Spine

Spine

Spine

Table of Contents

Introduction

Review of the Normal Anatomy and Biomechanics of Human Spine

Abormal Anatomy and Biomechanics of Human Spine

Degenerative Spinal Disease

Spinal Stenosis

Spondylosis

Scoliosis

Bibliography

Introduction

The human spine is essentially a mechanical structure that operates along a system of levers , pivots , activators , and restraints . This mechanical structure in very flexible and has a wide range of motion but it also has the ability to be a very strong and stable structure One of the major causes of

chronic disability in the adult working population is due to the degenerative changes in the human spine . Spinal degeneration is a normal part of aging , and neck and back pain are one of life 's most common problems . There are many potential sources of pain , and finding the specific cause is often a problem for the patient and doctor . The aim of this research is to discuss the normal anatomy and the biomechanics of the human spine as well as the abnormal changes a person experiences when the spine becomes degenerative . In most cases neck and back pain can be temporarily eliminated through the use of conservative therapy , but if the pain is severe or neurological surgical intervention may be necessary

Review the Normal Anatomy and Biomechanics of Human Spine

The vertebral column or spine is made up of a series of bones called vertebrae . The spine is a strong and flexible column of bones made up of the cervical , thoracic , lumbar , sacral , and coccygeal regions . The cervical or neck region is normally made up of 7 bones , the thoracic or chest region has 12 bones , and the lumbar or low back region is made up of 5 bones . The sacral region consists of 5 fused bones , and the coccygeal region 3 to 5 tiny bones . However variations do occur . The spine is curved and in pro looks like an elongated letter "S " in shape . The cervical and lumbar regions have a forward curve and the thoracic region a backward curve when viewed from the side . It has been suggested that the S shape of the spine : facilitates energy absorption and protects the spinal structures against impact by increasing its strength helps maintain balance in the upright position andabsorbs shocks when a person walks

Variation in vertebrae size , shape and detail occur in the different regions of the spine . For example , the lumbar vertebrae are the largest and strongest . In general , however , all vertebrae have the same basic structure . There are three main parts to a vertebra (White Panjabi

Vertebral Body (weight bearing structure

The vertebral body is a thick , disc shaped cylindrical block of bone flattened at the back and with roughened top and bottom surfaces . It is made up of spongy bone on the inside , which enables it to resist compression , and a thin outer covering of compact bone . It is the weight bearing part of vertebrae

Vertebral Arch (protective in function

The vertebral arch surrounds the spinal column and is protective in function

The vertebral arch , or neural arch as it is sometimes called , extends backwards from the vertebral body . It is made up of two short , thick processes called pedicles that stick out backwards from the vertebral body and join the laminae . The laminae are flat and join together to form the back part of the vertebral arch . Together the vertebral arch and vertebral body surround the spinal column . The space occupied by the spinal column is called the vertebral foramen . The vertebral foramen when stacked on top of each other , forms the vertebral or spinal canal On each side of the vertebral column there is an opening between each vertebrae called the intervertebral foramen which enables the spinal nerves to pass through

Vertebral Processes

There are seven different processes that come from the vertebral arch . A transverse process extends sideways on each side from the junction of a lamina and pedicle . A single spinous process extends back and downwards from the junction of the laminae . These three processes have spinal muscles to them . The other four articular processes form joints with other vertebrae . The two articular processes on top form a joint with the two articular processes on the bottom of the vertebrae above and the two bottom processes form a joint with the two processes on top of the vertebrae below

Vertebral Disks

Adjacent vertebral bodies are to each other by an intervertebral disc . The disc is made up of a central mass of pulpy tissue called the nucleus pulposus and a tough outer covering of fibro-cartilage called the annulous fibrosis . The layers of the annulus are thinner at the back , making this area potentially more prone to damage . The discs are shock absorbers , giving resilience to the spinal column as well as flexibility . When a body is erect , the various parts of the disc are under uniform pressure but when the spine is flexed extended or bent to the side , one part of the disc is under increased compression whereas another part is under tension (Frankel

Ligaments

Ligaments are strong bands of fibrous tissue that connect structures such as bone to bone . Two long ligaments , one at the front and one at the back (anterior and posterior longitudinal ligament , extend the length of the vertebral column . They are to the discs and help prevent excessive movement of the spinal column . An abnormal stress may tear the outer fibres of a disc , causing the jelly like nucleus pulpous to leak out and press on neighbouring spinal nerves . The joints between the vertebral arches are connected by different types of ligamentous tissue (White Panjabi

