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5 biomechanics of vertebral column  regional -lumbar
 

5 biomechanics of vertebral column regional -lumbar

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    5 biomechanics of vertebral column  regional -lumbar 5 biomechanics of vertebral column regional -lumbar Presentation Transcript

    • 5.Biomechanics ofVertebral Column: Regional Structure & Function-Lumbar RegionDr. D. N. BidSarvajanik College of Physiotherapy,Rampura, Surat – 395003.
    • Structure of the Lumbar Region• The first four lumbar vertebrae are similar instructure.• The fifth lumbar vertebra has structuraladaptations for articulation with the sacrum.6/14/2013 dnbid71@gmail.com 2
    • • Typical Lumbar Vertebrae• Body• The body (Fig. 4-37A) of the typical lumbarvertebra is massive, with a transverse diameterthat is greater than the anterior diameter andheight.• The size and shape reflect the need to supportgreat compressive loads caused by bodyweight, ground reaction forces, and musclecontraction.6/14/2013 dnbid71@gmail.com 3
    • • Arches– Pedicles. The pedicles are short and thick and projectposterolaterally.– Laminae. The laminae are short and broad.– Zygapophyseal Articular Processes (facets).According to Bogduk, both the superior andinferior zygapophyseal facets vary considerably inshape and orientation (see Fig. 4-37A).Mamillary processes, which appear as small bumps,are located on the posterior edge of each superiorzygapophyseal facet (see Fig. 4-37C).The mamillary processes serve as attachmentsites for the multifidus and medialintertransverse muscles.The inferior zygapophyseal facets are vertical andconvex and face slightly anteriorly and laterally.6/14/2013 dnbid71@gmail.com 4
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    • • Transverse Process. The transverse process is long andslender and extends horizontally.• Accessory processes, which are small and irregularbony prominences, are located on the posterior surfaceof the transverse process near its attachment to thepedicle (see Fig. 4-37C).• The accessory processes serve as attachment sites forthe multifidus and medial intertransverse muscles.• Spinous Process. The spinous process is broad andthick and extends horizontally.6/14/2013 dnbid71@gmail.com 6
    • • Vertebral Foramen. The vertebral foramen is triangularand larger than the thoracic vertebral foramen butsmaller than the cervical vertebral foramen.• The fifth lumbar vertebra is a transitional vertebra anddiffers from the rest of the lumbar vertebrae in that ithas a wedge-shaped body wherein the anterior portionof the body is of greater height than the posteriorportion.• The L5/S1 lumbosacral disk also is wedge shaped. Thesuperior diskal surface area of L5 is about 5% greaterthan the areas of disks at L3 and L4.6/14/2013 dnbid71@gmail.com 7
    • • The inferior diskal surface area of L5 is smallerthan the diskal surface area at other lumbarlevels.• Also, the spinous process is smaller than otherlumbar spinous processes, and the transverseprocesses are large and directed superiorlyand posteriorly.6/14/2013 dnbid71@gmail.com 8
    • • The lumbosacral articulation is formed by the fifthlumbar vertebra and first sacral segment.• The first sacral segment, which is inclined slightlyanteriorly and inferiorly, forms an angle with thehorizontal called the lumbosacral angle (Fig. 4-38).• The size of the angle varies with the position of thepelvis and affects the superimposed lumbar curvature.• An increase in this angle will result in an increase inlordosis of the lumbar curve and will increase theamount of shearing stress at the lumbosacral joint (Fig.4-39).6/14/2013 dnbid71@gmail.com 9
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    • • Intervertebral Disks• Specific regional variations occur in theintervertebral disks of the lumbar region, whichdiffer from the disks of the cervical region in thatthe collagen fibers of the anulus fibrosus arearranged in sheets called lamellae (Fig. 4-40).• The lamellae are arranged in concentric rings thatsurround the nucleus.• Collagen fibers in adjacent rings are oriented inopposite directions at 120 to each other.6/14/2013 dnbid71@gmail.com 12
    • • The advantage of the varying fiber orientation by layer isthat the anulus fibrosus is able to resist tensile forces innearly all directions.• The lumbar intervertebral disks are the largest in the body(as are the vertebral bodies).• The shape of each disk is not purely elliptical but concaveposteriorly.• This provides a greater cross-sectional area of anulusfibrosus posteriorly and hence increased ability to resist thetension that occurs here with forward bending (Fig. 4-41).6/14/2013 dnbid71@gmail.com 13
