Lumbar Spnine: Anatomy, Biomechanics and Pathomechanics

Lumbar Spine:Lumbar Spine:
Biomechanics,Biomechanics,
PathomechanicsPathomechanics
Radhika ChintamaniRadhika Chintamani
04/11/2004/11/20 11Lx SpineLx Spine

CONTENTS
 Introduction.
 Anatomy: Vertebrae, Muscular attachments, Ligamentous
support
 Thoracolumbar Fascia
 IVD
 Mechanics: Angles of Lx, Kinetics, Kinematics: Joint
coupling, Lumbo-pelvic rhythm, Flexion-relaxation response
 Pathomechanics: Lumbarization, Sacralization, facet joint
arthropathy, facet tropism, PIVD, Stenosis, Spondylo: -sis, -
lysis and lesthesis, bony overgrowth and Anklysoing
spondylitis.

IntroductionIntroduction
 The human spine acts as aThe human spine acts as a
multisegmental, flexible rodmultisegmental, flexible rod
forming the central axis of theforming the central axis of the
neck and trunk.neck and trunk.
 Lordotic curves (apexLordotic curves (apex
anterior) are present in theanterior) are present in the
lumbar and cervical spines,lumbar and cervical spines,
thoracic has a kyphoticthoracic has a kyphotic
curvature (apexcurvature (apex
posteriorly).These curvesposteriorly).These curves
help to enhance the repetitivehelp to enhance the repetitive
load-bearing capacity of theload-bearing capacity of the
spine by providing “flex,” orspine by providing “flex,” or
damping function.damping function.

Transitional ZonesTransitional Zones
 The junctions between these curves are areas of great forceThe junctions between these curves are areas of great force
concentration and are called transitional zones.concentration and are called transitional zones.
 These zones are frequent sites of tissue injury resulting inThese zones are frequent sites of tissue injury resulting in
dysfunction and nociception: For example, in the lumbar spinedysfunction and nociception: For example, in the lumbar spine
the junction between L5 and S1 (lumbosacral joint) is a verythe junction between L5 and S1 (lumbosacral joint) is a very
common site of pain complaint. Vertebrae near and withincommon site of pain complaint. Vertebrae near and within
transitional zones have unique characteristics and aretransitional zones have unique characteristics and are
referred to as atypical vertebrae.referred to as atypical vertebrae.
Lx SpineLx Spine 4404/11/2004/11/20

Articular Tripod:Articular Tripod: Intervertebral joints + pair ofIntervertebral joints + pair of
apophyseal jointsapophyseal joints
 In this tripod, these joints work in a closed chain kinematicIn this tripod, these joints work in a closed chain kinematic
mechanism. Hence, if one gets displaced, other two have to getmechanism. Hence, if one gets displaced, other two have to get
displaced.displaced.
 3 fibro-osseous canals to house and protect the important3 fibro-osseous canals to house and protect the important
neurovascular elements of the lumbar spine are;neurovascular elements of the lumbar spine are;
 The vertebral foramen is formed within the center of theThe vertebral foramen is formed within the center of the
vertebrae,vertebrae,
 Pair of intervertebral foramina are formed laterally betweenPair of intervertebral foramina are formed laterally between
adjacent vertebrae.adjacent vertebrae.

Typical lumbar vertbraeTypical lumbar vertbrae
04/11/2004/11/2066

Trabecular Pattern of Lumbar VertebraeTrabecular Pattern of Lumbar Vertebrae
 Interestingly, the “reinforcedInterestingly, the “reinforced
scaffolding” created by thescaffolding” created by the
alignment of the bony trabeculaealignment of the bony trabeculae
lacks a substantial number oflacks a substantial number of
obliquely orientated trabeculae,obliquely orientated trabeculae,
which results in a poor capacity ofwhich results in a poor capacity of
the lumbar vertebrae to toleratethe lumbar vertebrae to tolerate
rotational stresses. In situ, this isrotational stresses. In situ, this is
compensated for by the IVDs andcompensated for by the IVDs and
posterior bony structures,posterior bony structures,
apophyseal joints as well as byapophyseal joints as well as by
muscular support.muscular support.

NoteNote
 Functionally, the pedicles are the only bony attachment between theFunctionally, the pedicles are the only bony attachment between the
vertebral body and the neural arch and strongly anchor these structuresvertebral body and the neural arch and strongly anchor these structures
to one another. The pedicles are often called upon to sustain highto one another. The pedicles are often called upon to sustain high
compressive and tensile loads that occur during spinal rotation, flexion,compressive and tensile loads that occur during spinal rotation, flexion,
and extension.and extension.

Clinical relevance of Lx SpineClinical relevance of Lx Spine
1. Fractures from compressive loads (wedge compression(wedge compression
fracture) sustained with the spine in flexion or in a midrangefracture) sustained with the spine in flexion or in a midrange
position (lumbar neutral) usually occur in the vertebral bodiesposition (lumbar neutral) usually occur in the vertebral bodies
of the upper lumbar or lower thoracic area. These fracturesof the upper lumbar or lower thoracic area. These fractures
are quite common in persons with osteoporosis and mayare quite common in persons with osteoporosis and may
result from commonly performed activities such as goingresult from commonly performed activities such as going
rapidly from standing to sitting in a chair. These fracturesrapidly from standing to sitting in a chair. These fractures
create a wedge shape of anterior part of vertebral body.create a wedge shape of anterior part of vertebral body.

