Chapter 8Lumbar Spine, SI Joints, Sacrum & CoccyxDarv Nomann R.T. (R)
Anatomy: Vertebral Column
Forms the central axis of the skeleton
Centered in the midsagittal plane
Located in posterior trunk
Functions
Encloses and protects spinal cord
Supports trunk and skull
Provides muscle attachments
Anatomy: Vertebral Column
Composed of small, irregular bones called vertebrae
Total of 33 vertebrae in early life
24 are true, moveable vertebra
Sacral and coccygeal segments are false, fixed vertebra
•Sacral vertebrae fuse into the sacrum
•Coccygeal vertebra fuse to form coccyx
Anatomy: Vertebral Column
Divided into five groups named according to region they occupy
Cervical vertebrae
Thoracic vertebrae
Lumbar vertebrae
Sacral vertebrae
Coccygeal vertebrae
Anatomy: Vertebral Column
Has four curves that arch anteriorly and posteriorly from midcoronal plane
Lordotic curves are convex anteriorly
Kyphotic curves are concave anteriorly
Anatomy: Vertebral Column
Each curve named for region
Cervical = lordotic
Thoracic = kyphotic
Lumbar = lordotic
Pelvic = kyphotic
Scoliosis is a condition of abnormal lateral curvature of the spine
Kyphosis is a condition of increased kyphotic curve of T-spine
Anatomy: Vertebral Column
Vertebrae separated by intervertebral disks, composed of fibrocartilage
Function as cushions
Anatomy: Vertebral Column
Disc composed of
Annulus fibrosus – outer, fibrocartilaginous disk
Nucleus pulposus – central, soft mass
HNP = herniated nucleus pulposus
“Slipped disk”
Anatomy: Vertebral Column
Anterior and lateral aspects of vertebral column
Anatomy: Typical Vertebra
Transverse processes project laterally and a little posteriorly
Spinous process projects posteriorly and inferiorly
Spina bifida is congenital condition in which the laminae fail to fuse
Anatomy: Typical Vertebra
Superior aspect
Lesson 3
Anatomy of the Lumbar Spine, SI Joints
Sacrum, and Coccyx
Anatomy: Lumbar Vertebrae
Five in number
Occupy the posterior abdominal region
Unique features:
Transverse processes are smaller than T-spine
Pars interarticularis – part of lamina between articular processes
Anatomy: Lumbar Vertebrae
Superior aspect of lumbar vertebrae
Anatomy: Sacrum
Formed by fusion of five sacral segments into curved, triangular bone
Wedged between iliac bones of pelvis
Articulation = sacroiliac (SI) joints
Anatomic features
Promontory
Canal
Foramina
Cornu
Anatomy: Coccyx
Formed by fusion of three to five rudimentary vertebrae
Curves inferiorly and anteriorly from articulation with sacrum
Anatomic features
Cornu
Anatomy: Sacrum and Coccyx
General Procedural Guidelines
Patient preparation
General patient position
IR size
SID
ID markers
Radiation protection
Patient instructions
Patient Preparation
Patient preparation for middle to lower vertebral column procedures requires removal of artifacts from the anatomy of interest.
Necklaces
Clothing artifacts
Patient Preparation
Provide gown
Secure patient possessions in designated manner and location
General Patient Position
Ambulatory patients
Upright or recumbent
Nonambulatory patients
Alter positioning to maximize patient comfort
Trauma patients
Move IR and CR to obtain images to maximize patient safety (see Chapter 13, pp. 28 and 32)
IR Size
Textbook gives guidelines
Use smallest IR that will demonstrate anatomy
Collimate field size to anatomy of interest
SID
SID is standardized as a part of procedural protocol
When SID is not specified under a projection, Merrill’s Atlas recommends 48 (122 cm)
ID Markers
Right or left side markers must be included on each image
Other required ID markers must be in the blocker or elsewhere on the final image
Radiation Protection
Shield pediatric patients and patients of reproductive age
Refer to guidelines on p. 390, Volume 1
Other radiation protection measures
Close collimation
Optimum technique factors
Patient Instructions
Explain positions, procedures, and breathing instructions
Respiration is suspended during most middle to lower vertebral column projections
Radiographic Procedures
Essential Projections of the
Lumbar Spine (L-Spine), SI joints, Sacrum, and Coccyx
Essential Projections: L-Spine
AP
Lateral
Lateral L5-S1
AP oblique
RPO
LPO
AP axial L-S junction and SI joints (Ferguson)
AP L-Spine
Patient position
Supine or upright
Part position
MSP centered to midline
Shoulders and hips in same horizontal plane
Arms crossed on chest
Reduce lordosis by flexing hips and knees to place lower back closer to table
AP L-Spine
CR
Perpendicular to IR
For 35- × 43-cm IR, enters patient at iliac crests (L4)
For 30- × 35-cm IR,enters patient at 1.5 (3.8 cm) above iliac crests (L3)
Lateral L-Spine
Note: L-spine intervertebral foramina is demonstrated.
