Test 3- Bone Flashcards
In addition to provide mechanical support and protecting key organs from traumatic injury bone plays an important role
In addition to provide mechanical support and protecting key organs from traumatic injury bone plays an important role in Ca homeostasis.
“Bones are
Bones are dynamic organs undergoing constant remodeling throughout life”
Are Diseases of bone diganosed a lot?
Diseases of bone are often under-diagnosed
Bone is a specialized
Bone is a specialized connective tissue consisting of cells embedded within a gel-like substance that becomes mineralized
Bone has the property of
Bone has the property of marked rigidity and strength whilst retaining some degree of elasticity
To accommodate changes related to mechanical stresses and demands on calcium homeostasis bones are
To accommodate changes related to mechanical stresses and demands on calcium homeostasis bones are in a dynamic state of growth and resorption throughout life.
Like other types of connective tissue bone is composed of
Like other types of connective tissue bone is composed of cells and an organic extracellular matrix containing primarily glycoproteins and collagen fibersthis matrix is known as osteoid. Osteoid rapidly undergoes mineralization (by deposition of inorganic salts, mainly calcium hydroapatite (CHAP) crystals, to form bone.
The bone matrix also contains a variety of
The bone matrix also contains a variety of growth factors which probably play an important role in bone development, modeling and remodeling.
Cellular elements of bone
• Osteoblasts- produce osteoid, immature cells of bone
- Osteocytes- mature cells of bone
- Lining cells (inactive osteoblasts)
• Osteoclasts- multinucleated cells that reabsorb bone- maintain Ca + metabolism
pinkish- osteoid
large mulitnucleated cells- osteoclasts that liberate ca into the blood
There are two types of bone based on the degree of maturity…
- Woven bone: Immature bone present during fetal development and in the early stages of bone repair. Collagen fibers in woven bone are randomly arranged adopting a crisscross (woven) pattern microscopically.
- Lamellar bone: Mature bone. Collagen fibers are arranged in a parallel pattern.
according to the stage of maturation bone(cortical or canellous) could be either woven or lamelluar
During fetal life bone formation occurs in 2 ways, both of which involve replacement of connective tissue by bone:
- Intramembranous ossification – Occurs within “membranes” of condensed primitive mesenchymal tissue flat bones of the skull ONLY
- Endochondral ossification – Occurs in the majority of bones of the skeleton (limbs, vertebral column, pelvis, base of the skull). Bone develops from a cartilaginous model (hyaline cartilage) that is subsequently replaced by osseous tissue present in the so called ossification centers.
epiphyseal plates
Endochondral ossification occurs in the ossification centers of immature bones and in the growth plates (epiphyseal plates) of developing bones.
Once the growth plates are closed (mature animal),
Once the growth plates are closed (mature animal), no further longitudinal growth (resulting in increase length) can occur.
growth plate
Bottom- begining of mystephosis- spoongy bone
Top- resistin cartilage- chondro cysts are isolated
Proliferative(p) layer
Chondrodysplasia
Chondrodysplasia (Chondrodysplasia fetalis or disproportionate dwarfism)
Breed-associated, usually hereditary conditions that occur in dogs, cattle and sheep. 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).
Most common in beef breeds (Angus, Hereford). In Dexter cattle, homozygote animals for the Dexter phenotype (Dexter “bulldog” dwarfism) are severely deformed and are usually aborted before 7 months of gestation (lethal form of chondrodysplasia).
“Dexter bulldog
“Dexter bulldog” – Congenital lethal Chondrodysplasia
Inherited condition of Dexter cattle.
Affected calves are often aborted and exhibit disproportionate dwarfism,
short vertebral column, marked micromelia (shortening of the limbs),
large head with short muzzle, protruding
tongue and large abdominal hernia
Chondrodystrophic dog breeds exhibit
Chondrodystrophic dog breeds exhibit localized chondrodysplasias involving specific bones.
Daschumonds- Micromelic achondroplasia(very short limbs)
Other brachicephalic chondrodystrophic dog breeds are Bulldogs and Boxers
Basset hound
Cervico-vertebral stenotic myelopathy (Wobbler‟s syndrome)
- This a localized skeletal dysplasia most common in horses and large breed dog
- It can also be classified as a degenerative joint disease which affects the axial skeleton.
- The syndrome results in dynamic or static compression of the cervical spinal cord (SC) by abnormal cervical vertebrae.
- In the dynamic form sc compression occurs when the neck is flexed; in the static form sc compression occurs no matter what position the neck is in.
Wobbler’s in horses and large breed dogs
Cervical vertebral stenotic myelopathy
in Doberman
“ski-slope lesions”
Wobbler Syndrome, horse
static- severe compression of the cervical canal
Osteopetrosis
Osteopetrosis (petros: rock)
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.
