I. Concept of complications Concept of complications: When using medical technology for treatment, pathological symptoms derived from their own pathological development or difficult to avoid in the course of treatment as required by the technical operation specifications, namely complications. They are characterized by: 1. having a clear cause. 2. There is a certain causal relationship (direct or indirect) with the primary disease. 3, co-existing with the primary disease. 4, technical operation in accordance with the premise of medical technical operation requirements, unavoidable. Second, the classification of complications 1, reversible complications (1) mild: refers to only general surgical treatment can be cured or self-recovery, without surgical treatment of the problem, such as pinhole infection, extender steel needle breakage, bone and joint deformity, such as angular deformity, mild foot drop, abnormal sensation, etc. (2) Moderate: problems that require systemic medication or simple surgery to heal, such as incomplete osteotomy, severe pinhole infection, delayed healing, common peroneal nerve conduction dysfunction, poor new bone growth, delayed healing, deformed healing, low patella, etc. (3) Severe: It refers to problems that require comprehensive treatment measures or reoperation to resolve, such as reversible complications like calf fascia syndrome, joint dislocation or subluxation, joint stiffness, bone discontinuity, bone defect, re-fracture, venous thrombosis, fat embolism and length loss of 5% or more. 2, irreversible complications (sequelae) (1) mild: such as hip, knee, ankle cartilage damage, osteoarthritis and nerve damage caused by partial dysfunction of the limb. (2) Moderate: loss of muscle strength and joint function of the affected limb due to severe nerve, muscle and vascular injury. (3) Severe: amputation of the affected limb, such as limb necrosis caused by major vascular injury, such as extensive soft tissue necrosis of the limb caused by severe calf fascia syndrome, etc.