Describe the vertebrae in the lumbar spine
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
What are the features of a typical lumbar vertebrae?
- 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
Which processes are unique to the lumbar vertebrae?
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
Describe the L1 vertebrae
Transitional vertebrae between the lumbar and thoracic spine
- shape more similar to thoracic vertebrae
- oval shaped foramen
- body more heart shaped
- shorter TPs
Describe the L5 vertebrae
- 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)
Describe the lumbo-sacral angle
- 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)
Review the sacral spine
- 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
Describe the intervertebral foramina
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
Review the 7 features of a typical spinal vertebrae including their functions
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