Metaphyseal Dysplasia
Osteopetrosis is an heritable condition also known as “Metaphyseal Dysplasia” results in diffuse osteosclerosis (↑ bone density).
Since there is no space for the hematopoietic tissues of the bone marrow to grow, affected animals often present aplastic anemia. Affected bones have an increased susceptibility to fracture. Reported mainly in dogs, sheep, cattle and horses.
- Aplastic anemia
Osteopetrosis
Congential Cortical hyperostosis of pigs
Autosomal recessive inherited condition in pigs.
• Limbs (primarily the forelimbs) appear swollen due to excessive deposition of radiating trabeculae on the periostal surface, and blockage of the local lymphatic circulation.
Most affected pigs are born dead or die within hours- lame animals that can not stand
This abnormality has been compared to Caffey‟s disease (infantile cortical hyperostosis) observed in children and monkeys.
Localized malformations
Localized malformations
- Limbs (appendicular skeleton)
- Amelia: Absence of a limb(s|)
- Hemimelia: Absence of the distal half of a limb
- Polymelia: Supernumerary limbs
- Phocomelia: Abscense of the proximal portion(s) of a limb(s)
- Micromelia: Abnormally small or short limb(s)
- Syndactylia: Fusion of the digits
- Polydactylia: Supernumerary digits
- Others…
Amelia:
Absence of a limb(s|)
Hemimelia:
Absence of the distal half of a limb
Polymelia:
Supernumerary limbs
Phocomelia:
Abscense of the proximal portion(s) of a limb(s)
Micromelia:
Abnormally small or 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
Kyphoscoliosis:
Dorso-lateral deviation of the vertebral column
Dorsal deviation of the spinal column- kyphosis
Angular limb deformities
Angular limb deformities – Relatively common in young animals and specially important in horses. In many cases (not all) the origin of the deformity can be traced to an asymmetric lesion in an active growth plate. Characterized by twisting of the bone: lateral (outward) deviation (valgus deformity) or medial (inward deviation (varus deformity) of one or more limbs distal to the affected growth plate or joint. Present at birth or may develop later in life. Causes may include:
- Malposition in utero
- Joint laxity
- Hypothyroidism (congenital goiter)
- Trauma (ischemia or reduced blood supply) - Malnutrition
- Impaired endochondral ossification
Carpal Valgus, foal.
Metabolic Bone Diseases
• Also referred as osteodystrophies
Result from disturbed bone growth, modeling or remodeling due to either nutritional or hormonal imbalance.
MBD is characterized by failure of production of bone matrix, its mineralization or its maintenance.
Metabolic Bone Diseases Etiology
Nutritional: Vitamins C, D, Ca, P, Protein
Hormonal: Parathyroid (PTH), Thyroid (calcitonin),
gonads (estrogens), adrenal problems (corticosteroids).
Disuse: Physical inactivity
Toxic: Lead and fluoride poisoning, hypervitaminosis A etc.
Can metabolic bone diseases have more than one etiology?
In a particular individual metabolic bone diseases can have more than one etiology. In addition, different forms of metabolic bone disease (osteodystrophies) can coexist in the same individual.
In domestic animals metabolic bone disease caused by nutritional deficiency
In domestic animals metabolic bone disease caused by nutritional deficiency is often caused by deficiency of more than one nutrient.
Osteoporosis
Characterized by osteopenia (↓ in the amount of bone tissue). “ there is a ↓ amount of bone but the bone that is present is normal. Grossly there is a reduction in the thickness of the cortical bone and a ↓ number of trabeculae in the cancellous bone.
Osteoporosis Etiology
- Nutritional
* *Starvation(MOST COMMON)**, Cu deficiency, Vitamin C deficiency. - Aging
In humans peak bone mass occurs around the age of 30; there after resorption outpaces bone formation.
- Disuse
Goat, osteoporosis/ osteopenia – Cornell Serous atrophy of bone marrow -Starvation
From McGavin: Sheep Osteopenia/ osteoporosis
Heifer – starvation Serous atrophy of BM Fat, Cornell Files
osteoporosis- MIGHT BE, but it’s hard to diagnosis
Rickets
Metabolic bone disease of a complex etiology affecting young growing animals.
The basic pathogenesis involves defective calcification of osteoid and defective endochondral ossification.
Etiology is multifactorial but typically involves vitamin D or phosphorous deficiency.
• Exposure to sunlight (solar ultraviolet radiation is also important).
