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But only a few treatments would be required. Manipulation of the neck as a treatment for low-back pain—or when there are no neck-related symptoms—is a useless and unscientific procedure that poses unnecessary risk to sensitive joints and blood vessels in the neck. Common sense, as exercised in this case, will often raise questions about treatment methods that are unnecessary or inappropriate.

Homola is a second-generation chiropractor who has dedicated himself to defining the proper limits on chiropractic and to educating consumers and professionals about the field. His book Bonesetting, Chiropractic, and Cultism supported the appropriate use of spinal manipulation but renounced chiropractic dogma. His book Inside Chiropractic: A Patient's Guide provides an incisive look at chiropractic's history, benefits, and shortcomings.

Now retired after 43 years of practice, he lives in Panama City, Florida. Samuel Homola, D. Question About years ago, I had lower back pain on the right side, possibly related to being thrown from horse rides, twice. Several questions occur to me now: Was the relief and cure I experienced real, or was it something that I just outgrew? Do you have a comment on this modality of treatment? Would you describe reasons and appropriate modalities for atlas adjustments? Answer The atlas is the highest spinal bone in the neck and has no connection to any structure that could cause back pain.

The laminae extend posteriorly from the left and right articular pillars and join to form the spinous process. Two adjacent vertebrae connect with each other by means of the facet joints on either side. This leaves a space between the bodies of the vertebrae which is filled with the intervertebral disc.

The intervertebral foramen for the exiting nerve root is formed by the space between the adjacent pedicles, facet joints and the vertebral body and disc. The integrity of the nerve root canal is therefore dependent on the integrity of the facet joints, the articular pillars, the vertebral body endplates and the intervertebral disc.

The body of the vertebra is connected to the articular pillars by the pedicles. The superior and inferior articular facets extend from the articular pillars to connect with the corresponding facets of the vertebrae above and below, to make up the posterior facets. The lateral transverse processes and the posterior spinous process form the attachments for paraspinal ligaments and muscles. It is attached to the vertebral bodies above and below the disc by the superior and inferior endplates. The nucleus pulposus is a gel-like substance made up of a meshwork of collagen fibrils suspended in a mucopolysaccharide base.

It has a high water content in young individuals, which gradually diminishes with degenerative changes and with the natural aging process. The fibers of adjacent lamellae have similar arrangements, but run in opposite directions. The fibers of the outer annulus lamella attach to the vertebral body and mingle with the periosteal fibers. The fibrocartilaginous endplates are made up of hyaline cartilage and attach to the subchondral bone plate of the vertebral bodies.

There are multiple small vascular perforations in the endplate, which allow nutrition to pass to the disc. The integrity of the inner aspects of the disc is best visualized by injecting a radio-opaque agent into the disc. This material disperses within the nucleus and can be visualized radiologically as a discogram. The facet joints connect the superior facet of a vertebra to the inferior facet of the adjacent vertebra on each side and are typical synovial joints.

The articular surfaces are made of hyaline cartilage which is thicker in the center of the facet and thinner at the edges. A circumferential fibrous capsule, which is continuous with the ligamentum flavum ventrally, joins the two facet surfaces. Fibroadipose vascular tissue extends into the joint space from the capsule, particularly at the proximal and distal poles.

This tissue has been referred to as a meniscoid which can become entrapped between the facets. The posterior facets can be seen on X-ray but only to a limited extent. Degenerative changes and hypertrophy of the facets can be visualized to a greater extent on CT and MRI. Radio-opaque dye can also be injected into the joint and the distribution of the dye measured. The space between the vertebral bodies is the location of the cartilaginous intervertebral disc.

