Spinal Anatomy

Copyright © 2001 Medtronic Sofamor Danek, Inc. All rights

reserved.

Anatomical Planes

• Anatomical position

• Axial (Horizontal or

Transverse) - divides the body into upper and lower

segments

• Coronal (Frontal) - divides

the body into front and back

sections

• Sagittal - divides the body into left and right sections

• Cranial - the head or

towards the head

• Caudal - the tail or towards

the tail

• Anterior - the front section

or towards the front

• Posterior - the back section

or towards the back

• Ventral - the front or

anterior surface

• Dorsal - the back or

posterior surface

Basic Terminology

Cranial

Caudal

Anterior

PosteriorD

ors

al V

entr

al

Basic Vertebral Structures

Cervical Thoracic Lumbar

• Anterior Arch

– Vertebral body

– Anterior 1/3 pedicles

Vertebral Arches

• Posterior Arch

– Posterior 2/3 pedicles and

posterior elements

– Arches form the vertebral

foramen

Vertebral Structures

Body

Pedicle

LaminaSuperior Articular Process

SpinousProcess

TransverseProcess

Vertebral Foramen

Vertebral Structures

• Articular processes Superior Articular Process• Pars interarticularis

Inferior Articular Process

Zygapophyseal Joint

(Facet Joint)

Pars

• Intervertebral Disc

Vertebral Structures

• End Plate

• Apophyseal Ring

– Cartilaginous

– Bony

• The FUNCTIONAL UNIT of the

spine

• Comprised of:

– Two adjacent vertebrae

– Intervertebral disc

– Connecting ligaments

– Two facet joints and capsules

The Motion Segment

Vertebral Structures

• Pedicle notches

Slight Notch

Deep Notch

Intervertebral Foramen

• Intervertebral foramen

• Nerve roots exit

• Cervical– Upper cervical: C1-C2

– Lower cervical: C3-C7

Regions of the Spine

• Sacrococcygeal

• Thoracic

• Lumbar

Thoracic Vertebrae

• Body - progressive increase in

mass from T1 to T12

• Pedicles - small diameter

• Laminae - vertical, with “roof

tile” arrangement

• Spinous processes - long,

overlapping, projected downward

• Intervertebral foramen - larger,

less incidence of nerve

compression

Thoracic Vertebrae

• Body - heart shaped (axial

view)

• Vertebral foramen - round

• Pedicles - small in diameter

• Spinous processes - long and

projected downwards

Lumbar Vertebrae

• Body - L1 to L5 progressive increase in mass

• Pedicles - longer and wider than thoracic; oval shaped

• Spinous processes - horizontal, square shaped

• Transverse processes - smaller than in thoracic region

• Spinal foramen- large to allow for cauda equina and nerve roots

• Intervertebral foramen - large, but with increased incidence of nerve root compression

CoccyxLateral View

Sacral

Promontory

Sacral Tilt30°-60°

Sacral Canal

The Sacrum

1

2

3

4

5

Sacral Hiatus

Sacral Horn

Intervertebral Disc

• Annulus Fibrosus

– Outer portion of the disc

Lamellae

• Great tensile strength

– Made up of lamellae

Annulus

Fibrosus

– Layers of collagen fibers

• Arranged obliquely 30°

• Reversed contiguous layers

Intervertebral Disc

• Nucleus PulposusNucleus Pulposus

– Inner structure

– Gelatinous

– High water content

– Resists axial forces

Ligaments

Ligamentum flavum

Posterior longitudinal ligament

Anterior longitudinal ligament

Spinal Nerve Structures

• Spinal Cord

– Contained in epidural space

– Network of sensory and motor

nerves

– Firm, cord-like structure

– Extends from foramen

magnum to L1

– Terminates at conus medularis

– Cauda equina below L1

– Filum terminale

Spinal Nerves

• Ventral roots (anterior)– Motor

– Cell body in spinal cord

• Dorsal roots (posterior)– Sensory

– Cell body in dorsal root ganglia

• Peripheral nerve

• Aorta– Thoracic

– Ascending, aortic arch, descending

– Abdominal

• Common iliac (bifurcation at L4)

• Femoral

• External iliac

• Middle sacral

• Internal iliac

• Iliolumbar

Thoracic and Lumbosacral Arteries

Segmental Arteries

• T4 to sacrum at each level

from aorta

• Intercostal branch

• Posterior branch

• Spinal branch

– Anterior spinal artery

– Perforating arteries

• Superior vena cava

• Segmental veins

• Inferior vena cava

• Common iliac veins

– Thin-walled, easily

injured

• Azygous vein

• Hemiazygous vein

Thoracic and Lumbosacral Veins

X-ray Views• Standard/Plain Films

– Anteroposterior (AP) or Posteroanterior (PA)

