Part 1 of 2
WHAT DO WE KNOW ABOUT BACK PAIN?
Back pain is a common condition that affects 60 to 80% of the general population at some point in their lives. It begins very early in life affecting children and teenagers, and becomes more prevalent among people in their 50s and 60s. Back pain troubles the elderly and its prevalence is around 30 to 40% in that patient population. All these numbers suggest that most back pain results from a biological process that begins in adolescence and continues throughout adult life. It is probable that progression of age-related degeneration of the spine structures, such as the intervertebral discs, is the offending process that periodically stimulates a person’s pain system and produces back pain.
Of interest, 20% of the population denies ever experiencing back pain. This is most surprising as they deny past or current back pain even when they have severe spine problems such as disk herniation or spinal stenosis. Apparently, these people are insensitive to the degenerative process that produces back pain in the vast majority of people.
Could this insensitivity be harmful? Pain is generally a protective experience that helps to limit physical stresses on repairing tissues. Insensitivity might deny people of this protective pain experience, and accelerate spine degeneration. Surprisingly, this is not the case, as those without histories of back pain do not have greater degeneration than those who experience back pain. This suggests that back pain, for those that can feel it, may not be biologically protective or beneficial, and it may not signal the need for mandatory rest or reduced activities.
WHY DO WE SEE SO MANY DIFFERENT PRESENTATIONS OF BACK PAIN IN OUR PRACTICE?
Research suggests that the strongest factors that influence the risks for back pain are likely genetic. For identical twins, if one twin has problems with back pain, there is a six times greater risk of the other twin to also have back pain. It has also been observed that some families have lots of members with back pain while other families do not, and that this difference is not explained by the degree of spine degeneration, the types of work they do, or any physical exposure that might cause stress in the back. This suggests that it is likely that the risk of back pain is based on genetic differences that effect the sensitivity and adaptive abilities of the pain system responsible for monitoring the back. This response differs from person to person and could explain why physicians see so many different presentations of back pain in their practice and also why 20% of the population seems resistant to back pain.
WHAT IS THE TRUE RELATIONSHIP BETWEEN BACK PAIN AND DISK DEGENERATION?
As we age, virtually everyone will develop degeneration of the spine. This is not the consequence of wear and tear from overuse of the spine, but instead due to the diminished ability of our cells to maintain the spine structures as we age. As with back pain, studies of twins have shown that the age of onset and severity of spine degeneration is strongly predicted by genetics, presumably because we inherit aging genes that alter or destroy the cells that are responsible for maintaining spine structures.
Surprisingly, even though degeneration persists in most people, it is asymptomatic or only results in episodic symptoms that quickly resolve. Research has also shown that the severity of the degeneration only has a small influence on the probability of having an episode of back pain in the adolescent and the middle-aged adult populations, but it has greater influence in the elderly. This suggests that the presence and progression of spine degeneration may be a process relevant to back pain, but that its importance is surpassed by other genetic factors that determine the sensitivity and responsiveness of an individual’s pain system.
When discussing disk degeneration with patients, it is essential to acknowledge three points:
(1) associations between disk degeneration and back pain are weak; (2) spinal pain typically resolves, whereas disk degeneration always persists; and (3) most people with disk degeneration are pain free.
DOES GREATER PHYSICAL ACTIVITY MEAN GREATER RISK FOR SPINAL PAIN?
It is a common belief that back pain results from physical activities that slowly damage or acutely overstress the tissues of the spine. This is referred to as the cumulative injury model of back pain. This premise is strongly challenged by studies exploring physical risk factors for back pain in children, adults and the elderly. Multiple studies have documented that moderate or vigorous physical activity does not increase the risk of back pain, but instead offer modest protection from back pain. Similarly, it has been found that there is no linear relationship between occupational exposure to physical activity and physical load and the risk of back pain.
