning. Several types of VEPTR devices are available, including the following:

  • Cradle-to-cradle — Used in cases of fixed or missing ribs, severe scoliosis, and hypoplastic thorax
  • Cradle-to-lumbar lamina hook — Used when scoliosis involves the lumbar region or when lower ribs are absent
  • Cradle-to-S-hook — Attaches upper ribs to the pelvis and is useful in cases in which lower ribs are absent and lumbar bones are weak

The patient is placed in the lateral decubitus position. Two incisions are made: (1) a large J-shaped incision medial to the border of the scapula and curving anteriorly and (2) a small incision made distally so as to apply the distal end of the prosthesis to the spine. The prosthesis is applied over the rib cage and beneath the skin and muscle. After the proximal and distal ends are attached, the device is distracted with the aid of expansion pliers.

Intraoperative spinal cord monitoring (somatosensory evoked potentials [SEPs]) has been found to be useful in these cases. If SEPs change intraoperatively, then decreasing the VEPTR expansion may resolve the issue. Spinal cord monitoring can decrease the incidence of neurologic complications following excessive surgical correction.

Pediatric Isola spine system

The Isola system (see the image below) consists of screws with washers that are applied from posterior to anterior, horizontal to the frontal plane of the vertebral body, and parallel to the apex of the curvature. Screws may be applied through the staples.

Postoperative scoliogram after correction with ped Postoperative scoliogram after correction with pediatric Isola system.

Closed-top end screws are placed first. A rod is then contoured along the curvature and is cut to size, so that it extends about 1 cm beyond the end screws. The rod is passed between the two end screws, and open-end screws with staples are then placed in the remaining intervening vertebrae, with the contoured rod serving as a guide for positioning the screws. Caps are placed on the intermediate screws, and the rod is rotated approximately 180° to obtain both a coronal correction and a sagittal correction.[37]

Further correction can be accomplished by opening the vertebral spaces with a Cobb elevator after tightening one of the intermediate screws. At this stage, further correction can also be accomplished by applying distraction between the screw connector bodies. The disk space that is created can now be filled completely with bone graft material. Vertebral screws are compressed centrally, starting from the top of the screw to the bottom, and then to the top of the next screw. The final compression is applied across the apical vertebrae.

Rods are inserted to prevent progression of the curve, and the rods are extended every 6 months to keep pace with the child's growth. Hooks are used as anchors on the upper part of the curve, and pedicle screws are used in the lower part of the curve. At the apex of the curve, the muscle is not dissected, so as to maintain the blood supply to the bone at the apex.

Postoperative Care

The surgical wounds must be protected with padding to prevent injury. The prosthesis must be expanded every 4-6 months as the child grows. Expansion requires that a small incision be made at the site of distraction. When the child stops growing, the device can be removed, and other definitive procedures (eg, rib spreading) may be necessary.

Complications

The risks associated with surgery under anesthesia include the following:

  • Bleeding
  • Pneumonia
  • Wound complications (eg, poor healing, infection)
  • Device-related problems, such as allergic reaction to metal, or bending, breaking, or loosening of the device
  • Neurologic deficit due to stretching of the spinal cord from expansion

Crankshaft phenomenon is a complication following isolated posterior fusion surgeries, in which the unfused anterior vertebral bodies continue to grow and cause lordosis and scoliosis. Crankshaft phenomenon is seen when the spine is skeletally immature, and typically occurs during the two peak growth velocity periods (ie, between birth and the age of 5 years and between the ages of 10 and 15 years).[38]

Paralysis is the most feared complication of surgery for scoliosis. A survey conducted by the Scoliosis Research Society determined that the incidence of acute neurologic complications resulting from the treatment of scoliosis was 0.72%.[39] In infantile scoliosis, because neural axis involvement is significant, the risk of neurologic injury is greater if not recognized preoperatively.

Infection is a risk with all surgical procedures; antibiotic prophylaxis is essential.

Pseudoarthrosis is a failure of the spine to fuse and is more common in adults than in adolescents.

Decompensation occurs because of overcorrection of the spinal curve, in which the curvature of the spine loses its flexibility, causing the patient to lean to one side.

Flat-back syndrome is seen less often now because of technical improvements since the Harrington rod. In this condition, patients have decreased lumbar lordosis and need to hyperextend their hips to stand or need to adopt a flexed-hip-and-knee gait, leading to increased back fatigue.

There is a risk of low-back pain, especially after lower distal level fusion. This may result from unfused levels of the spine or degeneration of the fused spine.

Rod fractures may occur in 15% of cases.[40] The risk of such fractures is not associated with the preoperative magnitude of scoliosis or kyphosis. The risk factors for rod fractures incldue the following:

  • Prior fracture
  • Single rods
  • Stainless steel rods
  • Small-diameter rods
  • Proximity to tandem connectors
  • Short tandem connectors
  • Preoperative ambulation

Repeat fractures are common, especially with single rods. Rod replacement, with larger-diameter rods if appropriate, may be preferable to attempting to connect the broken rods; fractures signal fatigue of the rod.

The complications associated with casting include an increase in peak inspiratory pressure, which can result in increased respiratory complications.[41] Subclavian thrombosis after casting has also been reported in the literature.[42]