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Introduction
  • Always look to see if physis is open
  • Unique principals in pediatric bone
    • elasticity
      • more elastic which leads to unique fracture patterns
        • buckle fractures
        • greenstick fractures
    • remodeling potential
      • open physes (growth plates) can allow extensive bone deformity remodeling potential
      • occurs more rapidly in plane of joint motion
        • sagittal plane in wrist, due to primarily extension/flexion
      • occurs more at the most active physes, due to most growth and potential for remodeling
        • most active physes in upper extremity
          • proximal humerus 
          • distal radius
        • most active physes in lower extremity
          • distal femur 
          • proximal tibia
  • Same principles as adult bone
    • intra-articular fractures must be reduced
 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
  • Schmids
  • Fractures most commonly occur through hypertrophic zone


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
 

 

  • Perichondrial artery 
    • major source of nutrition to physis 
Injury Classification
  • Salter-Harris classification
    • Type 1-  physeal separation
    • Type 2- fracture traverses physis and exits metaphysis
      • most common type
      • Thurston Holland fragment
    • Type 3- fracture traverses physis and exits epiphysis
    • Type 4- fracture passes through epiphysis, physis, metaphysis
      • Thurston Holland fragment
    • Type 5- crush injury to physis
Treatment
  • Closed reduction vs. CRPP vs Open reduction
    • depends on injury pattern
    • intra-articular fractures must be reduced
Complications
  • Growth arrests
    • overview
      • complete arrest leads to shortening
        • see Leg Length Discrepancy topic
      • partial arrest leads to angulation
    • treatment
      • bar resection with interposition
        • indications
          • < 50% physeal involvement
          • > 2 years or 2cm growth remaining
      • ipsilateral completion of arrest
        • indications
          • > 50% physeal involvement
          • can combine with contralateral epiphysiodesis and/or ipsilateral lengthening
 

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