Joints Developmental - Pathology

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Hip Dysplasia

Elbow Dysplasia

Osteochondrosis

Osteochondrosis in pig elbow (Image sourced from Bristol Biomed Image Archive with permission)
Osteochondrosis dissecans (Image sourced from Bristol Biomed Image Archive with permission)
  • Defect in cartilage growth (i.e. dyschondroplasia)
  • In growing animals: large breeds of dogs (4-8 months), pigs (5-7 months) and horses (weeks - 2 years)
  • Involves both the growth plate and the immature joint cartilage
  • Multifactorial:
    • Trauma
    • Genetic
    • Rapid growth
    • Ischaemia
    • Nutritional
  • Essentially idiopathic
  • Failure of endochondral ossification
  • Lesions bilateral in 70% of cases but lameness often unilateral, sometimes no clinical signs
  • Some authors consider this condition more generalised, in which case e.g. ununited anconeal process would be part of osteochondrosis syndrome

Different manifestations include:

  • 1. Osteochondrosis dissecans (OCD):
    • Retained cartilage cores
      • White, wedge-shaped areas of retained cartilage in the metaphysis
      • Clefts -> separation of cartilage from bone -> flaps or free joint mice
      • May interfere with joint function
    • Lysis → bone cysts
    • Focal disruption of endochondral ossification
    • -> Angular limb deformities and degenerative joint disease
    • May be present together with synovitis
    • Predilection sites:
      • In dogs:
        • Proximal humerus
        • Lateral femoral condyle
        • Coronoid process of ulna
      • In pigs:
        • Humeral and medial femoral condyles
        • Anconeal process of elbow
      • In horses:
      • Medial femoral condyle
      • Distal tibia
    • Osteochondrosis dissecans in dogs:
      • Grossly:
        • Lesion in central part of the caudal aspect of developing ossification centre in humeral head
      • Histologcally:
        • Lesion filled with granulation tissue (fibroplasia)
        • Surrounding thickened bone spicules
        • Cap of thickened articular cartilage over the defect
        • -> May fragment - joint mice
        • Calcified cartilage fragments may be in the posterior pocket of joint capsule
          • May grow through synovial fluid nourishment
  • 2. Epiphysiolysis
    • Not associated with retention of cartilage
    • Separation of epiphysis from the metaphysis
    • Likely to be due to trauma to degenerated growth plate
    • Possibly the basis of ununited anconeal process and ununited coronoid process in dogs


Arthrogryposis

  • Persistent congenital flexure of a joint in conjunction with muscle contraction
  • Caused by:
    • Inactivity or paralysis in utero
    • Spinal dysraphism
    • Intrauterine viral infections
    • Toxic plants (poison hemlock, lupine)
    • Cause persitent contraction of uterus -> fetal compression
  • Arthrogryposis and palatoschisis in Charolais cattle


Angular limb deformity