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Histology of growth plate. Factors causing growth disturbance. Principles of guided growth modulation.?Answer this question for ms orthopaedic university exam 10 marks in handwritten notes image format

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Growth Plate Handwritten Notes
Here are your MS Orthopaedics exam notes. Below is the complete typed version of all content for reference and study:

GROWTH PLATE (PHYSIS) - HISTOLOGY, GROWTH DISTURBANCE & GUIDED GROWTH MODULATION

1. HISTOLOGY OF GROWTH PLATE

The physis is a cartilaginous disc between epiphysis and metaphysis responsible for longitudinal bone growth. It has 4 zones arranged from epiphysis toward metaphysis:
ZoneKey Features
Zone 1 - Reserve (Resting)Small scattered chondrocytes; stem cell-like progenitor cells; stores lipids/glycogen; anchors physis to epiphysis
Zone 2 - ProliferativeChondrocytes divide into "coin-stack" columns; most active growth zone; produces collagen type II; weakest zone - fractures occur here
Zone 3 - HypertrophicCells enlarge 5-10x; three sub-zones: maturation, degeneration, provisional calcification; vascular invasion begins
Zone 4 - Ossification (Primary Spongiosa)Capillary invasion; osteoblasts deposit bone on calcified cartilage scaffold; remodelled to secondary spongiosa
Key point: Thickness of physis remains constant during growth - new cartilage produced = cartilage resorbed.
Here is a real histology image of the growth plate (picrosirius red stain, 17-week human fetal physis):
Growth plate histology showing zones H (Hypertrophic), P (Proliferative), R (Resting) and Bone
(Zones H = Hypertrophic, P = Proliferative, R = Resting - Firestein & Kelley's Rheumatology)

2. FACTORS CAUSING GROWTH DISTURBANCE

A) Traumatic
  • Salter-Harris (SH) types III, IV, V carry highest risk
  • SH V (crush/compression) - worst, often missed acutely
  • Bony physeal bar: peripheral bar → angular deformity; central bar → shortening
  • Most physeal fractures run through the proliferative zone
B) Infection
  • Neonatal haematogenous osteomyelitis: metaphyseal vessels cross physis in children <18 months
  • Septic arthritis: proteolytic enzymes directly destroy cartilage
  • Especially dangerous: hip (proximal femur physis)
C) Radiation
  • Doses >2000 cGy cause chondrocyte death
  • Growth arrest or angular deformity depending on field
D) Vascular/Ischaemic
  • Perthes disease (AVN femoral head)
  • Sickle cell disease: physeal infarction
  • Disruption of perichondrial ring of LaCroix
E) Metabolic/Nutritional
  • Rickets: widened, cupped, frayed physis; disorganised zones
  • Scurvy: zone of provisional calcification primarily affected
  • Hypothyroidism, growth hormone deficiency
F) Iatrogenic
  • Hardware crossing physis (threaded pins most damaging)
  • Principle: use smooth wires, smallest diameter, remove as soon as stable
G) Tumours/Dysplasia
  • Multiple hereditary exostoses: osteochondromas tether physis
  • Achondroplasia: FGFR3 mutation - reduced proliferative zone activity

3. PRINCIPLES OF GUIDED GROWTH MODULATION

Definition: Temporary, reversible, partial physeal tethering to correct angular deformity or limb length discrepancy in a skeletally immature patient.
Underlying Principle - Hueter-Volkmann Law:
  • Increased compressive load → inhibits physeal growth
  • Decreased compressive load → stimulates physeal growth
  • Tethering the convex side slows growth there, allowing the concave side to "catch up"
Methods:
  1. Stapling (Blount, 1949)
    • Metallic staples across physis on convex side
    • Disadvantages: can damage physis, staples may "walk out," less predictable
  2. Tension Band Plate / 8-Plate (Metaizeau; popularised by Stevens)
    • Plate spans physis with 2 screws (one epiphyseal, one metaphyseal)
    • As limb grows, screws diverge in a tension-band effect
    • Fully reversible - plate removed once deformity corrected
    • Indications: genu valgum, genu varum, tibia vara, limb length discrepancy, knee flexion contracture
    • Timing: condyle must be large enough for smallest screw (>16 mm)
  3. Transphyseal Screw
    • Single cannulated screw crossing physis
    • Minimally invasive, simple technique
Timing of intervention:
  • Predict using Moseley straight-line graph or Green-Anderson tables
  • Correction rate approximately 1° per month at the knee
  • Must have adequate growth remaining
Advantages over corrective osteotomy:
  • Minimally invasive, often outpatient
  • Reversible and adjustable
  • Gradual correction (no acute deformity)
  • Can be repeated if overcorrection occurs
Complications:
  • Overcorrection/rebound deformity after plate removal
  • Hardware failure or migration
  • Physeal damage (rare with smooth implants)
  • Loss of correction
Sources: Campbell's Operative Orthopaedics 15th Ed 2026; Histology: A Text and Atlas (Eroschenko/Ross 9e); Firestein & Kelley's Textbook of Rheumatology
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