    • • Articulations• Interbody Joints• The interbody joints of the lumbar region are capable oftranslations and tilts in all directions.• Zygapophyseal Joints• The zygapophyseal joints of the lumbar region, like allothers, are true synovial joints and contain fibroadiposemeniscoid structures.• The joint capsules are more lax than in the thoracic regionbut more taut than those of the cervical region.• The dorsal capsule has been demonstrated to befibrocartilaginous in nature, which suggests that thisportion of the capsule is subject to compressive as well astensile forces.6/14/2013 dnbid71@gmail.com 14
    • • In a newborn, the zygapophyseal joints in the lumbarregion lie predominantly in the frontal plane in thepresence of lumbar kyphosis.• As the child develops and assumes an uprightposture, the curve of the lumbar region changes tolordosis, and the orientation of the zygapophysealjoints change as well.• The orientations of the adult lumbar zygapophysealjoints display great variability both between individualsand within individuals; however, the majority of themhave a curved structure that is biplanar in orientation.6/14/2013 dnbid71@gmail.com 15
    • • The anterior aspect of each joint remains in the frontalplane, and the posterior aspect lies close to or in thesagittal plane (Fig. 4-42).• The degrees to which this happens vary. The frontalplane orientation provides resistance to the anteriorshear that naturally is present in the lordotic lumbarregion.• The sagittal plane orientation allows the great range offlexion and extension ROM and provides resistance torotation.6/14/2013 dnbid71@gmail.com 16
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    • • Ligaments and Fascia• The majority of the ligaments associated with thelumbar region are the same ligaments describedpreviously (ligamentum flavum, PLL, anteriorlongitudinal ligament, interspinous and supraspinousligaments, and joint capsules).• However, a few of these ligaments have variationsspecific to the lumbar region and need to bementioned here before the iliolumbar ligaments andthe thoracolumbar fascia are introduced.6/14/2013 dnbid71@gmail.com 18
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    • • The supraspinous ligament is well developed only inthe upper lumbar region and may terminate atL3, although the most common termination siteappears to be at L4.• The ligament is almost always absent at L5/S1.• The deep layer of the supraspinous ligament isreinforced by tendinous fibers of the multifidus muscle.• The middle fibers of the supraspinous ligament blendwith the dorsal layer of the thoracolumbar fascia.• The intertransverse ligaments are not true ligaments inthe lumbar area and are replaced by the iliolumbarligament at L4.6/14/2013 dnbid71@gmail.com 21
    • • The PLL is only a thin ribbon in the lumbarregion, whereas the ligamentum flavum isthickened here.• In a study of 132 lumbar spine ligaments, Pintarand associates found that the interspinousligament had the least overall stiffness and thejoint capsules the highest.• The anterior longitudinal ligament is strong andwell developed in this region.6/14/2013 dnbid71@gmail.com 22
    • • Iliolumbar Ligaments• The iliolumbar ligaments consist of a series ofbands that extend from the tips and bordersof the transverse processes of L4 and L5 toattach bilaterally on the iliac crests of thepelvis (Fig. 4-43).6/14/2013 dnbid71@gmail.com 23
    • • There are three primary bands:– the ventral (or anterior) band, which runs from theventral caudal aspect of the transverse process of L5to the ventral surface of the iliac crest at the iliactuberosity;– the dorsal (or posterior) band, which runs from the tipof the transverse process of L5 to the cranial part ofthe iliac crest at the iliac tuberosity; and– the sacral band (sometimes called the lumbosacralligament), which runs from the ventral aspect of thetransverse process of L5 and the ala of the sacrum tothe sacral surface of the iliac tuberosity of the iliaccrest.6/14/2013 dnbid71@gmail.com 24
    • • The iliolumbar ligaments as a whole are verystrong and play a significant role in stabilizingthe fifth lumbar vertebra (preventing thevertebra from anterior displacement) and inresisting flexion, extension, axial rotation, andlateral bending of L5 on S1.6/14/2013 dnbid71@gmail.com 25
    • • Thoracolumbar Fascia• The thoracolumbar fascia (also called the lumbodorsalfascia) consists of three layers: theposterior, middle, and anterior (Fig. 4-44).• The posterior layer is large, thick, and fibrous andarises from the spinous processes and supraspinousligaments of the thoracic, lumbar, and sacral spines.• The posterior layer gives rise to the latissimus dorsicranially, travels caudally to the sacrum and ilium, andblends with the fascia of the contralateral gluteusmaximus.• Deep fibers are continuous with the sacrotuberousligament and connected to the posterior superior iliacspines, iliac crests, and PLL.6/14/2013 dnbid71@gmail.com 26
