Bone lengthening surgery is an effective method for treating limb inequality caused by various reasons. A series of complications arise due to the high risk of surgery and complicated technical operation, and serious complications can lead to the failure of the surgery, so this surgery is very demanding and requires sophisticated surgical instruments and high level of doctors to ensure the success of the surgery and achieve good results. Bone lengthening complications: 1. Needle tract infection The incidence is high and is one of the common complications, related to more steel needles, unreasonable layout, cutting skin during lengthening, long healing process, loss of steel needle tension, etc. The observed analysis of needle tract infection is related to the following reasons: ① frequent needle hole disinfection; ② external causes of crusting off at the needle hole and exposed trauma; ③ chronic cutting injury caused by long-term pulling (related to the diameter of steel needles); ④ excessive functional exercise; ⑤ weakened patient resistance (such as after a cold). Therefore, after surgery, regularly observe the dressing at the needle hole for blood and ooze, change the dressing regularly, keep the skin around the needle hole clean and dry, and do not overdo the amount of liquid when disinfecting the needle hole with alcohol to prevent the infiltration into the subcutis causing tissue necrosis and weakening the local resistance. If redness and swelling around the needle channel and abnormal secretions are found, immediately strengthen the dressing change, stop extending and apply antibiotics to control the infection. If the infection is serious, the steel needle can heal after removal. Extend the steel needle should try to use a fine steel needle fixed. 2, steel needle relaxation and steel needle breakage With the adjustment of the extender and limb lengthening and functional exercise, steel needle relaxation and stress concentration steel needle fatigue and fracture will occur. Extend the steel needle should try to use tension after the fixed, maintain the tension of the steel needle, and regularly check the tightness of the steel needle. Intraoperative tightening of the screw should be reliable, the steel pin cut-off should leave a margin for relaxation and then tighten. The process of tightening the screw after relaxation should also be slow, gradually reaching balance with another crossed steel pin. The main reasons for this are incomplete osteotomy and slow lengthening speed. In addition, partial resection of the tibial lengthening fibula is also very important, often inducing tibial fusion due to early fusion of the fibula. Through clinical observation, we believe that the optimal speed of lengthening is about 0,7 mm/d and should not be lower than 0,33 mm/d. If the lengthening speed is too slow in violation of this principle, it will easily lead to complications of early mineralization and fusion of the bone end. 4, delayed healing and bone discontinuity Traditional methods of lengthening speed of 1 ~ 1, 5 mm / d, through clinical observation, we believe that the best speed of lengthening about 0, 7 mm / d, the maximum limit should not exceed 1 mm / d, if the violation of this principle lengthening speed is too fast easily lead to delayed bone healing, and even bone discontinuity complications occur. 5.Axial deviation Firm and stable external fixation and skilled anatomical knowledge after osteotomy are the basic conditions for maintaining the axial direction in lengthening to prevent angulation. Unequal muscle strength at the osteotomy and unstable single-ring fixation and osteotomy position are the main factors of axial deviation. The proximal tibia tends to outflank pronation and the distal tibia is prone to inversion pronation. Understanding these basics can overcome or reduce the occurrence of angular deformity. Therefore, it is more important to prevent its occurrence. Preoperatively, the angulation direction is expected, and the lengthener is placed at an intraoperative tilt of 5-10 degrees to ensure a good axis through lengthening, and the lengthener is adjusted at any time during postoperative observation if limb deviation, angulation, torsion, and disproportion are found. 6, muscle contracture and joint dysfunction After the calf lengthening, the tendon is passively elongated and the external fixation nail is placed to restrict the contraction of the muscle beyond its extendable adjustment range, thus limiting the activities of the knee and ankle joints. lizarov et al. have shown with evidence that under certain speed and frequency of tension, the muscle tissue has a regenerative function; however, if a certain limit is exceeded, it will lead to muscle tissue regeneration is uncontrolled and contractures occur, resulting in muscle contractures with limited flexion and extension or even stiffness of the joint. In order to avoid knee and ankle joint dysfunction and muscle contracture during the entire process of tibiofibular lengthening, functional exercise instruction is required during the treatment process, specifically including: ① Routine load exercise is necessary to maintain normal joint function and maintain the internal environment. During limb lengthening, strengthen the joint active and passive flexion and extension activity functional exercise; at the same time, the intermittent stress stimulation generated during limb activity has the effect of promoting bone healing. Patients should be encouraged to perform joint activities during distraction lengthening, with isometric muscle contraction, etc., supplemented by muscle massage and passive activities of the joint (CPM machine) to promote blood circulation, maintain muscle strength and normal mobility of the joint, and reduce the occurrence of complications. ②Auxiliary magnetic therapy and medication to promote fracture healing to accelerate the healing of the osteotomy end and remove the bone lengthener as early as possible. (3) During tibiofibular lengthening, especially large lengthening, the mobility of knee and ankle joints decreases, but through functional exercise, joint function can be improved or restored. Exercise should be gradual, 3 to 4 times a day, 10 to 20 minutes each time, not fast and violent. 7, neurovascular injury In the early stage of lengthening, the affected leg is slightly elevated with a thin pillow for 2 weeks after surgery, and the blood flow of the distal end of the affected limb and the sensation, movement and wound drainage of the toes are closely observed to facilitate the detection of nerve and vascular injury of the limb, and the spreader screw on the lengthening device is twisted every day since the 7th day after surgery to lengthen it by 0,67～1,0mm, and the speed of lengthening depends on the patient’s tolerance. Close observation to avoid blood circulation and neurological dysfunction of the limb due to excessive stretching In the middle and late stages of lengthening, the neurovascular lengthening is stretched because it is slower than the bone lengthening, and if not handled properly, vascular nerve injury can easily occur. In the treatment, closely observe the skin sensation, joint activity, arterial pulsation and peripheral circulation of the affected limb, and take timely measures if abnormalities are found, such as foot bruising, pallor and swelling can be judged as vascular crisis, remove external factors such as whether the limb is compressed or overly tightly wrapped, and report to the doctor to give dilation, elevation of the affected limb, physiotherapy, massage, and in severe cases, incision and decompression. If there is loss of active movement of the toes, severe pain, numbness, abnormal sensation can be judged as neurological crisis, remove any external factors such as limb compression, tight bandaging, etc., and still no improvement should be considered to be slowed down the lengthening speed, etc. If there is still no improvement, then stop lengthening or even shorten appropriately. Usually relief can be obtained, but if the vascular nerve has been torn then it needs to be explored and repaired. There is another condition that should also be noted to prevent direct injury to the vascular nerve when penetrating the steel needle. We believe that increasing the number of extensions appropriately in the middle and late stages of lengthening, 6 to 8 times/day, is beneficial in preventing complications of vascular nerve injury.