Bone Pathology Flashcards
What are the cellular elements found in bone?
- Osteoblasts - produce EXC that will become mineralized; younger bone cells; trapped within the Osteoid and become…
- Osteocytes - mature bone cells
- Lining Cells (inactive osteoblasts) - simple squamous epithelium-like; when they become active, they get more “plump” or bigger
- Osteoclasts - multi-nucleated, large cells that reabsorb bone; maintenance of Ca2+ metabolism
Based on the degree of maturity, there are 2 types of bone. What are the 2 types?
- Woven Bone - Immature bone; present during fetal development and in early stages of bone repair
- Lamellar Bone - Mature bone; collagen fibers are arranged in a parallel pattern
Bone formation occurs in 2 ways, both of which involve replacement of Connective Tissue by bone. What are the 2 ways?
- Intramembranous Ossification - occurs within the membranes of condensed primitive mesenchymal tissue –> flat bones of the skull
- Endochondral Ossification - majority of bones in the skeleton; bone develops from a cartilaginous model (hyaline cartilage) that is replaced by osseous tissue
Where does endochondral ossification occur?
The ossification centers of immature bones and in the growth plates (epiphyseal plates) of developing bones.
Longitudinal growth no longer occurs once the growth plates are closed (mature animals). What type of growth is longitudinal growth?
Longitudinal Growth results in an increase in LENGTH.
Growth plates are the site of LONGITUDINAL GROWTH.
Chondrodysplasia is AKA…
Chondrodystrophy, Chondrodysplasia Fetalis or Disproportionate Dwarfism
T/F - Chondrodystrophy is breed-associated, usually hereditary in dogs, cattle and sheep.
True.
What happens in the Anomaly Chondrodysplasia?
Membranous appositional growth is normal but interstitial growth of cartilage is abnormal resulting in premature close of growth plates and decrease length of long bones (affects bones that form by endochondral ossification).
What breeds are more susceptible to chondrodysplasia?
Angus, Hereford cattle
Dexter cattle - Dexter “bulldog” dwarfism
Dexter “Bulldog” is an inherited condition of Dexter cattle. Affected calves are often (fill in blank) and exhibit disproportionate (fill in blank).
Dexter “Bulldog” is an inherited condition of Dexter cattle. Affected calves are often (aborted) and exhibit disproportionate (dwarfism).
What are the CS of Dexter “bulldog”?
Prominent tongue, short vertebral column, marked micromelia - shortening of the limbs
large head with short muzzle
large abdominal hernia
Dachshunds have what type of chondrodysplasia? These breeds exhibit localized chondrodysplasia involving specific bones,
Micromelic achondrodysplasia - short limbs! This is a normal feature in Dachshunds, Bassets, and Corgis. - They are genetically selected to present this!
Brachiocephalic breeds, like PUGS, have what type of chondrodystrophy?
Brachicephalic chondrodysplasia
Bulldogs and Boxers are other breeds with this!
What is Wobbler’s Syndrome?
Cervico-vertebral stenotic myelopathy (degeneration of the spinal cord).
This a localized skeletal dysplasia most common in horses and large breed dogs.
Degenerative joint disease affecting the axial skeleton.
Wobbler’s Syndrome results in what type of compression of the cervical spinal cord?
Dynamic or Static Compression of the Spinal Cord by abnormal cervical vertebrae.
In the Dynamic Form of Wobbler’s Syndrome, spinal cord compression occurs when the neck is…
FLEXED
In the Static Form of Wobbler’s Syndrome, spinal cord compression occurs when the neck is…
Compression occurs no matter what the position of the neck is.
MORE SEVERE FORM!
Osteopetrosis is…
Inherited disease caused by osteoclast failure to reabsorb the primary spongiosa. This failure results in an increased bone density and lack of medullary (bone marrow) spaces.
Osteopetrosis is AKA…
Metaphyseal Dysplasia - results in diffuse osteosclerosis (increased bone density)
Osteopetrosis often presents with…
aplastic anemia - there is no space for the hematopoietic tissues of the bone marrow to grow
Osteopetrosis affected bones are more susceptible to….
Increased susceptibility to fracture.
What is a congenital anomaly in Pigs?
Congenital cortical hyperostosis
Congenital cortical hyperostosis in pigs is what type of condition?
Autosomal recessive inherited condition.
What are the CS of Congenital cortical hyperostosis in pigs?
Forelimbs appear swollen due to excessive deposition of radiating trabecular on the periosteal surface, and blockage of the local lymphatic circulation.
Most pigs are born dead or die within hours.
Congenital cortical hyperostosis in pigs is compared to what disease in children and monkeys?
Caffey’s disease - infantile cortical hyperostosis
What is Amelia?
absence of limb(s)
Hemimelia?
Absence of the distal half of a limb
Polyemia?
Supernumerary limbs
Phocomelia?
Absence of the proximal portion(s) of a limb(s)
Micromelia?
Abnormally small/short limb(s)
Syndactylia?
Fusion of the digits
Polydactylia?
Supernumerary digits
Lordosis?
Ventral deviation of the vertebral column
Kyphosis?
Dorsal deviation of the vertebral column
Scoliosis?
Lateral deviation of the vertebral column - common in humans
Kyphoscoliosis?
Dorso-lateral deviation of the vertebral column
Angular limb deformities are relatively common in (fill in blank) and specially important in (fill in blank).
Angular limb deformities are relatively common in young animals and specially important in horses.
