MSK 2 Flashcards
What are the two broad categories of inflammatory bone diseases?
infectious and non infectious
what kind of viruses cause viral bone lesions in young growing animals with open physes?
pestiviruses like BVDV, classical swine fever, canine distemper, and border disease virus
what is the pathogenesis of biral bone lesions?
viruses damage osteoclasts–>abnormal osteoclast activity–> metaphyseal trabeculae are not remodelled –> metaphyseal osteosclerosis/growth retardation lattices
what is the difference between osteitis and osteomyelitis?
osteitis is inflammation of the bone, osteomyelitis is inflammation of the bone and medullary cavity
osteomyelitis is most often associated with
bacterial or fungal infections
name 3 sources of bone infections
- direct introduction like via open fracture or penetrating wound
- extension from soft tissues like cellulitis, periodontitis, etc
- hematogenous spread
sometimes with bacterial infection you can get embolic osteomyelitis. Describe the pathogenesis
septicemia–>bacteria spread via the blood–>the blood supply to the growth plate involves capillaries that make sharp bends which are prone to turbulence, thrombosis, and slow flow–>bacteria can lodge here and proliferate and spread locally–>leading to suppurative osteomyelitis
what is this lesion showing?
embolic osteomyelitis from a bacterial infection
list some comon bacterial species associated with embolic osteomyelitis
trueperella pyogenes, staphylococcus sp, escherichia coli, salmonella enterica
what is this arrow pointing to? this is tissue from a foal
metaphyseal suppurative osteomyelitis (pus above and below the growth plate)
bacterial osteomyelitis is also called lumpy jaw in cattle and is caused by
actinomyces bovis
what is the pathogenesis of actinomyces bovis?
damge to the oral mucosa provides portal of entry–> soft tissue infection develops–> extension of infection into the mandible–> pyogranulomatous osteomyelitis
list 3 gross lesions of lumpy jaw
- necrotic tracts of pyogranulomatous inflammation, may drain as thick pus to the skin (fistula)
- concurrent periosteal bone proliferation and lysis
- honeycomb appearance of the mandible
this is a cow mandible. what disease is this and what is the etiology?
lumpy jaw/bacterial osteomyelitis
actinomyces bovis
this is tissue from a cow. what is your suspected diagnosis?
lumpy jaw/bacterial osteomyelitis. you can see the pockets of swelling, fibrous scar tissue, and tracts of pyogranulomatous inflammation
how does fungal osteomyelitis usually appear?
pyogranulomatous to granulomatous osteomyelitis with bone lysis and periosteal new bone formation
what is an important differential diagnosis for fungal osteomyelitis?
bone neoplasia
what is one important consideration when you are attempting to diagnose fungal osteomyelitis?
it is less common than bacterial and the risk is very dependent on geographical location and the specific species common in certain areas
what are the usual clinical signs associated with fungal osteomyelitis?
fever, weight loss, and bone pain
what are two things this could be?
fungal osteomyelitis or bone neoplasia
describe the pathogenesis of fungal osteomyelitis using blastomyces as your pathogen
blastomyces inhalation–>hematogenous spread and apparent predilection for lungs (fungal pneumonia) and less often appendicular bones–>pyogranulomatous osteomyelitis
what are 3 gross lesions to look for with fungal osteomyelitis?
- periosteal new bone thickens the bone contour
- loss of cortical bone (cortex gone)
- suppurative to pyogranulomatous material present
what is osteonecrosis and what causes it? What is the pathogenesis? What is the result?
necrosis of the bone, causes can be infection, trauma, neoplasia, frostbite, etc.
pathogenesis: bone lesions that causes damage to the blood supply causing ischemia and infarction
area is slowly removed by osteoclasts so if it is not removed a sequestrum can form. the outcome depends on the blood supply, the size, and the proximity to viable tissue
what is shown here?
bone necrosis, well demarcated area tan area
what is a bone sequestrum and what causes it?
fragments of necrotic bone that are isolated from blood supply, almost always associated with inflammation, caused by comminuted fractures creating fractures, can interfere with healing and cause non union fractures
what is shown here?
osteomyelitis with sequestrum
what is metaphyseal osteopathy? what do the lesions look like?
also known as hypertrophic osteodystrophy, affects young large and giant breed dogs, it is very painful and resolves spontaneously. We do not know what causes it.
lesions: initially bilaterally symmetrical suppurative and fibrinous osteomyelitis of the metaphysis of multiple long bones, it can have a “double growth plate” appearance. In chronic stages there will be new periostal bone
what disease is shown here?
metaphyseal osteopathy, you can see the growth plate and then a second band of inflammation
what is aseptic necrosis and what is the specific type that is common?
