The common site of extra-pulmonary TB and the most severe form of osteoarticular TB is spinal TB, which is a widespread infectious disease problem in animal husbandry areas and developing areas [8, 20]. Because of its unique anatomical structure, the early symptoms of cervical TB are too tricky to notice. The neck and shoulder pain and discomfort of neck and shoulder occur first mostly. When the disease continues to develop, the posterior pharyngeal wall abscess is created slowly. The surrounding tissues, like the trachea and esophagus, may be compressed by this spreading cold abscess. The nerve root compression symptoms were caused mostly by the cold abscess posterior compressing. The anterior and middle columns of the spine are affected mainly by cervical TB, resulting in cervical kyphosis, neck stiffness, and neurological dysfunction caused by spinal cord compression. The single-level infections of the vertebral body are rare [6–8]. In this study, the lesions of patients with kyphotic cervical TB were concentrated mostly in the lower level of the cervical spine (C3 - C6). Involving more than two vertebral bodies occurred in all patients, who forming local kyphotic deformity. Typical cervical spinal cord compression symptoms were observed in 12 cases. The purpose of surgery is to decompress the compression symptoms of the spinal cord effectively, reconstruct the stability of the vertebral body, and restore the normal sequence in the sagittal position of the spine vertebral body.
The treatment published by a previous study of the early stage cervical vertebral TB was regular anti-TB chemotherapy and symptomatic treatment [8, 11, 16, 20]. But the long-term medication cycle and the increasing drug resistance, there is a great incidence of chance for the lesion to continue to the advanced stage, which may lead to progressive aggravation of spine deformity or vertebral body instability [22, 23]. For severe bone destruction and poor cervical stability after conservative treatment, surgical intervention is usually required. At present, the simple anterior approach of debridement and spine reconstruction surgery is a commonly used surgical method for the treatment of cervical TB, since the characteristics of simple approach, simplified procedure, removal of the lesion completely, and reliable structural reconstruction [1, 6–8, 24, 25]. The case series of 17 patients with cervical TB who were managed for the anterior approach of debridement and BGIF, were reported by Wu et al.  The bone grafting fusion of the vertebral body and improved neurological dysfunction were achieved. In this study, 18 patients of group A were treated by the anterior approach of debridement and BGIF, the sagittal sequence of the cervical vertebral body was corrected significantly. Briefly, the preoperative local Cobb angle was improved from 25.13 ± 8.28 ° to -9.74 ± 3.71 ° after surgery, the SCA was improved from 91.74 ± 8.96 to 80.16 ± 7.05 postoperatively, the C2-C7SVA was improved from 36.48 ± 10.35 to 11.65 ± 4.38 postoperatively. The patient's neurological recovery was satisfactory, and the neck and shoulder pain was relieved completely. It was recommended by us that the anterior approach of debridement and BGIF should be selected in the following cases: (1) the TB lesion eroded or destroyed the vertebral body slightly, and obvious cold abscess appears in front; (2) there was no obvious vertebral collapse, intervertebral space lesion, only slight infiltration of the adjacent vertebral body with no pedicle destruction; (3) patients with the poor physical condition. In these cases, the anterior approach of debridement and BGIF can achieve the purpose of lesion removal, stability reconstruction in one stage, without the need for a supplementary posterior approach of internal fixation to strengthen cervical vertebral body stability.
In the treatment of patients with severe vertebral destruction, collapse, or vertebral dislocation, combined anterior and posterior approach surgery should be considered to reconstruct vertebral body stability when the anterior approach surgery alone cannot achieve stability reconstruction [5, 12, 26, 27]. Combined anterior and posterior approach surgery (anterior approach of debridement or decompression combined with the posterior approach of pedicle screw fixation) is superior to only anterior approach surgery in biomechanical stability . However, a change of surgical position was required by combined anterior and posterior approach surgery, more damage was also brought to this procedure, included man-made injury to surrounding tissues, longer operation time, and more blood loss. So the indications for this procedure need to be strictly controlled since its higher risks compared with anterior approach surgery alone. In this study, 5 patients were treated by combined anterior and posterior approach surgery, and the spinal cord compression symptoms were relieved. The preoperative local Cobb angle was improved from 26.18 ± 9.93 ° to -11.05 ± 5.02 ° postoperatively. The SCA was improved from 98.76 ± 4.61 to 82.23 ± 1.13 postoperatively, and the C2-C7SVA was improved from 32.44 ± 4.24 to 11.52 ± 4.02 postoperatively. The cervical vertebral sagittal sequence was corrected obviously, without postoperative broken screws, rods, or internal fixation loosening. As far as we considered, the combined anterior and posterior approach surgery should be selected in the following cases: a) severe vertebral bone destruction with vertebral instability; b) severe vertebral collapse, with pedicle bone destruction, with the severe imbalance of the cervical sagittal plane. c) Severe erosion of adjacent vertebral bodies with unilateral or pedicle destruction. In the surgical procedure, one-stage posterior approach surgery aimed to fix and decompress, remove the vertebral plate and decompress the capsule indirectly, to reduce the risk of anterior approach surgery. In the process of anterior approach debridement, more attention should be paid to the extent of resection, the decompression should be performed effectively for compression area, and resection of the posterior longitudinal ligament. The scope of the contralateral resection depends on the invasion of the lesion. In principle, the uncovertebral joint should not be removed, and complete lesion removal and vertebral body structural support are more critical. In our cohort, complications occurred in 1 of 5 patients who underwent combined anterior and posterior approach surgery. The muscle strength of both upper limbs decreased from grade 5 to grade 3, with normal sensory function. After symptomatic treatment with neurotrophic drugs, the muscle strength returned to normal after 2 weeks.
