Physiatrists frequently see patients who have chronic pain, and the physiatric approach is highly relevant to pain management. This article is directed toward physiatrists who do not specialize in pain management. It discusses the epidemiology of pain in patient groups often treated by physiatrists, pathophysiologic processes underlying chronic pain, the assessment of chronic pain patients, and selected treatments for chronic pain.
Pain management refers to interventions designed to alleviate patients’ pain directly, rather than treating diseases or injuries believed to be the cause of pain.
Although the field of pain management encompasses acute pain management (eg, treatment of postoperative pain) and management of cancer pain, this article focuses on thmanagement of chronic nonmalignant pain involving the musculoskeletal system.
Basic concepts and definitions
Although pain management may be a definable specialty within medicine, it is fraught with ambiguity. The ambiguity begins when one tries to define chronic pain and distinguish between treating pain as a symptom and treating disorders in which pain is a major symptom.
Because pain is a cardinal symptom of many illnesses and injuries, one might argue that physicians in all areas of medicine treat pain on a regular basis. However, most physicians believe they treat disorders that cause pain rather than treat pain directly. This curative model of pain management embodies the view that physicians should look beyond symptoms to the underlying biologic abnormality believed to be causing the symptoms, and provide treatment that reverses this abnormality. In the best case, symptoms resolve without any additional treatments when the underlying biologic disturbance has been reversed. Common examples include appendectomy for a patient who presents with right lower quadrant pain secondary to appendicitis, and antibiotic therapy for a patient who has a painful septic joint.
The curative model makes key assumptions about the relationship between pain and the underlying pathophysiologic processes believed to be causing the pain. These are that (1) the onset of pain is closely related to the onset of the pathophysiologic process, (2) the physician can identify the pathophysiologic process underlying a patient’s pain, (3) the physician can effectively treat that pathophysiologic process; and (4) resolution of the pathophysiologic process will lead to resolution of the patient’s pain.
The curative model is so ingrained that many physicians have trouble thinking about pain in any other way. In the real world, however, multiple settings exist in which treatment must be directed toward pain itself rather than toward a hypothesized biologic abnormality that is believed to cause the pain. For example, the goal of surgical anesthesia is to prevent patients from experiencing agonizing pain during surgical procedures.
Chronic pain represents another setting in which treating pain directly is often most appropriate rather than looking for upstream pathology to treat. No precise definition of chronic pain exists, and an attempt to create one would probably be counterproductive. One commonly proposed definition is that chronic pain refers to pain that has persisted for a certain duration (eg, 3 or 6 months). A related definition is that chronic pain refers to pain that has persisted beyond the normal healing period for the disorder believed to underlie the pain . These criteria are plausible as operational definitions of chronic pain, but are missing one of key feature. For the most part, patients are not designated as chronic pain patients and referred to pain specialists unless they have not experienced benefit from the treatments that are normally provided for their medical conditions. Thus, in practical terms, chronic pain patients are those who experience persistent pain that has been unresponsive to what seem to be appropriate treatments.
In considering why effective treatment of chronic pain usually involves focusing on the pain itself, one should note that assumptions two and three of the curative model are often not met for patients identified as chronic pain patients. Physicians are often unable to identify what is generating the pain complaints or are not able to treat the diagnosed conditions effectively. Assumption four is challenged by neurophysiologic evidence that even when pain is initiated by a medical condition in a straightforward way, it can gradually become autonomous from the pathophysiologic process, so that therapy that reverses the pathophysiologic process does not resolve the pain (see later discussion). Finally, curative therapies are often irrelevant to individuals designated as chronic pain patients, because these therapies were already administered and were ineffective.
Relevance of pain management to physiatry
Some physiatrists focus their clinical practices on patients who have pain as their major reason for seeking health care, including those who work at pain centers and ones who focus on the management of spinal disorders. Other physiatrists treat patients who are disabled by conditions that are not necessarily painful, such as spinal cord injury and stroke. For these physicians, pain might be construed as a bothersome secondary problem that complicates their attempts to rehabilitate patients. But even these physiatrists must have some facility with this area of medicine, because chronic pain is highly prevalent in most patient groups that will probably be treated by physiatrists.