2. The epiphyseal ring at the superior and inferior portions of the2. The epiphyseal ring at the superior and inferior portions of the
vertebral bodies is an important site of ossification duringvertebral bodies is an important site of ossification during
growth and development. Abnormal ossification here cangrowth and development. Abnormal ossification here can
occur in adolescents and leads to a painful condition knownoccur in adolescents and leads to a painful condition known
as vertebral epiphysitis, or Scheuermann’s disease.as vertebral epiphysitis, or Scheuermann’s disease.
Lx SpineLx Spine 101004/11/2004/11/20

Articular processArticular process
 Arising from the junction of the posterior pedicles and lateral laminae.Arising from the junction of the posterior pedicles and lateral laminae.
2 important articular process present in each vertebrae are superior2 important articular process present in each vertebrae are superior
and inferior articular processes.and inferior articular processes.
 These processes articulate with the opposite articular processes fromThese processes articulate with the opposite articular processes from
adjacent vertebrae (i.e., a superior articular process articulates withadjacent vertebrae (i.e., a superior articular process articulates with
the inferior articular process of the vertebra above it).the inferior articular process of the vertebra above it).
Lx SpineLx Spine 111104/11/2004/11/20
The superior articular process is the
larger of the two articular processes. It
projects upward, providing an articular
surface on its medial aspect, thus
forming the outer bony component of the
facet joint.
The inferior articular process projects
downwards and laterally, forming an
inner component of the facet joint

Facet jointsFacet joints
 Facet joint act asFacet joint act as load bearersload bearers of lumbar spine, resist anterior shearof lumbar spine, resist anterior shear
forces, resist torsion, resist compressive forces.forces, resist torsion, resist compressive forces.
 During upright posture, approximately 18–20% of the compressive loadDuring upright posture, approximately 18–20% of the compressive load
acting upon the lumbar spine is exerted at the facets.acting upon the lumbar spine is exerted at the facets.
 With increased lordosisWith increased lordosis
 Center of gravity shifts posteriorlyCenter of gravity shifts posteriorly
 Produces an extension moment on the lumbar spine and increasing theProduces an extension moment on the lumbar spine and increasing the
load on the lumbar facets.load on the lumbar facets.
 A decreased lordosis shifts the center of gravity of the head, arms, andA decreased lordosis shifts the center of gravity of the head, arms, and
trunk anteriorly and shifts the load to the vertebral bodies andtrunk anteriorly and shifts the load to the vertebral bodies and
intervertebral joints.intervertebral joints.
Lx SpineLx Spine 121204/11/2004/11/20

Clinical RelevanceClinical Relevance
 The capsules of the lumbar facet joints often have fibroadipose,The capsules of the lumbar facet joints often have fibroadipose,
meniscoid inclusions which are quite small and are typically locatedmeniscoid inclusions which are quite small and are typically located
near the periphery of the joint.near the periphery of the joint.
 Because the facet joint is a synovial-type joint, it is subjected to aBecause the facet joint is a synovial-type joint, it is subjected to a
variety of arthritic and synoviolytic disorders such as osteo- andvariety of arthritic and synoviolytic disorders such as osteo- and
rheumatoid arthritis.rheumatoid arthritis.
Lx SpineLx Spine 131304/11/2004/11/20

NOTENOTE
 The thick bone of the superior articular process is critical in
resisting lumbar rotation and, by doing so, protecting the
IVD from excessive torsional stress [13].
 In the lumbar spine, the facet joint planes lie roughly parallel
to the sagittal plane; thus movements in this plane (flexion
and extension) have larger excursions than movements in
the transverse plane (lumbar rotation) or frontal plane (lumbar
sidebending) [50,69].
Lx SpineLx Spine 141404/11/2004/11/20

 Between the superior and inferior articular processes is a relatively
flat isthmus of bone known as the pars interarticularis.
 Clinically, this area is of great importance, as it is often the site of
bone failure during excessive or repetitive lumbar extension and/or
rotation.
Lx SpineLx Spine 151504/11/2004/11/20
•Fractures in this area are called
spondylolysis and are visible on
plane film oblique radiographs. In
some cases, bilateral spondylolysis
can occur.
•This can result in anterior slippage
of the lumbar vertebra known as
spondylolisthesis, or posterior
slippage of lumbar vertebrae called
retrolesthesis.

