The pathological basis of LBS is chronic degeneration of the intervertebral disc and vertebral bone destruction, and intractable back pain as the main clinical manifestations [15]. Intervertebral space stenosis is the common presentation of radiography, which presents in 32 patients (58.1%) in this study. In the view of anatomy, the intervertebral joint is the stress concentration area behind the spine, which may be easily affected by intervertebral space stenosis. If the anti-Brucella therapy is not intervented timely, the joint degeneration can be accelerated by increasing the joint contact, which brings about the proliferation and hardening of the articular surface. Then, the biomechanical structure stability of the intervertebral joint and spine sagittal balance may be destroyed. Via published studies [16–18], the phenomenon that invasion of the synovium and cartilage surface of joints by Brucella is more common. Posterior joint destruction combined with disc degeneration may bring about vertebral slippage. On that occasion, intractable back pain may be worsened by spine sagittal imbalance and severe vertebral slippage, as well as the corresponding manifestations of nerve damage. Fortunately, the velocity of infiltrative bone destruction in Brucella infestation is slow, and bone repair has been performed simultaneously while bone destruction occurs, which means sequestrum is not easily formed [17, 19]. Hence, the preservation of the vertebrae's structural morphology is a special character of LBS, which is different from spinal tuberculosis [19]. Hence, the spinal stability of patients with LBS is usually better than that of spinal tuberculosis. For instance, that's why kyphotic deformity is rare among patients with LBS.
Blood culture remains the gold standard for diagnosis of Brucella infestation, especially for patients who have ingested contaminated dairy products or come in contact with infected animals [1, 3]. Yet, the sensitivity of blood culture depends on several factors, especially the disease phase and previous antibiotics usage. In the acute phase, the sensitivity of blood culture may be more than 80%, while for patients with chronic infestation, its sensitivity is approximately 30% -70% [20]. Despite Although the population is generally susceptible to Brucella, most of the clinical symptoms can be effectively relieved by prompt and standard antibacterial chemotherapy [21, 22]. The indications and timing of surgical intervention are still controversial. But the current recognition is that the surgery should be prepared for patients whose Brucella poisoning symptoms cannot be effectively improved by anti-Brucella therapy (6 weeks of medication and 1 week of drug withdrawal), and combined with one of the following symptoms [7, 23, 24]: paravertebral abscess or psoas abscess; intervertebral disc destruction; spinal structure instability; accompanied by other bacterial infections. The purposes of surgery are radically removing the lesion, improving the local blood circulation, relieving the nerve root compression symptoms, and restoring the spinal sagittal balance to promote the early limbs' function recovery.
At present, the surgical approaches mainly consist of the anterior approach, posterior approach, and combined anterior and posterior approach. The choice of approach should be based on the location of the spinal lesion, the degree of vertebral destruction and spinal nerve compression, and the surgeon's technical proficiency. It has been reported in the literature that posterior approach surgery alone is more practical for intraspinal granulation and abscess removal, which is more suitable for middle and posterior column lesions, especially for patients combined with intraspinal nerve damage. While the combined anterior and posterior approach is recommended for patients with perivertebral abscess, psoas abscess, or greater anterior column destruction [7]. Considering that paravertebral abscess combined with spinal nerve compression symptoms occurred in most patients (83.6%) in this study, the posterior surgery was performed, because of its less intraoperative damage to the nerve root and lower incidence of complications. According to Frankel's classification, the spinal nerve compression symptoms were improved from grade C/D to grade E in 53 patients (96.3%) at the final follow-up.
To our knowledge, anterior surgery has also been recommended by some scholars. However, this method not only requires high surgical techniques for the surgeon but also has the risk of damaging the iliac vessels and sympathetic nerves of the complex anatomy of the anterior lumbosacral spine. And the operation time and blood loss can be increased, since the placement procedure of internal fixation in the lumbosacral area. Yin et al. [25] reported a case series of 16 patients with Bucella spondylitis managed by anterior debridement, autologous bone graft fusion, and internal fixation, with a mean operation time of 237.4 min, and a mean intraoperative blood loss of 580.2 ml. In this group, the mean operation time was 138.7 min (range, 80 to 200 min) with a mean intraoperative blood loss of 215.4 ml (range, 60 to 370ml), which was significantly less than the Yin's study. Additionally, there was no back pain caused by iatrogenic, which confirmed the feasibility of posterior surgery.
Although the posterior surgery makes up for the lack of anterior surgery, the spinal sagittal imbalance caused by serious anterior column structure damage cannot be ignored. And the persistent nerve compression symptoms (back pain or numbness) may be brought out by the severe soft tissue adhesions. In the view of Brucella spondylitis character [1, 6], the intervertebral space and the upper and lower endplates of adjacent vertebral bodies are mainly involved, and the distribution of abscesses is relatively limited, which rarely exceeds the edge of the vertebral body. A large sample, a multicenter, retrospective comparative study published by Ulu-Kilic et al. [4] showed that the extent of paravertebral abscesses in thoracolumbar Brucella spondylitis generally did not exceed the upper and lower edges of the destroyed vertebral body. Some patients with nerve root compression symptoms caused by intervertebral discs bulging from intraspinal abscesses or swelling could also be relieved by prolonging the antibacterial chemotherapy period. Thus, the completeness of lesion removal should not be overemphasized [23]. Chen et al. [8] reported that 24 patients with Brucella spondylitis were treated by one-stage posterior debridement, and autogenous bone graft using internal fixation, and satisfactory postoperative results were received. In this study, posterior surgery was managed for patients who met the criteria, and nerve compression symptoms were relieved in 53 patients (96.3%). The reason why two patients were not improved may be the irreversible nerve damage caused by chronic infestation history. In our experience, Brucella has low invasiveness of skeletal and existing standard chemotherapy regime, which means that early anti-Brucella therapy intervention plays an effective role in infestation control. Clinicians in the endemic area should become aware of and consider brucellosis in the differential diagnosis of febrile diseases with peculiar musculoskeletal, and patients could benefit from the timely and correct treatment to prevent the increased medical burden. However, as the spine sagittal imbalance occurrence is caused by the development of infestation, surgery cannot wait.
In this study, incision healing in all patients without sinus formation, infection recurrence, and pseudoarthrosis formation. ESR and CRP returned to normal levels at 3 postoperative months (P < 0.05). In the comparison of preoperative conditions, the pain symptoms and neurological dysfunction were relieved obviously (P < 0.05). In our opinion, posterior surgery was recommended for patients without neurological dysfunction. In this way, excessive damage to the structure of the posterior column of the spine can be avoided effectively, which allows a lower risk of injury to the sac and nerve roots intraoperatively and reduce the incidence of dissemination of infection further. Besides, for patients with neurological compression symptoms, the surgical approach was recommended to be selected for the severer side for hemi-spinal fenestration, and resection of the facet joint. After the completion of release on one side, the decompression was conducted on the other side. The decompression should be manipulated carefully to avoid the fracture of the contralateral lamina or excessive destruction of the facet joints. Similarly, it should be noted that patients with the base of the spinous process apposed closely to the sac should be meticulously separated using a nerve dissector when biting off the root of the spinous process.
Last but not the least, the results of this study may be affected potentially by several limitations, because of its retrospective and single-center nature. Firstly, there is no standardized surgical method for the treatment of LBS. Secondly, the efficacy of antibacterial chemotherapy cannot be underestimated. Hence, a prospective study of more samples and multi-center may do a great favor for the reconstruction of spine stability.