Other more positive reasons exist why physiatrists should become familiar with chronic pain management. One is that the basic approach in treating chronic pain is very compatible with a rehabilitative focus. Physiatrists primarily focus on helping patients develop skills that permit them to function optimally despite deficits imposed by their disorders. This rehabilitative focus is extremely relevant to chronic pain. Although physicians occasionally encounter chronic pain patients who have been misdiagnosed and are in fact amenable to curative therapy, effective treatment of chronic pain more commonly improves the quality of life of a patient without completely resolving the disorder.
A related point is that exercise therapy plays an important role in the physiatric management of musculoskeletal disorders, and physiatrists have more knowledge of exercise therapy than specialists in most other fields of medicine. The facility most physiatrists have with exercise therapy can be applied in the treatment of chronic pain patients.
Relevance of pain management to physiatry
Some physiatrists focus their clinical practices on patients who have pain as their major reason for seeking health care, including those who work at pain centers and ones who focus on the management of spinal disorders. Other physiatrists treat patients who are disabled by conditions that are not necessarily painful, such as spinal cord injury and stroke. For these physicians, pain might be construed as a bothersome secondary problem that complicates their attempts to rehabilitate patients. But even these physiatrists must have some facility with this area of medicine, because chronic pain is highly prevalent in most patient groups that will probably be treated by physiatrists.
Other more positive reasons exist why physiatrists should become familiar with chronic pain management. One is that the basic approach in treating chronic pain is very compatible with a rehabilitative focus. Physiatrists primarily focus on helping patients develop skills that permit them to function optimally despite deficits imposed by their disorders. This rehabilitative focus is extremely relevant to chronic pain. Although physicians occasionally encounter chronic pain patients who have been misdiagnosed and are in fact amenable to curative therapy, effective treatment of chronic pain more commonly improves the quality of life of a patient without completely resolving the disorder.
A related point is that exercise therapy plays an important role in the physiatric management of musculoskeletal disorders, and physiatrists have more knowledge of exercise therapy than specialists in most other fields of medicine. The facility most physiatrists have with exercise therapy can be applied in the treatment of chronic pain patients.
Basic concepts for the nonspecialist
Physiatrists who specialize in pain medicine often develop skill in procedures such as epidural injections, radiofrequency medial branch neurotomies, and implantation of spinal cord stimulators. However, this article is directed toward the nonspecialist and is designed to describe concepts and skills that almost every physiatrist needs in relation to chronic pain. The focus is on musculoskeletal pain, because pain of musculoskeletal origin is extremely common and frequently treated by physiatrists. Four areas will be discussed: (1) the epidemiology of chronic pain in rehabilitation populations, (2) new concepts regarding the pathophysiology underlying chronic pain, (3) the assessment of chronic pain, and (4) treatment of chronic pain through exercise therapy and medications.
Epidemiology: the burden of chronic pain
Physicians must be aware that chronic pain can have enormous negative effects on the quality of life of patients and their ability to function. Assessing these effects is often difficult, because the burden of illness experienced by individuals who have various medical conditions usually reflects a combination of loss of function caused by the condition and pain when engaging in activities. For example, an individual who has multiple sclerosis may experience weakness, problems with balance, and visual impairment in addition to pain. However, research suggests that even in individuals whose activity limitations reflect a combination of pain and organ dysfunction, the pain may make an important and independent contribution to disability. In particular, Ehde and Jensen reviewed literature on the prevalence and significance of pain among patients typically treated by physiatrists, including those who had spinal cord injury, amputation, cerebral palsy, and multiple sclerosis. Although significant variation was seen across studies, the investigators found maximal reported pain prevalence rates of 94% for spinal cord injury, 74% for amputation, 84% for cerebral palsy, and 82% for multiple sclerosis. A more recent review indicates that patients who have these conditions report significant effects of pain on their overall quality of life and their ability to work and perform activities of daily living (ADLs).
