Small Animal Vertebral Column

To preserve space, the radiographs presented in this chapter do not show collimation. For safety, always collimate so that the beam is limited within the image receptor edges. In film radiography, you should see a clear border of collimation (frame) on every radiograph. In some jurisdictions, evidence of collimation is required by law.

Survey axial skeletal imaging does have limited diagnostic value in neurological disease and may be insufficient in conditions of the vertebral column, such as trauma. Definitive evidence may need to be obtained by myelography, computerized tomography (CT), or magnetic resonance imaging (MRI).¹^,² When these modalities are available, they have largely replaced radiography for spinal disease/trauma diagnosis in referral practices.

However, in spite of the limitations, proper survey vertebral radiographs are a valuable tool for those patients who have suffered spinal injuries and present with paresis or paralysis, either partial or complete. In addition, survey radiographs can demonstrate many of the signs consistent with intervertebral disk protrusion. Common intervertebral disk protrusion sites are T12 to T13, T13 to L1, C2 to C3, and C3 to C4.¹

High-quality images are needed to see subtle changes in bone opacity, shape, and angulation of the vertebrae or vertebral column¹^,² (Table 20.1). The common views of this portion of the axial skeleton are the lateral (L) and ventrodorsal (VD) views of the cervical, thoracic, thoracolumbar, lumbar, lumbosacral, sacral, and caudal vertebrae. Depending on the size of the patient, a full survey study is either four or five images of each orthogonal view.

TABLE 20.1

Protocol for Spinal Radiography
ANATOMICAL LOCATION	ROUTINE VIEWS	ANCILLARY VIEWS
Cervical vertebrae	Lateral, Ventrodorsal Center at C3–C4	Hyperextended or hyperflexed lateral, open-mouth ventrodorsal, coned-down views, oblique
Thoracic vertebrae	Lateral, Ventrodorsal	Oblique, dorsoventral
Thoracic vertebrae	Center at T6–T7	Coned down (T6–T7)
Thoracolumbar vertebrae	Lateral, Ventrodorsal Center at thoracolumbar junction	Oblique
Lumbar vertebrae	Lateral, Ventrodorsal Center at L3–L4	Oblique
Lumbosacral vertebrae	Lateral, Ventrodorsal Center at lumbosacral junction	Hyperextended or flexed lateral

• Survey radiographs of a large dog center at C3 to C4, T6 to T7, thoracolumbar, L4, and lumbosacral
• Small dog survey radiographs center at C3 to C4, T6 to T7, L4, and lumbosacral

Cat survey studies of the vertebrae are often part of the whole-body view. For both the dog and the cat, coned-down views are important for areas of interest. Dynamic views of the vertebrae are not common in cats but can be completed.

See Appendix D on the Evolve website for information on the vertebral number and characteristics of the vertebrae of some common species.

Radiographic Concerns

• Each of the vertebral segments and adjacent intervertebral disks generally need to be examined, so correct positioning and attention to detail are essential to produce images of diagnostic value. This means centering the primary beam on the particular area of interest and tightly collimating immediately adjacent to the spine to increase the detail and contrast.
• Remember that the x-ray beam diverges from the central ray, so it is important to use smaller cassettes and take multiple views. Limit the number of vertebrae examined so that the intervertebral disk spaces are more perpendicular to the central beam. The farther away the area of interest is from the central beam, the greater the geometrical variation and the more inaccurate the interpretation of that area. Intervertebral spaces at the periphery of radiographs often appear falsely narrowed.³ Coned-down views give further high-quality images.
• Having the anatomy parallel to the image receptor and perpendicular to the center of the beam is also essential for accurate diagnosis.
- • Tape placed along the spine may assist in proper alignment ⁴ (Fig. 20.1).
  