The posterior facets are visible. The central canal is smaller than usual for this vertebral level. None of the discs were painful during injection. There is normal contrast dispersal in the nuclear compartment at each level Figure 2. The most important ligament from a clinical perspective is the posterior longitudinal ligament, which connects to the vertebral bodies and posterior aspect of the vertebral disc and forms the anterior wall of the spinal canal. The ligamentum flavum, which has a higher elastin content, attaches between the lamina of the vertebra and extends into the anterior capsule of the zygapophyseal joints; it attaches to the pedicles above and below, forming the posterior wall of the vertebral canal and part of the roof of the lateral foramina through which the nerve roots pass.

There are also dense fibrous ligaments connecting the spinous processes and the transverse processes, as well as a number of ligaments attaching the lower lumbar vertebrae to the sacrum and pelvis. The musculature of the spine is similar in microscopic structures to that of other skeletal muscles. The individual muscle cells have small peripherally located nuclei and are filled with the contractile proteins, actin and myosin. The actin and myosin form cross-striations, which are easily visualized on light microscopy of longitudinal sections of muscle.

The sarcomeres formed by the actin and myosin fibrils are separated by Z-lines, to which the actin is attached, and are visible on electron microscopy. The nuclei of the muscle cells are thin, elongated and arranged along the periphery of the cells. The muscles of the back are arranged in three layers. The most superficial, or outer layer, is made up of large fleshy erector spinae muscles, which attach to the iliac and sacral crests inferiorly and to the spinous processes throughout the spine. In the lower lumbar region, it is a single muscle, but it divides into three distinct columns of muscles, separated by fibrous tissue.

Below the erector spinae muscles is an intermediate muscle group, made up of three layers that collectively form the multifidus muscle. These muscles originate from the sacrum and the mamillary processes that expand backwards from the lumbar pedicles. They extend cranially and medially to insert into the lamina and adjacent spinous processes, one, two or three levels above their origin. The deep muscular layer consists of small muscles arranged from one level to another between the spinous processes, transverse processes and mamillary processes and the lamina.

In the lumbar spine, there are also large anterior and lateral muscles including the quadratus lumborum, psoas and iliacus muscles which attach to the anterior vertebral bodies and transverse processes. The spinal cord projects distally through the spinal canal from the brain, to taper out at the lower first or upper second lumbar vertebral level.

The lower level of the spinal cord is known as the conus medullaris, from which nerve roots descend through the spinal canal to their respective exit points. The spinal cord is ensheathed Figure 2. Note the small peripheral nuclei situated at the periphery of the muscle cells Courtesy ChurchillLivingstone Saunders Press Light microscopy. Note the cross-striations and thin dark nuclei arranged along the periphery of the muscle cells. Courtesy Churchill-Livingstone Saunders Press by the three layers of the meninges. The pia mater invests the conus medullaris and rootlets. The outer layer, or dura mater, is separated by a potential subdural space to the arachnoid meninges.

The subarachnoid space, which separates it from the pia mater, is filled with cerebrospinal fluid, which circulates up and down the spinal canal. The dura mater and pia mater continue distally, ensheathing the spinal nerves to the exit points. The spinal nerves exit the spinal cord by two nerve roots. The ventral nerve root carries motor fibers which originate in the anterior horn of the spinal cord.

These neurons receive direct input from motor centers in the brain and, in turn, innervate the body musculature. The sensory or dorsal nerve root carries impulses from sensory receptors in the skin, muscles and other tissues of the body to the spinal cord and from there to the brain. The cell bodies of these sensory neurons are located within the dorsal root ganglia, which can be seen as an expansion within the dorsal root.

The ventral and dorsal roots join to form the spinal nerve which exits the spinal canal and immediately divides into an anterior and posterior primary division. The posterior primary division, or ramus, of the nerve root innervates the facet joints and the posterior musculature, as well as the major posterior ligaments. Courtesy Churchill-Livingstone Saunders Press sends nerve fibers via the gray ramus communicans to the sympathetic ganglion chain.

A small sinuvertebral, or recurrent nerve of Von Luschka, branches from the mixed spinal nerve to innervate the posterior longitudinal ligament. The anterior primary division then travels laterally or inferiorly, depending on the vertebral level, to form the various plexuses and nerves that innervate muscles Figure 2.

