low back pain (braddom 4th)

871

CHAPTER 40

LOW BACK PAINKaren P. Barr and Mark A. Harrast

Low back pain has become a costly burden to society and a leading cause of disability and loss of productivity. This chapter outlines the anatomy and biomechanics of the lumbar spine and our current understanding of the physi-ology of low back pain. We discuss the clinical evaluation and treatment of various etiologies of low back pain and leg pain caused by lumbar spine disease.

Epidemiology

Low back pain is a symptom, not a disease, and has many causes. It is generally described as pain between the cos-tal margin and the gluteal folds. It is extremely common. About 40% of people say that they have had low back pain within the past 6 months.233 Studies have shown a lifetime prevalence as high as 84%.240 Onset usually begins in the teens to early 40s. Most patients have short attacks of pain that are mild or moderate and do not limit activities, but these tend to recur over many years. Most episodes resolve with or without treatment. The median time off work for a back injury is 7 days, and many people with low back pain never alter their activity. A small percentage of low back pain becomes chronic, however, and causes significant disability. In most studies about half of the sick days used for back pain are accounted for by the 15% of people who are home from 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. Just over 1% of adults in the United States are permanently disabled by back pain, and another 1% are temporarily disabled.151

The percentage of patients disabled by back pain, as well as the cost of low back pain, has steadily increased dur-ing the past 30 years. This appears to be more from social causes than from a change in the conditions that cause low back pain. The two most commonly cited factors are the increasing societal acceptance of back pain as a reason to become disabled, and changes in the social system that pay benefits to patients with back pain.238

Anatomy and Biomechanics of the Lumbar Spine

General ConceptsThe lumbar spine has a dichotomous role in terms of func-tion, which is strength coupled with flexibility. The spine per-forms a major role in support and protection (strength) of the spinal canal contents (spinal cord, conus, and cauda equina) but also give us inherent flexibility, allowing us to place our limbs in appropriate positions for everyday functions.

The strength of the spine results from the size and arrangements of the bones, as well as from the arrange-ment of the ligaments and muscles. The inherent flexibility results from the large number of joints placed so closely together in series. Each vertebral segment can be thought of as a three-joint complexone intervertebral disk with vertebral end plates, and two zygapophyseal joints. The typical lordotic framework of the lumbar spine assists with this flexibility but also increases the ability of the lumbar spine to absorb shock.

The VertebraeThe bony anatomy of the lumbar spine consists of five lum-bar vertebrae. A smaller percentage of the population has four (the fifth vertebrae is sacralized) or six (the first sacral segment is lumbarized). Anatomic variants also exist consist-ing of a partially lumbarized S1. The lumbar vertebrae have distinct components, which include the vertebral body, the neural arch, and the posterior elements (Figure 40-1). The vertebral bodies increase in size as you travel caudally in the spine. The lower three are typically more wedge-shaped (taller anteriorly), which helps create the normal lumbar lordosis. The structure of these large vertebral bodies serves its weight-bearing function well to support axially directed loads; however, they would fracture more routinely were it not for the shock-absorbing intervertebral disks placed stra-tegically between the vertebral bodies.

The sides of the bony neural arch are the pedicles, which are thick pillars that connect the posterior elements to the vertebral bodies. They are designed to resist bending and to transmit forces back and forth from the vertebral bodies to the posterior elements. The posterior elements consist of the laminae, the articular processes, and the spinous pro-cesses. The superior and inferior articular processes of adja-cent vertebrae create the zygapophyseal joints. The pars interarticularis is a part of the lamina between the supe-rior and inferior articular processes (Figure 40-2). The pars is the site of stress fractures (spondylolysis) because it is subjected to large bending forces. This occurs as the forces transmitted by the vertically oriented lamina undergo a change in direction into the horizontally oriented pedicle.23

The JointsThe Intervertebral Disk

The intervertebral disk and its attachment to the vertebral end plate are considered a secondary cartilaginous joint, or symphysis. The disk consists of the internal nucleus pulpo-sus and the outer annulus fibrosus. The nucleus pulposus is the gelatinous inner section of the disk. It consists of

872 SECTION 4 Issues in Specific Diagnoses

water, proteoglycans, and collagen. The nucleus pulposus is 90% water at birth. Disks desiccate and degenerate as we age and lose some of their height, which is one reason we are slightly shorter in our geriatric years.

The annulus fibrosus consists of concentric layers of fibers at oblique angles to each other, which help to with-stand strains in any direction. The outer fibers of the annu-lus have more collagen and less proteoglycans and water than the inner fibers.19 The varying composition supports the functional role of the outer fibers in acting like a liga-ment to resist flexion, extension, rotation, and distraction forces.

The main function of the intervertebral disk is shock absorption (Figure 40-3). It is primarily the annulus, not the nucleus, that acts as the shock absorber. (The nucleus is primarily a liquid and is incompressible.) When an axial load occurs, the increase in force in the incompressible nucleus pushes on the annulus and stretches its fibers. If the fibers break, then a herniated nucleus pulposus results.

The Zygapophyseal Joints

The zygapophyseal joints (also known as Z joints and facet joints) are paired synovial joints, that is, they have a synovium and a capsule (Figure 40-4). Their alignment or direction of joint articulation determines the direction of

motion of the adjacent vertebrae. The lumbar zygapophy-seal joints lie in the sagittal plane and thus primarily allow flexion and extension. Some lateral bending and very little rotation are allowed, which limits torsional stress on the lumbar disks. Rotation is more a component of thoracic spine motion. The majority of spinal flexion and exten-sion (90%) occurs at the L4L5 and L5S1 levels, which contributes to the high incidence of disk problems at these levels.

Biomechanics

Because flexion loads the anterior disk, the nucleus is dis-placed posteriorly.111 If the forces are great enough, the nucleus can herniate through the posterior annular fibers. The lateral fibers of the posterior longitudinal ligaments are thinnest, however, making posterolateral disk hernia-tions the most common (Figure 40-5). The posterolateral

Superiorarticular

facet

Transverseprocess

Spinousprocess

Inferiorarticular

facet

Pedicle

Vertebralbody

Inferiorvertebral

notch

Lamina

FIGURE 40-1 Lateral view of the lumbar vertebrae. (Modified from Parke WW: Applied anatomy of the spine. In Rothman RH, Simeone FA, editors: The spine, ed 4, Philadelphia, 1999, Saunders.)

12

3

FIGURE 40-2 An oblique dorsal view of an L5 vertebra, showing the parts of the vertebral arch: 1, pars interarticularis (crosshatched area); 2, pars lami-naris; and 3, pars pedicularis. The dotted line indicates the most frequent site of mechanical failure of the pars interarticularis. (Modified from Parke WW: Applied anatomy of the spine. In Rothman RH, Simeone FA, editors: The spine, ed 4, Philadelphia, 1999, Saunders.)

A

B

C

DFIGURE 40-3 The mechanism of weight transmission in an intervertebral disk. A, Compression increases the pressure in the nucleus pulposus. This is 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 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 next. (Modified from Bogduk N: The inter-body joint and the intervertebral discs. In Bogduk N, editor : Clinical anatomy of the lumbar spine and sacrum, ed 3, Edinburgh, UK, 1977, Churchill Livingstone.)

873CHAPTER 40 Low Back Pain

portion of the disk is most at risk when there is forward flexion accompanied by lateral bending (i.e., bending and twisting). The zygapophyseal joints cannot resist rotation when the spine is in flexion. This increases torsional shear forces in the lumbar spine, making rotary movements in a forward-flexed posture probably the most risky for lum-bar disks.

The LigamentsThe two main sets of ligaments of the lumbar spine are the longitudinal ligaments and the segmental ligaments. The two longitudinal ligaments are the anterior and posterior longitudinal ligaments. They are named according to their position on the vertebral body. The anterior longitudinal ligament acts to resist extension, translation, and rotation. 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 longitudinal ligament is twice as strong as the posterior longitudinal ligament.

The main segmental ligament is the ligamentum fla-vum, which is a paired structure joining adjacent laminae. It is the ligament that is pierced when performing lumbar punctures. It is a very strong ligament but is elastic enough

to allow flexion. Flexing the lumbar spine puts this liga-ment on stretch, decreasing its redundancy and making it easier to pierce during a lumbar puncture.