Contrary to common beliefs, and even when symptoms have a rapid onset, the association of memorable physical triggers or inciting events with new-onset back pain is the exception and not the rule. Research has shown that two thirds of episodes of back pain occur spontaneously, and even when inciting events are identified, they are most often non-traumatic and non-strenuous triggers such as incidental sneezing, bending, twisting, or reaching.
These observations do not suggest that physical exposures are irrelevant to back pain episodes, but instead that back pain can be triggered by a range of stresses on spinal tissues from baseline tissues forces at rest to a range of physical activities, from innocuous to strenuous. These observations also have lead most spine experts to suggest that back pain results from sudden mechanical failure of spine structures that have been slowly weakened by age-related degeneration, and that identifiable triggers associated with pain onset are largely coincidental.
The importance of this cannot be overemphasized, as it infers that back pain episodes are inevitable, and that avoiding recreational or work-related physical activities offers no advantage for back pain prevention. Therefore, healthcare providers should encourage people to resume activities as desired despite the presence of spine degeneration or prior back pain.
BACK PAIN HAS A FAVORABLE NATURAL HISTORY.
In general, the natural history of new-onset spinal pain is favorable. Severe pain rarely lasts for more than a week, and three quarters of episodes completely resolve within 3 months. Pain intensity tends to fluctuate from day to day, and pain flares of brief duration are reported by 90% of patients over the first 6 weeks. For a majority of people, spinal pain is a recurrent problem over decades, with the probability of recurrence of pain increasing with an increasing number of consecutive years with episodes.
The processes responsible for recovery are unknown but likely represent a combination of resolution of local tissue reactions that induced a pain response, along with adaptation or recalibration of the monitoring pain neurons to the degenerative status of the spine tissues.
WHAT ABOUT CHRONIC BACK PAIN?
Unfortunately, one quarter of new spinal pain episodes persist beyond 3 months and may become chronic. Surprisingly, there are no spine-related anatomic, biochemical, and physiologic factors that can help us discern which patients will recover from back pain and which will not. However, even for those with chronic symptoms, intensity trends in a favorable direction over time.
In the absence of identified spine pathology, chronic spinal pain likely represents a primary neurologic process, reflecting changes in pain processing, or persistent sensitization of pain pathways such that innocuous stimuli of the spinal tissues, such as simple movements or certain normal postures can induce pain. Reversal or suppression of these sensitized pain processes are the basis for most conservative treatments of chronic spinal pain.
IS NOT IN PEOPLE’S HEAD, BUT WHAT IS IN THEIR HEAD MAY CONTRIBUTE TO BACK PAIN.
Psychosocial factors can influence the risk for acute and chronic back pain. Low education status, excessive worry, anxiety, depression, high stress, poor self-rated health, frequent use of health or social services and concurrent pain in other areas have been found to increase the risk of chronic back pain. In addition, occupational factors such as job dissatisfaction, low levels of social support in the workplace and lack of control over job tasks are found to be much more important than physical exposure in predicting work related back pain.
It is tempting to over interpret these psychosocial risk factors to suggest that chronic back pain is largely in people’s heads. However, it must be noted that none of these psychosocial factors are powerful predictors of chronic back pain, and that many people without these risk factors have chronic back pain, while many people with psychosocial risk factors do not. The important inference from these studies is that higher brain functions including emotions and cognition influence the susceptibility to and persistence of spinal pain, presumably by accentuating complex neurological processes that affect pain neuron excitability. As such, acknowledging and addressing psychosocial issues are potential paths to mitigate back pain.
Back pain is a common affliction that results from the interaction between degenerative tissue events and the pain system. It is influenced by genetics, tissue degeneration, a person’s lifestyle and psychosocial factors.
Back pain has a spontaneous onset and it doesn’t represent the result of cumulative injuries. In the majority of the population it seems to have a favorable prognosis but it can become chronic in some patients.
Article based on: Rainville, James MD . EVALUATION AND CONSERVATIVE TREATMENT OF BACK AND SPINE PAIN. PART 1 OF COURSE: PRACTICAL ORTHOPEDICS FOR PRIMARY CARE PHYSICIANS.
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