7.1.1 Incidence

CP is one of the most common chronic childhood disabilities in the developed world, with an incidence of 2 to 2.5 per 1,000 live births. ² Reported scoliosis prevalence rates range from approximately 15 to 80% depending on the severity of neurologic involvement (i.e., GMFCS level), patient age, and functional status. ^{3 ,​ 4 ,​ 5 ,​ 6 ,​ 7} There is an association between increasing incidence and severity of scoliosis and degree of involvement of neurologic impairment as it relates to the GMFCS level. However, this may represent a confounding effect, which can be explained by the findings of Persson-Bunke et al. ⁸ They analyzed the association between the development of scoliosis, GMFCS level, CP subtype, and age at diagnosis of scoliosis in a population of children with CP. ⁸ They found that the proportion of patients with scoliosis increased with GMFCS level, but that there was no significant association with scoliosis and CP subtype independent of GMFCS level. In their series, only children with GMFCS levels IV and V developed scoliosis of greater 40 degrees. There is value in subclassifying GMFCS level V on the basis of axial motor functions. Jain et al ⁹ has shown that additional motor impairments in feeding (presence of gastrostomy tube), airway control (presence of tracheostomy), speech (nonverbal status), and cortical instability (seizures) may be tabulated to produce subscores from 5.0 to 5.4. These predict health-related quality-of-life scores and risk of complications and death in surgically treated patients.

7.1.2 Natural History

The cause of neuromuscular scoliosis in CP is related to muscle weakness, spasticity, impaired motor control, truncal imbalance, and impaired sensory feedback. ^{10 ,​ 11 ,​ 12 ,​ 13} These factors may lead to asymmetric spinal forces, and, initially, children will present with flexible, postural curves. ^{11 ,​ 13} Persson-Bunke et al ⁸ found that the prevalence and risk of developing moderate or severe scoliosis was related to age and GMFCS level. They found that children at GMFCS level IV or V have approximately 50% risk of clinically moderate or severe scoliosis at 18 years of age. Although most children are diagnosed after 8 years of age, many children develop substantial curves in the juvenile or infantile period (Fig. 7‑1 a, b).

More severely involved children (GMFCS levels IV and V) tend to have long, C-shaped curves, which lead to imbalance of the pelvis. ^{11 ,​ 14} Curves that occur earlier (before 15 years of age) tend to progress more rapidly and result in larger, stiffer curves. ^{6 ,​ 15} The rate of progression may increase dramatically to as much as 2 to 4 degrees per month during the adolescent growth phase. ^{6 ,​ 16} As a patient’s curve becomes larger with age, a structural component develops. One must also consider that patients with CP may begin puberty much earlier or later than typically developing children, and the age of skeletal maturity may also vary widely. ^{5 ,​ 7 ,​ 17 ,​ 18} In addition, spinal deformity in patients with CP may progress after maturity. Thometz and Simon ⁷ found that patients with the largest curves (>50 degrees) at the time of skeletal maturity had the largest curve progression.

7.1.3 Functional Effects of Scoliosis in Children with Cerebral Palsy

Scoliosis in patients with CP may contribute to major limitations in function, activity, sitting, standing, comfort, self-image, and social perceptions. The concept of form following function is useful in understanding some of the physical impairments of patients with CP. Patients with a single, long spinal curvature tend to experience trunk decompensation, limiting the ability to sit upright without support. ¹² Pelvic obliquity can result from unbalanced curvature and can lead to abnormal pressure distribution. ^{12 ,​ 14} A balanced, erect sitting position is essential for improved health and activity in patients with CP because it maximizes use of the upper extremities, communication, vision, and feeding. Upright position optimizes gastrointestinal function by decreasing aspiration and reflux with gravitational assistance. ¹²

An unbalanced seating position leads to excessive pressure on the skin overlying the ischial tuberosity or, in more severe cases, over the greater trochanter. ¹² This alteration in pressure distribution can cause decubitus ulceration of soft tissues, especially if the child is unable to communicate. ¹⁴ Patients with rib prominences resulting from scoliotic rotational deformities often experience discomfort at contact points with the iliac crest, as well as with chairs and braces. ^{12 ,​ 13} The resultant pressure ulcer and abnormal contact points may produce severe discomfort and pain. Furthermore, the ability to perform basic functions, such as looking forward or at keyboards, swallowing without aspiration, and communicating, depends on an upright sitting position. ¹¹ Nonambulatory patients also have decreased functional capacity as a consequence of their increased reliance on their upper extremities for balance and physical support. ^{10 ,​ 11 ,​ 13}

The degree and nature of spinal deformity can affect the overall health status and comorbidities of patients with CP. Several studies have suggested that substantial scoliosis also leads to impairment in cardiopulmonary function. However, Kalen et al ⁴ compared patients with CP and untreated scoliosis of Cobb angles greater than 45 degrees to those CP patients with mild or no scoliosis and found no significant difference in pulse, oxygen saturation, functional loss, or incidence of decubiti. They noted that adult CP patients without scoliosis had no better cardiopulmonary function than those with scoliosis and lost as much functional ability over time. It is important to consider that the scoliosis itself may not be the cause of the functional impairments but may simply represent an additional symptom of the neuromuscular dysfunction in patients with CP. ⁴

7.3.1 Spinal Orthoses

Bracing is used in patients with CP with the goal of providing postural support and potentially delaying curve progression to allow for optimal timing of definitive spinal surgery. There is conflicting evidence regarding the efficacy of bracing, with some authors supporting the idea that brace use may slow curve progression ¹⁶ and others refuting this claim. ¹¹ Most authors recommend the use of a soft brace given that the goal of bracing is to provide postural support, not correction of the curve. Rigid orthoses can lead to problems with skin integrity, pulmonary function, and gastrointestinal function. ^{9 ,​ 10 ,​ 12} Braces are still widely used for children with curves in the 30- to 60-degree range with the hope of providing periods of support or comfort, or of slowing the curve. ^{11 ,​ 16} However, experience has shown that children can rarely tolerate bracing for periods longer than 8 hours per day. Most experienced orthopaedists still use orthoses as part of nonoperative care.

7.3.2 Seating Modification

Supportive features of a wheelchair can help enable better sitting. These include lateral supports, head rests, chin supports, vests, variable-angle seatbacks, custom-molded backs and seats, and tilt-in-space systems. These features can optimize function and delay or even prevent the need for surgery. ¹³ Prescribing these modifications is a technical specialty, best done in combination with a physical therapist and technician.