Radiology of the vertebral column

Tobias Schwarz; Andrew Holloway

doi:10.22233/9781910443187.9

British Small Animal Veterinary Association , 355 (2013); https://doi.org/10.22233/9781910443187.9

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Radiology of the vertebral column

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Authors: Tobias Schwarz and Andrew Holloway
From: BSAVA Manual of Canine and Feline Radiography and Radiology
Item: Chapter 9, pp 355 - 386
DOI: 10.22233/9781910443187.9
Copyright: © 2013 British Small Animal Veterinary Association
Publication Date: January 2013

Abstract

Radiographic assessment of the vertebral column is usually perfomed to investigate suspected disorders of the vertebral column and paravertabral soft tissues. As the spinal cord and nerves are not visible on survey radiographs, diagnostic conclusions are mainly drawn indirectly from its casing, the vertebral column. Therefore, it is not surprising that survey spinal radiography has a poor diagnostic yield in animals with neurological disease. There are challenges associated with radiography of the vertebral column. For example localization, accurate neurolocalization is required and should precede radiography to ensure that the correct spinal cord segments are imaged and to rule out multifocal disease. Paired structures (articular processes, pedicles) are superimposed on lateral views, and cardiovascular structures and the bowel are superimposed on the vertebral column on ventrodorsal (VD) views, creating multiple composite shadows which can mimic pathology. There is poor contrast of the paraspinal soft tissues and the soft tissues within the vertebral canal. Also, radiography is relatively insensitive for demonstrating bone loss. Considerable bone loss (30-50%) is required before changes are recognized on radiographs.

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Figures

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9.1

(a) Patient positioning for a lateral view of the vertebral column. The vertebral column is positioned parallel to the X-ray table and perpendicular to the X-ray beam by supporting the mid-cervical and mid-lumbar vertebral column using radiolucent positioning aids. This prevents the vertebral column from sagging in the sagittal plane. Supporting the skull, sternum and limbs limits rotation in the transverse plane. (b) Positioning for a VD view. The caudal cervical vertebral column and thorax are supported to prevent rotation. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. © 2013 British Small Animal Veterinary Association

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9.1 (a) Patient positioning for a lateral view of the vertebral column. The vertebral column is positioned parallel to the X-ray table and perpendicular to the X-ray beam by supporting the mid-cervical and mid-lumbar vertebral column using radiolucent positioning aids. This prevents the vertebral column from sagging in the sagittal plane. Supporting the skull, sternum and limbs limits rotation in the transverse plane. (b) Positioning for a VD view. The caudal cervical vertebral column and thorax are supported to prevent rotation. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.

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9.2

Lateral cervical myelogram of a German Shepherd Dog. The dorsal and ventral opaque columns of contrast medium in the subarachnoid space outline the margins of the spinal cord. The subarachnoid space is attenuated at the C4–C5, C5–C6, C6–C7 and T1–T2 intervertebral disc spaces. There is mild narrowing of the spinal cord at T1–T2. (Courtesy of L Jarrett) © 2013 British Small Animal Veterinary Association

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9.2 Lateral cervical myelogram of a German Shepherd Dog. The dorsal and ventral opaque columns of contrast medium in the subarachnoid space outline the margins of the spinal cord. The subarachnoid space is attenuated at the C4–C5, C5–C6, C6–C7 and T1–T2 intervertebral disc spaces. There is mild narrowing of the spinal cord at T1–T2. (Courtesy of L Jarrett)

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9.3

Principles of myelographic interpretation. (a) Normal. (b) Ventral extradural compressive lesion (e.g. disc extrusion resulting in displacement or compression of the spinal cord on the lateral view and widening on the VD view). The subarachnoid space is narrowed on both views. (c) Intradural–extramedullary lesion (e.g. meningioma resulting in splitting of one of the contrast medium columns. This is best seen at the margins where pooling of contrast medium creates a ‘golf-tee’ sign). The cord is widened on the VD view. (d) Intramedullary lesion (e.g. spinal cord tumour). The spinal cord is widened and the subarachnoid space thinned on both views. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. © 2013 British Small Animal Veterinary Association

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9.3 Principles of myelographic interpretation. (a) Normal. (b) Ventral extradural compressive lesion (e.g. disc extrusion resulting in displacement or compression of the spinal cord on the lateral view and widening on the VD view). The subarachnoid space is narrowed on both views. (c) Intradural–extramedullary lesion (e.g. meningioma resulting in splitting of one of the contrast medium columns. This is best seen at the margins where pooling of contrast medium creates a ‘golf-tee’ sign). The cord is widened on the VD view. (d) Intramedullary lesion (e.g. spinal cord tumour). The spinal cord is widened and the subarachnoid space thinned on both views. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.

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9.4

Lateral view of the normal vertebral structures of the (a) cervical, (b) thoracic and (c) lumbar vertebral column. 1 = vertebral body; 2 = endplate; 3 = transverse process; 4 = cranial articular process; 5 = caudal articular process; 6 = spinous process; 7 = accessory process; 8 = pedicle; 9 = rib head; 10 = articular process joint; 11 = intervertebral disc; 12 = intervertebral foramen; 13 = mammilary process. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. © 2013 British Small Animal Veterinary Association

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9.4 Lateral view of the normal vertebral structures of the (a) cervical, (b) thoracic and (c) lumbar vertebral column. 1 = vertebral body; 2 = endplate; 3 = transverse process; 4 = cranial articular process; 5 = caudal articular process; 6 = spinous process; 7 = accessory process; 8 = pedicle; 9 = rib head; 10 = articular process joint; 11 = intervertebral disc; 12 = intervertebral foramen; 13 = mammilary process. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.

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9.5

Lateral radiographs of the vertebral column of a skeletally mature dog. (a) Cervical vertebral column. The C4–C6 vertebrae have large, ventrolaterally oriented, transverse processes (arrowheads). Note that the C2–C3 and C7–T1 intervertebral disc spaces are normally narrower than C4–C6. (b) Caudal cervical and cranial thoracic vertebral column. Superimposition of the head of the first rib on the C7–T1 intervertebral disc space may mimic intervertebral disc mineralization (arrowed). (c) Caudal thoracic and cranial lumbar vertebral column. The diaphragmatic (T10) vertebra has dorsally oriented cranial (arrowhead) and sagittally oriented caudal (arrowed) articular process joints. The T13 and L1 vertebrae are fused (block vertebra). (d) Lumbar vertebral column. Note the typical ‘horsehead’ shape of the intervertebral foramina (*) and articular process joint spaces (double arrow). The gradual narrowing of the caudal lumbar intervertebral disc spaces is due to geometric distortion. The ventral margin of L4 is indistinct due to hypaxial muscle attachments (arrowhead). (e) Lumbosacral vertebral column. Note that the larger, triangular, intervertebral disc space and indistinct articular joint space of L7–S1 (*) are normal features. © 2013 British Small Animal Veterinary Association