Spinous and Transverse ProcessesSpinous and Transverse Processes
 The spinous process: It is the point of attachment of theThe spinous process: It is the point of attachment of the
interspinous ligament, and posteriorly it provides an enhancedinterspinous ligament, and posteriorly it provides an enhanced
moment arm for the attachment of the thoracolumbar fasciamoment arm for the attachment of the thoracolumbar fascia
(TLF) and the multifidus muscle.(TLF) and the multifidus muscle.
 Transverse Process: The widest transverse processes (anTransverse Process: The widest transverse processes (an
important radiographic landmark) are found on the thirdimportant radiographic landmark) are found on the third
lumbar vertebra and the thickest are part of the fifth lumbarlumbar vertebra and the thickest are part of the fifth lumbar
vertebra. Several structures that provide stability in the frontalvertebra. Several structures that provide stability in the frontal
plane have attachments to the transverse processes, includingplane have attachments to the transverse processes, including
the quadratus lumborum muscle, fibers from the TLF, and thethe quadratus lumborum muscle, fibers from the TLF, and the
iliolumbar ligaments.iliolumbar ligaments.
Lx SpineLx Spine 161604/11/2004/11/20

Vertebral ForaminaVertebral Foramina
 Of critical importance are the three fibro-osseous passageways withinOf critical importance are the three fibro-osseous passageways within
the bony lumbar spine.the bony lumbar spine.
 Clinical importance: The lateral portion of the vertebral foramen justClinical importance: The lateral portion of the vertebral foramen just
medial to the intervertebral foramen are known as themedial to the intervertebral foramen are known as the laterallateral
recessesrecesses and are a common location forand are a common location for nerve entrapment by discnerve entrapment by disc
herniation.herniation.
Lx SpineLx Spine 171704/11/2004/11/20
Level of
Vertebrae
AP
diameter
Transverse
Diameter
L1 16mm 21mm
L3 15mm 22mm
S1 13mm 30mm
Dommisse et al reported certain
representative values for the
diameters of vertebrae in AP and
Transverse direction
In normal subjects, there is an approximately 10% increase in the area of
the vertebral foramen during flexion and a 10% decrease during
extension

 Panjabi et al. [49] compare the size and shape of the intervertebralPanjabi et al. [49] compare the size and shape of the intervertebral
foramina in normal and degenerative motion segments (i.e., twoforamina in normal and degenerative motion segments (i.e., two
adjacent vertebra). The authors report a 20% decrease in the area duringadjacent vertebra). The authors report a 20% decrease in the area during
lumbar extension and a 30% increase during lumbar flexion.lumbar extension and a 30% increase during lumbar flexion.
 Hasue [22] and Mayoux Benhamou [38] describe the intervertebralHasue [22] and Mayoux Benhamou [38] describe the intervertebral
foramen as pearshaped in flexion and triangular in extension.foramen as pearshaped in flexion and triangular in extension.
 In a recent study, only 4 of 408 subjects with presumed nerveIn a recent study, only 4 of 408 subjects with presumed nerve
compression had evidence of compression in the intervertebral foramencompression had evidence of compression in the intervertebral foramen
[9]. However, a very large number of these individuals demonstrated[9]. However, a very large number of these individuals demonstrated
compression in the lateral portion of the vertebral foramen, the areacompression in the lateral portion of the vertebral foramen, the area
known as the lateral recess.known as the lateral recess. Lx SpineLx Spine 181804/11/2004/11/20

Ligaments of LSLigaments of LS
04/11/2004/11/201919

Ligament name Action opposed by it
ALL separation of anterior vertebral bodies (e.g.,
lumbar extension, anterior bowing of the lumbar
spine
PLL Separation of posterior vertebral bodies(e .g:
lumbar flexion)
Supraspinous Separation of the spinous process(e .g: lumbar
flexion, rotation)
Ligamentum
Flavum
Separation of the laminae
Interspinous Separation of posterior vertebral bodies, i.e.
lumbar flexion, posterior translation of superior
vertebral bodies
Intertransverse Separation of transverse processes i. e .
Iliolumbar Flexion, extension, rotation, and lateral
bending Lx SpineLx Spine 202004/11/2004/11/20

Thoracolumbar FasciaThoracolumbar Fascia
 A complex array of dense connective tissue covering the lumbarA complex array of dense connective tissue covering the lumbar
region, providing critical support to the spine during lumbar flexionregion, providing critical support to the spine during lumbar flexion
and lifting activities.and lifting activities.
 Anatomically it consists of three layers:Anatomically it consists of three layers:
 The anteriorThe anterior
 MiddleMiddle
 Posterior layersPosterior layers
Lx SpineLx Spine 212104/11/2004/11/20

 *Anterior and middle layers arise from the transverse processes of the
lumbar vertebrae: encompases: quadratus lumborum while blending with
the fascia of the transversus abdominis and internal oblique abdominis
muscles.
Clinical importance:
 ‘’The connection of the TLF to the anterior abdominal structures via
qudratus lumborum leads to formation of direct connection between the
bony spine and the deep abdominal muscles and appears to be an important
relationship for the dynamic stabilization of the lumbar spine.’’
 The large posterior layer of the TLF arises from the spinous processes of
the thoracic, lumbar, and sacral vertebrae and covers the erector spinae
muscles: blends with
 Laterally: latissimus dorsi muscle
 Inferiorly: gluteus maximus muscle
 Thus, forms a direct connection between the proximal humerus (the distal
attachment of the latissimus dorsi) and proximal femur (distal attachment of
the gluteus maximus muscle).
Lx SpineLx Spine 222204/11/2004/11/20

