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

Complications

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

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)