Articular capsules made up of thin loose ligaments to the edges of the articular processes of adjacent vertebrae

Ligamenta flava are elastic sheets connecting the laminae of adjacent vertebrae

Supraspinous ligament : a strong fibrous cord connecting the spinous processes from the seventh cervical vertebrae to the sacrum

Interspinous ligaments are weak bands that connect adjacent spinous processes and similar bands called intertransverse ligaments are found between transverse processes in the lumbar region

Muscles

The muscles of the spine are important in maintaining its stability and balance as well as assisting in spinal movement . The superficial back muscles are mainly concerned with movements of the upper limbs . The post-vertebral spinal muscles , or deep back muscles , are numerous and varied in structure and function . Muscles extend from the sacrum to the skull and allow such movements as rotation and extension (backward bending ) of the spine

The muscles that are important for the stability of the spine include the : Latissimus Dorsi Lumbar Paravertebral Muscles and the Multifidus The abdominal muscles (found at the front of the spine wrapping around the side of the trunk ) form a natural corset with other muscles and play a major role in the maintenance of spinal stability . The abdominal muscles include the : Rectus Abdominus Internal and External Oblique muscles and the Transversus Abdominus muscle (Herzog

Spinal Cord Spinal Nerves

The spinal cord is cylindrical in shape and starts as an extension of the lower part of the brain stem and finishes at around the second lumbar vertebrae . The cord is made up of some 31 segments that each give rise to a pair of spinal nerves . The spinal cord is protected by the spinal column , the spinal meninges (dense fibrous covering , the cerebrospinal fluid (special fluid surrounding the brain and spine , and the vertebral ligaments . The main function of the spinal cord is to convey motor impulses from the brain to the muscles , and sensory information from the body to the brain (Frankel

There are 31 pairs of spinal nerves named and numbered according to the level and region of the spine from which they emerge . There are 8 pairs of cervical nerves , 12 pairs of thoracic nerves , 5 pairs of lumbar and sacral nerves , and 1 pair of coccygeal nerves . With the exception of the first pair of cervical nerves , all spinal nerves leave the vertebral column from the intervertebral foramen (White Panjabi

Functions of the Spine

The spine has four main functions : support mobility housing and protection and control

Support . In human beings , the vertebral or spinal column is the principle supporting structure . The spine bears heavy loads , in particular the cervical and lumbar regions , including the weight of the upper body and any loads being lifted , lowered , carried or held

Mobility . The upper and lower limbs are through a series of joints to the spine . Muscles , ligaments and tendons connect parts of the spine to each other as well as to the other limbs and allow a diverse range of movements to occur . The cervical and lumbar spine areas are particularly flexible . Forward bending (flexion ) and backward bending (extension ) of the lumbar spine produce the greatest range of movement in the spine . Twisting (rotation ) and side bending (lateral flexion ) are common spinal movements during manual handling

Housing Protection . The spinal column protects the spinal cord and nerves as they pass from the brain to the upper and lower limbs

Control . The movement of each segment of the spine is controlled actively by muscles and passively by ligaments . Without muscular support , the spine is unstable . Movement of the human body is initiated and controlled by the contraction of muscles . Ligaments and other soft tissue surround joints and prevent unwanted abnormal movements

Finally , normal spine biomechanics is required to maintain a healthy spine . Abnormal biomechanics can be classified as hypomobile (decreased movement between vertebrae , hypermobile (increased ) movement between vertebrae or instability (severe loss of stability . Muscle weakness ligament injury , broken bones or damage to the intervertebral disc can all lead to abnormal biomechanics , a major factor in the development of neck and back pain

Abnormal Anatomy and Biomechanics of Human Spine

The anatomical changes seen in degenerative disease of the spine are very complex . They may occur in a cascading sequence or may occur simultaneously in all components . Degeneration of any of the components of the motion segment may result in abnormal function of that segment The degenerative process usually begins in either of the facet joints or in the disc . Eventually , all motion segment components are affected with degenerative changes

The disc is often the first component to experience anatomical changes By the age of fifty years , over 95 of all people will have lumbar disc degeneration . However , this does not mean that all people will have symptoms . The most significant alterations to the disc are , the water and proteoglycan content of the nucleus pulposus decreases . The water and proteoglycan content of the annulus decreases , but not to the extent of the nucleus . The collagen fibers of the annulus fibrosus become distorted . Tears may occur in the lamellae , due in part to distortion of the collagen fibers , and could result in a loss of annular strength

