I. Pathological characteristics of thoracic spine tuberculosis The incidence of thoracic spine tuberculosis in the spine is as high as about 39.6%, especially in children. Due to factors such as negative thoracic pressure, mediastinal organ pulsation, complex structures adjacent to the thoracic outlet and physiological lordosis of the thoracic spine, thoracic spinal tuberculosis is prone to the formation of paravertebral and other abscesses, and the range of thoracic paravertebral abscesses is usually more extensive, with an incidence of 86.5%~98.5% reported in the literature. Superior thoracic spine abscesses can compress the esophagus and trachea in the upper thoracic orifice causing dysphagia and respiratory distress. Middle thoracic spine abscesses may protrude along the intercostal space or locally to the body surface, and may also form tension abscesses that penetrate into the lungs (about 10.9%), and the abscess and dead bone may be coughed up or penetrate into the lungs (3.3%), or may protrude backward into the spinal canal and cause spinal cord compression. Inferior thoracic and thoracolumbar TB abscesses may protrude from the body in the supragluteal and infragluteal triangles, or they may flow along the lumbaris major muscle into the iliac fossa and then descend into the thighs. The thoracic spine tuberculosis, like other spinal tuberculosis, predominantly destroys the anterior and middle columns of the spine, and because of its own physiological lordosis, the stress is concentrated on the anterior side of the vertebral body, causing collapse of the vertebral body after weight-bearing, resulting in a very pronounced lordosis. Diagnosis of thoracic spine tuberculosis (a) clinical manifestations: insidious onset, often manifested as continuous pain in the thoracic back, which may radiate to the chest and abdomen. The thoracic vertebrae gradually become deformed, and those with spinal cord compression may have lower limb pain, numbness, weakness, unstable walking, dysbiosis, or even paraplegia. It is also accompanied by tuberculosis toxicity symptoms, such as poor numbness, weakness and low fever and night sweats. Upper thoracic spine tuberculosis may cause dysphagia and dyspnea due to abscess compression of the esophagus and trachea. Those with pleural effusion may have cough, chest tightness and dyspnea. Signs include: posterior or lateral convexity deformity of the thoracic spine, local pressure pain, percussion pain, and in cases of spinal cord compression, sensory impairment below the lesion site, weakened muscle strength of the lower limbs, hyperactive tendon reflexes and positive pathological signs. Upper thoracic spine tuberculosis may have cervical abscess and limitation of cervical movement, and lower thoracic spine tuberculosis may have upper lumbar triangle abscess and limitation of lumbar movement. Posterior convexity deformity (34.8%) is the most common cause of first diagnosis in children; common symptoms include lower limb symptoms (50.7%), including lower limb weakness and gait instability; common signs include posterior convexity deformity (92.8%), which may be accompanied by systemic symptoms such as night sweats, low fever, poor appetite, lethargy and nocturnal cries. (B) Laboratory tests: elevated blood sedimentation, C-reactive protein, normal white blood cells, normal or high lymphocytes, and may be accompanied by anemia. The positive rate of intraoperative pathological antacid bacillus staining for finding antacid bacillus is 10%~51.7%, and the positive rate of antacid bacillus culture of pus is higher, 30%~82.8%, and drug sensitivity and drug resistance gene detection can be performed at the same time. Pathological histology has a very high positive rate, showing tuberculous granulomas containing giant cells of Langhans and foci of caseous necrosis. PCR methods have a positive rate of over 50% for detection of Mycobacterium tuberculosis, but cannot identify old or fresh tuberculosis infection. Tuberculin can be used for the differential diagnosis of spinal tuberculosis. (C) Imaging examination 1. Ultrasound examination can detect paravertebral abscess, lumbar muscle abscess, and pleural effusion; 2. X-ray examination can show active tuberculosis, vertebral body sclerosis, destruction, intervertebral space narrowing, fusion, widening of paravertebral shadow, and thoracic vertebral lordosis or lateral convexity deformity. However, due to the influence of the ribs, the thoracic spine tuberculosis is not as clear as the cervical and lumbar spine tuberculosis; 3. CT examination can show the destruction and sclerosis of the vertebral body and accessory bones, destruction of the intervertebral disc, narrowing