Low Back Pain

The Z-lines and muscle filaments are evident. Mitochondria can be seen in the septa between the muscle fibers. The dorsal root ganglion of the exiting L5 nerve root is seen arrow. The posterior paraspinal muscles are seen: multifidus, longissimus thoracis pars lumborum, and iliocostalis lumborum pars lumborum arrows.

The psoas muscle is demonstrated at the anterolateral aspect of the vertebra throughout the body. Inflammatory processes occurring within the disc activate nociceptive nerve endings which send impulses via the sinu-vertebral nerve and gray ramus communicans nerve to the spinal cord. The multifidus m , longissimus thoracis pars lumborum l , and iliocostalis i , and gluteus maximum g are seen. The sacroiliac joints are visible s Figure 2.

The rootlets of the cauda equina are seen in the posterior thecal sac, with the sacral rootlets more posterior in position, and the L5 rootlets positioned laterally. The basivertebral vein complex entry into the L4 vertebra arrows and the venous channels are visible nociceptive fibers which travel within the dorsal primary division of the spinal nerve. Injury or entrapment of the neural elements of the spine can result in loss of function of a single motor or sensory nerve root, if the entrapment is within the neural foramen.

If the entrapment is due to stenosis or narrowing of the central canal, function within the cauda equina or spinal cord can be affected. Injury to the spinal cord can impact on the reflex centers or the sensory and motor pathways to the central control centers in the brain.

The spinal cord and the nerve roots in the cauda equina can also be visualized using these imaging techniques. The nerve roots, as they exit through the foramen, can be best seen on MRI scan and the size of the nerve root canal, which has the potential to entrap these nerves, can be measured. There is, however, marked variation in the size of the central canal and lateral foramina through which the spinal cord and nerve roots pass.

The simple measurement Figure 2. The latency represents the time it takes for nerve impulses to travel from the point of stimulation to the spinal cord. The nerve impulses travel through the spinal cord and connect with a Renshaw interneuron to send impulses back along the motor nerve to the distal muscles. The proximal conduction time represents the time it takes for nerve impulses to travel from the point of stimulation to the spinal cord and back to the point of stimulation.

Any entrapment or injury to the nerve root or sciatic nerve will prolong the latency of the response Figure 2. The peripheral nerves receive input from multiple nerve roots. This diagram illustrates the response on stimulation of the posterior tibial nerve at the ankle.

Low Back Pain – Causes, Diagnosis and Treatment

It is often possible to record a response over the lumbar spine as well as the scalp. The difference in latency between the spinal response and the cortical response is known as the central conduction time CCT , and represents the time that an impulse requires to travel from the spinal cord to the brain Figure 2. In order to achieve this, it is necessary to conduct a clinical examination and, where necessary, electrodiagnostic studies.

The diagnostic field known as clinical neurophysiology encompasses a series of testing procedures used to detect and quantify nerve function. The primary electrodiagnostic study utilized to document nerve root entrapment or injury is electromyography, where a needle is inserted into the muscle and the presence of denervation of the muscle can be documented.

Nerve root compression results in irritability of the cell membranes of a muscle. This can be noted on electromyography as short fibrillation potentials and positive sharp waves, which are not seen in normally innervated muscles. Within a few months following denervation, the remaining intact nerves begin to sprout collateral nerve fibers to innervate those muscles that have lost their nerve supply. This process results in a change in the appearance of the normal muscle activity seen on electromyography, which takes on a polyphasic appearance.

S1 nerve root function can also be determined by measuring neural reflexes, which travel to the spinal cord on stimulation of the sciatic nerve in the popliteal fossa, and by recording the motor response generated from these H-reflexes in the gastrocnemius muscles. The F-response is another method of measuring the motor pathway in the nerve roots which travels from a point of stimulation over a peripheral nerve to the spinal cord and back to the muscle. The documentation of nerve pathways within the spinal cord is achieved by stimulating a peripheral sensory nerve and recording electrical responses, using computer averaging over the spine and over the brain.

Education and the Prevalence of Pain

Delay or absence of these somatosensory evoked responses or potentials is strongly suggestive of a lesion impacting on the sensory pathways within the spinal cord. The differentiation of peripheral nerve lesions or injury distal to the nerve root is achieved by measuring nerve conduction in peripheral nerves. Direct measurement of bladder function using cystometry, bowel function using colonometry and male sexual function using nocturnal penile tumescence and rigidity may also be of value if it is suspected that these functions are being affected by lesions in the cauda equina or spinal cord.

The innervation of the lumbar spine. Clinical Anatomy of the Lumbar Spine, 2nd edn. Clinical neurophysiology and electrodiagnostic testing in low back pain. The Lumbar Spine, Vol 1, 2nd edn. The process of degenerative change occurs in the entire population as it ages and is probably part of the normal aging process. Even the most severe degenerative changes can occur in the absence of symptomatology, but back pain is more common in individuals who demonstrate these degenerative changes. It appears that the degenerative changes in the spine make one more vulnerable to the inflammatory effects of trauma.

Degenerative changes are most evident in the intervertebral discs and the facet joints, usually at the same time, but often to varying degrees. Figure 3. These annular tears increase in size and coalesce to form radial fissures. The radial fissures then expand and extend into the nucleus pulposus, disrupting the disc structure internally. This represents stage one of the degenerative process in the discs. The posterior facets are enlarged and the facets show degenerative changes.

This demonstrates the interaction between the discs and the posterior joints. Courtesy Churchill-Livingstone Saunders Press of the disc. As degeneration continues, the disc collapses, shortening the distance between the two vertebral bodies. This re-absorption can progress to the point where the vertebral bodies are eventually separated only by dense sclerotic fibrous tissue which is all that remains of the original disc structure.

At the same time as the disc is being reabsorbed, the vertebral bodies on either side of the disc become dense and sclerotic. Osteophytes extend from the vertebral bodies around its circumference, presumably in an attempt to stabilize the three-joint complex and reduce motion. Occasionally, the osteophytes may join and fuse, resulting in bony ankylosis of the joint. The extensive degenerative changes in the posterior joints have resulted in enlargement of the facets. On the left side of the disc near the back of the vertebral body, there is a small circumferential tear in the annulus fibrosus.

This tear has enlarged and spread to the center of the disc. Courtesy Churchill-Livingstone Saunders Press can lead to the formation of a synovial fold, projecting into the joint between the cartilage surfaces. There is gradual thinning of the cartilage, which starts in the periphery with progressive loss of cartilage tissue. Subperiosteal osteophytes begin to form which enlarge both the inferior and superior facets.

This breakdown continues until there is almost total loss of articular cartilage with marked periarticular fibrosis and the formation of subperiosteal new bone expanding the volume of the superior and inferior facets. During the early phases of these degenerative changes, the facet capsule can become very lax, allowing increased movement. It is probably this period of increased mobility of the joint which leads to further degeneration within the posterior facets, and puts further stress on the intervertebral discs.

There is complete disintegration of the nucleus pulposus.

Common Causes of Low Back Pain

These changes have resulted in instability of the three-joint complex at this level. The lumbar spine is markedly unstable at this level. The thickened annulus fibrosus is bulging around the circumference of the disc with resultant stenosis and narrowing of the spinal canal long arrow. There is almost complete resorption of the disc which is seen as a small slit between the vertebral bodies.

There is sclerosis of the bone in the vertebral bodies on either side of the disc. Courtesy Churchill-Livingstone Saunders Press Longitudinal sagittal section of the lumbar spine showing marked degeneration at four levels. There is disintegration of the L3—L4 and L4—L5 discs. At the L5—S1 level, there is disc resorption, with sclerotic bone on either side of the remnants of the disc. T2 weighted MR images of the lumbar spine measure the hydration status of the disc, which gradually decreases in the presence of degenerative changes. This results in a change in the signal intensity within the disc, which is easily seen.

