With the rapid development of spinal surgery, various internal fixation materials and methods have been introduced one after another, and spinal osteotomy has been promoted from simple correction of posterior convexity to lateral convexity, which has become increasingly difficult and extensive, raising new issues for surgical treatment methods aimed at correcting deformities. Surgery should not only be performed to correct spinal deformities, but also to consider how to minimize serious complications of surgery, such as spinal cord injury (even paralysis), nerve root injury, large vessel injury, and slippage due to spinal instability, in order to improve the patient’s quality of life. This means that the ideal surgical approach is to correct kyphosis to the maximum extent possible and effectively with safety in mind. This requires the surgeon to select the appropriate surgical plan based on factors such as the patient’s different types of kyphosis and spinal mobility. Hunchback deformity due to ankylosing spondylitis (AS) is a relatively common spinal disorder for which surgical orthopedic correction is the only effective treatment. The development of surgical methods reflects the state of the treatment level. The current surgical approaches to kyphosis correction at home and abroad are mainly divided into: simple accessory osteotomy; arch vertebral body osteotomy. The current evaluation of multiplanar arch vertebral body osteotomy is higher. However, we found that this procedure involves two adjacent vertebral bodies, including the intervertebral discs, in the process of osteotomy, which causes a lot of surgical bleeding and is prone to serious nerve root injury, and the problems of osteotomy angle and osteotomy distance are often based on experience and have not been solved. In summary, the main problems are: ① What is the safest osteotomy distance and angle? ②How to osteotomy less bleeding? ③Can aortic calcification be absolutely inoperable? ④How to operate on the complication of hip joint stiffness? ⑤ How to operate to reduce recurrence? The serious complications and the potential risk of their occurrence are still large, so that the promotion of the application of surgery is limited. For this reason, the authors conducted a review to improve and refine the new surgery for problems that are prone to occur, with a view to minimizing the complications of the current vertebral arch osteotomy and its opportunities to occur. I. Characteristics of ankylosing spondylitis hump: The treatment of ankylosing spondylitis hump has the following characteristics: the cause of ankylosing spondylitis is currently unknown, but it is related to immunogenetics, so there is no effective etiologic treatment, only symptomatic and combined chemotherapy to stabilize the disease. In most patients with stiff and severe spine, surgical orthopedics is an effective approach. This type of humpback is a large round back deformity, which provides a greater option for surgical osteotomy, and the disease provides a better pathological basis for multisegmental osteotomy. This means that a single osteotomy is not as effective as a multi-segment dispersed osteotomy for orthopedic purposes. Ankylosing spondylitis has extensive lesions involving the cervical spine. In some of these cases, it is difficult to use general anesthesia during surgery and requires a high level of anesthesia. The spine has bamboo-like changes, sclerosis of the ligaments, and calcification of the aorta. If epidural anesthesia is chosen, puncture is difficult and local anesthetic infiltration is not effective. Therefore, the choice of anesthesia is more important than other types of hunchback. In addition, the spinal sclerosis requires more vigorous efforts in the correction process to correct the deformity. Ankylosing spinal bone is thickened, and brittle, poor toughness, easy to fracture, internal fixation is more difficult, the spinal joint is blurred after calcification, such as the upper arch dowel, according to the normal positioning method, inaccurate positioning during surgery, which may lead to nerve damage or dowel penetration arch fixation instability. Such patients have different degrees of hip flexion stiffness, which directly affects the orthopedic effect of the hunchback. It is required to properly deal with hip flexion deformity before hunchback orthopedics. Patients with poor general condition, long-term hunchback deformity, compression of the heart, lungs, abdomen and other organs, often accompanied by varying degrees of anemia, heart block and decreased lung capacity, tolerate anesthesia surgery less well than the general population. And the surgery of hunchback correction is more traumatic, so the preoperative preparation should be carried out fully for their disease characteristics. Smith-Petersen first designed the “V” osteotomy of the lumbar spine to correct the kyphosis. The first spinal osteotomy was designed by Smith-Petersen to correct kyphosis. The most effective site for correction of kyphosis, the apex of the kyphosis, was attempted to be osteotomized at that time, but because kyphosis mostly occurs in the thoracolumbar or lower thoracic segment, which is the spinal cord segment of the spine, Smith considered this area to be off-limits for osteotomy and chose to make a wedge-shaped osteotomy of the posterior attachment of the spine in the lumbar space below the cone of the spinal cord for 1-2 gaps. The anterior longitudinal ligament and the fibrous ring are then ruptured, creating an anterior opening of the vertebral body, increasing the anterior convexity of the lumbar spine, and compensating for the erection of the posterior convexity of the trunk, turning the original “C” posterior convexity of the spine into a “3” type. The procedure is a pioneer in the surgical treatment of kyphosis, and it provides a solution to the patient’s pain. Because the basic principle is the compensatory correction of lumbar adnexal osteotomy, the osteotomy