Each disc can be classified in terms of one , and occasionally more than one , of the following diagnostic categories (Milette : Normal Congenital /Developmental Variation Degenerative /Traumatic Infectious /Inflammatory . Each diagnostic category can be subcategorized to various degrees of specificity according to the information available and purpose to be served

Normal : Normal defines young discs , which are morphologically normal without consideration of the clinical context and not inclusive of degenerative , developmental , or adaptive changes that could , in some contexts (e .g . normal aging , scoliosis , spondylolisthesis ) be considered clinically normal . However , the bilocular appearance of the adult nucleus resulting from the development of a central horizontal band of fibrous tissue is considered a sign of normal maturation

Congenital or Developmental Variation : The Congenital /Developmental Variation category includes discs that are congenitally abnormal or that have undergone changes in their morphology as an adaptation to abnormal growth of the spine such as from scoliosis or spondylolisthesis

Degenerative or Traumatic : Degenerative and /or traumatic changes in the disc are included in a broad category that includes subcategories of Anular Tear Herniation and Degeneration . Characterization of this group of discs as Degenerative /Traumatic does not imply that trauma is necessarily a factor or that degenerative changes are necessarily pathologic as opposed to the normal aging process . Anular tears , also properly called anular fissures , are separations between anular fibers avulsion of fibers from their vertebral body insertions , or breaks through fibers that extend radially , transversely , or concentrically involving one or many layers of the anular lamellae

Degeneration may include any or all of : real or apparent desiccation fibrosis , narrowing of the disc space , diffuse bulging of the anulus beyond the disc space , extensive fissuring (i .e . numerous anular tears and mucinous degeneration of the anulus , defects and sclerosis of the end-plates , and osteophytes at the vertebral apophyses . A disc demonstrating one or more of these degenerative changes is divided into two sub-categories : spondylosis deformans , possibly representing changes in the disc associated with a normal aging process or intervertebral osteochondrosis , possibly the consequences of a more clearly pathologic process

Herniation is a localized displacement of disc material beyond the limits of the intervertebral disc space . The disc material may be nucleus , cartilage , fragmented apophyseal bone , anular tissue , or any combination thereof . The disc space is defined , craniad and caudad , by the vertebral body end-plates and , peripherally , by the outer edges of the vertebral ring apophyses , exclusive of osteophytic formations

Localized displacement in the axial plane can be focal , signifying less than 25 of the disc circumference , or broad-based , meaning between 25 and 50 of the disc circumference . Presence of disc tissue circumferentially (50-100 ) beyond the edges of the ring apophyses may be called "bulging " and is not considered a form of herniation , nor are diffuse adaptive alterations of disc contour secondary to adjacent deformity as may be present in severe scoliosis or spondylolisthesis (Milette

Herniated discs may take the form of protrusion or extrusion , based on the shape of the displaced material . Protrusion is present , if the greatest distance , in any plane , between the edges of the disc material beyond the disc space is less than the distance between the edges of the base in the same plane . The base is the cross-sectional area of disc material at the outer margin of the disc space of origin , where disc material displaced beyond the disc space is continuous with disc material within the disc space . In the cranio-caudal direction , the length of the base is not exceed the height of the intervertebral space Extrusion is when , in at least one plane , any one distance between the edges of the disc material beyond the disc space is greater than the distance between the edges of the base in the same plane , or when no continuity exists between the disc material beyond the disc space and that within the disc space

Migration is displacement of disc material away from the site of extrusion , regardless of whether sequestrated or not . Because posteriorly displaced disc material is often constrained by the posterior longitudinal ligament , images may portray a disc displacement as a protrusion on axial sections and an extrusion on sagittal sections in which cases the displacement should be considered an extrusion Herniated discs in the cranio-caudal (vertical ) direction through a break in the vertebral body end-plate are referred to as intravertebral herniations . Disc herniations may be further specifically described as contained , if the displaced portion is covered by outer anulus , or uncontained when absent any such covering . Displaced disc tissues may also be described by location , volume , and content

Degenerative Spinal Disease

Firstly , we need to define of normal and degenerative disks to make following discussion

Normal : The disc is fully and normally developed and free of any changes of disease , trauma , or aging . Only the morphology , and not the clinical context , is considered . In common practice , people with a variety of harmless congenital or developmental variations of discs , minor bulging of anuli , anterior and lateral marginal vertebral body osteophytes , etc are normal people . Some people are clinically "normal " even though they have morphologically abnormal discs