Moreover, research on low back pain dramatically shows the impact of pain on people’s ability to function. Lumbar spine conditions represent a major cause of work disability in most western societies . Although disability in lumbar spine conditions occasionally reflects an unequivocal loss of function (eg, persistent lower-extremity weakness from a lumbar radiculopathy), most individuals who have disabling lumbar spine problems are disabled by the pain associated with physical activity rather than by any demonstrable loss of function of the spine.
As one example of the burden of chronic pain, Robinson and colleagues examined the functional status of injured workers who participated in multidisciplinary pain rehabilitation programs. The cohort consisted of 89 workers who had sustained injuries an average of 7.5 years earlier and had undergone multidisciplinary rehabilitative treatment an average of 4.5 years earlier. On the Physical Component Summary of the SF-12 , these workers had average scores of only 30.3. This was well below the mean score of 38.8 obtained from individuals who had serious medical conditions, including diabetes and congestive heart failure. Of the workers, 63% reported that they were unable to work because of their pain.
In addition to causing individuals to perceive themselves as physically unwell and disabled from work and other activities, pain has very serious implications for the emotional well-being of individuals. For instance, individuals in the study by Robinson and colleagues also received a Mental Component Summary score on the SF-12. Their average score of 43.1 was well below the average of 53.8 for individuals who had no known mental disorder. These results are consistent with abundant data showing a high prevalence of emotional dysfunction among individuals who have chronic pain . Although pain is plausibly construed as a consequence of emotional dysfunction in some people, evidence shows that pain may often cause emotional dysfunction .
Neurophysiologic model
The curative model postulates a simple relationship between end-organ function and pain, and that correcting dysfunction in an organ will resolve pain stemming from the organ. Physicians have been long aware that this model is only approximate, and that psychological factors can influence how patients experience and communicate pain. However, during the past 20 years, research on the neurophysiology of pain has shown that tissue damage and the associated nociception can produce sensitization of the peripheral and central nervous systems, and that this sensitization can subserve a dissociation between tissue injury and pain.
Discussing the vast literature on central and peripheral nervous system sensitization is beyond the scope of this article , but a representative study shows methods that have been used to study central nervous system sensitization (CNSS) and findings from CNSS research that have implications for understanding chronic pain in the clinic. Hoheisel and Mense identified neurons in the dorsal horns of the spinal cords of cats that responded selectively to nociceptive input from isolated regions of the gastrocnemius and semitendinosis muscles. They then injected Bradykinin, a highly irritating chemical, into the two muscles to induce a nociceptive barrage. After this procedure, the dorsal horn neurons being monitored showed an expansion of receptive fields (ie, responded to stimulation from sites that had previously not elicited a response), a reduction in firing threshold (so that they responded to innocuous stimuli that previously had not provoked a response), and spontaneous firing, indicating that CNSS had occurred and persisted after the original nociceptive input was terminated. Other researchers have shown spontaneous firing in dorsal horn neurons after exposure to a nociceptive barrage . Findings of Hoheisel and Mense and numerous other researchers suggest that previously inexplicable chronic pain may be mediated by CNSS.
In animal research, CNSS is operationally defined in terms of changes in the behavior of central nervous system (CNS) neurons, typically measured with microelectrodes inserted into the dorsal horn or other CNS structures. For obvious ethical reasons, these methods cannot be used in humans. However, enough parallels exist between the behavior of animals with known CNSS and that of humans who have chronic pain to convince neuroscientists and pain physicians that patients’ experiences and behavior are mediated by CNSS . For example, the nonanatomic distribution of pain that many chronic pain patients report can be construed as manifestations of expanded receptive fields of sensitized CNS neurons . The hyperalgesia observed when soft tissues of chronic pain patients are palpated can be construed as a manifestation of reduced firing thresholds of sensitized CNS neurons. Their spontaneous pain can be construed as a manifestation of spontaneous firing of sensitized CNS neurons.
