Pathology of Bone Flashcards
What are 3 major roles of bones?
- mechanical support
- protect key organs from traumatic injury
- maintain calcium homeostasis
How are most bones form? Bones found in the skull?
endochondral ossification
intramembranous ossification
Bone structure:
What are other names for Chondrodysplasia/Chondrodystrophy? What is it? What bones are affected?
Chondrodysplasia fetalis or disproportionate dwarfism
breed-associated condition where membranous appositional growth (horizontal) is normal in the bone, but interstitial growth (vertical) of cartilage is abnormal, resulting in premature closure of growth plates and a decrease in the length of long bones
those formed by endochondral ossification
What breed of cattle are most affected by chondrodysplasia? What phenotype results in the most severe form of bovine chrondrodysplasia?
Beef breeds, especially Dexter cattle
homozygote animals for the Dexter phenotype (Dexter “bulldog type” dwarfism) are severely deformed and typically aborted before 7 months of gestation
Dexter bulldog:
tongue seems long because parts of the mandible are derived from endochondral ossification - disproportionate dwarfism - large head with short muzzle - large abdominal hernia
What 5 breeds of dogs exhibit localized chondrodysplasias?
Dachshund and Basset hounds have micromelic achondroplasia
Pugs, Bulldogs, and Boxers exhibit brachycephalic achondroplasia
What is Wobbler’s Syndrome? What are the 2 forms? In what animals is it most common in?
Cervico-Vertebral Stenotic Myelopathy, a localized skeletal dysplasia and degenerative joint disease resulting in compression of the spinal cord
- dynamic: compression of spinal cord occurs no matter the position of the neck
- static: compression of spinal cord occurs when the neck is flexed
horses and large breed dogs, like Great Danes and Doberman Pinschers
Wobbler’s syndrome, spinal cord:
“ski-slope lesion”
- compression causes ataxia and incoordination
Wobbler’s syndrome, neck flexion:
What is Osteopetrosis?
inherited autosomal recessive disease caused by a lack of osteoclasts or by osteoclast failure to reabsorb the primary spongiosa, resulting in an increased bone density and lack of medullary spaces that would hold bone marrow
What is another name for osteopetrosis? What does it tend to cause?
metaphyseal dysplasia
- aplastic anemia, since there is no space for the hematopoietic tissues of the bone marrow to grow
- susceptibility to bone fracture, since the bone is much thicker and less flexible
What does osteopetrosis look like of a radiograph?
much larger and thicker bones that are more radiopaque than usual
(L)
What is congenital cortical hyperostosis? How does this affect fetuses?
autosomal recessive inherited condition in pigs where limbs (primarily the forelimbs) appear swollen due to excessive deposition of radiating trabeculae on the periosteal surface and lymphatic circulation is blocked
born dead or die within hours
What has congenital cortical hyperostosis been compared to in children and young monkeys?
Caffey’s disease - infantile cortical hyperostosis
Congenital cortical hyperostosis:
What is amelia? Hemimelia? Polymelia? Phocomelia? Micromelia?
AMELIA - absence of a limb(s)
HEMIMELIA - absence of the distal half of a limb
POLYMELIA - presence of additional limb(s)
PHOCOMELIA - severe shortening of the long bones of the limbs
MICROMELIA - abnormally small or short limb(s)
What was associated with children born with phocomelia in the 50’s and early 60’s?
pregnant women taking thalidomide (sedative), causing their babies to be born with feet and/or hands close to their trunk, resembling seal flippers
What is syndactyly? Polydactyly?
SYNDACTYLY: fusion of the digits
POLYDACTYLY: presence of extra digits
What are 4 common malformation of the vertebrae? What typically causes them?
- lordosis: ventral deviation of the vertebral column
- kyphosis: dorsal deviation of the vertebral column
- scoliosis: lateral deviation of the vertebral column
4 kyphoscoliosis: dorso-lateral deviation of the vertebral column
a malformed triangular “hemi” vertebrae
Scoliosis, kyphosis, lordosis
Lordosis, horse:
typically causes lameness and degenerative joint disease
Hemivertebrae:
congenital
In what aged animals are angular limb deformities common? What is the origin commonly traced back to? What are the 2 types?
younger animals, especially foals
an asymmetric lesion in the active growth plate
- valgus deformity: twisting of the bone with a lateral (outer) deviation
- varus deformity: twisting of the bone with a medial (inward) deviation
What are 6 possible causes of angular limb deformities?
- malposition in utero
- (congenital) hypothyroidism
- joint laxity
- trauma (ischemia, reduced blood supply)
- malnutrition
- impaired endochondral ossification
Horse, varus vs. valgus deformities:
What are metabolic bone diseases also referred to as? What are they a result of?
osteodystrophies
disturbed bone growth, modeling, or remodeling due to either nutritional or hormonal imbalance
What are the main characteristics of metabolic bone diseases?
failure of production of the bone matrix, its mineralization, or its maintenance
What are the 4 possible etiologies of metabolic bone disease?
