L4: Bone, Joint, and Muscle Path (Dark) Flashcards
bone anatomy
osteon made up of osteocytes surrounding Haversian canal
chars. of intramembranous ossification
- flat bones
- no growth plates
- susceptible to fibrous osteodystrophy
- not affected by chondrodysplasia
- ossification center begins in the fibrous CT membrane
- osteoid is secreted into the fibrous membrane
- forms woven bone and periosteum
- final layer of compact bone
chars. of endochondral ossification
- long bones (arms, legs, ribs)
- requires growth plates
- predominantly increases length (not width)
- hyaline cartilage –> 1ary ossification center + periosteum –> 2ary ossification center –> medullary cavity –> compact bone, periosteum, spongy bone
physeal plate
where 2 ossification centers meet each other
zone of proliferation
chondrocytes proliferating
zone of hypertrophy
where chondrocytes get larger
growth plate fx requires:
angiogenesis
- needs adequately mineralized collagen/cartilage
- needs adequate blood vessel quality
what dz process affects columnar cartilage/provisional zone of calcification
Rickets
what dz process affects osteoid formation
Osteogenesis imperfecta
what dz process affects bone remodeling in compact bone
osteopetrosis
transverse fracture
straight across fracture
oblique fracture
fracture at an angle
zones across a growth plate**
- resting
- proliferating
- hypertrophic
- ossification
- trabecular cone
- if orderly developed cartilage gets disrupted, will have growth problems*
spiral fracture
looks oblique in 2 different views of the fracture
“greenstick” fracture
- incomplete fracture
- usually in younger dogs where you get fracture through one cortex but not another
- usually not displaced
comminution
multiple fragments present in fracture
mnemonic for fracture classification
O (open v. closed)
L (location)
D (degree - complete or incomplete)
A (articular extension)
C (comminution/pattern)
I (intrinsic bone quality)
D (displacement, angulation, rotation)
stages of fracture healing
1) hematoma
2) fibrocartilagenous callus
3) bony callus
4) remodeling
Salter fracture
- fracture through a growth plate
- can induce growth deformities
- classified by the fracture location
- 5 main types (“SALTR”) - see slide 17**
Type 1 “Straight” Salter fracture
fracture straight through growth plate
-5%
Type 2 “Above” Salter fracture
starts above then travels through growth plate
-75%
Type 3 “Lower” Salter fracture
starts below then travels through growth plate
-10%
Type 4 “Through” Salter fracture
starts above and passes vertically through growth plate to end below growth plate
-10%
Type 5 “cRush” Salter fracture
growth plate compressed
-uncommon
Craniomandibular osteopathy
- proliferation of bony tissue around jaw, mandible, and TMJ
- primarily in Westies and Scotties
- autosomal recessive
- starts at 3-7mo, stops at 11-13mo
Osteogenesis imperfecta
- defect in matrix synthesis (ie. type I collagen)
- char. by excessive bone fragility –> fractures
- usually short lifespan
- without effective collagen synthesis, can’t get effective osteogenesis
Osteopetrosis
- failure of bone remodeling
- increased bone density
- has “bone in bone” appearance
Chondrosyplasia
- composed of multiple syndromes
- achondroplasia (failure to generate cartilage)
- disproportionate dwarfism
- affects bones with growth plates the most
Osteoporosis
- bone loss - resorption > formation
- disuse, malnutrition, corticosteroids, etc.
- susceptible to pathologic fracture
- osteoclast activity exceeds osteoblast activity
- a concern in older humans
osteopenia
decreased numbers of thin trebeculae
-usually progresses to osteoporosis
scurvy***
- only in species lacking L-gulonolactone oxidase
- lack of vit. C–> dec. lysine and proline hydroxylation in collagen –> impaired collagen synthesis –> weakened vessel walls and physeal cartilage deformity –> periarticular hemorrhage and osteochodrodysplasia
Fibrous osteodystrophy
Primary or secondary hyperparathyroidism:
- primary: caused by functional parathyroid adenomas or parathyroid hyperplasia
- secondary: Ca:P imbalance in feed (too much P or too little Ca), or kidney disease
Rickets
- defect in endochondral ossification
- only in young animals (b/c problem at growth plates)
- def. in Vit. D or phosphorus
Hypertrophic osteopathy
- due primarily to intrathoracic space occupying mass
- periosteal proliferation
- joints NOT involved**
- etiology unclear
Hypertrophic OsteoDystrophy (metaphyseal osteopathy)
- “Double physeal line”
- young dogs
- acute inflammation in the primary spongiosa
- necrosis of osteoblasts
- usually self-limiting
Eosinophilic Panosteitis
- happens around nutrient foramen
- patchy increased radiodensity in marrow cavity
Legg-Perthes Disease
- avascular necrosis of the femoral head
- small breed dogs
- occurs prior to physeal closure (4-11mo)
Osteomyelitis***
- SERIOUS condition
- causes: sx, penetrating wound, fracture, hematogenous spread
- tx difficult
- can be acute or chronic
- can be caused by many species of bacteria
- commonly centered around physes because bacteria get caught in blood supply here**
- main causes: Bordetella bronchiseptica and/or Pasteurella multocida**
malignant tumor of lymphocytes
lymphosarcoma
malignant tumor of macrophages
histiocytic sarcoma
malignant tumor of endothelial cells
hemangioma
benign tumor of fibroblasts
fibroma
malignant tumor of fibroblasts
fibrosarcoma
tumor of plasma cells
multiple myeloma
- common in bones
- can produce Bence-Jones protein in urine
2 big things to remember about osteosarcoma
- away from elbow, towards knee (except for horses, which can get it on mandible)
- pathologic fractures very common
- does NOT bridge joints
benign tumor of osteocytes
osteoma
malignant tumor of osteocytes
osteosarcoma
benign tumor of chondrocytes
chondroma
malignant tumor of chondrocytes
chondrosarcoma
osteochondromatosis
a condition involving a proliferation of osteochondromas
- benign
- proliferation of growth plate cartilage
- grow with skeleton
- tend to see around ribs and costochondral jxs
- don’t typically cause problems but if occurs in spinal cord can cause compressive damage
multilobular tumor of bone
forms stripey pattern on flat bone
2 ways synovium reacts to injury
1) hypertrophy (very common)
2) pannus (granulation tissue on articular surface)
- can damage underlying cartilage**
- can progress to ankylosis (pathologic fusion of joint)
arthrodesis*
ELECTIVE fusion of the joint
cartilage has poor blood supply and limited regenerative capacity
:)
Fibrillation
- forms vertical clefts in cartilage
- dull, yellow-brown cartilage
- can be reversible
Eburnation
polishing of exposed subchondral (below the cartilage) bone
-bone effectively taking place of cartilage
Osteophytosis
osteophytes form around unstable joint such as with arthritis
“joint mice”
calcified bony piece of tissue that is free floating in the joint
Inflammatory Arthritis
Caused by acute (penetrating wound, septicemia) or Chronic (immune-mediated, virus, untreated acute arthritis) arthritis
-pus in joint common CS
Sharpei fever
immune-mediated inflammatory arthritis in Sharpeis.