Disc Degeneration : Because there is confusion in differentiation of changes of pathologic degenerative processes in the disc from those of normal aging (Czervionke ) category "Degenerative /Traumatic " includes all such changes , thus does not compel the observer to differentiate the pathologic from the normal consequences of aging . Perceptions of what constitutes the normal aging process of the spine have been greatly influenced by post-mortem anatomical studies involving a limited number of specimens , harvested from cadavers from different age groups , with unknown past medical histories , and the presumption of absence of lumbar symptoms (Coventry , Eckert

With such methods , pathologic changes are easily confused with consequences of normal aging . Resnick and Niwayama emphasized the differentiating features of two degenerative processes involving the intervertebral disc , which had been previously described by Schmorl and Junghanns "spondylosis deformans " which affects essentially the anulus fibrosus and adjacent apophyses , and "intervertebral osteochondrosis (145 ) which affects mainly the nucleus pulposus and the vertebral body end-plates , but also includes extensive fissuring (numerous tears ) of the anulus fibrosus , which may be followed by atrophy . Although Resnick and Niwayama stated that the cause of the two entities was unknown other scientific studies suggest that spondylosis deformans is the consequence of normal aging , whereas intervertebral osteochondrosis sometimes also called "deteriorated disc " results from a clearly pathologic , though not necessarily symptomatic , process (Sauser et al Twomey Taylor

With normal aging , fibrous tissue replaces nuclear mucoid matrix , but the disc height is preserved and the disc margins remain regular (Jarvik et al ) Radial tears of the anulus are found only in a minority of post-mortem examinations of individuals over 40 years old (Kieffer et al ) and therefore cannot be considered a usual consequence of aging Slight symmetric bulging of the disc may occur in the elderly due to remodeling associated with osteoporosis (Twomey Taylor ) On conventional radiographs and CT , small amounts of gas can be detected in some elderly individuals at the anular /apophyseal enthesis , probably located in small transverse anular tears , and possibly signifying early manifestations of spondylosis deformans however , a large amount of gas in the central disc space is always pathologic and is a feature of intervertebral osteochondrosis (Yu et al

Anterior and lateral marginal vertebral body osteophytes have been found in 100 of skeletons of individuals over 40 , so are consequences of normal aging , whereas posterior osteophytes have been found in only a minority of skeletons of individuals over 80 , so are not inevitable consequences of aging (Nathan ) End-plate erosions with osteosclerosis and chronic reactive bone marrow changes also appear to be pathologic Slight to moderate decrease in central disc signal intensity found on T2-weighted MR images can be a non-pathologic age-related observation but , if the result of a normal process , should be relatively uniform among all discs studied in the individual

Intervertebral osteochondrosis , or deteriorated disc , also sometimes called chronic discopathy , shows , on microscopic examination , structural disorganization and general replacement of normal disc tissue by fibrosis . Radiographically , intervertebral osteochondrosis is characterized by narrowing of the intervertebral space , irregular disc contour often associated with bulging , multi-directional osteophytes often involving the central spinal canal and foramina , end-plate erosions with reactive osteosclerosis , and chronic vertebral body bone marrow changes . On T2-weighted images , the central disc signal intensity is usually markedly decreased , and at distinct variance to that seen in unaffected discs of the same individual . The distinction is made at the time of the reading and does not imply that early manifestations of a pathologic process are always distinguishable from changes of normal aging (Yu et al

Herniated Disc : Herniated disc denotes displacement of disc material The term is appropriate to denote the general diagnostic category when referring to a specific disc and to be inclusive of various types of displacement when speaking of groups of discs . It includes discs that may properly be characterized by more specific terms , such as "protruded disc " or "extruded disc (Milette

Herniated disc refers to localized displacement of nucleus , cartilage fragmented apophyseal bone , or fragmented anular tissue beyond the intervertebral disc space (disc space , interspace . The interspace is defined , craniad and caudad , by the vertebral body end-plates and peripherally , by the edges of the vertebral ring apophyses , exclusive of osteophytic formations . Displacement of disc material , either through a fracture in the bony end-plate or in conjunction with displaced fragments of fractured walls of the vertebral body , may be described as "herniated " disc , though such should accompany of the fracture so as to avoid confusion with primary herniation of disc material . Displacement of disc materials from one location to another within the interspace , as with intra-anular migration of nucleus without displacement beyond the interspace , is not considered herniation