Radial and circumferential tears can also be visualized on MR images. On CT scan imaging, gas formation can be seen within the radial tears and the annulus during the reabsorption phase. Sclerotic changes within the facet joints can also be noted on standard X-rays. Better visualization of these changes is achieved by means of CT scan or MR images, which can document the growth of osteophytic spurs and determine whether they encroach on the spinal canal or neuroforamina. The intervertebral disc has lost height, and there is gas in the disc space which appears black on CT images arrow.

On the axial image, there is lateral protrusion of the disc margin to the left Figure 3. The Knuttson gas phenomenon is present at L4—L5 arrow , indicative of advanced degeneration of the L4—L5 disc. The purple-staining articular cartilage represents normal cartilage. The arrow points to a thin sausage-shaped tag of synovial tissue lying between the articular surfaces. The arrow points to thin degenerate cartilage on the upper part of the joint.

A large thick fibrofatty tag extends from the joint capsule on the right, lying between the two purple articular surfaces. There is thinning of the articular cartilage on the lower joint surface, with a large space between the joint capsule and the articular surfaces. This is indicative of a lax capsule and an unstable joint. The joint is almost obliterated and there is cartilagineous fusion of the two facets of the joint. The arrow points to the remnants of the joint space. This type of change occurs when there has been immobilization of the joint for prolonged periods.

The two surfaces of the articular cartilage have slid past each other, resulting in subluxation of the joint. On the left side, a fibrofatty tag of synovium attached to the joint capsule extends into the joint arrow. The purple articular cartilage on both sides of the joint is very thin and fragmented. The arrows point to the grossly thickened capsule on both sides of the joint. The intervertebral foramen large arrow is much reduced in size as the result of impingement by an enlarged superior articular process of the facet of L5 small arrow.

There is entrapment of the synovium within the joint left arrow. The breakdown in the disc is evident right arrow with bulging posteriorly. The spinal canal is narrowed due to the combined effects of the joint hypertrophy and the bulging disc. Imaging of degenerative disease of the lumbar spine and related conditions. Using computed tomography and enhanced magnetic resonance imaging to distinguish between scar tissue and recurrent lumbar disc herniation. Pathology and pathogenesis of lumbar spondylosis. Degenerative disk disease: assessment of changes in vertebral body marrow with MR imaging.

Annular tears and disc degeneration in the lumbar spine. Anatomy of facet joints and its clinical correlation with low back pain. Contemp Orthop ; 4 Acute trauma Acute trauma, either in the form of a direct blow to the spine or the application of excessive rotational or compressive force applied to the spine, can result in injury to virtually any structure. The structures most vulnerable to acute trauma are the annulus fibrosus of the intervertebral discs, the endplates of the intervertebral discs and the vertebral bodies.

If these tears are oriented in a radial fashion, the nucleus pulposus may migrate through the tear, causing a protrusion of the disc beyond its natural borders. This can occur as an acute process in a healthy disc given sufficient force. Degenerated discs that already have some degree of annular tearing, usually in a circumferential pattern, have less elastic proteoglycans and are less able to withstand these forces.

If there is a disruption of the posterior longitudinal ligament, nuclear material can extrude through the annulus, narrowing the diameter of the Figure 4. The disc protrusion effaces the dorsal root ganglion arrow ; b nonenhanced computed tomography of the same patient reveals increased signal density of the lateral disc herniation; c postdiscography computed tomography of the same patient demonstrates contrast enhancement of the lateral disc herniation arrow Figure 4. Note that the posterior longitudinal ligament has been elevated posteriorly and separated by the disc herniation.

