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sacrum/coccyx

Terms in this set (15)

In order to minimize distortion of the sacrum in frontal projections, which of the following is the most correct angulation of the central ray?
15 degrees cephalad
The sacrum exhibits a concave anterior surface and a convex posterior surface in normal adults. Females typically have a slightly more pronounced curvature. In order to demonstrate this bone with minimal shape distortion, the central ray should be directed to be perpendicular to the anterior surface of the bone. In the average adult, a 15 degree cephalad angulation of the central ray will be perpendicular to the body of the sacrum.
When performing an AP axial projection of the sacrum, the central enters at the midsagittal plane (MSP) and:
2 inches superior to the pubic symphysis.
The sacrum forms the posterior portion of the pelvic girdle, and lies between the two hip (innominate) bones. When the central ray is angled to demonstrate a non-distorted image of the sacrum the central ray should enter the MSP at a point approximately 2 inches superior to the pubic symphysis and pass through the body of the sacrum.
Which of the following bony landmarks lies at the same level as the superior border of the pubic symphysis?
Prominence of the greater trochanter
While many radiographic positioning texts cite the pubic symphysis as a bony positioning landmark for abdominal and pelvic radiographs, it is embarrassing for many technologists to palpate this structure. It is therefore useful to remember that the prominence of the greater trochanter lies at the same level as the superior border of the pubic symphysis and the tip of the coccyx. Lateral rotation of the femur makes palpation of the greater trochanter easy and is less embarrassing.
Which of the following structures is/are part of the sacrum?1. Promontory2. Transverse foramina3. Auricular surface
1 and 3
The promontory of the sacrum is the prominent ridge on the anterior surface of the first sacral segment. The auricular surfaces are on the lateral sacrum where it articulates with the hip (innominate) bones. Transverse foramina are only found in the cervical region of the spine and allow for transmission of the vertebral arteries.
A patient presents in the Emergency Department with severe pain in the inferior spine after falling on the ice. A coccyx examination is ordered. When performing the lateral projection of the series, what is the appropriate central ray entrance point?
3.5 inches posterior and 2 inches inferior to the ASIS.
In order for the central ray to pass through the coccyx, it should enter the body more inferiorly than for sacral or combined sacral/coccygeal images. For dedicated lateral coccyx images, the central ray enters the body 3-4 inches posterior to the ASIS and approximately 2 inches inferior to the level of the ASIS.
Which of the following is/are appropriate evaluation criteria for an AP projection of the sacrum?
1. Sacrum free of superimposition by the pubic symphysis
2. Open L5/S1 joint space
3. Superimposition of the sciatic notches
1 only
When properly performed, an AP radiograph of the sacrum will demonstrate the bone free of superimposition by the pubic symphysis. The sacroiliac (SI) joints should be visualized and appear symmetrical to indicate that the patient was in a true AP position with no rotation. With the correct angulation of the x-ray beam, the sacral foramina should be open and well-demonstrated. The sciatic notches are superimposed on the lateral projection.
An AP projection of the coccyx demonstrates the coccyx superimposed by the superior rami of the pubic bones. What correction, if any, should be made?
Increase the caudal angulation of the tube.
The x-ray tube should be angled 10 degrees caudad to place the beam perpendicular to the coccyx and separate the coccyx from the pubic symphysis. This will demonstrate the entire coccyx above the pubic symphysis. If there is superimposition of these structures, then the x-ray beam should be angled more caudally which will project the pubic symphysis lower on the image and away from the coccyx.
What is the appropriate central ray angulation and entrance point for an AP axial projection of the coccyx?
10 degrees caudad entering midsagittal plane at a level 2 inches superior to the pubic symphysis.
The coccyx curves anteriorly and so to minimize distortion the central ray is angled 10 degrees caudad. This angulation places the central ray perpendicular to the coccyx. The central ray entrance point should be at the midsagittal plane and approximately 2 inches superior to the pubic symphysis in order to compensate for this angulation.
Which of the following is/are appropriate evaluation criteria for a lateral projection of the sacrum?
1. Symmetrical sacral foramina
2. Greater sciatic notches are superimposed
3. Superimposition of the femoral heads
2 and 3
When the patient is properly positioned for a lateral sacrum image, the bone should be demonstrated in lateral profile and the hip bones and femurs should be directly superimposed. This can easily be evaluated by examining the greater sciatic notches and the posterior borders of the ischial bones. Sacral foramina are visible on AP axial images of the sacrum rather than on the lateral.
When evaluating an AP axial projection of the coccyx, the technologist notices that the obturator foramina are symmetrical, and that the coccyx is just superior to and in the same plane as the pubic symphysis and is superimposed by the bladder. What positioning error, if any, has been made with this image?
No mistake has been made; this is an acceptable image.
A properly positioned AP axial coccyx image will demonstrate a symmetrical appearance of the obturator foramen and pubic bones. The coccyx should be free of superimposition by the pubic bones, and generally lies in the midline. The coccyx will normally be superimposed by the urinary bladder.
The sacroiliac joints are classified as which of the following?
Synovial, gliding
The SI joints are articulations between the auricular surfaces of the sacrum and the iliac bones. These joints are considered synovial, irregular gliding joints.________________
Should this image of the sacrum be repeated? Why or why not?
No, all required anatomy is included and the patient is correctly positioned
When the patient is properly positioned for a lateral sacrum image, the bone should be demonstrated in lateral profile and the hip bones and femurs should be directly superimposed. This can easily be evaluated by examining the greater sciatic notches and the posterior borders of the ischial bones. Sacral foramina are visible on AP axial images of the sacrum rather than on the lateral.
Which letter on the image below is pointing to the sacral promontory?
E
The promontory of the sacrum is the prominent ridge on the anterior surface of the first sacral segment and is identified by the letter E. A refers to the superimposed superior articular processes; B is the median sacral crest; C is pointing to the greater sciatic notch.
In an infant, the sacrum is normally composed of how many segments?
5
At birth, the sacrum is normally composed of 5 segments of bone which usually fuse into a single bone by adulthood. The coccyx is composed of 3-5 segments at birth which fuse into a single bone by adulthood.
Which letter on the image below is pointing to the superior articular process?
A
A refers to the superimposed superior articular processes; B is the median sacral crest; C is pointing to the greater sciatic notch; D is pointing to the intervertebral foramina of L4; and E is pointing to the sacral promontory.
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