The other segmental ligaments are the supraspinous, interspinous, and intertransverse. The supraspinous liga-ments are the strong ligaments that join the tips of adjacent spinous processes and act to resist flexion. These ligaments, along with the ligamentum flavum, act to restrain the spine and prevent excessive shear forces in forward bending. This is supported by electromyographic studies that have shown that there is no active contraction of the erector spinae and hip extensor muscles when resting in lumbar flexion.

The MusclesMuscles With Origins on the Lumbar Spine

These muscles can be divided anatomically into posterior and anterior muscles. The posterior muscles include the latissimus dorsi and the paraspinals. The lumbar paraspi-nals consist of the erector spinae (iliocostalis, longissimus, and spinalis), which act as the chief extensors of the spine, and the deep layer (rotators and multifidi) (Figures 40-6 and 40-7). The multifidi are tiny segmental stabilizers that act to control lumbar flexion because they cannot produce enough force to truly extend the spine. Their most impor-tant function has been hypothesized to be that of a sensory organ to provide proprioception for the spine, given the

CCAC

FIGURE 40-4 A posterior view of the L3L4 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 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: The zygapophysial joints. In Bogduk N, editor : Clinical anatomy of the lumbar spine and sacrum, ed 3, Edinburgh, UK, 1977, Churchill Livingstone.)

Nerve rootcompressionin the lateral

recess

Caudaequina

Posterolateralherniated

nucleuspulposus

Nucleuspulposus

Defectin anulusfibrosus

Anulusfibrosus

FIGURE 40-5 Posterolateral intervertebral disk herniation.

Iliocostalis thoracis

Longissimus thoracis

Spinalis thoracis

Iliocostalis thoracis

Longissimus lumborum

Iliocostalis lumborum

FIGURE 40-6 The intermediate layer of back muscles: the erector spinae.


predominance of muscle spindles seen histologically in these muscles.

The anterior muscles of the lumbar spine include the psoas and quadratus lumborum. Because of the direct attachment of the psoas on the lumbar spine, tighten-ing this muscle accentuates the normal lumbar lordosis.

This can increase forces on the posterior elements and can contribute to zygapophyseal joint pain. The quadratus lumborum acts in side bending and can assist in lumbar flexion.

Abdominal Musculature

The superficial abdominals include the rectus abdominis and external obliques (Figure 40-8, A). The deep layer con-sists of internal obliques and the transversus abdominis (Figure 40-8, B). The transversus abdominis has received significant attention recently as an important muscle to train in treating low back pain. Its connection to the thora-columbar fascia (and consequently its ability to act on the lumbar spine) has probably been the major reason it has received such attention of late.

Thoracolumbar Fascia

The thoracolumbar fascia, with its attachments to the transversus abdominis and internal obliques, acts as an abdominal and lumbar brace. It decreases some of the shear forces that other muscles and lumbar motions cre-ate. This abdominal bracing mechanism results from con-traction of these deep abdominal muscles, which creates tension in the thoracolumbar fascia, which then creates an extension force on the lumbar spine without increasing shear forces.75

Pelvic Stabilizers

The pelvic stabilizers are considered core muscles because of their indirect effect on the lumbar spine, even though they do not have a direct attachment to the spine. The gluteus medius stabilizes the pelvis during gait. Weakness or inhibition of this muscle results in pelvic instability, which introduces lumbar side bending and rotation, creating increased shear or torsional forces on the lumbar disks.

The piriformis is a hip and sacral rotator and can cause excessive external rotation of the hip and sacrum when it is tight. This can result in increased shear forces at the lumbosacral junction (i.e., the L5S1 disk or Z joints).

Semispinalis capitis

Semispinalis cervicis

Spinalis thoracis

Multifidus

FIGURE 40-7 The deep back muscles: the multifidi.

Serratusanterior

Anterior layer ofrectus sheath

Externaloblique

5th costalcartilage

Anterior layerof rectus sheath

Externaloblique

Anterior superioriliac spine

Rectusabdominis

A

Serratusanterior

Anteriorlayer ofrectus

sheath

Externaloblique

(cut edges)

Internaloblique

Anteriorsuperior

iliac spine

Rectusabdominis

Posteriorlayer ofrectussheath

Transversusabdominis

Internaloblique

Rectusabdominis

Pectoralismajor

BFIGURE 40-8 A, The superficial abdominal muscles. B, The deep abdominal muscles.


Some practitioners also believe that other pelvic floor muscles act to maintain proper positioning of the spine and are an important focus of some spine rehabilitation programs.

Biomechanical Lifting in Relation to Muscular Activity and Disk Loads

The activity of the lumbar muscles correlates well with intradiskal pressures (i.e., when back muscles contract, there is an associated increase in disk pressure). These pres-sures change depending on spine posture and the activity undertaken. Figure 40-9 demonstrates the changes in L3 disk pressure under various positions and exercises.149,150 Adding rotation to the already flexed posture increases the disk pressure substantially. Comparing lifting maneuvers, it has been shown that there is not a significant difference in disk pressure when lifting with the legs (i.e., with the back straight and knees bent) versus lifting with the back (i.e., with a forward-flexed back and straight legs).6,7 What decreases the forces on the lumbar spine is lifting the load close to your body because the farther the load is from the chest, the greater the stress on the lumbar spine.7

The NervesThe conus medullaris ends at about bony level L2, and below this level is the cauda equina. The cauda equina con-sists of the dorsal and ventral rootlets, which join together in the intervertebral neuroforamen to become the spinal nerves (Figure 40-10). The spinal nerve gives off the ventral primary ramus. The ventral primary rami from multiple levels form the lumbar and lumbosacral plexus to inner-vate the limbs. The dorsal primary ramus, with its three branches (medial, intermediate, and lateral), innervates the posterior half of the vertebral body, the paraspinal muscles, and the zygapophyseal joints, and provides sen-sation to the back. The medial branch is the most impor-tant to remember because it innervates the zygapophyseal joints and lumbar multifidi and is the target during radio-frequency neurotomy for presumed zygapophyseal joint pain (Figure 40-11).24

Pathophysiology and Pain Generation

The Degenerative Spine CascadeKirkaldy-Willis et al.108 have supplied us with the most accepted theory describing the cascade of events in degen-erative lumbar spine disease that results in spondylotic changes, disk herniations, and eventually multilevel spinal stenosis (Figure 40-12). At the heart of this theory is the fact that, although the posterior zygapophyseal joints and the anterior intervertebral disks are separated anatomically, forces and lesions affecting one certainly alter and affect the other. For example, axial compressing injuries can

75 100 150 220 140 185 27525

%

A

%

150 180 210 100 140 130 35BFIGURE 40-9 A, Relative change in pressure (or load) in the third lumbar disk in various positions in living subjects. B, Relative change in pressure (or load) in the third lumbar disk during various muscle-strengthening exercises in living subjects. Neutral erect posture is considered 100% in these figures; other positions and activities are calculated in relationship to this. (Modified from Nachemson AL, Waddell G, Norlund AI: Epidemiology of neck and low back pain. In Nachemson AL, Johnsson B, editors: Neck and back pain: The scientific evidence of causes, diagnosis, and treatment, Philadelphia, 2000, Lippincott Williams & Wilkins.)

Arachnoid

Subarachnoidspace

Pia

Dura

Dorsal root

Ventral root

Dorsal rootganglion

Dural sleeve

Spinal nerve

Ventral ramus

Dorsal ramusFIGURE 40-10 A lumbar spinal nerve, its roots, and meningeal coverings. The nerve roots are invested by pia mater, and covered by arachnoid and dura as far as the spinal nerve. The dura of the dural sac is prolonged around the roots as their dural sleeve, which blends with the epineurium of the spinal nerve. (Modified from Bogduk N: Nerves of the lumbar spine. In Bogduk N, editor : Clini-cal anatomy of the lumbar spine and sacrum, ed 3, Edinburgh, UK, 1977, Churchill Livingstone.)


damage the vertebral end plates, which can lead to degen-erative disk disease, which eventually stresses the posterior joints, leading to the common degenerative changes seen in them over time. Torsional stress can injure the posterior joints and the disks, which in turn leads to increased stress on both these elements, resulting in further degenerative changes over time. When these degenerative changes affect one level, such as L4L5, a chain reaction occurs, placing stress on the levels above and below the currently affected level, and eventually resulting in more generalized multi-level spondylotic changes.