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9.5 Lateral radiographs of the vertebral column of a skeletally mature dog. (a) Cervical vertebral column. The C4–C6 vertebrae have large, ventrolaterally oriented, transverse processes (arrowheads). Note that the C2–C3 and C7–T1 intervertebral disc spaces are normally narrower than C4–C6. (b) Caudal cervical and cranial thoracic vertebral column. Superimposition of the head of the first rib on the C7–T1 intervertebral disc space may mimic intervertebral disc mineralization (arrowed). (c) Caudal thoracic and cranial lumbar vertebral column. The diaphragmatic (T10) vertebra has dorsally oriented cranial (arrowhead) and sagittally oriented caudal (arrowed) articular process joints. The T13 and L1 vertebrae are fused (block vertebra). (d) Lumbar vertebral column. Note the typical ‘horsehead’ shape of the intervertebral foramina (*) and articular process joint spaces (double arrow). The gradual narrowing of the caudal lumbar intervertebral disc spaces is due to geometric distortion. The ventral margin of L4 is indistinct due to hypaxial muscle attachments (arrowhead). (e) Lumbosacral vertebral column. Note that the larger, triangular, intervertebral disc space and indistinct articular joint space of L7–S1 (*) are normal features.

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9.6

Lateral radiograph of the normal lumbar vertebral column in a cat. Note that the vertebral bodies of the lumbar vertebrae are elongated (arrowed) and that the forward projecting transverse processes have an elongated appearance (arrowhead). © 2013 British Small Animal Veterinary Association

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9.6 Lateral radiograph of the normal lumbar vertebral column in a cat. Note that the vertebral bodies of the lumbar vertebrae are elongated (arrowed) and that the forward projecting transverse processes have an elongated appearance (arrowhead).

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9.7

Lateral radiograph of the thoracolumbar vertebral column in a dog. The superimposition of the intervertebral foramina creates the typical ‘horsehead’ shape. The L1–L2 intervertebral disc space is most central on this view and thus appears largest. Towards the left of the image, the T12–T13 and T13–L1 intervertebral disc spaces appear gradually narrower, making assessment of the disc space width difficult. There is also faint mineralization of the nucleus pulposus at T11–T12 and L2–L3 (arrowheads). © 2013 British Small Animal Veterinary Association

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9.7 Lateral radiograph of the thoracolumbar vertebral column in a dog. The superimposition of the intervertebral foramina creates the typical ‘horsehead’ shape. The L1–L2 intervertebral disc space is most central on this view and thus appears largest. Towards the left of the image, the T12–T13 and T13–L1 intervertebral disc spaces appear gradually narrower, making assessment of the disc space width difficult. There is also faint mineralization of the nucleus pulposus at T11–T12 and L2–L3 (arrowheads).

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9.8

Röntgen signs: location and alignment. Lateral radiograph showing fused C2 and C3 block vertebrae in a cat. The odontoid process is enlarged, misshapen and oriented too dorsally (*). The height of the vertebral canal at the level of the dens within C1 is considerably narrower than within C2 (double-headed arrows). These changes are likely to be clinically significant. Note the vestigial or narrowed intervertebral disc space between C2 and C3, and the change in shape of the cranial aspect of the C4 vertebral body to accommodate the angulation of the caudal endplate of the C2–C3 block vertebra. The diameter of the vertebral canal at C3–C4 is similar to that at C4–C5. © 2013 British Small Animal Veterinary Association

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9.8 Röntgen signs: location and alignment. Lateral radiograph showing fused C2 and C3 block vertebrae in a cat. The odontoid process is enlarged, misshapen and oriented too dorsally (*). The height of the vertebral canal at the level of the dens within C1 is considerably narrower than within C2 (double-headed arrows). These changes are likely to be clinically significant. Note the vestigial or narrowed intervertebral disc space between C2 and C3, and the change in shape of the cranial aspect of the C4 vertebral body to accommodate the angulation of the caudal endplate of the C2–C3 block vertebra. The diameter of the vertebral canal at C3–C4 is similar to that at C4–C5.

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9.9

Röntgen sign: size. The vertebral canal within the L5 vertebral body is widened (double-headed arrow). The dorsal and ventral margins are expanded outwards and thinned. This represents a form of bone atrophy and remodelling typical of a slowly expanding mass. Final diagnosis: meningioma. © 2013 British Small Animal Veterinary Association

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9.9 Röntgen sign: size. The vertebral canal within the L5 vertebral body is widened (double-headed arrow). The dorsal and ventral margins are expanded outwards and thinned. This represents a form of bone atrophy and remodelling typical of a slowly expanding mass. Final diagnosis: meningioma.

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9.10

Röntgen sign: size. Shortened vertebra. (a–b) Lateral radiographs of the cranial thoracic spine of a dog with multiple myeloma. (a) The T3 vertebra is osteolytic and shortened (double-headed arrow) due to a compression fracture. There is an irregular periosteal reaction, suggesting that weakening of the vertebra was gradual, stimulating bone reaction. (b) At a later stage in the disease course, T3 has completely collapsed (double-headed arrow). Additional lesions and pathological fractures of the spinous processes are also present (*). (c) Lateral radiograph of a dog with a traumatic L3 compression fracture. The L3 vertebra is shortened (double-headed arrow), sclerotic caudally (arrowheads) and the L3–L4 intervertebral disc space (*) is reduced in size, consistent with a compression fracture and disc extrusion. © 2013 British Small Animal Veterinary Association

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9.10 Röntgen sign: size. Shortened vertebra. (a–b) Lateral radiographs of the cranial thoracic spine of a dog with multiple myeloma. (a) The T3 vertebra is osteolytic and shortened (double-headed arrow) due to a compression fracture. There is an irregular periosteal reaction, suggesting that weakening of the vertebra was gradual, stimulating bone reaction. (b) At a later stage in the disease course, T3 has completely collapsed (double-headed arrow). Additional lesions and pathological fractures of the spinous processes are also present (*). (c) Lateral radiograph of a dog with a traumatic L3 compression fracture. The L3 vertebra is shortened (double-headed arrow), sclerotic caudally (arrowheads) and the L3–L4 intervertebral disc space (*) is reduced in size, consistent with a compression fracture and disc extrusion.

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9.11

Röntgen sign: size. (a) Lateral view of the lumbar vertebral column of a 7-month-old dog with congenital hypothyroidism. Closure of the physes is delayed and the physes remain widened (arrowed). The vertebrae are reduced in length but the bone density is normal. (b) Lateral view of the thoracic vertebrae of a skeletally mature dog with congenital hypothyroidism, leading to epiphyseal dysplasia. The vertebrae are square and have irregular endplates. © 2013 British Small Animal Veterinary Association

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9.11 Röntgen sign: size. (a) Lateral view of the lumbar vertebral column of a 7-month-old dog with congenital hypothyroidism. Closure of the physes is delayed and the physes remain widened (arrowed). The vertebrae are reduced in length but the bone density is normal. (b) Lateral view of the thoracic vertebrae of a skeletally mature dog with congenital hypothyroidism, leading to epiphyseal dysplasia. The vertebrae are square and have irregular endplates.