osteonecrosis NOT associated with infection
aspetic necrosis of the femoral head: affects young minature dog breeds
- femoral head infarction, necrotic bone resorbed by osteoclasts, articular cartilage collapses
what is hypertrophic osteopathy? who gets it, what do the lesions look like, and what is it associated with? Pathogenesis?
hypertrophy of the bones, occurs in dogs usually sometimes horses, lesions are progressive periosteal new bone formation affecting the distal limbs, typically associated with concurrent intrathoracic disease
pathogenesis is unknown, but we know the condition will regress if the primary problem is resolved (a pulmonary/lung problem)
what is this disease?
hypertrophic osteopathy
what are osteochondromas? How do they normally appear?
aka multiple cartilaginous exostoses which are benign nodular growths projecting from the outer bone surface
the lesion is usually a mass of trabecular bone and cartilage arising from the metaphyseal areas of multiple bones. they appear at a young age and keep growing until the animal stops growing at skeletal maturity
this is a bone cross section. What is shown here?
an osteochondroma
this is the rib of a puppy. what is shown here? are these lesions usually problematic?
osteochondroma
these can resolve once the animal stops growing so if they are small enough they may not cause any issues
what are the two clinically significant bone neoplasms? what do you need in order to diagnose these?
osteosarcoma and chondrosarcoma
you need a biopsy and NOT a cytology to diagnose. you also need a clinical history and radiographs usually too
what is the cell of origin for osteosarcoma? How do these cells act? What is an important DDX? Where does this cancer metastasize to?
malignant osteoblasts; they produce bone and destroy existing bone
DDX: osteomyelitis
this cancer is aggressive and fast growing, often metastasizes to the lungs
where does osteosarcoma usually arise?
distal radius and ulna, proximal humerus, distal femur, distal or proximal tibia, “away from the elbow, towards the knee”, but can arise in any bone
does osteosarcoma usually invade into the joint spaces?
no
what kind of tumor is this likely?
osteosarcoma
what are some ways to tell between osteomyelitis and osteosarcoma?
- osteomyelitis can infiltrate the joints, osteosarcoma does not
- osteomyelitis comes with fever, osteosarcoma does not
- weight loss is seen with osteomyelitis, not in osteosarcoma
- a draining tract is possible in osteomyelitis, not found in osteosarcoma
- pain is seen with both
what is the cell of origin for chondrosarcoma and how do the tumors usually behave?
malignant chondrocytes that produce cartilage, they are slow growing with localized bone destruction, arises from flat bones
what tumor is this likely arising from the skull?
chondrosarcoma
list some neoplasms that often metastasize to the bones and the most common locations they metastasize to
carcinomas mostly of the mammary gland, lung, and prostate
ribs, vertebrae, and proximal long bones
a cat comes to your clinic and it’s foot looks like this. what are you concened about?
i am concerned about lung-digit syndrome, which is spread from a pulmonary carcinoma. once the tumor has spread, it proliferates and destroys the nail bed and can cause sloughing of the claw. I would immediately want to take thoracic radiographs to investigate the lungs
what is the underlying lesions of metaphyseal osteopathy?
the double growth plate
hypertrophic osteopathy is associated with lesions in what other body system? Give two examples of these associated lesions
intrathoracic disease such as lung tumors or pneumonia
what is chondrodysplasia?
congenital disorder where there is abnormal growth of cartilage, like disproportionate dwarfism (short legs with normal sized heads)
what is osteopetrosis? what is the cause? what kind of animals are predisposed?
osteopetrosis=osteosclerosis (increased bone density) with no medullary cavity
cause: defective osteoclasts fail to resorb bone leading to improper remodelling
angus cattle and peruvian paso horses preisposed, also an association with BVDV in cattle
what disease is this?
osteopetrosis/osteosclerosis, note the loss of medullary cavity
what is osteogenesis imperfecta?
a genetic disease where you have abnormal type I collagen, leading to reduced trabecular bone leading to fractures, joint laxity, and abnormal dentin
what is the word for:
- partial or complete fusion of the digits
- increase in the number of digits
- increase in the number of limbs
syndactyly
polydactyly
polymelia
what is the difference between brachygnathia inferior and superior?
inferior is a shortening of the mandible leading to an overbite
superior is a shortening of the maxilla, which is seen in brachy breeds
abnormal ventral curvature of the spinalcolumn is called
lordosis
what is this showing?
lordosis
abnormal dorsal curvature of the spinal column is called
kyphosis
what is shown here?
kyphosis
abnormal lateral deviation of the spinal column is called
scoliosis
what is spina bifida?
defective closure of the dorsal vertebral lamina in the vertebral column
