Eur Spine J DOI 10.1007/s00586-015-3941-y
ORIGINAL ARTICLE
Which method is the most effective for preventing postoperative infection in spinal surgery? Erol Oksuz1,5 • Fatih Ersay Deniz1 • Ozgur Gunal2 • Ozgur Demir1 Sener Barut2 • Fatma Markoc3 • Unal Erkorkmaz4
•
Received: 12 February 2014 / Revised: 7 April 2015 / Accepted: 7 April 2015 Ó Springer-Verlag Berlin Heidelberg 2015
Abstract Background Several methods have been used to reduce the infection rate in spinal surgeries with instrumentation. Purpose Which method is the most effective for preventing postoperative infection? Study design Basic science, animal model. Objective In the present study, the efficiency of antibiotic prophylaxis, silver-plated screws, and local rifamycin application to the surgical site was investigated in an experimental animal model. Staphylococcus aureus was used as the pathogen. Methods Fifty 6-month-old female Wistar albino rats were used. The animals were randomly numbered and divided into five groups of ten rats each (Group 1, control group; Group 2, titanium screw and S. aureus inoculation; Group 3, titanium screw, 0.1 ml rifamycin application to the surgical area, and bacterial inoculation; Group 4, titanium screw, single preoperative dose of IM cefazolin, and bacterial inoculation; Group 5, silver-plated screw and bacterial inoculation). Titanium micro-screws were placed
& Erol Oksuz [email protected] 1
Department of Neurosurgery, Gaziosmanpasa University, Tokat, Turkey
2
Department of Infectious Diseases and Clinical Microbiology, Gaziosmanpasa University, Tokat, Turkey
3
Department of Pathology, Gaziosmanpasa University, Tokat, Turkey
4
Department of Statistics, Sakarya University, Sakarya, Turkey
5
Kas¸ ıkcıbagları m. Ahmet Yesevi c., 8. Sok. No: 3, 60000 Merkez, Tokat, Turkey
into the pedicles. The control group received a sterile isotonic solution, and the other four groups received bacterial suspensions containing S. aureus. The animals were killed 15 days later. Results Intensive S. aureus growth was observed in all tissue and screw samples from Group 2. The results for Group 3 were similar to those for Group 1, no growth was observed in the screw cultures. Intensive growth was observed in the five screw samples in Group 4 and in the eight samples in Group 5. Conclusion Our study suggests that rifamycin application to the surgical area in spinal operations with instrumentation is an effective method to prevent S. aureus infections. Keywords Infection Spinal surgery Instrumentation Staphylococcus aureus Rifamycin
Introduction While the infection rate for simple discectomy has been reported to be below 1 %, the rate of infection in spinal surgery using instrumentation has been reported as 3–8.5 % [1–5]. This condition increases disease duration, prolongs hospitalization, increases treatment costs, and decreases patient quality of life [2]. Obesity, diabetes, longterm steroid use, rheumatoid arthritis, and advanced age, which are known as risk factors for infections, are also risk factors for spondylosis, so instrumentation may be necessary to treat some of these diseases [1, 2, 5]. Moreover, nutrition deficiency, smoking, long preoperative hospital stay, previous trauma operations, tumor excision, blood loss during the operation, extended operation time, and presence of postoperative incontinence are other risk factors for infections [1, 2].
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Eur Spine J
The most commonly encountered microorganism in patient series is the gram positive bacteria, Staphylococcus aureus, which can cause suppurative inflammation in the bone, leading to necrosis and dissolution of the bony matrix [2–4, 6]. This bacterium can also form a film layer on biomaterials, and due to this characteristic, may lead to antibiotic-resistant infections. Other frequently encountered bacteria are Streptococcus epidermidis, Enterococcus faecalis, Enterobacter cloacae, Pseudomonas aeruginosa, Klebsiella pneumonia, and Escherichia coli [2–4]. Silver-plated catheters have been used for a long time in body spaces filled with fluid because of its antibacterial characteristics. Although silver-plated polyaxial screws have recently been used in spinal surgery, there are few experimental and clinical studies. Local rifamycin application has been used in some clinics because of its antibacterial characteristics. However, experimental studies for local rifamycin are also limited. The most commonly used method for prophylaxis is systemic antibiotics, which are known to decrease infection rates significantly, especially in cases with instrumentation. However, there are different protocols for their use, which are still being debated [7–9]. This study aimed to compare the effectiveness of singledose systemic antibiotic prophylaxis, local rifamycin application, and silver-plated screw methods in decreasing the infection rate in an experimental animal model.