In studying lumbar degenerative disease, the question of which came first (disk degeneration or zygapophyseal joint degeneration) always arises. Fujiwara67 has answered this by studying multiple magnetic resonance images (MRIs) of aging spines. He hypothesizes that disk degeneration pre-cedes zygapophyseal joint osteoarthritis, and that it might take 20 years for zygapophyseal joint disease to occur after the onset of disk degeneration.

To describe the degenerative cascade in more detail, we will separate our discussion of the changes that occur in the posterior joints from those in the disk, but fully real-izing that they both can occur simultaneously and affect each other (see Figure 40-12). The degenerative changes that occur in the zygapophyseal joints from aging and repetitive microtrauma are similar to those that occur in the appendicular skeletal joints. The process begins with synovial hypertrophy, which eventually results in cartilage degeneration and destruction. With lessened and weak-ened cartilage and capsular laxity, the joint can become unstable. With the repetitive abnormal joint motion that results from this instability, the bony joint hypertrophies. This narrows the central canal and lateral recesses, poten-tially impinging nerve roots.

A similar process occurs anteriorly at the disk level from repetitive microtrauma of primarily shearing forces. 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 pulposus can herniate. Internal disk disruption can occur without herniation, however, because age and repeated stresses act-ing on the spine cause the gelatinous nucleus to become more fibrous over time. Tears in the annulus can progress to tears in the fibrous disk material, resulting in internal

disk disruption without frank herniation. All this results in a loss of disk height, which causes instability (because the end-plate connection to the disk is degenerated), as well as lateral recess and foraminal narrowing and poten-tial nerve root impingement. The loss of disk height also places new stresses on the posterior elements, resulting in further instability of the zygapophyseal joints and further degeneration and nerve root impingement.

Although this theory offers an explanation as to how the spine ages, it is still unclear why there is such a marked disconnect between the anatomic changes in the spine associated with aging, and back pain. Many patients with normal spine anatomy suffer from back pain, occasionally disabling pain, and many patients with marked degenera-tive changes on imaging are nearly or fully pain free. As a result, several theories have been developed to explain the occurrence of back pain.

Transverseprocess

Spinalnerve

Ventralprimary

ramus

Dorsalprimary

ramus

Superiorarticularfacet

Medialbranch

Zygapo-physealjoint

Inferiorarticularfacet

FIGURE 40-11 Observe that the innervation of the zygapophyseal joints derives from the medial branch off the dorsal primary ramus.

Posteriorjoints

Three jointcomplex

Intervertebraldisk

Synovialreaction

Circumferentialtears

Cartilagedestruction Herniation

Radialtears

Osteophyteformation

Internaldisruption

Capsularlaxity Instability

Loss diskheight

Subluxation Lateral nerveentrapment

Diskresorption

Enlargementarticular process

(and laminae)

One-levelcentral

stenosis

Osteophytesat back ofvertebralbodies

Effect of recurrent strainsat levels above and

below the original lesion

Multilevel degenerative lesions

Multilevel spinal stenosis

FIGURE 40-12 The spectrum of degenerative change that leads from minor strains to marked spondylosis and stenosis. (Modified from Kirkaldy-Willis WH, Wedge JH, Yong-Hing K, et al: Pathology and pathogenesis of lumbar spondylosis and stenosis, Spine 3:319-328, 1998, with permission of Lippincott Williams & Wilkins.)


Radiculitis and RadiculopathyMany patients with radicular pain have no neural impinge-ment noted on MRI. Studies have shown that disk hernia-tions can cause an inflammatory response.131,136,187 The mechanism stems from the fact that the nucleus pulpo-sus is highly antigenic as a result of being in an immu-noprotected setting in nonpathologic states. When the fluid of the nucleus pulposus is exposed to neural tissue of the spinal canal and neuroforamen through a defect in the annular fibers, an autoimmune-mediated inflamma-tory cascade begins. The inflammatory mediators gener-ated can cause swelling of the nerves. This can alter their electrophysiologic function, sensitizing these neurons and enhancing pain generation without specific mechanical compression.

The mechanism of mechanical compression of the nerve roots has been studied as well.13,184,185 Compression of nerve roots can induce structural and vascular changes as well as inflammation.150 Neural compression can result in impairment of intraneural blood flow, subsequently decreased nutrient supply to the neural tissue, local isch-emia, and formation of intraneural edema. This can set off an inflammatory cascade similar to that described above. Mechanical stimulation of lumbar nerve roots has also been shown to stimulate production of substance P, the neuropeptide known to modulate sensory nocicep-tive feedback.13 With these biochemical reactions, the local structural effects of mechanical compression (demy-elination and axonal transport block) just compound the symptomatic response.

Pain of Spinal StenosisThese mechanisms could also be responsible for neuro-genic claudication symptoms of lumbar stenosis. Newer theories, however, also support a spinal vascular role in stenosis symptoms.

If mechanical compression were the sole problem in spinal stenosis, decompressive surgeries would be the only needed cure. We know that this is untrue, and conse-quently alternative theories on the pathogenesis of symp-tomatic spinal stenosis have been studied. Two theories supporting a vascular component to symptoms of spinal stenosis are the venous engorgement and arterial insuffi-ciency theories.1

In the venous engorgement theory, the spinal veins of patients with stenosis dilate, causing venous congestion and stagnating blood flow.45 This pooling of blood in the spinal veins increases epidural and intrathecal pressures, leading to a microcirculatory, neuroischemic insult (i.e., an ischemic neuritis), which in turn leads to the typical neu-rogenic claudication symptoms of stenosis.

The arterial insufficiency theory of spinal stenosis is based on the arterial dilatation of the lumbar radicular vessels during lower limb exercise to provide increased blood flow and nourishment to the nerve roots. In patients with spinal stenosis, this reflex dilatation might be defective.14Because patients with spinal steno-sis are typically elderly, they are also at higher risk for atherosclerosis, which in turn just amplifies the arterial insufficiency.

Pain Generators of the Lumbar SpineThe low back is an anatomically diverse set of structures, and there are many potential sources of pain. One useful strategy to clarify these potential sources of pain is learning what low back structures are innervated (and can transmit pain through neural pain fibers) and what structures have no innervation (Box 40-1).

The sinuvertebral nerve innervates the anterior vertebral body, the external annulus, and the posterior longitudinal ligament. The posterior longitudinal ligament is a highly innervated structure and can play a significant role in low back pain perception with lumbar disk herniations. The medial branch of the dorsal primary ramus innervates the zygapophyseal joints and interspinous ligaments, as well as the lumbar multifidi. The other small branches of the dor-sal primary ramus innervate the posterior vertebral body and other lumbar paraspinal musculature and fascia. The anterior longitudinal ligament is innervated by the gray rami communicans, which branch off the lumbar sym-pathetic chain. The internal annulus fibrosus and nucleus pulposus do not have innervation and in nondisease states cannot transmit pain.

Because many structures are potentially a source of pain, theories have been developed to help practitioners deter-mine the cause of a particular patients pain. Some of the most common ones are described below.

