Spine and Pelvis
Scoliosis Series
Anatomy & Pathology
Students should be able to identify the following structures on radiographic images:
superior articular process, transverse process, pedicle, pars interarticularis, lamina, inferior articular process, zygapophyseal joint, intervertebral disk space, spinous process, superior vertebral notch, inferior vertebral notch, mamillary process, body, vertebral foramen, intervertebral foramen, sacral promontory, sacral ala, anterior and posterior sacral foramina.
Routine Projections (ARRT Required)
PA (or AP) Upright
CR Location & Positioning
- SID: 60 inches (152 cm) minimum; use department standard for long-length imaging or stitching
- Patient position: Upright, facing IR for PA (preferred to reduce anterior organ dose); arms relaxed at sides
- Adjustments: Center MSP to IR; include base of skull through at least 1 inch (2.5 cm) below iliac crests; use compensating filter or system stitching; level pelvis and equal weight bearing; breast and gonadal shielding when feasible without obscuring anatomy
- CR: Perpendicular to IR, centered to MSP at mid-thoracolumbar region (level adjusted to include entire curve)
- Pt. Instructions: Stand tall, look straight ahead, hold still; suspend respiration
- Exposure: Grid or long-length detector per system; tight lateral collimation; technique to preserve bone and hardware detail across variable thickness
Evaluation Criteria
- Coverage (what anatomy must be included and how you verify it’s complete): Entire spine from skull base through iliac crests (or entire visible curve set) centered on image; hardware included if present
- Rotation checks (how symmetry or alignment tells you if positioning is correct): Spinous processes midline; iliac crests and SI joints symmetric; clavicles symmetric on thoracic portion
- Motion checks (how sharpness confirms patient cooperation/exposure timing): Clear endplates and pedicles; no breathing or sway blur
- Technique checks (what contrast density, soft tissue visibility, and artifacts to look for): Uniform brightness via filter/stitching; no clipped margins; protective shields not overlapping anatomy of interest
- Clinical aim (when applicable, e.g., reflux, obstruction, displacement, etc.): Establish baseline curve magnitude and balance under gravity; document hardware and coronal alignment for Cobb angle measurement
Lateral Upright
CR Location & Positioning
- SID: 60 inches (152 cm) or department standard for long-length imaging
- Patient position: Upright, true lateral stance with equal weight bearing on both feet
- Adjustments:
- Align mid-coronal plane to center of IR (ensure entire spine is within field).
- Keep pelvis neutral (no anterior or posterior tilt).
- Have patient extend arms forward or grasp support bar to clear spine margins.
- Confirm head is neutral (not flexed or extended) and chin slightly elevated for C-spine visualization.
- Use compensating filter (if available) to balance shoulder and pelvic densities.
- CR: Perpendicular to mid-coronal plane at the mid-thoracolumbar region (roughly T12–L1 level).
- Patient instructions: Look straight ahead; suspend respiration and remain still during exposure.
- Exposure: Grid or long-length DR system; tight AP collimation; select technique for variable tissue thickness (shoulders vs pelvis).
Evaluation Criteria
- Coverage: Entire thoracic and lumbar spine included in profile from skull base (if possible) through sacrum; must at minimum include the thoracolumbar junction and lumbar lordosis.
- Rotation checks: Posterior vertebral borders form a single line without double contour; ribs nearly superimposed; pelvis not rotated (anterior superior iliac spines aligned vertically).
- Motion checks: Vertebral margins sharp and distinct; no breathing blur. If breathing technique used, lung markings appear blurred while vertebral bodies remain crisp.
- Technique checks: Adequate penetration through shoulders and pelvis; intervertebral disk spaces visible without burnout; uniform density from thorax to sacrum when using filter or stitching.
- Clinical aim: Evaluate global sagittal alignment (including kyphosis and lordosis), spinal balance, and any spondylolisthesis or postoperative hardware alignment under physiologic load.
Notes for Clinical and ARRT Context
- ARRT classification: This projection meets the ARRT requirement for the “Lateral Upright” projection in the Scoliosis Series.
- Extended clinical use: When captured on a long-length detector or stitched DR image, this projection provides the profile of global sagittal alignment, allowing for quantitative assessment of C7 plumb line, pelvic incidence, and lumbar lordosis relationships.
- Reproducibility: Ensure identical stance, SID, and centering on follow-up studies to allow accurate comparison of curve progression and postoperative correction.