serum, the suspension was diluted serially with isotonic serum to obtain the final bacterial concentration of 106 CFU/10 ll. This suspension was divided into tubes in small volumes and stored at -70 °C to be used during the surgery. Inoculation into Tryptic Soy agar was performed to determine whether bacteria were alive before freezing and later during the surgical procedure after the stock solution was thawed. 10 ll bacteria from the stock solution were injected into the operational space except for the control group. The rats were anesthetized preoperatively with intraperitoneal ketamine hydrochloride (Ketalar, Pfizer, USA) and xylazine hydrochloride (xylazinbio %2, Bioveta, Czech Republic). For the surgical procedure, the lumbar region, which would be incised in the prone position, was shaved and rubbed with povidone iodine, and then an incision of 1.5 cm was performed. Then, paravertebral muscle dissection and decortication in the lumbar region were performed under the microscope. The pedicle was decorticated with a drill, and a space was opened for the screw. A screw 1 mm in diameter and 3 mm in length (Trimed, Turkey) was inserted (Figs. 1, 2). Then, 0.1 ml of serum physiologic solution was given to the control group, whereas S. aureus solution was given to the other groups. In the rifamycin group, first rifamycin was applied and following a 1-min interval the environment was dried. S. aureus solution was applied after drying the environment. Then, the fascia and skin were sutured. In Group
Materials and methods This study was performed with the approval of the Experimental Animals Ethics Committee at the local Experimental and Clinical Research Center and supported by The Scientific Research Commission of our University. In the present study, fifty 6-month-old Wistar albino female rats, weighing 200–250 g, were used. The rats were chosen randomly and divided into five groups. In Group 1, only a titanium screw was inserted (the control group), and sterile isotonic serum physiologic solution was applied. In Group 2, a titanium screw was inserted, and 106 CFU/10 ll S. aureus solution was applied. In Group 3, a titanium screw was inserted, and then 0.1 ml rifamycin and 106 CFU/10 ll S. aureus solutions were applied. In Group 4, after a single dose of intramuscular (IM) cefazolin, a titanium screw was inserted, and 106 CFU/10 ll S. aureus solution was applied. In Group 5, a silver-plated screw was inserted, and 106 CFU/10 ll S. aureus solution was applied. Standard species of methicillin susceptible S. aureus (ATCC 29213) were used as the pathogen, which was obtained from the Infectious Diseases and Clinical Microbiology laboratory. After a bacterial suspension was prepared using the McFarland 6 standard in sterile isotonic
123
Fig. 1 A–P radiography of a rat in which a pedicle screw was inserted
Eur Spine J
Fig. 2 Lateral radiography of a rat in which a pedicle screw was inserted
4, 30 mg/kg cephazoline Na was given IM before screw insertion. In Group 5, silver-plated screws were inserted. Two weeks later, the rats were anesthetized using the same method. First, sterile blood samples were drawn from the atrium. Then, placing the rats in prone position, microbiological and biopsy samples were obtained from the vertebra and surrounding muscle tissue, and also, the screws were removed. The rats were killed with high-dose potassium (10 mg). The samples were evaluated for microbiological and histological findings. After the screws were removed, a sample from the bone at entrance site of the screw was obtained, and all samples were placed in 15-ml sterile falcon tubes. The bone samples were ground in a sterile mortar, whereas muscle samples were homogenized in packages containing 10 ml of isotonic serum. After homogenization, serial dilutions were performed, and the samples were inoculated into Tryptic Soy agar. They were incubated at 37 °C for 24 h. Then, bacterial growth was evaluated qualitatively. Regarding growth, 1–3 colonies was accepted as scarce growth, and more than three colonies was accepted as intense growth. After the micro-screws were placed and mixed with 0.5 ml Tryptic Soy broth, they were inoculated into Tryptic Soy agar. The biopsy samples were fixed in 10 % formaldehyde solution, processed by routine histological methods, and embedded in paraffin. The sections were cut and stained with hematoxylin and eosin. Histologic changes, including