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9.12

Röntgen sign: shape. Malformation of the occipitoatlantal articulation in a cat. (a) On the lateral view, the occipital condyles appear hypoplastic (arrowed). The anatomy of the atlas is generally normal except for a subtle change in the shape of the articular margin cranially. (b) On the VD view, the right occipital condyle is recognized to be normal in shape and size (arrowhead), whereas the left condyle is hypoplastic and flattened (arrowed) with adaptive remodelling of the cranial articular surface of the atlas. © 2013 British Small Animal Veterinary Association

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9.12 Röntgen sign: shape. Malformation of the occipitoatlantal articulation in a cat. (a) On the lateral view, the occipital condyles appear hypoplastic (arrowed). The anatomy of the atlas is generally normal except for a subtle change in the shape of the articular margin cranially. (b) On the VD view, the right occipital condyle is recognized to be normal in shape and size (arrowhead), whereas the left condyle is hypoplastic and flattened (arrowed) with adaptive remodelling of the cranial articular surface of the atlas.

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9.13

Röntgen sign: shape. Lateral radiograph of a dog with well demarcated osteolysis of the spinous process (*) and cranial articular processes of L2 (double-headed arrow), leading to an enlarged and abnormally shaped intervertebral foramen (arrowheads). The main differential diagnosis for this lesion would be a neoplastic process arising from the bone or paravertebral soft tissues. © 2013 British Small Animal Veterinary Association

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9.13 Röntgen sign: shape. Lateral radiograph of a dog with well demarcated osteolysis of the spinous process (*) and cranial articular processes of L2 (double-headed arrow), leading to an enlarged and abnormally shaped intervertebral foramen (arrowheads). The main differential diagnosis for this lesion would be a neoplastic process arising from the bone or paravertebral soft tissues.

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9.14

Röntgen sign: shape. Lateral radiograph of the thoracic vertebral column of a cat. Ventral bone spurs incompletely bridge several intervertebral disc spaces consistent with incidental spondylosis deformans. The intervertebral disc spaces are unequal in width, wedge-shaped with endplate sclerosis, with mineralization of the nuclei in some cases, indicative of intervertebral disc degeneration. Intervertebral disc disease in the cat is less common than in the dog. Where clinically significant, disease is usually chronic and progressive rather than due to acute extrusion. Radiographic changes such as these are of limited clinical significance. © 2013 British Small Animal Veterinary Association

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9.14 Röntgen sign: shape. Lateral radiograph of the thoracic vertebral column of a cat. Ventral bone spurs incompletely bridge several intervertebral disc spaces consistent with incidental spondylosis deformans. The intervertebral disc spaces are unequal in width, wedge-shaped with endplate sclerosis, with mineralization of the nuclei in some cases, indicative of intervertebral disc degeneration. Intervertebral disc disease in the cat is less common than in the dog. Where clinically significant, disease is usually chronic and progressive rather than due to acute extrusion. Radiographic changes such as these are of limited clinical significance.

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9.15

Röntgen sign: number. Lateral and VD views of the lumbosacral vertebral column of a dog with multiple myeloma. (a) Poorly circumscribed lysis of the L5 and L6 vertebral bodies is present (black arrows). The trabecular pattern is indistinct. An indistinct periosteal reaction borders the ventral margin of the L5 vertebral body. (b) The extent of the lysis of L5 (black arrow) and L6 (white arrows) is more evident on the VD view. Differentiating between monostotic and polyostotic lesions is an important feature to consider when evaluating radiographs of the vertebral column. © 2013 British Small Animal Veterinary Association

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9.15 Röntgen sign: number. Lateral and VD views of the lumbosacral vertebral column of a dog with multiple myeloma. (a) Poorly circumscribed lysis of the L5 and L6 vertebral bodies is present (black arrows). The trabecular pattern is indistinct. An indistinct periosteal reaction borders the ventral margin of the L5 vertebral body. (b) The extent of the lysis of L5 (black arrow) and L6 (white arrows) is more evident on the VD view. Differentiating between monostotic and polyostotic lesions is an important feature to consider when evaluating radiographs of the vertebral column.

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9.16

Röntgen sign: opacity. Osteopenia. Whole body radiograph of a 5-month-old cat with nutritional secondary hyperparathyroidism. There is marked generalized osteopenia, rendering the vertebral column poorly visible. Thoracic vertebral compression fractures have resulted in kyphosis (arrowed). There is caudal lumbar lordosis (white arrowhead) and the cortices of the femurs are thinned (black arrowheads). © 2013 British Small Animal Veterinary Association

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9.16 Röntgen sign: opacity. Osteopenia. Whole body radiograph of a 5-month-old cat with nutritional secondary hyperparathyroidism. There is marked generalized osteopenia, rendering the vertebral column poorly visible. Thoracic vertebral compression fractures have resulted in kyphosis (arrowed). There is caudal lumbar lordosis (white arrowhead) and the cortices of the femurs are thinned (black arrowheads).

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9.17

Röntgen sign: opacity. Osteopenia. Cervical vertebral column of a cat with hypervitaminosis A. There is a diffuse, smooth periosteal reaction bridging the dorsal aspect of the cervical vertebrae (arrowheads). There is also mild osteopenia of the vertebral bodies. © 2013 British Small Animal Veterinary Association

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9.17 Röntgen sign: opacity. Osteopenia. Cervical vertebral column of a cat with hypervitaminosis A. There is a diffuse, smooth periosteal reaction bridging the dorsal aspect of the cervical vertebrae (arrowheads). There is also mild osteopenia of the vertebral bodies.

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9.18

Röntgen sign: opacity. Osteopenia. Thoracic vertebral column of a dog with chronic hyperadrenocorticism. There is generalized osteopenia, making the vertebrae poorly distinct. The vertebral cortical margins stand out compared with the more demineralized medulla. Obesity also contributes to the low contrast in the image. © 2013 British Small Animal Veterinary Association

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9.18 Röntgen sign: opacity. Osteopenia. Thoracic vertebral column of a dog with chronic hyperadrenocorticism. There is generalized osteopenia, making the vertebrae poorly distinct. The vertebral cortical margins stand out compared with the more demineralized medulla. Obesity also contributes to the low contrast in the image.

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9.19

Röntgen sign: opacity. Osteolysis. Lateral radiograph of the thorax of a dog with neck pain. The purpose of radiography was to assess for pulmonary metastases. Note that an extensive lytic lesion has resulted in destruction of most of the spinous process and dorsal lamina of the second thoracic vertebra (arrowed). These changes are easily overlooked due to superimposition of the scapulae and emphasize the need to evaluate all parts of the image and the importance of not suspending the evaluation of the film when a conspicuous lesion, in this case multiple pulmonary metastases, is present. © 2013 British Small Animal Veterinary Association

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9.19 Röntgen sign: opacity. Osteolysis. Lateral radiograph of the thorax of a dog with neck pain. The purpose of radiography was to assess for pulmonary metastases. Note that an extensive lytic lesion has resulted in destruction of most of the spinous process and dorsal lamina of the second thoracic vertebra (arrowed). These changes are easily overlooked due to superimposition of the scapulae and emphasize the need to evaluate all parts of the image and the importance of not suspending the evaluation of the film when a conspicuous lesion, in this case multiple pulmonary metastases, is present.

