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CHAPTER 33 LOW BACK PAIN Karen P. Barr, Leah G. Concannon, Mark A. Harrast Low back pain has become a costly burden to society and Public Health Perspective a leading cause of disability and...

CHAPTER 33 LOW BACK PAIN Karen P. Barr, Leah G. Concannon, Mark A. Harrast Low back pain has become a costly burden to society and Public Health Perspective a leading cause of disability and loss of productivity. This chapter outlines the anatomy and biomechanics of the Programs to decrease the incidence of back pain have been lumbar spine and our current understanding of the physi- developed. Only exercise has been shown to be an effective ology of low back pain. The clinical evaluation and treat- intervention to prevent back pain. Interventions such as ment of various etiologies of low back pain and leg pain ergonomics, education, reduced lifting, and back supports caused by lumbar spine disease is also reviewed. have not shown to be effective.23 Other public health inter- ventions have focused on minimizing the chronicity and effects of low back pain. Public health campaigns through- Epidemiology out Europe, Canada, and Australia have attempted to use the media to elicit changes in beliefs and treatment seeking. Low back pain is a symptom, not a disease, and has many This has been most effective in Australia, where it was causes. It is generally described as pain between the costal shown to decrease disability behavior and work absences.39 margin and the gluteal folds. It is extremely common. Many countries have developed evidence-based guide- Approximately 40% of people say they have had low back lines to help practitioners manage this condition. Goals pain within the past 6 months,237 and annually 15% often include minimizing inappropriate interventions to report low back pain lasting longer than 2 weeks.58 Studies decrease comorbidity associated with unnecessary treat- have shown a lifetime prevalence as high as 84%.244 Onset ments and control health care costs. The use of new and usually begins in the teens to early 40s. Most patients expensive technology to diagnose and treat back pain has have short attacks of pain that are mild or moderate and not led to improved outcomes, but has caused greatly esca- do not limit activities, but these tend to recur over many lating costs and socioeconomic problems. The rate of years. Most episodes resolve with or without treatment expensive treatments such as injections and surgeries vary and the great majority of people who have back pain do greatly by country and even regions within countries, not seek medical care.255 Approximately 10% to 15% of without an associated improvement in outcomes in these back pain becomes chronic and, for some of this group, regions. The trend of both increased cost of care and it can cause substantial disability. In most studies, approxi- increasing comorbidities from these complex interventions mately half of the sick days used for back pain are continues, as does the trend of increasing disability from accounted for by the 15% of people who are home from back pain.16 work for more than 1 month. Between 80% and 90% of the health care and social costs of back pain are for the 10% who develop chronic low back pain and disability. Anatomy and Biomechanics of Just over 1% of adults in the United States are perma- the Lumbar Spine nently disabled by back pain, and another 1% are tem- porarily disabled.160 General Concepts Researchers have sought to determine what factors lead back pain to become chronic and disabling. Interestingly, The lumbar spine has a dichotomous role in terms of func- unlike many other medical conditions, it does not appear tion, which is strength coupled with flexibility. The spine to be related to the diagnosis or the cause of the back pain. performs a major role in support and protection (strength) Instead, the largest baseline predictors of persistent dis- of the spinal canal contents (spinal cord, conus, and cauda abling back pain are maladaptive pain coping behaviors, equina) but also gives us inherent flexibility, allowing us the presence of nonorganic signs, presence of psychiatric to place our limbs in appropriate positions for everyday disease, low physical function, and low general health.51 functions. The percentage of patients disabled by back pain, as well The strength of the spine results from the size and as the cost of low back pain, has steadily increased during arrangements of the bones, as well as from the arrange- the past few decades. This appears to be more from social ment of the ligaments and muscles. The inherent flexibility causes than from a change in the conditions that cause low results from the large number of joints placed so closely back pain. The two most commonly cited factors are the together in series. Each vertebral segment can be thought increasing societal acceptance of back pain as a reason to of as a three-joint complex: one intervertebral disk with become disabled, and changes in the social system that pay vertebral end plates and two zygapophyseal joints. The disability benefits to patients with back pain.242 typical lordotic framework of the lumbar spine assists with 711 712 SECTION 4 Issues in Specific Diagnoses Pedicle Superior articular facet Vertebral body 2 Transverse 1 process 3 Spinous process Inferior Lamina Inferior articular vertebral facet notch FIGURE 33-2 An oblique dorsal view of an L5 vertebra, showing the parts of the vertebral arch: 1, pars interarticularis (crosshatched area); 2, pars lami- FIGURE 33-1 Lateral view of the lumbar vertebrae. (Modified from Parke naris; and 3, pars pedicularis. The dotted line indicates the most frequent site WW: Applied anatomy of the spine. In Herkowitz HN, Garfin SR, Balderson RA, of mechanical failure of the pars interarticularis. (Modified from Parke WW: et al, editors: Rothman-Simeone: the spine, ed 4, Philadelphia, 1999, WB Applied anatomy of the spine. In Herkowitz HN, Garfin SR, Balderson RA, et al, Saunders.) editors: Rothman-Simeone: the spine, ed 4, Philadelphia, 1999, WB Saunders.) this flexibility but also increases the ability of the lumbar is one reason we are slightly shorter in our older adult spine to absorb shock. years. The annulus fibrosus consists of concentric layers of fibers at oblique angles to each other, which help to with- Vertebrae stand strains in any direction. The outer fibers of the The bony anatomy of the lumbar spine consists of five annulus have more collagen and less proteoglycans and lumbar vertebrae. A small percentage of the population water than the inner fibers.22 This varying composition has four (the fifth vertebra is sacralized) or six (the first supports the functional role of the outer fibers to resist sacral segment is lumbarized). The lumbar vertebrae are flexion, extension, rotation, and distraction forces. composed of the vertebral body, the neural arch, and the The main function of the intervertebral disk is shock posterior elements (Figure 33-1). The vertebral bodies absorption (Figure 33-3). It is primarily the annulus, not increase in size as you travel caudally in the spine. The the nucleus, that acts as the shock absorber because the lower three are typically more wedge-shaped (taller anteri- liquid properties of the nucleus render it incompressible. orly), which helps create the normal lumbar lordosis. The When an axial load occurs, the increase in force in the structure of the vertebral bodies and the shock-absorbing incompressible nucleus pushes on the annulus and