Chapter 8



Chapter 8

Lumbar Spine, SI Joints, Sacrum & Coccyx

Darv 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?

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