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9.20

Röntgen sign: opacity. Osteosclerosis. (a) Lateral and (b) VD radiographs of the thoracolumbar vertebral column of a young dog with paraparesis. There is extensive remodelling associated with the L2–L3 vertebrae (white arrow). The intervertebral disc space is narrowed with marked sclerosis of the endplates bordering the disc space. A cleft is present within the cranial endplate of the L3 vertebra. The articular processes (arrowhead) appear irregular on the lateral view, but on the VD view they are normal in size. The intervertebral foramen is narrowed (black arrow). These changes are probably the consequence of trauma considering the collapsed disc space and the normal size of the vertebrae. Regardless of the cause, the changes indicate vertebral instability and adaptive changes to cope with the increased load. On MRI, the spinal cord was shown to be compressed by marked proliferation of protruding dorsal annulus. © 2013 British Small Animal Veterinary Association

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9.20 Röntgen sign: opacity. Osteosclerosis. (a) Lateral and (b) VD radiographs of the thoracolumbar vertebral column of a young dog with paraparesis. There is extensive remodelling associated with the L2–L3 vertebrae (white arrow). The intervertebral disc space is narrowed with marked sclerosis of the endplates bordering the disc space. A cleft is present within the cranial endplate of the L3 vertebra. The articular processes (arrowhead) appear irregular on the lateral view, but on the VD view they are normal in size. The intervertebral foramen is narrowed (black arrow). These changes are probably the consequence of trauma considering the collapsed disc space and the normal size of the vertebrae. Regardless of the cause, the changes indicate vertebral instability and adaptive changes to cope with the increased load. On MRI, the spinal cord was shown to be compressed by marked proliferation of protruding dorsal annulus.

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9.21

Röntgen sign: opacity. Osteoproliferation. (a) Lateral radiograph of the lumbar vertebral column of a dog with back pain due to vertebral osteomyelitis. A thick, smooth, periosteal reaction extends from the ventral border of the third lumbar vertebra (arrowed). The vertebral body overall is of increased opacity compared to adjacent vertebral bodies, due to the superimposition of florid, lateralized periosteal new bone. The changes were confirmed on MRI. Only a single vertebra was involved. (b) Lateral radiograph of the lumbar vertebral column of a dog with primary neoplasia of the L4 vertebra. The changes are predominantly productive involving the dorsal lamina of the vertebra. The location of the lesion and the amorphous new bone are indicative of a neoplastic process. © 2013 British Small Animal Veterinary Association

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9.21 Röntgen sign: opacity. Osteoproliferation. (a) Lateral radiograph of the lumbar vertebral column of a dog with back pain due to vertebral osteomyelitis. A thick, smooth, periosteal reaction extends from the ventral border of the third lumbar vertebra (arrowed). The vertebral body overall is of increased opacity compared to adjacent vertebral bodies, due to the superimposition of florid, lateralized periosteal new bone. The changes were confirmed on MRI. Only a single vertebra was involved. (b) Lateral radiograph of the lumbar vertebral column of a dog with primary neoplasia of the L4 vertebra. The changes are predominantly productive involving the dorsal lamina of the vertebra. The location of the lesion and the amorphous new bone are indicative of a neoplastic process.

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9.22

Röntgen sign: opacity. Remodelling. Lateral view of the lumbosacral vertebral column of a dog with remodelling changes following a displaced L7 fracture. The changes are chronic. The caudal aspect of the L7 vertebra is displaced ventrally. The displaced fragment has fused with the ventral aspect of the L6 vertebral body and the cranial aspect of the non-displaced L7 fragment (malunion). The intervertebral disc between L6 and L7 is still recognizable (black arrow). There is extensive remodelling and ventral spondylosis. The vertebral canal at the lumbosacral junction is irregularly widened. The changes associated with the L4–L5 vertebrae probably represent a congenital block vertebra rather than the result of trauma as the L4 vertebral body is shortened and the articular process joints are absent (white arrow). © 2013 British Small Animal Veterinary Association

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9.22 Röntgen sign: opacity. Remodelling. Lateral view of the lumbosacral vertebral column of a dog with remodelling changes following a displaced L7 fracture. The changes are chronic. The caudal aspect of the L7 vertebra is displaced ventrally. The displaced fragment has fused with the ventral aspect of the L6 vertebral body and the cranial aspect of the non-displaced L7 fragment (malunion). The intervertebral disc between L6 and L7 is still recognizable (black arrow). There is extensive remodelling and ventral spondylosis. The vertebral canal at the lumbosacral junction is irregularly widened. The changes associated with the L4–L5 vertebrae probably represent a congenital block vertebra rather than the result of trauma as the L4 vertebral body is shortened and the articular process joints are absent (white arrow).

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9.23

Röntgen sign: opacity. Osteopetrosis. There is a generalized, increased medullary opacity of the skeleton in this cat with lymphoma. This is particularly visible in the vertebral bodies. © 2013 British Small Animal Veterinary Association

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9.23 Röntgen sign: opacity. Osteopetrosis. There is a generalized, increased medullary opacity of the skeleton in this cat with lymphoma. This is particularly visible in the vertebral bodies.

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9.24

Röntgen sign: opacity. Lateral radiograph showing intervertebral disc degeneration and herniation in a chondrodystrophic dog. The L1–L2 intervertebral disc space is narrowed with mineralized disc material superimposed on the intervertebral foraminal space (arrowhead). These changes are consistent with a Hansen type I degeneration and disc extrusion. This finding is not sufficient to determine whether surgical intervention is justified as this material is not necessarily the clinically relevant lesion. © 2013 British Small Animal Veterinary Association

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9.24 Röntgen sign: opacity. Lateral radiograph showing intervertebral disc degeneration and herniation in a chondrodystrophic dog. The L1–L2 intervertebral disc space is narrowed with mineralized disc material superimposed on the intervertebral foraminal space (arrowhead). These changes are consistent with a Hansen type I degeneration and disc extrusion. This finding is not sufficient to determine whether surgical intervention is justified as this material is not necessarily the clinically relevant lesion.

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9.25

Röntgen sign: opacity. Soft tissue mineralization. Lateral view of the lumbar vertebral column of a dog with ossification of the dura mater (dural ossification), outlining the spinal cord (automyelogram) (arrowheads). At L6–L7 mineralized disc material can be seen protruding into the vertebral canal and the dural sac is mildly deviated (arrowed). This does not provide sufficient information to determine whether a significant lesion is present. © 2013 British Small Animal Veterinary Association

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9.25 Röntgen sign: opacity. Soft tissue mineralization. Lateral view of the lumbar vertebral column of a dog with ossification of the dura mater (dural ossification), outlining the spinal cord (automyelogram) (arrowheads). At L6–L7 mineralized disc material can be seen protruding into the vertebral canal and the dural sac is mildly deviated (arrowed). This does not provide sufficient information to determine whether a significant lesion is present.

