MSK 1 Flashcards
what is the weakest place in growing bones?
the growth plate or physis
what is the one thing that a fracture MUST have in order to heal?
adequate blood supply
young animals often get what kind of fractures?
along the growth plate (different salter harris classifications)
what is the most common type of salter harris fracture in young animals?
type II along physis and into metaphysis
angular limb deformities are common in what kind of animals?
fast growing animals like dogs and horses
what are thw two types of angular limb deformities?
valgus: lateral deviation or splay legged
varus: medial deviation or bow legged
you are brought a cute rescue pittie mix with bowed legs and the new owner wants to know what it is and what caused it. You tell them…
the dog has varus or medial deviation, form of angular limb deformity, and it is caused most commonly by asymmetric damage to the growth plate (one side closes and the other grows), can also be caused by malposition in utero, joint laxity, hypothyroidism, malnutrition, or sometimes we aren’t sure why
name these conditions
top is valgus, bottom is varus, both forms of angular limb deformities
this is from a puppy. what is the arrow pointing to and why is it significant?
it is pointing to an area where the growth plate of the radius dissapeared, so no further growth can occur at this site. this likely happened because of some trauma to the radial growth plate in that location
fractures occur when the ______ exceeds the _____
mechanical force
bone strength
define a fracture
a break/rupture resulting in a physical discontinuity in a bone
what are the two ways in which fractures are classified?
traumatic (forces break a normal healthy bone) and pathologic (forces break an unhealthy or diseased bone)
list the ways to classify a fracture
open/closed
displaced or not
comminuted
transverse/oblique/spiral/linear
location (proximal, distal, midiaphyseal)
name the bone
what is an avulsion fracture
when a ligament pulls bone away from a site of insertion
what is a greenstick fracture?
where one cortex is broken but the other side is not, happens in young animals (think of a green twig breaking and only one side breaks while the other stays in tact)
what are the 5 steps in fracture healing?
- hematoma
- fibrous tissue
- woven bone and cartilage laid down
- soft callus or primary callus forms
- hard callus or secondary callus forms (woven bone to lamellar bone)
list some reasons for non-union fractures
inadequate blood supply, instability/excessive forces or motion, infection, pathologic underlying disease, malnutrition, necrotic tissue like a sequestrum
what does the word osteodystrophy mean? What causes this? What is a common result?
abnormal bone growth
caused by nutritional or hormonal imbalances, toxicities, etc
common result is pathologic fractures and pain
osteodystrophy is more commonly seen in what kind of animal?
growing animals
the top arrow is pointing to what? What is the cause of this lesions and what is the pathogenesis?
it is showing a growth arrest line (just above the growth plate), caused by debilitating disease or malnutrition. the trabeculae in the metaphysis are abnormally algined so that they are parallel to the physis instead of perpendicular
Pathogenesis: inciting cause–>long bone growth stops–>abnormal osteoclast activity–>lines are carried into metaphysis as growth resumes
what is seen here and what does this indicate?
serous atrophy of fat, indicating the animal was either anorexic or in starvation, the medullary fat has become gelatinous and see through rather than white and opague. note also the cortex is thinner than normal
what is osteoperosis? How is it different than osteopenia?
reduced bone mass and density with associated pathological fractures
osteopenia is reduced bone mass and density WITHOUT pathological fractures
mineralization is normal in both scenarios
what causes osteoperosis?
calcium deficinecy: low calcium causes an increase in PTH which stimulates osteoclasts to resorb more bone
starvation: low energy/protein/minerals
physical disuse/atrophy: very little stimulation to lay down new bone
basically anything that tips the balance so that more bone is absorbed than replaced
what is a common medical treatment that can lead to osteoperosis?
a cast or splint!
explain how bones can be normally mineralized in osteoperosis if the pathogenesis involves low calcium levels
when the bones were formed, the individual was healthy and had adequate calcium leading to normal mineralization, then comes the actual cause of osteoperosis such as starvation and the levels of calcium decrease which stimulates osteoclasts to resorb more bone, the bone isn’t replaced so the bone desnity goes down and makes them weak and brittle
what is this showing?
osteoperosis, note the bottom photo the cortex is thinner and there is hardly any trabecular bone filling the medullary cavity, bones are brittle with reduced density
what is rickets? What results will you see from this disease? What causes this disease?
failure of bone mineralization in young growing animals
leads to thickened growth plates from lack of cartilage mineralization and abnormal endochondral ossification, bones are soft
causes: vitamin D and phosphorus deficinecy
what disease is this?