of the intervertebral space, formation of dead bone, paravertebral abscess, abscess in the spinal canal or compression of the spinal cord by dead bone. MRI is important for the early diagnosis of thoracic spinal tuberculosis. It can detect early inflammatory edema and destruction of vertebral body, destruction of intervertebral disc, paravertebral and intravertebral abscess, clearly show spinal cord compression, and also early detection of adnexal tuberculosis. However, MRI does not show the size and extent of dead bone as clearly as CT. The treatment of thoracic spinal tuberculosis is the same as the treatment of other parts of the spinal tuberculosis, and the most crucial is the anti-tuberculosis drug treatment, which should be based on the principles of early, appropriate, regular, combined, and whole process. The aim of surgery is to decompress the spinal cord, stabilize the spine, correct the posterior convexity deformity and prevent aggravation of the deformity. The stability of the thoracic spine is better than that of the cervical and lumbar spine due to the protective effect of the thoracic support. However, because the spinal cord in the thoracic spinal canal is less tolerant of abscess compression than the cauda equina in the lumbar spinal canal, the requirements for spinal decompression are higher. These two factors lead to the fact that the indications for surgery for thoracic spinal tuberculosis are still controversial. Abhay Nene et al. treated 70 patients with thoracic spinal tuberculosis with conservative antituberculosis drugs, 44 with abscess formation, including 21 epidural abscesses, and 7 with spinal cord compression symptoms. His indications for conservative treatment were: (1) no significant neurological impairment (Medical Research Council grade below 3); (2) no worsening of neurological impairment during conservative treatment; (3) clear diagnosis; and (4) posterior convexity deformity less than 40°. After a mean follow-up of 40 months, 98% (69/70) of the patients were satisfactorily treated conservatively without residual instability or neurological symptoms, an excellent rate of 74%. 23% had residual kyphosis but no biomechanical instability. He concluded that conservative treatment of thoracic spinal tuberculosis was effective in the majority of patients and that only a minority of patients required surgical treatment. Rajasekaran et al. showed that patients with a 30° kyphosis of the thoracic spine without effective treatment develop a kyphotic angle of 50° to 73° within 10 years. Surgical internal fixation treatment not only completely removes the lesion and promotes the patient’s recovery, but also corrects the kyphotic deformity and prevents loss of the corrected angle. The indications for surgery for thoracic spinal tuberculosis are: large abscess and dead bone formation, posterior convexity deformity greater than 30°, spinal cord compression symptoms, and non-operative treatment is ineffective, but early surgery should be performed for patients with incomplete or paraplegia. The surgical choice of thoracic spinal tuberculosis and its advantages and disadvantages The surgical choice of thoracic spinal tuberculosis can be based on the site and extent of the lesion and the patient’s general condition, and can be performed by intrathoracic extrapleural lesion removal, transthoracic lesion removal, extrapleural transcostal transverse process lesion removal, posterior fixed phase I or phase II anterior transthoracic or extrapleural lesion removal, and upper thoracic segment tuberculosis sternal stalk or sternal split access lesion removal. (A) Transthoracic extrapleural lesion removal and internal fixation with bone graft fusion is suitable for those who have poor systemic status or pulmonary function and are not easy to operate openly, and the lesion is located in T4-12. The advantages are less trauma, faster postoperative recovery, no need to place closed chest drainage, and no common complications of open chest. The disadvantages are that the pleura is easily torn during surgery, inadequate exposure, restricted operation, and incomplete spinal cord decompression. Because of the small upper thorax and poor rib elasticity, the extrapleural approach with rib removal in the upper thoracic segment is not well exposed. (b) Transthoracic lesion removal and internal fixation with bone grafting is mainly used for patients with active or stable tuberculosis combined with mild to moderate spinal deformity, patients in good general condition, patients whose pulmonary function requires that the measured value of maximum ventilation is more than 50% of the predicted value, and patients’ lung X-ray, and the