Normal and abnormal spine and thoracic cage development

Abstract

Development of the spine and thoracic cage consists of a complex series of events involving multiple metabolic processes, genes and signaling pathways. During growth, complex phenomena occur in rapid succession. This succession of events, this establishment of elements, is programmed according to a hierarchy. These events are well synchronized to maintain harmonious limb, spine and thoracic cage relationships, as growth in the various body segments does not occur simultaneously at the same magnitude or rate. In most severe cases of untreated progressive early-onset spinal deformities, respiratory insufficiency and pulmonary and cardiac hypertension (cor pulmonale), which characterize thoracic insufficiency syndrome (TIS), can develop, sometimes leading to death. TIS is the inability of the thorax to ensure normal breathing. This clinical condition can be linked to costo-vertebral malformations (e.g., fused ribs, hemivertebrae, congenital bars), neuromuscular diseases (e.g., expiratory congenital hypotonia), Jeune or Jarcho-Levin syndromes or to 50% to 75% fusion of the thoracic spine before seven years of age. Complex spinal deformities alter normal growth plate development, and vertebral bodies become progressively distorted, perpetuating the disorder. Therefore, many scoliotic deformities can become growth plate disorders over time. This review aims to provide a comprehensive review of how spinal deformities can affect normal spine and thoracic cage growth. Previous conceptualizations are integrated with more recent scientific data to provide a better understanding of both normal and abnormal spine and thoracic cage growth.

Keywords: Children; Early-onset spinal deformity; Growth; Spine; Thoracic cage; Thorax.

Figure 1

Sitting and standing height. From birth to age five, the development of the trunk is substantial. Between age 5 and puberty, the lower extremities grow more than the trunk and the spinal growth rate decreases from 2.2 to 1.1 cm/year. During puberty, the trunk grows more than the lower extremities. At the beginning of puberty, the remaining standing height is approximately 20 cm, of which 2/3 is at the level of the trunk and 1/3 is at the level of the lower extremities. At Risser I (menarche), the remaining growth of the trunk is approximately 3 to 4 cm.

Figure 2

Spine at birth. At birth, only 30% of the spine is ossified. At birth, the T1-S1 segment measures approximately 20 cm and reaches 45 cm at skeletal maturity.

Figure 3

Thoracic cage distortion and lung compression. Lung (A) and thoracic cage (B) growth volumes increase in a non-linear fashion over the first twenty years of life. The volumes of both structures are proportional to height in the absence of spinal disease. Spinal deformities alter normal spine and thorax growth, prevent the lungs from expanding and lead to thoracic insufficiency syndrome (C).

Figure 4

Early-onset spinal deformity. Thirteen-month-old female with progressive infantile scoliosis.

Figure 5

Controlled growth. Eight-year-old male with congenital scoliosis treated with “spine to rib” vertical expandable prosthetic titanium rib. Treatment of the growing spine is a unique challenge and involves preservation of the thoracic spine, thoracic cage, and lung growth without reducing spinal motion.