Ch. 10 Lumbar, Sacrum, & Coccyx

Center point for posterior oblique sacroiliac joints:

1" medial to upside ASIS.

What is the degree of patient/part obliquity for posterior oblique positions for sacroiliac joints?

25-30 degrees posterior oblique, with side of interest elevated.

Center point for lateral coccyx:

3-4" posterior & 2" distal to ASIS.

Center point for lateral sacrum & coccyx:

3-4" posterior to ASIS.

Center point for AP axial L5-S1 projection:

30 degrees cephalad for males, 35 degrees cephalad for females, at the level of the ASIS centered to the midline of the body.

Center point for AP axial sacroiliac joints:

30-35 degrees cephalad (30 degrees male & 35 degrees female), 2" below level of ASIS.

Center point for lateral L5-S1 (spot) position:

5-8 degrees caudad, 1.5" inferior to iliac crest & 2" posterior to ASIS.

Spina Bifida:

A congenital condition in which the posterior aspects of the vertebrae fail to develop, exposing part of the spinal cord. Occurs most often at L5.

Scoliosis:

A lateral curvature of the vertebral column that usually occurs with some rotation of the vertebra. It involves the thoracic & lumbar regions.

What should be done to reduce scatter radiation from reaching the image receptor during lateral projections?

A lead mat.

Herniated nucleus pulposus (HNP)

AKA as herniated disk or slipped disk. It's usually due to trauma or improper lifting. The nucleus pulposus (disk) protrudes through the fibrous outer layer, pressing against the spinal cord or nerves. Most frequently in L4-L5, causing sciatica (irritation of nerve traveling down the posterior leg).

What is the topographic landmark of S1-S2?

ASIS.

Center point for AP or PA Right & Left Bending Scoliosis:

Align midsagittal plane to IR; Midpoint to IR; IR includes a minimum of 1-2" below the iliac crest.

Center point for PA or AP Scoliosis Ferguson Method:

Align midsagittal plane to IR; Midpoint to IR; IR includes a minimum of 1-2" below the iliac crest.

Ankylosing Spondylitis

An inflammatory condition that usually begins in the sacroiliac joints & progresses up the spinal column. The spine becomes rigid and joints fuse. Common in males in their 30's.

What are the anatomical structures of the sacrum?

Anterior perspective: the sacrum is concave, the original five segments are fused into a single bone, four sets of pelvic sacral foramina, the alae, two superior articular processes; Lateral perspective: the sacral canal, median sacral crest, auricle surface which articulates with the ilium and forms the sacroiliac joint, sacral horns, & coccyx; Posterior sacrum: auricular surface, articulating facets of the superior articular surface, 8 posterior sacral foramina, & sacral horns.

Center point for AP or PA Lumbar & Lateral lumbar spine:

At the level of the iliac crest.

Best modality for metastases

Bone scan.

Center point for AP Axial coccyx:

CR angled 10 degrees caudad, 2" superior to pubic symphysis.

Center point for AP axial sacrum:

CR angled 15 degrees cephalad, 2" superior to pubic symphysis.

Center point for Lateral Hyperextension & hyperflexion (spinal fusion):

CR to site of fusion if known, or center of IR.

Best modality for Spondylosis:

CT

Best modality for spondylolisthesis:

CT

What is the joint classification of the intervertebral joints of the lumbar?

Cartilaginous (symphysis).

Best modality used for compression & chance fractures:

Computed Tomography

For an RPO or LPO lumbar spine, will demonstrate upside or downside z-joints?

Downside

Why should the knees and hips be flexed for AP projections of the lumbar?

Flexing the knees reduces the lumbar curvature (lordosis), bringing the back closer to the radiographic exam table and lumbar vertebral column more parallel to the IR. Flexing the knees is also more comfortable for the patient.

For an oblique lumbar spine projection, where is the pedicle (eye) of the Scottie dog located?

For a correct 45 degree patient rotation, the pedicle or eye of the Scottie dog will be located near the center of the vertebral body. The pedicle (eye) demonstrated posteriorly indicates overrotation, & the pedicle (eye) demonstrated anteriorly indicates underrotation.

What is the median sacral crest and where is it on the sacrum?

Fused spinous processes; located on the posterior side of the sacrum.

Spondylolisthesis:

Involves forward movement of one vertebra in relation to another. Commonly due to a developmental defect in the pars interarticularis. Often occurs at L5-S1 or L4-L5.

