This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anatomy and physiology of bone and fracture healing, Subject name: Orthopaedics
All are True about fracture healing except : 
Select and explain. 
A. Nutrition affects healing, B. Stable fixation promotes healing, C. Compression at fracture site causes nonunion, D. Hormonal status may affect healing
C: Compression at fracture site causes nonunion
Answer: C: Compression at fracture site causes nonunion 
Explanation: Compression at fracture site improves healing by inducing callus formation Compression enhances the rate of union in cancellous bone. In coical bones, compression at the fracture site enhances rigidity of fixation, and possibly results in primary bone healing. Ref: Maheshwari 9th ed pg 12.