Lx Bones

Question 1

Describe the vertebrae in the lumbar spine

Answer 1

There are 5 lumbar vertebrae

L2-4 are typical lumbar vertebrae
L1 is a transitional vertebrae with the thoracic spine
L5 is a transitional vertebrae with the sacral spine, and the largest vertebrae in the vertebral column

Question 2

What are the features of a typical lumbar vertebrae?

Answer 2

• huge thick body (to support increased body weight loading in the inferior spinal segments)
• kidney shaped body
• large triangular foramen to accommodate Lx plexus
• short fat spinous processes (nearly horizontal)
• long slender transverse processes (nearly lateral)
• articular processes have a sagittal alignment that allows for a large range of motion in the sagittal plane and severely limits rotation

Unique processes:

• mamillary processes (on superior articular facets) provide attachments for multifidi and intertransverse muscles
• accessory processes on base of transverse processes

Question 3

Which processes are unique to the lumbar vertebrae?

Answer 3

Mamillary processes

• on the superior articular facets (posterior surface)
• provide attachment points for the multifidi and intertransversari muscles

Accessory processes
- on base of transverse processes

Question 4

Describe the L1 vertebrae

Answer 4

Transitional vertebrae between the lumbar and thoracic spine

• shape more similar to thoracic vertebrae
• oval shaped foramen
• body more heart shaped
• shorter TPs

Question 5

Describe the L5 vertebrae

Answer 5

• transitional vertebrae between the lumbar and sacral spine
• with the L5 / S1 vertebrae helps to form the lumbosacral angle
• largest of all moveable vertebrae
• body big and wide to articulate with large sacral base
• TPs unite with vertebral body and pedicle
• inferioro facets face anteriorly to meet S1 facets (transition from sagittal plane facet orientation of Lx to coronal plane orientation of Sx)

Question 6

Describe the lumbo-sacral angle

Answer 6

• The articulation between L5 and S1 forms the lumbosacral angle
• angle 130-160 degrees
• point of acute vulnerability to excessive anterior shear forces in the spine
• facet joints of L5/S1 oriented in a more frontal plane than other Lx vertebrae to help resist anterior shear at this joint
• supported by:
• ALL
• articular facets of L5/S1 (bony stability)
• iliolumbar ligament crosses posterior to junction (from sacrum / ilium to TP L5)

Question 7

Review the sacral spine

Answer 7

• composed of 5 fused vertebrae
• sacral base (superior) - large thick base of sacrum for articulation with L5
• sacral canal -continuation of vertebral canal, containing cauda equina
• sacral foramina - 4 pairs of foramina between the vertebrae (anterior and posterior) for exit of anterior and posterior rami of spinal nerves

Functions:

• provides strength and stability to pelvis
• transmits spinal nerves to the pelvis and lower body
• transmits weight of body to pelvic girdle

Question 8

Describe the intervertebral foramina

Answer 8

Formed by the space between the inferior and superior vertebral notches of adjacent vertebrae laterally

Creates a foramen through which the spinal nerves exit the vertebral foramen

Question 9

Review the 7 features of a typical spinal vertebrae including their functions

Answer 9

Body - resists compressive forces and provides structure & height to vertebral column

Pedicles - transmit bending forces to vertebral bodies

Laminae - resist and transmit forces to pedicles, attachment site for muscles and ligaments

Transverse processes - attachment sites for muscles and ligaments

Spinous processes - resist compression and excessive extension, transmit forces to laminae, attachment sites for muscles and ligaments

Zygapophyseal facets - resist shear, compression, tensile and torsional forces, and transmit forces to laminae

IVD - shock absorption and force distribution, resists excessive loading force on the spine, provides height and structure to the vertebral column, resists excessive rotational movement