Bone Pathology Flashcards
Malignant Neoplasms of Joints
Arise from the synovial membrane
Uncommon in dogs and very rare in other species
Pannus formation is a possible sequel of
Chronic joint injury
Lordosis
Ventral deviation of the vertebral column
Etiology of osteoporosis
Nutritional
Aging
Disuse
Amelia
Absence of limbs
Degree of osteonecrosis is influenced by
Influenced by size and extent of necrosis and extent and strength of collateral circulation and local repair mechanism
Causes of angular limb deformities
Malposition in utero
Joint laxity
Hypothyroidism
Trauma
Malnutrition
Impaired endochondral ossification
Valgus deformity
Lateral deviation of one or more limbs distal to the affected growth plate or joint
Syndactylia
Fusion of digits
Most common joint lesions in domestic animals involve
synovial joints
Primary Degenerative Joint Disease
No apparent predisposing cause - generally observed in older animals
Pathologic Bone Fracture
Abnormal bone broken by minimal trauma or normal weight bearing
Traumatic Bone Fracture
Normal bone broken by excessive force
Nutritional Secondary Hyperparathyroidism
Dietary deficiency of Ca, excess dietary P or deficiency of Vitamin D
Typically a result of decreased Ca or increased P in the diet and affects young growing animals
Osteodystrophies - Metabolic Bone Diseases
Result from disturbed bone growth, modeling or remodeling due to either nutritional or hormonal imbalance
Osteodystrophy due to Hypervitaminosis A
Cats that consume high quantities of bovine livers
Cause deforming cervical spondylosis
Affected cats develop osteophyte formation around the joints of the cervical vertebrae, should and elbow
Metabolic Bone Disease is characterized by
Failure of production of bone matrix, its mineralization or its maintenance
Chondroplasia - Chondrodysplasia fetalis
Disproprotionate dwarfism
Breed associated, usually hereditary conditions.
Membranous appositional growth is normal but interstitial growth of cartilage is abnormal resulting in premature closure of growth plates and decreas length of long bones
Intramembranous Ossification
Bone formation that occurs within “membranes” of condensed primitive mesenchymal tissue
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Flat bones of the skull
Microscopic appearance fo osteonecrosis
Cell death with loss of osteocytes from their lacunae
Cervico-vertebral Stenotic Myelopathy - “Wobbler’s Syndrome”
Localized skeletal dysplasia
Classified as a degenerative joint disease which affects the axial skeleton
Results in dynamic or static compression of the cervcial spinal cord by abnormal cervical vertebrae
Secondary Degenerative Joint Disease
Associated with an underlying abnormality in the join or its supporting structures which leads to premature degeneration of the articular cartilage
Micromelia
Abnormally small or short limbs
Angular Limb Deformities
Common in young animals and specially important in horses
Origin can be traced to asymptomatic lesion in an active growth plate
Characterized by twisting of the bone
Osteomalacia
Grown (adult) animal disease
Failure in the mineralization of osteoid primarily due to vitamin D or P deficiency
Unmineralized osteoid is resistant to osteoclast resorption and accumulates in the bone
Affected animals may exhibit bone pain, pathologic fractures and deformities
Collapse of articular surface may occur
End-Stage Joint
Describe a joint with severe chronic injury
Affected joints exhibit variable degrees of damage to the articular cartilage, deformation, osteophyte, and pannus formation, capsular fibrosis, synovial villous hypertrophy/hyperplasia and occasional ankylosis
Rickets
Affecting young growing animals
Defective calcification of osteoid and defective endochondral ossification
Multifactoral etiology typically involves vitamin D or phosphorus deficiency
Outcome of osteonecrosis
Complete resorption and replacement of necrotic bone may occur
Formation of sequestrum
(Primary/Secondary) bone tumors are more common
Primary
Osteomyelitis
Common in young farm animals as result of bacteremia or septicemia
Omphalophlebitis is common source in neonates
Can be localized
Predilection site of Osteosarcoma
Close to the knee and way from the elbow
Types of malignant neoplasms of joints
Synovial Cell Sarcoma
Histocytic Sarcoma
Lesions of “Elbow Dysplasia Syndrome” in young dogs
Ununited anconeal process
Fragmented medial coronoid process of the ulna
Fibrous Osteodystrophy
Common metabolic bone disease
Characterized by extensive bone resportion and replacement by fibrous connective tissue and poorly mineralized immature bone
Result of persistent elevations of plasma PTH levels - hyperparathyroidism
Osteodystrophy caused by fluoride toxicosis
Occurs in herbiovores - 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
Bones exhibit periosteal hyperostosis
Two types of bone based on degree of maturity
Woven bone
Lamellar bone
Involucrum
Layer of granulation tissue and reactive bone formed as a result of attempts to wall of a sequestrum
Synovial Cell Sarcoma
