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Spine and Pelvis

30 Scoliosis Series

Anatomy & Pathology

Anatomy and Key Landmarks

  • Vertebral body
  • Pedicles and laminae (vertebral arch)
  • Spinous and transverse processes
  • Superior and inferior articular processes
  • Zygapophyseal (facet) joints
  • Intervertebral disks and foramina
  • Pars interarticularis and mamillary process (lumbar)
  • Sacral promontory and ala
  • Anterior and posterior sacral foramina

Common Pathology 

  • Idiopathic scoliosis (primary and compensatory curves)
  • Congenital and neuromuscular scoliosis
  • Spondylolisthesis (most commonly at L5–S1)
  • Exaggerated kyphosis or lordosis
  • Postoperative alignment (e.g., rods, pedicle screws)

Routine Projections

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

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

Lateral Upright – Profile of Global Sagittal Alignment

CR Location & Positioning

  • SID: 60 inches (152 cm) or system standard
  • Patient position: Upright true lateral; arms forward or hugging support to clear spine; equal weight bearing
  • Adjustments: Center mid-coronal plane to IR; include from skull base through iliac crests; use compensating filter for shoulders and pelvis if available
  • CR: Perpendicular to mid-thoracolumbar region, mid-coronal plane
  • Pt. Instructions: Look straight ahead; keep still; suspend respiration
  • Exposure: Grid or long-length detector; tight AP collimation; technique for lateral thickness and shoulder density

Evaluation Criteria

  • Coverage: Thoracic and lumbar vertebrae in profile from T1 (as feasible) through sacrum; at minimum, thoracolumbar junction and lumbar lordosis included
  • Rotation checks: Posterior vertebral borders in single line; ribs nearly superimposed; pelvis not rotated
  • Motion checks: Sharp vertebral margins; no breathing blur
  • Technique checks: Adequate penetration through shoulders and pelvis; open intervertebral spaces where possible
  • Clinical aim: Evaluate sagittal balance, kyphosis/lordosis, and spondylolisthesis under physiologic loading

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).

 

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Radiographic Procedures Review Guide Copyright © 2025 by Carla M. Allen and Taylor M. Otto is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, except where otherwise noted.