Idiopathic scoliosis

Idiopathic is the most common type of scoliosis in children and adolescents; 2–3% of children have idiopathic scoliosis. The term idiopathic implies that the cause remains unknown. The deformity involves all three planes as the vertebrae at the apex of the curve are rotated towards the convexity of the scoliosis.

Children with idiopathic scoliosis can develop a single thoracic, thoracolumbar or lumbar curvature, or multiple curves along the spine. In the thoracic region, the effect of the rotational deformity of the spine is usually the development of a significant rib prominence. This is in addition to an elevation of the shoulder line and protrusion of the scapula adjacent to the convex side of the curve, as well as elimination of the normal thoracic kyphosis, which together create most of the cosmetic element of the deformity. Thoracolumbar and lumbar curves produce an asymmetry of the waistline and prominence of the pelvis adjacent to the concavity of the scoliosis, and this is usually the patient’s first complaint. In contrast, double thoracic and lumbar curves are often diagnosed late as they are balanced and cosmetically less obvious.

Clinical presentation and prognosis

Infantile idiopathic scoliosis

This has two distinct patterns of development. Some 80–90% of curves resolve spontaneously with further growth and do not require treatment other than observation. The remaining 10–20%, however, show rapid progression, are usually resistant to conservative management with a spinal jacket or a brace, and require early surgical treatment. Male and female patients are equally affected. Surgical treatment is indicated in older children with progressive curves or in children with more severe deformities where the use of growing rods can delay spinal fusion for a later age and preserve spinal growth (Fig. 26.1). If left untreated, infantile scoliotic curves will exceed 100° by the age of 10 years and patients can die from cor pulmonale in early adulthood.

FIGURE 26.1 Preoperative and postoperative antero-posterior radiographs of the spine show a very severe left thoracic infantile idiopathic scoliosis, which was corrected with the placement of a growing rod with the aim to control the deformity and allow for further growth. At a later stage a definitive spinal fusion will be required to stabilize the spine. The patient’s age was 2 years 4 months before surgery

Adolescent idiopathic scoliosis

Females are more commonly affected than males, and for a curve greater than 20° the ratio is approximately 4 : 1. The children are born with a straight spine and start developing a scoliosis close to puberty. As they go through their adolescent growth spurt, the deformity progresses more rapidly and becomes clinically apparent. The most frequent pattern of deformity is a right thoracic scoliosis (80–90%). A left thoracic scoliosis is regarded as atypical and other underlying causes, such as spinal dysraphism, should be excluded. Risk factors for curve progression include a younger age or a larger curve magnitude at detection, and are directly related to the amount of remaining growth. Patients who have a rigid thoracic scoliosis often have decreased lung volume, but this is not usually a clinical problem and does not interfere with the level of the patient’s activities. In contrast, an adolescent idiopathic thoracic scoliosis that exceeds 90° can cause clinically significant respiratory compromise.

Radiographic evaluation

Obtain antero-posterior (AP) and lateral radiographs of the spine with the patient standing to document the type and location of the scoliosis. The magnitude of the curve can be measured using the Cobb method in both the coronal (frontal) and the sagittal (lateral) planes of the spine (Fig. 26.2).

FIGURE 26.2 Cobb angle. The vertebrae at either end of the curvature are located and lines drawn from the superior surface of the uppermost vertebral body and the inferior surface of the lowermost vertebral body. The perpendicular lines to the superior and the inferior end-plates of the two end vertebrae included in the curve are used to form the Cobb angle

The Cobb angle and the amount of remaining spinal growth are essential guides to treatment and scoliosis progression during follow-up. Preoperative MRI of the whole spine extending from the foramen magnum proximally to the sacrum distally is required for patients with abnormal findings on neurological examination, an atypical curve pattern, for children with abnormalities of the skin or subcutaneous tissues overlying the spine, or for patients with an infantile or juvenile scoliosis.

Young children with infantile scoliosis or patients with very severe curves, and especially those who will require a combined anterior and posterior spinal fusion, may also require a preoperative cardiopulmonary assessment.

Treatment

The aim of management of scoliosis is to ensure that a child does not enter adulthood with a significant curve (Table 26.1). Observation is indicated for growing patients with small adolescent idiopathic scoliotic curvatures of up to 20–25°, a minimal cosmetic deformity and otherwise normal findings on clinical examination.

Table 26.1 Guidelines for treatment for patients with an adolescent idiopathic scoliosis

Magnitude of Curve (°)	Treatment
<20–25	Observation
25–40	Bracing
>40–50	Surgical correction and fusion with instrumentation and bone graft

Bracing with a lightweight, detachable, custom-moulded, underarm orthosis can be used in a growing child who has a moderate curve ranging from 20–25° up to 40° and whose apex lies below the level of the sixth thoracic vertebra. The aim of a brace (see Chapter 7) is to modify spinal growth and stop curve progression. Brace management cannot lead to resolution of the scoliosis and, at best, will maintain the size of deformity seen at the initiation of bracing. Therefore, the indication for bracing is for small-to-moderate curves that are cosmetically acceptable at the time of initial diagnosis. The child is asked to wear the brace for approximately 20 hours a day until skeletal maturity. Compliance can be a significant problem.

