CBP CBP Radiographic Analysis 2 — Questions and Answers
Question 1: What does 'anterior weight bearing' as seen on a lateral lumbar radiograph indicate in CBP assessment?
- The patient was leaning forward during the X-ray exposure
- The plumb line from L1 falls anterior to the sacral promontory, indicating forward sagittal imbalance (Correct answer)
- Increased disc hydration on T2 MRI
- Normal weight distribution across the lumbar spine
Correct answer: The plumb line from L1 falls anterior to the sacral promontory, indicating forward sagittal imbalance
When the sagittal vertical axis (plumb line from L1 or C7) falls anterior to the sacral promontory, CBP identifies this as anterior weight-bearing, indicating sagittal imbalance.
Question 2: In CBP, how is the 'Harrison posterior tangent' (HPT) angle of a vertebra determined?
- By measuring the disc height at adjacent levels
- By drawing a line along the posterior vertebral body surface and measuring its angle to a plumb vertical line (Correct answer)
- By comparing left and right pedicle width on the AP film
- By measuring the distance from the spinous process to the vertebral body
Correct answer: By drawing a line along the posterior vertebral body surface and measuring its angle to a plumb vertical line
The HPT angle is the acute angle formed between the line along the posterior vertebral body and a true vertical (plumb) reference line on lateral radiographs.
Question 3: On a full-spine AP radiograph, what does 'lateral vertebral translation' refer to in CBP?
- Axial rotation of the vertebra on the AP film
- The horizontal (left or right) displacement of a vertebral body relative to the vertebra below or to a gravity line (Correct answer)
- Disc space narrowing in the coronal plane
- Pedicle asymmetry between sides
Correct answer: The horizontal (left or right) displacement of a vertebral body relative to the vertebra below or to a gravity line
Lateral vertebral translation is the side-to-side positional shift of a vertebra's centroid relative to the one below, measured in millimeters on the AP radiograph.
Question 4: According to CBP radiographic protocols, why should full-spine radiographs be taken in the standing (weight-bearing) position?
- It is cheaper and faster to take standing films
- Standing films capture the functional, load-bearing spinal posture that reflects true alignment under gravity (Correct answer)
- Supine films are reserved for post-treatment only
- Standing films reduce radiation exposure significantly
Correct answer: Standing films capture the functional, load-bearing spinal posture that reflects true alignment under gravity
CBP emphasizes weight-bearing films because gravity-loaded posture reveals the true structural and functional alignment that determines clinical outcomes and treatment targets.
Question 5: Which measurement on an AP cervical radiograph helps identify a lateral cervical translation in CBP?
- The Cobb angle between C2 and C7 vertebral endplates
- The horizontal offset of C7 centroid relative to the C2 centroid or a central gravity line (Correct answer)
- The disc height ratio at C5-C6
- The foraminal width on the left versus right
Correct answer: The horizontal offset of C7 centroid relative to the C2 centroid or a central gravity line
Comparing the horizontal positions of vertebral centroids (or C7 relative to C2) on the AP view reveals lateral translation of the cervical column from its ideal midline position.
Question 6: In CBP outcome studies, which radiographic parameter is most commonly used to verify structural correction after treatment?
- Change in disc height (mm)
- Change in Cobb angle or posterior tangent angle of the treated spinal region (Correct answer)
- Change in vertebral body bone density
- Change in foraminal opening size
Correct answer: Change in Cobb angle or posterior tangent angle of the treated spinal region
CBP outcome research primarily uses before-and-after angular measurements (Cobb or posterior tangent angles) to document and verify structural spinal correction.
CBP CBP Radiographic Analysis 2
What does 'anterior weight bearing' as seen on a lateral lumbar radiograph indicate in CBP assessment?