intervertebral disks function together to withstand axially stretches its fibers. If the fibers break, then a herniated directed loads. The sides of the bony neural arch are the nucleus pulposus results. pedicles, which are thick pillars that connect the posterior Because flexion loads the anterior disk, the nucleus is elements to the vertebral bodies. They are designed to displaced posteriorly.121 If the forces are great enough, the resist bending and to transmit forces between the vertebral nucleus can herniate through the posterior annular fibers. bodies and the posterior elements. The posterior elements The lateral fibers of the posterior longitudinal ligaments consist of the laminae, the articular processes, and the are thinnest, however, making posterolateral disk hernia- spinous processes. The superior and inferior articular pro- tions the most common (Figure 33-4). The posterolateral cesses of adjacent vertebrae create the zygapophyseal portion of the disk is most at risk when there is forward joints. The pars interarticularis is the part of the lamina flexion accompanied by lateral bending (i.e., bending and between the superior and inferior articular processes twisting). The zygapophyseal joints cannot resist rotation (Figure 33-2). The pars is the site of stress fractures (spon- when the spine is in flexion, thereby increasing torsional dylolysis) because it is subjected to large bending forces. shear forces and putting the disks at risk. This occurs as the forces transmitted by the vertically ori- The activity of the lumbar muscles correlates well with ented lamina undergo a change in direction into the hori- intradiskal pressures (i.e., when back muscles contract, zontally oriented pedicle.27 there is an associated increase in disk pressure). These pressures change depending on spine posture and the activity undertaken. Figure 33-5 demonstrates the changes Intervertebral Disk in L3 disk pressure under various positions and exer- The intervertebral disk and its attachment to the verte- cises.158,159 Adding rotation to the already flexed posture bral end plate are considered a secondary cartilaginous increases the disk pressure substantially. Comparing lifting joint, or symphysis. The disk consists of the internal maneuvers, it has been shown that there is not a substan- nucleus pulposus and the outer annulus fibrosus. The tial difference in disk pressure when lifting with the legs nucleus pulposus is the gelatinous inner section of the (i.e., with the back straight and knees bent) versus lifting disk. It consists of water, proteoglycans, and collagen. The with the back (i.e., with a forward-flexed back and straight nucleus pulposus is 90% water at birth. Disks desiccate and legs).8,9 What decreases the forces on the lumbar spine is degenerate as we age and lose some of their height, which lifting the load close to your body. The farther the load  CHAPTER 33 Low Back Pain 713 C C AC A FIGURE 33-4 A posterior view of the L3-L4 zygapophyseal joints. On the left, the capsule of the joint (C) is intact. On the right, the posterior capsule has been resected to reveal the joint cavity, the articular cartilages (AC), and B the line of attachment of the joint capsule (dashed line).The upper joint capsule (C) attaches further from the articular margin than the posterior capsule does. (Modified from Bogduk N, editor:The zygapophysial joints. In Clinical and radiologi- cal anatomy of the lumbar spine and sacrum, ed 5, Edinburgh, 2012, Churchill Livingstone.) Nerve root Cauda compression equina C in the lateral recess Posterolateral Defect herniated in annulus nucleus fibrosus pulposus D Nucleus Annulus pulposus fibrosus FIGURE 33-3 The mechanism of weight transmission in an intervertebral disk. A, Compression increases the pressure in the nucleus pulposus. This is FIGURE 33-5 Posterolateral intervertebral disk herniation. exerted radially onto the annulus fibrosus, and the tension in the annulus increases. B, The tension in the annulus is exerted on the nucleus, preventing it from expanding radially. Nuclear pressure is then exerted on the vertebral end plates. C, Weight is borne, in part, by the annulus fibrosus and by the Ligaments nucleus pulposus. D, The radial pressure in the nucleus braces the annulus, and the pressure on the end plates transmits the load from one vertebra to the The two main sets of ligaments of the lumbar spine are the next. (Modified from Bogduk N, editor: The inter-body joint and the interverte- longitudinal ligaments and the segmental ligaments. The bral discs. In Clinical and radiological anatomy of the lumbar spine and sacrum, ed two longitudinal ligaments are the anterior and posterior 5, Edinburgh, 2012, Churchill Livingstone.) longitudinal ligaments. They are named according to their position on the vertebral body. The anterior longitudinal is from the chest, the greater the stress on the lumbar ligament acts to resist extension, translation, and rotation. spine.8 The posterior longitudinal ligament acts to resist flexion. Disruption of either ligament primarily occurs with rota- tion rather than with flexion or extension. The anterior Zygapophyseal Joints longitudinal ligament is twice as strong as the posterior The zygapophyseal joints (also known as Z joints and facet longitudinal ligament. joints) are paired synovial joints with a synovium and a The main segmental ligament is the ligamentum flavum, capsule (Figure 33-6). Their alignment or direction of joint which is a paired structure joining adjacent laminae. It is articulation determines the direction of motion of the the ligament that is pierced when performing lumbar adjacent vertebrae. The lumbar zygapophyseal joints lie in punctures. It is a very strong ligament but is elastic enough the sagittal plane and thus primarily allow flexion and to allow flexion. Flexing the lumbar spine puts this liga- extension. Some lateral bending and very little rotation are ment on stretch, decreasing its redundancy and making it allowed, which limits torsional stress on the lumbar disks. easier to pierce during a lumbar puncture. Rotation is more a component of thoracic spine motion. The other segmental ligaments are the supraspinous, The majority of spinal flexion and extension (90%) occurs interspinous, and intertransverse. The supraspinous liga- at the L4-L5 and L5-S1 levels, which contributes to the high ments are the strong ligaments that join the tips of adjacent incidence of disk problems at these levels. spinous processes and act to resist flexion. These ligaments, 714 SECTION 4 Issues in Specific Diagnoses Semispinalis capitis Semispinalis cervicis Iliocostalis thoracis Longissimus thoracis Spinalis thoracis Iliocostalis thoracis Spinalis thoracis Longissimus lumborum Iliocostalis lumborum Multifidus FIGURE 33-6 The intermediate layer of back muscles: the erector spinae. FIGURE 33-7 The deep back muscles: the multifidi. along with the ligamentum flavum and the facet joints, act Abdominal Musculature to restrain the spine and prevent excessive shear forces in forward bending.28 The superficial abdominals include the rectus abdominis and external obliques (Figure 33-9, A). The deep layer Muscles consists of internal obliques and the transversus abdomi- nis (see Figure 33-9, B). The transversus abdominis has Muscles with Origins on the Lumbar Spine been the focus of considerable attention recently as an These muscles can be divided anatomically into posterior important muscle to train in treating low back pain. Its and anterior muscles. The posterior muscles include the