The pathogenesis of purulent spondylitis is mainly hematogenous infection with posterior trauma and local spread [5]. The main pathogenic bacteria of suppurative spondylitis are S. aureus [6] and E. coli [7], while other rare bacteria include Streptococcus, Pneumococcus, Salmonella, Pseudomonas, and Candida [8, 9].
The pathological features of suppurative spondylitis are primarily the coexistence of bone destruction with bone hyperplasia and sclerosis [10]. Clinically, it can be divided into acute phase, subacute phase, chronic phase and healing phase [3]. CSS is often misdiagnosed and missed due to its insidious condition and atypical symptoms and imaging, which is easily confused with spinal tuberculosis. In this study, 12 patients were diagnosed with spinal tuberculosis via imaging and symptoms before definite etiological diagnosis. They were treated with concurrent diagnostic anti-tuberculosis therapy, and 10 of them were treated effectively. This may be due to anti-tuberculosis treatment drugs containing rifampicin and levofloxacin, which are effective against some gram-positive and negative bacteria. Therefore, using diagnostic anti-tuberculosis treatment as a basis for the differential diagnosis of CSS and spinal tuberculosis should be treated with caution.
In addition to routine imaging and laboratory tests, new laboratory testing methods have been approved in recent years. the Xpert MTB/RIF assays have high diagnostic specificity for tuberculosis and is used as the basis for differential diagnosis discerning CSS and spinal tuberculosis. We have performed Xpert MTB/RIF assays on all samples from our department since June 2012 and the Xpert MTB/RIF assays results are highly consistent with disease test results. In addition, highly sensitive bacteriological detection can detect pathogens and can be used as an important diagnostic criterion. However, currently, this is not widely used due to the high requirements for specimen materials and the high testing costs. Currently, suppurative spondylitis has the following diagnostic criteria: (1) postoperative pathological biopsy; (2) percutaneous puncture biopsy bacterial culture; (3) blood culture (done at least twice); (4) local pain or neurological symptoms; (5) at least one imaging examination (X-ray, CT, MRI, or bone scan); and (6) laboratory tests revealing an acute inflammatory response (CRP > 30 mg/L, ESR > 30 mm/h, T > 38°C).A definite diagnosis must satisfy both (1) and (2), or (5) and at least one of (1), (2), or (3). The disease can be highly suspected if it satisfies both (6) and one of (1), (2), or (5). There is also the possibility of disease detection if (4) and one of (3) or (5) coexist. [11]
If patients have been clearly diagnosed, conservative treatment may be considered for patients with mild poisoning, tolerable pain, mild vertebral destruction, absence of deformity and kyphosis, segmentation stability, intolerance to surgery, and absence of paravertebral abscesses [12, 13]. The use of sensitive antibiotics is one of the main factors affecting treatment. If the efficacy of wide-spectrum antibiotics is poor, it should be adjusted over time and, if necessary, the department responsible for treating infections should be consulted to help adjust antibiotics. Sensitive antibiotics should be used once pathogenic bacteria are identified [14]. Most studies recommend intravenous antibiotics for 6–8 weeks, followed by an oral antibiotic treatment for 6 weeks [15–17]. Other studies show that IV antibiotics can be administered for 4–6 weeks until clinical signs and laboratory examination results return to normal, after which oral antibiotics can be continued for 6 weeks [18]. Later reexamination of CRP and ESR can monitor the developmental direction of the disease. Two patients in this group were treated conservatively: one was an aged patient with many basic diseases and the other had mild symptoms of poisoning and a mild degree of vertebral destruction.
Surgery is still the primary treatment for CSS. Currently, the general principles of surgical treatment are extensive and thorough removal of lesions, and the removal of all infected necrotic tissue or unhealthy bone [19]. Thorough removal of tissue that is vascularized during debridement is the key to successful surgery [20]. The procedure requires opening subchondral blood vessels to facilitate antibiotic delivery. Local instability or deformities caused by lesion destruction or removal need to be orthopedic or stabilized. Emergency decompression should be performed if complete paraplegia occurs. Surgical indications include 1) obtaining a bacteriological diagnosis when a non-open biopsy is unsafe or the result is negative, 2) presence of severe abscess symptoms, such as relaxation fever and sepsis, 3) poor effect of conservative treatment, such as sustained high ESR or no relief of pain, 4) nerve symptoms caused by spinal cord compression, and 5) obvious deformity or vertebral body destruction [21, 22].
