The chest wall is a major component of the respiratory pump and consists of the rib cage and abdomen. It is inflated by the inspiratory muscles of the rib cage and the diaphragm and its integrity is key to sustaining ventilation. Disorders affecting the nonmuscular structures of the chest wall (the thoracic spine, ribs, costovertebral joints, abdominal wall, and sternum) may lead to respiratory dysfunction. When the integrity of these nonmuscular components is severely compromised, respiratory failure may ensue. The pathophysiology of disorders affecting these nonmuscular components is generally related to the imposition of excessive elastic loads placed on the respiratory muscles. In some disorders, such as kyphoscoliosis (KS) and obesity, the load on the respiratory muscles is chronic and progressive. By contrast, with flail chest, the load on the respiratory muscles is acute. If the respiratory muscles had not adapted or had little time to adapt to loads that increase the work of breathing, respiratory failure may quickly ensue. Other disorders, such as ankylosing spondylitis (AS) and pectus excavatum, have a minimal impact on respiratory function. Diseases directly affecting the respiratory muscles are discussed in Chapter 84.
Important physiologic and clinical considerations in kyphoscoliosis are discussed below.
KS comprises a group of spinal disorders that are characterized by curvature of the spine in the lateral direction (scoliosis) and sagittal plane (kyphosis) as well as by spinal axis rotation. It is a common spinal abnormality, with estimates of prevalence in the United States ranging from 1 in 10,000 people for severe deformities to 1 in 1000 people for mild deformities.1 The etiology of KS is unknown for the vast majority of cases (85% classified as idiopathic). With the remainder, KS is due to either neuromuscular disease (paralytic or secondary KS) or is congenital (Table 83-1).2–4
Table 83-1Causes of Kyphoscoliosis
Idiopathic KS usually manifests in late childhood or early adolescence and involves primarily females (ratio of 4:1).5 Individuals with idiopathic KS may complain of back pain or may have psychological problems.5 When KS is severe, complaints include dyspnea with exertion and constitutional symptoms related to nocturnal hypoventilation. Respiratory failure also may develop.6 Paralytic or secondary KS may be due to a number of neuromuscular disorders including polio, muscular dystrophy, cerebral palsy, and spinal bifida.4 With these diseases, KS typically occurs when the individuals become nonambulatory. Congenital KS results from developmental vertebral anomalies that are usually present at birth.3 Although uncommon, it ...