Let’s first look at the structure of your lower back so that you can understand how a spondylolisthesis will affect you.
The bones in your spine
Your lower back (lumbar spine) is formed by bones (vertebrae) stacked on each other. There are five lumbar vertebrae, called (L1-L5), and five sacral vertebrae, called (S1-S5). The five lumbar vertebrae are stacked on top of each other, like wooden blocks, and they are able to move. Whereas the five sacral vertebrae are fused together, like lego, and moves as a unit.
The vertebrae are not shaped like square wooden blocks, but resemble the shape of oxtail bones. They fit snugly on top of each other, like a 3D puzzle. If you look at it from the top, each vertebra has three parts:
- In the front you have the vertebral body – Large and thick to help carry weight
- In the back you have the vertebral arch – Designed to form a ‘tunnel’ or canal, where your spinal cord and nerves can run through
- Towards the sides you have bony transverse processes – Designed to enhance movement and muscles can attach to these processes
It is important to take note of the vertebral arch, as this is the part that will be affected by a spondylolysis and spondylolisthesis. The vertebral arch consists of:
- 2 Pedicles
- 2 Laminae
- 1 Spinous process
- 2 Transverse processes
- 4 Articular surfaces
The curve in your spine
Viewed from the side, your lumbar spine is curved forward. This curvature, called the lumbar lordosis, is normal. Without the curves in your spine, your spine would have been as straight as a broomstick. Now, imagine bending forward or backward if you had such a straight spine. Your movements would also be very stick-like.
Discs, ligaments, and nerves
Between each vertebra, there is a disc, made up out of a gel-like material. These discs act as shock absorbers when you walk, run and jump. They are responsible for increasing the available movement of your spine, without sacrificing the supportive strength of your vertebral column.
Inside the vertebral canal, you can find your spinal cord that runs all the way from your brain to your lumbar and sacral vertebrae. This thick cord of nerves connects your brain to the nerves in the rest of your body. Nerve roots branch out from your spinal cord and exits in between each vertebra.
To aid in the stability of our 3D block tower, numerous different ligaments connect one vertebra to the next. They criss-cross from one bone to the next, making sure each vertebra stays in place.
Lower back muscles
The muscles in your lower back can be divided into four groups moving your lower back in four directions (backward, forward, sideways and turning sideways)
- Extensors: Extensor spinae, spinalis Iliocostalis and multifidus
- Flexors: Rectus abdominis, external obliques, iliopsoas, internal obliques and transversus abdominis
- Lateral flexors and rotators: Quadratus lumborum, external obliques, internal obliques and intertransversarii