applied anatomy of lumbar spine

Question 1

function of Lx spine

Answer 1

support / WB
quadrupedal vs bipedal 
mobility 
trunk locomotion 
protect SC and cauda equina

Question 2

spinous process and transverse processes

apophyseal joint

inter body joint

Answer 2

SP and TP :provides levers for muscles and ligs for causing and restricting mvmt and stabilising vertebral column

apo: guides intervertebral motion
inter: absorbs shock and distributes load throughout vertebral column

provide intervertebral stability
serves as approximate site of the axes of rotation for movement
functions as deformable intervertebral spacer

Question 3

IV disc

Answer 3

constituents
WATER
proteoglycans large molecules consisting of polysaccharides linked to proteins: NB for load transfer.
Collagen: Type I & II

Nucleus Pulposus:
70-90% water, 65% proteoglycans, 15-20% collagen
Annulus Fibrosis:
60-70% water, 50-60% collagen, 15% proteoglycan acts as binding in lamellae.
Vertebral End Plate =0.6 – 1mm cartilage layer:
covers NP but not all of AF.
Strongly attached to AF more than VB so can be ripped from VB in trauma.
Provides nutrition to disc.

Question 4

annulus fibrosis orientation

Answer 4

ANGULATION 
50% lamellae restrict left rotation and
other 50% restrict right rotation.

Question 5

IV disc load transmission

Answer 5

sequence 
nucleus radially deviates 
circumferentially under axial pressure 
increases tension in annular fibres 
Annular fibres reach their elastic limit
An inward force is exerted back on NP
NP then exerts downward pressure 
Weight is transmitted to vertebra below & cycle is repeated.

Question 6

spinal nerve

Answer 6

Spinal nerve –
very short usually

Dorsal rami – supply posterior spinal structures

Ventral rami – make up plexi –
L1-4 Lumbar plexus
L4-5 join to lumbo-sacral plexus

Question 7

L5 stability

Answer 7

Iliolumbar ligament – connect TP of L5 to ilia – 5 parts – very important in providing stability for L5 – consider lumbosacral angle. (ave = 16 degrees 6-29)

Question 8

facet joints

Answer 8

Facet / Zygoapophyseal
joints formed by 2
facets covered in thick
articular cartilage.

Minimal weight-bearing –
standing – facets bear
ave. 16% load
(Adams & Hutton 1983)
Capsule:
surrounds dorsal, superior & inferior margins of joint
ligamentum flavum ant.
Nerve supply:
dorsal ramus of spinal nerve. 
Capsules richly invested with mechanoreceptors & nociceptors

Superior articular facets face medially & slightly posteriorly.

Inferior articular facets face laterally & slightly anteriorly.

Orientation in lumbar
spine –>
limits rotation
but allows flex / ext -
WHY?
Intra-articular fibroadipose meniscoids –
Provide protection to articular surfaces when exposed by opening movements
may be implicated in ‘Acute Locked Back’ syndrome

Question 9

Muscles

Answer 9

GLOBAL / SUPERFICIAL
long muscles that attach to thorax and pelvis and function to transfer load and as prime trunk movers.
Multi-segmental
Power - strength

LOCAL / DEEP
attach directly onto lumbar vertebra (uni- or multi-segmental) and function to control lumbar curvature
Segmental stabilisers
Often uni-segmental
Stability – endurance

Global Erector Spinae: 
Longissimus thoracis pars thoracis iliocostalis lumborum pars thoracis
Quadratus lumborum (lateral fibres)
Rectus Abdominus
Internal Oblique
External Oblique

Local Erector Spinae:
Longissimus thoracis pars lumborum iliocostalis lumborum 
Multifidus – deep fibres
Interspinales
Intertransversarii
Quadratus Lumborum (medial fibres)
Transversus Abdominis 
Internal Oblique (via TLF)

Question 10

rotation translation

Answer 10

ROTATION = PHYSIOLOGICAL / OSTEOKINEMATIC MOTION
Force couple
Torque
TRANSLATION = ARTHROKINEMATIC / ACCESSORY GLIDE
Shear force
Nomenclature: cephalad & caudad

Question 11

biomechanics

Answer 11

lumbar flexion extension
side flexion
rotation

Question 12

Stress-strain

Answer 12

STRESS = applied or elongating force is known as stress. Units of force (Newtons)
STRAIN = extent to which a fibre is elongated as a result. Units of length (% increase / decrease vs. initial length)
Tension / tensile strain
Compression strain
Shear strain
Torsion strain - twist

Question 13

stiffness

Answer 13

STIFFNESS
= Resistance to deformation: measured by the force required to produce a unit elongation / deformation
Biologically – greater stiffness – greater bonding between collagen fibres / matrix
Clinically what influences segmental stiffness?

Question 14

lumbar flexion

Answer 14

↑ IV disc pressure – NP posteriorly
Facet joints slide open & gapno-gap
Posterior ligts stretched –
EOR restraints =
rotation: posterior facet jt capsules, ligaments, muscle stretch
translation: facet joints  stabilise segment and protect against shear

Question 15

lumbar extension

Answer 15

↓ IV disc pressure – posterior compression relative to anterior stretch
NP anteriorly
Facet joints slide closed
Anterior ligts stretched:
EOR restraints =
Bony block –
inferior articular processes impact lower face of superior articular processes of vertebra below
+/- spinous processes (depending on interspinous space)

Question 16

lumbar side flexion

Answer 16

CONTRALATERAL

FACET JTS:

LIGTS:

MUSCLE (if active SF):

IPSILATERAL

FACET JTS:

LIGTS:

MUSCLE (if active SF):

Question 17

lumbar rotation

Answer 17

Arrangement of IV disc: AF rings primarily limit torsion strain (50%)
Collagen fibres (AF) if strained > 4% length will sustain damage (>3˚)
IVD resist rotation > flexion
Impaction of facet joints:
(L) rotation: (R) facet joint impacts

1-3˚ total rotation at each segment (total = 11-15˚)