Non-union occurs when there are no signs of healing after >3-6 months (depending upon the site of fracture). Non-union is one endpoint of delayed union. The distinction between delayed union and non-union can be slightly arbitrary: whilst fractures can generally be expected to heal in 3-4 months this will vary in the case of open fractures and those associated with vascular injury, and also in the presence of patient risk factors described below. However, non-union is generally said to occur when all healing processes have ceased and union has not occurred.