X-ray Views• Standard/Plain Films

– Lateral

X-ray Views

• Special Views

– Flexion: forward bend

– Extension: backward bend

– Purpose: evaluate motion

segment instability

Special Radiographic Studies

Fluoroscopy

• Permits real-time imaging

• Often used during surgical procedure (C-arm)

• Used for placement of needles, guidewires, and other

devices

• Appearance of radiodensity is opposite of processed

x-ray film, example: bone appears dark

Myelography

• Purpose:

– Show compression or displacement of neural elements

• Method:

– Radiopaque material injected into the thecal sac

– Standard x-rays and/or fluoroscopy

• Reading:

– Neural structures are dark

– Contrast material white

Special Radiographic Studies

Special Radiographic Studies

Discography

• Purpose:

– Evaluate patency of disc

– Establish whether disc is causing

back/radicular pain

• Method:

– Place needle into disc under fluoro

– Inject dye into the disc

• Reading:

– Dye leaks out of nucleus = incompetent disc

– Injection reproduces pain = disc as source of

pain (Provocative discogram)

Special Radiographic Studies

Computed Tomography (CT/CAT)

• Purpose:

– Detect bony tissue pathologies

• Method:

– Multiple slices of axial x-ray images (1-4mm)

– Computer constructs into permanent image

• High radiation exposure

Special Radiographic Studies

Magnetic Resonance Imaging

(MRI)

• Purpose:

– Detect soft tissue pathologies

• Method:

– Uses magnetic and radio wave energy

– Shows a two-dimensional slice

• Coronal, sagittal or axial view

• No radiation

Special Radiographic Studies

Bone Scan

• Purpose:

– Detect inflammation, infection, tumor

• Method:

– Inject radioisotope into the bloodstream

– Isotope absorbed by bone tissue

– Gamma scan detects radiation

• Reading:

– Dark areas = increased activity (hot spot)

Degenerative Change

The Intervertebral Disc (IVD)

• By age 50, 95% of people show lumbar disc degeneration

• Not all have symptoms

• Significant changes to IVD are:

– Water and proteoglycan content decreases

– Collagen fibers of AF become distorted

– Tears may occur in the lamellae

• Results in:– Disc loses height and volume

– Loses resistance to loading forces

• No longer acts as a shock absorber

Degenerative Change

The Vertebral Body (VB)

• Key Roles

– Carry 80% of the axial loads through VB and disc

– Endplates enable nutrition to diffuse to disc

Degenerative Change

The Vertebral Body (VB)

• Degenerative Changes

– Sclerosis: Increased bone formation adjacent to endplates

• Reduces nutrition diffusing to disc

• Stiffens endplate, and reduces ability to absorb loads

– Osteophytes: Formation of small bony spurs

• Can project into neuro structures

Degenerative Disc Disease• Changes include:

– Disc loses height and volume

– Compressive loads transfer away from nucleus to margins

– Sclerosis of endplate reduces disc nutrition

– Facet joints wear away cartilage, begin to override

– Motion segment becomes hypermobile

– Osteophytes develop to attempt to stabilize motion segment

– Osteophytes may encroach on neuro structures

Spinal Stenosis

• Narrowing of the spinal canal and/or lateral foramen through which the nerves travel

• Three types:

– Central stenosis: in central spinal canal where cord or cauda equina are located

– Lateral recess stenosis: in the tract where nerve roots exit canal

– Acquired: in lateral foramen where nerve roots exit to body

• Most frequent in lower cervical and lower lumbar spine

Lumbar Spinal Stenosis

• Back pain almost always present

• Buttock, leg pain common

• Neurogenic claudication increases with walking

/standing

– Usually causes back and leg pain

– Relief with flexing forward

Spinal Stenosis

Treatment• Conservative options include:

– Stretching, swimming, etc

– Epidural steroid injections

• Severe stenosis / intractable pain candidates for surgery

– Central stenosis: laminectomy with medial facetectomy may be enough

– Stenosis in lateral recess or lateral foramen may require laminectomy, facetectomy and foraminotomy

Axial CT

myelogram

L2-3

Axial CT

myelogram

L3-4

Herniated Disc

• Often called “ruptured disc”

• Very common pathology

• L3-4, L4-5, L5-S1 common

locations

• Thought to be a culmination of

acute traumatic events to the disc

Herniated Disc4 degrees:• Nuclear herniation: nucleus

ruptures. No disruption of outer annular fibers

• Disc protrusion: ruptured nucleus causes outer fibers to bulge

• Nuclear extrusion: Complete split in annulus. Material leaks but remains attached to nucleus

