First, neutral spine is a biomechanically sound position in which the least amount of stress is placed on pain sensitive tissue. The weight of the body is absorbed by the weight bearing structures of the spine, which are the vertebral bodies. The vertebral bodies are designed to support and sustain large amounts of force. When proper spinal curves in a balanced posture (Figure 23) are present, the spine is actually stronger than when the curves are reduced or excessive. Neutral spine is a term that appears frequently in the literature, but to the dental professional the term may not be clearly defined or offer clear instruction.
Figure 23. Balanced Posture.
A healthy back has three natural curves; a slight forward curve in the neck (cervical curve), a slight backward curve in the upper back (thoracic curve), and a slight forward curve in the low back (lumbar curve). Good posture actually means keeping these three curves in balanced alignment. If the lumbar curve is reversed, the thoracic curve will increase and the head will translate forward creating a forward head alignment. With each inch that the head translates forward out of alignment, the weight of the head increases creating more demand on the cervical muscles and causing abnormal forces to pain sensitive tissue in the cervical spine joints, discs, and ligaments (Figure 24).
Figure 24. Forward Head Posture.
As previously mentioned, the cervical, thoracic and lumbar curves each measure approximately 30-40 degrees. Variations exist in age groups, but these values offer spinal stability. When the curves are in alignment, the joints are held in an optimal position to allow an equal distribution of force through the entire structure minimizing stress to pain sensitive tissue. The spine in a neutral position feels stable when vertically loaded. Here is an audio file to help in finding your neutral spine position.
Video 1. Finding a Neutral Spine Position.