Supplemental Projections
PA Ferguson – Hip/Foot Elevation Test (Primary vs Compensatory)
CR Location & Positioning
- SID: 60 inches (152 cm) or system standard
- Patient position: Upright PA
- Adjustments: First image in neutral upright; second image with hip/foot elevated 3–4 inches (8–10 cm) on the convex side of the primary curve; do not support patient beyond the block (effort required to maintain position); center MSP to IR; include skull base through iliac crests
- CR: Perpendicular to MSP at mid-thoracolumbar region; same centering for both images
- Pt. Instructions: Stand tall; keep arms relaxed; hold still; suspend respiration
- Exposure: Match technique and centering between images; identical collimation for comparison
Evaluation Criteria
- Coverage: Same anatomic extent on both images for side-by-side comparison
- Rotation checks: Midline alignment consistent between images; pelvic leveling documented
- Motion checks: No blur; identical stance except for prescribed elevation
- Technique checks: Comparable exposure values between images; no shield overlap on the spine
- Clinical aim: Differentiate primary (structural) curve from compensatory curve based on change or lack of change with elevation
PA (or AP) Upright With Lateral Bending
CR Location & Positioning
- SID: 60 inches (152 cm) or system standard
- Patient position: Upright PA preferred; perform right-bend and left-bend images
- Adjustments: From neutral, have patient laterally bend toward each side without rotating the trunk or lifting heels; arms positioned to avoid obscuring ribs and lumbar spine; include skull base through iliac crests
- CR: Perpendicular to MSP at mid-thoracolumbar region
- Pt. Instructions: Bend sideways without twisting; hold end position; suspend respiration
- Exposure: Same collimation and technique across both bends for symmetry
Evaluation Criteria
- Coverage: Entire curve set included on both bends
- Rotation checks: Pelvis stays as level as possible; minimal axial rotation (spinous processes remain near midline)
- Motion checks: No motion blur at end-range bend
- Technique checks: Comparable density across both images; lateral soft tissues not clipped
- Clinical aim: Assess flexibility for preoperative planning and to distinguish structural vs flexible (compensatory) curves
Hows & Whys of Scoliosis Radiography
Anatomy
- Which curves are typically assessed in scoliosis surveys?
Primary (structural) and compensatory curves across thoracic and lumbar regions. - Which lumbar landmark helps identify spondylolisthesis on the lateral?
The posterior vertebral body line at L5–S1 relative to the sacral promontory.
Positioning
- Why use PA instead of AP whenever possible?
To reduce radiation to anterior radiosensitive organs (especially breast tissue in adolescents) while still demonstrating the full spine. - Why keep patient unsupported during Ferguson and bending images?
To let gravity and patient effort reveal true curve flexibility versus structural rigidity for surgical planning. - Why use a long SID and compensating filters or stitching?
To reduce magnification and provide uniform exposure across the large thickness range from shoulders to pelvis, ensuring consistent visualization for measurement. - Why insist on equal weight bearing and level pelvis in routine upright views?
To avoid artificial curve exaggeration or pelvic tilt that can mislead Cobb angle assessment. - Why position arms to the side (PA) or forward (lateral)?
To prevent humeri and scapulae from obscuring thoracic vertebrae and to keep the spine margins measurable.\
Technique & Image Evaluation
- How can you tell the routine PA survey is centered and not rotated?
Spinous processes are midline; clavicles and iliac crests appear symmetric; the vertebral column runs down the image center. - How can you tell the Ferguson images are comparable?
Identical collimation and centering with only the prescribed hip/foot elevation changed; overall body alignment otherwise matches. - How can you tell the bending images show lateral bend without rotation?
Spinous processes remain near midline; ribs show minimal axial rotation; pelvis remains close to level. - How can you tell the lateral is a true lateral?
Posterior vertebral body borders and pedicles align; ribs are nearly superimposed; no double contour of vertebral margins. - How can you tell exposure is appropriate across the long field?
Uniform visibility of vertebral bodies and endplates from upper thorax through pelvis without burnout or underpenetration.
Clinical Applications
- When are Ferguson elevations and lateral bends most helpful?
When differentiating structural from compensatory curves and assessing flexibility for bracing or operative planning. - When is a lateral mandatory in a scoliosis series?
When kyphosis/lordosis or spondylolisthesis is suspected, or for postoperative sagittal balance assessment. - When should additional regional views be added?
When focal symptoms or hardware warrant higher-detail evaluation (e.g., targeted lumbar or thoracic series).