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    • • The posterior layer also travels laterally over theerector spinae muscles and forms the lateralraphe at the lateral aspect of the erector spinae.• The internal abdominal oblique and thetransversus abdominal muscles arise from thelateral raphe.• The posterior layer becomes the middle layer andtravels medially again along the anterior surfaceof the erector spinae and attaches back to thetransverse processes and intertransverseligaments of the lumbar spine.6/14/2013 dnbid71@gmail.com 28
    • • These two layers completely surround thelumbar extensor muscle group.• The anterior layer of the thoracolumbar fasciais derived from the fascia of the quadratuslumborum muscle, where it joins the middlelayer, inserts into the transverse processes ofthe lumbar spine, and blends with theintertransverse ligaments.6/14/2013 dnbid71@gmail.com 29
    • • McGill described the fascia as a stabilizing corsetthat forms a “hoop” around the abdomen alongthe abdominal muscles and their fascia (see Fig.4-44).• Gracovetsky designated:– the anterior layer of the thoracolumbar fascia as the“passive part” and– the posterior layer as the “active part.”6/14/2013 dnbid71@gmail.com 30
    • • According to Gracovetsky, the passive part serves totransmit tension produced by a contraction of the hipextensors to the spinous processes.• The active portion is activated by a contraction of thetransversus abdominis muscle, which tightens thefascia.• The fascia transmits tension longitudinally to the tips ofthe spinous processes of L1/L4 and may help the spinalextensor muscles to resist an applied load.6/14/2013 dnbid71@gmail.com 31
    • • Vleeming found that both the gluteusmaximus and contralateral latissimus dorsitensed the superficial layer and provided apathway for the mechanical transmission offorces between the pelvis and the trunk.6/14/2013 dnbid71@gmail.com 32
    • Function of the Lumbar Region• Kinematics• The lumbar region is capable of movement inflexion, extension, lateral flexion, and rotation.The lumbar zygapophyseal facets favor flexionand extension, because of the predominantsagittal plane orientation (see Fig. 4-18A).• Flexion of the lumbar spine is more limited thanextension and, normally, it is not possible to flexthe lumbar region to form a kyphotic curve.6/14/2013 dnbid71@gmail.com 33
    • • The amount of flexion varies at eachinterspace of the lumbar vertebrae, but mostof the flexion takes place at the lumbosacraljoint.• During flexion and extension, the greatestmobility of the spine occurs between L4 andS1, which is also the area that must supportthe most weight.6/14/2013 dnbid71@gmail.com 34
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    • • Rotation in this region, however, is more limitedbecause of the shape of the zygapophyseal joints (Fig.4-45).• The effectiveness of the zygapophyseal joints inresisting axial rotation depends on the extent that thesuperior facets face medially (in the sagittal plane).• The greater the medial orientation of the jointsurfaces, the greater the resistance to axial rotation.6/14/2013 dnbid71@gmail.com 36
    • • In the lumbar region, pure flexion and extension canoccur, but coupled motions always occur with lateral flexionand axial rotation.• With lateral flexion, pronounced flexion and slightipsilateral rotation occurs.• With axial rotation, however, substantial lateral flexion in acontralateral direction occurs, but only a slight amount offlexion occurs.• Lateral flexion and rotation are most free in the upperlumbar region and progressively diminish in the lowerregion.• The largest lateral flexion ROM and axial rotation occursbetween L2 and L3.6/14/2013 dnbid71@gmail.com 37
    • • Little or no lateral flexion or rotation is possible at thelumbosacral joint because of the most commonorientation of the zygapophyseal joints, at 45 to thesagittal plane.• There is, however, a considerable amount of variationin the degree of axial rotation of lumbar vertebrae.• In addition to being affected by facet orientation, theamount of rotation available at each vertebral levelappears to be affected by the position of the lumbarspine.6/14/2013 dnbid71@gmail.com 38
    • • When the lumbar spine is flexed, the ROM inrotation is less than when the lumbar spine is inthe neutral position.• The posterior anulus fibrosus and the PLL seem toplay an important role in limiting axial rotationwhen the spine is flexed.• The zygapophyseal joint capsules limit rotation inboth the neutral and extended positions of thespine.6/14/2013 dnbid71@gmail.com 39
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    • • Continuing Exploration: Lumbar-Pelvic Rhythm• Cailliet described a specific instance ofcoordinated, simultaneous activity of lumbarflexion and anterior tilting of the pelvis in thesagittal plane during trunk flexion andextension.• He called the combined lumbar and pelvicmotion lumbar-pelvic rhythm.• The activity of bending over to touch one’stoes with knees straight depends on lumbar-pelvic rhythm.6/14/2013 dnbid71@gmail.com 42
