On the relation between thoracic kyphosis, athletic training, hamstring shortness, and anthropometry in the developing spine.

Abstract

Thoracic hyperkyphosis is a spine problem associated with back pain, trunk motion restriction, and cosmetic deformity. It is anecdotally linked to physical activity, which can augment the flexion moment applied to the thoracic spine by gravity, and through increased muscle activity, increase the compression forces acting on the vertebral centra. In adolescents, these changes may affect the development of the osteochondral and intervertebral tissues, leading to permanent vertebral wedging. Athletic training is one type of physical activity thought to extrinsically load the spine and contribute to the development of hyperkyphosis. Hamstring shortness has been anecdotally associated with spine deformity, as have certain anthropometric characteristics. In this dissertation, secondary analyses of the data from a cross-sectional study of 2,270 8-to-18 year-olds were used to investigate the associations between thoracic kyphosis, athletic training, hamstring shortness, and anthropometry. Originally, photogrammetric methods were used to measure the angles between pairs of lines tangent to thoracic and lumbar skin surface landmarks. Training time was self-reported, and hamstring muscle shortness (tightness) was determined using the Finger-to-Floor Reach Test. A direct relationship was demonstrated between thoracic kyphosis angle and annual training time, such that a 16% difference in annual training hours was associated with a 54% increase in thoracic angle. Subsequently, videographic methods were used to measure thoracic, lumbar, and hip angles via surface landmarks on 31 individuals ranging from 10 to 70 years. Hamstring-short subjects demonstrated posterior pelvic tilting and reductions in both lumbar lordosis angle and torso flexion range of motion. This lumbar flattening was associated with thoracic flattening, especially in younger, normokyphotic subjects, reflecting spine curve balance and an <italic>indirect</italic> relation between reach distance and thoracic angle. In older, hamstring-short hyperkyphotics with reach distances beyond about 140 mm, kyphosis angle tended to increase. This <italic>direct</italic> relation confirmed a link between hamstring shortness and thoracic kyphosis, suggesting an adaptive mechanism to enhance flexion range of motion. Finally, hyperkyphotic subjects tended to have longer thoracic spines, and hamstring-short subjects tended to have longer legs. Our findings may be useful for designing prospective studies to develop guidelines for athletic training program design and sports participant screening.