Spondylodiscitis is a most common spinal infection, which affects the vertebral bodies, intervertebral disk, paraspinal tissues, and also the posterior bony elements occasionally. Traditionally, conservative treatment including immobilization and systemic administration of antibiotics is the first choice for pyogenic spondylitis[19, 20]. Surgical treatment is indicated in patients with progressive biomechanical pain, refractoriness to antibiotic therapy, epidural abscesses, neurological impairment or segmental instability. Surgical intervention is recommended as it could relieve pain, maintain vertebral column balance, improve neurologic function, and bring higher quality life.
Debridement and reconstruction are two main principles of the surgical treatment of pyogenic spondylitis[23, 24]. The anterior approach provides direct visualization for radical debridement and decompression without affecting the posterior elements,which is the best way to control the infection and promote definitive healing, and it also can warrant adequate and strong reconstruction with modern instrumentation tools[10–12]. However, anterior surgery alone does not adequately correct kyphosis and could not bear physiological loads, the recurrence of kyphosis following it are difficult to treat[9, 25]. In order to overcome these limitations, some authors advocated posterior spinal stabilization and fusion. Posterior approach could give better kyphotic deformity correction and vertebral stabilization, less complications and less surgical invasiveness. Meanwhile, the infected intervertebral discs, vertebral endplates, and vertebral body tissues could be adequately debrided through a posterior-only approach to assure the excellence of the radiographic and clinical results[13, 15]. But a considerable portion of authors believed that the posterior-only approach has the drawbacks of insufficient removal of infected tissue compared with the anterior approach. Thus a combination of anterior debridement with posterior fixation is widely used for the treatment of lumbar pyogenic spondylodiscitis[14, 27–29]. Nevertheless, the combined approach increases the risk of morbidity associated with the prolonged duration of operation, anesthesia times, the additional blood loss and operative trauma.
Antibiotic-loaded cement (AIBC) is widely used to treat or prevent infections in total hip and knee arthroplasty because it can lead to a locally high antibiotic concentration. Nonetheless, burst release of antibiotics and microbial colonization of the non-degradable cement has led to advanced investigation for more antibiotic delivery. Calcium sulphate has a long history as antibiotic carrier material, which is a resorbable osteo-conductive scaffolds without requiring to be removed after implantation. It also can be mixed with heat-sensitive antibiotics because there is very little temperature rise on curing[17, 33]. The mechanical strength of CS is comparable to cancellous bone, and is hydrolyzed slowly in bone, lasting for about 6–12 weeks. The antibiotic-loaded beads demonstrated high bioactivity in preventing and eliminating the residual bacteria, with long periods of sustained efficacy. It's a good solution for the shortcoming of insufficient removal of infected tissue in the posterior procedure. The cement beads could be absorbed completely in about 8–12 weeks after surgery, and new bone gradually formed while antibiotics released to control the infection. The imaging examination showed the infected site healing well with no recurrence during the follow-up in our series. Percutaneous pedicle screw instrumentation was used to avoid unnecessary muscle dissection and tissue disruption, decrease blood loss and complications, provide immediate stability. Meanwhile, pedicle screws were inserted into the infected and adjacent vertebra to avoid decreasing mechanical stability by longer fixation levels.
Antibiotics targeted toward the causative pathogen appears to be the most important factor to determine the success rate of treatment. Identifying the causative pathogens is one of the key factors to achieve cure in our studies. Positive culture was obtained in 23 patients (72%) while Staphylococcus aureus is the most frequent pathogen (73%) in our studies. Systemic antibiotic treatment duration ranged from 6 weeks to 12 weeks, which was consistent with the previous literature description. Appropriate antibiotic therapy based on the causative pathogen is crucial and can lead to good clinical results. After sending blood culture and disc space aspiration, all patients immediately started empirical intravenous antimicrobial therapy. Then, an appropriate antibiotic was administrated according to the results of microbial culture and sensitivity.
Our data showed the pain was significantly relieved and the ODI index was significantly increased after surgery, all patients could return to normal life. The patients’ ESR and CRP levels decreased significantly 7 days after surgery and returned to normal in a mean of 4 weeks after surgery, indicated that inflammation indexes were well controlled. The CS antibiotic bone granules were absorbed in 2 to 3 months gradually, and the bony fusion was observed in all patients in a mean of 4.1 months after surgery. The Cobb Angle was significantly improved at 7 days post-op and last follow-up, and there was significant difference between the post-op angle and the final follow-up, which meant the Cobb Angle was maintained at the final follow-up with no kyphotic deformity aggravated compared with the post-op. All the 20 patients with preoperative dysfunction recovered to different degrees after operation, and the excellent and good rate reached to 94.4%.
However, this study also has limitations. The current study is a small-scale retrospective data analysis in a single institution, and there is no matching control group. We need a prospective controlled study and a large number of patients to identify the effectiveness of this technique in the future.