CHAPTER 20 LOW BACK PAIN Ronald Kanner, MD, FAAN, FACP 1. What are the most common causes of acute back pain? In most cases of acute back pain, no clear pathophysiologic mechanism is defined, and patients are diagnosed as having “back strain.” Episodes are usually preceded by minor trauma, heavy lifting, or a “near fall.” Direct trauma is rarely a cause. A small minority of patients have acute medical illnesses that cause back pain. The first urgent crossroad in the diagnosis of low back pain is to decide whether the patient has a medically emergent condition (tumor, infection, or trauma) or not. The signs and symptoms that should alert the clinician to impending disaster are focal spine tenderness, fever, weight loss, or bowel or bladder dysfunction. More than 90% of cases of so-called benign acute low back pain resolve spontaneously. 2. Why does the back hurt? Erect posture forces the spine into a position in which it is constantly exposed to minor trauma and to stress on pain-sensitive structures. These pain-sensitive structures are the supporting bones, articulations, meninges, nerves, muscles, and aponeuroses. The vertebral body, despite being short, is actually a long bone with endplates of hard bone and a center of cancellous bone. It is innervated by the dorsal roots. In general, the periosteum, including the periosteum associated with the spine, is markedly pain-sensitive. (This is why, for example, banging the shin is so painful: the periosteum is unprotected.) The articulations (facet joints) are true diarthrodial joints and have a capsule and meniscus. The capsule and bones are richly innervated with nociceptors and are subjected to stress every time the spine turns or bends. 3. Why do some patients with absolutely no evidence of spine injury complain of chronic, disabling back pain? The answer here is the same as the answer in any other significant chronic pain syndrome: the absence of a demonstrable lesion does not confirm the diagnosis of psychogenic pain, and the presence of psychopathology does not mean that the patient is not suffering. Although our intellectual grasp of nociceptive systems is good, these systems are not sufficient to explain all types of pain. Chronic pain must be viewed as a biopsychosocial phenomenon. 4. Some patients who had clearly defined causes for back pain continue to suffer from the same pain, even after the causative agent is eliminated. Why? There is evidence to suggest that chronic, ongoing pain can actually restructure signaling within the central nervous system. There are synaptic changes and there may be neuronal hyperactivity, expression of new genes, and other central phenomena that perpetuate the perception of pain. 5. What characteristics of pain help to define its origin? The type of pain suffered varies with the structure involved. Pain originating in a vertebral body (from osteoporosis, tumor, or infection) tends to be local and aching. It is somatic, nociceptive pain, made worse by standing or sitting and relieved by lying supine. Even though it is usually local, it may refer to other sites. Characteristically, the L1 vertebral body refers pain to the iliac crests and hips. When facet joints are involved, pain is most pronounced when the back is extended. Limitation of active range of motion is a hallmark of facet pain. 6. How do the intervertebral discs (“slipped discs”) contribute to back pain? The intervertebral disc is composed of a firm anulus fibrosus, with a spongier nucleus pulposus inside. The fibrous ring is innervated by nociceptors, but the nucleus pulposus is not. When strong vertical stress is applied to the spine, the nucleus pulposus bulges outward through the anulus fibrosus. Stretching of the fibrous ring is painful; in general, it produces localized low back pain. Once the anulus breaks, disc material may extrude and press against a nerve. Pressure on the nerve root is felt as radicular pain (“sciatica”). Of interest, as the anulus bursts, the intense low back pain tends to subside and is replaced by radicular pain. A bulging disc in itself is usually not painful. Anything that increases pressure on the spine increases pain from a disc. Thus, pain is exacerbated by standing, sitting, and the Valsalva maneuver. 7. What is the usual outcome of a patient with acute low back pain? The vast majority of the general population will have acute back pain at some point in their lives. Over 90% of cases resolve, without specific therapy, in less than 2 weeks. As mentioned earlier, in most cases no specific diagnosis is made. 8. How helpful are radiographs in determining the etiology of acute low back pain? Most patients with acute low back pain require no imaging procedures. It may not be easy to convince a patient who is writhing in pain that no radiographs are needed. However, plain radiographic findings of degenerative disease are as common in asymptomatic patients as in patients with acute back pain. Furthermore, magnetic resonance imaging (MRI) is far too sensitive and nonspecific to be used as a screening procedure. More than one half of adults with no history of back pain may show asymptomatic bulging of discs at one or more lumbar levels, and fully one fourth show disc protrusion. Reserve imaging procedures for patients with acute low back pain when the diagnosis is in question. Specifically, if fever or point tenderness on the spine raises the suspicion of infection or tumor, an imaging procedure is imperative. 