The document discusses the biomechanics of the lumbar spine. It describes the structure of the lumbar vertebrae including adaptations in the L5 vertebra. Key ligaments that support the lumbar spine are described such as the iliolumbar ligament. The document also discusses lumbopelvic rhythm which is the coordinated movement between the lumbar spine and pelvis during trunk flexion and extension. Finally, the kinematics and kinetics of the lumbar spine are summarized including the compression and shear forces it experiences.

1. BIOMECHANICS
OF LUMBAR
SPINE

2. Topics to be discussed;
 Structure of lumbar spine
 Lumbar articulations
 Ligaments & Fascia
 Lumbopelvic rhythm
 Kinematics of lumbar spine
 Kinetics of lumbar spine

4. Structure of Lumbar spine
 The first four lumbar L1-L4 vertebrae
are similar in structure.
 The fifth lumbar L5 vertebra has
structural adaptations for articulation
with the sacrum.

6. 5TH LUMBAR VERTEBRA
 It is a transitional vertebra:
 involving, providing, or consisting of a
passage, movement, or change from one
state, condition, subject, place, etc., to
another
 L5 has a wedge-shaped body
 The L5/S1 disk also is wedge shaped.
 The superior discal surface area of L5 is
about 5% greater than the areas of discs
at L3 and L4.
 The inferior discal surface area of L5 is
smaller than the discal surface area at
other lumbar levels.
 The spinous process of L5 is smaller than
other lumbar spinous processes
 The transverse processes of L5 are large
and directed superiorly and posteriorly

7. Lumbosacral articulation
 It is formed by the L5 and S1.
 The 1 sacral segment, which is inclined
slightly anteriorly and inferiorly, forms
an angle with the horizontal called the
Lumbosacral Angle.
 An increase in this angle will result in an
increase in lordosis of the lumbar curve.
 Increase the amount of shearing stress at
the lumbosacral joint

8.  ARTICULATION
 Interbody joints
The interbody joints of the lumbar
region are capable of translations
and tilts in all directions.
 Zygapophyseal joints
Allows flexion , extension , rotation
and lateral bending

9. Intertransverse
Ligament
Supraspinous
Ligament
Content Here
Content Here
Ligaments of
the Lumbar
Spine
 Supraspinous ligament is well
developed in upper lumbar
region and may terminate at
L3 and L4.
 The ligament is almost
always absent at L5/S1
 Intertransverse ligaments are
not true ligaments in the
lumbar area and are replaced
by the iliolumbar ligament at
L4.
Iliolumbar
Ligament
 There are three primary bands:
 Ventral (or anterior) band
 Dorsal (or posterior) band
 Sacral band (lumbosacral
ligament)
 The illiolumber ligaments is
very strong and stabilizing the
5 lumbar vertebra (preventing
the vertebra from anterior
displacement)
 resisting flexion, extension,
axial rotation, and lateral
bending of L5 on S1

10. Lumbar Pelvis Rhythm
 It is a specific instance of coordinated,
simultaneous activity of lumbar flexion and
anterior tilting of the pelvis in the sagittal
plane during trunk flexion and extension.
 This combined lumbar and pelvic motion is
lumbar-pelvic rhythm

11. Lumbar Pelvis Rhythm
 Bending over to touch one’s toes with
knees straight
Lumbar flexion followed by anterior
tilting of the pelvis at the hip joints
 Return to the erect posture
Lumber extension
Initiated by posterior tilting of the pelvis at
the hips

12. Kinematics of Lumbar Movements
 Flexion
 Extension
 Lateral flexion
 Rotation (limited by zygapophyseal
joints)

14. Kinetics
Compression:
The increase size of the
lumbar vertebral bodies and
discs in comparison with
their counterparts in the
other regions help the
lumbar structures support
the additional weight.

15. Shear:
In the upright standing position, the
lumbar segments are subjected to anterior
shear forces cause by the lordotic position,
the body weight, and ground reaction
forces. This anterior shear or translation
of the vertebra is resisted by direct
impaction of the inferior zygapophyseal
facets of the superior vertebra against the
superior zygapophyseal facets of the
adjacent vertebra below.

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