Casting for Early-Onset Scoliosis
Casting for Early-Onset Scoliosis
DEFINITION
Early-onset scoliosis is defined as scoliosis occurring by age 5 years. The term was developed because it is more likely associated with long-term pulmonary compromise than in children with later onset scoliosis.2, 16
Infantile scoliosis is another term referring to scoliosis detected by age 3 years. It usually refers to idiopathic scoliosis unlike “early-onset scoliosis” which can include congenital and neuromuscular curves. Occasionally, the term infantile scoliosis will include syndromic children because of the difficulty in identifying many syndromes in young children. Practically, infantile and early-onset scoliosis are often used synonymously.
ANATOMY
Infantile scoliosis is a deformity of the discs, vertebral bodies, and the chest wall. The ribs articulate with the vertebra at both the transverse processes (costotransverse joints) and the vertebral bodies (costovertebral joints).
The spine is usually rotated about the longitudinal axis with the lateral convex side more posterior than the concave side (FIG 1).
PATHOGENESIS
The pathogenesis of idiopathic or most syndromic early-onset scoliosis is unknown. Early-onset scoliosis may have an underlying neurologic or muscular abnormality.
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FIG 1 • A. An AP radiograph of a 12-month-old child with a typical left lower thoracic infantile scoliosis. B. A computed tomography (CT) scan at the apex of an infantile scoliosis showing the rotation with the anterior spine rotated toward the concavity and the posterior spine toward the convexity.
NATURAL HISTORY
Infantile curves may be either resolving or progressive with resolving curves being far more common.
Scoliosis presenting during the first year of life has a greater likelihood of resolving spontaneously, whereas curves developing after 1 year of age have a worse prognosis.12, 13
Both the rib-vertebral angle difference (RVAD) and rib phase are important for predicting which curves will progress15 ( FIG 2).
The RVAD is the difference of the angles made between each rib and the corresponding vertebral body. This is measured at the vertebral level with the greatest angular difference between the concave and convex rib.
Rib phase is classified as phase 1 or 2, depending on whether or not spinal rotation causes the rib head to overlap the vertebral body (phase 1, no overlap; phase 2, overlap).
Eighty-three percent of resolving curves have a RVAD of less than 20 degrees and 83% of progressing curves have a RVAD of greater than 20 degrees.
In progressive curves, the RVAD increases and the phase gradually transitions from 1 to 2. Phase 2 ribs are the hallmark of progressive curves, as all phase 2 curves progress.
Double curves present a special problem as most of them progress.
The RVAD in double curves may be quite low, but an oblique 11th or 12th convex rib with lumbar rotation is a poor prognostic sign.
Generally, the RVAD and phase are reliable, but the measurement error may make discernment difficult in
marginal cases,4 in which case, close observation, typically with repeat radiographs in 3 months, is the best course.
Left untreated, the prognosis for curves that do progress is invariably poor: By age 5 years, 57% of untreated children
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will have a curve greater than 70 degrees.15 These large thoracic curves can cause restrictive lung disease or thoracic insufficiency syndrome (TIS) characterized by decreased thoracic growth and lung volume, inhibiting
alveolar development and lung function, which may cause respiratory failure and death at an early age.7 The thoracic deformity can also lead to pulmonary hypertension and cor pulmonale, with respiratory failure and death occurring at a later age.3, 10, 15, 18 Curves of greater than 70 degrees are sufficient to cause cor
pulmonale and have a higher mortality rate than smaller curves.10, 16
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FIG 2 • The RVAD from the same child shown in FIG 1A.
Patients with progressive curves progress by about 5 degrees per year reaching 70 degrees or more by age 10 years.9, 17 Thoracic curves greater than 70 degrees in adolescence are associated with significantly lower forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) values compared to
patients with smaller deformities.