• Sequestered nucleus: Leaked substance no longer attached to nucleus

Lateral MRI,

HNP L4-5

Axial MRI,

HNP L4-5

Initial Non-surgical

Treatments

Non-surgical options* may include:

• Physical therapy

• Pain medication

• Anti-inflammatory medications

• Bracing

• Behavior modification

• Epidural Steroid Injections

*for patients who don’t have weakness or incontinence

Treatment

• Not all patients suffer pain

• As outer disc distorts, may protrude into spinal canal

• May lead to sciatica (pain down back of leg)

• Often start with conservative, non-operative care

– Spontaneous resolution of sciatica often occurs

• Patients with cauda equina syndrome require surgical

attention

• Common surgical procedures include:

– Laminectomy, discectomy, microdiscectomy, endoscopic

discectomy, ablation procedure

Minimally Invasive Spine

ProceduresMinimally invasive techniques can be used to treat conditions of the cervical, thoracic, and lumbar spine:

– Herniated Discs

– Degenerative Disc Disease

– Spondylolisthesis

– Stenosis

– Degenerative Deformity

– Tumor

Why Minimally Invasive?

or

Old Approach New Technology

Accessing the Spine

• A series of soft-tissue dilators create a small tunnel through the muscles of the back.

Accessing the Spine

• A tubular retractor is inserted over these dilators to the level of the spinal column and serves as the working portal.

• The tubular retractor or “portal” is chosen specifically for the procedure and patient anatomy.

Spondylolisthesis

• Slip of one vertebra in relation to

an adjacent vertebra

• Slipped vertebra carries entire load of vertebral column above

• Spondylolisthesis is a forward slip Retrolisthesis is a backward slipLateral listhesis is a sideways slip

• Most often at L4-5, L5-S1

Anatomy

• Usually result of defect in pars interarticularis

• Micro fractures in pars from repeated, excessive

loads (football linemen, gymnasts have high

incidence)

• Disc degeneration associated with most forms of

spondylolisthesis

Spondylolisthesis

ClassificationTwo main classification systems:

• Wiltse

– Classed by etiology types

• Type I = dysplastic or congenital

• Type II = isthmic (3 subtypes)

– Stress fx, elongated healed fx, acute fx

• Type III = degenerative

• Type IV = traumatic

• Type V = pathologic

• Type VI = iatrogenic

Spondylolisthesis

Grading• Several methods. Myerding is common:

– Catergorize by % one vertebral body translates anterior to level below

Spondylolisthesis

Radiographic Evaluation• Standing lateral x-ray best initial evaluation

• AP may disclose Napoleon’s Hat (high degree slip)

• Oblique view may reveal Scotty Dog

– “broken neck” or “collar” on dog indicates spondylolytic lesion

Spondylolisthesis

Treatment

• Non-operative modalities

– Cessation of precipitating activity, bed rest, bracing

– Often successful with children

• Surgical intervention for patients with neurologic involvement, intractable pain and unresponsive to non-op methods

• Surgical indications and techniques a widely debated subject

Spondylolisthesis

Lateral preop x-ray,

low back isthmic

spondylolisthesis L4-5

Sagittal preop MRI

low back isthmic

spondylolisthesis L4-5

Axial preop MRI low

back isthmic

spondylolisthesis L4-5

Lateral postop x-ray,

posterior spinal fusion

with instrumentation

AP postop x-ray,

posterior spinal fusion

with instrumentation

Lateral preop x-ray,

low back isthmic

spondylolisthesis L4-5

Lateral postop x-ray,

posterior spinal fusion

with instrumentation

AP postop x-ray, L4/5

and L5/S1 ALIF with

posterior percutaneous

spinal fusion with

instrumentation

Intrathecal Drug Delivery

– At least 3 classes of G protein opioid receptors distributed widely in the CNS: μ-mu, δ-delta and κ-kappa

• high densities of these found in peri-aqueductal gray, medullary nucleus raphe magnus, spinal cord, caudate nucleus, septal nucleus, hypothalamus, and hippocampus.

• Trial injection (dose 100 times < IV dose) prior to insertion

• Advantages: less sedation/confusion,

constipation, and N/V; less effective

after 1 year so not indicated for

chronic benign pain

• Often used in past for diffuse, axial

cancer-related back pain in

terminally ill patients

Dorsal Column Stimulation

Indications: failed back surgery syndrome, refractory angina pectoris, painful limb ischemia (peripheral vascular syndromes) and CRPS; about 75% of patients receive 50% pain reduction

Better for focal than generalized pain and better for leg pain than axial back pain