 The capsules of the lumbar facet joints often have fibroadipose,The capsules of the lumbar facet joints often have fibroadipose,
meniscoid inclusions [67]. These structures are quite small and aremeniscoid inclusions [67]. These structures are quite small and are
typically located near the periphery of the joint. A common clinicaltypically located near the periphery of the joint. A common clinical
hypothesis is that entrapment of these meniscoid inclusions canhypothesis is that entrapment of these meniscoid inclusions can
occur with certain sudden, unguarded motions, resulting in painful,occur with certain sudden, unguarded motions, resulting in painful,
limited range of motion (ROM), eliciting exclamations such as, “Ilimited range of motion (ROM), eliciting exclamations such as, “I
just threw my back out!” Anecdotally, patients with such episodesjust threw my back out!” Anecdotally, patients with such episodes
often have rapid relief of symptoms following spinal manipulation.often have rapid relief of symptoms following spinal manipulation.
 Because the facet joint is a synovial-type joint, it is subjected to aBecause the facet joint is a synovial-type joint, it is subjected to a
variety of arthritic and synoviolytic disorders such as osteo- andvariety of arthritic and synoviolytic disorders such as osteo- and
rheumatoid arthritis. Although degenerative changes of the facetrheumatoid arthritis. Although degenerative changes of the facet
joint are frequently visualized on radiographs, the relationship ofjoint are frequently visualized on radiographs, the relationship of
these findings to pain is uncertain [72].these findings to pain is uncertain [72].
Lx SpineLx Spine 232304/11/2004/11/20

Intervetebral jointsIntervetebral joints
 The intervertebral, or interbody, joint is a symphysis-type
articulation that joins two adjacent vertebral bodies. Its primary
components are the superior and inferior surfaces of the vertebral
bodies, the vertebral endplates, and the IVD The intervertebral joint
serves the critical function of providing a mechanism for motion and
load bearing between the vertebrae.
Lx SpineLx Spine 242404/11/2004/11/20

Vertebral End platesVertebral End plates
 The vertebral endplate is a flat structure composed of hyaline and
fibrocartilage that is approximately 0.6–1.0 mm thick.
 Acts as boundary between IVD and vertebrae.
 The endplate is more strongly bound to the disc than to the vertebral
body; thus certain types of trauma can tear the endplate away from
the bone.
Lx SpineLx Spine 252504/11/2004/11/20

 Nucleus pulposus: represents the
inner portion of the IVD.
 Histologically=
mucopolysaccharide.
[composition= approximately
70–90% water+ dry weight]
[dry weight composition= 65%
proteoglycans, approximately
20% of which is collagen +
elastic fibers and various
proteins]
Lx SpineLx Spine 262604/11/2004/11/20
 Annulus Fibrosis: represents the
outer portion of the IVD.
 composed of rings of
fibrocartilage forming the outer
portion of the IVD. Taylor
describes the typical lumbar
anulus fibrosis as consisting of
between 10 and 20 layers of
collagen fibers that are obliquely
oriented to one another.
When viewed on the transverse
plane, the IVD has a noticeable
concavity in its central, posterior
portion. This concavity increases
the amount of anulus fibrosus
material posteriorly, in order to
resist the flexion loads common in
daily activities.
IVDIVD

 The posterior longitudinal ligament also reinforces the posterior anulus;
however, the posterior–lateral portion of the anulus is not as well reinforced.
This contributes to the predominance of posterior and posterior–lateral disc
herniations. ALL is 4 times stronger than PLL. And hence resistance
provided by ALL is anytime greater than PLL, which leads to common
posterior displacement of the disc.
 Proteoglycans play a very important role in load bearing. Once the person
stands, load distribution takes place in entire spine, including the IVD. The
proteoglycans on bearing load, swells absorbing water. And once the load is
removed, they return back to the normal position. Once the age advances,
number of proteoglycans reduce and hence load bearing capacity of the spine
decreases, this leads to increase in the load bearing by the lumbar vertebrae
which therefore leads to degenerative changes, causing LBA.Lx SpineLx Spine 272704/11/2004/11/20

 Considering the diurnal variations in the disc, Snook et al. [61]Considering the diurnal variations in the disc, Snook et al. [61]
describe a randomized clinical trial on persons with chronic low backdescribe a randomized clinical trial on persons with chronic low back
pain. Noting that most lifting injuries to the low back occurred in thepain. Noting that most lifting injuries to the low back occurred in the
morning, the authors postulated that flexion avoidance in the morningmorning, the authors postulated that flexion avoidance in the morning
might help to reduce pain. In their study, one group of persons withmight help to reduce pain. In their study, one group of persons with
low back pain avoided early morning lumbar flexion and had muchlow back pain avoided early morning lumbar flexion and had much
better outcomes than a second group that performed stretchingbetter outcomes than a second group that performed stretching
exercises in the early morning. The authors suggest that the elevatedexercises in the early morning. The authors suggest that the elevated
disc fluid volume early in the morning predisposed the disc to injurydisc fluid volume early in the morning predisposed the disc to injury
during lumbar flexion. This is an intriguing finding and may haveduring lumbar flexion. This is an intriguing finding and may have
implications for instruction to patients performing exercises for lowimplications for instruction to patients performing exercises for low
back pain.back pain.
Lx SpineLx Spine 282804/11/2004/11/20