  FIG. 20.1 Placing tape along the vertebrae helps maintain correct alignment and position. A small foam pad under the nose may be required. A line drawn between the greater trochanters should be perpendicular to the table.
- • Use sponges or cotton padding between the limbs and under the sternum to keep the spine parallel to the tabletop, avoid any sagging, and prevent axial rotation.
- • Sandbags can also be used for positioning on areas that will not be in the field of view.
- • For patients without spinal cord injuries, pulling and supporting the front and hind limbs in opposite directions keeps the thoracolumbar vertebral column extended to a near-parallel position, as well as opening the intervertebral spaces.¹^-³
• Choose a high-detail cassette/film combination if film is used. Low kilovoltage (kV) and high milliampere-seconds (mAs) provide better radiographic contrast, and the use of a grid further increases the contrast. Ensure there is enough kV for penetration and mAs for film darkening or signal (digital film).
• If using digital imaging, utilize appropriate algorithms to process raw data to prevent a sudden transition between bone and soft tissue that can create an artificial dark halo around the vertebrae.²
• The directional and identification labels should be in the field of view, but be conscious of overlapping the label on important anatomy, especially in VD views.
- • For lateral views, place the label along the dorsum.
- • In the VD views, the label may have to be taped to the patient in lieu of being placed on the image receptor.
• The hair coat should be clean and dry. Remove the collar for any cranial and cervical views. The bladder and colon should be emptied, as material within the colon or a distended bladder can create multiple superimposed shadows that might interfere with diagnosis.
• Generally it is more comfortable for right-handed radiographers to place the dog or cat in right lateral recumbency, but either side can be dependent.
• General anesthesia should be used to achieve accurate positioning with muscle relaxation; otherwise false narrowing of the intervertebral disk spaces due to muscle spasm may occur.¹^,²^,⁵
• Because most feline patients requiring vertebral radiography likely present with spinal injury, sedation or general anesthesia and gentle handling are needed.
• If trauma is suspected, ensure that any concurrent issues such as thoracic pathology are addressed before obtaining the radiography.
• If the patient is compromised, VD views can also be made using the horizontal cross-table beam with the patient in lateral recumbency. This is especially useful if vertebral body fractures are suspected.
• Dorsoventral (DV) views (ancillary view) are not as accurate because of the increase in object-film distance (OFD). Also, it may be more difficult to obtain a parallel technique if the animal is in the DV position.
• Hyperflexion and hyperextension views (ancillary views) can further evaluate the caudal aspect of the lateral cervical and the lumbosacral vertebrae if the patient is chemically restrained and will not be traumatized by such handling. Be extremely gentle with handling.

Technician Notes

To understand the importance of and to demonstrate the optical illusion of variation in spacing that occurs farther from the central beam, evenly place a row of pennies on a 5-cm sponge about half an inch (1.5 mm) apart along the center length of the image receptor. Take an x-ray (suggested technique of 50 kV and 2 mAs) and look at the image. On the resulting image notice how the spacing between the pennies appears to distort as they progress toward the outside edges of the film.

Technician Notes

In general, each vertebra is made up of a body (the denser ventral portion, which is separated from the bodies of adjacent vertebra by intervertebral disks), vertebral arch (located dorsal to the body), and various processes (the cranial and caudal articular processes, the dorsal spinous process, and the lateral transverse process) (see Figs. 20.3, 20.9, 20.16, and 20.17).

The first letter designating each group, followed by the number of vertebrae in each group, is the vertebral formula. The vertebral formula for a dog and cat is C₇T₁₃L₇S₃Cd_6-20.

Technician Notes

The vertebral column is divided into five regions: cervical (neck), thoracic (chest), lumbar (abdomen), sacral (pelvis), and caudal (tail). To refer to a particular vertebra, use abbreviations for the region followed by the number within the region, beginning at the cranial end. For example, T12 is the twelfth thoracic vertebra. The abbreviation for caudal vertebrae is Cd (although sometimes the tail vertebrae are referred to as coccygeal and the abbreviation is Cy).