connection to the thoracolumbar fascia (and consequently latissimus dorsi and the paraspinals. The lumbar para- its ability to act on the lumbar spine) has probably been spinals consist of the erector spinae (iliocostalis, longissi- the major reason that it has received such attention of late. mus, and spinalis), which act as the chief extensors of the Thoracolumbar Fascia spine, and the deep layer (rotators and multifidi) (Figures 33-7 and 33-8). The multifidi are tiny segmental stabilizers The thoracolumbar fascia, with its attachments to the that act to control lumbar flexion because they cannot transversus abdominis and internal obliques, acts as an produce enough force to truly extend the spine. Their most abdominal and lumbar “brace,” particularly when lifting. important function has been hypothesized to be that of a This abdominal bracing mechanism results from contrac- sensory organ to provide proprioception for the spine, tion of these deep abdominal muscles, which creates given the predominance of muscle spindles seen histologi- tension in the thoracolumbar fascia, which then creates an cally in these muscles. extension force on the lumbar spine without increasing The anterior muscles of the lumbar spine include the shear forces.86 The validity of this model has recently been psoas and quadratus lumborum. Because of the direct called into question, however.28 attachment of the psoas on the lumbar spine, tightening Pelvic Stabilizers this muscle accentuates the normal lumbar lordosis. This can increase forces on the posterior elements and can The pelvic stabilizers are considered “core” muscles because contribute to zygapophyseal joint pain. The quadratus of their indirect effect on the lumbar spine, even though lumborum acts in side bending and can assist in lumbar they do not have a direct attachment to the spine. The flexion. gluteus medius stabilizes the pelvis during gait. Weakness  CHAPTER 33 Low Back Pain 715 Serratus Pectoralis anterior major Anterior Rectus layer of abdominis rectus Serratus 5th costal sheath Posterior anterior cartilage layer of rectus Anterior layer External sheath Anterior layer of oblique of rectus sheath rectus sheath (cut edges) Transversus Rectus abdominis External abdominis Internal oblique External oblique Internal oblique oblique Anterior Anterior superior superior Rectus A iliac spine B iliac spine abdominis FIGURE 33-8 A, The superficial abdominal muscles. B, The deep abdominal muscles. % % A 25 75 100 150 220 140 185 275 B 150 180 210 100 140 130 35 FIGURE 33-9 A, Relative change in pressure (or load) in the third lumbar disk in various positions in living individuals. B, Relative change in pressure (or load) in the third lumbar disk during various muscle-strengthening exercises in living individuals. Neutral erect posture is considered 100% in these figures; other posi- tions and activities are calculated in relationship to this. (Modified from Nachemson AL, Morris JM: In vivo measurements of intradiscal pressure, J Bone Joint Surg Am 46:1077-1092, 1964.) or inhibition of this muscle results in pelvic “instability,” muscles, and the zygapophyseal joints, and provides sensa- which introduces lumbar side bending and rotation, creat- tion to the back. The medial branch innervates the zyg- ing increased shear or torsional forces on the lumbar disks. apophyseal joints and lumbar multifidi, and is the target The piriformis is a hip and sacral rotator and can cause during radiofrequency neurotomy for presumed zyg- excessive external rotation of the hip and sacrum when it apophyseal joint pain (Figure 33-11).29 is tight. This can result in increased shear forces at the lumbosacral junction. Other pelvic floor muscles may also act to maintain proper positioning of the spine and are an Pain Generators of the Lumbar important focus of some spine rehabilitation programs. Spine The low back is an anatomically diverse set of structures, Nerves and there are many potential sources of pain. One useful The conus medullaris ends at about L2, and below this strategy to clarify these potential sources of pain is learning level is the cauda equina. The cauda equina consists of the what low back structures are innervated (and can transmit dorsal and ventral rootlets, which join together in the pain through neural pain fibers) and what structures have intervertebral neuroforamen to become the spinal nerves no innervation (Box 33-1). (Figure 33-10). The spinal nerve gives off the ventral The sinuvertebral nerve innervates the anterior vertebral primary ramus. The ventral primary rami from multiple body, the external annulus, and the posterior longitudinal levels form the lumbar and lumbosacral plexus to inner- ligament. The posterior longitudinal ligament is a highly vate the limbs. The dorsal primary ramus, with its three innervated structure and can play an important role in low branches (medial, intermediate, and lateral), innervates back pain perception with lumbar disk herniations. The the posterior half of the vertebral body, the paraspinal medial branch of the dorsal primary ramus innervates the 716 SECTION 4 Issues in Specific Diagnoses Dura zygapophyseal joints and interspinous ligaments, as well as the lumbar multifidi. The other small branches of the Arachnoid dorsal primary ramus innervate the posterior vertebral body and other lumbar paraspinal musculature and fascia. The anterior longitudinal ligament is innervated by the Subarachnoid Dural sleeve gray rami communicans, which branch off the lumbar space sympathetic chain. The internal annulus fibrosus and nucleus pulposus do not have innervation and therefore, Pia in nondisease states, cannot transmit pain. Spinal nerve Dorsal root Aging Spine: A Degenerative Cascade Ventral ramus Kirkaldy-Willis et al.118 have supplied us with the most Ventral root accepted theory describing the cascade of events in degen- erative lumbar spine disease that results in disk hernia- Dorsal root tions, spondylotic changes, and eventually multilevel ganglion Dorsal ramus spinal stenosis. At the heart of this theory is the fact that, FIGURE 33-10 A lumbar spinal nerve, its roots, and meningeal coverings. although the posterior zygapophyseal joints and the ante- The nerve roots are invested by pia mater, and covered by arachnoid and dura rior intervertebral disks are separated anatomically, forces as far as the spinal nerve. The dura of the dural sac is prolonged around the and lesions affecting one certainly alter and affect the roots as their dural sleeve, which blends with the epineurium of the spinal other. For example, axial compressing injuries can damage nerve. (Modified from Bogduk N: Nerves of the lumbar spine. In Bogduk N, editor: Clinical and radiological anatomy of the lumbar spine and sacrum, ed 5, the vertebral end plates, which can lead to degenerative Edinburgh, 2012, Churchill Livingstone.) disk disease, which eventually stresses the zygapophyseal joints, leading to the common degenerative changes seen Transverse Superior over time. Torsional stress can injure the zygapophyseal process articular joints and the disks, which in turn leads to increased stress facet on both these elements. It appears that commonly these changes begin first in the disks. By studying multiple mag- Spinal netic resonance images (MRIs) of aging spines, evidence of nerve Medial disk degeneration is seen first, and can precede zygapophy- branch seal joint disease by as much as 20 years.76 When these degenerative changes affect one level, a chain reaction Ventral Zygapo- occurs, placing stress on the levels