732 Spine Alignment

lordosis

convex anteriorly and concave posteriorly

what two spinal segments are lordotic

cervical and lumbar

kyphosis

concave anteriorly and convex posteriorly

what two spinal segments are kyphotic

thoracic and sacrococcygeal

anatomical factors that influence the shape of the spinal curves throughout the vertebral column

• wedge shape intervertebral discs or vertebral bodies

• spatial orientation of facet joints

• histologic composition of ligaments

• degree of natural muscle stiffness

how is the spine during fetal development

primarily kyphotic

how does the vertebral column curves change during the lifespan

spine is primarily kyphotic during fetal development but lordotic curves develop with motor maturation

line of gravity

an imaginary line that runs from the head to the floor and falls on concave side of the spinal cords. This helps to maintain the natural curves of the spinal column

what anatomical landmarks does the line of gravity pass through

mastoid process, anterior to S2, posterior hip and anterior to knee

line of gravity posterior to lumbar spine

constant extension torque that facilitates lordosis

line of gravity anterior to the spinal cord

promotes flexion torque

what are external torques caused by to maintain spinal curves

due to the line of gravity

what are internal torques caused by to maintain spinal curves

due to muscle and connective tissue tension

what can alter sagittal plane alignment

disease, normal effects of aging, and faulty posture can alter sagittal plane alignment

what can happen to connective tissue structures when there are changes from ideal posture

may increase stress on muscles, ligaments, bones, discs, facet joints, and spinal nerve roots and may also affect volume of body cavities especially with exaggerated thoracic kyphosis

what are the main structures that influence posture

Lumbar spine and pelvic posture

slouched posture

posterior pelvic tilt with slightly flexed (kyphotic) lumbar spine

what may happen over time with a slouched posture

• stretch or weaken annular fibrosus reducing the ability to block protruding nucleus pulposus

• results in larger pressures in lumbar discs

• more protracted head

ideal sitting posture

more upright and extended thoracic spine facilitating more retracted (extended) base of cervical spine yielding more desirable “chin-in” position

what may happen over time with an ideal sitting posture

may also increase muscular stress at the base of the cervical spine

scoliosis

a deformity of the vertebral column that involves an abnormal curvature all three planes, most notably frontal and horizontal

functional scoliosis

corrected by an active shift in posture

structural scoliosis

fixed deformity cannot be corrected fully by active shift in posture