rickets, you can see the thickened growth plate and retained cartilage that will not mineralize
list gross features of rickets
segmental growth plate thickening
multifocal growth plate lesions
prominant at sites of rapid growth (adjacent to growth plates) like the metaphysis and epiphysis
may also see on bone cross section, tongues of un resorbed cartilage extending into the metaphysis
what disease is this?
rickets, this is showing the costochondral junction and the growth plates of ribs are being thickened and cartilaginous, looking like rosary beads
what disease is this?
rickets, this is showing the costochondral junction and the growth plates of ribs are being thickened and cartilaginous, looking like rosary beads
this is from a tibiotarsus of a chicken. what disease is this?
rickets, you can see the thickened growth plate and an unmodeled metaphysis on the left. the right is normal
what is osteomalacia?
soft bones, similar causes and pathogenesis to rickets but it occurs in adults instead of young/growing animals. the growth plate is not involved. involves defective mineralization during bone remodeling. the bones will have reduced resistance to pressure and tension
what are some gross lesions of osteomalacia?
expansion of the marrow cavity, thin spongy soft cortex, pathologic fractures, bones overall will be soft
what is fibrous osteodystrophy? What is the pathogenesis?
replacement of bone by fibrous connective tissue (instead of replaced by more healthy bone)
pathogenesis: hyperparathyroidism–>elevated PTH–>increased osteoclastic activity and replacement by fibrous tissue–> soft malleable bones
what are the two causes fibrous osteodystrophy and how do they differ?
primary hyperparathyroidism: excessive PTH secreted by the parathyroid glands, more rare and often seen with parathyroid gland neoplasia
secondary hyperparathyroidism: a compensation for low serum calcium which increases amounts of PTH, more common than primary hyperparathyroidism
with fibrous osteodystrophy, bones will be ____
soft and often enlarged
what are the two kinds of secondary hyperparathyroidism
nutritional and renal
what are some causes of nutritional secondary hyperparathyroidism and how does this disease appear grossly?
caused by low calcium high phosphorus diets in young animals, affecting the skull bones
can appear as a “big headed” animal, bilateral enlargement of fascial bones and fascial swelling
what are some examples of diets low on calcium and high in phosphorus?
horses: cereal hay (oat straw), bran, grain
dogs and cats: all meat diets
nutritional secondary hyperparathyroidism will cause ______ and it is most common in what animals with what expection?
cause fibrous osteodystrophy
in young animals except in horses, can happen in adults, does not happen in cattle and sheep
what is this disease and what is a common result?
this is fibrous osteodystrophy caused by nutritional secondary hyperparathyroidism, you can see the maxillary bone replaced with fibrous tissue including around the teeth, and fibrous tissue is compressing the nasal cavity towards the septum. Common result is for teeth to fall out
renal secondary hyperparathyroidism is also known as _______ and what are the 3 associated lesions?
renal osteodystrophy
1. soft, malleablebones
2. soft pliable mandible (rubber jaw)
3. deformed mandible/maxilla and tooth loss
what disease is this?
renal osteodystrophy/rubber jaw
renal osteodystrophy is a combination of what two things? what is it associated with?
fibrous osteodystrophy and osteomalacia
associated with severe chronic renal disease, common in older dogs and cats
what is the pathogenesis of renal osteodystrophy?
renal disease, kidneys excrete less phosphate, leading to hyperphosphatemia, phosphate reacts with calcium and causes hypocalcemia in the blood, causes PTH to increase, leading to more bone resorption
renal disease also causes reduced renal vit D metabolism leading to reduced calcium absorption from the intestines
this dog has chronic renal disease. what is happening here?
renal osteodystrophy, the nasal septum and maxillary bones are undulating and soft, and there is loss of alveolar bone leading to floating teeth
What bone lesion is associated with starvation in young animalsand how does it occur?
growth arrest lines happen in young growing animals near the metaphysis or epiphysis and they happen because of the “pausing” or “stopping” of long bone growth during the time of starvation
define osteoperosis and list 3 potential causes
osteoporosis: reduced bone mass and density with associated pathological fractures
causes: calcium deficiency, starvation, physical disuse
What metabolic bone disease would develop from a vit D deficiency in a piglet? what about an adult animal?
rickets in piglet/young animal
osteomalacia in adults
what is the basic pathogenesis of fibrous osteodystrophy?
hyperparathyroidism, increased PTH, increased osteoclastic resorption and replacement of fibrous tissue, soft malleable bones
What type of diet is associated with nutritional osteodystrophy?
low calcium high phosphorus diets
dogs and cats: all meat diets
horses: cereal hay, bran, grain
what condition is associated with fibrous osteodystrophy in older dogs and cats
renal osteodystrophy/chronic renal failure