What is the interiliac line and what is its significance in lateral projections?

It's an imaginary line in between the iliac crests. The CR must be parallel with the interiliac line. If their is insufficient waist support, the CR may have to be angled 5-8 degrees caudad.

Center point for anterior & posterior obliques:

L3 (costal region) or 1.5" above the iliac crest.

The anatomical structure of the lumbar vertebra:

Lateral & superior perspectives: transverse processes, spinous process; Intervertebral foramina: Intervertebral foramen, pedicles, superior vertebral notch, inferior vertebral notch; Z-joints: superior articular processes, inferior articular processes, laminae, & pars interarticularis; Posterior & anterior perspectives: spinous processes & transverse processes.

Best modality used for herniated nucleus pulposus (HNP):

MRI

Compression fractures:

May be due to trauma, osteoporosis, or metastatic disease. The superior & inferior vetebral bodies are driven together, creating a wedge-shaped appearance.

Center point for PA or AP Scoliosis & Erect lateral scoliosis projection:

Midpoint to IR (lower margin of IR is placed 1-2" below iliac crest).

Best modality used for ankylosing spondylitis:

Nuclear medicine bone scan.

What patient position causes a radiographic appearance of "Scottie dogs?" What each aspect of the Scottie dog represents on the vertebra?

Oblique lumbar spine; transverse process (nose), pedicle (eye), pars interarticularis (neck), inferior articular process (front leg), superior articular process (ear). The z-joint is formed by the front leg and the ear.

What is the difference between Osteoblastic & Osteolytic metastases?

Osteolytic are destructive lesions with irregular margins. Osteoblastic are proliferative bony lesions of increased density. A combination of the two will have a "moth-eaten" appearance of bone resulting from the mix of destructive and blastic lesions.

What type of joint movement does the z-joints have?

Plane (gliding).

Metastaes:

Primary malignant neoplasms that spread to distant sites via blood and lymphatics (osteolytic & osteoblastic).

Best modality for scoliosis:

Radiograph

What should be done to help place the patient's spine more parallel to the table/IR when performing lateral projections?

Radiolucent support beneath the waist.

Chance fracture:

Result from a hyperflexion force that causes fracture through the vetebral body. Commonly caused by wearing seat belts during a traffic accident.

CR angles for the axial sacrum & axial coccyx:

Sacrum (15 degrees cephalad); coccyx (10 degrees caudad).

What forms the z-joints of the lumbar and what is their relationship to the midsagittal plane?

Superior articular processes which project upward & the inferior articular process which project downward; z-joints form an angle open from 30 to 50 degrees to the midsagittal plane.

What are the anterior projecting bony processes called? what do these structures help form?

Superior articular processes; they form z-joints with the inferior articular processes of the fifth lumbar vertebrae.

What is the difference in the angle of the sacrum between males and females?

The angle is greater on an average female, as compared with an average male; the forward curvature is more pronounced in males and is less pronounced with less curvature, in females.

What is the topographic landmark of L4-L5?

The iliac crest.

Where is the lamina? What is the portion located between the superior and inferior articular processes?

The lamina can be seen superiorly & posteriorly. They form a bridge between the transverse processes, lateral masses, & spinous process; the pars interarticularis.

What is the topographic landmark of L2-L3?

The lower costal margin.

What is the superior & the inferior aspect of the coccyx called?

The superior aspect is called the base, and the inferior aspect is called the apex.

What is the topographic landmark of the coccyx?

The superior margin of the symphysis pubis or 1" superior to the greater trochanter.

What is the topographic landmark of T9-T10?

The ziphoid tip.

Where are the intervertebral foramina of the lumbar and where are they located in relation to the midsagittal plane?

They are situated 90 degrees relative to the midsagittal plane.

Where are the sacral horns located and what is their other name?

They can be seen laterally and inferiorly on the posterior side of the sacrum (each side of the fifth sacral segment). They are also known as cornua.

Best modality for spina bifida:

Ultrasound, CT, or MRI

For an RAO or LAO lumbar spine, will demonstrate upside or downside z-joints?

Upside

Which SI joints are demonstrated on the posterior oblique projections?

Upside; the base is side up and the apex is side down.

Sponylolysis:

the dissolution of a vertebra, such as from aplasia of the vertebral arch and separation of the pars interarticularis of the vertebra. On an oblique projection, the neck of the Scottie dog appears broken.