Pyogenic spondylodiscitis of the spine is a rare disease, accounting for 1% to 7% of all cases of pyogenic osteomyelitis, although the incidence has increased further in recent years.1–4 Pyogenic spondylodiscitis of the cervical spine is much rarer than involvement of the lumbar and thoracic spines, composing 3% to 6% of cases of pyogenic spondylodiscitis of the spine.1,5–7 Therefore, studies on cervical pyogenic spondylodiscitis are scarce despite the ability of this disease to lead to severe neurological complications. In contrast with spinal infections in other regions, cervical pyogenic spondylodiscitis can be a more rapidly deteriorating process, leading to early neurologic complications.8 The risk of severe septic and neurological complications with cervical pyogenic spondylodiscitis is so high that it justifies urgent treatment.9
Although the preferred primary treatment of cervical pyogenic spondylodiscitis is a nonsurgical approach consisting of intravenous antibiotics and external immobilization,10,11 surgery is still required in selected cases in which signs of structural instability or neurologic deficit are present. The surgical management of cervical pyogenic spondylodiscitis involves debridement or decompression with or without instrumented fusion using anterior, posterior, or combination approaches. Instrumentations are thought to improve fusion rates and prevent the collapse and dislodgement of bone grafts and are routinely used to aid fusion in noninfectious cases. However, due to concerns about bacterial seeding on the foreign material after instrumentations in pyogenic infections, the safety and efficacy of anterior cervical plating for cervical pyogenic spondylodiscitis are still undetermined and controversial. To date, to our knowledge, no studies have performed to investigate the safety and efficacy of anterior cervical plating for anterior cervical debridement and fusion (ACDF) of cervical pyogenic spondylodiscitis. Therefore, we performed the current study to investigate this unsolved issue.
MATERIALS AND METHODS
This study was approved by the Institutional Review Board at all participating sites. We identified a total of 23 patients for possible involvement in this study, including 12 patients who underwent of ACDF with plating and 11 patients who underwent of ACDF without plating. Trained research staff at each site extracted relevant data from the patient medical records, surgical charts, radiology images, and other source documents. The data were transcribed into study-specific paper case report forms. All available data regarding demographics, levels of involvement, neurologic status, bone graft material, fusion status, isolated causative bacteriological organism(s), and perioperative or postoperative complications were extracted. The segmental height was checked to evaluate the subsidence of bone graft at the preoperative, immediately postoperative, and last follow-up time points. The segmental angle of the fused segment and C2–C7 angle were measured at the preoperative, immediately postoperative, and last follow-up time points (Figure 1). Also, fusion status was determined by a motion of less than 2° measured on flexion and extension lateral plain radiographs taken at the last follow-up,12 or computed tomography was performed to check the fusion status. The laboratory analysis of infection parameters included white blood cell count, erythrocyte sedimentation rate, and C-reactive protein level. The diagnosis was based on clinical symptoms, imaging findings, and laboratory data and was subsequently confirmed by the perioperative specimen culture results.
Indications for surgery included one or more of the following: severe destruction of endplates and vertebral bodies accompanied by local kyphosis and instability, paravertebral and/or epidural abscess formation, neurological deficit, instability associated with pain, and intractable neck pain despite nonsurgical treatments including intravenous antibiotics and rigid cervical brace. The operation consisted of anterior debridement or decompression using the microscope, gaining of specimens for bacterial culture and histopathological biopsy, and reconstruction of the defect with or without stabilization using anterior cervical plating. The bone graft material was primarily a tricortical bone graft obtained from the patient's iliac crest; nine patients in the ACDF with plating group and 11 patients in the ACDF without plating group received a tricortical iliac bone graft, while three patients in the ACDF with plating group received a titanium cage plus cancellous iliac bone graft. All plates used were made of titanium.
Postoperatively, all patients were treated with intravenous antibiotics (selective antibiotics according to the sensitivity found in the specimen cultures; empirical in cases of no culture growth) for 4 to 6 weeks and subsequently with oral antibiotics until the infection parameters returned to normal limits. The duration of antibiotic use was determined by physicians of the Department of Internal Medicine who specialized in infectious diseases at each hospital. A rigid cervical brace was applied after surgery and maintained for 12 weeks.
Data were analyzed using the SPSS Windows ver. 18.0 software program (IBM Corp., Armonk, NY) and are presented as means ± standard deviations. The paired t test and chi-squared test were used for statistical analyses. A P value <0.05 was considered significant.
