Lumbar Anatomy

Question 1

Features of a Lumbar Vertebrae

Answer 1

• LARGE KIDNEY-SHAPED BODY
• SHORT, FLAT, RECTANGULAR SPINOUS PROCESS
• ARCH IS VERY THICK
• LONG TRANSVERSE PROCESSES
• SMALL TRIANGULAR VERTEBRAL FORAMEN
• ARTICULAR PROCESSES FACE M/L

Question 2

Bony elements- 3 zones in the vertical sagittal plane

Answer 2

1. Vertebral Body
2. Pedicles, neural foramen
3. Posterior Arch

Question 3

Vertebral Body

Answer 3

• Function:
  
  • Weight bearing
    
    • Cortical bone
    • Cancellous (trabecular) bone
  • Up to 50% of compressive load to the body is borne by the trabecular bone, 50%by the cortical shell
    
    • Blood supply helps trabecular bone and shell manage compressive loads
  • Endplates Molecules for nutrition of the disc are extruded through the end-plates with compressive loading
  • Blood within the vertebral body increases the load bearing capacity

Question 4

Posterior Elements/Arch

Answer 4

• Connected to the body by the Pedicles
  
  • Laminae
  • Transverse processes
  • Articular processes
  • Body, pedicles, and posterior arch form the vertebral canal
  • Intervertebral foramen between pedicles

Question 5

Function of the posterior arch

Answer 5

• Attachment sites for ligaments and muscles
• Osseous ring to protect neural tissue

Question 6

Lumbar Spine Joints

Answer 6

• 3 joint complex: 1 anterior (interbody) and 2 posterior (facet joints)
• Facet joints = Zygapophyseal joints
• Facet joints are part of the posterior arch
• Only facet joints are synovial
• Facet Joints
  
  • 52 including upper cervical spine (not including ribs)
  • 10 in the lumbar region
  • Plane synovial joints
  • Synovial tags, menisci

Question 7

Lumbar “FACET” Joints

Answer 7

• Synovial joints
• 2 inferior and 2 superior
• Superior joint surfaces face posterior (medial)
• Inferior surfaces face anterior (lateral)
• Innervated from a minimum of 3 nerve root levels (thus pain referral is varied, and not diagnostic)
• Different shapes have been noted

Question 8

Weight bearing in the lumbar region

Answer 8

• While the facets take on load…
• The inter-body joint is the principle weight-bearing component of the lumbar spine unless extreme lordosis or other anomaly

Question 9

Facet Joint Movement

Answer 9

1. During erect sitting the facet joints have been found to carry no vertical load (no lordosis)
2. End range extension, the tips of the inferior process of the superior vertebra impact on the lamina of the inferior vertebra - loads are transferred to the lamina
3. Prolonged standing with a lordotic spine, the facet joints become impacted
4. Load sharing with lordosis:

• L1 - L2/3 = 11%
• L3 - L5/S1 = 19%

Question 10

Facet Joint Loading

Answer 10

• Loading depends upon the tilt of the vertebra
• Narrowing of the intervertebral disc space can result in 70% of the axial load being borne by the facet joints
• Leads to degenerative changes in the facet joint
• Highest loading in the extended position
• Axial loading of the lordotic spine = accentuated lordosis, strain on the anterior ligaments which now share the load bearing

Question 11

Arthritis of the Vertebrae

Answer 11

• Osteoarthritis can cause bony growths (osteophytes) to form on the vertebrae. These can limit motion and cause pressure on the spinal nerves as they travel through the intervertebral foramina.

Question 12

Lumbar Facet Capsule

Answer 12

• Facet capsule
  
  • Contains a meniscoid / meniscus and is highly Innervated

Question 13

Lumbar Facet Joint Pain Maps- Posterior

Answer 13

Question 14

Lumbar Facet Joint Pain Maps- Anterior

Answer 14

Question 15

Issue at hand with Lumbar Spine

Answer 15

• Any innervated structure in the lumbar region can be and is a source for pain (ligament, bone, tendon, joint capsule, insertion point, disc, etc.)
• There are no diagnostic tests that have great sensitivity or specificity for a structure as the source of pain
• Diagnostic injections are most likely the best tool to date, but by no means are they perfect
• Recognize that the facet joint can be the source of nociception that leads to perception of pain in the LE, even past the knee

Question 16

Lumbosacral Junction

Answer 16

• L5-S1
• Sacrum articulates with the innominate to form the Sacroiliac Joint (SIJ)

1. Sagittal plane angle is 50 degrees between sacrum and horizontal
2. Angle between sacrum and L5 is 16 degrees (L5-S1 disc is higher anteriorly)
3. Lumbar lordosis is 70 degrees

• Body weight creates an anterior shear on the lower lumbar vertebra.
• Anterior shear force is countered by the facet joints, the ligaments and the disc.

Question 17

Motions of the Lumbar Vertebrae

Answer 17

Question 18

The Pelvic Girdle and the Sacroiliac joint (SIJ)

Answer 18

• 2 innominates (fused ilium, ischeum, and pubic bones)
  
  • Sacrum
• Functional unit includes:
  
  • SIJ
  • Pubic symphysis
  • L4 and L5
  • The hip joints

Question 19

SIJ

Answer 19

• Innominate joint surface is fibrocartilage
• Sacral surface is hyaline cartilage
• Joint surfaces have many crevices, are not smooth
• Minimal motion (4 degrees)
• Anterior joint is reported as innervated by dorsal rami of L2 through S2
• Posterior joint is reported as innervated by L4 through S3, with major contribution from S1 and S2

Question 20

SIJ and Pelvic Girdle Pain Patterns

Answer 20

Question 21

Curvatures of the Vertebral Column

Answer 21

• LUMBAR CURVATURE IS CONVEX ANTERIORLY
• ABNORMAL CURVATURE IS LORDOSIS
• HERNIATION OF INTERVERTEBRAL DISC IS COMMON
• THE SACRUM IS CONCAVE ANTERIORLY. IN ANATOMICAL POSITION, THE ANTERIOR SURFACE IS ALMOST HORIZONTAL.
• THE SACRUM IS RARELY FRACTURED OR DISLOCATED, BUT ARTHRITIS OF THE SACROILIAC JOINTS IS COMMON