inflammation, necrosis, granulomas, and giant cells, were evaluated under a light microscope. Inflammation was scored as 0 = no inflammatory cells; 1 = minimal, few scattered inflammatory cells; 2 = moderate, including discrete aggregates of inflammation; and 3 = marked, diffuse inflammatory cell infiltrate. Necrosis was scored as 0 = no necrosis; 1 = minimal, less than 10 %; 2 = moderate, 10–50 %; and 3 = marked, greater than 50 % of the sections. Granulomas were scored as 0 = no granuloma; 1 = mild, only a few granulomas seen in all of the sections; 2 = moderate, several granulomas in some areas of the section; and 3 = marked, many granulomas were seen in every microscopic area of the section. Giant cells were scored as 0 = no giant cells; 1 = mild, few scattered giant cells; 2 = moderate, more abundant giant cells; and 3 = marked, many giant cells were seen in every microscopic area of the section. A Chi-squared test was used to compare the categorical variables (culture and pathological results) between the groups. Categorical variables are shown as counts (n) and percentages (%); p values of \0.05 were considered to be statistically significant. Analyses were performed by statistical software (IBM SPSS Statistics 20, SPSS Inc., An IBM Corp., Armonk, NY, USA). The results were evaluated with colleagues in the Department of Biostatistics.
Results Gross neurological deficits were not observed in the rats; cerebrospinal fluid (CSF) leakage was observed during the procedure in one rat, but after the procedure, neither neurologic deficit nor CSF fistula was observed in that rat. No systemic infection symptom, such as weight loss or fever, was observed in any of the rats. Growth in blood cultures was observed in two rats, one in the silver-plated screw group and one in the cefazolin group; nevertheless, the differences are not statistically significant. This finding might have been due to the development of cyclical bacteremia caused by local infection. Intensive growth was detected in all of the screw and tissue cultures from Group 2. The most similar group to this group was the silver-plated screw group in Group 5; growth was detected in eight rats (80 %) in the screw cultures and nine rats (90 %) in the tissue cultures. In Group 4, intense growth was detected in five screw cultures (62.5 %, n = 8), whereas sparse growth was detected in one rat (12.5 %). In the tissue cultures for this group, sparse growth was observed in two rats (25 %), and intense growth was observed in six rats (75 %). In Group 3, heavy growth was observed only in one tissue culture, and in the others, no growth was observed, including the screw
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Eur Spine J Table 1 The microbiological results and statistics of the groups Group 1 (n = 8)
Group 2 (n = 10)
Group 3 (n = 10)
Group 4 (n = 8)
Group 5 (n = 10)
p
0.506
Blood No growth
8 (100.0)
10 (100.0)
10 (100.0)
7 (87.5)
9 (90.0)
3? colonies (heavy)
0
0
0
1 (12.5)
1 (10.0)
Screw No growth
8 (100.0)
0
10 (100.0)
2 (25.0)
2 (20.0)
1–3 colonies (poor)
0
0
0
1 (12.5)
0
3? colonies (heavy)
0
10 (100.0)
0
5 (62.5)
8 (80.0)
7 (87.5)
0
9 (90.0)
0
1 (10.0)
\0.001
Tissue No growth 1–3 colonies (poor)
1 (12.5)
0
0
2 (25.0)
0
3? colonies (heavy)
0
10 (100.0)
1 (10.0)
6 (75.0)
9 (90.0)
cultures. In the control group (Group 1), sparse growth was observed only in one tissue culture, and in the others, no growth was observed, including the screw cultures. Comparisons of the microbiological results among the groups are shown in Table 1. Regarding the screw cultures, there were statistically significant differences among the groups (p \ 0.001). According to pairwise comparisons, there were statistically significant differences between the control and infected groups (p \ 0.001), control and silver-plated screw groups (p \ 0.001), infected and rifamycin groups (p \ 0.001), rifamycin and cefazolin groups (p \ 0.004), control and cefazolin groups (p \ 0.008), and the rifamycin and silverplated screw groups (p \ 0.001). No significant differences were detected for the other paired comparisons (p [ 0.05). Regarding the tissue cultures, there were statistically significant differences among the groups (p \ 0.001). According to pairwise comparisons, there were statistically significant differences between the control and infected groups (p \ 0.001), control and cefazolin groups (p \ 0.001), control and silver-plated screw groups (p \ 0.001), infected and rifamycin groups (p \ 0.001), rifamycin and cefazolin groups (p \ 0.001), and the rifamycin and silver-plated screw groups (p \ 0.001). No significant differences were detected for the other paired comparisons (p [ 0.05). Comparisons of the pathological results among the groups are shown in Table 2. Dense inflammation was observed in three specimens from Group 2 (30 %), four specimens from Group 4 (50 %) and one specimen from Group 5 (10 %). However, dense inflammation was not observed in the control Group and Group 3. Focal necrosis was observed in three specimens from Group 2 (30 %), two specimens from Group 3 (20 %), and two specimens from Group 4 (25 %). Yet, dense inflammation was not observed in the control group and Group 5. Dense granuloma formation and giant cells