Segmental Dysfunction

Segmental dysfunction can occur when either a segment is too stiff or too mobile. A segment encompasses the disk, the vertebrae on each side of the disk, and the muscles and ligaments that act across this area. Excessive stiffness is thought to be caused by arthritic and ligamentous changes. Excessive mobility, also called instability, or potentially better termed functional instability, can be the result of tissue damage, poor muscular endurance, or poor mus-cular control, and is usually a combination of all three factors. Structural changes from tissue damage, such as strained or failed ligaments that cause joint laxity, vertebral

A useful classification system to understand the potential sources of low back pain depends on knowing what structures are innervated (and can transmit pain) and what structures have no innervation.Innervated structures Bone: Vertebrae Joints: Zygapophyseal Disk: Only the external annulus and potentially diseased

disk Ligaments: Anterior longitudinal ligament, posterior

longitudinal ligament, interspinous Muscles and fascia Nerve rootNoninnervated structures Ligamentum flavum Internal annulus Disk: Nucleus pulposus

BOX 40-1

Potential Pain Generators of the Back


end-plate fractures, and loss of disk height, can lead to seg-mental dysfunction because of the altered anatomy. Mus-cles also provide a critical component of spinal stability. This is of particular interest to the physiatrist because it can be affected by exercise. In normal situations, only a small amount of muscular coactivation (about 10% of maxi-mal contraction) is needed to provide segmental stability. In a segment damaged by ligamentous laxity or disk dis-ease, slightly more muscle coactivation might be needed. Because of the relatively gentle forces required to perform the activities of daily living, muscular endurance is more important than absolute muscle strength for most patients. 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 strength and endurance needs increase. For example, in rapid breathing caused by exertion, there is rhythmic contraction and relaxation of the abdominal wall. A fit person can simultaneously provide spine support with abdominal wall muscles and meet breathing demands, but a less-fit person might not be able to do so and therefore could more easily become injured or have pain.139 This biomechanical model is particularly complex in the spine because of the presence of global movement patterns and segmental movement patterns. Two interrelated muscular tasks must be carried out at the same time: maintaining overall posture and position of the spine, and control of individual intersegmental relationships. Sufficient but not excessive joint stiffness is required at the segmental level to prevent injury and allow for efficient movement. This stiffness is achieved with specific patterns of muscle activ-ity, which differ depending on the position of the joint and the load on the spine. The inability to achieve this stiffness, and the resulting segmental problems, is thought to be a factor in low back pain.178

Muscular Imbalances and Neural Procession Problems

There appear to be consistent muscular problems in patients with chronic low back pain. Some of these factors might exist preinjury and make the spine more suscepti-ble to injury, and some are adaptations to injury. Just as is seen in other areas of the body (such as the knee), muscle function and strength around the spine are altered after injury.177 Studies have shown abnormal firing patterns in the deep stabilizers of the spine and transversus abdomi-nus with activities such as limb movements, accepting a heavy load, and responding to balance challenges. Other researchers have found strength ratio abnormalities and endurance deficits in patients with low back pain, such as abnormal flexion to extension strength ratios and lack of endurance of torso muscles.140

Studies of lumbar paraspinals have found several abnor-malities in patients with low back pain. Multiple imaging studies have demonstrated paraspinal muscle atrophy, particularly of the multifidi, in patients with chronic low back pain.178 Recovery of the multifidi does not appear to occur spontaneously with the resolution of back pain.91 Biopsies of multifidi in patients with low back pain also show abnormalities. Atrophy of type 2 muscle fibers is found, and internal structural changes of type 1 fibers that give them a moth-eaten appearance are seen. In a study

of patients undergoing surgery for lumbar disk hernia-tions with duration of symptoms from 3 weeks to 1 year, multifidi biopsies collected at the time of surgery showed type 2 muscle atrophy and type 1 fiber structural changes. Biopsies were repeated 5 years postoperatively. Type 2 fiber atrophy was still found in all patients, in both those who had improved with surgery and those who had not. In the positive outcome group, however, the percentage of type 1 fibers with abnormal structures had decreased, and in the negative outcome group there was a marked increase in abnormal type 1 fibers.175 Increasingly strong scientific support is found for the multifactorial nature of low back pain, which includes both structural and dynamic factors.

This gives a theoretical basis for treatment aimed at improving spine biomechanics as a means of treating low back pain, along with other treatments aimed at pain man-agement. The research in this area is intriguing but not yet conclusive. It is unclear whether these muscular abnormal-ities are the result of back pathology that leads to pain, or the cause of back pain. Study results conflict regarding consistent deficits in patients with back pain. This again reflects the heterogeneous nature of the group of patients classified as having low back pain, and that different fac-tors predominate for different patients.

Psychosocial Factors and Low Back Pain

Pain is an individual experience, and biomechanical and neurologic factors alone do not explain much of the vari-ance seen clinically in patients with back pain. Multiple psychosocial factors have been found to play a role in low back pain. This is briefly discussed here and more thoroughly discussed in the chapter on chronic pain (see Chapter 42), as these issues are shared by multiple painful conditions and not just low back pain.

Depression, Anxiety, and Anger. It appears that between 30% and 40% of those with chronic back pain also have depression.115 This rate is so high because depressed patients are more likely to develop back pain and to become more disabled by pain, and because some patients with persistent pain become depressed. Patients who are depressed are at increased risk of developing back and neck pain. In a recent analysis of factors leading to the onset of back and neck pain, those in the highest quartile for depression scores had a fourfold increased risk of devel-oping low back pain than those in the lowest quartile for depression scores.39 Strong evidence also shows that psy-chosocial factors are closely linked to the transition from acute pain to chronic pain and disability. In a study of 1628 patients with back pain seen at a pain clinic, those with a comorbid diagnosis of depression were more than 3 times more likely to be in the worst quartiles of physi-cal and emotional functioning on the 36-Item Short-Form Health Survey than those who were not depressed.70 Mul-tiple other studies have found that depression, anxiety, and distress are strongly related to pain intensity, duration, and disability.118

Research has also shown a high correlation with anger measurements and pain, thought to be related to deficient opioid modulation in those with high anxiety, anger, and fear reactivity.32 Patients with posttraumatic stress disorder have a high incidence of chronic low back pain as well.201


Patient Beliefs About Pain and Pain Cognition. Beliefs about back pain can be highly individual and are often not based on facts. Some patients with back pain, espe-cially those with chronic low back pain that keeps them from working, have a great deal of fear about back pain. These include fears that their pain will be permanent, 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 low back pain who perform poorly on treadmill exercise tests,191 walk slower on treadmill tests,2 and perform more poorly on spinal isometric exercise testing3 were the ones with more anticipation of pain than those who did well on these tests. Fear-avoidance beliefs rather than actual pain during testing predicted their performance. Fear-avoidance levels explain self-reported disability and time off work more accurately than actual pain levels or medical diagno-sis does.127 This finding has led Waddell and other experts to state that the fear of pain may be more disabling than pain itself.234

A large, population-based study found that subjects with high levels of pain catastrophizing, characterized by exces-sively negative thoughts about pain and high fear of move-ment and injury or reinjury (kinesophobia), who had back pain at baseline were much more likely to have especially severe or disabling pain at follow-up evaluation compared with those who did not catastrophize. For those without back pain at the initial questionnaire, catastrophizers were more likely to have developed low back pain with disabil-ity at follow-up evaluation than noncatastrophizers.171 Thought processes, such as the presence of catastrophizing, are not limited to back pain and are often part of a larger pattern of relationships and thought processes.

Patients beliefs about pain and their approach to deal-ing with pain have been consistently found to affect out-comes. Fortunately, changes in these beliefs and cognitive patterns are possible. Multidisciplinary pain programs have proven effective in decreasing fear-avoidant beliefs and catastrophizing (see Chapter 42).205

These changes in beliefs can also improve function. For example, a study in which a group of patients with chronic low back pain underwent a cognitive behavioral treatment program found that, although there were not significant changes in pain intensity, those with reductions of fear-avoidance beliefs had significant reductions in disability. Changes in fear-avoidant beliefs accounted for 71% of the variance in reduction in disability in this study.252

Centralization and Pain

The experience of nociception is processed by the body in complex ways. The theory that pain is a simple loop from injury to perception of injury is much too simplistic. Pain processing begins in the spinal cord and continues exten-sively in the brain, and the ultimate pain that someone experiences is the sum of multiple descending and ascend-ing faciliatory and inhibitory pathways. Extensive evidence now supports the theory that persistent pain might be caused by central sensitization, which could help explain why often no pain generator is found in chronic low back pain.46

The History and Physical Examination of the Low Back

A complete history and physical examination is important in the evaluation of low back pain to determine the cause of the symptoms, rule out serious medical pathology, and determine whether further diagnostic evaluation is needed.