Gross Lesions in Rickets
o Irregular thickening of growth plates with tongues of uncalcified
cartilage extending into the metaphysis
o Widening of growth plates enlarged ends of long bones; enlargement of costochondral junctions (“rachitic rosary”); weight-bearing long bones may become bowed
o Hemorrhages beneath the articular cartilage or in growth plates o Pathological fractures may occur
o At necropsy ribs bend rather than snap
Rickets. Dog from India
Osteodystrophic (growth- arrest) lines –Rickets-Foal
Chicken: Rachitic rosary
Osteomalacia
A disease of grown (adult) animals (closed growth plates).
Similar pathogenesis to rickets: failure in the mineralization of
osteoid primarily due to vitamin D or P deficiency.
Unmineralized osteoid is resistant to osteoclastic resorption and accumulates in the bone.
Affected animals may exhibit bone pain (shifting lameness), pathologic fractures and deformities such as kyphosis, lordosis and scoliosis.
Collapse of articular surfaces may occur.
Fibrous Osteodystrophy
(osteodystrophia fibrosa; osteitis fibrosa cystica)
Relatively common metabolic bone disease characterized by extensive bone resorption and replacement by fibrous connective tissue and poorly mineralized immature bone.
- The disease is the result of persistent elevations of plasma PTH levels (hyperparathyroidism).
- More common in horses, pigs, dogs and cats. Also seen in reptiles and New World Monkeys.
Fibrous Osteodystrophy Mechanism:
Primary Hyperparathyroidism-
Fibrous Osteodystrophy (Basic mechanism: ↓Ca; ↑P= ↑PTH)
Due to primary or secondary hyperparathyroidism.
Primary Hyperparathyroidism:
- Usually associated with functional parathyroid adenomas in dogs.
- Affected animals exhibit marked hypercalcemia and hypophosphatemia.
- Lesions may include FO; Thyroid C-cell hyperplasia; hypercalcemic nephropathy (nephrocalcinosis) and metastatic mineralization in soft tissues.
Secondary Hyperparathyroidism(MORE COMMON)
1. Nutritional: Dietary deficiency of Ca; excess dietary P, or deficiency of Vitamin D. In most cases nutritional secondary hyperparathyroidism is the result of ↓Ca or ↑ P in the diet and, with the exception of horses, affects young growing animals.
2. Renal: Complex etiology but P retention due to l_oss of glomerular function_ and the inadequate synthesis of 1, 25 Dihydroxyvitamin D (1,25, dihydroxy cholecalciferol, calcitriol) by the kidney play a mayor role.
Renal osteodystrophy occurs more commonly in the dog. Bones, especially those of the head become swollen and are firm rather than hard, maxilla and mandible are usually affected. The mandibles may become quite pliable (“rubber jaw”). Teeth are often mobile and malpositioned within the swollen gums and alveolar bone.
Fibrous osteodystrophy, Horse. Loss of bone and replacement by fibrous connective tissue.
“Bran disease or Big head”
“Rubber jaw” – Renal Osteodystrophy, dog Cornell files.
Fibrous osteodystrophy
teeth become burried
Shih-Tzu, Renal osteodystrophy, Cornell files.
fibrous osteodystrophy
teeth are embedded in the proliferative tissue
Foal, focal osteomyelitis with sequestrum(toward the bottom of the picture). Cornell Files
in a young animal
sequestrum will result in the formation of a layer of granulation tissue and reactive bone know as an “involucrum”
Cornell, Pathologic fracture, Osteosarcoma, dog
VERY COMMON IN DOGS
Fracture Repair
Healed humeral fracture, feedlot steer, UCVM, OI
Complications associated with bone fractures
- Bone necrosis and formation of a sequestrum
- Nonunion fracture pseudoarthrosis (false joint) formation
- Osteomyelitis (compound fractures)
- Cachexia( wild animals)
Pig – vertebral abscess resulted in fracture of the vertebral body and focal compression of the spinal cord, common sequel of tail biting. AVC
can cause intendtion of the spinal cord
rib fractures are difficult
Blood vessel from the bone marrow come close to the growth plate and turn very softly
bacteria can colonize easier
Physitis has extended to the periosteum and metacarpal phalangeal joint, foal
osteomylitis- change in the color of the bone- have a rim of inflammation/congestion; in the area of the growth plate
Embolic osteomyelitis, foal. Note Area of bone necrosis (arrow).
lesions cloase to epiphysisal growth plate
sequestrium- necrosis and inflammation
bacteria that can cause this: E. coli, salmonella(espesically in foals),
Bovine Actinomycosis, “lumpy jaw”, UCVM
pyogranolomatous osteomylitis
Etiological agent- actinomyces bovis
engorgment of the mandible
Involvment of the mandbile and maybe maxilla
Chronic pyogranulomatous osteomyelitis – Actinomycosis
lesions in the mouth or a bad tooth- can be portal of entry
Pyogranulomatous Osteomyelitis, Actinomycosis
sulfur granules- characterisitized by large bacterial colonies surrounded by neutrophils and on outside- macrophages, lymphocytes
Splendore Hoeppli- eosinophilic filaments that surround the bacteria- represents the antigens/antibody complexes
Gram positive bacteria, Actinomyces bovis, UCVM, OI
MOSTLY BONE
“Lumpy Jaw” (Actinomycosis) – cow.