Technician Notes

Note that the positioning itself is fairly similar for most of the lateral and ventrodorsal views of the vertebrae. Keep important principles in mind.

Technician Notes

Remember to collimate tightly to the vertebrae. Place the label/marker on the dorsal aspect for the lateral views. For VD views, tape the marker on the body or place it on the table in an area that will not obscure important anatomy.

Cervical Vertebrae

Lateral View of the Cervical Vertebrae—Routine

Technician Notes

Strategically used positioning aids give the patient the illusion that it is being held.

Technician Notes

Pulling the front limbs caudally prevents shoulder soft tissue from overlapping the spine.

Technician Notes

Be extra careful when manipulating small-breed dogs that present with apparent neck pain.

Technician Notes

Quickly go through your mental checklist before pushing the exposure button: settings correct; image receptor/machine/grid in position; proper location of markers and ID (if using at this stage); correct body part and view; properly centered; borders correct and collimated; patient properly prepared, positioned, and restrained so the vertebrae are in the same horizontal plane as the sternum for the lateral and superimposed for the VD, and parallel to the image receptor. The central ray is perpendicular to the field of view and the receptor.

Ventrodorsal View of the Cervical Vertebrae

Positioning

Place In: Dorsal recumbency in a V-trough or supported by tape/Velcro strapping or sandbag if needed.
Hind Limbs: Place the pelvic limbs in a neutral position and secure with sandbags.
Forelimbs: Evenly position the forelimbs caudally and secure with a sandbag.
Head/Neck/Sternum: Keep the head in a natural position with the nose slightly up to minimize the curvature of the cervical spine. Secure with padding lateral to the head and neck. Keep the sternum superimposed over the vertebrae.
Vertebrae: Use padding beneath the rostral neck to keep the cervical vertebrae parallel to the table.

Comments and Tips

• If possible, angle the beam in a slight caudocranial direction (20 degrees) between the intervertebral spaces to improve visualization of the disk spaces because they slope caudally in the VD position.
• Make sure that the sternum and vertebrae are superimposed and perpendicular to the image receptor to minimize rotation.
• The nose should be in line with the base of the tail with the limbs positioned evenly.
• If there is an interest in the occipital bone, point the nose upward and secure with sandbags lateral to the head and neck so that there is no bone superimposition of C1 to C2 with the occipital bone.
• As this is often the last view made, the endotracheal tube may need to be removed before the image is taken to avoid artifacts that might interfere with diagnosis.
• An open-mouth view of the odontoid process can be made as described in Chapter 21.

Examples

MEASURE: Level of C6 near the manubrium.

CENTRAL RAY: C3 to C4.

BORDERS: Base of the skull to just past the shoulder joint to about T2, with tight collimation laterally.

Hyperextended Lateral View of the Cervical Vertebrae—Ancillary

Positioning

Place In: Lateral recumbency.
Hind Limbs: Superimpose and place the pelvic limbs caudally; secure with a sandbag.
Forelimbs: Position and superimpose the forelimbs caudally; secure with a sandbag. A small foam pad may be placed between the limbs.
Head/Neck/Sternum: Elevate and keep the nose level to the table, using a foam pad. To see if the head is in a true lateral, draw an imaginary line between the medial canthi, and make sure this line is perpendicular to the table. Hyperextend the neck and head dorsally and caudally until resistance is met. Support the cranial area of the head with a sandbag, or secure with tape/Velcro strapping. Place foam pads under the sternum to achieve true alignment with the vertebrae.
Vertebrae: Use a foam pad or cotton beneath the cervical vertebrae as needed to keep each vertebra parallel to the table.

Comments and Tips

• For true hyperextension, all cervical vertebrae need to be extended dorsally.
• As with other cervical laterals, the head must be in a true lateral position; keep true lateral positioning of the entire body using proper padding, and do not overextend the limbs.
• Collimate tightly so that a coned-down view is obtained.
• If an endotracheal tube is present, be careful that the patient's breathing is not restricted at any point.
• The hyperextended view is usually completed before the flexion to determine if the latter is required.
• The hyperextended and hyperflexed views are referred to as dynamic views and are usually completed after myelography to note any spinal cord impingement due to extradural changes associated with vertebral instability.² Be very cautious with the procedures to prevent further injury.

Examples

MEASURE: C3 to C4 intervertebral space across the neck.

CENTRAL RAY: C3 to C4 intervertebral space.

BORDERS: Base of the skull to the spine of the scapula (just past the shoulder joint). Collimate tightly to the edge of the wings of the atlas and the center of the spine of the scapula.

Flexed Lateral View of the Cervical Vertebrae—Ancillary

Positioning

Place In: Lateral recumbency.
Hind Limbs: Superimpose and position the pelvic limbs caudally; secure with sandbags.
Forelimbs: Position and superimpose the forelimbs ventrally and caudally, and secure with a sandbag. A small foam pad can be placed between the limbs.
Head/Neck/Sternum: Place tape or thin rope around the nose or canine teeth, and gently apply traction on the end so the neck and head are flexed. Pull the tape caudally between the forelimbs close to the body, and secure to a sandbag. If needed, elevate the nose using a sponge so the head is in true lateral. Draw an imaginary line between the medial canthi, and make sure this line is perpendicular to the table. A sandbag can be placed dorsal to the nose to maintain the hyperflexed position. Place sponges under the sternum to achieve true alignment with the vertebrae.
Vertebrae: If needed, use sponges beneath the cervical vertebrae to keep the spine parallel to the table and at the same plane as the thoracic vertebrae.

Comments and Tips

• For true flexion, all cervical vertebrae need to be flexed.
• As with other cervical laterals, the head must be in a true lateral position; keep true lateral positioning of the entire body using proper padding, and do not overextend the limbs.
• The flexed lateral dynamic view is generally used to assess small-breed dogs with suspected subluxation.²
• Begin with the mildest extension that will demonstrate instability, as marked flexion may further damage the spinal cord.
• Collimate tightly so that a coned-down view is obtained for less distortion and better contrast.
• The radiographs should only be taken with the patient under general anesthesia and placement of an endotracheal tube. Be careful with hyperflexing the neck so as not to cause tracheal trauma or constriction of the endotracheal tube.

Examples

MEASURE: C3 to C4 intervertebral space across the neck.

CENTRAL RAY: C3 to C4 intervertebral space.

BORDERS: Base of the skull to the spine of the scapula (just past the shoulder joint). Collimate tightly to the edge of the wings of the atlas and the center of the scapular spine.

Lateral Oblique View for the Odontoid Process—Ancillary

Positioning

Place In: Lateral recumbency.
Hind Limbs: Superimpose and place the pelvic limbs caudally; secure with a sandbag.
Forelimbs: Position and superimpose the forelimbs caudally; secure with a sandbag. A small foam pad can be placed between the limbs.
Head/Neck/Sternum: Use tape/Velcro strapping to keep the head in its natural oblique position.⁶ Place sponges under the sternum so it is on the same plane as the thoracic vertebrae.
Vertebrae: Use padding to keep the cervical vertebrae lateral and the head and C1 oblique.

Comments and Tips

• Position the ear pinnae laterally, and pull the tongue to avoid shadows on the radiograph.
• Lateral oblique views of C1 to C2 are used to demonstrate the dens.

Examples

MEASURE: C1 (for odontoid process).

CENTRAL RAY: C1 (for odontoid process).

BORDERS: Midskull to C4.

Thoracic Vertebrae

Lateral View of the Thoracic Vertebrae—Routine

Positioning

FIG. 20.9 A, Left lateral views of the sixth thoracic vertebra. B, Twelfth and thirteenth thoracic vertebrae.

Place In: Lateral recumbency with pelvis moved ventrally to straighten the thoracic spine.
Hind Limbs: Superimpose and place the pelvic limbs caudally; secure with a sandbag. A small foam pad can be placed between the limbs.
Forelimbs: Superimpose and cranially position the forelimbs slightly; secure with a sandbag. A small foam pad can be placed between the limbs.
Head/Neck/Sternum: Keep the head in a natural position, and support the neck with a sandbag. If needed, use sponges under the sternum and between the limbs to achieve true alignment of the sternum and vertebrae.
Vertebrae: Use padding if needed to keep each thoracic vertebra on the same horizontal plane as the sternum. Using tape as in Fig. 20.1 can assist with proper alignment.

Comments and Tips

• Try to keep lateral positioning of the entire body even if radiographing only the thoracic area.
• Collimate tightly laterally.
• The pelvis should be positioned ventrally so that the thoracic vertebrae are aligned with the long axis of the image receptor. In the mid-to-caudal thoracic vertebrae region, dogs and cats have a natural area of kyphosis.¹
• The ribs should be superimposed over each other so that the intervertebral spaces are better viewed, and the sternum should be on the same plane as the vertebrae. Use foam pads appropriately.
• Large dogs may require two separate views.
• Placing a lead mask or saline bag dorsal to the thoracic spine helps prevent scattered/secondary radiation from darkening the spinous processes in large dogs.

Examples

MEASURE: Highest point of the midthorax.

CENTRAL RAY: T6 to T7 or the caudal border of the scapula.

BORDERS: From C7 to L1 inclusive (shoulder joint to past the origin of the last rib).

Technician Notes

Placing padding under the nose and the natural curvatures of the spine (neck and lumbar regions) and between the limbs for all lateral positions will keep the spine parallel and horizontal with the table/image receptor and perpendicular to the center ray.

Keep a true lateral position of the entire body for each view, and keep the sternum and vertebrae on the same plane, parallel to the table and perpendicular to the x-y beam and receptor.

Ventrodorsal View of the Thoracic Vertebrae—Routine

Positioning

Place In: Dorsal recumbency in a V-trough or use sandbags, if needed, to prevent rotation.
Hind Limbs: Equally place the pelvic limbs in a neutral position; secure with sandbags.
Forelimbs: Equally position the forelimbs cranially and tie or secure with sandbags.
Head/Neck/Sternum: The head and neck are best positioned with the nose parallel to the table and equidistant between the limbs. Support with ties or a sandbag, being careful not to restrict breathing.
Vertebrae: Superimpose the sternum and vertebrae to minimize any rotation.

Comments and Tips

• Ensure that there is a straight line from the tip of the nose to the base of the tail to achieve rib symmetry on the image.
• Large dogs may require two separate views.
• The symmetry of the normal patient is noted on an image when the spinous processes are evident on the midvertebral body and the sternum is superimposed over the vertebrae.

Examples

MEASURE: T6 to T7 or the caudal border of the scapula.

CENTRAL RAY: T6 to T7 or the caudal border of the scapula.

BORDERS: C7 to L1 (shoulder joint to past the origin of the last rib).

Technician Notes

Image fewer vertebrae to prevent distortion due to the divergence of the x-ray beam.

Thoracolumbar Vertebrae

Lateral View of the Thoracolumbar Vertebrae—Routine

Positioning

Place In: Lateral recumbency.
Hind Limbs: Superimpose and place the pelvic limbs caudally; secure with a sandbag.
A small foam pad can be placed between the limbs.
Forelimbs: Superimpose and cranially position the forelimbs slightly; secure with a sandbag. A small foam pad can be placed between the limbs.
Head/Neck/Sternum: If needed, use foam pads under the sternum to achieve true alignment with the vertebrae. Keep the head in a natural position and support the neck with a sandbag, being careful not to restrict breathing.
Vertebrae: Keep the thoracolumbar vertebrae on the same plane as the sternum. Using tape as in Fig. 20.1 can assist with proper alignment.