Surgical correction should be considered if the curve is greater than 40° and likely to deteriorate with remaining spinal growth, or if there is an established scoliosis greater than 50°. The aim of surgery is to prevent further deterioration by stabilizing the spine and to correct all the components of the deformity (spinal curvature, rib prominence, shoulder or waistline asymmetry, thoracic translocation and listing of the trunk). This can be achieved with the use of spinal instrumentation and bone grafts to produce a solid bony arthrodesis (fusion) across the instrumented levels (Fig. 26.3). The general principle when selecting the extent of the fusion is to try to maintain as many mobile segments as possible to preserve spinal flexibility.

FIGURE 26.3 Preoperative and postoperative antero-posterior and lateral radiographs of the spine showing a severe right thoracic adolescent idiopathic scoliosis, which was corrected with a posterior spinal fusion

After surgery children are mobilized as soon as possible and bracing is not usually necessary. A small proportion of patients may have to wear an underarm spinal jacket or brace if the fixation of the spine is not secure enough.

Congenital scoliosis

Congenital scoliosis is caused by developmental vertebral anomalies that occur in the mesenchymal period, during the first 6 weeks of intrauterine life, and produce a lateral longitudinal imbalance in the growth of the spine. Although the vertebral anomalies are present at birth, the clinical deformity may not become evident until later childhood. The anomalies can affect any part of the spine and are classified as defects of vertebral formation or vertebral segmentation, and mixed anomalies (Fig. 26.4). These malformations often cause a structural deformity in one or two planes and a progressive curvature as the spine grows. As the child grows, a structural compensatory scoliosis often develops above or below the congenital scoliosis, and creates a more significant imbalance of the spine.

FIGURE 26.4 Classification of congenital scoliosis

Congenital scoliosis may also be associated with congenital malformations affecting the intraspinal neural structures (up to 40%), genitourinary (25%) and cardiac (10%) systems, cervical spine (Klippel–Feil syndrome – 25%) and shoulder (Sprengel’s deformity – 7%).

Congenital scoliosis is usually progressive and does not respond to conservative management. It is impossible to create growth on the concavity of the scoliosis where it is either retarded or non-existent due to malformation, and the aim of surgery is to balance spinal growth by stopping the accelerated growth on the convexity of the curve. The key to successful treatment is early diagnosis while the curve is still small and there is an opportunity to balance the growth of the spine prophylactically (Fig. 26.5). If the patient presents with a more severe deformity at a later stage, salvage surgery will be required and usually involves an extensive spinal arthrodesis and a suboptimal outcome.

FIGURE 26.5 Preoperative antero-posterior radiograph and magnetic resonance image of the spine showing a left L1 hemivertebra (black arrow). Posterior resection of the hemivertebra and segmental fusion with instrumentation resulted in a normal spinal balance in both the coronal and the sagittal planes

Neuromuscular scoliosis

Neuromuscular scoliosis occurs in patients with upper or lower motor neurone lesions, and in muscular conditions (Table 26.2). The spinal deformity is the consequence of a generalized muscle weakness affecting the trunk, with or without associated spasticity, and the effect of gravity. This type of scoliosis is typically characterized by an early onset with rapid progression and a poor response to orthotic management, particularly during the adolescent growth spurt. The scoliosis that develops is a long ‘C’-shaped curve with the apex most frequently located in the thoracolumbar spine, and can occasionally be associated with an increased kyphosis or lordosis. The curve commonly extends to the pelvis causing marked pelvic obliquity.

Table 26.2 Incidence of neuromuscular conditions associated with scoliosis

The deformity of the trunk and the pelvis may add to the child’s functional loss from their underlying disorder. The spinal mal-alignment and trunk decompensation can affect standing balance in ambulatory patients and limit their ability to walk. In non-walkers, the imbalance can lead to sitting intolerance and cause a child to become a hand-dependent sitter. It can also produce pain from impingement of the ribs against the iliac crest on the concavity of the scoliosis as the spine collapses and the pelvic obliquity progresses. Scoliosis in this group of severely disabled children may create cardiopulmonary complications and deteriorate pre-existing feeding disorders.

The management of neuromuscular scoliosis is directed at maintaining or improving functional abilities and the quality of life. Bracing may provide trunk support and improve posture, but does not prevent curve progression. Seating can be adapted to accommodate the spinal deformity, but also does not correct the deformity. Trunk support and seating modifications can be used as a temporizing measure to maintain function in young children with flexible deformities, to allow further spinal growth and delay surgery. Spinal fusion is the only treatment that is effective in these patients and involves an extensive spinal arthrodesis with instrumentation and allograft bone. It is indicated to improve seating stability, maintain function, improve the quality of life and prevent cardiorespiratory compromise (Fig. 26.6). A multidisciplinary approach is essential when surgical treatment is anticipated to reduce the significant risks of potentially life-threatening complications that can occur in the perioperative period.

FIGURE 26.6 Preoperative and postoperative clinical photographs and antero-posterior radiographs of the spine show a typical severe long ‘C’-shaped right thoracolumbar neuromuscular scoliosis with significant associated pelvic obliquity causing impingement of the ribs against the iliac crest on the concavity of the scoliosis in a patient with quadriplegic cerebral palsy. A posterior spinal fusion was performed and resulted in correction of the scoliosis and a level pelvis