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9.26

Röntgen sign: margination. Lateral radiograph of the cranial cervical vertebral column of a small-breed dog with a depression fracture of C3 following a bite to the neck from a larger dog. A discrete defect (white arrow) is present in the dorsal lamina of C3. The small cortical fragment (black arrow) is displaced ventrally and superimposed on the vertebral canal. Inadvertent axial rotation may have allowed the defect in the margin of the vertebral canal to be better visualized. © 2013 British Small Animal Veterinary Association

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9.26 Röntgen sign: margination. Lateral radiograph of the cranial cervical vertebral column of a small-breed dog with a depression fracture of C3 following a bite to the neck from a larger dog. A discrete defect (white arrow) is present in the dorsal lamina of C3. The small cortical fragment (black arrow) is displaced ventrally and superimposed on the vertebral canal. Inadvertent axial rotation may have allowed the defect in the margin of the vertebral canal to be better visualized.

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9.27

(a) Lateral view of the vertebral column of a young cat with multiple congenital malformations. There is marked kyphosis (dorsal angulation) of the thoracic vertebral column (arrowed). Radiography provides a global assessment of the changes; however, it is impossible to assess the nature and extent of the malformations with certainty. Accurate neurolocalization and cross-sectional imaging are required to establish whether the changes are of clinical significance and confirm any sites of stenosis (on MRI in this cat there was severe cord compression at T3–T4). The lumbosacral changes were not clinically significant. (b) Magnified lateral and (c) VD views of the vertebral column of a young cat with multiple congenital malformations. (b) The magnified view demonstrates narrowing of the vertebral canal at the level of T3–T4 (small double-headed arrow) compared to adjacent segments (large double-headed arrows). (c) Scoliosis (lateral deviation to the left) of the lumbar vertebral column (white arrows) and a transitional lumbosacral vertebra (black arrow) are evident. The malformations within both vertebral segments include block vertebrae, hemivertebrae, incomplete separation of the dorsal laminae and spinous processes and transitional vertebrae. Radiography provides a global assessment of the changes; however, it is impossible to assess the nature and extent of the malformations with certainty. Accurate neurolocalization and cross-sectional imaging are required to establish whether the changes are of clinical significance and confirm any sites of stenosis (on MRI in this cat there was severe cord compression at T3–T4). The lumbosacral changes were not clinically significant. © 2013 British Small Animal Veterinary Association

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9.27 (a) Lateral view of the vertebral column of a young cat with multiple congenital malformations. There is marked kyphosis (dorsal angulation) of the thoracic vertebral column (arrowed). Radiography provides a global assessment of the changes; however, it is impossible to assess the nature and extent of the malformations with certainty. Accurate neurolocalization and cross-sectional imaging are required to establish whether the changes are of clinical significance and confirm any sites of stenosis (on MRI in this cat there was severe cord compression at T3–T4). The lumbosacral changes were not clinically significant. (b) Magnified lateral and (c) VD views of the vertebral column of a young cat with multiple congenital malformations. (b) The magnified view demonstrates narrowing of the vertebral canal at the level of T3–T4 (small double-headed arrow) compared to adjacent segments (large double-headed arrows). (c) Scoliosis (lateral deviation to the left) of the lumbar vertebral column (white arrows) and a transitional lumbosacral vertebra (black arrow) are evident. The malformations within both vertebral segments include block vertebrae, hemivertebrae, incomplete separation of the dorsal laminae and spinous processes and transitional vertebrae. Radiography provides a global assessment of the changes; however, it is impossible to assess the nature and extent of the malformations with certainty. Accurate neurolocalization and cross-sectional imaging are required to establish whether the changes are of clinical significance and confirm any sites of stenosis (on MRI in this cat there was severe cord compression at T3–T4). The lumbosacral changes were not clinically significant.

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9.28

Transitional vertebrae. (a) VD view of the lumbosacral joint of a 5-month-old German Shepherd Dog. The transitional lumbosacral vertebra has a normal transverse process on the left (*) and an abnormal broad transverse process fused with the sacral wing on the right (arrowhead). The spinous process (arrowed) of the transitional vertebra is split (spina bifida). (b) Lateral view of the thorax of a dog. The transitional vertebra is located at C7. Note the elongated (rib-like), ventrally oriented transverse processes (arrowed). © 2013 British Small Animal Veterinary Association

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9.28 Transitional vertebrae. (a) VD view of the lumbosacral joint of a 5-month-old German Shepherd Dog. The transitional lumbosacral vertebra has a normal transverse process on the left (*) and an abnormal broad transverse process fused with the sacral wing on the right (arrowhead). The spinous process (arrowed) of the transitional vertebra is split (spina bifida). (b) Lateral view of the thorax of a dog. The transitional vertebra is located at C7. Note the elongated (rib-like), ventrally oriented transverse processes (arrowed).

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9.29

Hemivertebra formation. Normal, paired mesodermal segments (N) merge and form a cartilaginous precursor of a vertebral body. If a mismatch in the fusion pattern occurs, unmatched segments (M) form wedge-shaped hemivertebrae (H), resulting in vertebral curvature deformities. © 2013 British Small Animal Veterinary Association

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9.29 Hemivertebra formation. Normal, paired mesodermal segments (N) merge and form a cartilaginous precursor of a vertebral body. If a mismatch in the fusion pattern occurs, unmatched segments (M) form wedge-shaped hemivertebrae (H), resulting in vertebral curvature deformities.

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9.30

VD radiograph of a Bulldog showing scoliosis (arrowheads) and abnormal spacing of the ribs due to the formation of a hemivertebra at T8. These deformities are ubiquitous in brachycephalic breeds and only rarely cause clinical signs. © 2013 British Small Animal Veterinary Association

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9.30 VD radiograph of a Bulldog showing scoliosis (arrowheads) and abnormal spacing of the ribs due to the formation of a hemivertebra at T8. These deformities are ubiquitous in brachycephalic breeds and only rarely cause clinical signs.

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9.31

(a) Lateral radiograph of a Boston Terrier with thoracic hemivertebrae. The vertebral bodies of T9 and T11 are narrowed ventrally (triangular-shaped), resulting in kyphosis. These changes were incidental. Note also the central endplate defects in T5 and T7, consistent with incidental Schmorl’s nodes. (b) Ventrodorsal radiograph of a brachycephalic dog with cleft or butterfly vertebrae at T8, T10 and T12. The bodies of these vertebrae are incompletely formed, giving them the shape of a butterfly. © 2013 British Small Animal Veterinary Association

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9.31 (a) Lateral radiograph of a Boston Terrier with thoracic hemivertebrae. The vertebral bodies of T9 and T11 are narrowed ventrally (triangular-shaped), resulting in kyphosis. These changes were incidental. Note also the central endplate defects in T5 and T7, consistent with incidental Schmorl’s nodes. (b) Ventrodorsal radiograph of a brachycephalic dog with cleft or butterfly vertebrae at T8, T10 and T12. The bodies of these vertebrae are incompletely formed, giving them the shape of a butterfly.