Mechanical properties of IVDMechanical properties of IVD
 The basic external stresses acting upon the IVD can be classified as
compression and tension, bending and rotation.
1. Compression: forces that tend to approximate vertebral bodies
compromise of compression load.
 Vertical Compression Load applied on the IVD
 Pressure within nucleus pulposus increases
 But nucleus pulposus being water content, and water is
incompressible, pressure is distributed to annulus fibrosis
 Circumferential distribution of load to annulus fibrosis= radial
expansion.
 Some of the forces is also transmitted to the next vertebrae through
vertebral end plates.
Lx SpineLx Spine 292904/11/2004/11/20

 Hoop stressHoop stress: The phenomenon by: The phenomenon by
which disc transfers thesewhich disc transfers these
compression loads by convertingcompression loads by converting
vertically applied compression intovertically applied compression into
circumferentially applied tension iscircumferentially applied tension is
called so.called so.
 Pascal’s lawPascal’s law: pressure applied to a: pressure applied to a
liquid is distributed equally in allliquid is distributed equally in all
directions.directions.
Lx SpineLx Spine 303004/11/2004/11/20

Dynamic flexibility to the IVD and the capacity forDynamic flexibility to the IVD and the capacity for
viscoelastic behavior:viscoelastic behavior:
 Once the load is applied on the IVD, IVD hasOnce the load is applied on the IVD, IVD has ability to storeability to store
energy and recoil elastically once the load is released.energy and recoil elastically once the load is released.
 This mechanism is critical to the loadThis mechanism is critical to the load-bearing capacity-bearing capacity of theof the
motion segment and the ability of trabecular bone in the vertebralmotion segment and the ability of trabecular bone in the vertebral
body to function as a shock absorber.body to function as a shock absorber.
 This may beThis may be due todue to presence ofpresence of elastic fiberselastic fibers, in the nucleus, in the nucleus
pulposus and annulus fibrosis which implies the nature of dynamicpulposus and annulus fibrosis which implies the nature of dynamic
flexibility of the IVD and also the viscoelastic properties.flexibility of the IVD and also the viscoelastic properties.
Lx SpineLx Spine 313104/11/2004/11/20

 2. Bending: In 1935, Steindler stated that, nucleus pulposus deforms
in the opposite direction to the movement occurring in the sagital
and frontal plane motions. That is during extension, nucleus
pulposus moves anteriorly and during flexion, nucleus pulposus
moves posteriorly.
Lx SpineLx Spine 323204/11/2004/11/20

 White and Panjabi pointed out that during bending, the anulus
fibrosus is compressed on the side to which the subject bends. For
example, the posterior portion of the IVD is compressed during
extension but is exposed to tensile loading on the opposite side (Fig.
32.15). Therefore, with lumbar extension, a posterior bulging of the
anulus fibrosus and nucleus pulposus may be present, especially in
patients with degenerative IVDs. The clinical significance of this is
unknown.
Lx SpineLx Spine 333304/11/2004/11/20

DEFORMATION OF THE NUCLEUS PULPOSUS AS A BASISDEFORMATION OF THE NUCLEUS PULPOSUS AS A BASIS
FOR BACK EXERCISESFOR BACK EXERCISES
 The deformation of the nucleus pulposus during lumbar motionThe deformation of the nucleus pulposus during lumbar motion
forms the basis for the repeated prone press-up exercises advocatedforms the basis for the repeated prone press-up exercises advocated
by McKenzie.by McKenzie.
 McKenzie’s hypothesis is that as a patient flexes his or her lumbarMcKenzie’s hypothesis is that as a patient flexes his or her lumbar
spine, the nucleus pulposus displaces posteriorly, while duringspine, the nucleus pulposus displaces posteriorly, while during
lumbar extension, it displaces anteriorly, away from the pain-lumbar extension, it displaces anteriorly, away from the pain-
sensitive structures in the vertebral and intervertebral foramina.sensitive structures in the vertebral and intervertebral foramina.
Thus exercises and postures are prescribed to influence the positionThus exercises and postures are prescribed to influence the position
of the IVD thus reducing the pain.of the IVD thus reducing the pain.
Lx SpineLx Spine 343404/11/2004/11/20

3. Rotation: IVD can tolerate torsional (rotation) stress to a very lesser
extent.
 Orientation of the fibers in the anulous fibers being oblique, when a
person rotates to one side, the side to which the rotation is
performed is lax, and the side opposite to it the fibers of nucleus
pulposus are under tension.
 Fortunately, the rotation is resisted by facet joint, more than that of
annulus fibrosis.
 This mechanism is significantly reduced when the spine is in
flexion.
 Thus common mechanism of disc injury is forward flexion and
rotation to any one side.
Lx SpineLx Spine 353504/11/2004/11/20