Comments and Tips

• Try to maintain true lateral positioning of the entire body even if radiographing only the thoracolumbar area.
• Collimate tightly. The vertebrae should be limited to four on either side of the thoracolumbar junction. If interested in both the thoracic and lumbar vertebrae, each area should be radiographed separately so that the number of vertebrae are limited.
• The ribs should be superimposed over each other so that the intervertebral spaces are better viewed, and the sternum should be at the same distance from the table as the vertebrae.
• On the image the intervertebral foramina should be superimposed, and they should be of equal sizes from the thoracolumbar junction toward the sacrum.

Examples

MEASURE: Highest point of the ribs.

CENTRAL RAY: T13 to L1 intervertebral space.

BORDERS: Xiphoid to most caudal portion of the last rib.

Technician Notes

Keep these practical landmarks in mind as a general basis for the borders of all vertebrae:

• Base of the skull
• Shoulder
• Origin of the last rib
• Greater trochanter

Ventrodorsal View of the Thoracolumbar Vertebrae—Routine

Positioning

Place In: Dorsal recumbency in a V-trough or use sandbags, if needed, to prevent rotation.
Hind Limbs: Place the pelvic limbs in a neutral position; secure with sandbags if needed.
Forelimbs: Position the forelimbs cranially; tie or secure with sandbags.
Head/Neck/Sternum: The head and neck can be in a natural position. If needed, support with a sandbag, being careful not to restrict breathing. The nose should be equidistant between both front limbs.
Vertebrae: Have the sternum and vertebrae superimposed to minimize any rotation.

Comments and Tips

• Ensure that there is a straight line from the tip of the nose to the base of the tail.
• Collimate tightly. If interested in both the thoracic and lumbar vertebrae, each area should be radiographed separately so that the number of vertebrae are limited. See Box 20.1 to ensure you have proper symmetry on the image.
Box 20.1
Assessing Correct Positioning on a Vertebral Image
To assess correct positioning on a finished image.¹^-³

Examples

MEASURE: Highest point of the midthorax.

CENTRAL RAY: T13 to L1 intervertebral space.

BORDERS: Xiphoid to the caudal portion of last rib (about T10–L3).

Technician Notes

Provide enough support with a V- trough, foam pads, or sandbags to prevent any axial rotation. The spine and sternum must be superimposed perpendicular to the table and plate for the ventrodorsal view; and on the same horizontal plane, parallel to the table and plate, for the lateral views.

Technician Notes

Collimate tightly to include the transverse process and muscle mass, but do not include the fat and skin.

Lumbar Vertebrae

Lateral View of the Lumbar Vertebrae—Routine

Positioning

Place In: Lateral recumbency.
Hind Limbs: Superimpose and place the pelvic limbs slightly caudally; secure with a sandbag. A small foam pad can be placed between the limbs.
Forelimbs: Superimpose and position the forelimbs slightly cranially; secure with a sandbag. A small foam pad can be placed between the limbs.
Head/Neck/Sternum: If needed, use foam pads under the sternum to achieve true alignment with the vertebrae. Keep the head in a natural position; support the neck with a sandbag, being careful not to restrict breathing.
Vertebrae: Keep each lumbar vertebra parallel to the table and image receptor and on the same horizontal plane as the sternum. Using tape as in Fig. 20.1 can assist with proper alignment.

Comments and Tips

• Try to maintain true lateral positioning of the entire body even if radiographing only the lumbar area.
• Collimate tightly.
• See Box 20.1 to ensure you have proper symmetry on the image.

Examples

MEASURE: Level of L1.

CENTRAL RAY: L3 to L4 (palpate).

BORDERS: T12 to S1 (Just cranial to origin of last rib to just before the greater trochanter).