EOS patients have greater pulmonary function test (PFT) impairment than adolescent idiopathic scoliosis patients.11
PATIENT HISTORY AND PHYSICAL FINDINGS
Typically, parents have noticed the deformity before their physicians. It is important to ask about a family history of nerve or muscle disorders. Unlike adolescent scoliosis, early-onset scoliosis is not often familial except in neuromuscular disorders. Because young children cannot cooperate with a manual motor examination or an Adams forward bend test, one must rely on close observation to identify the curve and any evidence of neurologic issues or myopathies.
The neurologic examination should include an assessment of gait, upper and lower extremity motor strength where feasible, tone, deep tendon reflexes including abdominal reflexes, clonus, Hoffman, and Babinski signs. Foot deformities, particularly any equinus, cavus, varus, or foot size difference may be the only neurologic signs seen.
Common syndromes associated with early-onset scoliosis include Marfan syndrome, characterized by arachnodactyly (FIG 3) and often having more severe aortic involvement in young children, and Ehlers-Danlos syndrome, characterized by marked ligamentous laxity.
IMAGING AND OTHER DIAGNOSTIC STUDIES
The diagnosis of infantile scoliosis is made on plain anteroposterior (AP) or posteroanterior (PA) and lateral radiographs of the spine. In infants and young children who cannot stand, the radiographs are obtained supine. Once children can stand reliably, they are obtained in a standing position.
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FIG 3 • Arachnodactyly in a 2-year-old child with infantile scoliosis and Marfan syndrome.
Congenital vertebral anomalies such as unpaired pedicles, rib anomalies, and spina bifida are identified on plain radiographs. Because the spine is not fully ossified, the posterior elements may not be fully visualized on the AP view at a young age.
Disorders such as syringomyelia and Arnold-Chiari are sufficiently common that they should be sought with a spinal magnetic resonance imaging (MRI).6, 8
DIFFERENTIAL DIAGNOSIS
Idiopathic scoliosis
Syndromic scoliosis particularly Marfan syndrome, Prader-Willi, and Ehlers-Danlos Congenital scoliosis
Spinal cord anomalies, particularly tethered cord, syringomyelia, and Arnold-Chiari Myopathies and neuropathies such as congenital myopathies and spinal muscular atrophy Cerebral palsy
NONOPERATIVE MANAGEMENT
Bracing is the most common nonoperative treatment of early-onset scoliosis with variable success.1 Bracing is an important adjunctive treatment in cast treatment for early-onset scoliosis and plays an important role in delaying the need for surgery. Braces are difficult to fit in young patients. Young children have more pliable ribs than adolescents, and braces using a three-point bend on the apical rib can create a chest wall deformation by pushing the ribs toward the spine. Bracing may be difficult to properly apply each time to a young child's cylindrical shape. This is compounded by the need to make the brace sufficiently flexible for donning and doffing.
SURGICAL MANAGEMENT
Casting works best in younger patients with idiopathic smaller curves, but it can still help in older patients, those with larger curves, and syndromic curves. Be wary of neuromuscular and congenital curves.
Because of the problem with diminishing returns in growing instrumentation, if casting does not cure the curve, it will, ideally, delay growing rod surgery until at least age 6 or 7 years.
Begin casting when the child is diagnosed with progressive infantile scoliosis, is safe for anesthesia, and the goals are either cure or delay surgery.
The family must agree to minimum 1 year of casting and understand that even if the curve is not cured, delay for surgery is important.
Preoperative Planning
Because the derotation must be applied to each curve at its apex, it is important to review the patient's radiographs, determine the apices of each curve, and have a plan to properly rotate the spine stabilized against the pelvis and either the right or left pectoral region.
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FIG 4 • A. The child is intubated and prepared on the Mehta casting table with head halter-pelvic traction. B. Covering over the face and mouth, Boston brace shirt, abdominal pad, head halter, and pelvic straps are applied before positioning on the casting frame. (A: From Sanders JO, D'Astous J, Fitzgerald M, et al.
Derotational casting for progressive infantile scoliosis. J Pediatr Orthop 2009;29:581-587.)
