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ANATOMY OF SPINE
Dr Pankaj N SurangeMBBS, MD, FIPP
Interventional Pain and Spine specialist
A-P X-ray of a scoliotic spine in the coronal plane.
The CORONAL PLANE, also called the FRONTAL PLANE, is a vertical cut that divides the body into front and back sections. Physicians look at the coronal plane when they view an A-P (anterior-posterior) x-ray of the spine to evaluate scoliosis.
Anatomical Planes
Lateral X-ray of a kyphotic spine in the sagittal plane.
The SAGITTAL or MEDIAN PLANE is a vertical cut that divides the body into left and right sections. The sagittal view is seen by surgeons on a lateral x-ray of the spine.
Anatomical Planes
CT Scan of a thoracic vertebra in the axial plane.
The AXIAL or TRANSVERSE PLANE is a horizontal cut that divides the body into upper and lower sections. To best view the axial plane of the spine, surgeons will often obtain a CT scan with axial cuts.
Anatomical Planes
• Protection of – spinal cord and nerve roots– internal organs
Functions of the Spine
• Flexibility of motion in six degrees of freedom
Left and RightSide Bending
Flexion and Extension Left and Right Rotation
Functions of the Spine
To achieve these functions, the spine must have:
• Resistance to axial loading forces, accomplished by:
– Kyphotic and lordotic sagittal plane curves
– Increased mass of each vertebra from C1 to the sacrum
• Elasticity accomplished by:– Alternating lordotic and kyphotic
curves– Multiple MOTION SEGMENTS
Functions of the Spine
• The FUNCTIONAL UNIT of the spine• Composed of:
– Connecting ligaments
– Two adjacent vertebrae– The intervertebral disc
– Two facet joints and capsules
The Motion Segment
• Primary CurvesSagittal Plane Curves
• Secondary Curves
Cervical Lordosis 20°- 40°
Sacral Kyphosis
Lumbar Lordosis 30°- 50°
Thoracic Kyphosis 20°- 40°
Sagittal Plane Curves
• Cervical– Upper cervical: C1-C2– Lower cervical: C3-C7
• Sacrococcygeal: 9 fused vertebrae in the sacrum and coccyx.
• Thoracic: T1-T12
• Lumbar: L1- L5
Regions of the Spine
• Line of gravityAuricle of the ear
Odontoid
Body of C7
Anterior to thoracic spine
Posterior to L3
Mid femoral heads
Regions of the Spine
Basic Vertebral StructuresBasic Vertebral Structures
Cervical Thoracic Lumbar
There are two types of bone tissue:• Cortical bone: dense, outer shell of the
vertebra
Detail of Cortical Bone
Haversian System
Detail of Cancellous Bone
• Cancellous bone: inner, spongy bone
Types of Bone Tissue
Vertebral Body
Pedicle
LaminaSuperior Articular Process
SpinousProcess
Transverse Process
Vertebral Foramen
Vertebral Structures
Superior Articular Process
Inferior Articular Process
Zygapophyseal Joint
(Facet Joint)
Pars
Vertebral Structures
Vertebral Structures
• Pedicle notchesSlight Notch
Deep Notch
Intervertebral Foramen
• INTERVERTEBRAL FORAMEN through which the spinal nerve
roots leave the spinal cord
• Anterior ArchComprised of:– Vertebral body – Anterior 1/3 of the pedicles
• Posterior ArchComprised of:– Posterior 2/3 of the pedicles– Lamina– Processes
Vertebral Arches
The Atlas (C1)
Transverse Process
Transverse Foramen
Anterior Tubercle
Articular Facet for Dens
Lateral Mass
LaminaPosterior Tubercle
Superior Articular
Facet
Superior View
The Axis (C2)
Odontoid Process (Dens)
Body
Transverse Process
Inferior Articular
Facet
Superior Articular
Facet
Anterior View Posterior View
Lateral Mass
Spinous Process
Lower Cervical Vertebrae
• C3 to C7– May be referred to as
the subaxial region– Disc at every level– Vertebral structures
are similar
Lower Cervical Vertebrae C3 - C7
Transverse ProcessBody
Sulcus for Spinal Nerve
Lateral Mass
Lamina
Pedicle
Superior Articular Facet
Vertebral Foramen
Bifid Spinous Process
Transverse Foramen
Axial View
Sulcus for Spinal Nerve
UncinateProcess
Uncovertebral Joint(Joint of Luschka)
Lower Cervical Vertebrae C3 - C7
Anterior View
The vertebral bodies of the subaxial cervical spine have upward projections on the lateral margins called UNCINATE PROCESSES.
