**4. Different bone defects treatment techniques**

There is no standard for the definition of critical-sized bone defects, however typically a defect greater than 1–2 cm or loss over 50% of the circumference of the bone can be called a critical-sized bone defect. It should be notice that this definition also can be changed according to the defect location site or the situation of surrounding soft tissues [27–29]. For example femur, 6–15 cm can be classified as a large bone defect due to its good soft-tissue environment, while tibia defects over 1 cm can be defined as a large bone defect due to its lower healing capacity [27]. In another report, bone defects greater than 3, 5, and 6 cm in the forearm, femur/tibia, and humerus, respectively, were considered critical-sized defects [30]. Therefore, various parameters should be considered in the critical-sized bone defect and in general, it can be defined as an osseous defect that cannot be healed spontaneously during the lifetime or less than 10% of bone regenerated during the lifetime [31]. Different treatment methods have been reported for the treatment of bone complications, especially large bone defects, some of the most important treatment methods are summarized below. **Table 1** summarized the mentioned methods with their advantages and disadvantages.

### **4.1 Physical treatments**
