Scoliosis and the biomechanics for positive corrections

Induce positive corrections by understanding the spine’s physical compensation mechanisms

Scoliosis is a three-dimensional manifestation of aberrant spinal biomechanics  — axial (top), sagittal (side) and coronal (front). Surgery and bracing usually address the one-coronal dimension.

Adolescent idiopathic scoliosis, in my opinion, is caused by abnormal spinal biomechanics along with a neurological component, but here we will solely address spinal biomechanics.

Spinal strength and compensation

When we look at the spine from the front, it should be straight. When we look at the spine from the side, there should be good curves — the neck or cervical spine curves forward, which is a lordosis. The middle back or thoracic spine curves backward, which is a kyphosis. The low back also curves forward in lordosis. The sagittal curves of the spine give the spine strength and flexibility (or, C-squared plus 1 = resistance). The center mass of the skull at the sella turcica is anterior to the atlas. The sacrum is a kyphosis and relates to Ferguson’s angle. The spine then has five curves. 

Five squared + 1 = 26, so the spine is 26 times stronger if straight, or 13 times stronger with the fetal curve at birth (1 squared = 1 + equals 13). 

When the spine loses the good curves, it compensates by putting in bad sideways curves (scoliosis). In order to correct the bad curves, the good curves must be reintroduced. Eighty-eight percent of patients with a Cobb angle above 30 degrees have a kyphotic neck compared to 2 percent in the general population.

One tough mother

This cervical kyphosis or loss of the cervical curve lengthens the spinal canal by 24 percent. The spinal canal is the “home” or environment to the spinal cord. The meninges are a strong sock-like covering that goes around the brain and the spinal cord. One part of the three-part meninges is called the dura mater. Dura mater means “tough mother” in Latin, and it consists of very strong diagonal fibers that act like a Chinese finger pull when stretched and may compress the spinal cord by 30-40 percent. This traction and compression cause an adverse mechanical tension on the delicate spinal cord.

In response, the spine will twist and turn to reduce this tension. In the thoracic spine, lateral flexion and rotation are a coupled motion. As the spine bends to the left, the spinouses of the vertebras will rotate to the right. Scoliosis spines have abnormal spinal biomechanics and instead of rotating toward the convex curve, they rotate into the concavity. The body does this to reduce adverse mechanical tension, as it is easier “to go through the valley than over the hill.” 

This abnormal rotation is responsible for the rib hump or arch in scoliosis.

Due to the rib attachments, the thoracic spine has limited motion in flexion and extension. Lateral bending is the primary motion. There is a reciprocal influence of lever arms in the spine — as the cervical spine becomes straighter, the thoracic spine becomes straighter, and eventually the lumbar spine becomes straighter. As Isaac Newton said, “for every action there is an equal and opposite reaction.”

Anterior adjusting

The anterior movement of the thoracic spine is known as lordotization, diminished kyphosis, hypokyphosis, anterior thoracic subluxation, anterior dorsal syndrome or Pottenger’s saucering. Scoliotic spines have this anterior movement of the thoracic vertebras, and an increase in lordotization equals an increase in the Cobb angle.

Posterior to anterior thoracic adjusting is contraindicated in scoliosis patients, including adjusting the “high side of the rainbow.” By understanding the spinal biomechanics of scoliosis, it is possible to introduce positive corrections to the scoliosis patient. 

Dennis Woggon, DC, BS, graduated cum laude from Palmer College of Chiropractic in 1974 with a bachelor of science degree in biology. He began CLEAR Institute in 2000, which has become a nonprofit organization to teach the public and chiropractors how to help scoliosis with chiropractic. (CLEAR stands for Chiropractic Leadership, Education and Research.) The goal of CLEAR Institute is to implement an effective chiropractic system of scoliosis care to help people worldwide through research and spinal rehabilitation.