The ulnar nerve is caused by compression at the elbow, often secondary to chronic injury to the elbow, with progressive intrinsic hand muscle atrophy and numbness on the ulnar side of the hand as the main manifestation of the clinical symptoms, also known as delayed ulnar neuritis, traumatic ulnar neuritis, ulnar nerve palsy. Etiology: 1, elbow valgus, humeral condyle fracture or humeral epiphysis injury in early childhood can occur elbow valgus deformity, when the ulnar nerve is pushed to the medial side to increase tension, this is the most common cause. 2, ulnar nerve subluxation, congenital ulnar nerve groove is shallow or the fascia and ligament structure at the top of the elbow canal is relaxed, the ulnar nerve tends to slide out of the ulnar nerve groove when flexing the elbow, this repeated slippage makes the ulnar nerve suffer from friction and collision and injury. 3, fracture of the internal epicondyle of the humerus, such as fracture block downward displacement, can compress the ulnar nerve. 4, traumatic ossification, the elbow joint is the most vulnerable to traumatic ossification myositis, such as elbow trauma after this ectopic ossification occurs in the vicinity of the ulnar nerve groove, is also a cause of compression of the ulnar nerve. 5, other, long-term flexion of the elbow work, medical factors caused by the card pressure, occipital elbow sleep caused by “sleep paralysis”. Symptoms and signs: In the early stage of the disease, patients often feel numbness and discomfort in their little finger. Sometimes they have difficulty writing or using chopsticks. When the symptoms worsen, the ulnar carpal flexors and the deep flexors of the ring finger and little finger become weak, the intrinsic muscles of the hand atrophy, and mild claw-shaped finger deformity appears. Diagnosis: Specialized hand surgery, electromyography can help to make a clear diagnosis. Treatment: Conservative treatment is indicated in the early stages of the disease, when symptoms are mild. Posture adjustment of the arm, prevention of prolonged hyperflexion of the elbow joint, avoidance of sleep with the elbow in the pillow, and wearing an elbow brace may be indicated. Non-steroidal anti-inflammatory and analgesic drugs may occasionally relieve pain and numbness, but steroid hormone closure in the elbow canal is not recommended. Surgical treatment is indicated for intrinsic hand muscle atrophy, where conservative treatment is not effective. The following surgical procedure is commonly used: the ulnar nerve is uncoupled from the ulnar nerve sulcus and moved subcutaneously to the anterior elbow. The ulnar nerve is moved forward with adequate freeing to the distal and proximal ends, and the articular branch of the nerve and one or two muscle branches need to be cut to facilitate displacement to the anterior elbow to prevent intramuscular entrapment after displacement. A piece of deep fascia is lifted at the beginning of the flexor muscle to control the displaced ulnar nerve in the anterior part of the elbow to prevent the displaced nerve from slipping back to its original position when the elbow is extended. The flipped deep fascia should be of a certain width and length to prevent the formation of a new entrapment of the ulnar nerve. Interfascicular release of the nerve bundle is generally not advocated, as it may aggravate the symptoms. Postoperatively, a plaster brace in the flexed elbow position is braked, and practice activities are started after 3 weeks. Other surgical methods are not very popular, although they are also clinically used. Surgery: Elbow ulnar nerve release anteriorly requires brachial plexus anesthesia, and the release anteriorly is divided into two types: subcutaneous anteriorly or deep anteriorly. Postoperatively, a cast in the flexed elbow position is required for 2-3 weeks. Prognosis: Pre-operative intrinsic hand muscle atrophy is poor. The results are good if ESP can be measured in the elbow before surgery and poor if there is no ESP. Intraoperative degeneration of the intraneural fibers was seen with poor postoperative results. Prolonged duration of symptoms is also a sign of poor prognosis.