When "herniated " disc material is displaced from its normal location and not simply represent an acquired growth beyond the edges of the apophyses , as is the case when connective tissues develop in gaps between osteophytic formations . Displacement , therefore , can only occur in association with disruption of the normal anulus or , as in the case of intravertebral herniation (Schmorl 's node , a break in the vertebral body end-plate . Since details of the integrity of the anulus are often unknown , the distinction of herniation is usually made by observation of displacement of disc material beyond the edges of the ring apophyses that is "localized " meaning less than 50 (180 degrees ) of the circumference of the disc . Generalized , meaning greater than 50 displacement of disc material beyond the ring apophyses , or adaptive changes of the apophyses and /or outer anulus to adjacent abnormality such as may occur with scoliosis or spondylolisthesis , are not herniations . The 50 cut-off line is established by way of convention to lend precision to terminology and does not demarcate etiology , relation to symptoms , or treatment indications (Milette

Protruded Discs : A disc is "protruded " if the greatest distance , in any plane , between the edges of the disc material beyond the disc space is less than the distance between the edges of the base in the same plane The term "protrusion " is only appropriate in describing herniated disc material , as discussed above . Protrusions may be "focal " or "broad-based " The distinction between focal and broad-based is arbitrarily set at 25 of the circumference of the disc . Protrusions with a base less than 25 (90 degrees ) of the circumference of the disc are "focal " If disc material is herniated so that the protrusion encompasses 25 to 50 of the circumference of the disc , it is considered "broad-based protrusion (Milette

Extruded Discs : The term "extruded " is consistent with the lay language meaning of material forced from one domain to another through an aperture . With reference to a disc , the test of extrusion is the judgment that , in at least one plane , any one distance between the edges of the disc material beyond the disc space is greater than the distance between the edges of the base measured in the same plane , or when no continuity exists between the disc material beyond the disc space and that within the disc space . Extruded disc material that has no continuity with the disc of origin may be further characterized as "sequestrated . A sequestrated disc is a subtype of "extruded disc " but by definition , can never be a "protruded disc " Disc material that is displaced away from the site of extrusion , regardless of continuity , may be called "migrated " a term which is useful for the interpretation of imaging studies because it is often impossible from images to know if continuity exists (Milette

Displaced disc fragments are sometimes characterized as "free " A "free fragment " is synonymous with a "sequestrated fragment " and not the same as "uncontained " as the latter refers only to the integrity of the outer anulus and has no inference as to the continuity of the displaced disc material with the parent disc . Migrated disc or fragment refers to displacement of disc material away from the opening in the anulus through which the material has extruded

Spinal Stenosis

Spinal stenosis is a progressive condition that represents approximately 5 of all back disease . Symptoms usually appear around age 50 to 60 and lead to increasing pain and disability as the condition progresses Understanding the dis , appropriate diagnostic tests , and treatment options is essential to providing appropriate nursing care and education for this patient population . About 5 of all patients presenting with low back pain are diagnosed with spinal stenosis (Connelly . While many conditions can lead to spinal stenosis , degenerative changes associated with aging are a frequent cause of symptoms . As the degenerative processes of aging accelerate during the 50s and 60s , early symptoms of spinal stenosis may begin

Lumbar and cervical stenosis are much more common than thoracic stenosis (Esses . While not specifically associated with a particular occupation lumbar spinal stenosis is more prevalent among men (Hilibrand Rand As the population ages and individuals continue their active lifestyles the incidence of symptomatic spinal stenosis is expected to rise (Spivak

Spinal stenosis is defined as a narrowing of the space within the spinal canal , intervertebral foramina , or nerve root canal and can occur in any portion of the spine . This narrowing may be at one or more levels and may affect the nerve root canals , intervertebral foramen , or the spinal canal itself . Limited space causes compression of the affected nerves and blood vessels . Narrowing can be congenital , acquired , or a combination of the two (Garfin et al

Stenosis can be further classified by location . Central stenosis involves the compression of the spinal cord or the cauda equina . Lateral stenosis involves compression of a spinal nerve root . Hypertrophy of the facet joint , disc degeneration , bulging of the disc into the spinal canal , or structural changes that occur when one vertebra slips forward on the next lower vertebra (spondylolisthesis ) can all lead to stenosis Symptoms are widely variable and depend on the degree and location of stenosis and other contributing conditions (Hilibrand Rand

Degeneration of the disc begins with loss of water from the nucleus pulposus resulting in a loss of disc height . As the adjacent vertebra press on the disc , the annulus can protrude into the spinal canal causing pressure on the spinal cord or cauda equina . Narrowing of the disc space causes a shift (usually anterior ) in vertebral alignment resulting in subluxation of one vertebra over the next lower one

