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1st Aug

2019

Understanding Low Back Pain: Current Research and Targeted Treatment

In this newsletter, I will discuss important research findings and points of views, presented at an international research and clinical expert forum in Chicago, 2015, and published in the June 2019 issue of Journal of Orthopaedic & Sports Physical Therapy. I will also discuss how I believe these findings can best be addressed, when designing an effective treatment program.

In order to improve clinical diagnosis and to personalize treatment, many researchers have attempted to divide people with low back pain into subgroups, and recommend a certain treatment for each subgroup. However, there is insufficient consensus of how to do this, and no strong evidence yet for the effectiveness of subgroup-based treatment. Others, myself included, suggest that there is considerable overlap between such subgroups, and low back pain typically involves a myriad of factors, which contribute to people’s symptoms, disability and quality of life, and multidisciplinary treatment and physical therapy targeting each patient’s unique condition and circumstances, is often needed, except perhaps for the most benign cases.

A few simple subtypes of clinical presentation have been described, including one where people have increased stiffness and muscle tone, and reduced mobility; as opposed to those who have excess mobility, and often reduced muscle tone and neuromuscular stability. In such cases, the former would benefit the most from treatment to decrease muscle tension and improve mobility (e.g. through soft tissue mobilization and passive and active joint mobilization), whereas the latter group would require more neuromuscular stabilization treatment (e.g. motor control training and stabilization exercise).

However, in my experience, these factors fall on a spectrum, and most people with low back pain need a combination of such treatment. The same goes for a person’s degree of inflammation or neurological sensitivity, which must be assessed, and treated with specific dosage in order to be effective.

From a neurological point of view, low back pain is today often grouped into nociceptive pain, neuropathic pain, or nociplastic/central sensitization pain. Nociceptive pain refers to pain originating in tissues other than the nervous system, perceived by us from the stimulation of nociceptive fiber receptors in tissues, usually due to something compromising such tissues. Neuropathic pain describes pain due to compromised somatosensory nervous system, such as nerve roots in the spine. Nociplastic pain or central sensitization describes the phenomenon where there is altered sensory processing in the brain, and altered function of neural pathways in the spinal cord, resulting in more widespread and intense/unpleasant pain experience which may be provoked by even benign activities which cause no tissue trauma. This commonly is accompanied by other physiological changes such as glial cell activation, and neuroimmune and neuroinflammatory responses.

Again, often times we see a combination of such neurological pain subtypes, which all need different specific rehabilitation and medical treatment.

From a biological point of view, certain changes occur, which are crucial to address with physical therapy treatment. Most research today confirm that the deep fibers of the multifidus muscle in the low back (key stabilizing muscles) rapidly get inhibited after the onset of acute low back pain. Studies have shown significant atrophy (shrinkage) of these muscles within a few days following onset of acute pain. Other studies have also shown that early gentle specific exercise to activate the multifidus, is sufficient to restore the multifidus size reasonably quickly, whereas general exercise does not accomplish this. This evidence is a strong reason to initiate early rehabilitation after the onset of acute low back pain.

Research has also shown, that in chronic low back pain, the deep fibers of the multifidus (the shortest muscle bundles, being the most effective segmental stabilizers) gradually transition from being predominately type I slow twitch endurance, to type II fast twitch muscles. One significant problem with this, is that only type I muscle fibers receive reflex activation to create joint stability. This occurs simultaneously with increased muscle tone and tightness of the more superficial and longer back muscles. We also start to see fatty infiltration and fibrous tissue ingrowth in these deep multifidus muscles, in part due to chronic inflammation and disuse.

Often making things worse, an emerging overlap of regions in the brain that represent the deep and superficial back muscles, makes it difficult for many people to selectively activate the deep multifidus instead of the superficial muscles.

As a result, the sum effect is loss of segmental stability in the lower back, yet increased spinal load due to the increased tightness of the superficial back extensor muscle fibers, which cannot produce segmental joint stability.

As some authors point out, specificity in treatment is a key, to deactivate the superficial back muscles, while activating the deep multifidus fibers, then decrease inflammation and to the extent possible reverse the build up of fatty and fibrous tissues in these deep muscle fibers, and finally restore both endurance (restore type I muscle make up) and strength of these muscles, which work in synergy with the deep abdominal muscles.This is all done with specifically dosed and targeted gradually progressed exercise. We know today, that general exercise cannot do this, although it can have other beneficial effects, such as a general anti-inflammatory effect.

I should also point out, that studies have shown a correlation between having more frequent episodes of recurrent low back pain, and having more pronounced fatty infiltration of the multifidus, indicating lower contractile ability of this muscle. Consequently, proper rehabilitation is important in prevention of long term low back pain and disability.

There is, of course, much more to low back pain rehabilitation than what has been discussed here, some of which I have described in past newsletters.

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