site and the number of osteotomies are not reasonable, which may cause a huge local pulling force on the large blood vessels in front of the lumbar spine, resulting in vascular tearing and life-threatening hemorrhage, and the intervertebral opening is unstable after spinal osteotomy, which may easily slip and cause spinal nerve injury. This procedure has poor orthopedic results, many complications, and high mortality. Lichtblau reported complications of up to 60% and mortality of up to 30%. In response to the above-mentioned surgical risks, many scholars made continuous improvements in the surgical method. However, it was not until the 1980s that significant results were achieved. One of the main advances in recent years is the improvement from accessory spinal osteotomy to combined arch and vertebral osteotomy, and the scope of adaptation of the combined arch and vertebral osteotomy varies widely, depending to some extent on the pathological characteristics of different types of hunchbacks. There are two categories. The secondary total spinal osteotomy, i.e., accessory osteotomy plus posterior vertebral osteotomy, is characterized by a bottom-to-back wedge-shaped osteotomy at the posterior aspect of the spine, generally removing the posterior 1/2-2/3 of the vertebral body. This approach increases the bony contact surface and spinal stability after osteotomy. Thomasen [4] was the first to report the surgical method of posterior compression of the vertebral body by scraping the cancellous bone of the vertebral body through the pedicle. Later, some scholars reported a periapical arch vertebral body osteotomy via the pedicle, which was improved to a multisegmental osteotomy, resulting in a greater degree of improvement in surgical outcomes. The authors analyzed the principle of multi-segmental vertebral arch osteotomy from a biomechanical point of view to reduce the chance of possible nerve root and spinal cord injury during surgery. Total spinal osteotomy: reported by Mcmaster M.J. and Tian Huizhong, the osteotomy includes the entire vertebral arch and vertebral body, forward to the anterior longitudinal ligament, and requires the removal of all the bone within the wedge, so that the spine is completely truncated, with 1-3 vertebral bodies above and below, leaving the spinal nerve roots free from the osteotomy surface. Closure of the osteotomy gap to correct the deformity and postoperative spinal stability are maintained by internal fixation devices. It is mainly applied to angular kyphosis and posterior scoliosis of the spine. Recurrence of kyphosis and posterior scoliosis after ankylosing spondylitis hump surgery is also indicated, but not arch kyphosis due to ankylosing spondylitis. The advantages are wide range of single osteotomy and large correction angle, but the surgery is traumatic and has potential spinal cord injury. 2, osteotomy limits: Based on animal tests and a review of the correction of kyphosis in ankylosing spondylitis, the authors conducted a prospective study of 118 patients with AS kyphosis who underwent multisegmental osteotomy correction with spinal shortening to explore the relationship between the limits of osteotomy correction and spinal cord function in ankylosing spondylitis kyphosis and to clarify the osteotomy limits for clinical kyphosis. The spine was shortened by 12-24 mm, and the pre- and post-correction X-ray vertebral osteotomy volume was also analyzed; intraoperative osteotomy volume, spinal cord deformation and spinal canal relationship were measured; changes in spinal cord function were observed with the arousal test. The difference between the amount of spinal osteotomy and the amount of spinal cord laxity and its influencing factors were also analyzed. The results showed that spinal cord relaxation could also cause spinal cord dysfunction. There were significant site differences in the amount of single-segment osteotomy in this group of patients, and the amount of single osteotomy was in the range of 9-16 mm in the T10-L1 segment; it was safer in the range of 15-24 mm in the L2-4 segment. The limit of osteotomy is also limited by the stability of the spine, the spinal cord vascular distribution, and the operation style. It is said that too large an osteotomy can cause spinal cord dysfunction, and it is generally said to be safer within 25 mm, which is consistent with the results of animal experiments. 3, the increase in the number of osteotomy segments (plane): the previous single-segment osteotomy, the correction angle is limited, and the increase to a certain extent prone to spinal slippage, the surrounding soft tissue overtraction and other serious complications. Wilson M, J had proposed multi-segmental osteotomy, which was limited to accessory osteotomy, and the radiographs showed that only one osteotomy had an orthopedic effect. In recent years, many scholars have done two or three vertebral arch osteotomies to make multi-segmental osteotomies have significant orthopedic effects. Three-segment osteotomies can correct posterior convexity above the COBB’S angle of 90b. The design of computer application software makes multi-segment osteotomy quick and standardized. 4.Improvement of the osteotomy plane: The apex of the posterior convexity of ankylosing spondylitis is mainly in the lumbar region, which is more common in the thoracolumbar segment and occasionally in the cervical and upper thoracic segments. The osteotomy site is generally best at the apex of the posterior convexity. In the past, it was thought that the spine above L1 was a forbidden area for osteotomy, because the osteotomy would easily cause paraplegia. In recent years, the operation style has been improved so that above L1 is no longer a forbidden area, and the original lumbar osteotomy has been raised to the thoracic and cervical segments. In the choice of surgery, the vertebral arch osteotomy can be used for those whose vertex of lordosis is below T10; for those whose vertex of lordosis is above T10, the thorax affects the closure of the osteotomy surface, multi-segment attachment osteotomy is used above T10, combined with the vertebral arch osteotomy below T10, so that the surgical trauma is small and the orthopedic effect is good, and the thorax can protect the upper thoracic spine from complications such as slippage. For cervical kyphosis, the vertebral artery stroke should be taken into account, and most scholars currently advocate the choice of cervical 7 osteotomy is safer. 