4 Late Sequelae of Untreated Pediatric Deformity
There is significant variability in the clinical presentation of adults with untreated pediatric deformity. In longitudinal studies on the natural history of late-onset idiopathic scoliosis, these patients have relatively limited disability compared with unaffected controls. 1 – 3 However, late sequelae of untreated pediatric de formity may also include symptomatic adult deformity, which can compromise health-related quality of life, particularly in the domains of pain and function, social roles, and mental health. 4 , 5 This significant and measurable compromise in health-related quality of life can be perceived as comparable or even worse than that of other chronic conditions such as diabetes, chronic lung disease, and congestive heart failure. 4 , 5 Patients dealing with the variability and uncertainty of the late sequelae of untreated scoliosis often make frequent visits to an adult spine surgery practice, and they express the following concerns: “Am I going to be disabled?” “If I get pregnant, is this going to worsen the scoliosis curve?” “Are my lungs being crushed by the curve?” “Am I going to end up deformed and hunched?” This chapter addresses these questions. Accurate information regarding the natural history of untreated pediatric deformity will empower patients and physicians to make informed choices regarding treatment options.
Curve Progression in Adolescent Idiopathic Scoliosis
The most rapid curve progression in adolescent idiopathic scoliosis (AIS) occurs during the adolescent growth spurt. After skeletal maturity, curve progression is typically noticed over a period of decades rather than months or years. In a longitudinal 40.5-year follow-up study of 102 patients with untreated idiopathic scoliosis, Weinstein and Ponseti 1 found evidence of curve progression after skeletal maturity in 68% of the curves ( Fig. 4.1 ). Patients who reach skeletal maturity with curves measuring < 30 degrees can be reassured that their curve is unlikely to progress in adult life. On the other hand, patients with curves measuring ≥ 50 degrees, particularly patients with thoracic curves between 50 and 75 degrees, should be followed periodically because they are more likely to continue to progress. 1 , 6 With advanced spinal degeneration, curves that have reached 80 to 90 degrees tend to stabilize and progress less rapidly. This is likely related to ankylosis of the apex of the curve, increased rigidity due to the effects of spinal degeneration, and “stability” provided by the rib cage contact with the ilium 6 ( Fig. 4.1 ).
Thoracic curves undergo the fastest rate of curve progression, especially curves measuring between 50 and 75 degrees. The average rate of progression is ~ 1 degree per year of life. For this reason, patients who reach skeletal maturity with curves > 50 degrees should be considered for surgical intervention 1 , 2 , 6 ( Fig. 4.2 ). Thoracolumbar and lumbar curves > 30 degrees tend to progress, but at a slower rate than thoracic curves, with an average progression rate of 0.5 degree per year of life. These curves have a higher potential to develop translational or rota tory listhesis, a factor commonly associated with pain symptoms. 1 , 2 , 6 In particular, lumbar curves commonly develop lateral listhesis at L3-L4 and L4-L5, a frequent cause of radiculopathy in these patients. 7 Although thoracic curves may progress more, lumbar curves are more likely to become symptomatic and lead to the need for surgical care. Finally, double major curves tend to be better balanced with age, and they demonstrate preserved coronal compensation.
Late cardiopulmonary compromise is the most concerning potential consequence of untreated scoliosis. Scoliosis is a complex three-dimensional deformity of the spine that can also affect the geometry and range of motion of the chest wall. 8 The respiratory muscles are placed at a biomechanical disadvantage, resulting in decreased chest wall compliance and restrictive lung problems. 9 Autopsy studies have shown evidence of restrictive lung disease in patients with severe spinal deformities, 2 including small airway disease, atelectasis, and sometimes lung atrophy. 10 The abnormal thoracic anatomy may also lead to distortion of the bronchial tree and even to direct compression of bronchi, resulting in extensive areas of hypoventilation. 9
Pulmonary function impairment secondary to thoracic or thoracolumbar scoliosis curves is proportional to the magnitude and rigidity of the curve, and to the severity of thoracic hypokyphosis. 6 , 8 , 10 – 12 In the Iowa 50-year follow-up natural history cohort, 3 22% of patients reported shortness of breath with activities of daily living. This was significantly more prevalent with curves > 80 degrees. These results are also reflected in a recent cross-sectional study of 492 patients with scoliosis (94% AIS), of which 10% had evidence of severe restrictive lung disease (forced vital capacity < 50%). 13 This group had significantly larger thoracolumbar curves (80 degrees in the severe impairment group versus 57 degrees in rest of the patients), and these curves were also significantly stiffer (flexibility of 29% in the severe impairment group versus 46% in the rest of the patients). A 20-year follow-up study of patients with untreated scoliosis also supports these conclusions, and further concludes that the percentage of decline in vital capacity (VC) is the strongest predictor of respiratory failure. 14
Abnormalities in pulmonary function tests reflecting restrictive lung disease can be observed in adult patients with even just moderate curves (40–60 degrees). 15 Although these patients may present with normal blood gas levels at rest, they also have marked abnormal ities of gas exchange during exercise, resulting in hypoxemia and hypercapnia. 16 , 17
The age of onset of the scoliosis plays an important role in developing cardiopulmonary failure. Excluding neuromuscular disorders, patient who develop cardiorespiratory failure are predominantly those whose curves were first noted prior to the age of 5 years. 18 Curve severity has an effect on lung development and function, particularly prior to the age of 8 years, with a negative effect on the growth and number of alveoli. 16 Patients with AIS are very unlikely to develop respiratory failure regardless of severity.
Pulmonary rehabilitation and respiratory and peripheral muscle training are necessary to increase the endurance and walking distance in these patients. 19 In extreme cases, noninvasive mechanical ventilation (NIMV) results in improved survival. 17