CNSS has been proposed as an explanation for a multitude of chronic pain syndromes, including complex regional pain syndrome , chronic headache , fibromyalgia , and chronic spinal pain . Although these proposals have not been proven, the widespread belief among neuroscientists and pain specialists that CNSS is a major factor in chronic pain has implications for all physicians who treat chronic pain; they must be aware that CNSS may have a role in their patients’ complaints. They should also be aware that many of the inferential rules followed by physicians when interpreting pain complaints are based on a simple model of a direct correspondence between symptoms and dysfunction of tissues (eg, nerves, joints, periarticular tissues, muscles) in the region where patients indicate pain, but that the inferential rules are not valid when CNSS has occurred. For example, stocking glove numbness has been long considered a nonphysiologic complaint, but it can logically be interpreted as a result of CNSS .
Several cautions are needed when evaluating the hypothesis that chronic pain in humans frequently reflects CNSS. First, animal research on CNSS has focused primarily on the dorsal horn of the spinal cord; much less is known about changes in the brain in response to nociceptive input. Second, although various indirect methods have been used to identify CNSS in humans experiencing chronic pain , no definitive way exists to determine whether CNSS underlies the pain complaints of individual patients. One practical consequence of this methodologic limitation is that no conclusive information is available about the prevalence of CNSS among chronic pain patients. Some investigators have proposed that widespread hyperalgesia as manifested by tenderness during examination of soft tissues is a valid indicator of CNSS . If this indicator is accepted as valid, one would infer that CNSS is very common among individuals who have chronic pain. Currently, however, thoughtful physicians are often plagued with uncertainty as they attempt to determine whether CNSS is contributing substantially to the pain complaints of an individual patient. Another consequence is that assertions about the role of CNSS in various conditions are difficult to confirm or disconfirm. A skeptic might note that postulated CNSS acts as a “filler” when experts really don’t have a good understanding of the factors underlying pain behavior. Finally, the distinction between pain mediated by CNSS and pain mediated by psychological factors is hazy.
Psychological factors
Psychological factors are widely believed to play a major role in the complaints of a significant proportion of patients who complain of chronic pain. Multiple psychological disorders have been implicated in chronic pain, including anxiety disorders , depressive disorders , personality disorders , and chemical dependency . Also, robust literature demonstrates that dysfunctional psychological processes can contribute to chronic pain, even if they do not constitute a diagnosable psychiatric disorder. In particular, fear of activity or reinjury has been shown to play a role in preventing patients experiencing pain from participating in the active rehabilitation they need to recover from painful conditions .
Despite abundant literature on psychological factors in chronic pain, several key questions have not been fully answered.
What is the scope of psychological factors important in chronic pain?
One problem in addressing this issue is that the boundaries around psychological factors are fuzzy. Axis I disorders, such as generalized anxiety disorder, major depressive disorder, or alcohol abuse, are clearly psychological factors. But psychological factors blend imperceptibly into social factors in one direction, and into neurophysiologic factors in another. As an example of the ambiguity between psychological factors and social ones, research literature clearly indicates that individuals who have workers’ compensation claims respond less well to treatments for pain than individuals who not have these claims . Whether the adverse effect of participation in the workers’ compensation is caused by psychological or sociologic factors is unclear.
The distinction between psychological and neurophysiologic constructs has always been ambiguous, and research on CNSS during the past 25 years has made the distinction even hazier. For example, many phenomena (eg, pain in a stocking glove distribution) that a generation ago were attributed to psychological factors are now attributed (by some) to CNSS. Exploring when processes within the CNS should be described in the language of physiology versus when they should be described as psychological processes is beyond the scope of this article. Unfortunately, this issue has not been given the attention it deserves, largely because the neurophysiologists who study CNSS have little dialogue with the psychologists and psychiatrists who study psychological influences on pain.
Are psychological processes the cause or consequence of chronic pain?
Research supports both hypotheses. For example, evidence exists of an increased risk for chronic pain among individuals who have previously experienced emotional trauma in the form of sexual abuse . At least some prospective studies have also found that psychological dysfunction increases the risk that individuals will subsequently develop pain . However, research demonstrates that when individuals who have been experiencing chronic pain undergo treatment that relieves their pain, they show reductions in emotional dysfunction .
Assessment of chronic pain patients
Although abundant literature exists on the assessment of individuals who have chronic musculoskeletal pain , this does not make the task easy.
