Physeal Anatomy

Physeal Anatomy
Physeal Growth Plate
(letters on left correspond to histology in top right)
B. Reserve zone
  • Cells store lipids, glycogen, and proteoglycan aggregates for later growth and matrix production
  • Low oxygen tension

 

  • Gaucher’s
  • diastrophic dysplasia
  • Kneist*
  • pseudoachondroplasia*
C. Proliferative zone
  • Proliferation of chondrocytes with longitudinal growth and stacking of chondrocytes.
  • Highest rate of extracellular matrix production
  • Increased oxygen tension in surroundings inhibits calcification

 

  • Achondroplasia
  • Gigantism
  • MHE
D. Hypertrophic zone
  • Zone of chondrocyte maturation, chondrocyte hypertrophy, and chondrocyte calcification.
  • Three phases occur in the hypertrophic zone
    • Maturation zone: preparation of matrix for calcification, chondrocyte growth
    • Degenerative zone: further preparation of matrix for calcification, further chondrocyte growth in size (5x)
    • Provisional calcification zone: chondrocyte death allows calcium release, allowing calcification of matrix
  • Chondrocyte maturation regulated by local growth factors (parathyroid related peptides, expression regulated by Indian hedgehog gene)
  • Type X collagen produced by hypertrophic chondrocytes important for mineralization

 

  • SCFE (not renal)
  • Rickets (provisional calcification zone)
  • Enchondromas
  • Mucopolysacharide disease
  • SED
  • MED
  • Schmids
  • Kneist*
  • Pseudoachondroplasia*
  • Fractures most commonly occur through the zone of provisional calcification, specifically Salter-Harris I fractures

 

E. Primary spongiosa
(metaphysis)
  • Vascular invasion and resorption of transverse septa.
  • Osteoblasts align on cartilage bars produced by physeal expansion.
  • Primary spongiosa mineralized to form woven bone and then remodels to become secondary spongiosa (below)
  • Metaphyseal “corner fracture” in child abuse
  • Scurvy
Secondary spongiosa
(metaphysis)
  • Internal remodeling (removal of cartilage bars, replacement of fiber bone with lamellar bone)
  • External remodeling (funnelization)
  • Renal SCFE
Physis Periphery
Groove of Ranvier
  • During the first year of life, the zone spreads over the adjacent metaphysis to form a fibrous circumferential ring bridging from the epiphysis to the diaphysis.
  • This ring increases the mechanical strength of the physis and is responsible for appositional bone growths
    • supplies chondrocytes to periphery
 

  • Osteochondroma

 

Perichondrial fibrous ring of La Croix
  • Dense fibrous tissue that is the primary limiting membrane that anchors and supports the physis through peripheral stability

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