side with poor pulmonary function is selected as the operation side. For T1-4 tuberculosis a scaphoid retraction approach with resection of the 3rd rib is used, and for T4-12 tuberculosis a standard open chest approach is used. This procedure can be completed within the same incision, with complete removal of the lesion under direct vision and adequate decompression of the spinal canal, shortening the operative time and reducing blood loss, while achieving correction of the retroflexion deformity and stabilization of the spine. For severe deformities, thoracic collapse and aggravation of kyphosis can be stopped by intervertebral support implants, but the deformity correction effect is poor, so this procedure is generally not used alone for the treatment of severe rigid kyphotic kyphosis. Posterior convexity deformity involving the upper thoracic spine is very difficult to operate anteriorly. When the destruction of the vertebral body exceeds 50%, this procedure can only be used to lengthen the fixed segment, otherwise it will lead to loosening of the internal fixation. (iii) Extrapleural transverse costal process access for lesion removal and fusion with bone graft for internal fixation In 1954, Capener described the posterior resection of the transverse costal process, peeling off the wall pleura, and extrapleural access to the posterior aspect of the spinal vertebrae for biopsy, abscess drainage, and resection of certain tumors. This procedure is suitable for patients with T1-12 tuberculosis, where the lesion is located mainly on the lateral posterior aspect of the vertebral body, or for elderly patients with poor physical fitness. Its advantages are: (1) the lesion removal and bone grafting and internal fixation are completed in a posterior stage without opening the chest, which is less traumatic; (2) posterior three-dimensional internal fixation with pedicle screws and intervertebral bone grafting can effectively rebuild the stability of the spine; (3) combined internal fixation of the diseased vertebrae can reduce the incidence of degeneration of adjacent segments due to excessive fixation of normal segments. The disadvantages are: not as clear as transthoracic lesion removal, easy to damage the spinal cord and pleura, and poorer lesion removal and support bone grafting under direct vision, unless more than two transverse costal joints are removed. (d) Posterior fixation of phase I or phase II anterior transthoracic or extrapleural lesion removal and bone graft fusion internal fixation This procedure is suitable for the following cases: (i) those with severe lesion destruction or more than 3 segments, which are not suitable for installing anterior internal fixation; (ii) those with severe posterior convexity deformity requiring correction; (iii) those who have failed in anterior surgery and have difficulty in installing anterior internal fixation again. After posterior fixation and fusion, a stage I or II anterior transthoracic or extrapleural lesion removal will be performed according to the general status of the patient. For patients with poor systemic status or pulmonary function, extrapleural lesion removal can be used, otherwise transthoracic lesion removal is used, and the indications are the same as those for transthoracic lesion removal. The advantages are: (1) the scope of fusion can be reduced by nailing the diseased vertebrae, and the use of the pedicle nail can achieve orthopedic and fixation effects that are difficult to achieve with vertebral nails; (2) for multi-segmental vertebral tuberculosis, the method of posterior fixation and anterior segmental bone grafting is more stable than anterior long-segmental bone grafting, which can avoid the disadvantages of displacement, fracture and low fusion rate of the internal fixation and bone graft. Rajasekaran reported that the fusion rate of implants with more than 2 vertebral segments was only 35%. (E) Sternal stalk or sternal split approach for TB in the upper thoracic segment with lesion removal and internal fixation with bone graft fusion is suitable for T1-4 TB, with clearer exposure than the scaphoid retraction approach with resection of the 3rd rib and no postoperative complications such as limitation of scaphoid movement, in which the sternal stalk split approach is less traumatic than the full sternal split approach. In conclusion, the choice of surgical plan for thoracic spine tuberculosis should be based on the principle of individualized treatment and comprehensive consideration without bias. A reasonable chemotherapeutic regimen of antituberculosis drugs remains the key to the treatment of spinal tuberculosis and is also a guarantee of successful surgery.