The mean age of the 23 patients enrolled in this study was 62.6 years (range, 45–79 yrs), with 19 males and four females. Severe neck pain was a main clinical presenting symptom in 18 patients; five patients had neurological deficits (Table 1). The number of involved levels was one in 16 patients, two in six patients, and three in one patient. The most commonly affected levels in this study were C4–C5 (10 patients; 43.5%), C5–C6 (seven patients; 30.4%), and C6–C7 (five patients; 21.7%). The mean follow-up period after surgery was 21.3 months, including 28.0 ± 17.6 months for ACDF with plating and 14.5 ± 6.7 months for ACDF without plating (Table 2).
The overall radiological outcomes are shown in Table 3. One patient with ACDF with plating died due to a medical problem unrelated to the surgery at 2 months postoperative, so we excluded his data from statistical analyses of radiological outcomes. After ACDF with plating, segmental height, segmental angle, and C2–C7 angle were significantly improved compared with preoperative and were well-maintained at the last follow-up (Figure 2A–C). Conversely, after ACDF without plating, segmental height, segmental angle, and C2–C7 angle were also improved compared with preoperative but thereafter significantly deteriorated to preoperative levels at the last follow-up (Figure 3A–D). The fusion rate was higher in ACDF with plating (10/11 patients) compared with ACDF without plating (7/11 patients) (90.9% vs. 63.6%; P < 0.01). One patient who received ACDF with plating and four patients who received ACDF without plating underwent revision surgery due to bone graft dislodgement or nonunion.
The causative bacteriological organism was identified in nine patients. In five patients, Staphylococcus aureus was identified, while Staphylococcus epidermidis was identified in one patient, Escherichia coli was identified in two patients, and Prevotella melaninogenica was identified in one patient, respectively. No microorganism growth through intraoperative specimen culturing was noted in 14 cases (Table 4), which was assumed to be due to the patients having previously used antibiotics at other hospitals before transfer. No recurrence of cervical pyogenic spondylodiscitis occurred in either group.
In the current study, we reported that, after ACDF with plating for cervical pyogenic spondylodiscitis, segmental height, segmental angle, and C2–C7 angle were significantly improved compared with before treatment and remained well-maintained at the last follow-up. Separately, after ACDF without plating, three radiological parameters were also improved compared with preoperative, but deteriorated to preoperative levels at the time of last follow-up. The fusion rate was significantly higher in the ACDF with plating group versus the ACDF without plating group. No recurrence of pyogenic spondylodiscitis occurred in either group. Based on our findings, we recommend the use of anterior cervical plating, which can provide biomechanical stability, for better healing in cases of cervical pyogenic spondylodiscitis.
The aging of the population, intravenous drug use, immunosuppressive conditions, multiple and complex comorbidities, and increase in the use of invasive procedures over many decades has contributed to an increase in the number of pyogenic infections of the spine.13,14 Cervical pyogenic spondylodiscitis is a very rare disease accounting for less than 6% of all cases of pyogenic spondylitis of the spine.7 However, it is a serious condition with a mortality rate of 10%. Furthermore, 80% of cases are associated with epidural abscess formation, while 40% of cases involve neurological complications. Compared with other spine regions, the cervical spine permits a greater range of motion and the cervical cord occupies a larger portion of the spinal canal. These characteristics allow for pyogenic spondylodiscitis of the cervical spine to progress more rapidly and cause serious neurological complications.8,15 Considering the potential devastating complications and increased mortality, early diagnosis and prompt treatment should be the goal in cases of cervical pyogenic spondylodiscitis. Although the advent of antibiotic therapy enabled the nonsurgical management of early cases of cervical pyogenic spondylodiscitis, more advanced stages with spinal instability, cord compression, neurologic impairment, and absence of clinical improvement require surgical treatment.14,16–18 Surgical management should include meticulous debridement of all necrotic tissue; drainage of the epidural abscess; decompression of the spinal canal; alignment restoration; and spinal stabilization to prevent further deformity, pain, or neurological deficit.8 Cervical pyogenic spondylodiscitis predominantly involves the anterior structures of the spine, whereas the posterior elements are rarely affected.19 Therefore, many authors believe that anterior surgical approach to cervical pyogenic spondylodiscitis offers several advantages such as the eradication of necrotic tissue, direct relief of anterior compression, allowance for the collection of adequate tissue samples to ensure an accurate diagnosis, correction of kyphosis, and earlier fusion.