above and below the primary physeal currently affected level, and eventually resulting in more ramus joint generalized multilevel spondylotic changes. To simplify discussion of the degenerative cascade, we will separate our discussion of the changes that occur in Dorsal Inferior primary articular the zygapophyseal joints from those in the disk, fully real- ramus facet izing that they both can occur simultaneously and affect each other (Figure 33-12). FIGURE 33-11 Observe that the innervation of the zygapophyseal joints derives from the medial branch off the dorsal primary ramus. Tears in the annulus are thought to be the first anatomic sign of degenerative wear. When the annulus is weakened enough, typically posterolaterally, the internal nucleus BOX 33-1 pulposus can herniate. Internal disk disruption can occur Potential Pain Generators of the Back without herniation, however, because age and repeated stresses acting on the spine cause the gelatinous nucleus to A useful classification system to understand the potential become more fibrous over time. Tears in the annulus can sources of low back pain depends on knowing what progress to tears in the fibrous disk material, resulting in structures are innervated (and can transmit pain) and what structures have no innervation. “internal disk disruption” without frank herniation. All this results in a loss of disk height, which causes instability Innervated Structures (because the end-plate connection to the disk is degener- Bone: Vertebrae ated), as well as lateral recess and foraminal narrowing and Joints: Zygapophyseal potential nerve root impingement. The loss of disk height Disk: Only the external annulus and potentially diseased disk also places new stresses on the posterior elements, result- Ligaments: Anterior longitudinal ligament, posterior ing in further instability of the zygapophyseal joints and longitudinal ligament, interspinous further degeneration and nerve root impingement. Muscles and fascia The degenerative changes that occur in the zygapophy- Nerve root seal joints from aging and repetitive microtrauma are Noninnervated Structures similar to those that occur in the appendicular skeletal Ligamentum flavum joints. The process begins with synovial hypertrophy, Disk: Internal annulus, nucleus pulposus which eventually results in cartilage degeneration and destruction. With the resultant capsular laxity, the joint can  CHAPTER 33 Low Back Pain 717 Posterior Three joint Intervertebral anatomy. Muscles also provide a crucial component of joints complex disk spinal stability, and is one area of potential intervention through exercise. In normal situations, only a small amount of muscular coactivation (approximately 10% of maximal Synovial Circumferential contraction) is needed to provide segmental stability. In a reaction tears segment damaged by ligamentous laxity or disk disease, slightly more muscle coactivation might be needed. Because of the relatively gentle forces required to perform Cartilage Radial the activities of daily living, muscular endurance is more Herniation important than absolute muscle strength for most patients. destruction tears Some strength reserve, however, is needed for unpredict- able activities such as a fall, a sudden load to the spine, or quick movements. In sports and heavy physical work, both Osteophyte Internal strength and endurance needs increase. This biomechani- formation disruption cal model is particularly complex in the spine because of the presence of global movement patterns and segmental movement patterns. Two interrelated muscular tasks must Capsular Loss disk laxity Instability height be carried out at the same time: maintaining overall posture and position of the spine, and control of individual inter- segmental relationships. Sufficient but not excessive joint stiffness is required at the segmental level to prevent injury Subluxation Lateral nerve Disk and allow for efficient movement. This stiffness is achieved entrapment resorption with specific patterns of muscle activity, which differ depending on the position of the joint and the load on the spine. The inability to achieve this stiffness, and the result- Enlargement One-level Osteophytes ing segmental problems, is thought to be a factor in low articular process central at back of back pain.185 Alternatively, some segments are thought to (and laminae) stenosis vertebral be too stiff, because of osteoarthritis and ligamentous bodies thickening in the spine, which is also considered to be a source of low back pain. Effect of recurrent strains Although this theory offers an explanation as to how at levels above and below the original lesion the spine ages, it is still unclear why there is such a marked disconnect between the occurrence of back pain and the anatomic changes in the spine associated with aging. Many patients with normal spine anatomy suffer from back pain, Multilevel degenerative lesions occasionally disabling pain, and many patients with marked degenerative changes on imaging are nearly or fully pain-free. One theory is that this is related to differ- Multilevel spinal stenosis ences in muscular activation and neural control. There appear to be consistent muscular problems in FIGURE 33-12 The spectrum of degenerative change that leads from minor strains to marked spondylosis and stenosis. (Modified from Kirkaldy-Willis WH, patients with chronic low back pain. Some of these factors Wedge JH, Yong-Hing K, et al: Pathology and pathogenesis of lumbar spondylosis might exist preinjury and make the spine more susceptible and stenosis, Spine 3:319-328, 1998, with permission of Lippincott Williams & to injury, and some are adaptations to pain. Motor systems Wilkins.) and their adaption to back pain appear to vary greatly between individuals and range from subtle changes in muscle activation to redistribute forces, to complete avoid- become unstable, and with the subsequent repetitive ance of activity. Studies have shown abnormal firing pat- abnormal joint motion, bony hypertrophy results, thus terns in the deep stabilizers of the spine and transversus narrowing the central canal and lateral recesses and poten- abdominis with activities such as limb movements, accept- tially impinging nerve roots. ing a heavy load, and responding to balance challenges. These changes are commonly described clinically as seg- Other researchers have found strength ratio abnormalities mental dysfunction. Segmental dysfunction can occur and endurance deficits in patients with low back pain, such when either a segment is too stiff or too mobile. A segment as abnormal flexion to extension strength ratios and lack encompasses the disk, the vertebrae on each side of the of endurance of torso muscles.148 These motor adaptations disk, and the muscles and ligaments that act across this may have persistent long-term consequences.102 area. Excessive mobility, also called instability, or poten- Studies of lumbar paraspinals have found several abnor- tially better termed “functional instability,” can be the malities in patients with low back pain. Multiple imaging result of tissue damage, poor muscular endurance, or poor studies have demonstrated paraspinal muscle atrophy, par- muscular control, and is usually a combination of all three. ticularly of the multifidi, in patients with chronic low back Structural changes from tissue damage, such as joint laxity, pain.185 Recovery of the multifidi does not appear to occur vertebral end-plate fractures, and loss of disk height, can spontaneously with the resolution of back pain.101 