The origin of an angular limb deformity can be traced to an…
asymmetric lesion in an active growth plate
Define Valgus Deformity…
twisting of the bone: lateral (outward) deviation
Define Varus Deformity…
twisting of the bone: medial (inward) deviation
Metabolic Bone Diseases are AKA…
Osteodystrophies
Osteodystrophies result from…
disturbed bone growth, modeling or remodeling due to either nutritional or hormonal imbalance
Metabolic Bone Disease is characterized by…
failure of production of bone matrix, its mineralization or its maintenance
(4) Metabolic Bone Disease Etiologies:
Nutritional - Vits C, D, Ca, P, Protein
Hormonal - PTH, Calcitonin, estrogens, corticosteroids
Disuse - physical inactivity
Toxic - lead and fluoride poisoning
Metabolic Bone Diseases are traditionally classifies as…
osteoporosis, rickets, osteomalacia and fibrous osteodystrophy
Osteoporosis is characterized by…
osteopenia (decrease in the amount of bone tissue) but the present bone is normal
grossly - reduced thickness of cortical bone and a decreased number of trabecular in the cancellous bone
Etiology of Osteoporosis…
Nutritional - Starvation, Cu def., Vit C def.
Aging - resorption outpaces bone formation at a certain age (age 30 for humans - reach peak bone mass)
Disuse
In animals, MOST of the forms of osteoporosis that we will see are suffering from which etiology?
Nutritional
What is Rickets?
Rickets - a metabolic bone disease of a complex etiology affecting young growing animals.
What is the basic Pathogenesis involved in Rickets?
Involves defective calcification of osteoid and defective endochondral ossification (defective mineralization of cartilage matrix)
What is the etiology of Rickets?
Etiology is multifactorial but typically involves Vit D or Phosphorous Def.
Gross Lesions of Rickets include:
Irregular thickening of growth plates with tongues of uncalcified cartilage extending into metaphysis
widening of growth plates -> enlarged ends of long bones
enlarged costochondral junctions “rachitic rosary”
weight-bearing long bones may bow
hemorrhage beneath articular cartilage or in growth plates
pathological fractures
at necropsy, ribs bend instead of snapping
The First “Air Pollution Disease” is…
Rickets
Smog-filled cities deprived children of sunlight.
What is the best prevention and treatment of Rickets?
Sunlight
What are the CS of Rickets?
bony necklace, curved bones, big joints, and bowed legs
Osteomalacia is…
a disease of grown (adult) animals - closed growth plates
similar pathogenesis to rickets; failure in the mineralization of osteoid primarily due to Vit D or P def.
unmineralized osteoid is resistant to osteoclastic resorption and accumulates in the bone
Animals affected with Osteomalacia are usually painful -shifting lameness - and path. fractures. What deformities would this animal have?
kyphosis, lordosis, and scoliosis
Fibrous Osteodystrophy is AKA…
osteodystrophia fibrosa; osteitis fibrosa cystica
What are the characteristics of Osteodystrophy?
extensive bone resorption and replacement by fibrous connective tissue and poorly mineralized immature (woven) bone
Osteodystrophy is the result of…
persistent elevations of plasma PTH levels - hyperparathyroidism
What animals are we more likely to see Osteodystrophy in?
Horses, Pigs, Dogs and Cats
Reptiles and New World Monkeys
T/F: Fibrous Osteodystrophy can be due to Primary and Secondary Hyperparathyroidism.
True
Secondary Hyperparathyroidism is the more common cause of Osteodystrophy. What are the 2 forms of Secondary Hyperparathyroidism?
- Nutritional
2. Renal
“Big Head”/”Bran Disease” are common names for what disease in horses?
Fibrous Osteodystrophy in Horses.
-loss of bone and replacement by fibrous connective tissue
What triggers “Big Head”/”Bran Disease” in Horses?
an increased amount of Phosphorous in the diet - animals develop hyperphosphortemia - altering the normal Ca/Phos ratio (Very important!) –> increased Phos stimulates an increase in PTH –> stimulates osteoclastic reabsorption of bone
This is also seen in animals that are fed a strict, meat-only diet.
Describe Fluoride toxicosis…
Occurs in herbivores mainly cattle and sheep. Affects the normal metabolism of bone and teeth primarily in growing animals. Ameloblasts and odontoblasts are markedly sensitive to excess fluoride and the result are soft dark-brown discolored teeth that wear down easily (defective enamel and dentine - odontodystrophy). Bones exhibit periosteal hyperostosis.
Fluroride toxicosis is seen primarily in…and effects the…
Cattle…Teeth/Bone
**young animals with worn down teeth
Describe lead poisoning…
Lead interferes with osteoclastic activity. Subtle bone lesionsIncrease bone density (osteosclerosis) in the metaphysis“lead line”
Hypervitaminosis A in cats is…
The most well know syndrome is observed in cats that consume high quantities of bovine livers (high vitamin A content) for a long period of time deforming cervical spondylosis. The disease is more common in Australia and Uruguay. Affected cats develop osteophyte formation around the joints of the cervical vertebrae, shoulder and elbow. (also known as cervical ankylosing spondylosis or disseminating ankylosing osteoarthropathy).
What do the outcomes of Osteonecrosis depend on?
Depends on size of lesion and strength of collateral circulation - influences repair/healing.q
What is a sequestrum?
A piece of isolated, necrotic bone from the remaining viable bone
-can be a complication of osteonecrosis
Attempts to wall off a sequestrum will result in the formation of…
a layer of granulation tissue and reactive bone known as an “Involucrum”
Bone fractures can be classified as (7)…
Traumatic - normal bone broken by excessive force
Pathologic - abnormal bone broken by min. trauma or normal wt. bearing
Complete/Incomplete
Closed(simple)/Open(compound)
Comminuted - a fracture resulting in multiple bone fragments
Avulsed -caused by the pull of a ligament/muscle tendon at its insertion into bone
Microfracture/Infraction - fracturing of trabeculae w/out external deformation of cortical bone
