Chapter 10: Lumbar Spine, Sacrum, Coccyx

Combination osteolytic and osteoblastic metastases

"moth eaten" appearance of bone resulting from the mix of destructive and blastic lesions.

Superior articular processes of sacrum

2. Form zygapophyseal joints with the inferior articular processes of the 5th lumbar vertebrae.

Lumbar vertebrae

5. Largest individual vertebrae. Strongest in the vertebral column because the load of body weight increases toward the inferior end of the column. Cartilaginous disks between are common sites for injury and pathologic processes.

Spina bifida

A congenital condition in which the posterior aspects of the vertebrae fail to develop, thus exposing part of the spinal cord.

Inferior vertebral notch

A half-moon shaped area along the lower surface of each pedicle.

Superior vertebral notch

A half-moon shaped area along the upper surface of each pedicle.

Intervertebral foramina

A single opening formed when vertebrae are stacked, and the superior and inferior vertebral notches line up. Two between every two vertebra, one one each side, through which important spinal nerves and blood vessels pass. Demonstrated best on lateral image.

Gonadal shielding

Always used on males

Ankylosing spondylitis

An inflammatory condition that usually begins in the SI joints and progresses up the vertebral column. Common in males in their 30's.

Inferior articular processes

Articular processes on each vertebra that project downward from the area of the junction of the pedicles and laminae.

Superior articular processes

Articular processes on each vertebra that project upward from the area of the junction of the pedicles and laminae.

Posterior oblique of lumbar spine

Best demonstrates the downside zygapophyseal joints.

Intervertebral joint type

Between the bodies of any two vertebrae. Contain intervertebral disks that are made up of fibrocartilage and are only slightly movable. These joints, which are tightly bound by cartilage, are classified as cartilaginous joints. They are amphiarthrodial (slightly movable) of the symphysis sub-class.

Zygapophyseal joint type

Between the superior and inferior articular processes. Are classified as synovial. Diarthrodial (freely movable) with a plane (gliding) type of movement.

Base of coccyx

Broader, superior portion of the coccyx.

apex of coccyx

Distal pointed tip of the coccyx.

Sacroiliac joint

Each opens obliquely posteriorly at an angle of 30 degrees. Joints between sacrum and ilium.

Laminae

Form a bridge between the transverse processes, lateral masses, and spinous process.

Median sacral crest

Formed by fused spinous processes of the sacral vertebrae.

Pelvic sacral foramina

Four sets. Transmit nerves and blood vessels.

Lateral perspective of the sacrum

Illustrates the dominant convex curve (posterior perspective) of the sacrum and the forward projection of the coccyx.

Spondylolisthesis

Involves forward movement of one vertebra in relation to another.

Alae of Sacrum

Large masses of bone lateral to the first sacral segment.

Scoliosis

Lateral curvature of the vertebral column that usually occurs with some rotation of the vertebra. It involves the throacic and lumbar regions.

Compression fractures

May be due to trauma, osteoporosis, or metastatic disease. The superior and inferior surfaces of the vertebral body are driven together, producing a wedge-shaped vertebra.

Auricular surface

Named because of its resemblance in shape to the auricle of the ear. Here the sacrum articulates with the ilium of the pelvis.

Pars interarticularis

Portion of each lamina between the superior and inferior articular processes. Demonstrated on oblique lumbar image.

Sacral canal

Posterior to the body of the first sacral segment. Is a continuation of the vertebral canal and contains certain sacral nerves.

Spinous process

Posteriorly projecting off lumbar vertebra, bulky and blunt. The palpable lower tip lies at the level of the intervertebral disk space inferior to each vertebral body.

Metastases

Primary malignant neoplasms that spread to distant sites via blood and lymphatics.

PA vs AP

Prone places lumbar spine with its natural lumbar curvature so that the intervertebral disk spaces are nearer parallel to the divergetn x-ray beam. Provides better visualization of the margins of the intervertebral disk spaces, and lowers female ovarian dose of 25% to 30%. PA increases OID which results in magnification unsharpness.

Myelography

Requires injection of contrast medium into the suparachnoid space via a lumbar or cervical puncture to visualize the soft tissue structures of the spinal canal.

Chance fractures

Result from a hyperflexion force that causes fracture through the vertebral body and posterior elements. Patients wearing a lap-type seat belt are at risk because these belts act as a fulcrum during sudden deceleration

"Scottie dog"

Seen in a good 45 degree oblique lumbar spine image. The neck is one pars interarticularis, the ear is one superior articular process, the eye is formed by one pedicle, one transverse process forms the nose, the front legs are formed by one inferior articular process.

Sacrum

Shovel shaped, with the apex pointed inferiorly and anteriorly. The bodies of the original five segments are fused into a single bone in the adult.

Intervertebral foramen

Situated 90° relative to the midsagittal plane. Are spaces or openings between pedicles.

Sacral horns (cornua)

Small tubercles that represent the inferior articular processes projecting inferiorly from each side of the 5th sacral segment. Project inferiorly and posteriorly to articulate with the corresponding horns (cornua) of the coccyx.

Curvature of the coccyx

The coccyx curves anteriorly so that the apex points toward the symphysis pubis. More pronounced in males and less pronounced, with less curvature, in females.

Spondylolysis

The dissolution of a vertebra, such as from aplasia of the vertebral arch and separation of the pars interarticularis of the vertebra.

Coccyx

The most distal portion of the vertebral column. "tailbone." Three to five segments (ave. of 4) have fused in the adult to form.

Promontory of the sacrum

The posterior wall of the inlet of the true pelvis formed by the anterior ridge of the body of the 1st sacral segment. Best demonstrated from lateral perspective.

Transverse processes of coccyx

Two lateral projections on the most superior, largest, and broadest of the four sections of the coccyx.

Herniated nucleus pulposus (HNP)

aka herniated lumbar disc (slipped disk). Usually due to trauma or improper lifting. The soft inner part of the intervertebral disk protrudes through the fibrous outer layer, pressing on the spinal cord or nerves. Occurs most frequently at L4 to L5 levels, causing sciatica.

Anterior oblique of lumbar spine

best demonstrates upside zygapophyseal joints.

Osteolytic metastases

destructive lesions with irregular margins

Range of motion of combined effects of all vertebrae

flexion, extension, lateral flexion (bending), and rotation.

Zygapophyseal joints

form an angle open from 30 to 50 degrees to the midsagittal plane. Proximal lumbar vertebrae are nearer 50 degrees. Distal nearer 30 degrees. Ave. rotation 45 degrees.

Osteoblastic metastases

proliferative bony lesions of increased density