Malignant tumors arising from the synovial fibrocyte origin
Histiocytic Sarcoma
Malignant tumors arising from cells of histocytic phenotype, possible dendritic cells present in synovium
Ringbone
Degenerative disease in horses affecting the inter-phalangeal joints
Common in horses used in rodeo events or Polo
Result of abrupt stops, turns and twists
Etiology of metabolic bone disease
Nutritional
Hormonal
Disuse
Toxicity
Pathogenesis of osteodystrophy due to lead poisoning
- Lead interferes with osteoclastic activity
- Subtle bone lesions
- Increase bone density (osteosclerosis) in the metaphysis
- Lead Line
Scoliosis
Lateral deviation of the vertebral column
Lamellar Bone
Mature bone. Collagen fibers are arranged in a parallel pattern
Cellular elements of bone
Osteoblasts
Osteocytes
Lining cells - inactive osteoblasts
Osteoclasts
Primary Bone Neoplasms
Osteoma
Ossifying fibroma
Osteosarcoma
Chondroma
Chondrosarcoma
Multilobular tumor of bone
Bone
Specialized connective tissue consisting of cells embedded within a gel - like substance that becomes mineralized
Primary Hyperparathyroidism
Unusually associated with functional parathyroid adenomas in dogs
Affected animals exhibit marked hypercalcemia and hypophosphatemia
Caprine Arthritis - Encephalitis (CAE)
Slowly progressive disease of goats caused by a retrovirus.
Virus produces a respiratory and neurologic syndrome.
Joint lesions are characterized hy a lymphocytic hyperplastic synovitis with the formation of carpal hygromas
Joint
Formed when two or more bones are united by fibrous, elastic or cartilaginous tissues or by a combination of these tissues
Avulsed Bone Fracture
Caused by the pull of a ligament/ muscle tendon at its insertion into bone
Osteochondritis DIssecans (OCD)
Specific form of osteochondrosis characterized by the separation of a piece of articular cartilage from the subchondral bone
Gross lesions associated with Rickets
Irregular thickening of growth plates with tongues of uncalcified cartilage extending into the metaphysis
Widening of growth plates - weigh bearing long bones may become bowed
Hemorrhages beneth the articular cartilage or in growth plates
Pathological fractures
Ribs bend rather than snap - necropsy
Varus deformity
Medial deviation of one or more limbs distal to the affected growth plate or joint
Kyphoscoliosis
Dorso-lateral deviation of the vertebral column
During fetal life, bone formation occurs in what two ways
Intramembranous ossification
Endochondral ossification
Hemimelia
Absence of the distal half of the limb
Phocomelia
Absence of the proximal portion of the limbs
Microfracture - Infraction
Fracturing of trabeculae without external deformation of cortical bone
Renal Secondary Hyperparathyroidism
Complex etiology but P retention due to loss of glomerular function and inadequate synthesis of calcitriol by the kidney play major role
Renal Osteodystropy occurs commonly in dogs - “Rubber Jaw”
Injury to articular cartilage results in
Fibrillation, eburniation or “Joint mice” formation
Endochondral ossification occurs in the
Ossification Centers - immature bones
Growth Plates - developing bones
Polymelia
Supernumerary limbs
Polydactylia
Supernumerary digits
Intervertebral Disk Disease
Occurs in all breeds as part of the aging process
Septic Arthritis
Most common in farm animals, specially the young where its a common sequel to neonatal bacteremia
Osteoid
Extracellular matrix of bone containing primarily glycoproteins and collagen fibers. Rapidly undergoes mineralization
Cervico-vertebral stenotic myelopathy is most common in
Horses and large breed dogs
Complications associated with bone fractures
Bone necrosis and formation of sequestrum
Nonunion fracture - pseudoarthrosis
Osteomyelitis
Cachexia
Cartilaginous Joints
Bones are united by hyaline cartilage or fibrocartilage
Animals with Osteopetrosis often present with
Aplastic anemia
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No space for hematopoietic tissues of the bone marrow to grow
Synovial Joints
Unite two bone ends covered by hyaline articular cartilage and an articular capsule surrounds a cavity filled with synovial fluid
Toxic Osteodystrophies
Lead Poisoning
Fluoride Toxicosis
Hypervitaminosis A
Congenital Cortical Hyperstosis
Autosomal recessive inherited condition in pigs
Limbs appear swollen due to excessive deposition of radiating trabeculae on periostal surface and blockage of the local lymphatic circulation
Affected are usually born dead or die within hours
Common sequel of Osteochondrosis
Degenerative Joint Disease
Dynamic form of Cervico-vertebral stenotic myelopathy causes compression on the spinal cord when
the neck is flexed
Woven Bone
Immature bone present during fetal development and in the early stages of bone repair. Collagen fibers in woven bone are randomly arranged adapting a criss cross (woven) pattern microscopically
Hygromas
Chronic lesions that appear as flattneed cystic fluid-filled subcutaneous distensions over the cranial carpus. Usually there is no communication with the carpal joint or tendon sheath.