It is useful to begin a discussion of pain assessment with the concept of pain behaviors, which are the behaviors individuals show when they are in pain. Pain behaviors include verbal behaviors, such as statements about pain. They also include nonverbal behaviors, such as limping or wincing. These behaviors signal to others that an individual is experiencing pain.
The challenge for an examiner is to interpret the pain behaviors of a patient. Although pain behaviors are sometimes determined entirely by an abnormal biologic process in a patient’s body, they are typically also influenced by the social environment of the patient. Thus, examiners must consider the role of multiple factors that may influence the pain behaviors emitted by patients they evaluate. A useful way to conceptualize this challenge is to think of a regression (prediction) equation with multiple unknowns:
Where PB is the pain behavior that a patient demonstrates, and predictor variables are organized into four categories, so that Xa1, Xa2…Xan1 refer to biomedical factors at the end organ where the patient reports pain; Xb1, Xb2……Xbn2 refer to alterations in nervous system function (especially CNSS) that perpetuate pain after nociceptive impulses from the end organ have diminished or ceased; Xc1, Xc2…….Xcn3 refer to psychological variables; and Xd1, Xd2…Xdn4 refer to systems or contextual variables that influence pain complaints.
The equation emphasizes the multiplicity of factors that influence patients’ expressions of pain, and highlights the dilemma for evaluating physicians in determining the weights that should be assigned to various factors for individual patients. To make matters even worse, no real consensus exists about the possible variables within various categories (eg, those that specify the types of psychological factors that may affect a patient’s pain behavior).
Medical factors
Assessment of patients who have chronic musculoskeletal pain should begin with a conventional medical evaluation to determine the pathophysiologic basis of the symptoms and assess the potential relevance of medical or surgical therapies for treating the underlying pathologic process. This admonition may seem obvious, but sometimes pain specialists fail to heed it and instead launch directly into pain management therapies after performing only a cursory medical evaluation. The reasons for this are probably multiple. One is that many pain patients have undergone multiple evaluations before seeing a pain specialist. When faced with a multitude of imaging studies and consultation reports, pain specialists can easily recoil from the work of reviewing the prior evaluations and instead accept the conclusion that the patient has been thoroughly worked up for a treatable cause of pain. The temptation to jump past careful evaluation and move directly to pain management therapies is especially strong when the pain specialist does not have a great deal of expertise in the organ system putatively causing the pain. However, two reasons exist to avoid this temptation. First, even physicians who specialize in pain medicine and usually see chronic patients will occasionally see patients whose pain has a reasonably well-defined pathologic basis. Second, pain physicians are more likely to be considered credible if they start with a careful medical evaluation.
Altered nervous system functioning
Currently no definitive way exists to identify whether peripheral or central nervous sensitization is influencing a patient’s pain behavior. In this difficult situation, the best a physician can do is assess clinical features that are believed to reflect sensitization. These features include pain in multiple areas (in the absence of injuries to account for them), widespread hyperalgesia during soft tissue palpation, and phenomena associated with neuropathic pain (eg, burning pain provoked by very light sensory stimulation) in the absence of any suspected nerve injury.
Psychological factors
A physiatrist who has no training in psychology or psychiatry cannot be expected to identify quantitatively, or even qualitatively, the psychological issues affecting a patient’s pain behaviors. Diagnosing personality disorders or conditions involving chemical dependency is especially difficult, because patients often hide these problems.
However, even nonspecialists can make preliminary assessments of emotional distress levels, such as by asking patients to rate on a 10-point scale the extent to which they are struggling with anxiety, depression, and irritability. They can also have patients fill out simple self-report measures, such as the Beck Depression Inventory.
A few rules of thumb about psychological influences on pain are often helpful:
- 1.
Psychological factors play some role in the behavior of essentially all patients who have chronic pain. However, this role varies enormously among patients. For practical purposes, ignoring psychological factors and concentrating strictly on medical treatment is reasonable in treating some patients who have chronic pain and disastrous for others.
- 2.
Although research and clinical discussion concentrate on psychological dysfunction as a complicating process in chronic pain, conceptualizing the psychological adaptation to chronic pain as being on a continuum from outstanding to poor is more appropriate. The poor adaptation of some patients interferes with their recovery and complicates treatment planning. Alternatively, some individuals who have chronic pain manage better than expected because of their enormous courage and resourcefulness.