Biopsies lead to segmental dysfunction because of the altered of multifidi in patients with low back pain also show 718 SECTION 4 Issues in Specific Diagnoses abnormalities. Multifidi biopsies collected at the time of fear reactivity.37 Patients with posttraumatic stress disorder surgery for disk herniation showed type 2 muscle atrophy also have a high incidence of chronic low back pain.204 and type 1 fiber structural changes. On repeat biopsy Patient Beliefs About Pain and Pain Cognition repeated 5 years postoperatively, type 2 fiber atrophy was still found in all patients, in both those who had improved Beliefs about back pain can be highly individual and are with surgery and those who had not. In the positive often not based on facts. Some patients with back pain, outcome group, however, the percentage of type 1 fibers especially those with chronic low back pain that keeps with abnormal structures had decreased, and in the nega- them from working, have a great deal of fear about back tive outcome group there was a marked increase in abnor- pain. These include fears that their pain will be permanent, mal type 1 fibers.183 that it is related to activity, and that exercise will damage their back. This set of beliefs is referred to as fear avoidance. For example, studies have found that patients with chronic Centralization and Pain low back pain who perform poorly on treadmill exercise The experience of nociception is processed by the body in tests,196 walk slower on treadmill tests,2 and perform more complex ways. The theory that pain is a simple loop from poorly on spinal isometric exercise testing,3 were the ones injury to perception of injury is much too simplistic. Pain with more anticipation of pain than those who did well processing begins in the spinal cord and continues exten- on these tests. Fear-avoidance beliefs rather than actual sively in the brain, and the ultimate pain that someone pain during testing predicted their performance. Fear- experiences is the sum of multiple descending and ascend- avoidance levels explain self-reported disability and time ing facilitatory and inhibitory pathways. Extensive evidence off work more accurately than actual pain levels or medical now supports the theory that persistent pain might be diagnosis does.136 This finding has led Waddell and other caused by central sensitization, which could help explain experts to state that “the fear of pain may be more dis- why often no pain generator is found in chronic low back abling than pain itself.”238 pain.54 Large, population-based studies have found that indi- viduals with high levels of pain catastrophizing, character- ized by excessively negative thoughts about pain and high Psychosocial Factors and Low Back Pain fear of movement and injury or reinjury (kinesiophobia), Pain is an individual experience, and biomechanical and and who had back pain at baseline were much more likely neurologic factors alone do not explain much of the vari- to have especially severe or disabling pain at follow-up ance seen clinically in patients with back pain. Multiple evaluation compared with those who did not catastroph- psychosocial factors have been found to play a role in low ize.255 The presence of catastrophizing is not limited to back pain. This is briefly discussed here and more thor- back pain and is often part of a larger pattern of relation- oughly discussed in the chapter on chronic pain (see ships and thought processes. Chapter 37), as these issues are shared by multiple painful Patients’ beliefs about pain and their approach to conditions and not just low back pain. dealing with pain have been consistently found to affect outcomes. Fortunately, changes in these beliefs and cogni- Depression, Anxiety, and Anger tive patterns are possible. Multidisciplinary pain programs It appears that between 30% and 40% of those with chronic have proven effective in decreasing fear-avoidant beliefs back pain also have depression.125 This rate is so high and catastrophizing (see Chapter 37).208 These changes in because patients who are depressed are more likely to beliefs can also improve function. For example, a study in develop back pain and to become more disabled by pain, which a group of patients with chronic low back pain and also because some patients with persistent pain underwent a cognitive-behavioral treatment program become depressed. Patients who are depressed are at found that, although there were not significant changes in increased risk of developing back and neck pain. In a pain intensity, those with reductions of fear-avoidance recent analysis of factors leading to the onset of back and beliefs had significant reductions in disability. Changes in neck pain, those in the highest quartile for depression fear-avoidant beliefs accounted for 71% of the variance in scores had a four-fold increased risk of developing low reduction in disability in this study.258 back pain than those in the lowest quartile for depression scores.45 Strong evidence also shows that psychosocial factors are closely linked to the transition from acute pain History and Physical Examination of to chronic pain and disability. In a study of 1628 patients the Low Back with back pain seen at a pain clinic, those with a comorbid diagnosis of depression were more than three times more A complete history and physical examination is important likely to be in the worst quartiles of physical and emo- in the evaluation of low back pain to determine the cause tional functioning on the 36-Item Short-Form Health of the symptoms, rule out serious medical disease, and Survey than those who were not depressed.79 Multiple determine whether further diagnostic evaluation is needed. other studies have found that depression, anxiety, and dis- tress are strongly related to pain intensity, duration, and History disability.128 Research has also shown a high correlation with anger As with any pain history, features of back pain that should measurements and pain, thought to be related to deficient be explored include location; character; severity; timing, opioid modulation in those with high anxiety, anger, and including onset, duration, and frequency; alleviating and  CHAPTER 33 Low Back Pain 719 aggravating factors; and associated signs and symptoms. Besides determining a diagnosis, a purpose of the history Each of these features can assist the clinician in obtaining is to explore the patient’s perspective and illness experi- a diagnosis and prognosis and determining the appropri- ence. Certain psychosocial factors are valuable in determin- ate treatment. Elements of historical information that ing prognosis (Box 33-3). Factors such as poor job suggest a serious underlying condition as the cause of the satisfaction, catastrophic thinking patterns about pain, the pain such as cancer, infection, long tract signs, and fracture presence of depression, and excessive rest or downtime are are called red flags (Box 33-2). When these are present, much more common in patients in whom back pain further workup is necessary (Table 33-1). becomes disabling. These are called yellow flags because the clinician should proceed with caution, and further psychological evaluation or treatment should be consid- BOX 33-2 ered if they are present. Some of these psychosocial factors “Red Flags”: Most Common Indications from are addressed by specific questions, and some become History and Examination for Pathologic Findings evident through statements that patients make during the Needing Special Attention and Sometimes history as they describe their