Facet joints change their alignment , ligaments become lax , and motion increases as subluxation progresses . The foramen becomes smaller putting pressure on the exiting spinal nerve root (s . Osteophytes may also form along the facet joint resulting in further pressure on the exiting nerve root (s (Jenis An

Spondylosis

Cervical spondylosis refers to common age-related changes in the area of the spine at the back of the neck . With age , the vertebrae (the component bones of the spine ) gradually form bone spurs , and their shock-absorbing disks slowly shrink . These changes can alter the alignment and stability of the spine . They may go unnoticed , or they may produce problems related to pressure on the spine and associated nerves and blood vessels . This pressure can cause weakness , numbness , and pain in various areas of the body . In severe cases , walking and other activities may be compromised (McCormack Weinstein

As the amount of padding shrinks , the spine loses stability . The vertebrae react by constructing osteophytes , commonly known as bone spurs . There are seven vertebrae in the neck development of osteophytes on these bones is sometimes called cervical osteoarthritis . Osteophytes may help to stabilize the degenerating backbone and help protect the spinal cord . By age 50 , 25-50 of people develop cervical spondylosis by 75 years of age , it is seen in at least 70 of people . Although shrunken vertebral disks , osteophyte growth , and other changes in their cervical spine may exist , many of these people never develop significant problems (Bohlman

However , about 50 of people over age 50 experience neck pain and stiffness due to cervical spondylosis . Of these people , 25-40 have at least one episode of cervical radiculopathy , a condition that arises when osteophytes compress nerves between the vertebrae . Another potential problem occurs if osteophytes , degenerating disks , or shifting vertebrae narrow the spinal canal . This pressure compresses the spinal cord and its blood vessels , causing cervical spondylitic myelopathy , a dis in which large segments of the spinal cord are damaged . This dis affects fewer than 5 of people with cervical spondylosis (Bohlman ) Symptoms of both cervical spondylitic myelopathy and cervical radiculopathy may be present in some people

Scoliosis

Scoliosis is abnormal curvature of the spine . While the normal spine has gentle natural curves that round the shoulders and make the lower back curve inward , scoliosis typically involves a three-dimensional deformity of the spinal column and rib cage . To varying degrees , the spine curves from side to side , and some of the spinal bones may rotate slightly making the hips or shoulders appear uneven . It may develop in the following ways (Broom : as a single , primary side-to-side curve (resembling the letter C , or as two curves (a primary curve along with a compensating secondary curve that form an S shape

Scoliosis most commonly develops in the thoracolumbar region , which is the area between the upper back (the thoracic area ) and lower back (lumbar area . It may also occur only in the upper back or the lower back . The physician attempts to define scoliosis by the following characteristics : The shape of the curve its location its direction ?its magnitude its causes , if possible

The severity of scoliosis is determined by the extent of the spinal curvature and by the angle of the trunk rotation (ATR ) and is usually measured in degrees . Curves of less than 20 degrees are considered mild and account for 80 of scoliosis cases . Curves that progress beyond 20 degrees require medical attention . However , such attention usually involves periodic monitoring to make sure the condition is not becoming worse . While as many as one in 25 children has some degree of scoliosis only four out of every 1 ,000 people in the US have moderate to severe curves beyond 20 degrees (McIntosh

Scoliosis is often categorized by the shape of the curve , usually as either structural or nonstructural . In structural scoliosis , the spine not only curves from side to side , but the vertebrae also rotate twisting the spine . As it twists , one side of the rib cage is pushed outward so that the spaces between the ribs widen and the shoulder blade protrudes (producing the rib-cage deformity , or hump . The other half of the rib cage is twisted inward , compressing the ribs (Broom

A nonstructural curve does not twist but is a simple side-to-side curve ?Other abnormalities of the spine that may occur alone or in combination with scoliosis include hyperkyphosis (an abnormal exaggeration in the backward rounding of the upper spine ) and hyperlordosis (an exaggerated forward curving of the lower spine , also called swayback

The location of a structural curve is defined by the location of the apical vertebra . This is bone at the highest point (the apex ) in the spinal hump . This particular vertebra also undergoes the most severe rotation during the disease process . The direction of the curve in structural scoliosis is determined by whether the convex (rounded ) side of the curve bends to the right or left . For example , a physician will diagnose a patient as having right thoracic scoliosis if the apical vertebra is in the thoracic (upper back ) region of the spine and the curve bends to the right (McIntosh

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