Review of Tests for Lumbar Spine InstabilityNo matter what the problem, treatment for health problems has the best results when it is aimed at the underlying problem -- not just the symptoms. Back pain is no different in this regard except there can be a lot of different reasons why someone has back pain.
Physical therapists who see the majority of people with back pain have started classifying patients with low back pain into specific subgroups or categories to help in this process.
One of the most common subgroups is called lumbar segmental instability (LSI). Lumbar refers to the low back region composed of five large vertebrae numbered one through five (e.g., L1, L2, L3, and so on).
Segmental means a specific one of those vertebrae is involved. And instability describes too much movement or translation of the bone. The shift of the bone can be seen on X-ray when the spine moves -- especially at the end of the spinal movement (e.g., bending forward/flexion or bending backward/extension).
The patient suffering from back pain as a result of lumbar segmental instability experiences a "catching" sensation when standing up straight after being bent forward. Another sensation described is one of the spine "slipping out" during spinal motion.
The pain is usually worse in the morning. Pain and slippage are key features when the person tries to roll over. And like a weather gauge, changes in the barometric pressure also increase painful symptoms.
What can cause lumbar segmental instability? Age-related disc degeneration, surgical spinal fusion, surgical removal of a disc, or a history of trauma affecting the spine. The reason spinal fusion causes instability may have to do with the increased load and stress on the segments above and below the fused level.
The condition is diagnosed based on the patient's history, physical exam (clinical tests), and imaging studies. But X-rays expose the patient to radiation, so physical therapists are trying to figure out which tests currently being used are accurate and valid enough to use without X-rays to confirm the results.
This group of therapists from New Zealand at the University of Otago conducted a systematic review of the literature. They looked back over the past 60 years worth of data entered on six different electronic databases.
Articles testing the accuracy of clinical tests for lumbar stability/instability were read and evaluated. There were 11 tests in all that met the criteria for high-quality research.
Physical therapists will recognize some of the tests included such as the posterior shear test, the prone instability test, the Beighton hypermobility scale, the prone leg extension test, and tests for the instability catch sign, the painful catch sign, and the apprehension sign.
They found that the tests were all specific enough (able to identify when lumbar segmental instability was NOT the problem). But the tests had low sensitivity meaning they weren't very good at identifying patients who DID have segmental instability.
One test did stand out as being the most sensitive (84 per cent) and with high specificity (90 per cent) -- the passive lumbar extension test. But in the end, the patient's symptoms (pain with certain movements like rolling over or standing up straight) and the timing of those symptoms (worse when the weather changed) actually had the highest sensitivity/specificity (88 per cent/93 per cent).
In summary, this systematic review to evaluate evidence for clinical tests used to diagnose lumbar segmental instability found limited diagnostic use for those tests. In the future, it will be necessary to compare tests for accuracy and reliability when used with different age groups and when performed by different examiners.
Once the condition can be accurately diagnosed, then finding the most effective treatment strategies will be the next step. The goal is to develop noninvasive testing methods and treatment approaches that don't involve exposure to radiation or surgery.
Abdullah M. Alqarni, PT, MPhty, et al. Clinical Tests to Diagnose Lumbar Segmental Instability: A Systematic Review. In Journal of Orthopaedic & Sports Physical Therapy. March 2011. Vol. 41. No. 3. Pp. 130-140.
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