SI Joints, Sacrum and Coccyx, Scoliosis Flashcards
AP Axial SI Joint
- Pt. supine with legs extended - check for rotation
- CR: 30 for males, 35 for females
- CP: 2” superior greater trochanters at MSP OR 2” inferior ASIS
- suspend respiration
AP Axial SI Joint Evaluation Criteria
- no rotation
- Both SI joints demonstrated without superimposition from the superior pubic ramus
- open lumbosacral joint (L5/S1)
PA Axial SI Joints
- Pt. prone - check for rotation
- CR: 30 caudad for males
- CR: 35 for females
- CP: PSIS at MSP
- suspend respiration
If pubic symphysis is superimposed with the SI joints what does that mean in regards to the angle that was used?
there is too much angle
AP Oblique SI Joints
- rotate patient 25-30 from supine
- use sponges - keep entire body straight
- side furthest from IR is demonstrated - the raised side
- CR: perpendicular
- CP : 1” medial to raised side ASIS - at the level of the ASIS
- suspend respiration
AP Oblique SI Joint Evaluation Criteria
- open SI joint
- AP - center on the raised side
- minimal overlapping of the ilium and sacrum
AP Axial Sacrum
- Pt. prep - empty bladder - ordering physician may request a cleansing enema
- hospital pants
- pt. supine legs extended
- CR: 15 cephalad
- CP: 2” superior to pubic symphysis or 2” below ASIS at MSP
AP Axial Sacrum Evaluation Criteria
- No rotation
- Entire Sacrum with no foreshortening
- Pubic bones not overlapping sacrum
- tight collimation
- open sacral foramina
AP Coccyx
- Pt. supine - legs extended
- CR: 10 caudad
- CP: 2” superior pubic symphysis at MSP
What image is a good example of a bisecting angle technique?
AP Axial Sacrum
AP Coccyx Evaluation criteria
- entire coccyx demonstrated with segments not superimposed
- no rotation
- tight collimation
- no superimposition with pubic bones; coccyx must be superior (and should be in line with pubic symphysis)
Lateral Sacrum/coccyx
- Pt. on left side with knees flexed
- CP: 3.5-4” posterior to the ASIS (textbook answer)
- CP: dependant on knee flexion and pelvic tilt - midway between crest and trochanters
- Align CR so it passes through both PSIS (small caudad angle)
- lead masking on table
- always include coccyx
Lateral Sacrum/coccyx evaluation criteria
- sacrum and coccyx should both be seen clearly
- tight collimation
- superimposed acetabula and greater sciatic notches
Lateral coccyx
- pt. on left side
- CR: perpendicular
- CP: 3.5-4” posterior to ASIS and 2” superior level of greater trochanter
- light below level of greater trochanter
- sponge under the lower back/ asses for angle with PSIS
- lead masking on table
Lateral coccyx evaluation criteria
lateral coccyx visualized completely, including distal end of sacrum
What is scoliosis?
idiopathic, functional, neuromuscular and degenerative
When does scoliosis appear?
idiopathic typically appears during adolescence
What must we consider when imaging scoliosis?
- How much deformity does the patient have - determines hoe much we collimate
- Can the patient stand
- How old is the patient - most are adolescents - rad protection - high kVp and low mAs - image PA
- image quality - see entire spine on 1 image
CR Stitching for Scoliosis
- 2-3 CR cassettes can be attached together to achieve desired length
- uses computer software called image stitching to produce one image from all the cassettes
- follow procedures and protocols of specific vendor
Scoliosis classifications
non-structural (secondary or compensatory)
structural
what is non-structural scoliosis?
- temporary curvature
- muscle spasm, leg length discrepancy, hip dysplasia, poor posture or just to compensate for structural curve
- curve disappears when supine, with side bending or the cause is removed
what is structural scoliosis?
- curvature is permanent (unless treatment is offered)
- curve does not disappear when supine or with side bending
- sometimes referred to as the “primary” curve
structural scoliosis imaging considerations
- primary or structural curves need to be repaired if large enough
- body produces a compensatory curve (Secondary, non-structural) to keep the body aligned
- compensatory curve will be in the opposite direction from the primary or structural curve
- when supine, eliminating gravity eliminates the compensatory curve
- rotation in addition to lateral curvature - vertebral body rotates towards convex side of the curve
What views are acquired. in a scoliosis series?
- AP/PA upright
- AP/PA supine/prone
- AP/PA with lateral bending
- Lateral Upright
Why do we perform an AP/PA upright?
to assess the degree of curvature (Cobb angle) with the force of gravity
Why do we perform an AP/PA supine/prone?
to assess structural from non-structural curves
Why do we perform an AP/PA with lateral bending?
to assess primary from secondary curves and mobility
Why do we perform a lateral upright?
to assess the degree of kyphosis or lordosis - degree of anterior or posterior curvature
PA or AP upright
- allow patient’s arms to hang relaxed
- do not support patient
- do not use a compression band
- include from base of skull to ASIS/PSIS
- minimum SID of 150 cm
- CP depends on CR vs DR
Degree of Curvature
Cobb Angle
- determine the vertebra whose endplates are most tilted towards each other
- lines are drawn along the top of the superior tilted vertebra and the bottom of the inferior tilted vertebra
- two more lines are drawn at an angle of 90 of these lines, so that they intersect
- the resulting angle = Cobb angle
Cobb angle indications
- less than 20 normal
- 20 - 40 = brace (can stop progression if caught early on)
- > 40 - 50 = rods, spinal fusion
Lateral upright
- do not use compression band
- support arms - straight ahead
- EAM to ASIS
- SID min of 150cm
- CR: perpendicular
- CP: depends on CR vs DR
- Assesses degree of kyphosis and lordosis
Side bending images
- to assess structural from non-structural curves