Positioning
A proper table that allows secure positioning of the patient with head and pelvic traction, as well as full access to the torso, shoulder girdle, and pelvis, is required.
Although it is possible to cast with either Risser or a Cotrel adult-sized frame, they are quite large for small children and are now rarely available.
A mirror slanted under the table is useful for visualizing the rib prominence, the posterior cast, and the molds.
We use a table designed for young children by Min Mehta, which supports the head, arms, and legs while the shoulders, torso, and pelvis remain free (FIG 4A).
Salt Lake City Shriners Hospital designed a custom table, which performs a similar function of supporting the child in traction while leaving the body free for the cast application.
Patients are intubated rather than using a laryngeal mask airway (LMA) because thoracic pressure during the cast molding can make ventilation temporarily difficult. A bite block prevents teeth from constricting the tube during head halter traction. Cover the head and neck to prevent plaster or fiberglass irritation.
A silver-impregnated shirt is used as the innermost layer and can either be custom-made or one made for scoliosis bracing such as a Boston brace shirt.
An abdominal pad made of stockinette prevents excessive abdominal pressure during the casting (FIG 4B).
Approach
Plaster is preferred for correction because it is highly moldable and expands slightly when setting unlike fiberglass, which shrinks.
In select patients, typically those with supine curves have been corrected to less than 20 degrees or those who are in casts which are holding rather than obtaining further correction, we use fiberglass with a waterproof liner and waterproof padding allowing the children to bathe and get in a swimming pool. The Gore-Tex pantaloon designed for spica casts works well as a shirt undergarment with the pantaloon legs used as the arms.
TECHNIQUES
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Head Halter-Pelvic Traction
Head halter-pelvic traction assists in stabilizing the patient and in narrowing the body. Even though traction can correct the curve while applied, the position cannot be retained in the cast once traction is released and the body recoils unless the cast also supports the occiput or the mandible (TECH FIG 1).
If the patient has a lumbar curve, the hips are slightly flexed to decrease lumbar lordosis and facilitate curve correction.
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TECH FIG 1 • Child positioned on the frame for the casting.
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Padding and Plaster Application
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A thin layer of cotton padding is applied with occasional felt on significant bony prominences such as the iliac crest or rib prominence (TECH FIG 2A).
For curves with an apex above T8, the shoulders are incorporated, and high thoracic curves may require an occipital-mandibular extension.
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TECH FIG 2 • A. Only a thin layer of padding is applied because it is the mold which prevents sheer and skin breakdown. B. The pelvis is molded well just above the iliac crests as the foundation of the cast against which everything else rotates.
It is a well-molded and snug cast rather than more padding that prevents sores as it is less likely to rub and cause pressure sores than an excessively padded, poorly molded, or loose cast.
As the plaster is applied, it is important to obtain a good mold over the iliac crests, as the pelvis is the foundation of the cast (TECH FIG 2B).
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Curve Correction
Although the Cotrel and Morel5 elongation-derotation-flexion (EDF) technique and Mehta14 both use an over-the-shoulder cast, we have had excellent success staying below the shoulders because most
infantile curves have low apices, typically at T10-T11 with results nearly identical to Mehta's.
For a typical left thoracic curve, the pelvis is carefully molded and stabilized while the left posterior thorax is rotated anteriorly, the right anterior thorax is rotated posteriorly and stabilized against the left pectoral girdle.
It is important that the cast does not compress the convex ribs toward the spine and consequently narrow the space available for the lung. Rather, the posteriorly rotated ribs are rotated anteriorly to create a more normal chest configuration with counter rotation applied through the pelvic mold and upper torso (TECH FIG 3).
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TECH FIG 3 • A. The technique of curve manipulation, which rotates the spine posteriorly and stabilized against both the pectoral girdle and the pelvis. It is important not to displace the ribs laterally into the spine and chest. B. Application of the plaster mold. (A: From Sanders JO, D'Astous J, Fitzgerald M, et al. Derotational casting for progressive infantile scoliosis. J Pediatr Orthop 2009;29:581-587.)
