Biomechanics of the Lumbar Spine

Question 1

What is the most important characteristic of the lumbar spine?

Answer 1

it must bear tremendous loads created by body weight that interact with forces generated by lifting and other activities involving powerful muscle actions

Question 2

The lumbar spine is largely responsible for what?

Answer 2

trunk mobility

Question 3

Describe the anatomy of the facets of the lumbar spine

Answer 3

large
thick
strong

Question 4

L/S inferior articular processes are CONVEX and face what direction?

Answer 4

anterolaterally

Question 5

L/S superior articular processes are CONCAVE and face what direction?

Answer 5

posteromedially

Question 6

In what plane are the L/S facets?

Answer 6

sagittal

Question 7

What occurs to the facets at the lumbosacral junction?

Answer 7

they become more coronal

Question 8

What do the facet configuration of the L/S limit? and allow?

Answer 8

limits: rotational flexibility
allows: for greater mobility in flexion and extension

Question 9

What is the facet configuration of L1-4?

Answer 9

sagittal orientation

limits axial rotation (øy)

Question 10

What is the facet configuration of L5-S1?

Answer 10

coronal orientation

limit posterior/anterior shear (z translation)

Question 11

The lumbar facets normally carry ____% of axial load and up to ____% in extension.

Answer 11

18%

33%

Question 12

What is the primary movement in the Lumbar spine?

Answer 12

Flexion/extension (øx)

Question 13

What % of trunk flex/ext occurs in the L/S?

Answer 13

75%

TWICE as much FLEXION as extension

Question 14

What rotation is limited in the L/S overall due to sagittal facet orientation?

Answer 14

øy Axial rotation

Question 15

Lateral bending in the L/S is coupled with axial rotation; what side does the spinous go to?

Answer 15

ipsilateral (may switch at L4 and L5)

Question 16

Where is the nucleus located in the L/S?

Answer 16

somewhat posteriorly in the disc

Question 17

What is the disc height-to-body height ratio in the L/S?

Answer 17

1:3
(this relationship allows for more movement than T/S, but less movement than C/S and gives the disc greater resistance to axial compressive forces

Question 18

What does the L/S canal contain and protect proximally?

Answer 18

conus medularis

Question 19

What does the L/S cancel contain and protect distally?

Answer 19

cauda equina & spinal nerves distally

Question 20

Where does the spinal cord end?

Answer 20

L2; nerve roots continue down the spinal canal as the cauda equina

Question 21

CNS is tethered to the coccyx by what?

Answer 21

filum terminale

Question 22

NRs exit the dura slightly above the foraminal opening, causing their course to be more ___________ and their length to increase.

Answer 22

oblique

Question 23

When does the secondary lordotic curve of the L/S occur?

Answer 23

starts to develop ~ 9-12 months of age/beginning to sit up. Becomes established as they learn to stand (~18m)

Question 24

Where is the apex of the L/S lordotic curve?

Answer 24

L3-4 disc

Question 25

What should the normal lumbar lordosis angle be?

Answer 25

20-60 degrees

Question 26

Changes in the sacral angle can influence the depth of the ______ curves in the spine.

Answer 26

A-P

Question 27

What happens to the sacral base angle with an anterior pelvic tilt?

Answer 27

increases; resulting in an increase in the lumbar lordosis, which places more weight-bearing responsibility on the facets

Question 28

What happens to the sacral use angle with a posterior pelvic tilt?

Answer 28

decreases; resulting in a decreased lumbar lordosis, placing more weight-bearing responsibly on the disc and a decrease in spines ability to absorb axial compression forces

Question 29

What is the major stabilizer of the L/S?

Answer 29

(QL) Quadratus Lumborum

Question 30

How much is the QL lumborum active? Heavy lifts? isometrical lateral bending holds? standing isometric twists?

Answer 30

74% 54% 42%

Question 31

What are the characteristics of the ALL & PLL of the L/S?

Answer 31

Restricts excessive flex/ext Well developed (ALL>PLL) Attached to the vertebral body and the annulus

Question 32

What are the characteristics of the Ligamentum Flavum in the L/S?

Answer 32

Highly elastic | Acts as a barrier to material that would otherwise encroach on cord during ROM

Question 33

What are the characteristics of the Lumbodorsal Fasica in the L/S?

Answer 33

Attachment for: Transverse Abdominis, internal oblique, lattissimus dorsi Acts like a large extensor retinaculum to constrain long tendons of thoracic and lumbar extensors

Question 34

What are the characteristics of the Interspinous lig in the L/S?

Answer 34

Acts like a collateral lig, controls vertebral rotation to follow an arc through flexion range

Question 35

What are the characteristics of the supraspinous leg in the L/S?

Answer 35

provides resistance against excessive forward flexion

Question 36

What are the characteristics of the facets in the L/S?

Answer 36

Well developed Restricts joint flex Restrics distraction of facet surfaces during axial rotation

Question 37

What is lig damage in the L/S caused by?

Answer 37

joint laxity; joint degeneration follows | ligament damage mark the beginning of the end