9. A patient complaining of left lower back pain stands with his buttocks protruding and with his shoulders tilted to the left. What does this stance indicate? The spine has a number of normal curvatures. With the patient standing erect, the normal position of the spine shows cervical lordosis, thoracic kyphosis, and lumbar lordosis. In low back pain with muscle spasm, the lumbar lordosis may be lost or hyperaccentuated. If the patient tilts toward one side, there may be muscle spasm or foraminal encroachment. With lateral tilt, the ipsilateral intervertebral foramen narrows. Therefore, if there is nerve root compression in the foramen, pain increases. Conversely, when the patient tilts away from an affected side, the foramen on that side opens, lessening neural pain but possibly accentuating pain from muscle spasm. In lateral disc herniations, patients tend to lean away from the side of the herniation. 10. What is the normal range of motion of the spine? The lumbar spine should be able to flex forward 40 to 60 degrees from the vertical. As the patient extends backward, range is somewhat reduced (to about 20 to 35 degrees). Severe pain on extension of the spine may indicate pathology in the articular facets. 11. Describe the significance of the straight-leg raising maneuver Straight-leg raising is used to diagnose nerve root compression from disc disease. It is most commonly used to look for lower lumbar root pathology. The patient lies supine, and the leg is elevated from the ankle, with the knee remaining straight. Normally, patients can elevate the leg 60 to 90 degrees without pain. In disc herniations, elevations of 30 to 40 degrees produce pain. Ipsilateral straight-leg raising is more sensitive, but less specific, than contralateral straight-leg raising. That is, nearly all patients with herniated discs have pain on straight-leg raising on the affected side, but straight-leg raising elicits pain in many other conditions (e.g., severe hip arthritis). However, contralateral straight-leg raising does not produce pain on the affected side unless the pain is due to root disease. Use Patrick’s maneuver to differentiate between hip and lumbar root pathology. The thigh is flexed on the abdomen and the knee is externally rotated, putting stress on the hip joint but not on the nerve root. The patient with hip pathology experiences pain, but the patient with root pathology does not. 12. What is the significance of pain on percussion of the spine? Benign disease (disc protrusion and muscle spasm) rarely, if ever, produces pain on percussion of the spine. This sign usually indicates bone disease, most often metastases or infection; it requires immediate investigation with imaging procedures. 13. What historical data raise suspicion of infection or tumor, rather than benign disease? Most patients with herniated discs or other benign mechanical causes of back pain state that the pain improves with bed rest. When they are no longer weight bearing, pain is relieved. Patients with tumor or infection often say that their worst pain is at night when they are in bed. Nocturnal exacerbation is a clear danger signal. 14. Describe the most common scenario for a herniated intervertebral disc In the most common scenario for a herniated intervertebral disc, patients report severe back pain after lifting something heavy, and a few days later pain radiates down the leg. This sequence of events is due to the pathologic process underlying a herniated disc. With the initial exertion, the nucleus pulposus pushes against the anulus fibrosus, causing it to distend. This distention causes local back pain. As the anulus ruptures, the back pain is relieved, but the nucleus then presses against a nerve root, causing radiated pain down the leg. 15. What is the most common symptom for vertebral metastases? Patients with vertebral metastases almost invariably experience localized back pain. More than 95% of patients with malignant epidural spinal cord compression have pain as their first complaint. Pain is usually described as deep, localized, and aching. As neural structures become involved, the pain radiates in the distribution of the affected nerves. The thoracic spine is the site most commonly affected; thus, pain radiates in a band around the chest. Over time, further neurologic problems ensue. If epidural spinal cord compression progresses, patients have paraparesis, sensory loss, and bowel and bladder involvement. Epidural spinal cord compression from tumor is a medical emergency. Pain usually resolves fairly quickly with the administration of high doses of dexamethasone. Definitive treatment with radiation therapy or surgery is then undertaken. 16. Describe the radiographic appearance of spinal metastases On plain films, one of the earliest signs of spinal metastasis is erosion of a pedicle. Over time, the vertebral body begins to lose height. MRI reveals a change in signal intensity in the vertebral body. As the tumor progresses, it may be seen invading the epidural space and compressing the spinal cord. 17. Both vertebral metastases and vertebral osteomyelitis can cause destruction of vertebral bodies and changes on MRI signal. How can they be differentiated? Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related Related posts: Neuroimaging in the Patient with Pain Tension-Type Headache Sympathetic Neural Blockade Cancer Pain Syndromes Temporary Neural Blockade Physical Modalities: Adjunctive Treatments to Reduce Pain and Maximize Function Stay updated, free articles. Join our Telegram channel Join Tags: Pain Management Secrets Jun 14, 2016 | Posted by admin in PAIN MEDICINE | Comments Off on Low Back Pain Full access? Get Clinical Tree
