anatomy of lumbar spine, biomechanics of lumbar spine, movements at lumbar region, muscles of lumbar region, lumbar vertebra, kinetics and kinematics of lumbar spine

1. Shalu Thariwal
Biomechanics of
Lumbar spine

2. Anatomy of lumbar spine
 5 lumbar vertebrae
 Body(massive, transverse diameter is greater)
 Arches
 Pedicles(short, thick, project posterolaterally)
 Laminae(short and broad)
 Zygapophyseal articular process
 Transverse process(long, extends horizontally)
 Spinous process(broad, thick, horizontally)
 Vertebral foramina(triangular)

3. Lumbar

6. Lumbar vertebral joints
 The mobility of the vertebral column is provided by the symphyseal
joints between the vertebral bodies, formed by a layer of hyaline
cartilage on each vertebral body and an intervertebral disc between the
layers.
 The synovial joints between the superior and inferior articular processes
on adjacent vertebrae are termed the facet joints (also known as
zygapophyseal joints or Z-joints). They permit simple gliding
movements. The movement of the lumbar spine is largely confined to
flexion and extension with a minor degree of rotation. The region
between the superior articular process and the lamina is the pars
interarticularis. A spondylolysis occurs if ossification of the pars
interarticularis fails to occur.
 The 3-joint complex is formed between 2 lumbar vertebrae.
 Joint 1: Disc between 2 vertebral bodies;
 Joint 2: Left facet (zygapophyseal) joint;
 Joint 3: Right facet (zygapophyseal) joint.
 Lumbosacral articulation

7. Ligaments and fascia
 Ligamentum flavum
 Anterior longitudinal ligament
 Posterior longitudinal ligament
 Interspinous
 Supraspinous ligament(only in upper lumbar
region)
 Joint capsules
 Iliolumbar ligaments
 Thoracolumbar fascia

9. 3 column stability

11. Iliolumbar ligaments
 Consists of series of band, extends from tip and
border of L5 transverse processes
 attach bilaterally on the iliac crest
 3 primary bands
a) Dorsal band
b) Ventral band
c) Sacral band

12. Function
 Strong and stabilize L5 vertebra
 Resist flex, ext, axial rotation, and lateral bending
of L5 on S1
 Maximally loaded at Lumbosacral
junction(absence of muscle protection against
flexion)
 Low back pain – when sitting in a relaxed or
slouched posture.

13. Thoracolumbar fascia
 Also known as lumbodorsal fascia
 3 layers
a) Anterior
b) Middle
c) Posterior
 Act as a stabilizing corset, increases spinal
stiffness, mechanical transmission of forces
between pelvis and trunk.

14. Kinematics
 Flexion – 52 degree(sagittal plane )
 Extension-19
 Lateral flexion-30(frontal plane)
 Rotation -30(transverse plane)
Lumbopelvic rhythm

15. Kinematics
 Flexion and extension sagittal plane
orientation of zygapophyseal facets
 Upper lumbar region(most free lateral flexion
and rotation)
largest at L2, L3 level
 Lower lumbar region –flex and ext

16. Motions
Flexion
 Anterior rotation/translation
 IAP up/forward, compression forces on anterior side of
disc tending to migrate nucleus pulposus posteriorly
 Motion limited by: – Ligament/capsule tension – Facet joint
 5°-7°
Extension
 Posterior rotation/translation IAP, Posterior tilting , gliding
of superior vertebra
 IAP moves down/back, nucleus pulposus displaces
anteriorly
 Motion limited by: – Interspinous ligament buckling –
Bony impaction
4°-7°

18. Motions
Rotation
 Closes ipsilateral facet
 Opens contralateral facet Motion limited by:
 Motion limited by: – Facet orientation – Annulus fibrosus
 1°-3°
 Coupled with sidebend
Sidebend(lateral flexion)
 Creates a “extension/flexion” of the facets on the same segment
 Ipsilateral- close
 Contralateral-open, Superior vertebra laterally tilts, rotates and
translates over vertebra below, Annulus fibrosus is compressed
on concavity of curve and stretched on convex side
 2°-5°
 Coupled with rotation

19. Coordinated and simultaneous activity of lumbar
flexion and anterior tilting of the pelvis in the sagittal
plane.
Lumbosacral flexion +anterior tilting of pelvis

20. Kinetics
 Compression
 Shear

21. Compression
 Support the weight of upper part in static as well
as dynamics situations.
 Large lumbar vertebrae –support additional
weight
 Compressive load by muscular contraction
 Interbody joint 80%load,zp facet 20%load
 In ext ,more load on zpp joint

22. Shear
 Anterior shear forces (in upright position) caused
by:
 Lordotic position
 Body weight
 Ground reaction forces
 Superior facets lie in the frontal plane and face
posteriorly.

23. Shear and compression forces

24. Lumbosacral articulation (by 5th L and 1st
S) 1st sacral is inclines ant and inferiorly and forms
an angle horizontal called lumbosacral angle.

25. Muscles of lumbar spine
 Anterior group
 Posterior group
 Lateral group

26. Posterior muscles
 Thoracolumbar fascia
 Superficial erector spinae (logissimus thoracic pars
thoracic, iliocoastalis lumborum pars
thoracic)=extension and assist in ipsilateral side
flexion.
 Deep erector spinae (LTPL,ILPL)=ipsilateral side
flexion, posterior shear, rotation, assist in extension.
 Multifidus (from dorsal sacrum and ilium to the
spinous processes of L)vertically
oriented,extension,control segmental shear and
torsion by producing compression.

27. Lateral muscles
 Quadratus lumborum=act bilaterally ,frontal plane
stabilizer. Unilaterally , lateral flexion.
 Hike the hip
 Intertransversarii and rotators=rotation and lateral
flexion

28. Anterior muscles
 Prime flexor =rectus abdominis
 Abdominal wall=external oblique ,internal
oblique,transversus abdominis
 Psoas majorand ilacus= primary hip flexor
 Role of psoas major :anterior ilial rotation and
thus L extension,provide stability to L spine
during hip flexion by providing great amount of
Lumbar compression+ some anterior shear
forces.