illness experience. Questions Immediate Action (Including Imaging) about, for example, what patients believe is causing the pain, their fear and feelings surrounding this belief, their Children 55 years old back pain is affecting their lives (including work and home History of violent trauma Nonmechanical nature of pain (i.e., constant pain not life) can yield valuable information. Many of these yellow affected by movement, pain at night) flags are better prognostic indicators than the more tradi- History of cancer tional medical diagnoses.239 Systemic steroid use Drug abuse HIV infection or other patients who are immunocompromised BOX 33-3 Unintentional weight loss Systemically ill, particularly signs of infection such as fever Some Common “Yellow Flags” Associated with the or night sweats Development of Chronic Disabling Pain, Suggesting Persisting severe restriction of motion or intense pain with Additional Attention May Be Necessary minimal motion Structural deformity Presence of catastrophic thinking: there is no way the Difficulty with micturition patient can control the pain, that disaster will occur if the Loss of anal sphincter tone or fecal incontinence, saddle pain continues, etc. anesthesia Expectations that the pain will only worsen with work or Progressive motor weakness or gait disturbance activity Marked morning stiffness Behaviors such as avoidance of normal activity and Peripheral joint involvement extended rest Iritis, skin rashes, colitis, urethral discharge, or other Poor sleep symptoms of rheumatologic disease Compensation issues Inflammatory disorder such as ankylosing spondylitis is Emotions such as stress and anxiety suspected Work issues, such as poor job satisfaction and poor Family history of rheumatologic disease or structural relationship with supervisors abnormality Extended time off work Table 33-1 Sensitivities and Specificities of Different Elements of the History and Examination for Some Specific Causes of Low Back Pain Disease or Group of Diseases Symptom or Sign Sensitivity Specificity Spinal malignancy Age >50 years 0.77 0.71 Previous history of cancer 0.31 0.98 Unexplained weight loss 0.15 0.94 Pain unrelieved by bed rest 0.90 0.46 Pain lasting >1 month 0.50 0.81 Failure to improve with 1 month of conservative therapy 0.31 0.90 Erythrocyte sedimentation rate >20 mm 0.78 0.67 Spinal infection Intravenous drug abuse, urinary tract infection, skin infection 0.40 — Fever 0.27-0.83* 0.98 Vertebral tenderness “Reasonable” “Low” Age >50 years 0.84 0.61 Compression fracture Age >70 years 0.22 0.96 Corticosteroid use 0.66 0.99 Herniated intervertebral disk Sciatica 0.95 0.88 From Nachemson A, Vingard E: Assessment of patients with neck and back pain: a best-evidence synthesis. In Nachemson AL, Johnsson B, editors: Neck and back pain: the scientific evidence of causes, diagnosis, and treatment, Philadelphia, 2001, Lippincott Williams & Wilkins. *The sensitivity of “fever.” 720 SECTION 4 Issues in Specific Diagnoses Table 33-2 Physical Examination for Low Back Pain Examination Component Specific Activity Reason for This Part of the Examination Observation Observation of overall posture Determine whether structural abnormality or muscle imbalances are present Observation of lumbar spine Further define muscle imbalance and habitual posture Observation of the skin Search for diagnoses such as psoriasis, shingles, or vascular disease as cause of the pain Observation of gait Screen the kinetic chain and determine whether muscular, neurologic, or joint problems are contributing to symptoms Palpation Bones Search for bony problems such as infection or fracture Facet joints Identify whether specific levels are tender Ligaments and intradiskal spaces Determine whether these are tender Muscles Search for trigger points, muscle spasms, muscle atrophy Active range of motion Forward flexion Amount, quality if painful Extension — Side bending Same, also side to side differences Rotation — Neurologic examination Manual muscle testing of L1-S1 myotomes Determine weakness Pinprick and light touch sensation, L1-S1 Determine sensory loss dermatomes Reflexes: patellar, hamstring, Achilles Test injury to L4, L5, or S1 roots if diminished, upper motor neuron disease if brisk Balance and coordination testing Signs of upper motor neuron disease Plantar responses Same Straight leg raise Neural tension at L5 or S1 Femoral nerve arch Neural tension at L3 or L4 Orthopedic special tests Abdominal muscle strength Determines weakness and deconditioning Pelvis stabilizer strength (i.e., gluteus medius, Determines weakness and deconditioning maximus, etc.) Tightness or stiffness of hamstrings Determines areas of poor flexibility Tightness or stiffness of hip flexors — Tightness or stiffness of hip rotators — Prone instability test Signs of instability Physical Examination Table 33-2 outlines a thorough examination of the lumbar spine. Observation Observation should include a survey of the skin, muscle mass, and bony structures, as well as observation of overall posture (Figures 33-13 and 33-14, Table 33-3) and the position of the lumbar spine in particular. Gait should also be observed for clues regarding etiology and contributing factors. Palpation Palpation should begin superficially and progress to deeper tissues. It can be done with the patient standing. To ensure that the back muscles are fully relaxed, palpation is often done with the patient lying prone, perhaps with a pillow under the abdomen to slightly flex the spine into a posi- tion of comfort. It should proceed systematically to deter- mine what structures are tender to palpation. Range of Motion A B C D Quantity of Range of Motion. Several methods can be FIGURE 33-13 Four types of postural alignment. A, Ideal alignment. used to measure spinal range of motion (ROM). These B, Kyphosis-lordosis posture. C, Flat back posture, D, Sway-back posture. include using a single or double inclinometer; measuring (Modified from Kendall FP, McCreary EK: Trunk muscles in muscle testing and the distance of fingertips to floor; and, for forward flexion, function, Philadelphia, 1983, Lippincott Williams & Wilkins.) a Schober test (measuring distraction between two marks on the skin during forward flexion). Of these methods, the  CHAPTER 33 Low Back Pain 721 people without back pain also have limited range. ROM can also change depending on the time of day, the effort the patient expends, and many other factors.263 Quality of Range of Motion. The examiner should record whether there are abnormalities in the patient’s movement pattern during ROM, such as a “catch” in the range or whether or not it causes pain. This might give clues to the diagnosis. For example, pain with forward flexion can signify disk disease, and pain with extension can indicate 30° spondylolisthesis, zygapophyseal joint disease, or spinal stenosis. Neurologic Examination The neurologic examination of the lower limbs can rule out clinically significant nerve root impingement and other neurologic causes of leg pain (Table 33-4). The physical A B C examination should logically proceed to discover whether FIGURE 33-14 The effect of pelvic tilting on the inclination of the base of or not a particular root level is affected by combining the the sacrum to the transverse plane (sacral angle) during upright standing is findings of weakness, sensory loss, diminished or absent shown. A, Tilting the pelvis backward reduces the sacral angle and flattens the reflexes, and special tests such as the straight leg–raising lumbar spine. B, During relaxed standing, the