The upper cervical spine is adjacent to important structures, such as the medulla oblongata and cerebellum, which makes the anatomy more complex. Especially in the treatment of vertebral artery variations and pedicle deformities, surgery is difficult and risky, because the intraoperative procedure leads to vertebral artery injury easily, and even respiratory failure and sudden death [27, 29]. The odontoid process and the C2 vertebral body are involved by TB of the upper cervical spine. The odontoid process is an important structure, which connects the upper cervical joint. Severe bone destruction of the odontoid process can be caused by TB lesions, which makes the atlantoaxial intervertebral space separated, let the atlantoaxial dislocation and atlantoaxial instability occurred, then local blood flow in the odontoid process is poor. Imaging examination shows the mild erosion and destruction of the odontoid process at the early stage of disease, which will cause ischemic necrosis of the odontoid process in the advanced stage, and cause pathological fracture of the odontoid process. Afterward, the neck movement is limited, and the C2 vertebral body is severely collapsed, which will cause the cervical spine structure to unstable. Multilevel bone destruction also occurs in some patients with upper cervical TB, and several of them will be taken to cervical coronal imbalance and cervical deformity. The surgical treatment of upper cervical TB focuses on focal debridement, spinal cord decompression, and reconstruction of cervical stability. Given the choice of surgical methods, oral approach surgery has been utilized by some scholars to treat upper cervical TB [30, 31], and satisfactory postoperative results have also been received. This procedure can enter the lesion directly with the minor traumatic incision. However, postoperative cervical stability is poor in the treatment of patients with severe bone destruction, vertebral collapse, and atlantoaxial dislocation. It is also prone to breakage or displacement of the internal fixation device. The scope of surgery is deep and narrow, which leads to a high incidence of complications, such as oral mixed infection, retropharyngeal abscess, laryngeal edema, and cerebrospinal fluid leakage. The anterior approach of cervical postpharyngeal debridement combined with occipitocervical fusion for the treatment of upper cervical TB was applied by Wang et al. [5, 27], and good postoperative results were obtained. The advantages of this approach are the simple anatomical structure, which exposes the vertebral body through the esophageal sheath and the carotid sheath reduces the risk of peripheral nerve injury. However, the limited cervical movement was caused significantly, which decreased the quality of the patient's life. Besides, in combined anterior and posterior approach surgery, the main difference lied in the posterior approach of fixation method, fixation and fusion procedure of the atlanto-pivot, and occipitocervical fixation and fusion. Xing et al.  concluded that under the premise of removing the lesion, short-segment internal fixation and fusion should be used as far as possible to maximize the preservation of a cervical range of motion and minimize the loss of cervical range of motion, which is an important principle. In this study, there were 4 cases of upper cervical TB, 2 patients were treated by interbody fusion, and 2 patients were managed by atlanto-pivot fixation and fusion.
The simple anterior approach surgery was managed for patients with mild destruction of the odontoid process, no atlantoaxial dislocation, good stability of the upper cervical spine, or whose C2 without obvious vertebral collapse, C2/3 intervertebral space lesions, only slight infiltration of adjacent vertebral bodies, and no C2 pedicle destruction. For patients with severe atlas bone destruction with atlantoaxial joint and atlantooccipital joint instability, severe odontoid bone destruction with atlantoaxial dislocation, C2 vertebral bone destruction with severe vertebral collapse with unilateral and pedicle bone destruction, and C3 vertebral bone destruction with severe vertebral instability of vertebral collapse, the combined anterior and posterior approach surgery was applied. According to the extent of lesion involvement and the degree of vertebral destruction, an individualized surgical plan and standardized anti-TB chemotherapy were prepared, then satisfactory postoperative outcomes were obtained in the treatment of upper cervical TB using both surgical methods.
Our study of debridement and BGIF with different surgical approaches in the treatment of patients with kyphotic cervical TB provided some valuable clinic experience. Limitations of this study should also not be ignored. First of all, there is no mature treatment algorithm for the resolution of kyphotic cervical TB. In addition, there is a lack of large case series with the complete postoperative of infected kyphotic cervical TB treated with anterior or combined anterior and posterior approach surgery (debridement and BGIF). Hence, a prospective study of more samples and multi-center is of more clinical significance.