Pathology of Bone, Pt. 2 Flashcards
How does lead poisoning lead to toxic osteodystrophy? What can be seen grossly?
lead interferes with osteoclast activity
increase in bone density (osteosclerosis) in the metaphysis called a lead line
When is hypervitaminosis A common? What does this cause?
cats being fed high quantities of bovine livers that are rich in vitamin A for a long time (farms in Australia and Uruguay)
osteophyte (nodules of new bone on periosteal surface) formation around joints of the cervical vertebrae, shoulder, and elbow —> deforming cervical spondylosis, ankylosing spondylosis, disseminating ankylosing osteoarthropathy
Cervical akylosing spondylosis:
degeneration of vertebral bodies, fixating the joint —> hypervitaminosis A
What are the 3 main ways that bones respond to injury?
- necrosis
- bone fracture
- inflammation
What are the main 3 causes of necrosis in bone? How does the bone appear grossly? Microscopically?
- ischemic injury
- trauma
- inflammatory and neoplastic bone disease
necrotic bone appears paler
cell death with loss of osteocytes from their lacunae
What influences the outcome of osteonecrosis? What are the main 2 results?
size and extent of necrosis; the extent an strength of collateral circulation; local repair mechanisms
- complete resorption and replacement of necrotic bone
- formation of a sequestrum - a piece of necrotic bone remains and is isolated from the remaining viable bone
How are sequestrum fixed in bone?
sequestrum must be removed and the surrounding bone tissue must be stimulated to facilitate new bone formation for healing
What is an involucrum?
the bone’s attempt to wall off a sequestrum, resulting in the formation of a layer of granulation tissue and reactive bone
What is the difference between traumatic and pathologic bone fractures?
TRAUMATIC = normal bone broken by excessive force
PATHOLOGIC = abnormal bone broken by minimal trauma or normal weight bearing
What is the difference between complete and incomplete fractures?
COMPLETE = bone is completely broken into separate pieces
INCOMPLETE = crack that does not completely break the bone into two or more pieces
What is the difference between closed (simple) and open (compound) fractures?
CLOSED (SIMPLE) = skin and soft tissue remain intact
OPEN (COMPOUND) = bone ruptures skin and soft tissue
What is the difference between avulsed fractions and microfractures (infractions)?
AVULSION = fracture caused by the pull of a ligament/muscle tendon at its insertion into the bone
MICROFRACTURE (INFRACTION) = fracturing of trabeculae without external deformation of cortical bone
What is a common finding in pigs that exhibit continual tail biting?
original fracture of vertebral bodies (typically caused by fighting) causes infection to travel down the spinal cord and to the tail —> fracture can cause an abscess formation that can compress the spinal cord
Pathologic fracture caused by osteosarcoma:
What are the 4 steps of fracture repair?
- blood clots into a hematoma at the fracture site
- hematoma produces a meshwork to facilitate the proliferation of fibroblasts and new vessels, which starts the healing process
- macrophages and inflammatory cells resorb necrotic tissue and stimulate osteoprogenitor cells to transform into osteoblasts and chondroblasts to deposit woven bone or cartilage
- woven bone and cartilage are completely replaced by mature bone
Healed fracture, horse rib
Why is proper stability of bone fragments necessary in fracture repair?
if bone is lined up in a way that does not support angiogenesis, osteoprogenitor cells will become fibroblasts and not osteoblasts, since connective tissue is more easily made under hypoxic environments
What are 4 complications associated with bone fractures?
- bone necrosis and formation of sequestrum
- nonunion fracture - pseudoarthrosis (false joint) formation
- osteomyelitis from compound fractures
- cachexia - difficult to feed themselves
What kind of inflammation is a result of fractures? What does this cause?
osteitis/osteomyelitis, aseptic inflammation
trauma causes osteoperiostitis with formation of exostosis (osteophytes)
In what kinds of animals if osteomyelitis most common in? What is a common source of osteomyelitis in neonates?
young farm animals as a result of bacteremia or septicemia
omphalophlebitis (inflammation of umbilical vein)
Where does infection from osteomyelitis typically localize in piglets?
vertebral bodies (typically from tail biting)
Infection typically localizes in the metaphyses of long bones. Why is this so?
