A normal structurally stable spine sports 3 natural curves: the cervical lordosis, the thoracic kyphosis, and the lumbar lordosis (Figure 1). Each curve measures approximately 30-40 degrees. These curves provide the spine with structural stability making the strong vertebral bodies the weight bearing structures of the spine. Without these curves, or a spine with significantly less or more curve, pain-sensitive tissues become the weight-bearing structures and over time lead to pain and possible pathology (Figure 2).
Figure 1. Normal Spinal Curves.
Figure 2. Reduced Cervical Lordosis.
Additionally, the spinal column contains many parts and spaces. First, let’s look at what composes a spinal segment. A spinal segment is made up of 2 vertebral bodies with an intervertebral disc in between (Figure 3). The disc provides shock absorption, nutrition to the vertebral endplates, and occupies a space between the 2 vertebrae that maintain the patency of the intervertebral foramen (Figure 4).
Figure 3. Spinal Segment.
Figure 4. Intervertebral Foramen.
The patency of the foramen is crucial as the nerve root exits the spinal cord and comes out the intervertebral foramen. Any compromise or stenosis of this foramen may cause sensory and/or motor impairments in the target tissues supplied by the peripheral nerve (Figure 5). Later we will discuss further the common pathologies associated with dysfunctional or degenerative spinal segments. A facet joint is made from 2 facets, one facet from the superior vertebrae and the second from the inferior vertebrae. These two facets articulate together to form the joint (Figure 6).
Figure 5. Stenosis.
Figure 6. Facet Joint.
This joint is what is commonly referred to with the term degenerative joint disease. Finally, the spinal canal is the space occupied by the spinal cord. The nerve roots branch off the spinal cord and exit out to the periphery through the intervertebral foramen.