CHAPTER 20 LOW BACK PAIN Ronald Kanner, MD, FAAN, FACP 1. What are the most common causes of acute back pain? In most cases of acute back pain, no clear pathophysiologic mechanism is defined, and patients are diagnosed as having “back strain.” Episodes are usually preceded by minor trauma, heavy lifting, or a “near fall.” Direct trauma is rarely a cause. A small minority of patients have acute medical illnesses that cause back pain. The first urgent crossroad in the diagnosis of low back pain is to decide whether the patient has a medically emergent condition (tumor, infection, or trauma) or not. The signs and symptoms that should alert the clinician to impending disaster are focal spine tenderness, fever, weight loss, or bowel or bladder dysfunction. More than 90% of cases of so-called benign acute low back pain resolve spontaneously. 2. Why does the back hurt? Erect posture forces the spine into a position in which it is constantly exposed to minor trauma and to stress on pain-sensitive structures. These pain-sensitive structures are the supporting bones, articulations, meninges, nerves, muscles, and aponeuroses. The vertebral body, despite being short, is actually a long bone with endplates of hard bone and a center of cancellous bone. It is innervated by the dorsal roots. In general, the periosteum, including the periosteum associated with the spine, is markedly pain-sensitive. (This is why, for example, banging the shin is so painful: the periosteum is unprotected.) The articulations (facet joints) are true diarthrodial joints and have a capsule and meniscus. The capsule and bones are richly innervated with nociceptors and are subjected to stress every time the spine turns or bends. 3. Why do some patients with absolutely no evidence of spine injury complain of chronic, disabling back pain? The answer here is the same as the answer in any other significant chronic pain syndrome: the absence of a demonstrable lesion does not confirm the diagnosis of psychogenic pain, and the presence of psychopathology does not mean that the patient is not suffering. Although our intellectual grasp of nociceptive systems is good, these systems are not sufficient to explain all types of pain. Chronic pain must be viewed as a biopsychosocial phenomenon. 4. Some patients who had clearly defined causes for back pain continue to suffer from the same pain, even after the causative agent is eliminated. Why? There is evidence to suggest that chronic, ongoing pain can actually restructure signaling within the central nervous system. There are synaptic changes and there may be neuronal hyperactivity, expression of new genes, and other central phenomena that perpetuate the perception of pain. 5. What characteristics of pain help to define its origin? The type of pain suffered varies with the structure involved. Pain originating in a vertebral body (from osteoporosis, tumor, or infection) tends to be local and aching. It is somatic, nociceptive pain, made worse by standing or sitting and relieved by lying supine. Even though it is usually local, it may refer to other sites. Characteristically, the L1 vertebral body refers pain to the iliac crests and hips. When facet joints are involved, pain is most pronounced when the back is extended. Limitation of active range of motion is a hallmark of facet pain. 6. How do the intervertebral discs (“slipped discs”) contribute to back pain? The intervertebral disc is composed of a firm anulus fibrosus, with a spongier nucleus pulposus inside. The fibrous ring is innervated by nociceptors, but the nucleus pulposus is not. When strong vertical stress is applied to the spine, the nucleus pulposus bulges outward through the anulus fibrosus. Stretching of the fibrous ring is painful; in general, it produces localized low back pain. Once the anulus breaks, disc material may extrude and press against a nerve. Pressure on the nerve root is felt as radicular pain (“sciatica”). Of interest, as the anulus bursts, the intense low back pain tends to subside and is replaced by radicular pain. A bulging disc in itself is usually not painful. Anything that increases pressure on the spine increases pain from a disc. Thus, pain is exacerbated by standing, sitting, and the Valsalva maneuver. 7. What is the usual outcome of a patient with acute low back pain? The vast majority of the general population will have acute back pain at some point in their lives. Over 90% of cases resolve, without specific therapy, in less than 2 weeks. As mentioned earlier, in most cases no specific diagnosis is made. 8. How helpful are radiographs in determining the etiology of acute low back pain? Most patients with acute low back pain require no imaging procedures. It may not be easy to convince a patient who is writhing in pain that no radiographs are needed. However, plain radiographic findings of degenerative disease are as common in asymptomatic patients as in patients with acute back pain. Furthermore, magnetic resonance imaging (MRI) is far too sensitive and nonspecific to be used as a screening procedure. More than one half of adults with no history of back pain may show asymptomatic bulging of discs at one or more lumbar levels, and fully one fourth show disc protrusion. Reserve imaging procedures for patients with acute low back pain when the diagnosis is in question. Specifically, if fever or point tenderness on the spine raises the suspicion of infection or tumor, an imaging procedure is imperative. 