123
\0.001
were observed in one specimen from Group 3 (10 %) and one specimen from Group 4 (12.5 %). In the pathological examination, regarding necrosis, there were statistically significant differences among the groups (p = 0.035). According to pairwise comparisons, there was a statistically significant difference between the control and infected groups (p \ 0.04) and the cefazolin and infected groups (p \ 0.04), but there were no significant differences for the other paired comparisons (p [ 0.05). There were no statistically significant differences between groups for the other parameters (p [ 0.05).
Discussion and conclusion The infection rate has been reported as 3–8.5 % in spinal surgery operations using instrumentation because the instrument provides a suitable environment for bacterial colonization, and pathogen bacteria can adhere to these areas and colonize. This condition prolongs disease duration, causes lengthened hospital stay, and increases treatment expenses while decreasing patient life quality. In the present study, the efficacy of antibiotic prophylaxis was compared to efficacies of silver-plated screws and local rifamycin for preventing infection, using a rat infection model that was defined by Ofluoglu et al. [10]. Barker reported in his meta-analysis study that prophylactic antibiotic usage was beneficial [7]. Watters et al. [11] reported in their review that antibiotic usage was level of C according to evidence-based medicine. In the same study, the authors also reported that there was no consensus about antibiotic type or dose in the literature and that widespectrum antibiotic use for instrument-based surgeries had an evidence level of C [11]. Walters et al. [12] indicated in their study on sheep discs that cefazolin was effective against the development of discitis. In our study, intense
Eur Spine J Table 2 The pathological results and statistics for the groups Group 1 (n = 8)
Group 2 (n = 10)
Group 3 (n = 10)
Group 4 (n = 8)
Group 5 (n = 10)
p
0.119
Inflammation Absent
1 (12.5)
0
1 (10.0)
0
0
Rare
4 (50.0)
2 (20.0)
6 (60.0)
1 (12.5.0)
3 (30.0)
Focal
3 (37.5)
5 (50.0)
3 (30.0)
3 (37.5.0)
6 (60.0)
Dense
0
3 (30.0)
0
4 (50.0)
1 (10.0)
Necrosis Absent
7 (87.5)
1 (10.0)
5 (50.0)
5 (62.5)
4 (4.0)
Rare
1 (12.5)
6 (60.0)
3 (30.0)
1 (12.5)
6 (60.0)
Focal
0
3 (30.0)
2 (20.0)
2 (25.0)
0
Absent Rare
6 (75.0) 0
6 (60.0) 1 (10.0)
6 (60.0) 0
3 (37.5) 2 (25.0)
6 (60.0) 0
Focal
2 (25.0)
3 (30.0)
3 (30.0)
2 (25.0)
4 (40.0)
Dense
0
0
1 (10.0)
1 (12.5)
0
0.035
Granuloma 0.545
Giant cell Absent
6 (75.0)
6 (60.0)
6 (60.0)
3 (37.5)
6 (60.0)
Rare
0
1 (10.0)
0
2 (25.0)
0
Focal
2 (25.0)
3 (30.0)
3 (30.0)
2 (25.0)
4 (40.0)
Dense
0
0
1 (10.0)
1 (12.5)
0
growth was observed in 75 % of the screws and 62.5 % of the tissue cultures from rats treated with a single-dose antibiotic prophylaxis. However, there was not a statistically significant difference between the antibiotic prophylaxis and infected groups. The reason for these results may be the small number of subjects in the groups. Compared to the local rifamycin group, the efficacy was found to be lower, and this difference was statistically significant. In present study, only the effect of single-dose cefazolin was evaluated. Because of there is no standard consensus about systemic antibiotic prophylaxis in literature in spinal surgery only single-dose cefazolin was used. In this context, various antibiotics have been used for prophylaxis in spinal surgery [7, 11]. In the future, a study can be planned to compare of multi-dose cefazolin and other antibiotics in experimental models. In addition, it is understood that different doses of cefazolin has been used in prophylaxis in various studies. Rifamycins were first isolated in 1957 from Streptomyces mediterranei. Rifamycin SV, which became the first member of this class to enter clinical use as an intravenous antibiotic. The rifamycins have a unique mechanism of action, selectively inhibiting bacterial DNA-dependent RNA polymerase, and show no cross-resistance with other antibiotics in clinical use [13]. Rifamycin is an agent that especially effect on gram positive microorganisms and Mycobacterium tuberculosis. The effect of rifamycin on gram negative microorganisms is quite less compared to gram positive microorganisms [13].
