Complications of extension-type supracondylar humerus fracture are divided into early and late stages, as follows: 1. Early complications are mainly nerve injuries, the first is radial nerve injury, which is more common clinically, mostly seen in the posterior inward displacement of the fracture end, usually temporary nerve palsy, appearing as dorsal extension of the fingers and wrist joints cannot be fully recovered; for patients with persistent radial nerve palsy for more than 3 months before considering the implementation of exploratory surgery; the second is The second is median nerve injury, which presents with numbness of the skin of the three half-fingers on the radial side and the palmar side of the forearm, mostly due to posterior displacement of the distal end of the fracture, sometimes accompanied by brachial artery injury; the third is ulnar nerve injury, which presents with numbness of the skin on the side of the little finger; ulnar nerve injury is less common in extension type supracondylar humerus fractures and more common in flexion type supracondylar fractures; extension type supracondylar humerus fractures with vascular injury and persistent consequences are very rare, and the clinician must be vigilant. The fourth is the osteofascial compartment syndrome, also known as 5P syndrome, in which the affected limb is painful, pale, without pulse, sensory loss and paralysis, and the pressure of the osteofascial compartment is >30 mmHg, which is an indication for incisional decompression surgery; 2, the late complications are joint stiffness, dysfunction, ossifying myositis, repeated forceful manipulation, and physiotherapy in rehabilitation training. The incidence of elbow entropion deformity is about 9%-58% in all supracondylar humerus fractures treated by closed reduction or plaster fixation, which mainly affects the appearance and has an impact on certain movements of the upper limb, such as throwing a curve ball in the lateral direction and pushing forward, and there is usually no effective method of non-surgical treatment, and surgical orthopedics is the only effective method to treat the deformity.