sacral angle is about 30 degrees. maneuver. Upper motor neuron abnormalities should also C, Tilting the pelvis forward increases the sacral angle and accentuates the lumbar lordosis. (Modified from Sahrmann SA: Movement impairment syndromes be ruled out. The accuracy of the neurologic examination of the lumbar spine: diagnosis and treatment of movement impairment syndromes, in diagnosing herniated disk is moderate. The accuracy can St Louis, 2002, Mosby.) be increased considerably, however, with combinations of findings.59 The sensitivity and specificity of different find- ings for lumbar radiculopathy have been well studied Table 33-3 Factors That Affect Posture (Table 33-5). Reason for Orthopedic Special Tests to Assess for Relative Abnormality Clinical Example Strength and Flexibility Bone structure Compression fractures Scheuermann disease Back pain may be caused by deconditioning, poor endur- Ligamentous laxity Hyperextension of the knees, elbows ance, and muscle imbalances. Identifying inefficient or abnormal movement patterns of muscles that control the Muscle and fascial Tight hamstrings that cause a posterior pelvic movement of the spine and the position of the pelvis help length tilt Weak and long abdominal muscles that allow direct the exercise prescription. an anterior pelvic tilt Because of its stabilizing effect on the spine, abdominal Body habitus Obesity or pregnancy causes changes in force muscle strength and endurance is important. Several dif- and increased lumbar lordosis ferent methods can be used to measure abdominal muscle strength and control (Figures 33-15 and 33-16). One Neurologic disease Spasticity causes an extension pattern of the lower limb grading system assesses if the patient is able to maintain a neutral spine position while adding increasingly more Mood Depression causes forward slumped shoulders challenging leg movements (Figure 33-17). Habit Long-distance cyclists have increased thoracic Besides determining the strength of the abdominals, kyphosis and flat spine from prolonged strength testing of the back muscles and pelvic stabilizers, positioning while riding such as the hip abductors, can be useful. Assessing for areas of relative inflexibility is also important. Commonly per- formed tests are hip flexor flexibility, hamstring flexibility, double inclinometer has been shown to correlate the other hip extensors’ length, and gastrocnemius/soleus closest to measurements on radiographs.88 Fingertip to length. Balance challenges, such as the ability to maintain floor has good interrater and intrarater reliability, but this single-footed stance, the ability to lunge or squat, and takes into account the movement of the pelvis and is other functional tests are also helpful to determine a affected by structures outside the spine, such as tight ham- patient’s baseline status. strings.176 A Schober test is commonly used to assess a decrease in forward flexion in ankylosing spondylitis. It is Orthopedic Special Tests for sensitive for this condition but is not specific. General Lumbar Segmental Instability figures for normal ROM are forward flexion, 40 to 60 Many clinicians and researchers believe that one cause of degrees; extension, 20 to 35 degrees; lateral flexion, 15 to low back pain is segmental instability that responds to 20 degrees; and rotation, 3 to 18 degrees. Studies to deter- specific stabilization treatments. Therefore, accurately mine normal ROM in adults who are asymptomatic have identifying this group from other forms of low back pain found large variations.172 The importance of decreased could be important. These special tests include passive ROM in patients with back pain is unclear because many intervertebral motion testing and the prone instability test. 722 SECTION 4 Issues in Specific Diagnoses Table 33-4 Lumbar Root Syndromes Reflexes or Special Tests Root Dermatome Muscle Weakness Affected Paresthesias L1 Back, over trochanter, groin None None Groin L2 Back, front of thigh to knee Psoas, hip adductor None Occasionally front of thigh L3 Back, upper buttock, front of thigh Psoas, quadriceps—thigh Knee jerks sluggish, pain on full Inner knee, anterior lower leg and knee, medial lower leg wasting straight leg raise L4 Inner buttock, outer thigh, inside Tibialis anterior, extensor Straight leg raise limited, neck Medial aspect of calf and ankle of leg, dorsum of foot, big toe hallucis flexion pain, weak knee jerk, side flexion limited L5 Buttock, back and side of thigh, Extensor hallucis, peroneals, Straight leg raise limited to one Lateral aspect of leg, medial lateral aspect of leg, dorsum of gluteus medius, ankle side, neck flexion pain, hamstring three toes foot, inner half of sole, and first, dorsiflexors, reflex decreased, crossed second, and third toes hamstrings—calf wasting leg–raising pain S1 Buttock, back of thigh, and lower Calf and hamstrings, wasting of Straight leg raise limited, decreased Lateral two toes, lateral foot, leg gluteals, peroneals, plantar ankle jerk lateral leg to knee, plantar flexor aspect of foot S2 Same as S1 Same as S1, except peroneals Straight leg raise limited Lateral leg, knee, heel S3 Groin, inner thigh to knee None None None S4 Perineum: genitals, lower sacrum Bladder, rectum None Saddle area, genitals, anus, impotence From Maguire JH: Osteomyelitis. In Braunwald E, Fauci AS, Kasper DL, et al, editors: Harrison’s principles of internal medicine, ed 15, New York, 2001, McGraw-Hill. Table 33-5 Lumbosacral Radiculopathy in Patients With Sciatica* Positive Lumbosacral Negative Lumbosacral Finding† Sensitivity (%) Specificity (%) Radiculopathy Radiculopathy Motor Examination Weak ankle dorsiflexion 54 89 4.9 0.5 Ipsilateral calf wasting 29 94 5.2 0.8 Sensory Examination Leg sensation abnormal 16 86 NS NS Reflex Examination Abnormal ankle jerk 48 89 4.3 0.6 Other Tests Straight leg–raising maneuver 73-98 11-61 NS 0.2 Crossed straight leg–raising maneuver 23-43 88-98 4.3 0.8 From McGee SR: Evidence-based physical diagnosis, Philadelphia, 2001, Saunders. *Diagnostic standard: For lumbosacral radiculopathy, surgical finding of disk herniation compressing the nerve root. † Definition of findings: For ipsilateral calf wasting, maximum calf circumference at least 1 cm smaller than on contralateral side; for straight leg–raising maneuvers, flexion at hip of supine patient’s leg, extended at the knee, causes radiating pain in affected leg (pain confined to back or hip is a negative response); for crossed straight leg–raising maneuver, raising contralateral leg provokes pain in the affected leg. NS, Not significant. Passive Intervertebral Motion Testing. The patient lies lifted. This is because the extensors are able to stabilize the prone. The examiner applies a firm steady anteriorly spine in this position.100,147 directed pressure over the spinous process and assesses Examining the Area Above and the amount of vertebral motion and whether pain is Below the Lumbar Spine provoked.100 Similar to the evaluation of other joints, the areas above Prone Instability Test. The patient lies prone, with the and below the lumbar spine should be evaluated to be torso on the examining table and the legs over the edge of sure nothing is missed. ROM of the hip joints should the table with the feet resting on the floor. The examiner be assessed, and a quick screen of the knee and ankle performs passive intervertebral motion testing at each level joint can determine whether disease in these areas is and notes provocation of pain. Then the patient lifts the contributing to the back problem. The thoracic spine legs off the floor, and the painful levels are repeated. A can be quickly screened as well during ROM and positive test is when the pain disappears when the legs are palpation.  