0.545
Senneville et al. [14] reported in their study, investigating S. aureus infection in knee and femur prostheses, that rifamycin combined treatments were more effective. In the same study, long-term systemic use of rifamycin was reported to be toxic to the liver. Muttaiyah et al. [15] reported that using clindamycin and rifamycin-soaked external ventricular drainage catheters decreased catheter-dependent ventriculitis. In the present study, a similarity was observed between the local rifamycin use and control groups. No growth was observed in the screw-inoculated cultures in the two groups. Among the tissue samples, 1–3 colonies were observed in the culture in one rat from control group, whereas intense cultural growth was observed in one rat from the group using local rifamycin. This condition was thought to be the result of rifamycin presence at high doses in the surgical area without systemic side effects. Secinti et al. [16] compared polarized silver-plated screws with normal screws in rabbits in terms of infection and reported that there was a statistically significant difference between them. In our study, there was a small difference between the titanium screw and silver-plated screw groups, but this difference was not statistically significant. In addition, in the pathological examination, there was also not a statistically significant difference. Finally, as a well-known and cheap agent rifamycin should be considered as a local agent in the prophylaxis of spinal surgery. The present study demonstrated that local rifamycin usage was more effective than the other compared methods for preventing of infection.
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Eur Spine J Conflict of interest
None.
References 1. Fang A, Hu SS, Endres N, Bradford DS (2005) Risk factors for infection after spinal surgery. Spine 30:1460–1465 2. Lim MR, Lee JY, Vaccaro AR (2006) Surgical infections in the traumatized spine. Clin Orthop Relat Res 444:114–119 3. Massie JB, Heller JG, Abitbol JJ, McPherson D, Garfin SR (1992) Postoperative posterior spinal wound infections. Clin Orthop Relat Res 284:99–108 4. Weinstein MA, McCabe JP, Cammisa FP Jr (2000) Postoperative spinal wound infection: a review of 2,391 consecutive index procedures. J Spinal Disord 13(5):422–426 5. Hodges SD, Humphreys SC, Egk JC, Covington LA, Kurzynske NG (1998) Low postoperative infection rates with instrumented lumbar fusion. South Med J 91:1132–1136 6. Silber JS, Anderson DG, Vaccaro AR, Anderson PA, McCormick P (2002) Management of postprocedural discitis. Spine J 2(4):279–287 7. Barker FG (2002) Efficacy of prophylactic antibiotic therapy in spinal surgery: a meta-analysis. Neurosurgery 51:391–401 8. Hellbusch LC, Helzer-Julin M, Doran SE et al (2008) Single-dose vs multiple-dose antibiotic prophylaxis in instrumented lumbar fusion—a prospective study. Surg Neurol 70(6):622–627 (discussion 627)
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9. Van Middendorp JJ, Pull ter Gunne AF, Schuetz M et al (2012) A methodological systematic review on surgical site infections following spinal surgery. Spine 37(24):2034–2045 10. Ofluoglu EA, Zileli M, Aydin D, Baris YS et al (2007) Implantrelated infection model in rat spine. Arch Orthop Trauma Surg 127:391–396 11. Watters WC, Baisden J, Bono CM et al (2009) Antibiotic prophylaxis in spine surgery: an evidence-based clinical guideline for the use of prophylactic antibiotics in spine surgery. Spine J 9:142–146 12. Walters R, Rahmat R, Shimamura Y, Fraser R, Moore R (2006) Prophylactic cephazolin to prevent discitis in an ovine model. Spine 31(4):391–396 13. Calfee DP (2010) Rifamycins. In: Mandell GL, Bennett JE, Dolin R (eds) Mandell, Douglas, and Bennett’s principles and practice of infectious diseases, 7th edn. Elsevier, Philadelphia, pp 403–418 14. Senneville E, Joulie D, Legout L et al (2011) Outcome and predictors of treatment failure in total hip/knee prosthetic joint infections due to Staphylococcus aureus. Clin Infect Dis 53:334–340 15. Muttaiyah S, Ritchie S, John S, Mee E, Roberts S (2010) Efficacy of antibiotic-impregnated external ventricular drain catheters. J Clin Neurosci 17:296–298 16. Secinti KD, Ayten M, Kahilogullari G, Kaygusuz G, Ugur HC, Attar A (2008) Antibacterial effects of electrically activated vertebral implants. J Clin Neurosc 15:434–439