- 3.
If preliminary assessment suggests that a patient’s recovery is likely to be compromised by psychological issues, physiatrists should have a low threshold for referring the patient for psychological evaluation.
Systems/contextual issues
Systems/contextual variables are construed as factors in the social environment that influence people independent of their individual psychological makeups. A good example is the receipt of benefits from a worker’s compensation carrier. Injured workers respond less well to various treatments than individuals who have similar medical conditions who do not have worker’s compensation claims . Although participation in the worker’s compensation system exerts its negative influence through effects on the perceptions, goals, and attitudes of injured workers, the influence seems robust and not dependent on any particular psychological characteristics of the affected workers.
Simple screening questions can address some of the systems/contextual factors that have been studied the most. As part of the evaluation, physiatrists should ask whether a patient has a worker’s compensation claim, is receiving any kind of disability compensation, and is involved in litigation related to the injury. Assessing the cultural and familial factors that can exert more subtle effects on patients is much more difficult. For example, evidence indicates that pain patients generally show more dramatic pain behaviors when in the presence of solicitous spouses , but this effect is likely not obvious when the patient is evaluated alone.
Other issues to assess
Severity of disability
A tendency exists throughout medicine to emphasize diagnosis and deemphasize evaluating how much individuals are incapacitated by their medical conditions. Among chronic pain patients, however, disability assessment is often at least as revealing as diagnostic assessment. One reason is that making a precise diagnosis that accounts even qualitatively for a chronic pain patient’s symptoms is often difficult. A second and more typical reason is that even if a diagnosis can be made, the diagnosed condition is usually compatible with a wide range of functional capabilities. For example, some individuals return to professional sports after decompressive lumbar spine surgery , whereas others remain virtually bedridden. Patients who come to the attention of pain physicians are those who show high levels of disability relative to the diagnosed medical condition.
Construing two different “types” of disability and assessing both is helpful . One type of disability involves limited ability to perform activities of daily living (ADLs). In assessing this type of disability, physiatrists should ask patients whether they must lie down during a typical day, whether they are independent in basic self-care (eg, dressing), and whether they need assistance with household chores. Scales such as the Roland scale are useful in assessing ADL limitations associated with low back pain.
The other type of disability refers to the ability to engage in age-appropriate role behavior, especially work. Physiatrists should ascertain what type of work patients are doing or have done, and whether they have had to leave the workforce because of their condition. If patients had to stop working because of pain, several follow-up questions are appropriate. Specifically, physiatrists should assess the duration of work disability, the financial and personal costs that patients are incurring because of work disability, and whether they are receiving any kind of disability compensation.
Chemical dependency and substance abuse
A substantial percentage of patients who are referred for pain evaluations have either current or past problems with drugs or alcohol. Information in this area is highly relevant for at least two reasons. First, physiatrists will occasionally encounter patients who present as having pain problems that require opioid therapy, when their real problem is opioid addiction. Second, because opioids are often used to treat chronic pain, physicians must know whether a patient has any special risk for inappropriate behavior regarding these medications.
Multidisciplinary evaluations
During the 1950s and 1960s, several centers established multidisciplinary pain programs . One of the primary activities in these early pain centers was the performance of pain evaluations by a multidisciplinary team, often consisting of a psychologist and physicians from different specialties. These evaluations continue to be the norm in multidisciplinary pain centers. In some centers, a typical multidisciplinary evaluating team includes a physician and psychologist. Physical therapists, occupational therapists, and vocational rehabilitation counselors are also often members of the teams. In effect, a multidisciplinary team addresses more or less the same issues as an individual pain physician, but in greater depth.
Related posts:
The Stroke Rehabilitation Paradigm
Traumatic Brain Injury: A Review of Practice Management and Recent Advances
Orthotic and Prosthetic Prescriptions for Today and Tomorrow
Cerebral Palsy
Cancer Rehabilitation: Challenges, Approaches, and New Directions
Rehabilitation Methods for the Burn Injured Individual
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
