Bone Injury and Bone Injury and 

Inflammatory Bone DiseasesInflammatory Bone Diseases

Alfonso LópezAlfonso LópezAtlantic Veterinary CollegeAtlantic Veterinary College

U i i f P i Ed d I l dU i i f P i Ed d I l dUniversity of Prince Edward IslandUniversity of Prince Edward Island

January 7, 2010 January 7, 2010

Bone Bone Necrosis / Cross SectionNecrosis / Cross Section

The texture of the necrotic bone notably changes. Instead of being hard the necrotic bone becomes friable. This change can be NN gdemonstrated by scratching the affected bone with a sharp object.

NN

Note the large area of necrosis (N) which appears as a pale discolored bone

Normal vs Necrotic Bone / HistopathologyNormal vs Necrotic Bone / Histopathology

Normal bone typically shows Normal bone typically shows osteocytesosteocytes inside the bone inside the bone

Necrotic boneNecrotic boneNormalNormal

**lacunae. These lacunae. These osteocytesosteocytesappear as dark cells (appear as dark cells (arrows)arrows)

In contrast, note the lack of In contrast, note the lack of visible visible osteocytesosteocytes in the in the

ti bti b hh ththnecrotic bone necrotic bone where where the the lacunae lacunae are empty are empty

((arrowheadsarrowheads). ). AlsoAlso, note in the necrotic , note in the necrotic

b th l k f bb th l k f bbone the lack of bone bone the lack of bone marrow marrow cells (cells (asterikasterik))

Aseptic necrosis of bone occurs as a result of ischemia or trauma. As long as the blood circulation has not been compromised, necrotic bone is reabsorbed by osteoclastic activity.

.Necrosis Necrosis  ResorptionResorptionWoven bone  Woven bone  Mature boneMature bone

Fractured bone Fractured bone spiculespiculeNote the woven bone (W) joining and replacing anNote the woven bone (W) joining and replacing an old fractured spicule of mature lamellar bone (l).

Mature lamellar bone (l) appears as pink and wellMature lamellar bone (l) appears as pink and well organized in which collagen fibers are compacted and arranged in a parallel fashion. In contrast, woven bone (w) is less compacted and the collagen fibers are organized in a crisscross fashion.be s a e o ga ed a c ssc oss as o

Eventually, woven bone (w) would be replaced by mature lamellar bone (l).( )

Necrosis Necrosis  ResorptionResorptionWoven bone  Woven bone   Callus (Callus (sacarsacar

Bone Necrosis.Bone Necrosis.

A fractured rib with callus formationA fractured rib with callus formation. If the size of the necrosis is large like in this fractured rib, repair occurs but leaves a visible scar known as callus. Note the enlargement of the rib at the site of the callus.

A healing fracture starts with hemorrhage and the formation of a hematoma at the site of fracture. This hematoma is rapidly invaded by fibrous connective tissue forming a temporary fibrous bridge between the edges of the fracturetemporary fibrous bridge between the edges of the fracture.

With time, the fibrous connective tissue becomes infiltrated with osteoblasts which lay down osteoid. The osteoid and the osteoblasts form woven (immature) bone.

Finally, woven bone is reabsorbed and replaced by mature (lamellar) bone forming a secondary callus.

Necrosis Necrosis  ResorptionResorptionWoven bone  Woven bone   Callus (scar)Callus (scar)

BB C ll f OldC ll f Old RibRib F tF tBone Bone Calluses from Old Calluses from Old Rib Rib FracturesFractures

Note the multiple bone calluses in the fractured rib cage (arrows) .

Passing through the birth canal is often traumatic enough to cause rib fractures in neonates.

Acquired trauma such as kicking or being hit by a car are other common causes of multiple rib fractures.

Necrosis Necrosis  Lack of Lack of resorptionresorption Bone Bone sequestrumsequestrum

Note large bone sequestrumin the vertebral body (asterisk)

A bone sequestrum is formed when a large piece of necrotic bone becomes isolated from circulation and cannot be reached by blood cells and osteoclasts.

A band of connective tissue known as involucrum generally surrounds the sequestered dead bone.

Necrosis Necrosis ºº resorption resorption ºº inflammation inflammation ºº proliferationproliferation

Ch i lif ti t litiCh i lif ti t liti

pp pp

Chronic, proliferative osteomyelitis. Chronic, proliferative osteomyelitis.

Distal part of large bone.Distal part of large bone.

Note the extensive Osteophyte proliferation resulting from chronic arthritis and osteomyelitis.

