This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Orthopaedics
All of the following factors facilitate nonunion except - 
Select and explain. 
A. Haematoma formation, B. Periosteal injuries, C. Absence of nerve supply, D. Chronic infection
A: Haematoma formation
Answer: A: Haematoma formation 
Explanation: A hematoma or blood clot occurs at the fracture site.
This hematoma provides two important factors for fracture healing:-


First, the hematoma provides a small amount of mechanical stability.
Second, and perhaps more importantly, the hematoma brings osteoblast and chondrocytes precursors to the fracture site in large numbers that can begin to differentiate into osteoblast and chondrocytes to begin producing matrix.


Other three options are causes of nonunion.