Bone lengthening usually takes about 6 months to a year before the brace can be removed, and in some cases it can take up to 18 months. Bone lengthening is generally used in the case of bone defects or infections caused by trauma. Currently, ilizarov stent is mostly used, which needs to be adjusted by about 1mm each to achieve the purpose of bone lengthening, so the time of bone lengthening depends on the length of the bone defect, and in the process of lengthening, it is necessary to pay attention to the gradual and progressive functional exercises, to avoid the deformity caused by the excessive tension of the tendon, etc. The time of bone lengthening unloading depends on the bone healing condition. The time of bone lengthening and unloading of the stent also depends on the healing of the bone, and the stent can be unloaded only when the bone is basically healed, and the bone lengthening has a certain range, and it can not be lengthened indefinitely, which will cause nerve damage. For small bone defects and good bone healing, the stent may be removed in half a year; for longer bone defects and poor bone healing, it may take a year to a year and a half before the stent can be removed.