9. A patient complaining of left lower back pain stands with his buttocks protruding and with his shoulders tilted to the left. What does this stance indicate? The spine has a number of normal curvatures. With the patient standing erect, the normal position of the spine shows cervical lordosis, thoracic kyphosis, and lumbar lordosis. In low back pain with muscle spasm, the lumbar lordosis may be lost or hyperaccentuated. If the patient tilts toward one side, there may be muscle spasm or foraminal encroachment. With lateral tilt, the ipsilateral intervertebral foramen narrows. Therefore, if there is nerve root compression in the foramen, pain increases. Conversely, when the patient tilts away from an affected side, the foramen on that side opens, lessening neural pain but possibly accentuating pain from muscle spasm. In lateral disc herniations, patients tend to lean away from the side of the herniation. 10. What is the normal range of motion of the spine? The lumbar spine should be able to flex forward 40 to 60 degrees from the vertical. As the patient extends backward, range is somewhat reduced (to about 20 to 35 degrees). Severe pain on extension of the spine may indicate pathology in the articular facets. 11. Describe the significance of the straight-leg raising maneuver Straight-leg raising is used to diagnose nerve root compression from disc disease. It is most commonly used to look for lower lumbar root pathology. The patient lies supine, and the leg is elevated from the ankle, with the knee remaining straight. Normally, patients can elevate the leg 60 to 90 degrees without pain. In disc herniations, elevations of 30 to 40 degrees produce pain. Ipsilateral straight-leg raising is more sensitive, but less specific, than contralateral straight-leg raising. That is, nearly all patients with herniated discs have pain on straight-leg raising on the affected side, but straight-leg raising elicits pain in many other conditions (e.g., severe hip arthritis). However, contralateral straight-leg raising does not produce pain on the affected side unless the pain is due to root disease. Use Patrick’s maneuver to differentiate between hip and lumbar root pathology. The thigh is flexed on the abdomen and the knee is externally rotated, putting stress on the hip joint but not on the nerve root. The patient with hip pathology experiences pain, but the patient with root pathology does not. 12. What is the significance of pain on percussion of the spine? Benign disease (disc protrusion and muscle spasm) rarely, if ever, produces pain on percussion of the spine. This sign usually indicates bone disease, most often metastases or infection; it requires immediate investigation with imaging procedures. 13. What historical data raise suspicion of infection or tumor, rather than benign disease? Most patients with herniated discs or other benign mechanical causes of back pain state that the pain improves with bed rest. When they are no longer weight bearing, pain is relieved. Patients with tumor or infection often say that their worst pain is at night when they are in bed. Nocturnal exacerbation is a clear danger signal. 14. Describe the most common scenario for a herniated intervertebral disc In the most common scenario for a herniated intervertebral disc, patients report severe back pain after lifting something heavy, and a few days later pain radiates down the leg. This sequence of events is due to the pathologic process underlying a herniated disc. With the initial exertion, the nucleus pulposus pushes against the anulus fibrosus, causing it to distend. This distention causes local back pain. As the anulus ruptures, the back pain is relieved, but the nucleus then presses against a nerve root, causing radiated pain down the leg. 15. What is the most common symptom for vertebral metastases? Patients with vertebral metastases almost invariably experience localized back pain. More than 95% of patients with malignant epidural spinal cord compression have pain as their first complaint. Pain is usually described as deep, localized, and aching. As neural structures become involved, the pain radiates in the distribution of the affected nerves. The thoracic spine is the site most commonly affected; thus, pain radiates in a band around the chest. Over time, further neurologic problems ensue. If epidural spinal cord compression progresses, patients have paraparesis, sensory loss, and bowel and bladder involvement. Epidural spinal cord compression from tumor is a medical emergency. Pain usually resolves fairly quickly with the administration of high doses of dexamethasone. Definitive treatment with radiation therapy or surgery is then undertaken. 16. Describe the radiographic appearance of spinal metastases On plain films, one of the earliest signs of spinal metastasis is erosion of a pedicle. Over time, the vertebral body begins to lose height. MRI reveals a change in signal intensity in the vertebral body. As the tumor progresses, it may be seen invading the epidural space and compressing the spinal cord. 17. Both vertebral metastases and vertebral osteomyelitis can cause destruction of vertebral bodies and changes on MRI signal. How can they be differentiated? Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related Related posts: Neuroimaging in the Patient with Pain Tension-Type Headache Sympathetic Neural Blockade Cancer Pain Syndromes Temporary Neural Blockade Physical Modalities: Adjunctive Treatments to Reduce Pain and Maximize Function Stay updated, free articles. Join our Telegram channel Join Tags: Pain Management Secrets Jun 14, 2016 | Posted by admin in PAIN MEDICINE | Comments Off on Low Back Pain Full access? Get Clinical Tree