- NUTRITIONAL: vitamins C and D, Ca, P, or protein deficiencies
- HORMONAL: (hyper)parathyroid (PTH), gonadal (estrogens), or adrenal (corticosteroids) problems
- DISUSE: physical inactivity
- TOXIC: lead and fluoride poisoning, hypervitaminosis A
What is osteoporosis? What is seen grossly?
a type of metabolic bone disease characterized by osteopenia, where there is a lower amount of bone tissue, but the bone present is normal
reduction in the thickness of the cortical bone and a decrease in the number of trabeculae in the cancellous bone
What are the 3 common etiologies of osteoporosis?
- NUTRITIONAL: starvation, Cu deficiency, vitamin C deficiency
- AGING: peak in bone mass at a certain point, where resorption will eventually outpace bone formation
- DISUSE
Osteoporosis:
thin cortical bone
decreased trabeculae in cancellous bone
Osteoporotic compression fracture:
decreased trabeculae lead to the increased fragility in vertebrae, leading to a smaller vertebra and greater likelihood of fracture
Osteoporosis:
What is Rickets? What is the basic pathogenesis?
metabolic bone disease typically affecting young growing animals
defective calcification of osteoid and defective endocondral ossification, causing the abnormal mineralization of cartilage matrix
vitamin D, Ca, or P deficiency
Other than nutrition, what is another necessity to avoid Rickets?
sunlight —> solar UV radiation helps produce vitamin D
What are 5 common gross lesions associated with Rickets?
- irregular thickening of growth plates with tongues of uncalcified cartilage extending into the metaphysis
- widening of growth plates causing enlarged ends of long bones, enlargement of costochondral junctions (rachitic rosary), and bowing on weight-bearing long bones
- hemorrhages beneath the articular cartilage or in growth plates
- pathological fractures
- bending of ribs rather than snapping at necropsy
Why is Rickets historically significant?
first “air pollution disease,” where the Industrial Revolution filled cities with smog, depriving children of sunlight and causing a mass development in Rickets
Rickets, rachiatic rosary:
enlarged costochondral junctions at the ribs
Rickets:
varus deformity
Foal, rachitic rosary:
Osteodystrophic lines, Rickets:
“growth-arrest” lines
- indicative of malnutrition
- cartilage production is interrupted, causing a line where it stopped and started again
What is osteomalacia? What is its pathogenesis?
metabolic bone disease of grown animals with closed growth plates
failure in the mineralization of osteoid primarily due to vitamin D or P deficiency —> unmineralized osteoid is resistant to osteoclastic resorption and accumulated in the bone
What are 4 common signs of osteomalacia?
- bone pain causing shifting lameness
- pathological fractures
- deformities, like kyphosis, lordosis, and scoliosis
- collapse of articular surfaces (connections between bones, ossicles, or other hard structures in the body)
What is fibrous osteodystrophy? What is it a result of? In which animals is it most common?
metabolic bone disease characterized by extensive bone resorption and replacement by fibrous connective tissue and poorly mineralized, immature bone
persistent elevations of plasma PTH levels caused by hyperparathyroidism; low Ca and high P levels = high PTH levels
horses, pigs, dogs, cats
- less commonly seen in reptiles and New World Monkeys
What is associated with primary hyperparathyroidism causing fibrous osteodystrophy?
usually associated with functional adrenal parathyroid adenomas where affected animals exhibit marked hypercalcemia and hypophosphatemia
What are 3 common lesions in fibrous osteodystrophy caused by primary hyperparathyroidism?
- thyroid C-cell hyperplasia —> continuous secretion of calcitonin, decreasing calcium
- hypercalcemic nephropathy (nephrocalcinosis)
- metastatic mineralization of soft tissues
Fibrous osteodystrophy, horse:
loss of bone and replacement by fibrous connective tissue
“brain disease,” “big head”
- head appears swollen
What are the 2 types of secondary hyperparathyroidism that can cause fibrous osterodystrophy?
- NUTRITIONAL: dietary deficiency of Ca, excess dietary P, or vitamin D deficiency; a result of low Ca or high P in the diet and tends to affect young, growing animals
- RENAL: P retention due to loss of glomerular function and the inadequate synthesis of 1,25-dihydroxyvitamin D (calcitriol)
Renal fibrous osteodystrophy most commonly occurs in what animals? What are 3 common presentations?
dogs
- bones (esp those in the head) become swollen and are firm, rather than hard (usually affects maxilla and mandible)
- mandible becomes quite pliable
- teeth are often mobile and malpositioned due to swollen gums and alveolar bone
Renal fibrous osteodystrophy, dog:
Renal fibrous osteodystrophy, “Rubber jaw”:
Renal fibrous osteodystrophy, gums:
swollen!
Renal fibrous dystrophy:
