Physeal Dysplasia with Slipped Capital Femoral Epiphysis

• Slipped capital femoral epiphysis seen in dogs, foals and calves
• Associated with severe trauma
• Pigs – manifestation of osteochondrosis with only minimal trauma required
• Most common type of physeal fracture in small animals and the proximal femur is the most common site
• In horses, physeal dysplasia is synonymus with physitis

More about Physeal dysplasia

• Also seen in the coypu with minimal trauma
• Femoral head physes contribute 30-40% of longitudinal growth of the femur in small animals
• Slipped epiphysis -> Salter-Harris type I where only the physis is involved
  • Most common type of physeal fracture in small animals and the proximal femur is the most common site
  • In traumatic cases, the fracture crosses through mutiple zones of the physis, with chondrocytes maintaining their linear arrangement on both sides of the fracture site for 1-4d following trauma
• Slipped capital femoral epiphysis – seen in humans, mainly adolescent boys, autosominal dominant with variable penetrance

In cats:

• [Physeal dysplasia with slipped capital femoral epiphysis in 13 cats. Craig LE. Vet Path (2001) 38 92-7]
  • Age 12-21months
  • 90% males
  • Often obese, lots of Siamese cats
  • Normal growth plates close at 7-9mths so these physes should have been closed
  • Histology – physeal dysplasia with persistence of an open, disorganized growth plate
    • Wide physis, necrotic cartilage at the cleavage site
    • Irregular clusters of chondrocytes separated by abundant chondroid matrix. Similar lesions in femoral neck.
  • No necrosis of the femoral head, although there is usually a small areas of peripheral attachment at the perichondral fibrocartilagenous complex – could provide some vacularization **The ligamentum teres provides no blood supply to the femoral head
  • Clusters of chondrocytes present on either side of the cleavage site
  • Differs from osteochondrosis by:
    • More diffuse affecting the whole physis (in OC – focal failure of endochondral ossification)
    • Chondrocytes are arranged in disorganized clusters rather than parallel rows
    • The cat breeds have not been selected for rapid growth
  • Insulin may have a role to play – most of the cats were obese....Similar deal to horse osteochondrosis