L-Spine, coccyx, and sacrum anatomy/positioning 1/31/26

What forms the central axis of the skeleton?

Vertebral column

What are the main functions of the vertebral column?

Protects the spinal cord, supports the trunk and skull, and provides muscle attachments

What type of bones are vertebrae?

Small irregular bones

How many vertebrae are present in early life?

33 vertebrae

How many true (movable) vertebrae are there?

24 vetebrae

Which vertebrae are considered false (fixed)?

Sacral and coccygeal vertebrae

What happens to the sacral vertebrae?

They fuse to form the sacrum

What happens to the coccygeal vertebrae?

They fuse to form the coccyx

What are the five regions of the vertebral column?

Cervical, thoracic, lumbar, sacral, and coccygeal

Which vertebrae are located in the neck region?

Cervical vertebrae

Which vertebrae are located in the thoracic region?

Thoracic vertebrae

Which vertebrae are located in the lower back?

Lumbar vetebrae

Which vertebrae fuse to form the sacrum?

Sacral vertebrae

Which vertebrae fuse to form the coccyx?

Coccygeal vertebrae

What type of curvature is the cervical spine?

Lordotic

What type of curvature is the thoracic spine?

Kyphotic

What type of curvature is the lumbar spine?

Lordotic

What type of curvature is the pelvic spine?

Kyphotic

What is kyphosis?

Increased kyphotic curvature of the thoracic spine

What are the two main parts of a vertebra?

Vertebral body and vertebral arch

Which part of a vertebra is anterior?

Vertebral body

Which part of a vertebra is posterior?

Vertebral arch

What space is formed by the vertebral body and arch?

Vertebral foramen

What is formed by the articulation of vertebral foramina?

Vertebral canal

What structures form the vertebral arch?

Two pedicles and two laminae

What are pedicles?

Projections extending posteriorly from the vertebral body

What do vertebral notches form?

Intervertebral foramina

What are laminae?

Thin plates projecting posteriorly and medially from pedicles

What projects posteriorly and inferiorly from the laminae?

Spinous process

What projects laterally from the junction of pedicles and laminae?

Transverse processes

How many articular processes does a typical vertebra have?

Four

What are the two types of articular processes?

Two superior and two inferior

What do articular processes form?

Zygapophyseal (facet) joints

What are zygapophyseal joints also called?

Interarticular facet joints

What is spina bifida?

Failure of the laminae to fuse

How many lumbar vertebrae are there?

five

Where is the lumbar spine located?

Posterior abdominal region

How do lumbar transverse processes compare to thoracic?

Smaller than thoracic transverse processes

What is the pars interarticularis?

Portion of the lamina between the articular processes

What radiographic sign represents the pars interarticularis?

Scottie dog sign

What joints are demonstrated on posterior oblique lumbar spine images?

Downside zygapophyseal joints

What joints are demonstrated on anterior oblique lumbar spine images?

Upside zygapophyseal joints

What does an LPO lumbar spine demonstrate?

Left (downside) zygapophyseal joints

What is the sacrum formed from?

Fusion of five sacral vertebrae

Where is the sacrum located?

Between the iliac bones

What joints are formed between the sacrum and ilium?

Sacroiliac (SI) joints

What is the sacral promontory?

Anterior projecting margin of S1

What is the sacral canal?

Continuation of the vertebral canal

How does the coccyx curve?

Inferiorly and anteriorly from the sacrum

What separates vertebral bodies?

Intervertebral disks

What is the function of intervertebral disks?

Act as cushions

What is the annulus fibrosus?

Outer fibrocartilaginous portion of the disk

What is the nucleus pulposus?

Central soft portion of the disk

What type of joints are intervertebral joints?

Cartilaginous

What type of joints are zygapophyseal joints?

Synovial (diarthrodial) gliding joints

At what angle are L1–L4 facet joints oriented?

45 degrees from the coronal plane

At what angle are L5–S1 facet joints oriented?

60 degrees from the coronal plane

What is another term for HNP?

Slipped disk

What commonly causes HNP?

Improper body mechanics or injury

Where do most HNPs occur?

L4–L5 and L5–S1

Why is HNP painful?

Compression of the spinal cord or nerve roots

What is spondylolysis?

Congenital defect or fracture of the pars interarticularis

Which projection best demonstrates spondylolysis?

Oblique lumbar spine

Why are athletes with unilateral spondylolysis at risk?

Increased stress fracture risk of the opposite pars

What is spondylolisthesis?

Forward displacement of one vertebral body over another

Which projection best demonstrates spondylolisthesis?

Lateral lumbar spine

Where does spondylolisthesis most commonly occur?

L5–S1 and L4–L5

What is osteoarthritis (DJD) of the spine?

Degeneration from wear and tear

What are common radiographic signs of DJD?

Lipping and bone spurring

Name the curve for each region: Cervical

Lordotic

Name the curve for each region: Thoracic

Kyphotic

Name the curve for each region: Lumbar

Lordotic

Name the curve for each region: Pelvic

Kyphotic

What view do you see the interverterbal foramina?

Lateral L-Spine

Uniqe features of L-Spine

Shorter process and pars interarticularis

What are the five major parts of the vertebral column

Cervical, Thoracic, Lumbar, Sacrum, Coccyx

Which vertebrae make up the cervical region

C1 to C7

Which vertebrae make up the thoracic region

T1 to T12

Which vertebrae make up the lumbar region

L1 to L5

What is the sacrum and where is it located

Triangular bone at base of spine, formed by fused sacral vertebrae

What is the coccyx and how many vertebrae does it contain

Tailbone, 3–5 rudimentary vertebrae

What is the normal curvature of the cervical spine called

Lordotic

What is the normal curvature of the thoracic spine called

Kyphotic

What is the normal curvature of the lumbar spine called

Lordotic

What is the normal curvature of the sacral/pelvic region called

Kyphotic

What is kyphosis in terms of spinal curvature

Excessive outward curvature of the thoracic spine

What is lordosis in terms of spinal curvature

Excessive inward curvature of the lumbar spine

What is scoliosis and how does it affect the spine

Abnormal “S” shaped lateral curvature

Which part of a typical vertebra bears most of the weight

Vertebral body

Which part of a vertebra forms the posterior portion surrounding the spinal canal

Vertebral arch

What are pedicles in a vertebra and where are they located

Short bony projections connecting body to laminae

What are the superior and inferior vertebral notches and what do they form

Indentations on pedicles that form intervertebral foramina

Which part of a vertebra connects the transverse processes to the spinous process

Laminae

What are transverse processes and where do they extend from

Lateral projections from vertebral arch

What is the spinous process and where is it located

Posterior projection from vertebral arch

What are the superior and inferior articular processes and what do they articulate with

Projections that articulate with adjacent vertebrae

What is the pars interarticularis in the lumbar vertebrae

Part of lamina between superior and inferior articular processes

How does the lumbar spinous process differ from cervical or thoracic spinous processes

Short, thick, and blunt, pointing posteriorly

How many sacral segments fuse, and between what ages does fusion occur

5 segments, fuse between ages 20–30

What is the sacral canal and what does it transmit

Continuation of vertebral canal, transmits sacral nerves