Muscles of LSMuscles of LS
04/11/2004/11/203636

Bogduk partitionBogduk partition
 The lumbar and thoracic portions of logissimus and iliocostalis muscles into:
1. longissimus thoracis pars lumborum
2. logissimus thoracis pars thoracis and
3. iliocostalis lumborum pars lumborum and
4. iliocostalis lumborum pars thoracis.
Lx SpineLx Spine 373704/11/2004/11/20
• Thoracic section of muscle contain 75% of
slow twitch fibers, whereas the lumbar
section of muscle contain mixed fibers.
Further, line of action over the lower
thoracic and lumbar region is very
superficial, such that forces in these
muscles have the greatest possible
moment arm and, therefore, produce the
greatest amount of extensor moment with
a minimum of compressive penalty to the
spine.
• Thoracic section of muscle contain 75% of
slow twitch fibers, whereas the lumbar
section of muscle contain mixed fibers.
Further, line of action over the lower
thoracic and lumbar region is very
superficial, such that forces in these
muscles have the greatest possible
moment arm and, therefore, produce the
greatest amount of extensor moment with
a minimum of compressive penalty to the
spine.

Multifidus MuscleMultifidus Muscle
 Line of action of mulitfidus tends toLine of action of mulitfidus tends to
be parallel to the compressive axis, inbe parallel to the compressive axis, in
some cases, runs anteriorly andsome cases, runs anteriorly and
caudally in an oblique direction.caudally in an oblique direction.
 Major mechanically relevant featureMajor mechanically relevant feature
of the multifidus is that since theyof the multifidus is that since they
span only a few joints, their forcesspan only a few joints, their forces
only affect local areas of the spine.only affect local areas of the spine.
 Therefore, the multifidus muscles areTherefore, the multifidus muscles are
involved in producing extensor torqueinvolved in producing extensor torque
(together with very small amounts of(together with very small amounts of
twisting and side-bending torque) buttwisting and side-bending torque) but
only provide the ability for correctionsonly provide the ability for corrections
or moment support at specific jointsor moment support at specific joints
that may be foci of stresses.that may be foci of stresses.
Lx SpineLx Spine 383804/11/2004/11/20

 The thoracic extensors (longissimus thoracis pars thoracis and
iliocostalis lumborum pars thoracis) that attach in the thoracic
region are the most efficient lumbar extensors, since they have the
largest moment arms as they course over the lumbar region.
Training of the lumbar extensor mechanism( logissimus thoracis par
thoracis and iliocostalis lumborum pars thoracis) must involve the
extensors that attach to the thoracic vertebrae, whose bulk of
contractile fibers lie in the thoracic region but whose tendons pass
over the lumbar region and have the greatest mechanical advantage
of all lumbar muscles. Thus, exercises to “isolate” the lumbar
muscles cannot be justified from either an anatomical basis or a
motor control perspective in which all “players in the orchestra”
must be challenged during training.
Lx SpineLx Spine 393904/11/2004/11/20

 While the lumbar sections of the longissimus and iliocostalis
muscles that attach to the lumbar vertebrae create extensor torque,
they also produce large posterior shear forces to support the shearing
loads that develop during torso flexion postures. Some therapists
unknowingly disable these shear force protectors by having patients
fully flex their spines during exercises, creating myoelectric
quiescence in these muscles, or by recommending the subject
maintain a posterior pelvic tilt during flexion activities such as
lifting.
Lx SpineLx Spine 404004/11/2004/11/20

BIOMECHANICS andBIOMECHANICS and
PATHOMECHANICSPATHOMECHANICS
 KINEMATICSKINEMATICS
Motion occuring at the lumbar spine is critical to aMotion occuring at the lumbar spine is critical to a
person’s ability to perform the numerous tasks of dailyperson’s ability to perform the numerous tasks of daily
living.living.
Lumbar motion can range from very small displacementsLumbar motion can range from very small displacements
during loading to a very large arcs of motion that occurduring loading to a very large arcs of motion that occur
with bending and reaching tasks .with bending and reaching tasks .
04/11/2004/11/204141

Movements available in lumbar spine :Movements available in lumbar spine :
 FlexionFlexion
 ExtensionExtension
 Lateral flexionLateral flexion
 RotationRotation
04/11/2004/11/204242

Joint coupling occurs when two motions are linked together andJoint coupling occurs when two motions are linked together and
one cannot occur without the other.one cannot occur without the other.
For example, lateral bending is limited in L5-S1 by bonyFor example, lateral bending is limited in L5-S1 by bony
geometry and tension in the iliolumbar ligament.Side bendinggeometry and tension in the iliolumbar ligament.Side bending
cannot occur without some lumbar rotation and vice-versa.cannot occur without some lumbar rotation and vice-versa.
JOINT COUPLINGJOINT COUPLING
04/11/2004/11/204343
Flexion Side flexion Same side rotation
Extension Side flexion Opposite side rotation

