Lumbar Spine Ligaments and Muscles Flashcards
Anterior Longitudinal Ligament
- Well developed along lumbar lordosis
- Tensile strength is greatest in lumbar region
- Supports weight of lumbar spine, especially at L/S junction (sling)
- 2x stronger than PLL
-Superficial fibers span multiple levels, Deep fibers span single level (deep blend with AF to reinforce disk)
Role of Anterior Longitudinal Ligament
Resists:
- *Anterior shear/ translation
- *Extension
- Axial rotation
- Distraction
Slacks with flexion
Proprioception with extension
Posterior Longitudinal Ligament
Ventral surface of vertebral canal
Very thin in lumbar region (thicker in C spine)
Resistance to axial tension is 1/6 that of ALL
Superficial span multiple levels, deep attach adjacent vertebrae and interlace with outer AF
Role of Posterior Longitudinal Ligament
Resist:
- Posterior translation
- Flexion (minimally)
Slacks with extension
Proprioception with flexion
Ligamentum Flavum
- Postero-lateral surface of vertebral canal
- Connect lamina to lamina
- Highly elastic and thick
- Includes slips to anterior facet joint capsule
With aging: Stretches out – can buckle in spinal canal
Role of Ligamentum Flavum
- Resists flexion
- Slacks with extension
- May assist with return to extension
- Elasticity –> constant tension, creating compressive force on disk –> Increase disk stiffness
Interspinous ligament
- Spinous process to spinous process
- Well developed in lumbar region
Supraspinous ligament
- Runs along tips of spinous processes from C7 to L3 (some individuals to L4)
**Absent at L5-S1
In lumbar region, blends with thoracolumbar fascia and multifidus
Role of supraspinous ligament
Resists:
- Flexion
- Separation of spinous processes
- Rotation (to a lesser degree)
Slacks with extension
Dense with mechanoreceptors –> Proprioception
Intertransverse ligament
- Bilateral transverse process to transverse process
- Blend with thoracolumbar fascia, TA, EO, lats
- Thickest in lumbar region
- Alternately stretched and compressed during lateral bending
- *Absent at L4 and L5
Role of intertransverse ligament
Resists:
- Lateral bending on contralateral side
- Rotation
Slack with lateral bending to ipsilateral side
Proprioception during lateral bending and rotation
Iliolumbar ligaments
- Ventral band and dorsal band: L4/5 Transverse process –> Iliac crest
- Sacral band: L4/5 TP and sacral ala –> Iliac crest (AKA lumbosacral ligament)
Role of iliolumbar ligaments
Prevent anterior displacement of L5 on sacrum (sliding off)
Resists motion in all planes
Lumbar mobilizers
Rectus abdominus abdominal obliques psoas major (ant fibers) iliocostalis longissimus quadratus lumborum
Lumbar stabilizers
Multifidus
Transversus abdominus
Psoas major (post fibers)
Muscular attachments to thoracolumbar fascia
Muscle function: Lumbar flexors
- Attachments on ribs, sternum, pelvis
- Rectus abdominus, psoas, obliques
- Other functions: Increasing intra-abdominal pressure (decrease stress on lumbar spine)
Muscle function: Lumbar extensors
Acting bilaterally: Dorsal muscles are extensors
Acting unilaterally: Dorsal muscles are lateral rotators and lateral flexors
Multifidus
Transverse process (and adjacent facet jt/ capsule) –> Spinous process 2-3 levels superior
From sacrum
To activate: Contralateral rotation
Multifidus action
- Increases spine stiffness (stabilization)**
- Avoid painful nipping of capsule by facet joint (approximates facets)
- Secondary:
- Extension (bilateral)
- Ipsilateral side bend
- Contralateral rotation
Transverse Abdominus
Ribs, iliac crest, thoracolumbar fascia –> Linea alba
Action of TA
- Stabilizes spine
- Narrows waist
- Generates tension on thoracolumbar fascia
Psoas major (posterior)
Transverse process (T12-L5), anterolateral vertebral bodies, intervertebral disks –> Lesser trochanter
Action of psoas major (posterior)
- Stabilizes spine (axial compression)
- Can generate anterior sheer
- Assist with trunk flexion
Thoracolumbar Fascia
- Superficial and deep
- Multiple muscular attachments of superficial and deep muscles
- Compressive “corset” to stabilize spine
Spinal Cord
Ends L1-L2
Cauda Equina
Nerve roots L2-S5 continue to run through central canal
What structures are innervated?
Lumbar disk
PLL and ALL
Interspinous ligament
Facet joints
What structure is not innervated?
Main ligamentous substance of ligamentum flavum (superficial surface is innervated)