Note the relationship between the normal-appearing nerve roots at L2 and L3 and the pedicle. The attachment of the longissimus thoracic pars lumborum to the transverse process is seen in the posterior paraspinal muscle compartment Figure 4. The posterior facets show degenerative changes in the form of irregular surfaces small arrow. If the disc herniation protrudes posteriorly in the midline to narrow the central canal of the spine, compression of the cauda equina or spinal cord can occur.

If the disc protrudes laterally, it can extend into the lateral foramina, encroaching on the nerve root. As a result of compression forces, the endplate of the vertebral body may collapse, allowing herniation of the nucleus pulposus into the vertebral body.

Bony fractures of the vertebral body are well visualized on X-ray and the edema associated with healing is visible on MRI scan. Radial tears and the protrusion of the nucleus into the tear can be visualized by injecting a radio-opaque dye into the disc, which can be visualized on X-ray as a discogram. These changes are more clearly seen on post-discography CT scanning. There is a disruption of the intrinsic bone structure, followed by edema and healing of the bone. If severe, these compression fractures can force spicules of bone or the entire vertebral body to move posteriorly, encroaching on the central canal or laterally encroaching on the neuroforamen.

There is a compression fracture of L5 with posterior displacement of the fractured bone, leading to marked narrowing of the central canal arrow. Muscles with intact nerve supply are normally silent at rest. The middle line of potentials b can be seen as a result of reinnervation of the nerve to the previously denervated muscle. The lower line of potentials c shows the response seen in a partially denervated muscle on voluntary contraction of the muscle. The polyphasic potentials differ from the normal potentials recorded from the normal gastrocnemius muscle in the right leg Figure 4.

Radiculopathy can be documented by noting denervation on needle electromyography of the muscles served by the involved nerve root.

The Lumbar Spine

Nerve compression of the S1 nerve root can also result in a delay of the H-reflex on stimulation of the tibial nerve in the popliteal fossa. A delay in F-response can be noted in cauda equina syndrome or multiple level radiculopathy. Somatosensory evoked responses will show delayed or absence latency which can occur as a result of compression of the spinal cord or cauda equina.

Thoracolumbar spine trauma. Evaluation and classification. Principles of management. The cortical somatosensory evoked potentials on stimulation of the S1 dermatome and the pudendal nerve are unobtainable on the symptomatic side, whereas the responses on stimulation of the L4 and L5 dermatomes are normal. Herniation of the lumbar disc in children and adolescents. J Pediatr Orthop ; 5 Chronic pathological changes The effects of acute and cumulative trauma result in progressive degenerative changes that affect both the intervertebral disc and the posterior facets and can be found at multiple levels of the spine.

Multilevel degenerative changes can result in decreased mobility of the spine and even fusion between the intervertebral bodies. Disc herniation, especially when painful, also results in reduced mobility and diminished levels of activity. These chronic changes asso- ciated with degenerative changes and disc herniation can have profound effects on the sensitive structures within the spinal canal and the spinal musculature. This encroachment can Figure 5. There is stenosis or narrowing of the central canal at both levels due to osteophytes protruding into the canal at the level of the disc.

The posterior muscle has been partially replaced by fibrofatty tissue. The spinal fluid has a bright signal intensity and the compression of the intrathecal rootlets is apparent. On the axial T2 MR image b , the central canal stenosis is caused by thickening of the posterior neural arch and ligamentum flavum, and overgrowth of the posterior facet joints. This causes significant flattening of the normally ovoid-appearing thecal sac Figure 5. Anteroposterior a and lateral b views of the lumbar spine following a myelogram, demonstrating a complete block of the contrast at the L2—L3 level Continued become quite marked, especially in the presence of large osteophytes from the vertebral bodies, and can result in significant stenosis of the central canal and lateral foramina.

These changes can be visualized on MRI and CT scanning, and, when severe, can disrupt function within the spinal cord and nerve roots. Such disruption can be intermittent and associated with pain or numbness in the legs on activity and which is relieved with rest, known as neurogenic claudication, or it can become permanent, leading to neurologic deficits as a result of encroachment on the spinal cord or cauda equina. Hypertrophy of the posterior facets encroaching on the neuroforamen is also evident in this type of study.