Non-Infectious Arthritis
Immune mediated etiology
Inflammation is in response to persistence of antigen in the synovial membrane of affected joints, or to the deposition int he synovium of immune complexes derived from inflammatory lesions elsewhere
Affect multiple joints
Effect of Pannus on the joint
Inflammatory cells within the pannus along with collagenases from synovial fibroblasts may further damage the articular cartilage and lead to ankylosis of the joint
Aseptic Inflammation of bone
Trauma may cause osteoperiostitis with formation of exostosis
Fibrous Osteodystrophy is more commonly caused by (Primary/Secondary) Hyperparathyroidism
Secondary
Most common causes of paresis in the dog
Intervertebral Disk Disease
Osteoporosis
Decreased 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 decrease number of trabeculae in the cancellous bone
Congenital Letah Chondrodysplasia - “Dexter Bulldog”
Inherited condition of Dexter cattle
Affected calves are often aborted and exhibit disproportionate dwarfism, short vertebral column, marked micromelia, large head with short muzzle, protruding tongue and large abnominal hernia.
Pannus
Fibrovascular and histocytic tissue that develops within the synovial membrane at its junction with the periosteum and cartilage margins and can spread over the articular surfaces.
Types of Joints
Fibrous Joints - Synarthroses
Cartilaginous Joints - Amphiarthroses
Synovial Joints - Diarthroses
Canine Craniomandibular Osteopathy
Lion Jaw
Proliferative disorder confined to the bones of the skull, especially the mandibles, occipital and temporal bones
Recognized at 4-7 months of age
Affected dogs may exhibit discomfort when chewing or inability to open the mouth to eat
Endochondral Ossification
Bone formation that occurs in the majority of bones of the skeleton.
Bone develops from cartilaginous model that is subsequently replaced by osseous tissue present in the so called ossification centers
Spondylosis
Common degenerative disease of the vertebral column characterized by the formation of osteophytes at the ventral and lateral margins of vertebral bodies adjacent to vertebral spaces
When growth plates are closed what effect does that have on growth?
Growth plates close in mature animals, no further rlongitudinal growth will occur
Osteochondrosis - Dyschondroplasia
Characterized by abnormal growth and maturation of the articular cartilage
Hypertrophic Pulmonary Osteoarthropathy - Osteopathy
Kyphosis
Dorsal deviation of the vertebral column
T/F: Bones remain in a dynamic state of growth and resportion throughout life
True
Sequestrum
Piece of necrotic bone isolated from the remaining viable bone
Hip Dysplasia
Characterized by a lack of conformity between the femoral head and the acetabulum → subluxation → DJD
Static form of Cervico-vertebral stenotic myelopathy causes compression on the spinal cord occurs
No matter what position the neck is in
Chondrosarcoma
Rare in domestic species
Involves flat bones more often than long bones
Most common primary bone tumor in dogs and cats
Osteosarcoma
Osteopetrosis
Inherited disease caused by osteoclast failure to reabsorb the primary spongiosa. This failure results in an increased bone density and lack of medullary spaces
Fibrous Joints
Bones are united by fibrous tissue
Common sequel of tail biting in pigs
Vertebral abscess resulting from fracture of the vertebral body and focal compression of the spinal cord
Osteitis - Osteomyelitis
Inflammation of the bone
Osteonecrosis - Osteosis
Necrosis of bone
Ischemia usually associated with trauma but may also occur in inflammatory and neoplastic bone diseases
Necrotic bone appears paler