The HistoryAs with any pain history, features of back pain that should be explored include location; character; severity; timing, includ-ing onset, duration, and frequency; alleviating and aggra-vating factors; and associated signs and symptoms. Each of these features can assist the clinician in obtaining a diagnosis and prognosis and determining the appropriate treatment. The causes of back pain are often very difficult to determine. For as many as 85% of patients, no specific cause for back pain is found.50 One of the main purposes of the history is to rule out rare but serious causes of back pain. Elements of historical information that suggest a serious underlying con-dition as the cause of the pain such as cancer, infection, long tract signs, and fracture are called red flags (Box 40-2). When these are present, further workup is necessary (Table 40-1).

Children 55 years old

History of violent trauma Nonmechanical nature of pain (i.e., constant pain not

affected by movement, pain at night) History of cancer Systemic steroid use Drug abuse HIV infection or other immunocompromised patients Unintentional weight loss Systemically ill, particularly signs of infection such as fever

or night sweats Persisting severe restriction of motion or intense pain with

minimal motion Structural deformity Difficulty with micturition Loss of anal sphincter tone or fecal incontinence, saddle

anesthesia Progressive motor weakness or gait disturbance Marked morning stiffness Peripheral joint involvement Iritis, skin rashes, colitis, urethral discharge, or other

symptoms of rheumatologic disease Inflammatory disorder such as ankylosing spondylitis

suspected Family history of rheumatologic disease or structural

abnormality

BOX 40-2

Red Flags: Most Common Indications From History and Examination for Pathologic Findings Needing Special Attention and Sometimes Immediate Action (Including Imaging)

Modified 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.


Besides determining a diagnosis, a purpose of the history is to explore the patients perspective and ill-ness experience. Certain psychosocial factors are valu-able in determining prognosis (Box 40-3). Factors such as poor job satisfaction, catastrophic thinking patterns about pain, the presence of depression, and excessive rest or downtime are much more common in patients in whom back pain becomes disabling. These are called yellow flags because the clinician should proceed with caution, and further psychologic evaluation or treat-ment should be considered if they are present. Some of these psychosocial factors are addressed by specific ques-tions, and some become evident through statements that patients make during the history as they describe their illness experience. Questions about, for example, what patients believe is causing the pain, their fear and feel-ings surrounding this belief, their expectations about the pain and its treatment, and how back pain is affecting their lives (including work and home life) can yield valu-able information. Many of these yellow flags are better prognostic indicators than the more traditional medical diagnoses.235

The Physical ExaminationTable 40-2 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 40-13 and 40-14), 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 (Figure 40-15) are fully relaxed, pal-pation is often done with the patient lying prone, perhaps with a pillow under the abdomen to slightly flex the spine into a position of comfort. It should proceed systematically to determine what structures are tender to palpation.

Range of Motion

Quantity of Range of Motion. Several methods can be used to measure spinal range of motion (ROM). These include using a single or double inclinometer; measuring the distance of fingertips to floor; and, for forward flexion, the Schober test (measuring distraction between two marks on the skin during forward flexion). Of these methods, the double inclinometer has been shown to correlate the clos-est to measurements on radiographs.77,210 Fingertip to floor has good interrater and intrarater reliability, but this takes into account the movement of the pelvis and is affected by structures outside the spine, such as tight hamstrings.168 The Schober test is commonly used to assess a decrease in forward flexion in ankylosing spondylitis. It is sensitive for this condition but is not specific. General figures for nor-mal ROM are forward flexion, 40 to 60 degrees; extension, 20 to 35 degrees; lateral flexion, 15 to 20 degrees; and rota-tion, 3 to 18 degrees. Studies to determine normal ROM in asymptomatic adults have found large variations within the normal range.165 It is unclear what the significance of decreased ROM is in patients with back pain because many people without back pain also have limited range. ROM

Table 40-1 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 yr 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 mo 0.50 0.81

Failure to improve with 1 mo of conservative therapy

0.31 0.90

Erythrocyte sedimenta-tion rate >20 mm

0.78 0.67

Spinal infection

Intravenous drug abuse, urinary tract infec-tion, skin infection

0.4

Fever 0.27-0.83* 0.98

Vertebral tenderness Reasonable Low

Age >50 yr 0.84 0.61

Compression fracture

Age >70 yr 0.22 0.96

Corticosteroid use 0.66 0.99

Herniated interverte-bral 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.

Presence of catastrophic thinking: there is no way the patient can control the pain, that disaster will occur if the pain continues, etc.

Expectations that the pain will only worsen with work or activity

Behaviors such as avoidance of normal activity, and extended rest

Poor sleep Compensation issues Emotions such as stress and anxiety Work issues, such as poor job satisfaction and poor

relationship with supervisors Extended time off work

BOX 40-3

Some Common Yellow Flags Associated With the Development of Chronic Disabling Pain Suggesting Additional Attention May Be Necessary


can also change depending on the time of day, the effort the patient expends, and many other factors.255

Quality of Range of Motion. The examiner should record whether there are abnormalities in the patients movement pattern during ROM, such as a catch in the range or whether it causes pain. This might give clues to the diagno-sis. For example, pain with forward flexion can signify disk disease, and pain with extension can indicate spondylolis-thesis, zygapophyseal joint disease, or spinal stenosis.

The Neurologic Examination

The neurologic examination of the lower limbs can rule out clinically significant nerve root impingement and other neurologic causes of leg pain (Tables 40-3 and 40-4). The physical examination should logically proceed to discover whether a particular root level is affected by combining the findings of weakness, sensory loss, diminished or absent reflexes, and special tests such as straight leg-raising sign. Upper motor neuron abnormalities should also be ruled

out. The accuracy of the neurologic examination in diag-nosing herniated disk is moderate. The accuracy can be increased considerably, however, with combinations of find-ings.50 The sensitivity and specificity of different findings for lumbar radiculopathy have been well studied (Table 40-5).

Orthopedic Special Tests to Assess for Relative Strength and Flexibility

Back pain can be caused by deconditioning, poor endur-ance, and muscle imbalances. This makes it important to identify any inefficient or abnormal movement patterns of muscles that control the movement of the spine and the position of the pelvis.

Because of their stabilizing effect on the spine, abdomi-nal muscle strength and endurance is important. Several different ways can be used to measure abdominal muscle strength and control (Figures 40-16 and 40-17). One grad-ing system assesses whether the patient is able to maintain a neutral spine position while adding increasingly more challenging leg movements (Figure 40-18).

Table 40-2 Physical Examination for Low Back PainExamination 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 L1S1 myotomes Determine weakness

Pinprick and light touch sensation, L1S1 dermatomes

Determine sensory loss

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, maximus, etc.

Determines weakness and deconditioning

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


Besides determining the strength of the abdominals, strength testing of the back muscles and pelvic stabiliz-ers, such as the hip abductors, can be useful. Assessing for areas of relative inflexibility is also important. Com-monly performed tests are hip flexor flexibility, hamstring flexibility, other hip extensors length, and gastrocnemius/soleus length. Balance challenges, such as the ability to maintain single-footed stance, the ability to lunge or squat, and other functional tests are also helpful to determine a patients baseline status.

Orthopedic Special Tests for Lumbar Segmental Instability

Many clinicians and researchers believe that one cause of mechanical low back pain is segmental instability that responds to specific stabilization treatments. Therefore accu-rately identifying this group from other forms of low back pain could be important. These special tests include passive intervertebral motion testing and the prone instability test.

Passive Intervertebral Motion Testing. The patient lies prone. The examiner applies a firm steady pressure over the spinous process anteriorly and assesses the amount of vertebral motion and whether pain is provoked.90

Prone Instability Test. The patient lies prone, with the torso on the examining table and the legs over the edge of the table with the feet resting on the floor. The examiner performs passive intervertebral motion test-ing at each level and notes provocation of pain. Then the patient lifts the legs off the floor, and the painful levels are repeated. A positive test is when the pain dis-appears when the legs are lifted off the table. This is

because the extensors are able to stabilize the spine in this position.90,138

Examining the Area Above and Below the Lumbar Spine

Generally in musculoskeletal medicine, the joint above and the joint below the painful area should be assessed to make sure nothing is missed. This is a good idea for the examination of the lumbar spine as well. ROM of the hip joints should be assessed, and a quick screen of the knee and ankle joint can determine whether pathology in these areas is contributing to the back problem. The tho-racic spine can be quickly screened as well during ROM and palpation.

>3030


Illness Behavior and Nonorganic Signs Seen on Physical Examination

Multiple reasons can explain why patients with back pain might display symptoms out of proportion to injury. Ill-ness behaviors are learned behaviors and are responses that some patients use to convey their distress. Several stud-ies have found that patients with chronic low back pain and chronic pain syndrome experience significant anxiety during the physical examination, even to the level expe-rienced during panic attacks. This complicates the assess-ment by altering the clinical presentation of the condition. This anxiety is generally manifest as avoidance behavior, such as decreased ROM or poor effort with muscle test-ing.81 Other reasons for illness behavior include a desire to prove to physicians how disabling the pain is and malin-gering. One way to assess for illness behavior on physical

examination is to perform parts of the examination to search for Waddells signs. Waddells signs are forms of ill-ness behavior.234 They are nonorganic findings on physical examination that correlate with psychologic distress. They are as follows: Inappropriate tenderness that is widespread or

superficial Pain on testing that only simulates loading the spine,

such as light pressure applied to the top of the head, which reproduces back pain, or rotating the hips and shoulders together to simulate twisting without actu-ally moving the spine, which reproduces back pain

Inconsistent performance when testing the same thing in different positions, such as a difference in outcome of the straight leg-raising test with the patient supine versus sitting

Regional deficits in strength or sensation that do not have an anatomic basis

Overreaction during the physical examinationFindings in three of these five categories suggest psy-

chologic distress and also suggest that other parts of the physical exam that require patient effort or reporting of symptoms might be inaccurate.

Clinical Evaluation: Diagnostics

Imaging StudiesImaging of the lumbar spine should be used in the evalua-tion of low back pain if specific pathology needs to be con-firmed after a thorough history and physical examination.

Plain Radiography

Conventional radiographs are indicated in trauma to eval-uate for fracture and to look for bony lesions such as tumor when red flags are present in the history. As an initial screen-ing tool for lumbar spine pathology, however, they have very low sensitivity and specificity.73 Anteriorposterior and lateral views are the two commonly obtained views. Oblique views can be obtained to examine for a spondy-lolysis by visualizing the pars interarticularis and the Scot-tie dog appearance of the lumbar spine (Figure 40-19). Lateral flexionextension views are obtained to check for dynamic instability, although the literature does not sup-port their usefulness.55 They are potentially most helpful from a surgical screening perspective when evaluating a spondylolisthesis. They are commonly obtained in post-trauma and postsurgical patients.

Magnetic Resonance Imaging

MRI is the preeminent imaging method for evaluating degenerative disk disease, disk herniations, and radiculop-athy (Figure 40-20) (see also Chapter 7). On T2-weighted imaging, the annulus can be differentiated from the inter-nal nucleus, and annular tears can be seen as high-intensity zones. These zones are of unclear clinical significance but are thought to be potential pain generators.

Adding gadolinium contrast enhancement helps to identify structures with increased vascularity. Contrast is always indicated in evaluating for tumor or infection or to determine scar tissue (vascular) versus recurrent disk

Table 40-3 Factors That Affect PostureReason for Abnormality Clinical Example

Bone structure Compression fractures

Scheuermann disease

Ligamentous laxity Hyperextension of the knees, elbows

Muscle and fascial length Tight hamstrings that cause a posterior pelvic tilt

Weak and long abdominal muscles that allow an anterior pelvic tilt

Body habitus Obesity or pregnancy causes changes in force and increased lumbar lordosis

Neurologic disease Spasticity causes an extension pattern of the lower limb

Mood Depression causes forward slumped shoulders

Habit Long-distance cyclists have increased thoracic kyphosis and flat spine from prolonged positioning while riding

Erector spinaemuscles

Iliaccrest

L45 intervertebraljoint

Sacroiliac joint

FIGURE 40-15 Anatomy of the low back surface anatomy.


herniation (avascular) in postsurgical patients with recur-rent radicular symptoms.

The downside of MRI is that, although it is a very sen-sitive test, it is not very specific in determining a definite source of pain. It is well established that many people with-out back pain have degenerative changes, disk bulges, and protrusions on MRI. Boden et al.21 demonstrated that one third of 67 asymptomatic subjects were found to have a substantial abnormality on MRI of the lumbar spine. Of the subjects younger than 60 years, 20% had a disk hernia-tion, and 36% of those older than 60 had a disk herniation and 21% had spinal stenosis. Bulging and degenerative disks were even more commonly found. In another study

of lumbar MRI findings in people without back pain, Jen-sen et al.97 demonstrated that only 36% of 98 patients had normal disks. They found that bulges and protrusions were very common in asymptomatic subjects, but that extru-sions were not. In a more recent study in 2001, Jarvik con-firmed these findings.96

Computed Tomography

Because of the resolution of anatomic structures in MRI, it has essentially replaced computed tomography (CT) scanning as the imaging study of choice for low back pain and radiculopathy. CT scanning is still more useful than MRI, however, in evaluating bony lesions. CT scans are

Table 40-4 Lumbar Root Syndromes

Root Dermatome Muscle WeaknessReflexes or Special Tests Affected Paresthesias

L1 Back, over trochanter, groin None None Groin, after holding posture, which causes pain

L2 Back, front of thigh to knee Psoas, hip abductor None Occasionally front of thigh

L3 Back, upper buttock, front of thigh and knee, medial lower leg

Psoas, quadricepsthigh wasting Knee jerks sluggish, protein kinase B-positive, pain on full straight leg raise

Inner knee, anterior lower leg

L4 Inner buttock, outer thigh, inside of leg, dorsum of foot, big toe

Tibialis anterior, extensor hallucis

Straight leg raise limited, neck flexion pain, weak knee jerk, side flexion limited

Medial aspect of calf and ankle

L5 Buttock, back and side of thigh, lateral aspect of leg, dorsum of foot, inner half of sole, and first, second, and third toes

Extensor hallucis, peroneals, gluteus medius, ankle dorsiflexors, hamstringscalf wasting

Straight leg raise limited to one side, neck flexion pain, ankle jerk decreased, crossed leg-raising pain

Lateral aspect of leg, medial three toes

S1 Buttock, back of thigh, and lower leg Calf and hamstrings, wasting of gluteals, peroneals, plantar flexor

Straight leg raise limited Lateral two toes, lateral foot, lateral leg to knee, plantar aspect of foot

S2 Same as S1 Same as S1, except peroneals Same as S1 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: Harrisons principles of internal medicine, ed 15, New York, 2001, McGraw-Hill.

Table 40-5 Lumbosacral Radiculopathy in Patients With Sciatica*

Finding Sensitivity (%) Specificity (%)Positive Lumbrosacral Radiculopathy

Negative Lumbrosacral 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.NS, Not significant.*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 patients 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.


also useful in the postsurgical patient with excessive hard-ware that can obscure MRIs, and in patients with implants (aneurysm clips or pacemakers) that preclude MRI.

Myelography

In myelography, contrast dye is injected into the dural sac and plain radiographs are performed to produce images of the borders and contents of the dural sac (Figure 40-21). CT images can also be obtained after contrast injection to produce axial cross-sectional images of the spine that enhance the distinction between the dural sac and its sur-rounding structures. This is typically reserved as a potential presurgical screening tool but has been used less with the advancement of MRI.

Scintigraphy

Radionuclear bone scanning is a fairly sensitive but not specific imaging modality that can be used to detect occult fractures, bony metastases, and infections. To

increase anatomic specificity, single-photon emission computed tomography (SPECT) bone scanning is used to obtain bone scans with axial slices. This allows the diagnostician to differentiate uptake in the posterior ele-ments from more anterior structures of the spine. The diagnostic use of this study with regard to altering clini-cal decision-making is controversial. Studies have been published demonstrating that the use of SPECT can help identify patients with low back pain who might benefit from Z-joint injections.172

A

B

CFIGURE 40-16 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 states that the crucial point in the test 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 flex-ors 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 grade is the ability to begin flexion but not maintain spinal flexion with the forearms extended forward. (Modified from Kendall FP, McCreary EK: Trunk muscles in muscle testing and function, Philadelphia, 1983, Williams and Wilkins.)

90

75

60

45

30

15

0

50% 60%70%

80%

90%

100%

A

B

CFIGURE 40-17 Leg lowering: grading. In the second test, the patient raises the legs one at a time to a right angle, and then flattens them back on the table. The patient slowly lowers the legs while holding the back flat. A 100% 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 the low back flat. B, The pelvis tilted anteriorly and the low back arched as the legs were lowered. C, The final position. Kendall notes that this second test is more important than the first (see Figure 40-16) in grading muscles essential to proper posture, and that often patients who do 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, Williams and Wilkins.)


Electromyography

Electromyography is useful in evaluating radiculopathy because it provides a physiologic measure for detecting neurogenic changes and denervation with good sensitivity and high specificity. It can help to provide information as to which anatomic lesions found in imaging studies are

truly physiologically significant.181 See Chapters 9 through 11 for further details.

Laboratory StudiesBlood tests are rarely used in isolation as a diagnostic strat-egy for low back pain. Some blood tests are helpful as an adjunct in diagnosing inflammatory disease of the spine (with such markers of inflammation as sedimentation rates and C-reactive proteins), as well as some neoplastic disorders, such as multiple myeloma with a serum protein electrophoresis and urine protein electrophoresis.

Differential Diagnosis and Treatment: The Prototype of Back Pain Greater Than Leg Pain

Mechanical Low Back PainNearly 85% of those who seek medical care for low back pain do not receive a specific diagnosis.50 The majority of these patients most probably have a multifactorial cause for back pain, which includes deconditioning; poor muscle

A

B C

D EFIGURE 40-18 Abdominal strength grading. A, The patient lies supine with the knees bent (supine crook 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, while 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.

Superior articular process(ear of Scottie dog)

Transverse process(nose)

Pedicle(eye)

Defect at pars interarticularis(collar or broken neck)

Inferior articular process(foot)

FIGURE 40-19 Oblique drawing of the lumbosacral junction, outlining the Scottie dog and the area of spondylolysis.


recruitment; emotional stress; and changes associated with aging and injury such as disk degeneration, arthritis, and ligamentous hypertrophy. This type of back pain can be given many names; simple backache, nonspecific low back pain, lumbar strain, and spinal degeneration are a few of the common names for this condition. The name given to a condition sends certain messages to the patient who receives the diagnosis. The term simple backache might cause a patient to think that the physician misunderstands because, from the patients perspective, the pain is not simple if it has not resolved in a few days. The label non-specific low back pain can cause the patient to continue to seek care from multiple providers to receive a specific diag-nosis. Lumbar strain suggests that the condition was caused by overactivity, which is often not the case, and that further physical activity would cause it to recur, which is not true. Spinal degeneration sends the message that the changes are permanent and will probably worsen.235 The term mechani-cal low back pain is perhaps the best term for this multifac-torial axial backache. It suggests the mechanism of injury better than terms such as strain or sprain, and it does not imply permanence.

The biomechanics of the spine are not unlike the bio-mechanics of other systems, in that longevity of the com-ponents and efficiency of the system depend on precise

movements of each segment. In the spine, this means both an alignment in sustained postures and movement pat-terns that reduce tissue strain and allow for efficient muscle action without trauma to the joints or soft tissue.189 Clini-cians and researchers alike theorize that when alignment and movement patterns deviate from the ideal, degenera-tion and tissue overload is more likely. This is analogous to the abnormal tire wear that occurs on a car when the wheels are out of alignment. Unlike machinery, the body can adapt over the course of time to stress on the segments. This adaptation can be the healthy response of tissue to loading (as is seen with exercise), such as muscle hypertrophy or increased bone density. It can also, however, begin a cycle of microtrauma that can lead to macrotrauma.125,140,189 The theoretic model for this approach is strong, and research is beginning to validate many of these concepts, although this is not easy given the complex nature of the system.

History, Physical Examination, and Diagnostic Tests in Mechanical Low Back Pain

The history and physical examination in mechanical low back pain are variable. No specific diagnostic tests exist for mechanical low back pain. Tests and imaging are used to exclude other diagnoses.

Treatment of Low Back Pain

Most studies of the various treatments for low back pain, particularly chronic low back pain, unfortunately have shown limited efficacy. Even the most commonly pre-scribed treatments, such as medications, exercise, and manipulation, in large trials tend to show improvements of only 10 to 20 points on a 100-point pain visual ana-logue scale. For this reason, most clinicians use multiple treatments on a particular patient in the hope that their cumulative effect will provide sufficient pain relief and an improvement in symptoms. The most common treatments for low back pain are discussed below.

Reassurance and Patient Education. Education should include providing as much of an explanation as patients need in terms they can understand. The physician should also provide empathy and support and impart a positive

A B CFIGURE 40-20 Disk extrusion in a 48-year-old woman with back and left leg pain. A and B, Sagittal T2- and T1-weighted magnetic resonance image (MRI) showing L5S1 disk extrusion with caudal extension. C, Axial T2-weighted MRI showing the extrusion is left paracentral in the lateral recess, occupying the space where the S1 root resides.

A B

FIGURE 40-21 Anteroposterior (A) and lateral (B) myelograms of a 59-year-old woman with severe L4L5 central stenosis caused by a large left L4L5 zygapophyseal joint synovial cyst. Note the obvious filling defect at the L4L5 level. She had symptoms of cauda equina syndrome and regained full neurologic function after decompression surgery.


message. Reassurance that there is no serious underlying pathology, that the prognosis is good, and that the patient can stay active and get on with life despite the pain can help counter negative thoughts and misinformation that the patient might have about back pain.235

Strong evidence from systematic reviews indicates that the advice to continue ordinary activity as normally as pos-sible fosters faster recovery and can lead to less disability than the advice to rest and let pain be your guide.236 It is controversial whether patients with low back pain fare bet-ter with a specific diagnosis or not. Education and explana-tions, however, should be adequate. As Waddell states in his book The Back Pain Revolution, Simply saying that I cant find anything wrong might imply that you are not sure and make patients worry more!235 On the other hand, some diagnoses carry negative messages to patients that suggest permanent damage and the need to get fixed, such as degenerative disk disease or arthritis.235 Mechanical low back pain is a useful diagnostic term because it implies the mechanism of the pain and the way it is best treated without suggesting permanence.

Beyond a diagnosis, there is other information that patients want about low back pain. In a study of patients who presented with low back pain to their primary care doctors in a health maintenance organization setting, the information that patients wanted from their doctor included the likely course of their back pain, how to man-age their pain, how to return to usual activity quickly, and how to minimize the frequency and severity of recurrences. They ranked each of these areas of education a higher pri-ority than finding a cause or receiving a diagnosis for their pain.235 Providing this information in an amount and in a way that patients can understand helps build a therapeutic doctorpatient relationship and, it is hoped, helps reduce anxiety and speed recovery.

Back Schools. The term back school is generally used for group classes that provide education about back pain. The content and length of these classes varies a great deal, but generally they include information about the anatomy and function of the spine, common sources of low back pain, proper lifting technique and ergonomic training, and sometimes advice about exercise and remaining active. Studies have generally found back schools to be effective in reducing disability and pain for those with chronic low back pain.224

Exercise. No well-controlled studies show that exercise is effective for the treatment of acute low back pain. Many practitioners believe that exercise for patients with acute low back pain is appropriate to prevent deconditioning, to reduce the chance of recurrence of symptoms, and to reduce the risk of the development of chronic pain and dis-ability. This is consistent with rehabilitation principles for other acute injuries, such as sports-related injuries or reha-bilitation after joint replacement surgery.239 This principle is not yet supported by scientific research, perhaps because of problems with long-term exercise compliance, the over-all favorable prognosis for each episode of acute back pain, or the outcome measures used.