Patient position
Recumbent or upright
Use same as for AP
Lateral L-Spine
Part position
True lateral with MCP vertical
Knees flexed and superimposed
Arms, with elbows flexed, at right angle to body
Place radiolucent support under lower spine to place horizontal, if needed
Lateral L-Spine
CR
Perpendicular to IR
For 35- × 43-cm IR, enters patient on MCP at iliac crests (L4)
For 30- × 35-cm IR, enters on MCP at 1.5
(3.8 cm) above iliac crests (L3)
If spine is not horizontal, angle caudad
5 to 8 degrees
•More for females
Lateral L-Spine
Collimated field
Collimate and use lead behind patient to reduce scatter
All five lumbar vertebrae
•Most of sacrum if using larger IR
Lateral L5-S1
Patient position
Lateral recumbent
Lateral L5-S1
Part position
MCP perpendicular to IR
Hips extended
Superimposed knees, may be slightly flexed
With elbows flexed, place arms at right angle to body
Support lower spine in horizontal position in same manner as for lateral projection
Lateral L5-S1
CR
When spine is horizontal, perpendicular to a coronal plane 2 (5 cm) posterior to ASIS and 1.5 (3.8 cm) inferior to iliac crest
•If not, angle 5 degrees caudad for males, 8 degrees caudad for females
Francis1 suggests alternative CR aligned with interiliac plane
•Refer to textbook, Fig. 8-102
1Francis C: Method improves consistency in L5-S1 joint space films, Radiol Technol 63:302, 1992.
Lateral L5-S1
Collimated field
Includes all of L5 and S1
AP Oblique L-Spine
Note: Zygapophyseal joints of L3-L4 and L4-L5 are demonstrated.
Note: Both sides are examined for comparison.
AP Oblique L-Spine
Patient position
Recumbent or upright
Use same position as AP
Part position
45-degree posterior oblique position
Radiolucent support under elevated side
AP Oblique L-Spine
CR
Perpendicular to IR
Enters patient 2 (5 cm) medial to elevated ASIS at L3 (1.5 or 3.8 cm above iliac crests)
Collimated field
Includes all five lumbar and top of sacrum
AP Axial (Ferguson)
Patient position
Supine
Part position
MSP centered to IR
Extend lower limbs, or abduct thighs and place vertical
AP Axial (Ferguson)
CR
Angled cephalad 30 to 35 degrees
•Use less angle on males, more on females
•Ferguson originally recommended 45-degree angle
Enters patient on MSP at 1.5 (3.8 cm) above pubic symphysis
AP Axial (Ferguson)
Collimated field
Includes entire sacrum and medial borders of ilia
Note: May also be performed with patient in prone position (PA axial) with CR angle
35 degrees caudad. Only AP axial is referred to as Ferguson method.
Essential Projections: SI Joints
AP Oblique
RPO
LPO
AP Oblique SI Joints
Note: SI joint farther from IR is demonstrated. Both sides are examined for comparison.
Patient position
Supine
AP Oblique SI Joints
Part position
25- to 30-degree posterior oblique position
Support body in position
Long axis parallel with table
IR centered at level of ASIS
AP Oblique SI Joints
CR
Perpendicular to IR
Enters patient 1 (2.5 cm) medial to elevated ASIS
Essential Projections: Sacrum and Coccyx
Sacrum
AP axial
Lateral
Coccyx
AP axial
Lateral
Note: Bowel should be prepped and bladder emptied before examination.
