From the Research
The T4-T5 vertebrae level is distinct from the T4-T5 intervertebral disc level, with the disc sitting inferior to the T4 vertebra and superior to the T5 vertebra, serving as a cushioning structure between them. This distinction is crucial in clinical practice, as pathologies can affect either the vertebral bodies or the intervertebral disc, and precise identification of the level is necessary for procedures like epidural injections or identifying spinal lesions on imaging 1. The intervertebral disc contains the nucleus pulposus surrounded by the annulus fibrosus and functions to absorb shock, allow spinal mobility, and distribute forces between vertebrae, while the vertebrae themselves are the bony structures that provide structural support and protection for the spinal cord.
Some key points to consider:
- The thoracic spine was previously known as a relatively stable region in human spine, but several studies reported that the motion of the thoracic spine and changes in the cross-sectional area of the spinal cord changed with positions in the sagittal plane 2.
- The kinematic relationship between the thoracic disc and the space available for cord (SAC) with the positional change is still not well investigated, but a study using kinematic magnetic resonance imaging (kMRI) found that the mean value of the thoracic intervertebral disc area from T4-T5 to T11-T12 tended to be larger in flexion than in extension 2.
- A cadaver and radiological study found that the dimensions of the thoracic nerve roots vary greatly from T1 to T12 intervertebral discs, and sound knowledge of these anatomical features of the thoracic nerve is mandatory for thoracic spine surgery 1.
- A longitudinal MRI study found that progressive thoracic disc degeneration was observed in 63.1% of subjects, and was significantly associated with smoking and with cervical-spine degeneration 3.
In terms of clinical implications, accurate identification of the level of the T4-T5 vertebrae and intervertebral disc is essential for diagnosis and treatment of spinal pathologies, and can help prevent complications and improve patient outcomes 4.