This immobilization has profound effects on paraspinal muscles. Within 3—4 weeks, atrophy of the muscle fibers can be seen on microscopy.

The cells become smaller, the number of nuclei decreases and the spaces between muscle fibers increase in size. Within 7 weeks, the spaces between muscle fibers become large and filled with fibrous collagen and the degeneration of muscle fibers becomes prominent. During exercise and remobilization of the spine, regeneration can be seen in the muscle fibers. Prominent myoblast chains are formed centrally in the empty sheath of damaged Figure 5.

Intrathecally enhanced axial computed tomogram reveals central canal stenosis secondary to posterior facet joint hypertrophy and vertebral body osteophyte formation and disc bulging c. Sagittal proton density MR image d demonstrates multiple level spondylotic changes and central canal stenosis at L2—L3 and L3—L4. Axial MR image e reveals central canal stenosis Figure 5. The reflex studies from the bulbocavernosus and urethra to the rectal sphincter are intact below the level of the injury. Cystometrogram shows hyperreflexia. The posterior muscle is replaced by fibrofatty tissue due to prolonged inactivity Figure 5.

The muscle fibers are much smaller than usual and there are a number of empty muscle sheaths. There are empty spaces between muscle fibers and few nuclei in the remaining muscles. Note the larger spaces between muscle fibers, sparse nuclei and empty muscle sheaths. There is extensive replacement of muscle fibers with fibrous tissue. There are multiple thin myoblastic chains and muscle fibers with prominent central myoblastic nuclei.

The transverse band of myoblast nuclei is noted to be central in a new muscle fiber. There is a central band of myoblast nuclei, each with two small dark nucleoli. The upper field shows new muscle fibers red. The lower field shows primarily collagen yellow with a few muscle fibers red. There is a full field of new thin muscle fibers. In the lower field, there are almost normal muscle fibers with visible mitochondria. There is degeneration of muscle with a few transverse Z-lines in a sea of debris.

The regeneration process can be seen in the development of new Z-lines. The arrow points to a new fiber. There are two new vertical Z-lines and a few transverse muscle filaments. The muscles have regenerated fully. Note the mitochondria on the left of the field. The Z-lines begin to re-form and the nuclei migrate to the periphery of the fiber. On CT and MR imaging of the spine, it is possible to visualize these changes within the posterior musculature. With immobilization, the posterior muscles are gradually replaced by fibrofatty tissue which increases with prolonged periods of inactivity.

Alterations during immobilization and regeneration of skeletal muscle. Spinal Stenosis. Clinical Orthopaedics and Related Research. Many of these abnormalities are of no clinical consequence, but under certain circumstances can predispose a patient to increasing pain. Other deformities such as scoliosis can result in cosmetic and functional difficulties. The laminae originate from the pedicle at a comparatively weak area known as the pars interarticularis or isthmus.

In childhood and adolescence, this area is subject to fatigue fracture, which may not heal properly and can lead to a fibrous union rather than a stable bony union. This can happen unilaterally or bilaterally. If it occurs a b Oblique radiographic view of the lumbar spine with a spondylolysis at L3 arrow a. The L5 disc space is narrowed, and the Knuttson gas phenomenon is seen in the disc space lower arrow Sagittal T2 weighted magnetic resonance image demonstrates a spondylolytic spondylolisthesis at L5—S1. This patient has a high shear angle at L5—S1, which may predispose to developing a spondylolisthesis.

The central spinal canal is not narrowed since the neural arch does not move anteriorly bilaterally, it creates an area of weakness between the anterior and posterior components of the vertebral arch. If this is stable, it may not be clinically important and can be an incidental finding seen on X-rays and CT scan.

This results in a slippage of the superior vertebral body on the inferior vertebral body.