ORIGINAL ARTICLE
Which method is the most effective for preventing postoperative infection in spinal surgery? Erol Oksuz1,5 • Fatih Ersay Deniz1 • Ozgur Gunal2 • Ozgur Demir1 Sener Barut2 • Fatma Markoc3 • Unal Erkorkmaz4
•
Received: 12 February 2014 / Revised: 7 April 2015 / Accepted: 7 April 2015 Ó Springer-Verlag Berlin Heidelberg 2015
Abstract Background Several methods have been used to reduce the infection rate in spinal surgeries with instrumentation. Purpose Which method is the most effective for preventing postoperative infection? Study design Basic science, animal model. Objective In the present study, the efficiency of antibiotic prophylaxis, silver-plated screws, and local rifamycin application to the surgical site was investigated in an experimental animal model. Staphylococcus aureus was used as the pathogen. Methods Fifty 6-month-old female Wistar albino rats were used. The animals were randomly numbered and divided into five groups of ten rats each (Group 1, control group; Group 2, titanium screw and S. aureus inoculation; Group 3, titanium screw, 0.1 ml rifamycin application to the surgical area, and bacterial inoculation; Group 4, titanium screw, single preoperative dose of IM cefazolin, and bacterial inoculation; Group 5, silver-plated screw and bacterial inoculation). Titanium micro-screws were placed
& Erol Oksuz [email protected] 1
Department of Neurosurgery, Gaziosmanpasa University, Tokat, Turkey
2
Department of Infectious Diseases and Clinical Microbiology, Gaziosmanpasa University, Tokat, Turkey
3
Department of Pathology, Gaziosmanpasa University, Tokat, Turkey
4
Department of Statistics, Sakarya University, Sakarya, Turkey
5
Kas¸ ıkcıbagları m. Ahmet Yesevi c., 8. Sok. No: 3, 60000 Merkez, Tokat, Turkey
into the pedicles. The control group received a sterile isotonic solution, and the other four groups received bacterial suspensions containing S. aureus. The animals were killed 15 days later. Results Intensive S. aureus growth was observed in all tissue and screw samples from Group 2. The results for Group 3 were similar to those for Group 1, no growth was observed in the screw cultures. Intensive growth was observed in the five screw samples in Group 4 and in the eight samples in Group 5. Conclusion Our study suggests that rifamycin application to the surgical area in spinal operations with instrumentation is an effective method to prevent S. aureus infections. Keywords Infection Spinal surgery Instrumentation Staphylococcus aureus Rifamycin
Introduction While the infection rate for simple discectomy has been reported to be below 1 %, the rate of infection in spinal surgery using instrumentation has been reported as 3–8.5 % [1–5]. This condition increases disease duration, prolongs hospitalization, increases treatment costs, and decreases patient quality of life [2]. Obesity, diabetes, longterm steroid use, rheumatoid arthritis, and advanced age, which are known as risk factors for infections, are also risk factors for spondylosis, so instrumentation may be necessary to treat some of these diseases [1, 2, 5]. Moreover, nutrition deficiency, smoking, long preoperative hospital stay, previous trauma operations, tumor excision, blood loss during the operation, extended operation time, and presence of postoperative incontinence are other risk factors for infections [1, 2].