These processes articulate with the level above to form the UNCOVERTEBRAL JOINT. These are also called JOINTS OF LUSCHKA.
Vertebra Prominens (C7)
SpinousProcess
Axial View
C7 is referred to as the VERTEBRA PROMINENS because it has a longer and larger spinous process than the other cervical vertebrae.
This spinous process is not usually bifid.
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, T1-T12• Body - heart shaped when viewed
superiorly.
• Vertebral foramen - round
• Pedicles - small in diameter
• Spinous processes - long and projected downwards
• Articular processes
Superior ArticularProcess
Inferior ArticularProcess
Thoracic Vertebrae, T1-T12
• 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
• Intervertebral foramen - large, but with increased incidence of nerve root compression
Lumbar Vertebrae, L1-L5
The SacrumSacral Horns
Sacral Ala
PediclesDorsalForamina
Sacral Hiatus
CoccyxPosterior View
Inverted triangle shape
CoccyxLateral View
Sacral Promontory
Sacral Tilt30°-60°
Sacral Canal
1
2
3
4
5
Sacral Hiatus
The Sacrum
• Intervertebral disc
• End plate
• Apophyseal ring
– Cartilaginous layer– Bony layer
Intervertebral Disc
• Fibrocartilaginous joint of the motion segment
• Make up ¼ the length of the spinal column
• Present at levels C2-C3 to L5-S1
• Allows compressive, tensile, and rotational motion
• Largest avascular structures in the body
Intervertebral Disc
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 Pulposus Nucleus
Pulposus– Inner structure– Gelatinous– High water content– Resists axial forces
Occipitocervical JointOccipital Condyles
ForamenMagnum
articulate with C1 superior
facets
Atlantoaxial Joint
C1
C2
Dens
Zygapophyseal joints
JOINT between the atlas (C1) and the axis (C2); has a range of motion in the transverse plane for rotation.
The DENS of C2 acts as a pivot point for the rotation of C1.
The articulating surfaces of the two vertebrae form ZYGAPOPHYSEAL (FACET) JOINTS that allow flexion-extension, side bending, and rotational movements.
Also called ZYGAPOPHYSEAL JOINTS.
The facet joints are formed by the articular processes of adjacent vertebrae. The inferior articular process of a vertebra articulates with the superior articular process of the vertebra below.
These are synovial gliding joints
Facet joints are oriented in different planes depending on their anatomic location.
The Facet Joints
Uncovertebral JointsUncovertebral
JointThe bony elevations on the superior lateral margins of the cervical vertebrae are called UNCINATE PROCESSES.
The uncovertebral joints are not true joints
These joints articulate with the inferior, lateral aspect of the vertebra above to form the UNCOVERTEBRAL JOINTS, also known as the JOINTS OF LUSCHKA. These are fibrous joints
Uncinate Process
The T2-T9 thoracic vertebra have facets superiorly and inferiorly at the posterior aspect of the vertebral body that form the COSTOVERTEBRAL joints.
Costovertebral JointsCostovertebral
joints
Rib
Costotransverse joints
Axial View
In the thoracic spine, the RIBS articulate with the vertebrae at both the body and the transverse processes.
At all thoracic levels there is a facet where the rib articulates with the transverse process. These are called the COSTOTRANSVERSE joints.
The T1 and T10-T12 vertebral bodies have only one costal facet.
Rib
Lateral View
Costovertebral joints
Costotransverse joint
Rib
Costovertebral Joints
Sacroiliac Joint
Sacroiliac Ligaments
SacrumIlium
The superior lateral surface on either side of the sacrum articulates with the inner aspects of the pelvis. This area forms the capsular, synovial SACROILIAC JOINT.
In some cases the sacroiliac joint is a hidden source of back pain.