- cyclic high fever, inflammatory arthritis, then goes away
- most develop amyloidosis from repeated arthrosis
Osteoarthritis
- DJD
- decreased proteoglycan synthesis
- inc. metalloenzyme synthesis degrades proteoglycans
- typically an aging lesion
- lesions: fibrillation, cartilage erosion, osteophytosis, eburnation, synovial hyperplasia
Osteochondritis Dissecans (OCD)
- osteochondrosis: area of damage to the cartilage; tends to be thicker and has problems in underlying blood supply
- OCD when flap separates from underlying bone (joint mouse when brakes off)
- more common in horse, dog, pig
- usually in younger animals
most common neoplasm of joints*
synovial cell sarcoma
-looks similar to osteosarc, but involves joint
disc structure
outer annulus fibrosis
inner nucleus pulposus
IVDD
- annulus fibrosis cracks, tears, or can rupture
- releases nucleus pulposus
- Type I: sudden; more common in chondrodystrophic breeds
- Type II: gradual (tends to be in larger dogs)
- CS: ataxia, painful, placing and CP deficits, dec. motors
Wobblers
- stenosis (narrowing) of vertebral column
- rule-out for IVDD
- tends to be in younger animals
- more common in horses, large breed dogs
- tends to be dynamic (ie. gets worse or better with certain motion)
Dural ossification
- “ossifying pachymeningitis” - inflamm. of the dura mater
- generally incidental
- few have neuro signs
Hip Dysplasia
- degenerative, non-inflammatory
- generally large-breed dogs
- deformation of the joint: subluxation of the femoral head
- osteophytes and fibrous CT form. to stabilize joint
- genetic component
Elbow Dysplasia
- degenerative, non-inflamm.
- usually large breeds (esp. GSD)
- ununited anconeal process
- fragmented medial coronoid process
- OCD of elbow
chars. of normal muscle
- myofibers - single muscle cells
- peripheral nuclei
- striations
- high blood supply
2 fiber types
Type I: -slow twitch -large number of mitochondria -postural and sustained activity Type II: -fast twitch -fewer mitochondria -rapid activity
2 distributions of muscle injuries***
focal, multifocal
2 timelines of m. injuries***
monophasic (all m. stages in the same state of damage/repair)
polyphasic (ie. chronic toxin exposure)
heart attack (or other vascular injury) would be classified as:***
focal, monophasic
Responses to injury
hypertrophy atrophy degeneration necrosis - calcification regeneration fibrosis
types of muscle damage
circulation myositis congenital extertional myopathies nutritional myopathies toxins neoplasia denervation
m. damage: circulation
-if lot of weight put on muscle such as in Downer cattle or equine anesthesia, will compress blood vessels –> myonecrosis
m. damage: myositis
Bacterial:
-typically clostridium
-abscesses
Parasitic:
-Toxoplasma, Trichinella (pigs), Sarcocystis (horses)
Autoimmune:
-systemic lupus erythematosus, polymyositis, purpura hemorrhagica, etc.
Congenital Myopathies
- malignant hyperthermia
- muscular dystrophy
- equine rhabdomyolysis
- hyperkalemic periodic paralysis (HYPP)
- fainting goats
- “spayleg”
chars. of Equine Rhabdomyolysis
- congenital myopathy
- sporadic
- polysaccharide storage myopathy
- recurrent exertional rhabdomylolysis (a breakdown of muscle tissue that releases a damaging protein into the blood)
spayleg
- congenital myopathy in pigs
- back leg muscles aren’t strong enough to support their weight so they sink down and splay out
Exertional Myopathies
- capture myopathy: usually lethal and stress has been identified as the single most determining factor, exacerbated by muscle exertion
- disuse (ie. cast)
Nutritional Myopathies
- malnutrition –> atrophy
- vit. E/selenium deficiency –> white m. disease
m. damage: toxins
Monensin
-horses more sensitive than cattle
m. damage: neoplasia
Rhabdomyoma (benign)
Rhabdomyosarcoma (malignant)
m. damage: denervation
- brachial plexus avulsion –> will get severe m. atrophy, phantom itches
- laryngeal hemiplegia
