What is Lumbar Spine Instability?
Lumbar spine instability is one of the causes of chronic Low Back Pain (LBP). The degenerative changes in the disc (located between the two vertebras in front) and cartilage in the facet joint (located in the back of the spine) can result in the loss of joint space between the two vertebral bones. As a result the ligaments, which are responsible for holding and stabilizing the two spinal vertebras become lose and create laxity in that segment. It is important to know there is a difference between lumbar spine instability and hypermobility. Many times the hypermobility of the spine is mistakenly referred to as instability by patients and clinicians.
What is the difference between spinal hyper-mobility and instability?
The hypermobility of a spinal segment occurs when there is laxity in the ligaments of the spinal segment/s. This laxity can lead to excessive motion in the segment and create degenerative changes in the disc and facet joints. However, the anatomical relationship between the two vertebras remains intact. The x-ray of spine in flexion and extension movement in hyper mobile segment does not indicate any slippage of the top vertebrae on the bottom one in the involved segment.
In most cases physical therapy can help to reduce the hypermobility by improving the strength of the spinal stabilizer muscles to substitute for this hypermobility. This approach is especially helpful to those patients who are active but not involve in high level sports activities. The substitution of the ligamentous laxity by stronger muscles could be very helpful but it might not create enough stability for those individuals who are involved in high level sports activities.
The instability of a spinal segment is usually referred to as the laxity of ligaments and the slippage of top vertebrae on the bottom one. The x-ray of spine in flexion and extension could show forward or backward slippage (more often forward) and therefore loss of normal anatomical relationship between the two segments. In this case the neural tissues could be compromised and cause pressure on the spinal cord or the nerves that are existing from the spinal cord.
What are the Causes of Spinal Instability?
1) Degenerative changes in the disc and facet joints ( Spondylosis) cause loss of joint space and tightness in the ligament of the spinal segment and allow for the top vertebrae slides forward or backward on the bottom one.
2) Fracture in the pars-interarticularis ( where the top and bottom facet joints articulate) in the spine, which could be congenital or secondary to trauma.
In both cases if the top vertebrae slides 25% (level one Spondylo-lysthesis) the strengthening of the spinal stabilizers could be helpful to reduce pain and improve the stability. If the top vertebrae slide 50% or more on the bottom vertebrae the surgical procedure for fusing the unstable segment becomes necessary.
When physical therapy is indicated?
Physical therapy for strengthening the spinal stabilizer muscles and reducing compression load to the spine would be the first treatment option as long as anatomical relationship between the two vertebral bones in the spinal segment is intact or there is not more than 25% slippage in the spinal segment.
Most likely on average 8 visits of physical therapy should be adequate for improving the stability of the spine. Patients should continue with the home exercise program to maintain their strength in their spinal stabilizer muscle groups.