It is generally believed that instrumentations such as plates and screws may decrease antibiotic efficacy and increase bacterial adherence and biofilm formation.20,21 There has been a long-held belief that instrumentations should not be placed into an infected area, partly due to studies showing a 5% to 20% infection rate with implant insertion and existing beliefs that the implant can act as a locus of resistance for infection.22,23 Therefore, instrumentations have been blamed for disturbing antimicrobial penetration and infection eradication.24,25 An increase in septic loosening of the instrumentations was also reported.26,27 However, the use of instrumentations within the infected area of the thoracic or lumbar spine has been increasingly discussed. In addition, despite concerns regarding the presence of foreign material at the infection site, some authors have suggested the use of instrumentations for spinal reconstruction or stability.16–18,28,29 There is no consensus about which treatment method is superior.
Despite such kinds of debates, implants placed in active infections have been shown to be safe and efficacious in clinical studies.17–18,28 Past data on bacterial seeding were recorded in the context of stainless steel implants, which are associated with significantly greater infection rates than titanium implants.30,31 However, this concept has changed since implants moved largely to titanium. The decreased susceptibility of titanium to bacterial adhesion has been shown to confer greater resistance to infection than stainless steel.30,32,33 The development of antibiotics is also benefiting implant use. Therefore, the combination of radical debridement and titanium implants has advantages such as spinal stabilization and a shortened hospital stay. Our study adds to the body of evidence that includes other recent publications.3,34–36 All of these studies have shown that instrumentation can be performed at the time of surgical debridement with antibiotic therapy. Gorensek series reported no infection recurrence, and solid bony fusion was achieved in 15 of 17 patients (88%).34 Gonzalvo et al35 reported that all patients experienced complete infection resolution, pain reduction, and neurological function improvements. Wang et al36 reported no implant failure and no infection recurrence. Surgery can lead to significant improvements in pain. More recently, spinal surgeons have become more aggressive and courageous in the application of implants in infected regions. No implant-specific complications were reported by these studies.6,37 If strong stability is not ensured when treating the spondylodiscitis, then the issue has not been treated well and sagittal alignment is not maintained. In this case, even if autologous bone is used, anterior plating or posterior fixation is needed to prevent nonunion or sagittal malalignment. However, posterior fixation carries the burden of requiring another anterior operation.
ACDF with plating significantly contributed to better correction of segmental kyphosis and the maintenance of sagittal alignment. Despite the insertion of an implant into the infected area, fusion rate after ACDF with plating compared with after ACDF without plating was higher in our study. The advantages of ACDF with plating including the maintenance of spinal alignment, higher fusion rate, shortened hospital stay, and no need for external fixation are significant, and this method can be used safely and successfully. The maintenance of spinal stability and alignment is very important when treating patients with cervical pyogenic spondylodiscitis. In addition, we used autograft (tricortical iliac or cancellous) in interbody space in all cases. It is much less common today to use iliac autograft compared with allograft or peek in non-infected cases. However, it is important to use autograft instead of allograft or bone substitute in the infected case and there is no evidence for the use of allografts or bone substitutes.
The primary weakness of this study was its retrospective multicenter design. As with all retrospective chart reviews, we were limited to studying the documented effects and were reliant on the documentation's accuracy. Our second limitation is the relatively small number of patients. However, cervical pyogenic spondylodiscitis is rarer than cases with involvement of the lumbar and thoracic spines.
In conclusion, the current study showed satisfactory correction and maintenance of radiological parameters and a higher rate of fusion without recurrence in cases of ACDF with plating for cervical pyogenic spondylodiscitis compared with ACDF without plating. Our results suggest that ACDF with plating can be a safe and effective treatment option for patients with cervical pyogenic spondylodiscitis and that strong biomechanical stability is an important point in the successful treatment of cervical pyogenic spondylodiscitis. Therefore, we recommend the use of anterior cervical plating, which can provide strong biomechanical stability, for ACDF of cervical pyogenic spondylodiscitis.
- The maintenance of spinal stability and alignment is very important when treating patients with cervical pyogenic spondylodiscitis.
- Anterior cervical plating with the advantages including the maintenance of spinal alignment and higher fusion rate can be a safe and effective treatment option for patients with cervical pyogenic spondylodiscitis.
- We recommend the use of anterior plating for anterior cervical debridement and fusion of cervical pyogenic spondylodiscitis.
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