AP Axial Sacrum
Patient position
Supine
May also be performed with patient prone (PA axial projection), if needed for comfort
AP Axial Sacrum
Part position
MSP in midline of table
ASIS equidistant from table
Arms in comfortable, symmetric position out of field
Support knees, if supine
AP Axial Sacrum
CR
15 degrees cephalad, if supine
•15 degrees caudad for prone
Enters MSP at 2˝ (5 cm) superior to pubic symphysis
•For prone – enters MSP at level of sacral curve
Collimated field
Includes entire sacrum and SI joints
AP/PA Coccyx
Patient position
Supine or prone
Choose position that maximizes patient comfort
Part position
Same as used for sacrum
AP/PA Coccyx
CR
Angled 10 degrees caudad
•10 degrees cephalad if PA performed
Enters MSP at 2 (5 cm) superior to pubic symphysis
•For PA, enters MSP at coccyx
Collimated field
Includes entire coccyx
Collimate for improved visibility
Lateral Sacrum
Patient position
Recumbent lateral
Hips and knees flexed for comfort
Lateral Sacrum
Part position
Arms at right angle to body
Knees superimposed
Support spine to horizontal position
Interiliac plane perpendicular to IR
Shoulders and pelvis in true lateral
•MCP vertical
Sacrum centered to IR
Lateral Sacrum
CR
Perpendicular to perpendicular to level of ASIS and to a point 3.5 (9 cm) posterior
Collimated field
Close collimation improves contrast and visibility
Lead rubber behind patient absorbs scatter
Lateral Coccyx
Patient and part positions
Same as used for sacrum
Lateral Coccyx
CR
Perpendicular to 3.5 (9 cm) posterior and 2
(5 cm) inferior to ASIS
Collimated field
Close collimation improves visibility
Lead rubber behind patient absorbs scatter
Lesson 4
Image Critique of the
Lumbar Spine, SI Joints, Sacrum and Coccyx
AP L-Spine
Area from lower T-spine to sacrum
Collimated to psoas muscles
No artifacts from underclothing
X-ray penetration of vertebral structures
Open intervertebral joints
SI joints equidistant from spine
Symmetric vertebrae with spinous processes in center of bodies
Projection? Anatomy?
Lateral L-Spine
On 35- × 43-cm IR, lower thoracic to coccyx shown
On 30- × 35-cm IR, lower thoracic to sacrum shown
Open intervertebral disk spaces and intervertebral foramina
Lateral L-Spine
No rotation
Superimposed posterior margins of bodies
Nearly superimposed iliac crests (if CR is not angled)
Spinous processes in profile
Vertebrae in middle of collimated field
Projection? Anatomy?
Lateral L5-S1
Open L5-S1 intervertebral joint
Field includes all of L5 and upper sacrum
L5-S1 joint in center of field
Iliac crests nearly superimposed, if CR is not angled
Projection? Anatomy?
AP Oblique L-Spine
Area from lower T-spine to sacrum shown
Zygapophyseal joints closer to IR open and visible through bodies
If joint is not open and pedicle is anterior on body, patient is not rotated enough
If joint is not open and pedicle is posterior on body, patient is rotated too much
T12-L1 and L1-L2 intervertebral joint spaces open
Projection? Anatomy?
AP Oblique L-Spine
AP Axial LS Junction and SI Joints (Ferguson)
LS junction and sacrum
Open L5-S1 intervertebral space
Both SI joints penetrated
Projection? Anatomy?
AP Oblique SI Joints
Open SI joint space with minimal overlap of ilium and sacrum
Joint in center of image
Projection? Anatomy?
AP Axial Sacrum
Sacrum demonstrated without foreshortening and with curve straightened
No overlap by pubic bones
Short-scale contrast
Improved by close collimation
AP Axial Sacrum
No rotation
Alae symmetric
Sacrum centered and seen in its entirety
Fecal material not overlapping sacrum
Projection? Anatomy?
AP/PA Coccyx
Coccygeal segments not superimposed
Short-scale contrast
Improved by tight collimation
No rotation
Projection? Anatomy?
Lateral Sacrum and Coccyx
Sacrum and coccyx seen with short-scale contrast
Improved by close collimation and use of lead rubber behind patient
No rotation
Posterior margins of ischia and ilia nearly superimposed
Projection? Anatomy?