Multiple high-quality studies have found, however, that exercise results in positive outcomes in the treatment of

chronic low back pain.226 This includes pain relief (although this relief is modest, with a recent metaanalysis of 43 tri-als showing a mean difference of 10 points on a 100-point scale), improvement in function, and slightly reduced sick leave.43,87 It appears that the most effective exercise for low back pain includes an individualized regimen learned and performed under supervision that includes stretching and strengthening.87 This is not surprising because it is gener-ally believed that the purpose of exercises for the treatment of low back pain is to strengthen and increase endurance of muscles that support the spine and improve flexibility in areas where this is lacking. This is combined with motor retraining to establish normal patterns of muscle activity, and treatment of deficits of the kinetic chain that interfere with biomechanical efficiency. One reason that studies have not been able to determine what exercises are best for patients with low back pain could be that multiple forms of exercise can achieve the goal of restoring function and regaining physical fitness.116,225,239

The exact dose of exercise, how much exercises should be advanced, and the ideal length of supervised treatment is not known. Because endurance is a significant problem with many patients with persistent back pain, activity lev-els should be increased in planned, fixed increments based on realistic goals rather than on symptoms. This is because it is normal in the course of low back pain that there will be temporary exacerbations of pain along the way. Beyond the physiologic benefits of exercise, increasing activity has positive effects on beliefs and behaviors about pain. Small doses of exercise that are not sufficient to cause physi-ologic change have been found to increase function and decrease pain. When specifically studied, this appeared to be from decreased fear-avoidance beliefs and reduced anxiety. By exposing fearful patients to physical activity through gradually increasing activity levels despite pain, they receive positive reinforcement by meeting goals, and personal experience can reduce fear of movement, reinjury, and catastrophizing.22 Adverse effects of exercise for low back pain are rarely reported, so it is generally a very safe form of treatment.

Specific Exercise Treatment for Low Back Pain. Exercise prescriptions for mechanical low back pain generally begin with the goal of improving alignment and posture. Although researchers have not been able to consistently identify which specific postural faults are associated with chronic low back pain,56 the correction of posture could be important for at least two reasons. One is that exercises are more effective if they are done from a position of proper alignment that promotes optimal joint function and move-ment patterns. The second is that, for virtually all patients, much more time will be spent in habitual postures such as sitting and standing than will ever be spent exercising. If these habitual postures can reduce abnormal tissue strains, there is a better chance of reducing pain and promoting healing.188

Research on measuring posture, especially in regard to what is normal posture and whether exercise can influ-ence posture, is difficult to conduct, and there are few stud-ies to guide us in this area. In general, posture is evaluated in both sitting and standing positions, and an attempt to correct faulty posture is made. Some of these postural faults


are habitual and can be improved with education, cuing, and practice. Some postural faults are structural problems that do not change with exercise, such as the kyphosis of Scheuermann disease or idiopathic scoliosis, and should be addressed with aids such as higher armrests or a chair with increased lumbar support. Many postural faults begin as habitual, and then become structural as tight muscles and tendons do not allow immediate correction with cuing, and weak muscles cannot maintain the proper posi-tion even if it can be reached. This is what is seen with typi-cal postural faults such as long-standing lordosis, in which hip flexors and lumbar paraspinals become tight from pro-longed positioning in lordosis, and abdominal muscles become long and weak from disuse and their prolonged lengthened position.

These types of faults can be addressed with the proper exercises to stretch tight areas and strengthen weak areas. This is harder, however, to achieve in patients with persis-tent back pain. Multiple studies have shown that subjects with chronic low back pain have deficits in spinal proprio-ception and make repositioning errors. For example, in a study in which asymptomatic patients were compared with patients with chronic low back pain in an activity in which participants were assisted into neutral spine posture and then asked to reproduce this position after periods of relaxed full lumbar flexion, the group with back pain had significantly more repositioning errors.157 This has impor-tant implications for treatment because those with back pain might need extensive training by a physical therapist to change their posture, rather than just education regard-ing posture or a few simple demonstrations.

Lumbar stabilization and core strengthening exercises that strengthen the muscles that support the spine are the most common exercises used to treat low back pain. A wide range of exercises can be used to strengthen these tissues. Because of research that shows that the deep stabi-lizers, such as the multifidi and transversus abdominus, do not function as well in those with low back pain, some pro-grams emphasize beginning training of these muscles in the treatment of low back pain. Typically the exercise pro-gram is then progressed to include more complex dynamic and functional tasks. These are sometimes called motor control exercises because of the emphasis on precision of movement, rather than simply gaining global strength or flexibility. Multiple randomized controlled trials have shown that lumbar stabilization exercises, core strengthen-ing, and motor control exercises are beneficial in reducing pain and improving function in patients with persistent low back pain. It is not clear whether these types of exer-cises are superior to other types.121

Modifications for Those in Whom Exercises Aggravate Pain. McGill138 has done extensive research evaluating spi-nal forces generated during exercise. For example, sit-ups cause more than 3000 N of compressive loads on the spine because of psoas activity, about the same as moderately heavy lifting. Leg raises also cause relatively high compres-sive forces. Curl-ups cause lower forces on the spine, so they are a better choice for anterior abdominal strengthening in the early stages of rehabilitation, or in those who have increased pain and cannot tolerate exercises with increased spinal loading. Lying prone and extending the spine while

extending the arms and legs causes more than 6000 N of compression to the spine and might be much too intense for those with back injuries. The quadruped position with the leg extended, however, also activates spinal extensors but causes less than half the amount of spinal compression if done properly with the abdominal muscles engaged and the spine in neutral.138 These examples show how modi-fication of exercises can reduce spinal forces and increase exercise tolerance.

Some patients, especially those with persistent pain, can have high fear-avoidant behavior and develop kinesopho-bia (a fear of movement and a belief that movement will increase pain or cause them to be injured). This fear of pain, rather than forces on the spine or spinal pathology, leads to poor exercise tolerance. If this is the reason for poor exer-cise tolerance, it can be addressed by graded reactivation and gradual increases in activity. A positive experience with this might decrease fears. For more severe cases, a multidis-ciplinary approach that includes psychologic counseling to explore these dysfunctional thought processes might be needed. The physician should emphasize to patients that exercise needs to become a daily habit. Lack of compliance is one of the main reasons why exercise treatments fail. The health benefits of the exercise program beyond pain relief should be discussed, and patients should be reminded that exercising needs to continue even after symptoms decrease or resolve.

Flexion Exercises for Low Back Pain. Once popular for the treatment of acute low back pain, using a series of flex-ion exercises has not been found to be more helpful for acute low back pain than other interventions, such as spi-nal manipulation, in several studies. No research has been done on the effectiveness of flexion exercises for chronic low back pain.223

Extension Exercises for Low Back Pain. Still commonly used by therapists in the treatment of low back pain, and in particular back pain accompanied by radicular leg pain, extension-based exercises are often done using the prin-ciples of the McKenzie method of physical therapy. This therapy approach divides the diagnosis for back pain into three categories: derangement, dysfunction, and postural syndrome. The most common of these are derangements, and exercises are chosen that centralize the pain, that is, move the pain from the leg or buttock into the low back. Although early studies were very promising, later studies have found this type of physical therapy to be helpful for low back pain but no more effective than other types of exercise.40,223

Aerobic Activity. Increasing aerobic activity is a corner-stone of most exercise programs for low back pain. Studies in this area are often difficult to interpret because, both in the clinical and research settings, aerobic activity is usually combined with strengthening and flexibility exercise. Stud-ies have shown that group classes that combine low-impact aerobics with strengthening and stretching floor exercises can be as effective in reducing pain and decreasing dis-ability as individualized physical therapy and strengthen-ing with weight machines.128 Many clinicians have found that patients with chronic low back pain tend to have very


low fitness levels, but research in this area has had conflict-ing results. For example, in one study in which prediction equations to estimated VO2max (a measure of aerobic fit-ness) in patients with chronic low back pain were com-pared with normal values, the values for chronic low back pain patients did not differ from age-matched normal values for sedentary men and women.250,251 This could be because those who agreed to participate in the study were not representative of all patients with chronic low back pain, or it might simply demonstrate the poor aerobic fit-ness of sedentary people in general. Perhaps this poor fit-ness level is related more to lifestyle than to back pain.

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