Upper Cervical LigamentsOccipitoatlantal Ligament Complex
Anterior occipitoatlantal ligament
Posterior occipitoatlantal ligament
Lateral occipitoatlantal ligament
Anterior View
Upper Cervical LigamentsOccipitoaxial Ligament Complex
Alar ligaments (2)Apical ligament
Posterior cutaway view
Occipitoaxial ligament
Posterior view
Lower Cervical, Thoracic, and Lumbar Ligaments
•Extending from the axis (C2) anteriorly to the sacrum.
•Is broader at the level of each vertebral body than at the level of the discs where the fibers adhere to the annulus fibrosus.
•Attaches to each vertebral body superiorly and inferiorly at the levels of the end plates.
Anterior Longitudinal Ligament (ALL)
Intertransverseligaments
Costal ligaments
Lower Cervical, Thoracic, and Lumbar Ligaments
The INTERTRANSVERSE LIGAMENTS extend from the inferior surface of the entire length of the transverse process to the superior surface of the adjacent transverse process.
The COSTAL LIGAMENTS connect the heads of the ribs to the vertebrae.
Posterior longitudinal ligament
Lower Cervical, Thoracic, and Lumbar Ligaments
POSTERIOR LONGITUDINAL LIGAMENT (PLL)
• Is weaker than the ALL.
• It runs from the axis (C2) caudally to the sacrum.
•The PLL is narrow at the levels of the vertebrae, but the fibers extend laterally at the disc levels. These fibers may help to contain herniated disc material.
•Like the ALL, the PLL is attached to the vertebra at the superior and inferior margins, and to the annular fibers of the intervertebral disc.
Interspinous ligament
Ligamentum nuchae
Lower Cervical, Thoracic, and Lumbar Ligaments
The INTERSPINOUS LIGAMENT connects each adjacent spinous process.
In the cervical spine the interspinous ligament becomes part of the LIGAMENTUM NUCHAE, that extends cranially to insert into the occiput.
The SUPRASPINOUS LIGAMENT is a very strong band connecting the tips of contiguous spinous processes. It extends from C7 to the sacrum.
Supraspinous ligament
Ligamentum nuchae
Lower Cervical, Thoracic, and Lumbar Ligaments
Above C7 these fibers are part of the LIGAMENTUM NUCHAE.
Ligamentum flavum
Lower Cervical, Thoracic, and Lumbar Ligaments
LIGAMENTUM FLAVUM
Also called the YELLOW LIGAMENT
Consists of elastic fibers oriented vertically that extend from the anterior inferior surface of the lamina above to the superior posterior surface of the lamina below.
The ligamentum flavum tends to thicken as it progresses down the spine, beginning at the axis (C2) and extending to the sacrum.
The ILIOLUMBAR LIGAMENTS extend from the transverse processes of L4 and L5 to the iliac crest.
Iliolumbar ligaments
Anterior View Posterior View
Lumbosacral Ligaments
Lumbosacral Ligaments
Anterior View
Lumbosacral ligaments
The LUMBOSACRAL LIGAMENT is a thick, fibrous band that extends from the anterior, inferior aspect of the transverse process of L5 to the lateral surface of the sacrum.
Sacroiliac LigamentsShort sacroiliac ligaments
Posterior View
Long sacroiliac ligaments
The SACROILIAC LIGAMENTS are as follows:
• short sacroiliac ligaments: composed of horizontal fibers extending from the sacrum to the posterior part of the iliac bone
• long sacroiliac ligaments: composed of fibers extending vertically from the sacrum to the posterior superior iliac spine
Posterior Spinal Muscle Groups
Iliocostalis
The superficial posterior muscles are collectively called the ERECTOR SPINAE, comprising three groups:
Longissimus
Spinalis
ErectorSpinae
Posterior Spinal Muscle Groups
semispinalis capitis
semispinalis cervicis
semispinalis thoracis
The middle, or intermediate, muscle group of the spine is called the SEMISPINALIS GROUP:
Posterior Spinal Muscle Groups
Multifidus
Intertransversarii attachments between spinous processes
Rotatores (longus and brevis)
Rotatores cervices
Rotatores thoracis
Rotatores lumborum
Levatores costae (longus and brevis)
The deep muscle layer consists of the following groups:
Arteries of the Cranial and Cervical Region
Foramen lacerum
Vertebral artery
Carotid artery
Two VERTEBRAL ARTERIES, one located on each side the cervical vertebrae. These arteries are branches of the right and left subclavian vs. that exit from aorta.
