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).