microanatomy of the vessels —> veins are thin, which facilitates the exchange of nutrients and bacteria from the blood
Abscess formation and pus in joints:
Where should you look for lesions of osteomyelitis in young animals? How are abscesses able to form fistulous tracts?
at the physis (growth plate)
neutrophils have enzymes that are able to break down connective tissue, allowing the abscess to drain (typically results in pus draining in the joint)
Physitis, foal:
know it’s a young animal bc of the presence of the growth plate on top
on the bottom - growth plate is missing and it is surrounded by necrotic tissue and a red ring of inflammation
Embolic osteomyelitis, foal:
What causes “lumpy jaw” in cows? What is “lumpy jaw?”
osteomyelitis caused by Actinomyces infection
Bovine Actinomycosis, maxilla involvement:
Chronic pyogranulomatous osteomyelitis, Actinomycosis:
maxillary sinus full of pus
What is a common cause of “lumpy jaw” in cows?
plant material impaction injures the gingival cavity, allowing Actinomyces into the blood, where it spreads through facial bones
What is a common histological finding in Bovine Actinomycosis (Lumpy Jaw)?
the formation of sulfur granules containing colonies of the bacteria surrounded by amorphous and elongated Ig-Ag complexes called Splendore Hoeppli
How can Actinomyces bovis be observed in a histological slide?
Gram stain (+)
How does the mandible tend to look like in a cow with lumpy jaw?
cavities (osteolysis) form followed by bone remodeling and proliferation, making the mandible seem large and lumpy
What is hypertrophic pulmonary osteoarthropathy/osteopathy known as? What animal is it most common in? What is it?
Marie’s Disease
dogs
observed in individuals with an intra-thoracic space-occupying mass (tumor, abscess) characterized by lameness and painful swelling of limbs caused by periosteal bone proliferation in long bones
Is it possible for bone changes caused by Marie’s Disease to regress? If so, how?
yes; if the space-occupying lesion in the thoracic cavity is removed
When is Marie’s Disease common in dogs? Mares?
DOG - young dogs with rhabdomyosarcomas of the urinary bladder
MARE - ovarian tumors
Marie’s disease:
radius, ulna, metacarpus have new bone production
What is Canine Craniomandibular osteopathy (Lion Jaw)? In what dogs is it most common?
proliferative disorder of unclear etiology confined to the bones of the skull, especially the mandibles, occipital bone, and temporal bone, where the affected animal exhbits discomfort when chewing or inability to open their mouth to eat
West Highland White Terriers, 4-7 months
Lion Jaw:
prominent mandible and tympanic bulla due to the formation of osteophytes
Are primary or secondary tumors more common in bone neoplasia? In what animals are they most common? How are they typically classified in these animals?
primary (tumors of bone and cartilage cell-lines)
dogs, to a lesser extent cats
dogs = malignant
horses, cattle, other domestic animals = benign
Where are ossifying fibromas and multilobular tumor of bone common?
rostral mandible of horses (and other large animals)
top of the head in dogs
Maxillary osteoma:
maxillary sinus filled with tissue that looks like bone
high swelling
botfly in nasal trabeculae (O. orvis)
What are osteosarcomas? What breeds of dog are most susceptible?
most common primary bone tumor in dogs and cats
male (~7.5 y/o) large breeds - St. Bernards, Great Danes, Irish Setters, Boxers, Dobermans, Rottweilers, Labrador Retrievers
What is the common saying for the predilection site of osteosarcomas?
“close to the knee, away from the elbow”
- can still occur in all bones! (appendicular > axial)
Osteosarcoma:
opaque = tumor proliferation
can metastasize into the lungs and cause respiratory failure
Osteosarcoma, distal femur:
infiltrating tumor shows no clear boundaries and invades surrounding tissue
- can’t really tell what’s going on
In all species, chondrosarcomas involed what kinds of bones?
flat bones more often than long bones
- ribs, nasal turbinates, pelvis, top of skull
Chondrosarcoma, skull:
compresses brain and infiltrates frontal sinus
shiny in real life, resembling cartilage
Chondrosarcoma, ribs:
translucent
infiltrating and destroying rib
