The growth rate of bone scab is different for each person, and it is normal to have very few scabs in 40 days. The reasons for slow growth of bone scabs include older age, poor nutrition, and serious injuries. 1. Older age: Generally speaking, compared with children and teenagers, the growth rate of bone scab is slow in the elderly. 2. Poor nutrition: If the nutrition is lacking or the health condition is not good, it will lead to the slow growth of bone scabs. 3. Serious injury: If the injury is serious, for example, the periosteum is seriously broken, or the fracture is not well aligned or aligned, it will also lead to slow growth of the bone scab. You should pay attention to the leg not to bear weight, otherwise it is easy to cause the fracture to be re-displaced, affecting the healing of the fracture. It is normal to have a fracture of the tibia in cast for 40 days with very little bone scab, and the X-ray should be reviewed regularly, and according to the healing condition of the fracture, the doctor should judge the degree of activity that can be taken, and carry out functional exercises appropriately.