You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is All of the following are types of avascular non-union except: and explain in detail?
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