The surgical approach has been controversial since the beginning of surgical treatment for spinal tuberculosis [19, 22, 23], and the main issue is whether anterior surgery or posterior surgery should be used. Compared to anterior surgery, posterior surgery is easy to expose the lesions, which seems to be more advantageous. However, tuberculosis is usually in the anterior and middle column of the vertebral bodies, thus thorough debridement cannot be achieved by posterior surgery. “Thorough debridement” is of paramount importance in the treatment of spinal tuberculosis, thus direct anterior exposure and debridement are more suitable.
Due to the clinical specificity of spinal tuberculosis in T4-6 segments, the surgical treatment has become a challenge for spine surgeons. The treatment in T4-6 segments is different from spinal tuberculosis in the upper thoracic spines (T1-T3) as well as the mid-and lower thoracic spines (T7-T12). Tuberculosis in the T1-T3 segments can be debrided using lower anterior cervical approach that is familiar to surgeons, which can be combined with posterior surgery or be used alone for fusion and reconstruction . Tuberculosis in the T7-T12 segments can be well exposed and debrided by conventional anterior transthoracic approach [25–27]. However, for T4-6, the anatomical position is deep, the surrounding tissues are complex, and there are many bony occlusions, such as sternal manubrium, clavicle, ribs and scapula. Moreover, the vertebral body is adjacent to the large blood vessel, aorta, thoracic duct and nerve tissues. Therefore, it is difficult to expose the lesions using anterior approach, and the surgical risk is high. Meanwhile, patients with tuberculosis are usually combined with destruction of bone structures, leading to kyphotic deformity, furthering increasing the difficulty of anterior surgery.
For T4-6 segments, the current anterior surgical approaches can be applied include subscapular transthoracic approach, mediastinal approach with sternotomy, clavicular approach, transsternoclavicular approach, and approach by resection of the manubrio-clavicular complex, etc. [10, 14, 24, 28, 29]. Although these surgical approaches can directly expose the lesions, and “thoroughly” debride the lesions as much as possible, they have the disadvantages of complex operations, unfamiliar to the spine surgeons, high surgical risk, and more complications including shoulder dysfunction, as well as injuries of vital organs such as recurrent laryngeal nerves, phrenic nerves, aorta and thoracic ducts, etc. In the meanwhile, trauma of anterior surgery is large, damage to the pulmonary appendices is great, and it is prone to pulmonary infection, atelectasis, pneumothorax and pleural effusion after surgery . Thus, surgeons are extremely prudent to choose anterior approach for T4-6 segments due to the numerous shortcomings.
Multiple studies in recent years have demonstrated that posterior surgery is superior to anterior surgery for thoracic tuberculosis in reconstructing spinal stability and correcting kyphotic deformity. Meanwhile, anterior and posterior surgeries have similar cure rates for thoracic tuberculosis [6, 12, 17, 30]. Wu et al.  have conducted a retrospectively study for 394 patients with thoracic tuberculosis in 15 medical centers over 15 years. In their study, 73 patients undergo anterior surgery, 237 patients choose posterior surgery, and 84 cases use the combined surgery. The results have shown that clinical efficacy of posterior surgery alone is not different from anterior surgery as well as the combined surgery. Moreover, surgical time is short, and there is less blood loss in posterior surgery. In addition, posterior surgery is superior to anterior surgery in correcting kyphotic deformity and maintaining spinal stability. Li et al.  have conducted a comparative study for the efficacies between anterior and posterior surgeries among patients aged over 65 years who have tuberculosis in T5-T12 segments. Their study results have suggested that posterior surgery is superior to anterior surgery, especially for patients with poor physical conditions. Wang et al.  have conducted a systematical review for anterior and posterior surgeries in the treatment of thoracic and lumbar spinal tuberculosis recently. Their findings have shown that posterior surgery is better in correcting kyphotic deformity, and the pedicle system is used to compress the bone graft so that the bone graft is closely attached to the bone tissue after the focus is removed during the operation, which is conducive to fusion so as to obtain better spinal stability. In the present study, 67 patients were also treated with pedicle screw system to compress the anterior column reconstruction bone graft. All patients completed fusion during the follow-up period of 6–9 months, 81.48% of the patients with neurological impairment recovered completely, and the ODI score and VAS score increased by 77.10% and 81.70%, respectively. Our study results also confirmed the advantages of posterior surgery.
Compared to posterior surgery, an important purpose of anterior surgery is to “thoroughly debride the lesions”. Nevertheless, true thorough debridement cannot be achieved. Whatever surgical approaches cannot ensure that there is no Mycobacterium tuberculosis after debridement. Although posterior surgery is indirect debridement, it is also confirmed to be effective in debriding lesions in vital parts based on the main areas of spinal tuberculosis by the support of imaging examinations such as MRI and CT. Zhao et al.  have conducted a retrospective cohort study for 105 patients with thoracolumbar tuberculosis, and suggested that debridement via anterior or posterior approaches can effectively debride necrotic tissues surrounding the focus, and both of the two approaches have the same effects in debridement and curing ability of tuberculosis. Wang et al.  have analyzed 51 cases with thoracolumbar tuberculosis, and they propose that spinal tuberculosis can be cured by fixation and fusion via posterior approach alone but there is no need of debriding lesion in the anterior side under the support of effective anti-tuberculosis drugs, and anterior debridement may be unnecessary. In our study, posterior debridement was performed for all patients. Rinsing with hydrogen peroxide was performed after debridement, and the surgical area was soaked in povidone iodine solution for 5min. At last, the lesion area and surgical area were rinsed using a small flushing gun and 3000ml of saline. After the process of debridement, there may still be Mycobacterium tuberculosis through posterior surgery, but most Mycobacterium tuberculosis was inactivated or washed away after the above treatments of rinsing and soaking, leading to better efficacy in posterior debridement. In our study, all the 67 patients obtained clinical cure, and there was no patient suffered from tuberculosis recurrence, confirming the effectiveness of debridement via posterior approach.
In our study, tuberculosis in T4-6 was put forward separately for the first time based on the clinical specificity of T4-6 segments, thus surgical treatment can be differentiated from other thoracic vertebrae (T1-3 and T7-12). This study focused on investigating the effectiveness and advantages of posterior surgery alone. However, this study had the disadvantage of small sample size. We believed that studies with large sample size, multi-center studies and even completely randomized studies would be performed in the future, which would be of great clinical significance for the treatment strategy of tuberculosis in T4-6 segments.