Osteochondroma : Mnemonics

Features of Osteochondroma

Mnemonic: Six “C”

  1. Commonest benign bone tumor
  2. Continue to grow until Closure of physis
  3. Cartilage cap (appears larger clinically than in X-ray)
  4. Continuous with native bone (cortex and medullary canal)
  5. Cane (pedunculated/stalked points away from joint and sessile/broad based have higher risk of malignant degeneration)
  6. Change (mutation) in EXT1, EXT2 and EXT3 genes


Mnemonic: ABCDE

  1. Adventitious bursa (pain)
  2. Breakage of stalk (pain)
  3. Chondrosarcoma (pain; risk: 1% in solitary osteochondroma and 10% in multiple osteochondroma)
  4. Deformities:
    • Femoral shortening
    • Coxa valga
    • Genu valgum, Ankle valgus (because of shortened fibula)
    • Patellar dislocation
    • Ulnar shortening, radial bowing and ulnar deviation of hand
    • Radial head dislocation
  5. Encroachment:
    • Nerve compression (sciatic, common peroneal, radial)
    • Pseudoaneurysm (popliteal artery)
    • Tendon (rotator cuff impingement, subscapularis tear, bicipital tendinitis)

Common locations

Mnemonic: FGH

  1. Femur (proximal)
  2. Genu (knee)
  3. Humerus (proximal)
  4. Hallux (subungual)

Risk factors for Malignant transformation

Mnemonic: GLAD PaST

  1. Growth after skeletal maturity
  2. Lucency (new)
  3. Additional scintigraphic activity
  4. Destruction (cortical)
  5. Pain after puberty
  6. Soft tissue mass
  7. Thickened cartilage cap >1.5 cm

Pathogenesis theories

theories osteochondroma

Mnemonic: Five “P”

1. Bone defect

  • Perichondral bone defect and (Keith)

2. Cartilaginous metaplasia

  • Periosteal metaplasia in periphyseal-perimetaphyseal area producing cartilage (Muller)

3. Displacement of physis

  • Peripheral part of physis displacement (Virchow)

4. Epiphysis retains chondrogenic potential

  • Pathological retainment of chondrogenic properties by the epiphysis that would form perichondral bone of the groove of ranvier (Langenskiold)

5. Failure of tubulation

  • Prominent metaphysis suggesting tubulation failure (Jansen)

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