View
1
Download
0
Category
Preview:
Citation preview
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
Recommended