About 80% of scoliosis cases belong to the group of so-called idiopathic scoliosis. Although the cause of this type of scoliosis is unknown, we know that asymmetric loading and gravity contribute to its progression.
It has been shown that adolescent idiopathic scoliosis (AIS) is eight times more common in girls than in boys.
Also, in cases with curves greater than 30 degrees, girls are ten times more likely to experience progression.
Scoliosis is the most complex deformity of the spine. The first change occurs in the sagittal, or side-profile, plane. There is a loss of the normal physiological curves. In people with scoliosis, reduced physiological kyphosis and lordosis are observed — the so-called flat back.
This deformity, adolescent idiopathic scoliosis, most often appears during the prepubertal and pubertal period and predominantly affects girls. Rapid growth and development are the most critical periods for the progression of this type of scoliosis. It is detected earlier in girls.
This is because when the growth spurt begins, the physiological curves in girls have not yet fully developed; in other words, the natural kyphosis and lordosis are still not formed. During this period, due to the lack of sagittal curves, the spine is unstable and there is a risk of deformities developing.
The levels of various hormones also play a role, including leptin, sex hormones, and others. Girls begin to mature earlier than boys and develop less muscle mass. Well-developed musculature acts as a protector of the spine.
In boys, the situation is somewhat different. Their rapid growth and development begin later, when the sagittal curves have already formed, which reduces the likelihood of the spine shifting and rotating sideways.
Understanding the different periods of growth and development helps answer the question of why adolescent idiopathic scoliosis, as a deformity, is more common in girls than in boys.
Infantile idiopathic scoliosis is observed in children between 0 and 3 years of age. Statistically, it is the rarest of all forms of idiopathic scoliosis and accounts for about 1% of all idiopathic scoliosis cases in children. Although the total number of cases is lower, around 60% of patients with infantile idiopathic scoliosis are boys.
Juvenile idiopathic scoliosis is diagnosed when spinal scoliosis appears between the ages of 4 and 10. It is less common than adolescent idiopathic scoliosis but more common than infantile scoliosis. Overall, it accounts for 10–15% of idiopathic scoliosis cases. Juvenile scoliosis is also more common in boys between the ages of 4 and 6, while between the ages of 6 and 10 it becomes more common in girls.
Finally, there is another common form of scoliosis that should be considered, affecting a very different age group. Older adults are at significant risk of scoliosis known as “de novo” or degenerative scoliosis. De novo scoliosis is caused by wear and damage to the intervertebral discs with advancing age and therefore affects a considerable proportion of the aging population. Studies show that up to 30% of people over the age of 60 are affected by this type of scoliosis. Although de novo scoliosis progresses much more slowly than childhood or adolescent scoliosis, it can still have a significant impact on quality of life if not treated properly. De novo scoliosis affects both men and women.
The conclusion we can draw is that throughout life, scoliosis occurs to a significant extent in both sexes.
