Difference between revisions of "Bones Developmental - Pathology"

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Revision as of 14:46, 26 September 2008


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()Map MUSCULOSKELETAL SYSTEM (Map)
BONES



Generalised

Proportionate dwarfism

  • Miniature breeds
  • Due to growth factor deficit

Chondrodysplasia

  • Literally means “abnormal cartilage development”
  • Defective cartilage growth at the physis
  • Usually genetic cause
  • Occurs in cattle, dogs, sheep, pigs and cats
  • Leads to disproportionate dwarfism (contrast with miniature breeds)
    • Generally, growth is disproportionate because only the growth of bones which form from cartilage models is retarded – growth of other bones is normal (i.e. long bones shorter than normal)

In Dogs:

  • Localised forms occur in dogs (e.g. affecting skulls of Pekingese and Bulldogs or the limbs of Dachshunds and Bassett hounds)
  • Occasionally seen in immature Beagles, Poodles, Alaskan Malamutes, Scottish Deerounds and Norwegian Elkhounds

In Cattle:

  • Dexter cattle
    • Are heterozygous for incompletely dominant gene
    • When homozygous - lethal, producing 'buldog calf'
    • Usually aborted prior to seven month of pregnancy
    • Also occurs in Holstein, Jerseys and Charolais
    • Grossly:
      • Limbs and vertebral column are short
      • Domed cranium
      • Protruding tongue
      • Absent hard palate
      • Large umbilical hernia with eventrated abdominal organs
    • Histologically:
      • Proliferative and hypertrophic zones in the physes are irregularly separated by fibrovascular tissue
      • Chondrocytes are not properly arranged
      • Irregular ossification and mineralisation
  • Telemark type
    • Cattle of Norwegian origin
    • Also seen in Jersey cows
    • Calves born alive, unable to stand and die soon after birth
    • Grossly:
      • Domed cranium
      • Brachygnatic face
      • Protruding tongue
      • Cleft palate
      • Short neck and limbs
  • Brachycephalic 'Snorter' type
    • Hereford and Aberdeen Angus
    • Show nasal dyspnoea and chronic rumenal tympany
    • Grossly:
      • Short, broad head
      • Prominent, laterally displaced eyes
      • Short and compressed vertebral column
      • Distal long bones shorter than proximal
    • Histologically:
    • Physes appear normal
    • Pallisading chondrocytes fewer in number
    • Less hypertrophy

In Sheep:

  • Ancon type
    • Short limbs due to premature closure of growth plates
    • Now rare
  • Spider lamb
    • Hereditary (autosomal recessive) in Suffolk and Hampshire breeds in North America
    • Long, thin, angular limbs
    • May be born alive or dead, aborted or develop symptoms within a month of birth
    • Grossly:
      • Fine bones, poor musculature, small heads, scoliosis
    • Histologically:

In Pigs:

  • Occurs in Danish Landrace
  • Autosomal recesive inheritance
  • Dwarfs with short legs, forelegs shorter than hind legs
  • Abnormal movement is noticable at weaning
  • Sequel is arthrosis

Osteopetrosis (Marble bone disease)

  • Occurs in sheep, dogs, cattle, horses
  • Failure of resorption by osteoclasts -> failure of remodelling of cancellous bone
  • Bones become thickened and dense but brittle
  • Marrow cavites are full of unresorbed primary spongiosa
  • Thickened intramembranous bones of skull -> altered shape of brain
  • Associated with severe viral infections, e.g. FeLV, BVD
  • Hereditary in Angus cattle


Lysosomal storage disease

  • Excess accumulation of metabolites in lysosomes
  • Affects mainly nervous system
  • Also affects growth of cartilage


Osteogenesis Imperfecta

  • Cause of fragile bones in humans, very rarely in animals
  • Reported in Holstein and Charolais calves
  • Poor mineralisation of bones and teeth
  • Fractures are often present at birth


Congenital hyperostosis of pigs

Hyperostosis (Image sourced from Bristol Biomed Image Archive with permission)
  • Rare, genetic
  • Diaphysial dysplasia
  • Excessive periosteal intramembranous bone, particularly in long bones
  • Grossly:
    • Greatly thickened long bones
    • Tense, shiny skin, closely adherent to tissues below
  • Born dead or die soon after birth




Retention of elongated primary trabeculae

  • Happens due to impaired osteoclastic activity
  • Primary trabeculae do not transform into secondary and tertiary
  • Continue to elongate
  • Form a dense band beneath growth plate - growth retardation lattice
  • Dense spikules apparent on radiographs
  • Can be caused by distemper virus, bovine viral diarrhoea virus

Localised

  • Hemimelia - abscence of one of limb bones
  • Syndactylia - fusion of toes
  • Polydactylia - increased number of digits
  • Ecterodactylia - cleft in paw extending to metacarpus of dogs and cats


Cervical Vertebral Stenotic Myelopathy (Wobblers)

  • Equine disease
  • Narrowing of the vertebral canal due to malalignment or maldevelopment of the vertebrae
  • Fast growing male TBs ranging from 8 months to 4 years
  • Hind limb ataxia due to cord compression


Angular limb deformity

  • Lateral deviation of distal portion of limb (valgus)
  • Medial deviation of distal portion of limb (varus) - more rare
  • Most common in foals
    • Carpal joint
    • Tarsal joint
    • Fetlock joint
  • Congenital or acquired
  • Due to:
    • Malpositioning in utero
    • Excessive joint laxity
    • Hypothyroidism
    • Trauma
    • Overnutrition
    • Defective endochondral ossification
    • Poor conformation
    • Disruption of blood supply to one side of bone
    • Secondary to physitis in horses
  • Usually resolves spontaneously in one to two weeks of life
  • More severe cases exceding compensatory capabilities will persisist
  • Cartilage development is affected


Fibrous dysplasia


Physitis

  • In horses
  • Often associated with angular limb deformity
  • Also called epiphysitis and physeal dysplasia
  • Problem of endochondral ossification
  • Two age groups
    • Weanlings
    • Yearlings in early training and two-year-olds
  • May cause contracted tendons and flexural deformities
  • Factors probably involved in its development:
    • Genetically fast growth rate
    • Large quantities of imbalanced, high energy feed
    • Imbalanced weight-bearing on joints
    • Excessive activity
    • Growth spurts
  • Histologically: (appearance similar to angular limb deformity)
    • Lateral aspect of radius
      • Thickened metaphyseal part of physeal cartilage
      • -> Delay or disturbance of endochondral ossification
      • Compression
    • Central part
      • No obvious deformity
    • Medial aspect
    • Laxity of periarticular attachements in young foals allows angular limb deformity; not occuring in older foals and young horses
    • (Sustained trauma produces similar lesions)


Developmental abnormalities