5, multi-directional osteotomy: mainly refers to osteotomy orthopedic in more than two planes such as sagittal plane and coronal plane, ankylosing spondylitis hunchback is mainly posterior convexity, some patients are accompanied by mild lateral convexity deformity, currently proposed vertebral osteotomy, the bottom edge of the wedge to the most convex direction, the tip of the wedge points to the concave side, but also retain a little bone to maintain the continuity of the spine and prevent spinal displacement. Better results can be achieved. The problems and countermeasures frequently encountered in the hunchback correction surgery for ankylosing spondylitis: 1. Surgery for patients with hip ankylosis: When the hunchback and the hip ankylosis are aggravated by the hip flexion deformity, the upper part of the body, which has already shifted the center of gravity, further increases the stress on the spine and hip joint. In order to effectively and accurately correct the hunchback, restore the normal stress characteristics of the spine, and avoid complications such as excessive correction of kyphosis caused by the illusion of anterior tilt of the spine, insufficient correction of the angle of the hunchback, and recurrence due to anterior tilt of the spine after correction of the hunchback, it is necessary to perform orthopedic surgery on both parts. Since the longitudinal axis of the spine is tilted forward due to the ankylosis of the hip joint, the longitudinal axis of the spine must be made basically vertical in order to achieve more definite results in hunchback orthopedics. From the biomechanical point of view, it is reasonable to perform hip orthopedic surgery first and then correct the hunchback. Surgery for combined abdominal aortic calcification: Previously, abdominal aortic calcification was considered a contraindication to surgery because of the strong longitudinal pulling force during surgery, which could easily cause injury to large blood vessels. The current procedure has been improved to avoid excessive longitudinal strain during spinal orthopedic procedures. The authors have operated on 41 patients with abdominal aortic calcification and no complications of large vessel rupture occurred. 2, the choice of internal fixation: for ankylosing spondylitis poor mobility, extensive calcification of the spine, there are three cases: ① calcification is serious, the structure is unclear, the accessory bone cortex calcification, while the bone marrow fat liquefaction, can not be used or the application of pedicle screws, CD, etc. prone to instability. When the spine needs to be fixed extensively during multi-segmental osteotomy, and CD rods are difficult to fix and generally not firmly fixed. It is recommended to use multi-segmental spine root padding wire and Luque rod internal fixation, which is simpler and easier. Especially when the lack of X-ray equipment and the inconvenience of applying pedicle screws and CD, it is more advantageous. ②In cases of mild calcification, the small joints of the spine are still recognizable. It is more stable to apply the pedicle screw system. ③ between the two, the application of hook and nail combination technology is better. 3, hemostasis: spinal osteotomy orthopedic process bleeding is extensive, large, and no well-known vessels can effectively stop bleeding. Hemostasis is always present throughout the surgery, so the hemostatic method should be serial. Preoperative application of hemostatic drugs to improve the coagulation mechanism; patient prone position, the abdomen as much as possible suspended, so that the abdominal pressure to reduce wound bleeding; anesthesia, you can use controlled hypotension (systolic pressure of about 10Kpa) to reduce wound bleeding; osteotomy procedures, you can first retain the peridural bone cortex to prevent premature destruction of the epidural venous plexus and the emergence of diffuse bleeding. 4. Prevention of spinal cord injury: Spinal cord injury is one of the more serious complications during hunchback correction, which directly affects the operation. Therefore, many scholars are very concerned about how spinal cord injury can be avoided. However, it is mainly closely related to the way and method of the osteotomy process. Exposure of the spinal cord: Some patients with humpbacked ankylosing spondylitis have a long history of sclerosis and adhesions to the vertebrae, so when separating the dura, it is better to start from the posterior midline on both sides where adhesions are less likely to occur and less likely to damage the spinal cord. The process of osteotomy should be performed under direct vision with instruments to protect the spinal cord and avoid touching and overstretching the spinal cord, otherwise the dura mater is intact and the spinal cord may be damaged by touching or stretching. In multisegmental osteotomy, prophylactic fixation of the osteotomized segment is feasible. This can prevent the spinal cord from being damaged by sudden misalignment during osteotomy of other segments. Order of osteotomy: It is best to perform osteotomy in a circular fashion, from the outside to the inside, layer by layer. SEP and MEP monitoring: In recent years, the monitoring of SEP and MEP in the process of spinal orthopedics has a greater practical value for early detection and reduction of spinal cord injury, combined with arousal tests can basically provide a reliable reference value for predicting and preventing spinal cord injury.