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9.32

(a) Lateral and (b) VD views of the lumbosacral vertebral column of a dog with spina bifida. (a) The spinous process is hypoplastic in L6 and absent in L7 (arrowed). (b) The wide pedicles and absence of lamina and spinous process of L7 are noted on the VD view (double-headed arrow). The small cleft in the caudal lamina of L6 indicates a partial fusion defect (black arrow). © 2013 British Small Animal Veterinary Association

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9.32 (a) Lateral and (b) VD views of the lumbosacral vertebral column of a dog with spina bifida. (a) The spinous process is hypoplastic in L6 and absent in L7 (arrowed). (b) The wide pedicles and absence of lamina and spinous process of L7 are noted on the VD view (double-headed arrow). The small cleft in the caudal lamina of L6 indicates a partial fusion defect (black arrow).

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9.33

Sacrococcygeal dysgenesis in a Miniature Pinscher. The caudal part of the sacrum (arrowhead) and connection to the coccygeal vertebrae (Cy) are absent. © 2013 British Small Animal Veterinary Association

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9.33 Sacrococcygeal dysgenesis in a Miniature Pinscher. The caudal part of the sacrum (arrowhead) and connection to the coccygeal vertebrae (Cy) are absent.

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9.34

Lateral radiograph of the caudal cervical vertebral column of a Toy Poodle with acute neurological signs. The C6–C7 intervertebral disc space is narrowed and wedge-shaped, indicating disc degeneration (*) and probable extrusion. The osteophyte extending from the caudoventral border of C6 is indicative of chronic instability. Although the survey radiographs support the presumptive diagnosis of intervertebral disc herniation, cross-sectional imaging (preferably) or myelography is required to confirm and lateralize the lesion. The C5–C6 articular process joints are widened (double-headed arrow). © 2013 British Small Animal Veterinary Association

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9.34 Lateral radiograph of the caudal cervical vertebral column of a Toy Poodle with acute neurological signs. The C6–C7 intervertebral disc space is narrowed and wedge-shaped, indicating disc degeneration (*) and probable extrusion. The osteophyte extending from the caudoventral border of C6 is indicative of chronic instability. Although the survey radiographs support the presumptive diagnosis of intervertebral disc herniation, cross-sectional imaging (preferably) or myelography is required to confirm and lateralize the lesion. The C5–C6 articular process joints are widened (double-headed arrow).

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9.35

Lateral lumbar spinal radiographs of two Dachshunds with signs of hindlimb paresis. (a) Multiple degenerative changes including narrowing of the L4–L5 (black arrow), L5–L6 and lumbosacral intervertebral disc spaces are visible. The L4–L5 facet joint is also narrowed (white arrow). It is not possible to determine which of the changes is most significant on survey radiographs alone. (b) The L5–L6 intervertebral disc space (white arrow) is the only one which is narrowed and is accompanied by narrowing of the facet joint (black arrows) and intervertebral foramen (arrowhead). A small amount of granular mineralized material lies within the ventral vertebral canal, dorsal to the intervertebral disc space. It is likely that the herniated degenerated disc material is responsible for the clinical signs but this and the lateralization, extent and degree of cord compression must be confirmed by myelography or cross-sectional imaging. The linear metal structure is a hypodermic needle placed to facilitate identification of the correct disc space at surgery. © 2013 British Small Animal Veterinary Association

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9.35 Lateral lumbar spinal radiographs of two Dachshunds with signs of hindlimb paresis. (a) Multiple degenerative changes including narrowing of the L4–L5 (black arrow), L5–L6 and lumbosacral intervertebral disc spaces are visible. The L4–L5 facet joint is also narrowed (white arrow). It is not possible to determine which of the changes is most significant on survey radiographs alone. (b) The L5–L6 intervertebral disc space (white arrow) is the only one which is narrowed and is accompanied by narrowing of the facet joint (black arrows) and intervertebral foramen (arrowhead). A small amount of granular mineralized material lies within the ventral vertebral canal, dorsal to the intervertebral disc space. It is likely that the herniated degenerated disc material is responsible for the clinical signs but this and the lateralization, extent and degree of cord compression must be confirmed by myelography or cross-sectional imaging. The linear metal structure is a hypodermic needle placed to facilitate identification of the correct disc space at surgery.

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9.36

Lateral radiograph of the caudal cervical vertebral column of a young Dobermann with cervical stenotic spondylomyelopathy (Wobbler syndrome). The C7 vertebra is wedge-shaped and rotated in a clockwise direction and the cranial vertebral foramen is markedly narrowed (double-headed arrow). These changes result in marked vertebral canal stenosis. © 2013 British Small Animal Veterinary Association

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9.36 Lateral radiograph of the caudal cervical vertebral column of a young Dobermann with cervical stenotic spondylomyelopathy (Wobbler syndrome). The C7 vertebra is wedge-shaped and rotated in a clockwise direction and the cranial vertebral foramen is markedly narrowed (double-headed arrow). These changes result in marked vertebral canal stenosis.

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9.37

Lateral radiograph showing lumbosacral disc degeneration in a large-breed dog. The endplates are sclerotic and the dorsal lamina (arrowed) and vertebral body of S1 are subluxated ventrally in relation to L7, contributing to the vertebral canal stenosis. © 2013 British Small Animal Veterinary Association

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9.37 Lateral radiograph showing lumbosacral disc degeneration in a large-breed dog. The endplates are sclerotic and the dorsal lamina (arrowed) and vertebral body of S1 are subluxated ventrally in relation to L7, contributing to the vertebral canal stenosis.

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9.38

Lateral radiograph of lumbosacral joint stenosis in a 3-year-old German Shepherd Dog with sacral osteochondrosis. The cranial endplate of S1 is not ossified dorsally (arrowheads), resulting in a flattened appearance. Small mineralized fragments are superimposed on the vertebral canal. © 2013 British Small Animal Veterinary Association

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9.38 Lateral radiograph of lumbosacral joint stenosis in a 3-year-old German Shepherd Dog with sacral osteochondrosis. The cranial endplate of S1 is not ossified dorsally (arrowheads), resulting in a flattened appearance. Small mineralized fragments are superimposed on the vertebral canal.

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9.39

(a) Lateral and (b) VD radiographs of a young dog with incomplete ossification of the atlas. The changes cannot be assessed on the lateral view, but on the VD view the arches of the atlas are not fused (arrowed), allowing direct visualization of the odontoid process. © 2013 British Small Animal Veterinary Association

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9.39 (a) Lateral and (b) VD radiographs of a young dog with incomplete ossification of the atlas. The changes cannot be assessed on the lateral view, but on the VD view the arches of the atlas are not fused (arrowed), allowing direct visualization of the odontoid process.

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9.40

(a, c) Neutral and (b, d) moderately flexed lateral radiographs of the cranial cervical vertebral column of two dogs with atlantoaxial instability. Instability results in widening of the space between the dorsal arch of C1 and the dorsal arch of C2 during flexion (double-headed arrow). The instability is more marked in (b) than in (d). © 2013 British Small Animal Veterinary Association

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9.40 (a, c) Neutral and (b, d) moderately flexed lateral radiographs of the cranial cervical vertebral column of two dogs with atlantoaxial instability. Instability results in widening of the space between the dorsal arch of C1 and the dorsal arch of C2 during flexion (double-headed arrow). The instability is more marked in (b) than in (d).