    • • According to Cailliet, the first part of bending forwardconsists of lumbar flexion, followed next by anteriortilting of the pelvis at the hip joints (Fig. 4-46).• A return to the erect posture is initiated by posteriortilting of the pelvis at the hips, followed by extension ofthe lumbar spine.• The initial pelvic motion delays lumbar extension untilthe trunk is raised far enough to shorten the momentarm of the external load, thus reducing the load on theerector spinae.6/14/2013 dnbid71@gmail.com 43
    • Normal Lumbar Motion6/14/2013 dnbid71@gmail.com 44
    • Alterations to lumbopelvic mobility6/14/2013 dnbid71@gmail.com 45
    • • Nelson and coworkers studied lumbar-pelvicmotion in 30 healthy women, age 19 to 35years, who lifted and replaced a 9.5-kg weight onthe floor.• They found that lumbar and pelvic motion werevariable among these individuals and tended tooccur simultaneously during trunk flexion andmore sequentially during trunk extension.6/14/2013 dnbid71@gmail.com 46
    • • The use of a weight may have affected thelumbar-pelvic rhythm, but this study raisesquestions about exactly when and how trunkand pelvic motion occurs.• McGill reported that he and his colleagues hadnever seen this strict sequence described byCalliet in any of the vast number of studiesthat they had done.6/14/2013 dnbid71@gmail.com 47
    • • There is no argument, however, that the integration ofmotion of the pelvis about the hip joints with motionof the vertebral column not only increases the ROMavailable to the total column but also reduces theamount of flexibility required of the lumbar region.• Hip motion may even, as McGill suggested, eliminatethe need for full lumbar flexion, which would serve aprotective function by protecting the anulus fibrosusand posterior ligaments from being fully lengthened.6/14/2013 dnbid71@gmail.com 48
    • • The contribution to motion from multiple areas toproduce a larger ROM than could be accomplished by asingle area is similar to what is found at the shoulder inscapulohumeral rhythm.• A restriction of motion at either the lumbar spine or atthe hip joints may disturb the rhythm and prevent aperson from reaching the toes.• Restriction of motion at one segment also may result inhypermobility of the unrestricted segment.6/14/2013 dnbid71@gmail.com 49
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    • • Kinetics• Compression• One of the primary functions of the lumbar region is toprovide support for the weight of the upper part of thebody in static as well as in dynamic situations.• The increased size of the lumbar vertebral bodies anddisks in comparison with their counterparts in theother regions helps the lumbar structures support theadditional weight.• The lumbar region must also withstand thetremendous compressive loads produced by musclecontraction.6/14/2013 dnbid71@gmail.com 52
    • • Experimental testing of 10 cadaver spines subjected to1000-N compressive loading demonstrated that thelumbar interbody joints shared 80% of the load, andthe zygapophyseal facet joints in axial compressionshared 20% of the total load.• This percentage can change with altered mechanics:with increased extension or lordosis, thezygapophyseal joints will assume more of thecompressive load.• Also, with degeneration of the intervertebral disk, thezygapophyseal joints will assume increasedcompressive load.6/14/2013 dnbid71@gmail.com 53
    • • Khoo and colleagues compared lumbosacral loads(ground reaction forces and accelerations plus forcesgenerated by erector spinae and rectus abdominismuscle groups) at the center of the L5/S1 joint in staticversus dynamic situations in 10 men.• Lumbosacral loads in the erect standing posture werein the range of 0.82 to 1.18 times bodyweight, whereas lumbosacral loads during levelwalking were in the range of 1.41 to 2.07 times bodyweight (an increase of 56.3%).6/14/2013 dnbid71@gmail.com 54
    • • Changes in position of the body will changethe location of the body’s line of gravity andthus change the forces acting on the lumbarspine.6/14/2013 dnbid71@gmail.com 55
    • • Shear• In the upright standing position, the lumbarsegments are subjected to anterior shear forcescause by the lordotic position, the bodyweight, and ground reaction forces (see Fig. 4-39).• This anterior shear or translation of the vertebrais resisted by direct impaction of the inferiorzygapophyseal facets of the superior vertebraagainst the superior zygapophyseal facets of theadjacent vertebra below.6/14/2013 dnbid71@gmail.com 56
    • • The effectiveness of the zygapophyseal joint inproviding resistance to anterior translation duringflexion depends on the extent to which the inferiorvertebra’s superior facets lie in the frontal plane andface posteriorly.• The more that the superior zygapophyseal facets of anadjacent inferior vertebra face posteriorly, the greaterthe resistance they are able to provide to forwarddisplacement because the posteriorly facing facets lockagainst the inferior facets of the adjacent superiorvertebra.6/14/2013 dnbid71@gmail.com 57
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    • Thank you….,End of Part - 56/14/2013 dnbid71@gmail.com 59