It is the kinematic relationshipIt is the kinematic relationship
between the lumbar spine and hipbetween the lumbar spine and hip
joints during sagittal plane movement .joints during sagittal plane movement .
The activity of bending over to touchThe activity of bending over to touch
one’s toes with knees straight dependsone’s toes with knees straight depends
on lumbo-pelvic rhythm.on lumbo-pelvic rhythm.
Initiation of Lumbar bending overInitiation of Lumbar bending over
hips is by Erector spinae till 40 degreeships is by Erector spinae till 40 degrees
and carried forward by Iliopsaos alongand carried forward by Iliopsaos along
with rectus abdomins.with rectus abdomins.
Starigtning up of Lumbar spine backStarigtning up of Lumbar spine back
to neutral occurs by Gluteus maximusto neutral occurs by Gluteus maximus
and then by Erector spinaeand then by Erector spinae
LUMBO -PELVIC RHYTHMLUMBO -PELVIC RHYTHM
04/11/2004/11/204444

Ipsi-directional LPRIpsi-directional LPR ––
when pelvis and lumbarwhen pelvis and lumbar
spine move in samespine move in same
direction; useful fordirection; useful for
activities such asactivities such as
extending the reachingextending the reaching
capacity of the uppercapacity of the upper
extremities.extremities.
Contra-directional LPRContra-directional LPR ––
when the pelvis and thewhen the pelvis and the
lumbar spine move inlumbar spine move in
opposite directions; seenopposite directions; seen
in walking, dancing, orin walking, dancing, or
any other activity in whichany other activity in which
the position of thethe position of the
supralumbar trunk mustsupralumbar trunk must
be held fixed.be held fixed.
04/11/2004/11/204545

Inclination of trunk in forward directionInclination of trunk in forward direction
Flattening of lumbar lordosisFlattening of lumbar lordosis
Achievement of full lumbar flexionAchievement of full lumbar flexion
Anterior pelvic rotationAnterior pelvic rotation
SEQUENCE IN LUMBOPELVICSEQUENCE IN LUMBOPELVIC
RHYTHMRHYTHM
04/11/2004/11/204646

It is relaxation response attained byIt is relaxation response attained by
erector spinae at complete trunkerector spinae at complete trunk
flexion.flexion.
This is a normal response: the trunkThis is a normal response: the trunk
on attaining complete flexion; puts anon attaining complete flexion; puts an
eccentric stretch on erector spinaeeccentric stretch on erector spinae
which should generally deactivate it.which should generally deactivate it.
But, in subjects with Low back acheBut, in subjects with Low back ache
due to spasm of erector spinae or itsdue to spasm of erector spinae or its
tightness; lead to contraction responsetightness; lead to contraction response
of the muscle seen during maximumof the muscle seen during maximum
limit of the flexion of trunk.limit of the flexion of trunk.
Hence this is an important outcomeHence this is an important outcome
measure to check the activity of erectormeasure to check the activity of erector
spinae during flexionspinae during flexion
FLEXION-RELAXATION RESPONSEFLEXION-RELAXATION RESPONSE
04/11/2004/11/204747

Compression:Compression:
Primary function of thePrimary function of the
lumbar spine to providelumbar spine to provide
support for the weight of thesupport for the weight of the
upper part of the body inupper part of the body in
static as well as in dynamicstatic as well as in dynamic
situations.situations.
Studies have shown 10Studies have shown 10
cadever spine subjected tocadever spine subjected to
1000N load demonstrated1000N load demonstrated
that the lumbar interbodythat the lumbar interbody
joints shared 80% of the loadjoints shared 80% of the load
and zygoapophyseal facetand zygoapophyseal facet
joints shared 20% of the totaljoints shared 20% of the total
load.load.
KINETICSKINETICS
04/11/2004/11/204848

Shear:Shear:
In the upright standingIn the upright standing
position, the lumbar segmentsposition, the lumbar segments
are subjected to anteriorare subjected to anterior
shear forces cause by lordoticshear forces cause by lordotic
position, the body weight andposition, the body weight and
ground reaction forces.ground reaction forces.
04/11/2004/11/204949

NEUTRAL LUMBAR SPINENEUTRAL LUMBAR SPINE HYPERLORDOTIC LUMBAR SPINEHYPERLORDOTIC LUMBAR SPINE

Angles of Lumbar SpineAngles of Lumbar Spine
Lx SpineLx Spine 515104/11/2004/11/20

Lx SpineLx Spine 525204/11/2004/11/20

PATHOMECHANICSPATHOMECHANICS
 LumbarizationLumbarization
 SacralizationSacralization
 Facet joint arthropathyFacet joint arthropathy
 Facet tropismFacet tropism
 PIVD: Phases, StagesPIVD: Phases, Stages
 StenosisStenosis
 Sheurmann’s diseaseSheurmann’s disease
 Ligamentum flavum hypertrophyLigamentum flavum hypertrophy
 Bony outgrowthsBony outgrowths
 Spondylo: -sis, -lysis and lesthesis,
 Anklysoing spondylitis
Lx SpineLx Spine 535304/11/2004/11/20

Lumbaraization SacralizationLumbaraization Sacralization
Occasionally theOccasionally the
junction between thejunction between the
first and secondfirst and second
sacral vertebrae failssacral vertebrae fails
to fuse creating ato fuse creating a
condition known ascondition known as
lumbarizationlumbarization whichwhich
results in six mobileresults in six mobile
lumbar vertebrae.lumbar vertebrae.
Lx SpineLx Spine 545404/11/2004/11/20
Wheres in someWheres in some
cases lumbosacralcases lumbosacral
junction fuses duringjunction fuses during
growth andgrowth and
development resultingdevelopment resulting
inin sacralizationsacralization of L5of L5
and results in fourand results in four
mobile lumbarmobile lumbar
vertebrae.vertebrae.