CHAPTER 33 Low Back Pain 723 50% 60% 70% 90° 75° 80% ° 60 ° 45 90% ° 30 A 15° 100% 0° B A C FIGURE 33-15 Trunk raising forward: grading. The curl trunk sit-up is per- formed with the patient lying supine and with the leg extended. The patient posteriorly tilts the pelvis and flexes the spine, and slowly completes a curled trunk sit-up. Kendall and McCreary114 state that the “crucial point in the test B for the abdominal muscle strength is at the moment the hip flexors come into strong action. The abdominal muscle at this point must be able to oppose the force of the hip flexors in addition to maintain the trunk curl.” At the point where the hip flexors strongly contract, patients with weak abdominal muscles will tilt the pelvis anteriorly and extend the low back. A, A 100% or normal grade is the ability to maintain spinal flexion and come into the sitting position with the hands clasped behind the head. B, An 80% or good grade is the ability to do this with the forearms folded across the chest. C, A 60% or fair grade is the ability to do this with the forearms extended forward. A 50% or fair C grade is the ability to begin flexion but not maintain spinal flexion with the FIGURE 33-16 Leg lowering: grading. In the second test, the patient raises forearms extended forward. (Modified from Kendall FP, McCreary EK: Trunk the legs one at a time to a right angle, and then flattens the low back on the muscles in muscle testing and function, Philadelphia, 1983, Lippincott Williams and table. The patient slowly lowers the legs while holding the back flat. A 100% Wilkins.) or normal grade is the ability to hold the low back flat on the table as the legs are lowered to the fully extended position. An 80% or good grade is the ability to hold the low back flat and lower the legs to a 30-degree angle. A, A 60% or fair plus grade is the ability to lower the legs to 60 degrees with Illness Behavior and Nonorganic Signs Seen on the low back flat. B, The pelvis tilted anteriorly and the low back arched as Physical Examination the legs were lowered. C, The final position. Kendall and McCreary114 note that this second test is more important than the first (see Figure 33-15) in Multiple reasons can explain why patients with back pain grading muscles essential to proper posture, and that often patients who do might display symptoms out of proportion to injury. well on the first test do poorly on the second. (Modified from Kendall FP, McCreary EK: Trunk muscles in muscle testing and function, Philadelphia, 1983, Illness behaviors are learned behaviors and are responses Williams and Wilkins.) that some patients use to convey their distress. Several studies have found that patients with chronic low back pain and chronic pain syndrome experience significant anxiety during the physical examination, even to the level findings that may also indicate psychological distress. They experienced during panic attacks. This anxiety is generally are as follows: manifest as avoidance behavior, such as decreased ROM or Inappropriate tenderness that is widespread or poor effort with muscle testing.92 Other reasons for illness superficial. behavior include malingering and a desire to prove to Pain on testing that only simulates loading the spine, physicians how disabling the pain is. One way to assess for such as light pressure applied to the top of the head, illness behavior on physical examination is to perform which reproduces back pain, or rotating the hips and parts of the examination to search for Waddell signs.238 shoulders together to simulate twisting without actu- These may be seen with malingering, but are nonorganic ally moving the spine, which reproduces back pain. 724 SECTION 4 Issues in Specific Diagnoses A B C D E FIGURE 33-17 Abdominal strength grading. A, The patient lies supine with the knees bent (supine hook lying). The physician cues the patient to activate the transversus abdominis (“Pull your belly button toward your backbone”), and a very slight lumbar lordosis is maintained in a neutral position in which the spine is neither flexed nor extended. The ability to maintain the neutral spine is progressively challenged by loading the spine via lower extremity movements. Grading is as follows. B, Grade 1: The patient is able to maintain a neutral spine while extending one leg by dragging the heel along the table; the other leg remains in the starting position. C, Grade 2: The patient is able to maintain a neutral spine while holding both legs flexed 90 degrees at the hip and 90 degrees at the knee, and touching one foot to the mat and then the other. D, Grade 3: The patient is able to maintain a neutral spine while extending one leg by dragging the heel along the table. The other leg is off the mat and flexed 90 degrees at the hip and 90 degrees at the knee. E, Grade 4: The patient is able to maintain a neutral spine while extending one leg hovered an inch or two above the table, and the other leg is off the mat and flexed 90 degrees at the hip and 90 degrees at the knee. Grade 5: The patient is able to extend both legs a few inches off the mat and back again while maintaining the spine in neutral. Inconsistent performance when testing the same when red flags are present in the history. As an initial thing in different positions, such as a difference in screening tool for lumbar spine pathology, however, they outcome of the straight leg–raising test with the have very low sensitivity and specificity.84 Anterior-posterior patient supine versus sitting. and lateral views are the two commonly obtained views. Regional deficits in strength or sensation that do not Oblique views can be obtained to examine for a spondy- have an anatomic basis. lolysis by visualizing the pars interarticularis and the Overreaction during the physical examination. “Scottie dog” appearance of the lumbar spine (Figure Findings in three of these five categories suggest psycho- 33-18). Lateral flexion-extension views are obtained to logical distress and also suggest that other parts of the check for dynamic instability, although the literature does physical examination that require patient effort or report- not support their usefulness.64 They are potentially most ing of symptoms might be inaccurate. helpful from a surgical screening perspective when evaluat- ing a spondylolisthesis. They are commonly obtained in patients after trauma or surgery. Clinical Evaluation: Diagnostics Magnetic Resonance Imaging MRI is the preeminent imaging method for evaluating Imaging Studies degenerative disk disease, disk herniations, and radicu- Imaging of the lumbar spine should be used in the evalu- lopathy (Figure 33-19). On T2-weighted imaging, the ation of low back pain if specific pathology needs to annulus can be differentiated from the internal nucleus, be confirmed after a thorough history and physical and annular tears can be seen as high-intensity zones. examination. These zones are of unclear clinical significance but are thought to be potential pain generators. Plain Radiography Adding gadolinium contrast enhancement helps to Conventional radiographs are indicated in trauma to eval- identify structures with increased vascularity. Contrast is uate for fracture and to look for bony lesions such as tumor always indicated in evaluating for tumor or infection or to  CHAPTER 33 Low Back Pain 725 determine scar tissue (vascular) ver