Proper casting corrects the curve through the rotation and a shift toward the midline without deforming the ribs toward the spine.
If the cast is found to be pushing the ribs toward the spine, we recommend it be removed and either reapplied or abandoned.
We cover the plaster with a layer of fiberglass both for color and strength.
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Windows, Trim, and Cast Edges
An anterior window is made to relieve the chest and a large abdominal window created to allow for
abdominal distention and breathing because younger children are diaphragmatic (belly) breathers while still preventing the lower ribs from rotating.
We have changed over time to larger abdominal windows trimmed to the inferior rib level because the abdomen does not provide additional support and it allows better breathing (TECH FIG 4A).
A posterior window is made on the concave side allowing the depressed concave ribs or transverse processes and spine to move posteriorly (TECH FIG 4B).
TECH FIG 4 • A. The anterior window captures the inferior ribs to keep them from protruding and leaves the abdomen as free as possible. B. The posterior windows allow the spine to rotate and help relieve excessive pressure. This particular patient had a double curve. C. A well-fitting cast in the patient when upright.
For under-the-shoulder casts, the superior trim line is at the manubrium. This is not as important for over-the-shoulder casts as long as the upper thorax is captured.
The lower trim line should be low enough to hold the pelvis securely while high enough to allow the hips more than 90 degrees flexion.
Lower trims prevent hip flexion and cause the cast to ride up when sitting, particularly in car seats that require significant hip flexion.
Once the child is awakened, the fit should again be assessed as it will shift slightly in an upright position. The child should be comfortable and find it easy to get around afterward (TECH FIG 4C).
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PEARLS AND PITFALLS |
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Difficulty ventilating during ▪ Make sure the patient is intubated and has a bite block. surgery
Troubles with trims ▪ Work with a cast technician who can do any final trimming once the child is awake and up after their body returns to a more normal configuration.
Skin irritation at cast removal ▪ Leaving off the cast overnight before recasting makes a big difference. A little light hydrocortisone cream can also help.
Patients sometimes need the ▪ In patients where this is likely, have a brace made from an cast removed for asthma or other intraoperative mold that the child could use if the cast has to respiratory issues. be urgently removed.
Parents expect a cure when the ▪ The parents must be educated in what to expect. |
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curve only decreases or stabilizes.
Cast sores ▪ Use broad distribution of forces during correction and leave no sharp edges. |
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POSTOPERATIVE CARE
Casting is done more frequently in younger than older children because they are growing faster. We typically change the cast every 2 months for children 2 years and younger, 3 months for those 3 years of age, and every 4 months for those 4 years and older.
Children are seen the day before cast application where the prior cast is removed and they are allowed to swim and bathe.
Casting continues until the curve is gone (<10 degrees) or has stabilized. Parents are informed before casting that the casting will continue for a minimum of a year. Radiographs
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are not necessary at every visit, as these children will often have large cumulative radiation doses.
Once the child is placed into a brace, the first brace is molded under anesthesia just like the casts by the surgeon.
OUTCOMES
In our patients, we found that 27% of casted patients resolved their scoliosis, 56% improved but did not resolved, 14% remained stable, and 3% progressed during casting.
Only 10% have had surgery, although this increases to 28% if considering only curves 50 degrees or more at the start of casting.
Among those who have had surgery, it was delayed by an average 2.7 years after the start of casting.
COMPLICATIONS
During casting, the major complications are pulmonary with increased pressures during plaster molding and setting. This is usually relieved once the plaster has set but is the reason intubation is important. The anesthesiologist must often apply positive pressure during the molding and plaster setting.
Postcasting pressure sores, although rare, are the major complication.
Many patients experience minor skin irritation which resolves overnight with cast removal.
Some patients, particularly those with asthma or other pulmonary disease, may require cast removal urgently to provide more chest expansion and access to their thorax.
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