Kirkham B. Wood, MD. From the University of Minnesota, Minneapolis, Minnesota CLINICS IN SPORTS MEDICINE
More and more young people are participating in sports, especially women, who are involving themselves in increasingly strenuous and vigorous competitive activities at an earlier age than ever before.41 Knowledge about the effect sports have on the developing spine and about the capacity of a youngster afflicted with a spinal deformity to compete in sporting activities are especially pertinent today.
NORMAL SPINAL GROWTH
The growing spine increases in size and length by a combination of longitudinal and latitudinal growth. Individual vertebral bodies and their posterior elements enlarge circumferentially by a combination of appositional growth while they elongate by endochondral ossification. The primary ossification center of the vertebral body is initially associated with a spherical physis, similar to epiphyseal ossification.39 After birth, the ossification center enlarges towards the sides of the vertebrae and the intervertebral discs. Gradually, this spherical growth center expands to demarcate increasingly parallel growth plates at the cephalad and caudad ends of the vertebra. The physis remains the major mechanism for enlargement of the axial skeleton. The physis is principally involved with longitudinal growth; however, it also contributes to circumferential expansion of the centrum. There is a growthplate present anteriorly at eachneur ocentral synchondrosis and similarly posteriorly at the spinous processes, which allow increased length of the laminae and pedicles. These growth plates generally close much earlier so that the posterior elements are mature by the end of the first decade, and longitudinal growth anteriorly continues until age 16 to 18. If there are any asymmetric closures here, it may be a predisposing factor for spinal deformity. Latitudinal growth of the vertebrae occurs via two mechanisms: the perichondrium, which surrounds the body, and diametric growth within the physis and the adjacent epiphysis, both of which are responsive to physiologic and mechanical stresses.
SPINAL DEFORMITY (SCOLIOSIS, KYPHOSIS)
Despite extensive research, the etiology behind the development of idiopathic adolescent spinal deformities such as scoliosis and kyphosis (Scheuermann’s kyphosis) remains obscure. The prevalence of adolescent idiopathic scoliosis in the general population has been estimated to be between 2% and 3%.3, 56, 57 It is one of the most common childhood deformities and typically more common in girls than boys especially in the adolescent period (Fig. 1). Scoliosis is normally a painless condition no matter what the degree of curvature. It is not until the adult years that pain normally becomes any sort of factor in the process. Yet it is important to remember that many adolescents, including those with scoliosis, will report varying degrees of back ache on presentation. Hence, it is necessary to determine whether any pain complaints are in fact benign and not caused by the scoliosis itself. Other conditions that may be the cause of a painful deformity in a growing child include fracture, benign tumors (osteoblastoma, osteoid osteoma), syringomyelia, and malignancy. Scheuermann’s kyphosis is a developmental round back deformity principally of the thoracic spine, believed to be principally caused by abnormal growth and development of the vertebral endplates over many segments resulting in an abnormal increase in the normal thoracic spine4 (Fig. 2). Scheuermann43 first described the abnormal thoracic kyphosis as three consecutive anterior vertebral bodies wedged at least 5% each along with visible end-plate alterations, Schmorl’s nodes, and even apophyseal ring fractures. Its incidence has been estimated at between 2% and 8%.35, 44 As with scoliosis, milder degrees of kyphosis are normally well tolerated; however, as the degree of curvature increases, or if the deformity comes to involve parts of the lumbar spine, pain reports become more frequent and in advanced cases may be severe enough to limit the patient’s participation in sports.