All of the following are types of avascular non-union except:: (A) Comminuted, (B) Elephant foot, (C) Torsion wedge, (D) Atrophic
Answer is B. Classification of non-union:
 Hypervascular non-union:

Elephant foot (hypertrophic , rich in callus)
Horse foot (mildly hypertrophic , poor in callus)
Oligotrophic (non-hypertrophic, no callus)

Avascular non-union:

Torsion wedge
Comminuted
Defect
Atrophic