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9.41

VD radiograph of a skeletally mature Miniature Schnauzer with atlantoaxial instability due to agenesis of the dens. Note the absence of a normal odontoid process (arrowed). The instability has been stabilized using crossed pins, screws and bone cement. © 2013 British Small Animal Veterinary Association

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9.41 VD radiograph of a skeletally mature Miniature Schnauzer with atlantoaxial instability due to agenesis of the dens. Note the absence of a normal odontoid process (arrowed). The instability has been stabilized using crossed pins, screws and bone cement.

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9.42

Lateral radiograph of the cervical vertebral column of a Fox Terrier that had been attacked by another dog. The transverse processes of C3 are fractured and displaced (arrowheads). However, it remains difficult to assess whether fractures of the vertebral bodies or arches are present. © 2013 British Small Animal Veterinary Association

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9.42 Lateral radiograph of the cervical vertebral column of a Fox Terrier that had been attacked by another dog. The transverse processes of C3 are fractured and displaced (arrowheads). However, it remains difficult to assess whether fractures of the vertebral bodies or arches are present.

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9.43

Lateral radiographs of the caudal thoracic vertebral column of a dog involved in a car accident. (a) The caudal endplate of T11 is minimally displaced. It is barely visible: the dorsal (black arrowhead) and ventral (white arrowhead) margins of the ventrally displaced endplate are shown. (b) Radiograph taken at post-mortem. The endplate fracture is clearly visible (arrowheads). Muscular bracing often prevents fracture displacement in vivo, making radiographic assessment difficult. © 2013 British Small Animal Veterinary Association

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9.43 Lateral radiographs of the caudal thoracic vertebral column of a dog involved in a car accident. (a) The caudal endplate of T11 is minimally displaced. It is barely visible: the dorsal (black arrowhead) and ventral (white arrowhead) margins of the ventrally displaced endplate are shown. (b) Radiograph taken at post-mortem. The endplate fracture is clearly visible (arrowheads). Muscular bracing often prevents fracture displacement in vivo, making radiographic assessment difficult.

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9.44

(a) Lateral view of the thoracic vertebral column of a dog involved in a car accident. The T5 and T6 vertebrae overlap (arrowheads), indicating vertebral luxation. (b) DV radiograph taken at post-mortem showing complete T5–T6 intervertebral and right vertebrocostal joint luxation, as well as a fracture of T6, causing complete transection of the spinal cord. © 2013 British Small Animal Veterinary Association

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9.44 (a) Lateral view of the thoracic vertebral column of a dog involved in a car accident. The T5 and T6 vertebrae overlap (arrowheads), indicating vertebral luxation. (b) DV radiograph taken at post-mortem showing complete T5–T6 intervertebral and right vertebrocostal joint luxation, as well as a fracture of T6, causing complete transection of the spinal cord.

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9.45

Lateral view of the lumbar vertebral column of a dog showing extensive degenerative changes. Florid new bone surrounds the articular processes (black arrows) and between the lamina and base of the spinous processes of adjacent vertebrae (white arrow). The changes, although dramatic, are often of limited significance other than reduced flexibility of the vertebral column. © 2013 British Small Animal Veterinary Association

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9.45 Lateral view of the lumbar vertebral column of a dog showing extensive degenerative changes. Florid new bone surrounds the articular processes (black arrows) and between the lamina and base of the spinous processes of adjacent vertebrae (white arrow). The changes, although dramatic, are often of limited significance other than reduced flexibility of the vertebral column.

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9.46

Lateral radiographs of (a) the cervical and (b) the lumbar vertebral column in a Great Dane. (a) The C4–C5 and C5–C6 articular process joints are misshapen and surrounded by massive osteophytosis (arrowheads). These changes can arise as a result of osteochondrosis and lead to stenosis of the cervical vertebral canal as part of the cervical stenotic spondylomyelopathy. (b) The lumbar articular process joints at L3–L4, L4–L5 and L5–L6 (arrowheads) are also affected. © 2013 British Small Animal Veterinary Association

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9.46 Lateral radiographs of (a) the cervical and (b) the lumbar vertebral column in a Great Dane. (a) The C4–C5 and C5–C6 articular process joints are misshapen and surrounded by massive osteophytosis (arrowheads). These changes can arise as a result of osteochondrosis and lead to stenosis of the cervical vertebral canal as part of the cervical stenotic spondylomyelopathy. (b) The lumbar articular process joints at L3–L4, L4–L5 and L5–L6 (arrowheads) are also affected.

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9.47

Lateral view of the lumbar vertebral column of a skeletally mature Boxer with continuous bone formation (arrowheads) along the ventral aspect of the lumbar vertebral bodies (disseminated idiopathic skeletal hyperostosis), leading to vertebral body enlargement, abnormal shape and fusion. Despite its dramatic appearance, this was an incidental finding. © 2013 British Small Animal Veterinary Association

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9.47 Lateral view of the lumbar vertebral column of a skeletally mature Boxer with continuous bone formation (arrowheads) along the ventral aspect of the lumbar vertebral bodies (disseminated idiopathic skeletal hyperostosis), leading to vertebral body enlargement, abnormal shape and fusion. Despite its dramatic appearance, this was an incidental finding.

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9.48

Lateral radiographs showing the absence of the articular process joints in two dogs. (a) Mid-thoracic block vertebra without articular processes (arrowed). (b) Absence of articular process joints at T10–T11 (arrowhead). This was an incidental finding. Note also the narrowing of the intervertebral disc space at T10–T11, indicating disc degeneration. © 2013 British Small Animal Veterinary Association

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9.48 Lateral radiographs showing the absence of the articular process joints in two dogs. (a) Mid-thoracic block vertebra without articular processes (arrowed). (b) Absence of articular process joints at T10–T11 (arrowhead). This was an incidental finding. Note also the narrowing of the intervertebral disc space at T10–T11, indicating disc degeneration.

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9.49

Lateral view of the lumbar vertebral column of a dog with spondylitis involving L2 and L3. The periosteal reaction (arrowed) is palisading and continuous along the ventral aspect of the vertebral bodies. The pattern is typically associated with a migrating foreign body. © 2013 British Small Animal Veterinary Association

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9.49 Lateral view of the lumbar vertebral column of a dog with spondylitis involving L2 and L3. The periosteal reaction (arrowed) is palisading and continuous along the ventral aspect of the vertebral bodies. The pattern is typically associated with a migrating foreign body.

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9.50

Magnified lateral view of the T7–T8 intervertebral disc space of an Irish Setter with early-stage discospondylitis. Note the disc space collapse and irregular osteolysis in both endplates (arrowhead). © 2013 British Small Animal Veterinary Association

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9.50 Magnified lateral view of the T7–T8 intervertebral disc space of an Irish Setter with early-stage discospondylitis. Note the disc space collapse and irregular osteolysis in both endplates (arrowhead).

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9.51

Lateral radiographs of the lumbosacral vertebral column of two dogs with discospondylitis. (a) There is destruction of the cranial and caudal endplates and subchondral bone bordering the L5–L6 (white arrow) and L6–L7 (black arrow) intervertebral disc spaces. Destruction of the cranial endplates at these sites is subtle. The predominant feature is bone lysis; sclerosis is limited. (b) The destruction of the endplates and subchondral bone at the L7–S1 intervertebral disc space is more marked than in (a), resulting in widening of the intervertebral disc space (double-headed arrow). The L7 and S1 vertebrae are shortened, the vertebral endplates are irregular and the disc space has collapsed. © 2013 British Small Animal Veterinary Association

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9.51 Lateral radiographs of the lumbosacral vertebral column of two dogs with discospondylitis. (a) There is destruction of the cranial and caudal endplates and subchondral bone bordering the L5–L6 (white arrow) and L6–L7 (black arrow) intervertebral disc spaces. Destruction of the cranial endplates at these sites is subtle. The predominant feature is bone lysis; sclerosis is limited. (b) The destruction of the endplates and subchondral bone at the L7–S1 intervertebral disc space is more marked than in (a), resulting in widening of the intervertebral disc space (double-headed arrow). The L7 and S1 vertebrae are shortened, the vertebral endplates are irregular and the disc space has collapsed.

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9.52

Lateral view of the lumbar vertebral column of a dog with an extensive primary vertebral tumour involving L4. Extensive destruction of the spinous process, lamina, and cranial and caudal articular processes and vertebral body predominates, but new bone is also present along the ventral margin of the vertebral body. The lesion is unusual as, although it clearly arises from one vertebra, it extends to involve the lamina and articular processes of the adjacent vertebrae. This probably reflects the advanced changes. © 2013 British Small Animal Veterinary Association

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9.52 Lateral view of the lumbar vertebral column of a dog with an extensive primary vertebral tumour involving L4. Extensive destruction of the spinous process, lamina, and cranial and caudal articular processes and vertebral body predominates, but new bone is also present along the ventral margin of the vertebral body. The lesion is unusual as, although it clearly arises from one vertebra, it extends to involve the lamina and articular processes of the adjacent vertebrae. This probably reflects the advanced changes.

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9.53

Lateral view of the lumbar vertebral column of a dog with a primary vertebral tumour involving L3. The lesion is large and predominately lytic (arrowed). Despite this, the lesion is easily overlooked if the clinician is distracted by the extensive degenerative changes (ventral spondylosis and periarticular osteophytes). © 2013 British Small Animal Veterinary Association

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9.53 Lateral view of the lumbar vertebral column of a dog with a primary vertebral tumour involving L3. The lesion is large and predominately lytic (arrowed). Despite this, the lesion is easily overlooked if the clinician is distracted by the extensive degenerative changes (ventral spondylosis and periarticular osteophytes).

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9.54

Lateral view of the caudal thoracic vertebrae of a dog with vertebral neoplasia of T9 (arrowheads). The only radiographic finding was mild sclerosis of the T9 vertebral body. © 2013 British Small Animal Veterinary Association

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9.54 Lateral view of the caudal thoracic vertebrae of a dog with vertebral neoplasia of T9 (arrowheads). The only radiographic finding was mild sclerosis of the T9 vertebral body.

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(a) Lateral view of the lumbar vertebral column and (b) lateral and (c) VD views of the thorax of a dog with vertebral metastasis. (a) The dorsal lamina of the fourth lumbar vertebra is disrupted (arrowed). The margin of the area of lysis is ragged and poorly circumscribed. On MRI, the medulla of the T13 vertebral body was also seen to be completely replaced by the tumour. This change cannot be appreciated on the radiograph (*) due to superimposition of the ribs and the insensitivity of radiographs in demonstrating bone lysis. (b–c) Careful evaluation of the thorax reveals an expansile, destructive lesion of the proximal third of the right fourth rib (arrowed) and pathological fracture of the rib. © 2013 British Small Animal Veterinary Association

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9.55 (a) Lateral view of the lumbar vertebral column and (b) lateral and (c) VD views of the thorax of a dog with vertebral metastasis. (a) The dorsal lamina of the fourth lumbar vertebra is disrupted (arrowed). The margin of the area of lysis is ragged and poorly circumscribed. On MRI, the medulla of the T13 vertebral body was also seen to be completely replaced by the tumour. This change cannot be appreciated on the radiograph (*) due to superimposition of the ribs and the insensitivity of radiographs in demonstrating bone lysis. (b–c) Careful evaluation of the thorax reveals an expansile, destructive lesion of the proximal third of the right fourth rib (arrowed) and pathological fracture of the rib.

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Lateral view of the lumbosacral vertebral column of a male dog with urethral neoplasia. Thick, palisading new bone (arrowed) is present along the ventral margin of multiple coccygeal vertebrae. The change is consistent with metastatic disease. © 2013 British Small Animal Veterinary Association

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9.56 Lateral view of the lumbosacral vertebral column of a male dog with urethral neoplasia. Thick, palisading new bone (arrowed) is present along the ventral margin of multiple coccygeal vertebrae. The change is consistent with metastatic disease.

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9.57

Lateral view of the thorax of a cat with a large soft tissue sarcoma between the scapulae. Infiltration of the mass into the dorsal spinous processes has resulted in pathological fractures of the mid-portion of the T4 and T5 dorsal spinal processes (arrowed). A mild periosteal reaction borders the fracture site (including T3). © 2013 British Small Animal Veterinary Association

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9.57 Lateral view of the thorax of a cat with a large soft tissue sarcoma between the scapulae. Infiltration of the mass into the dorsal spinous processes has resulted in pathological fractures of the mid-portion of the T4 and T5 dorsal spinal processes (arrowed). A mild periosteal reaction borders the fracture site (including T3).

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(a) Lateral and (b) VD views of the thoracolumbar vertebral column of a dog. Hemilaminectomy and spinal cord decompression for intervertebral disc extrusion had previously been performed. Neurological signs recurred 1 year later. (a) The missing articular process is difficult to recognize on the lateral view but the borders (black arrows) of the laminectomy are visible. The nucleus of the intervertebral disc at L3–L4 is mineralized (white arrow). (b) On the VD view, the missing process joint is appreciated better (white arrows). There does not appear to be any indication of instability as a result of the previous surgery. © 2013 British Small Animal Veterinary Association

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9.58 (a) Lateral and (b) VD views of the thoracolumbar vertebral column of a dog. Hemilaminectomy and spinal cord decompression for intervertebral disc extrusion had previously been performed. Neurological signs recurred 1 year later. (a) The missing articular process is difficult to recognize on the lateral view but the borders (black arrows) of the laminectomy are visible. The nucleus of the intervertebral disc at L3–L4 is mineralized (white arrow). (b) On the VD view, the missing process joint is appreciated better (white arrows). There does not appear to be any indication of instability as a result of the previous surgery.