One-stage surgery is generally recommended as the optimal operation timing. Some studies show that even if the patient is in acute infection stages but shows nerve compression symptoms, decompression and fixation in one surgical instance can also be performed. The hardware used for all patients is titanium screws and rods or plates, known as safe braking, for patients with ongoing active infections [23]. This material is chosen to deter organisms from colonizing the titanium material biofilm [24]. If the patient exhibits significant pain and spinal deformity, an orthopedic procedure can be performed following effective antibiotic treatment. Second stage surgery is only performed in patients of poor general condition or with inflammation in the acute phase, persistent high fever, or severe symptoms.
The current, primary debate is still the choice of surgical approach. This is mainly because lesions are often located in the anterior column of the spine and the intervertebral disc and vertebral body are the most common infection sites, while the posterior column of the spine is rarely infected. Therefore, anterior surgery is recommended [25]. After extensive anterior debridement, the anterior column of the spine loses its integrity and becomes potentially unstable, especially when multiple segments of the spine are involved. Therefore, surgical reconstruction is necessary to maintain sagittal balance and appropriate anterior column reconstruction methods are selected according to the degree and scope of vertebral body destruction. If lesions only colonize a single vertebral body of the thoracic vertebra, an autogenous bone graft of the ilium is usually sufficient. Nevertheless, the lesion site of the patient is primarily the lumbar vertebra or involves multiple vertebral bodies. Because autogenous bone graft is often difficult to accomplish, a combination of autograft and allograft is required. Further studies show that getting satisfactory operation results using autologous materials is difficult. Therefore, the titanium mesh is the proper choices, especially when the anterior column of patients has the more serious infection [26]. The advantage of this method is not only lower dosages of autologous bone block, but also its outstanding stability, ability to withstand greater pressure, and the simultaneous avoidance of bone resorption in autologous transplantation. Compared with autografts, we saw no postoperative infection or recurrent possibility with titanium mesh, and the bone fusion rate was almost 100% [25, 27]. Despite this, the anterior approach is highly complicated, so avoiding the anterior approach substantially reduces the risk of intraoperative complications. However, the anterior spinal column appears to be most at risk of subsidence. Therefore, some scholars determined the degree of segmental lordosis or kyphosis of the fused segments pre- and post-operatively using an adapted Cobb method. Interestingly, they observed only minor subsidence of 3.4° in instrumented segments, which is less than using a combined anterior and posterior approach with an autologous bone graft or titanium mesh cage and pedicle screw rod fixation [25]. Nevertheless, with long-distance screw-rod fixation alone, kyphotic deformities or preoperative signs of instability may increase the risk of implant failure [28]. The advantage of the posterior approach is that the exposure is low and the wound is small, so this method can clearly shorten the strict postoperative bedrest time [29]. However, due to incomplete debridement, this approach is only suitable for patients with accumulated disc lesions or a small amount of bone damage. In this study, 34 patients underwent surgical treatment, including posterior surgery in 20 cases (with second phase debridement in two cases), anterior and posterior combined surgeries in eight cases, and anterior surgeries in six cases. There were no significant differences in VAS and ODI scores among the three groups. We believe it is very important to choose the appropriate surgical approach according to the degree and extent of vertebral damage and abscess site. Total laminectomy is contraindicated for most patients, as it could accelerate infection and may aggravate spinal deformity in patients, thus leading to aggravated nerve compression. Laminectomy should be performed only in patients with primary epidural abscesses.
With the continuous development of spinal endoscopy and the improvement of the concept of minimally invasive, endoscopic surgery has been widely used in the treatment of lumbar diseases and has obvious advantages in the treatment of spinal infection [30]. This operation is an important complement to the traditional operation method. The puncture approach of endoscopic surgery is safe, which could avoid to damage the stability of the spine. Through the optical fiber video the operator could directly remove lesions and put accurate drainage tube to the focal center. With the most of inflammatory factor, pus, pathogenic bacteria had been removed by the physiological saline flushing during the operation, the intervertebral disc pressure was effectively reduced, and pain was obviously relieved [31]. Endoscopic surgery is suitable for the patients without severe kyphosis and nerve function damage, which is worth popularizing and applying.