They ascend through the transverse foramen of C6 through C1,entering the skull through the foramen magnum where they join together to form the BASILAR ARTERY.
Anterior to the cervical vertebrae are the CAROTID ARTERIES, which ascend through the FORAMEN LACERUM and join with the vertebral arteries to form the CIRCLE OF WILLIS.
Arteries of the Cranial and Cervical Region
Vertebral arteries
Basilar artery
Circle of Willis
Internal carotid arteries
Arteries of the Thoracic and Lumbosacral RegionsVertebral artery Aortic arch
Ascending aorta
Descending aorta
Thoracic segmental arteries
Abdominal aorta
Bifurcation of the aorta Lumbar
segmental arteriesExternal iliac
artery (left & right) Internal
iliac artery (left & right)Femoral artery
(left & right)
Segmental Arteries At each vertebral level from T4 to the sacrum, a pair
of SEGMENTAL ARTERIES branches posteriorly from the aorta to supply blood to the vertebral body, posterior elements, spinal cord, and costal structures.
Aorta
Segmental arteries
Intercostal artery
Spinal branch
Anterior spinal artery
Posterior branch
Anastomoses
The most important venous structures in the cervical spine are the internal and external JUGULAR VEINS. The internal jugular veins follow a path similar to the carotid arteries. They should always be considered during any anterior cervical spine procedure.
Veins of the Cervical and Thoracic Region
External jugular
Anterior jugular
Internal jugular
Veins of the Thoracic and Lumbar RegionInternal jugular
Superior vena cavaAzygos
veinThoracic segmental veins
Hemiazygos vein
Lumbar segmental veins
Inferior vena cava
Common iliac veins
Batson’s PlexusThe AZYGOS SYSTEM is a large
network of veins draining blood from the intestines and other abdominal organs back to the heart. The segmental veins drain into the azygos vein located on the right side of the abdomen, or into the hemiazygos vein located on the left side.
The azygos system also communicates with a valveless venous network known as BATSON’S PLEXUS. When the vena cava is partially or totally occluded, Batson’s plexus provides an alternate route for blood return to the heart.
The vessels of Batson’s plexus may be referred to as epidural veins
Batson’s plexus
Spinal Nerve StructuresSpinal Cord• Contained in epidural space• Network of sensory and motor
nerves• Firm, cord-like structure
Foramen magnum
• Extends from foramen magnum to L1
• Terminates at the conus medularis
• The cauda equina begins below L1
• Filum terminale extends from conus medularis to the coccyx
Conus medularis
Cauda equina
Meninges
Dura mater
Subdural space
Arachnoid layer
Subarachnoid space: filled with CSF
Pia mater
Within the spinal canal, the spinal cord is surrounded by the EPIDURAL SPACE, filled with fatty tissue, veins, and arteries. The fatty tissue acts as a shock absorber.
The spinal cord is covered by MENINGES which has three layers.
Spinal Nerve Topography
31 pairs of spinal nerves• 8 cervical• 12 thoracic• 5 lumbar• 6 sacrococcygeal
Spinal NervesSpinal cord
Epidural space
Dura mater and Arachnoid layers
Subarachnoid space
Dorsal root
Ventral root
Dorsal root ganglion
Peripheral nerve
Autonomic Nervous SystemIndependent of voluntary control.
Controls glandular and cardiac function and smooth muscle such as that found in the digestive tract.
There are two components: sympathetic parasympathetic
The control centers of both systems are located outside the spinal cord in structures called GANGLIA.
Autonomic Nervous SystemThe SYMPATHETIC NERVOUS
SYSTEM consists of a series of ganglia extending from the skull to the coccyx, lying on each side of the vertebral bodies. These aligned ganglia look like a chain at each side of the spine and are often referred to as the sympathetic nerve chain.
Injury to the sympathetic nerve chain in the lumbar spine may result in genitourinary problems for the patient.
Each sympathetic ganglion has fibers that join to the adjacent spinal nerve.
The PARASYMPATHETIC NERVOUS SYSTEM has ganglia located close to the organs they control.
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