Lumbar Spine Anatomy Flashcards
the top and bottom surfaces of the VB are smooth and have perforation holes for …
nutrition
what structure articulates with the disc and holds the end plate in place
ring apophysis
the posterior surface of the VB have large holes for…
nutrient arteries and basovertebral vein
what 2 trabecular systems are in the VB and what is the significance of each?
transverse - resists tension
vertical - resists compression
what is important about having trabeculae systems in the VB?
keep it light
what 4 structures make up the neural arch?
- pedicle
- lamina
- SP
- TP
what forces do the pedicles resist?
bending and tension
what is significant about the accessory or mamillary processes?
provide surface for m attachment (miltifidi)
describe the orientation of the superior facet
concave and faces medially and posteriorly
describe the orientation of the inferior facet
convex and face laterally and anteriorly
what structure sustains bending force from pedicle to lamina
pars interarticularis
what motion is favored by the orientation of the Lumbar facets?
sagittal plane motion - flex/ext
what shape is the VB of L5
wedge
describe the characteristics of the following structures for L5
- disc
- TP
- SP
- Z joint
disc = smaller surface
TP = larger
SP = smaller
Z - joint = orientation in coronal plane
what is the significance of the shape of the L5 VB
it can accommodate for the lumbosacral angle
how many articulations are at each vertebral segment of the lumbar spine
6 articulations
- superior and inferior IV joints (2)
- bilat superior and inferior Z joints (4)
what type of joint is the IV join
cartilagenous
what structure:
- accounts for 25% of total height of vertebral column
- allows mvmt
- absorbs shock and distributes load
IV disc
collagen fibers in the AF are oriented _____ off the vertical line and ______ opposite to each other
60
120 degrees
what forces does the AF resisit
compression, shear and torsion
what forces does the NP resist
compression and shear
what happens to the NP with axial loading
does not deform
reduces in height and expands radially toward AF, end plate and VB
what is the end plate made of
fibrocartilage and hyaline cartilage
what forces does the end plate resist
it is weak when exposed to compression forces
when you have a normal/intact disc, how much force does the z joint carry?
How much is it when the disc is diseased?
normal = 20-25%
diseased = up to 70% force thru the Z joint
how does the IV disc receive nutrients
by diffusion thru cartilagenous end plate
how does the disc receive its nerve supply
peripherally by branches of anterior rami and gray rami communicans
what are the pain sensitive structures surrounding the disc
ALL, PLL, nerve roots, VB, cartilage of z joint
what shape is ideal/normal for the Z joint
C or L (J) shape
how much motion occurs are the Z joint
5-8mm up and down
what is the function of the miltifidi
approximation of the z joint - stabilization
what is the significance of having J shaped z joints
resist anterior shear force on anteromedial aspect of z joint
what is the significance of C and J shaped joints
increases bony congruence = stability
what strucutre reinforces the z joint capsule anteriorly
ligamentum flavum
what position is the z joint capsule tight in?
all positions
what 2 structures reinforce the z joint capsule
miltifidi and lig flavum
what is the function of the fibroadipose meniscoid
protect z joint surface during motion
what happens when the fibroadipose meniscoid malfunctions
becomes buckled/relaxed in flexion and lodged under the capsule –> blocking extension and causing acute locking
where does the z joint get its nerve supply
medial branch of the dorsal root of the same segment and the segment below
how many and what articulations occur at the lumbosacral junction
3 articulations - IV joint and bilat facet joints
what is the normal LS angle
40 deg
describe the incline of S1 at the LS angle
inclines inferiorly and anteriorly forming and angle to horizontal line
what determines the lumbar curve
LS angle
what structures stabilize LS junction anteriorly and posteriorly
ALL and iliolumbar ligaments
where does the L5 VB tend to slide
anteriorly and inferiorly
what counterbalances the translation of L5 on S1
vertebral arch junction b/w superior and inferior facets
if the pars interarticularis breaks =
spondylolysis
if L5 is displaced anteriorly =
spondylolisthesis
what radiographic view can you see spondylolysis
oblique view = broken neck of scottie dog
the ALL has the greatest tensile strength in what region
lumbar region
what forces does the ALL resist
extension or excessive lordosis
what structure is diamond shaped and deviates laterally at disc level to support AF
PLL
why is it significant that the PLL is weak in the lumbar region
high incidence of HNP in this region
what forces does the PLL resist
flexion and traction
the ligamentum flavum extends _____ to cover the ______
laterally to cover the z joints
the ligamentum flavum contains a high % of ________
what does this allow it to do?
- elastin
- able to recoil and not buckle
where is the ligamentum flavum strongest and weakest
stringest - L region
weakest - cervical
what direction dies the lig flavum resist
flexion
slack in ext
what are the posterior ligaments of the vertebral column
interspinous, supraspinous and intertransverse
what direction does the interspinous and supraspinous ligaments resist
hyperflexion
palpable tenderness of the interspinous ligament may indicate…
hypermobility or instability
the supraspinous ligament does not have direct attachment to ______
thoracolumbar fascia at L4 - L5
what motion does the intertransverse ligament resist?
what is its contribution to stability
contralateral flexion
- no contribution to stability - it is just there
what are the 5 bands of the iliolumbar ligament
anterior, superior, inferior, vertical and posterior
what motion does the posterior band of the iliolumbar ligament resist
flexion
what is the function of the posterior band of the iliolumbar ligament
stabilize L5 from anterior displacement and resist lateral flexion at L5
where do the superficial layers of the Thoracolumbar fascia come from
latissimus dorsi
4 functions of thoracolumbar fascia
- m attachment
- resist segmental flexion
- assist in transmission of extension during lifting
** pull of TrA –> increase in tension of fascia –> limit intersegmental flexion and anterior translation
what is the most effect lateral flexors of the trunk
erector spinae
bilateral contraction of erector spinae will create what 3 things
- extend trunk
- tilt pelvis anterior
- increase L lordosis
unilateral contraction of erector spinae will create what 2 motions
- lateral flexion and rotation of trunk to SS
what 3 m groups make up the deep layers of the back m
transversospinal m group = semispinalis, miltifidi, rotatores
what is the “rotator cuff” of the z joint and why is it called that
multifidi - produces compression force during contraction to stabilize joint
pts with segmental instability show what 2 characterisitics of the multifidi
fatty replacement and atrohpy
as a group, the transversosponal muscles do what?
fine control of spinal motions
what does the evidence say about multifidi m recovery after decrease of LBP
m recovery is not automatic
what is one of the biggest findings in pts with LBP
m atrophy of multifidi –> inability to contract
bilateral contraction of the EO m will create…
Unilateral contraction …
bilat - trunk flex, post tilt of pelvis
unilat - I/L trunk lateral flex and C/L rotation
bilat contraction of IO m will create…
unilateral contraction …
bilat - trunk flexion and post tilt pelvis
unilat - I/L tunk lateral flex, I/L rotation
bilat contraction of TrA…
compression of abdominal cavity and increase tension of thoracolumbar fascia
- primary stabilizer
LBP pts failed to recruit _____ and ____ with fast speed arm mvmts
TrA and IO
what is the predominant hip flexor
iliacus
contraction of the psoas will create…
lateral lumbar flexion and vertical stabilization
the iliopsoas creates ________ by tilting the pelvis ______
lumbar lordosis
anteriorly
what characteristics does the iliopsoas present with in a pt with LBP
short (spasm) and atrophied
bilat QL contraction …
Unilat QL contraction …
bilat = extend lumbar
unilat = lateral flex L spine or elevate pelvis
