Ankylosing Spondylitis (AS) is a rheumatic immune disease that mainly affects the spine and involves the sacroiliac and peripheral joints. The incidence ratio is 7:1 to 10:1 for men and women. the onset of the disease is mostly in men aged 15 to 30 years old, and is rare in children and people over 40 years old. orthopedic department of Beijing 301 Hospital Zheng Guoquan Ankylosing crestitis back pain and discomfort and motor dysfunction are mostly caused by lumbar spine joint lesions. The pain is diffuse in the back at first, and then gradually concentrated in the lumbar region. Sometimes severe lumbar ankylosis may occur, and patients may even refuse to bend, stand or turn for fear of pain. Patients with ankylosing crestitis whose crests are not fully fused typically have symptoms that are worse when they are fixed in a certain position for a long time or when they wake up in the morning (“morning stiffness”), which can be improved by somatic activities or hot baths. Progressive upward progression of ankylosing crestitis can also involve the thoracic joints. Upper back pain, chest pain, and a sense of restricted thoracic expansion and movement may occur. Tenderness can be induced by finger pressure on the sternal stalk-sternal body joint, the rib and rib cartilage junction, and all thoracic vertebrae. As the disease progresses, there may be significant crestal kyphosis and limitation of thoracic movement. In the advanced stage of ankylosing crestitis, the main manifestation is crestal fixation and ankylosis. Individuals may become severely disabled, bedridden, and unable to care for themselves for long periods of time. Ankylosing crestitis can lead to typical crestal deformities, such as fixed anterior cervical tilt, increased thoracic lordosis, and deformed thoracolumbar lordosis and loss of anterior lumbar lordosis. Sagittal imbalance of the crest can cause the patient to be unable to lie flat, have difficulty walking, and be unable to see horizontally with both eyes, and in severe cases can cause a decrease in cardiopulmonary and digestive function. In order to compensate for the forward shift of the center of gravity of the body, the patient often adopts a posture of flexion of the ankle and knee joints and hyperextension of the hip joints, resulting in high energy expenditure and easy fatigue of the patient. The kyphosis, which occurs in the neck, can also lead to swallowing difficulties. Typical case: Patient Zhou, 33 years old, had ankylosing crestal kyphosis for more than 10 years. He had difficulty eating every day, poor digestion, limited hip movement, and resting flat on his back was a luxury. Pre-operative X-ray showed severe kyphosis. Pre-operative CT 3D reconstruction showed that the whole crest was completely deformed and fused, and there was also pseudo-joint formation at the lumbar 12 intervertebral disc.