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)