Bone lengthening surgery is an effective way to treat unequal length of limbs caused by various reasons, due to the high risk of surgery, complex technical operation and a series of complications, serious complications can lead to failure of the operation, so the operation is very demanding, need to have sophisticated surgical instruments and high level of doctors, in order to ensure the success of the operation, and achieve good results. Bone lengthening complications: 1. Needle tract infection The incidence is high, which is one of the common complications, related to more steel needles, irrational layout, cutting the skin in the lengthening process, long procedure, loss of tension of steel needles and so on. After observation and analysis of the needle tract infection is related to the following reasons: ① frequent disinfection of the needle hole; ② external causes caused by the needle hole crusting off, trauma exposure; ③ long-term pulling caused by chronic cuts (related to the diameter of the steel needle); ④ excessive functional exercise; ⑤ weakened resistance of the patient (such as after a cold). Therefore, after the operation, observe the dressing at the needle hole regularly to see if there is any blood seepage and oozing, change the dressing regularly, keep the skin around the needle hole clean and dry, and don’t overdo the amount of liquid when disinfecting the needle hole with alcohol to prevent it from seeping into the subcutaneous tissues to cause necrosis and weakening of the resistance of the local area. If you find redness, swelling and abnormal secretion around the needle tract, immediately strengthen the dressing change, stop prolongation and apply antibiotics to control the infection. If the infection is serious, it can be healed after the removal of the steel needle. Extension of the steel needle should try to use a fine steel needle fixed. 2.Steel needle relaxation and needle breakage With the adjustment of the lengthening device and limb lengthening and functional exercise, there will be steel needle relaxation and stress concentration of steel needle fatigue and breakage phenomenon. Extension of the steel needle should be used as much as possible after the tensile fixation, to maintain the tension of the steel needle, regularly check the tightness of the steel needle. Intraoperative tightening of the screws should be reliable, and the pin should be truncated to leave room for slackening and retightening. The process of tightening the screws after relaxation should also be slow, and gradually reach the balance with another cross pin. 4, the extension of the bone end of the early mineralization and fusion is not very common, the main reason is incomplete osteotomy and extension of the speed is too slow. In addition, tibial extension of fibular part of the resection is also very important, often due to the early fusion of fibula induced tibial fusion. 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 is easy to lead to the complication of fusion of bone ends with early mineralization. 5.Delayed healing and bone nonunion The traditional method of extending the speed of 1~1.5mm/d, through clinical observation, we believe that the optimal speed of extension is about 0.7 mm/d, the maximum limit should not be more than 1mm/d, if the violation of the principle of extending the speed of too fast can easily lead to delayed healing of the bone, and even the occurrence of bone nonunion complication. 6, axial offset After osteotomy, firm and stable external fixation and skillful anatomical knowledge are the basic conditions to keep the axial direction to prevent angulation in the extension. Unequal muscle strength at the osteotomy and unstable single-ring fixation as well as osteotomy position are the main factors of axial offset. The proximal tibia tends to externally pronate and the distal tibia is prone to internally pronate. Knowledge of the above basics can overcome or minimize the occurrence of angulation deformities. Therefore, prevention is even more important. The direction of angulation is predicted before operation, and the extender is placed at a tilt of 5~10 degrees during operation to ensure a good axis through extension, and the extender can be adjusted at any time if the limb is found to be offset, angulated, twisted, or disproportionate in the process of observation after operation. 7, muscle contracture and joint dysfunction after calf lengthening tendon elongation, placed external fixation nails to limit the muscle contraction, more than its stretchable range of adjustment, thus limiting the activities of the knee and ankle joints. Ilizarov et al. have used evidence to show that, at a certain speed and frequency of retraction conditions, muscle tissue has a regenerative function; however, if more than a certain limit will result in However, if a certain limit is exceeded, it will lead to uncontrolled regeneration of muscle tissue and contracture, which will result in muscle contracture and joint flexion/extension limitation or even stiffness. In the whole process of tibiofibular lengthening in order to avoid the occurrence of knee and ankle joint dysfunction and muscle contracture, in the course of treatment, it is necessary to provide patients with guidance on functional exercise, which includes the following: 1) Routine loading exercise is necessary to maintain the normal function of the joints and maintain the internal environment. In the process of limb lengthening, strengthen the functional exercise of active and passive flexion and extension activities of the joints; at the same time, the intermittent stress stimulation generated during limb activities has the effect of promoting bone healing. During the period of distraction lengthening, patients should be encouraged to carry out joint activities, with muscle isometric contraction, etc., supplemented by muscle massage and passive activities of the joints (CPM machine), in order to promote blood circulation, maintain muscle strength and normal mobility of the joints, and reduce the occurrence of complications. ② Assist magnetic therapy and medication to promote fracture healing, accelerate the healing of the osteotomy end, and remove the bone lengthener as early as possible. ③Tibia and fibula lengthening, especially in the process of large-scale lengthening, the patient’s knee and ankle joint mobility decreases, but through the functional exercise, the joint function can be greatly improved or restored. Exercise should be gradual, daily activities 3~4 times, 10~20 minutes each time, not fast and violent. 8, neurovascular injury in the early stage of the extension surgery, 2 weeks after the operation with a thin pillow will be slightly elevated leg, closely observe the blood flow of the distal end of the affected limb and toes, sensation, movement and wound drainage, etc., to facilitate the discovery of the limb’s nerves, blood vessel damage, since the seventh day after the operation, every day twisting the extender on the spreader screw, so that the extension of the 0,67 ~ 1,0mm, the extension of the rate depending on the patient to tolerate the situation. Observe closely to avoid blood circulation and nerve dysfunction of the limb due to excessive stretching. In the middle and late stages of the lengthening operation, the neurovascular lengthening is slower than the bone lengthening and is subjected to tension, if not handled properly, vascular and nerve injuries are likely to occur. In the treatment, closely observe the skin sensation of the affected limb, joint activity, arterial pulsation and peripheral circulation, and take timely measures when abnormalities are found, such as foot bruising, pallor, swelling can be judged to be a vascular crisis, remove the limb with or without compression, bandaging too tight, and other external factors, and report to the doctor to give the expansion of the volume, elevation of the affected limb, physiotherapy, massage, and in severe cases, incision and decompression. If the toe active activity loss, severe pain, numbness, sensory abnormalities can be judged as a neurological crisis, remove the limb with or without compression, bandaging too tight and other external factors, there is still no improvement should be taken into account to be slowed down to extend the speed of such as, if there is still no improvement, then stop prolongation, and even appropriate shortening. Usually can be relieved, but if the vascular nerve has been torn need to explore the repair. Another situation that should be noted is the prevention of direct damage to the vascular nerve when penetrating the steel needle. We believe that increasing the number of lengthening times appropriately in the middle and late stages of lengthening, 6~8 times/day, is beneficial to preventing complications of vascular nerve injury. Conclusion Bone lengthening (limb lengthening) surgery is complex, with many postoperative complications and high requirements for surgery and rehabilitation. In order to minimize the occurrence of postoperative complications, postoperative close observation of limb sensation, movement and blood circulation, accurate limb lengthening, guidance of functional exercise, and strengthening of the observation, prevention and treatment of complications is an important part of improving the quality of limb lengthening.