Ventrodorsal View of the Lumbar Vertebrae—Routine

Positioning

Place In: Dorsal recumbency in a V-trough or use sandbags, if needed, to prevent rotation.
Hind Limbs: Place the pelvic limbs in a neutral position; secure with sandbags if needed.
Forelimbs: Position the forelimbs cranially and secure with a sandbag if needed.
Head/Neck/Sternum: The head can be in a natural position.
Support with a sandbag, being careful not to restrict breathing.
Position the nose equidistant between the forelimbs.
Vertebrae: Superimpose the sternum and vertebrae to prevent any rotation.

Comments and Tips

• Ensure that there is a straight line from the tip of the nose to the base of the tail.
• The transverse processes should be present and symmetrical on the image.
• Enemas are suggested before radiography of the lumbar and lumbosacral spine because feces can create artifacts.

Examples

MEASURE: Level of L1.

CENTRAL RAY: Level of L4 (palpate).

BORDERS: T12 to S1 (Just cranial to both the origin of the last rib and acetabulum).

Technician Notes

Extending the forelimbs and hind limbs and securing them provide further support to help avoid rotation of the spine in the VD position.

FIG. 20.15 A, Fourth lumbar vertebra left lateral view. B, Fifth lumbar vertebrae, caudolateral view. (From Evans H, de Lahunta A. Guide to the Dissection of the Dog, 8th ed. St Louis: Saunders; 2017.)

FIG. 20.16 Sacrum. A, Ventral view. B, Left lateral view. (From Evans H, de Lahunta A. Guide to the Dissection of the Dog, 8th ed. St Louis: Saunders; 2017.)

FIG. 20.17 A, Third caudal vertebrae, dorsal view. B, Fourth caudal vertebrae, cranial view. C, Sixth caudal vertebra, dorsal (left) and lateral (right) views. (From Evans H, de Lahunta A. Guide to the Dissection of the Dog, 8th ed. St Louis: Saunders; 2017.)

Lumbosacral Vertebrae

Lateral View of the Lumbosacral Vertebrae—Natural Positioning—Routine

Positioning

Place In: Lateral recumbency.
Hind Limbs: Superimpose and position the pelvic limbs slightly caudally, with a foam pad between them; secure with sandbags. Ensure that the wings of the ilia are superimposed and parallel to the image receptor by placing padding under the upper limb.
Forelimbs: Superimpose and cranially position the forelimbs slightly; secure with a sandbag. A small foam pad can be placed between the limbs.
Head/Neck/Sternum: Use foam pads under the sternum to achieve true alignment with the vertebrae. Keep the head in a natural position; support the neck with a sandbag, being careful not to restrict breathing.
Vertebrae: Use padding to keep each lumbar vertebra parallel to the table and the image receptor.

Comments and Tips

• Use the pelvis technique chart to ensure adequate penetration.
• See Box 20.1 to ensure you have proper symmetry on the image.
• Ancillary views of the lumbosacral include hyperextended and hyperflexed views of the vertebrae.

Examples

MEASURE: Level of the lumbosacral junction or the highest point of the wings of the ilia.

CENTRAL RAY: Level of the lumbosacral junction (just caudal to the wings of the ilia).

BORDERS: L4 to the most cranial caudal vertebra (just cranial to the wings of the ilia to the femoral head).

Lateral View of the Lumbosacral Vertebrae—Ancillary

Comments and Tips

• These views are used to demonstrate lumbosacral instability.
• The measuring, centering, borders, and positioning is exactly the same as for the lateral view except for positioning of the hind limbs:
- • For the hyperextended view (Fig. 20.19A): hyperextend the superimposed hind limbs as far caudally as possible, placing a sandbag over them to hold in position.
  
  FIG. 20.19 A, Positioning for the lateral view of the lumbosacral vertebrae—hyperextended view. B, Positioning for the lateral view of the lumbosacral vertebrae—hyperflexed view.
- • For the hyperflexed view (Fig. 20.19B): position the superimposed hind limbs as far cranially as possible, placing a sandbag over them to hold in position.