Actinomyces bovis. Note osteolysis of the macerated and bleached bone specimen- bone remodeling
Chronic pyogranulomatous Osteomyelitis
Nocardia spp. was identified by culture and PCR
Hypertrophic pulmonary osteoarthropathy or osteopathy is also occasionally observed.
In young dogs with rhabdomyosarcomas(skeletal muscle malignant tumors) of the urinary bladder and mares with ovarian tumors.
bone proliferation along the periosteium
Canine craniomandibular osteopathy (“Lion Jaw”)
West Highland White Terrier
Osteoma, maxilla, Sheep-McGavin
we don’t see a lot of primary bone tumors in LA
In the dog osteosarcoma has
a relatively specific site predilection:
In the dog osteosarcoma has
a relatively specific site predilection:
“Close to the knee and away from the elbow”
Osteosarcoma, 11 y- Female Rottweiller,
poor prognosis
Osteosarcoma, 2 year-old Poodle, Atlantic Veterinary College
stifle joint
Chondrosarcoma, skull, dog -McGavin
Example of chondrosarcoma in a long bone- humerus of a mastiff
Chondrosarcoma, rib, cat, McGavin
Chondrosarcoma, humerus
Chondrosarcoma, humerus
Joint reaction to injury
Most common joint lesions in domestic animals involve synovial (diarthrodial) joints
• Injury to articular cartilage results in erosion/fibrillation(fraying- loss of cartilage and extracellular matrix), eburnation( all of the articular cartilage is gone!- exposure of the subchronal bone and has a shiny apperance) or “Joint mice” formation
On left- normal
on right- abnormal
left center- erosion of the bone
right/right center- complete loss of articular cartilage
Osteophyte formation(lumps) may be a sequel of chronic joint injury- this will help with formation of new bone(bone spurs)
articular cartilage looks granular, it’s discolored. There is erosion here
Villous hypertrophy/ hyperplasia of the synovial membrane is other manifestation of chronic joint injury
femoral head- loss of articular cartilage; exposure of subchondral bone- characterized by erosion of bone
Pannus formation
OCD lesions in dogs. SHOULDER COMMONLY AFFECTEDHumeral head
OCD lesions in dogs. Humeral head
deformaty in the bone
Stifle joint in a horse
areas of ulceration
humerus of a pig OCD or osteochondritis dissencants
OCD lesion, distal femur, lateral ridge, horse
erosion and ulceration with exposure of the underlying subchondrol bone
OCD lesion, distal femur, lateral ridge, horse, UCVM – 2009
Note abnormal growth of the articular cartilage and subchondral bone resulting in deformation of the trocheal groove and ridges, OI.
Osteochondrosis, Pig, femoral head
normal femoral head, pig
Osteochondrosis dissenticans, pigs, UCVM, OI
Femur (femoral head) –Dog with hip Dysplasia
subchondral bone is gone
DJD –Hip Joint, Aged German Shepherd
erosion of the articular cartilage
Hansen’s type I (B) - DASHSUNDS- Disk Extrusion
type II (A)- MORE COMMON IN NON- CHRONDODYSTROPIC DISEASES- Protrusion- associated with aging
IDD - Dog-
Hanesne’s Type II- as seen in older dogs
Spondylosis deformans, 20 year-old donkey, TAMU
Ankylosing spondylosis – aged bull, Cornell Show and Tell, Dr. King Macerated and bleached bone specimen.
Osteophytes (“bone spurs”).
31 year-old gelding In thin body condition
(395 kg). Loosing weight.
In addition to swayback this horse had severe degenerative joint disease. Poor tail tone and mild proprioceptive deficits in the hind limbs were noticed on examination
Lumbar segment of vertebral colon, Intervertebral disk disease (IDD) Leading to sub-luxation of L3-L4; formation of oseteophytes
spondylosis
Close up of the lesions in the medial condyle of the right humerus
lordosis(ventral deviation of the spinal column)
Common in horses used in rodeo events or Polo chronic trauma. The result of abrupt stops, turns and twists
Ring bone
Inflammatory Joint Disease
Osteomylitis
Route of Infection:
Most common in farm animals, specially the young where its a common sequel to neonatal bacteremia Non-infectious arthritis occur most often in dogs and
cats and have an immune- mediated etiology.