Chronic and persistent inflammation and necrosis of bone induces abnormal remodeling characterized by the growth of bone nodules k O t h t I thknown as Osteophytes. In severe cases, these Osteophytes cover large portions of the periosteal bone or joint.

As shown in this case, proliferation andAs shown in this case, proliferation and formation of Osteophytes obliterate the entire diaphysis of the femur in this pig.

Suppurative (pyogenic) Suppurative (pyogenic)

Osteomyelitis resulting fromOsteomyelitis resulting fromOsteomyelitis resulting from Osteomyelitis resulting from bacteremia in a young animal.bacteremia in a young animal.

I h b h h h i dIn the bone shown here there is good evidence of suppurative (neutrophilic) inflammation and osteolysis which appear as a large pale area of discolored bone. N t th t th i d t i th di h iNote that there is exudate in the diaphysis (below the growth cartilage) and metaphysis (above of the growth cartilage) of this bone.

Remember that in osteomyelitis, the suffix myelitis means inflammation of bone marrow. It should not be confused with myelitis as in inflammation of the spinalmyelitis as in inflammation of the spinal cord (i.e., encephalomyelitis).

Metaphyseal blood vessels are commonly the site of septic osteomyelitis in farm

i l d f lanimals and foals.

S ti ( i )S ti ( i )Suppurative (pyogenic). Suppurative (pyogenic).

OsteomyelitisOsteomyelitis from neonatal from neonatal bacteremiabacteremia in a young calf.in a young calf.

Another view of suppurative osteomyelitis. Note the purulent exudate

d di l ti f b ti ( t i k)and dissolution of bone tissue (asterisk). In most cases if septic inflammation, neutrophils induce extensive lysis of the bone which often results in pathological f tfractures.

An aspirate of this type of lesion would reveal large numbers of neutrophils some of which may contain bacteria.y

NormalNormal Osteomyelitis Osteomyelitis

Osteomyelitis. HistopathologyOsteomyelitis. Histopathology

Note the large cluster of leukocytes in the bone. Also note the bone trabecula in this area has already been reabsorbed by ostoclastic activity and replaced by fibrotic tissue as a first step for repair. Assuming that the infection is controlled, new woven bone will replace this localized area of fibrosis.

Bone infections occur commonly as a sequel of bacteremia Compared to othersequel of bacteremia. Compared to other tissues, bone infections are difficult to treat.

ActinocycosisActinocycosis-- Lumpy JawLumpy JawNote the swelling of the jaw due to localized osteomyelitis with exudate in the ulcerated skin (fistula). The pathogenesis of this lesion generallypathogenesis of this lesion generally involves soft tissue trauma of the oral cavity with penetration of opportunistic Actinomyces bovis.

The macerated jaw reveals exuberant exostosis. Pyogranulomatous inflammation of the mandible in Actinomycosis is generally unilateralActinomycosis is generally unilateral. Bone deformation and severe exostosis occur following episodes of bone necrosis and repair as is the case with chronic inflammationchronic inflammation.

(See figure 10-29 Thomson's book).

Spinal AbscessSpinal Abscess

This pig was unable to stand due a to spinal cord injury resulting from aspinal cord injury resulting from a spinal abscess.

Abscesses in the vertebrae are common in pigs and cattle. It is

t l t d th t "t il bit " ki i f tipostulated that "tail bite" skin infections often result in bacterial emboli lodging in the vertebral bodies (spondylitis). If several animals are affected in a herd, it i di t h lth tit indicates poor health management. Vertebral inflammation often extends to the meninges and causes meningitis.

Note the large vertebral abscessNote the large vertebral abscess (asterisk) with compression of the spinal cord (arrows).

Compression of the spinal cord could l d t th l i l f t i thlead to pathological fractures in the vertebrae.

Chronic osteomyelitis Chronic osteomyelitis Rhodococus equiRhodococus equi / foal/ foal

Note the lytic lesion in the x-ray and in the corresponding hemisection of vertebra. This foal had been previously diagnosed

ith i d t iwith sepsis and ataxia.

Rhodococcus equi was isolated from the exudate in a vertebra. Omphalophlebitis is a common source of bacterial embolisms in neonates.

Bacterial embolisms lodge primarily in the epiphyseal vessels of long bones. These infections are important in young foalsinfections are important in young foals where 70% of foals with joint-ill also have septic osteomyelitis.

The inflammation in this foal extended into the spinal canal causing meningitis.

Chronic mycotic osteomyelitis / Canine Chronic mycotic osteomyelitis / Canine pelvis femur and vertebrapelvis femur and vertebrapelvis, femur, and vertebra. pelvis, femur, and vertebra.

Blastomycosis. Blastomycosis. Bone inflammation and with notable exostosis

l i i f i d bare commonly seen in infections caused by systemic mycoses. These fungal diseases commonly cause chronic disseminated osteomyelitis that is part of a multi-systemic i f ti i l i th ti h l hinfection involving other tissues such as lymph nodes, spleen, skin, liver, brain, eyes, etc.

Systemic (deep) mycoses as their name implies, are disseminated fungal infectionsimplies, are disseminated fungal infections caused by dimorphic fungi such as Blastomyces dermatitides, Coccidioides immitis and Cryptococcus neoformans. These fungi disseminate, through the blood and lymphaticdisseminate, through the blood and lymphatic systems, to many tissues including bones.

Note the chronic granulomatous osteomyelitis characterized by proliferative lesions ( t i ) i th k l t f thi d(exostosis) in the skeleton of this dog.

A microscopic view is shown in the next slide.

Chronic osteomyelitis / Canine Chronic osteomyelitis / Canine Blastomycosis. HistopathologyBlastomycosis. Histopathology

A tssue section (PAS stain) of a lytic bone lesion in the leg of a mature dog with a history of weight loss, cough and l Th d l hibit dlameness. The dog also exhibited ulcerated skin lesions and a disseminated lymphadenomegaly (enlargement of lymph nodes). Many organs had multiple

lpyogranulomas.

Note the several PAS-positive yeasts (Blastomyces dermatitides) inside a multinucleated giant cell. Because of amultinucleated giant cell. Because of a high carbohydrate contents, the walls of yeast stain positive with PAS stain.

Pulmonary hypertrophic Pulmonary hypertrophic osteoarthropathy. Dogosteoarthropathy. Dogosteoarthropathy. Dogosteoarthropathy. DogPulmonary hypertrophic osteoarthropathy is a disease of convoluted pathogenesis characterized by extensive proliferation of osteophytes along the entire appendicularosteophytes along the entire appendicular skeleton. In humans this condition is called Marie's Disease.

The pathogenesis is still controversial but a i i th th hspace-occupying mass in the thorax such

as large abscesses or tumors is often incriminated. If the thoracic mass is removed, bone lesions tend to regress.

Megakarocytes released into circulation are normally trapped in the pulmonary capillaries. When there is a space occupying mass in the thorax, pulmonary h t i i d l t ihypertension induces vascular anastomosis that allows for magakaryocytes to reach the periosteal bone.

Note the severe hyperostosis along the entire periosteal surface of these bones.

Craniomandibular osteopathy Craniomandibular osteopathy (Lion's jaw). Canine. (Lion's jaw). Canine. Craniomandibular osteopathy is a localized bone disease in dogs of unknown etiology that results in extensive periosteal proliferation of the mandible and cranial bones. It is mainly seen in West Highland White and Scottish Terriers.

Lesions affect only the head, are bilaterally symmetrical and self-limitingbilaterally symmetrical, and self-limiting. The tympanic bullae are severely affected in most cases. Clinically, there is painful swelling and enlargement of the temporal-maxillary region Grossly andtemporal-maxillary region.Grossly and radiographically, there are proliferative changes in the temporal and maxillary bones causing bony bridging on the periosteal surfaceperiosteal surface.

Some images were acquired from veterinary colleges of Some images were acquired from veterinary colleges of Canada, United States and Mexico and the names of Canada, United States and Mexico and the names of pathologists who contributed with some slides are pathologists who contributed with some slides are known. Their valuable contribution is sincerely known. Their valuable contribution is sincerely acknowledged.acknowledged.

I would like to thank Adriana Lopez, University of I would like to thank Adriana Lopez, University of Western Ontario, and Eileen Western Ontario, and Eileen KinchKinch for editorial for editorial assistance; Dr María Forzán Atlantic Veterinaryassistance; Dr María Forzán Atlantic Veterinaryassistance; Dr. María Forzán, Atlantic Veterinary assistance; Dr. María Forzán, Atlantic Veterinary College, for critically reviewing these modules.College, for critically reviewing these modules.

Bone Injury and Inflammatory Bone DiseasesBone Injury and Inflammatory Bone DiseasesBone Injury and Inflammatory Bone DiseasesBone Injury and Inflammatory Bone Diseases

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