Facet joint arthropathyFacet joint arthropathy
Lx SpineLx Spine 555504/11/2004/11/20

Facet tropismFacet tropism
 Facet tropism:Facet tropism: the angularthe angular
asymmetry between the leftasymmetry between the left
and right and right facetfacet joint joint
orientation.orientation.
 Causes: discCauses: disc
degeneration, degeneration, facetfacet degener degener
ation and degenerativeation and degenerative
spondylolisthesis in thespondylolisthesis in the
lumbar spinelumbar spine
Lx SpineLx Spine 565604/11/2004/11/20

PIVD: PHASESPIVD: PHASES
Lx SpineLx Spine 575704/11/2004/11/20
1. Stage of Dysfunction: Where
due to acute trauma or lesion
in the muscles, muscles adapt
to a shortened position
leading to dysfunction
between them
2. Instability: this dysfunction
will lead to less load bearing
capacity by the muscles,
hence the spine becomes
instable
3. Re-stabilization: this occurs
due to ligament calcification
as now, the load is borne by
ligaments
1. Stage of Dysfunction: Where
due to acute trauma or lesion
in the muscles, muscles adapt
to a shortened position
leading to dysfunction
between them
2. Instability: this dysfunction
will lead to less load bearing
capacity by the muscles,
hence the spine becomes
instable
3. Re-stabilization: this occurs
due to ligament calcification
as now, the load is borne by
ligaments

PIVD: STAGESPIVD: STAGES
04/11/2004/11/205858
1. Disc Bulging: the nucleus
stays within the annulus but
causes dent over the annulus
2. Protrusion: there is complete
bulging out of the nucleus but
the parent contact is still
maintained and the bulging
dents on PCL
3. Extrusion: tear of annulus,
but the contact is maintained
with parent nucleus
4. Sequestration: loss of contact
with the parent nuclues
1. Disc Bulging: the nucleus
stays within the annulus but
causes dent over the annulus
2. Protrusion: there is complete
bulging out of the nucleus but
the parent contact is still
maintained and the bulging
dents on PCL
3. Extrusion: tear of annulus,
but the contact is maintained
with parent nucleus
4. Sequestration: loss of contact
with the parent nuclues

StenosisStenosis
Lx SpineLx Spine 595904/11/2004/11/20
1. Lateral stenosis: caused by the impingement of the nerve rootlet exiting the
foramen within the lateral recess
2. Central stenosis: caused by impingement of the central spinal canal
3. Foraminal stenosis: caused by impingement of nerve rootlet at the lateral
foraminal site.

Scheurmann’s diseaseScheurmann’s disease
Lx SpineLx Spine 606004/11/2004/11/20
Scheuermann's disease describes a condition where the vertebrae grow
unevenly with respect to the sagittal plane; that is, the posterior angle is
often greater than the anterior
Scheuermann's disease describes a condition where the vertebrae grow
unevenly with respect to the sagittal plane; that is, the posterior angle is
often greater than the anterior

Ligamantum Flavum HypertrophyLigamantum Flavum Hypertrophy
 Occurring due to thickening of the ligamentum flavum due
to disc bulge or any other irritation. This may cause central
canal stenosis. Lx SpineLx Spine 616104/11/2004/11/20

BonyBony
outgrowths ofoutgrowths of
spinespine
Lx SpineLx Spine 626204/11/2004/11/20

SpondylosisSpondylosis
Lx SpineLx Spine 636304/11/2004/11/20
Inflammation of the disc leading to irritation of the cartilage
thus causing pain

SpondylolysisSpondylolysis
Lx SpineLx Spine 646404/11/2004/11/20
Break in Pars inter-articularis

SpondylolesthesisSpondylolesthesis
Lx SpineLx Spine 656504/11/2004/11/20
SpondyloptosisSpondyloptosis
Slippage of the
vertebrae front of the
succeeding vertebrae
Has 5 grades
Spondyloptosis: Vertebrae falling
ahead of the succeeding vertebare

Ankylosing SpondylitisAnkylosing Spondylitis
Lx SpineLx Spine 666604/11/2004/11/20
1. An inflammatroy disease
of the spine caused due to
DNA mutation: HLA-B27
2. Usually starts from
Sacroiliac joint and travels
up towards cervical
3. Has a bamboo spine
appearance on X-ray

THANK
YOU!!!
04/11/2004/11/20 6767Lx SpineLx Spine

Lumbar Spnine: Anatomy, Biomechanics and Pathomechanics

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Lumbar Spnine: Anatomy, Biomechanics and Pathomechanics

Similar to Lumbar Spnine: Anatomy, Biomechanics and Pathomechanics (20)

More from Radhika Chintamani

More from Radhika Chintamani (20)

Recently uploaded

Recently uploaded (20)

Lumbar Spnine: Anatomy, Biomechanics and Pathomechanics