Instability??

[Mary.Mary]

What are the signs and symptoms of Instability? Spinal Instability?

Anyone??

[Justin]

Hi Mary,

There is a great publication on instability and spinal fusion: Emedicine, Spinal Instability and Spinal Fusion Surgery, Author: Peyman Pakzaban, MD, Consulting Neurosurgeon, Houston MicroNeurosurgery; Chairman, Department of Surgery, Patients Medical Center (Link). Here are some excerpts quoted below:

In their widely-quoted work, White and Panjabi defined spinal stability as the ability of the spine under physiological loads to limit patterns of displacement so as to not damage or irritate the spinal cord and nerve roots and, in addition, to prevent incapacitating deformity or pain due to structural changes.2 Conversely, instability refers to excessive displacement of the spine that would result in neurological deficit, deformity, or pain. Instability can be acute (eg, spine fractures and dislocations) or chronic (eg, spondylolisthesis). Acute instability has been further subcategorized as overt versus limited, whereas chronic instability has been subdivided to include glacial instability (progressive deformity) and instability associated with dysfunctional motion segment.3

A simpler conceptual approach would be to think of instability as overt, anticipated, or covert.

Overt instability refers to excessive motion that is readily documented by radiographic studies and results in pain, deformity, or neurological deficit. Those spine fractures, dislocations, tumors, and infectious processes that significantly disrupt one or more spinal motion segments produce acute overt instability. Spondylolisthesis with abnormal dynamic displacement, documented on flexion/extension x-ray films, is an example of chronic overt instability. In addition, any spinal deformity (kyphosis, hyperlordosis, scoliosis, or spondylolisthesis) that progresses with time as documented by serial radiographs (ie, Benzel glacial instability) falls in the category of chronic overt instability. Overt instability generally requires stabilization, either by external means (bracing) or internal means (fusion).

Anticipated instability refers to instability that would be produced by a surgical procedure that is required for proper decompression of neural elements or resection of an offending lesion. For instance, corpectomy or total facetectomy would constitute indications for fusion at the time of the original operation. A comprehensive anterior cervical discectomy (with complete resection of the posterior longitudinal ligament and portions of both uncovertebral joints performed for adequate neural decompression) may also be considered in this category, as its disrupts 2 of Denis' 3 spinal columns.

Covert instability is a more elusive concept. It refers to circumstances in which excessive motion cannot be grossly demonstrated but is presumed to exist based on the combination of clinical and radiographic findings. Fixed spondylolisthesis (without movement on flexion and extension x-ray films) in the setting of progressively worsening back pain and/or radicular symptoms is a good example of covert instability. Pseudarthrosis with intact instrumentation also falls in this category. Controversy arises when the concept of covert instability is applied to degenerative diseases of the spine. In this context, the concept of micro-instability is sometimes evoked to justify fusion for a wider range of conditions, including recurrent disc herniation, disc degeneration with discogenic pain, painful facet arthropathy, spinal stenosis, and failed back syndrome without overt instability.

Kirkaldy-Willis provided a classification of degeneration of the spine based on 3 phases that inherently included spine instability:

The first phase, Phase I, is known as the Dysfunctional Phase. This phase is characterized by circumferential tears or fissures in the outer annulus. In addition, endplate separation or failure can disrupt the blood supply, resulting in the loss of nutrition to the disc. These changes are thought to result from repetitive microtrauma. One hypothesis is that the discs' nuclear proteoglycans lose the capacity to absorb water and maintain their protective function. Low back pain, low grade disc degeneration and laxity of the facet capsule is included in this phase.

Phase II, or the Unstable / Instability Phase, is characterized by multiple annular tears (both radial and circumferential), internal disc disruption, and resorption or loss of disc space height. This phase is thought to result from the progressive loss of the mechanical integrity of the 3-joint complex. Increased facet joint laxity and moderate disc degeneration is present.

Phase III is also known as the Stabilization Phase. Further disc resorption, disc space narrowing, endplate destruction, disc fibrosis, and osteophyte formation are present leading to decreased overall motion. Disc injuries are more likely to occur in phase I or II of the degenerative process. Disc degeneration has reached final stage (grades 3 to 4).

Source: Kirkaldy-Willis WH, ed. The pathology and pathogenesis of low back pain. Managing Low Back Pain. New York, NY: Churchill Livingstone; 1988:49.

I hope this helps.

[Mary.Mary]

Ok, thanks Justin!!

NOW, can I ask another question?

What are the signs and/or symptoms of Instability??

[Justin]

Ok, thanks Justin!!

NOW, can I ask another question?

What are the signs and/or symptoms of Instability??

OK, I'm not really sure what you are looking for here. If you notice in my post above, low back pain is one symptom of spinal instability, while a sign of spinal instability would be demonstrated on imaging.

Here's another source of information: Segmental Instability of the Lumbar Spine.