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Eur Spine J
The most commonly encountered microorganism in patient series is the gram positive bacteria, Staphylococcus aureus, which can cause suppurative inflammation in the bone, leading to necrosis and dissolution of the bony matrix [2–4, 6]. This bacterium can also form a film layer on biomaterials, and due to this characteristic, may lead to antibiotic-resistant infections. Other frequently encountered bacteria are Streptococcus epidermidis, Enterococcus faecalis, Enterobacter cloacae, Pseudomonas aeruginosa, Klebsiella pneumonia, and Escherichia coli [2–4]. Silver-plated catheters have been used for a long time in body spaces filled with fluid because of its antibacterial characteristics. Although silver-plated polyaxial screws have recently been used in spinal surgery, there are few experimental and clinical studies. Local rifamycin application has been used in some clinics because of its antibacterial characteristics. However, experimental studies for local rifamycin are also limited. The most commonly used method for prophylaxis is systemic antibiotics, which are known to decrease infection rates significantly, especially in cases with instrumentation. However, there are different protocols for their use, which are still being debated [7–9]. This study aimed to compare the effectiveness of singledose systemic antibiotic prophylaxis, local rifamycin application, and silver-plated screw methods in decreasing the infection rate in an experimental animal model.
serum, the suspension was diluted serially with isotonic serum to obtain the final bacterial concentration of 106 CFU/10 ll. This suspension was divided into tubes in small volumes and stored at -70 °C to be used during the surgery. Inoculation into Tryptic Soy agar was performed to determine whether bacteria were alive before freezing and later during the surgical procedure after the stock solution was thawed. 10 ll bacteria from the stock solution were injected into the operational space except for the control group. The rats were anesthetized preoperatively with intraperitoneal ketamine hydrochloride (Ketalar, Pfizer, USA) and xylazine hydrochloride (xylazinbio %2, Bioveta, Czech Republic). For the surgical procedure, the lumbar region, which would be incised in the prone position, was shaved and rubbed with povidone iodine, and then an incision of 1.5 cm was performed. Then, paravertebral muscle dissection and decortication in the lumbar region were performed under the microscope. The pedicle was decorticated with a drill, and a space was opened for the screw. A screw 1 mm in diameter and 3 mm in length (Trimed, Turkey) was inserted (Figs. 1, 2). Then, 0.1 ml of serum physiologic solution was given to the control group, whereas S. aureus solution was given to the other groups. In the rifamycin group, first rifamycin was applied and following a 1-min interval the environment was dried. S. aureus solution was applied after drying the environment. Then, the fascia and skin were sutured. In Group
Materials and methods This study was performed with the approval of the Experimental Animals Ethics Committee at the local Experimental and Clinical Research Center and supported by The Scientific Research Commission of our University. In the present study, fifty 6-month-old Wistar albino female rats, weighing 200–250 g, were used. The rats were chosen randomly and divided into five groups. In Group 1, only a titanium screw was inserted (the control group), and sterile isotonic serum physiologic solution was applied. In Group 2, a titanium screw was inserted, and 106 CFU/10 ll S. aureus solution was applied. In Group 3, a titanium screw was inserted, and then 0.1 ml rifamycin and 106 CFU/10 ll S. aureus solutions were applied. In Group 4, after a single dose of intramuscular (IM) cefazolin, a titanium screw was inserted, and 106 CFU/10 ll S. aureus solution was applied. In Group 5, a silver-plated screw was inserted, and 106 CFU/10 ll S. aureus solution was applied. Standard species of methicillin susceptible S. aureus (ATCC 29213) were used as the pathogen, which was obtained from the Infectious Diseases and Clinical Microbiology laboratory. After a bacterial suspension was prepared using the McFarland 6 standard in sterile isotonic
123
Fig. 1 A–P radiography of a rat in which a pedicle screw was inserted
Eur Spine J
Fig. 2 Lateral radiography of a rat in which a pedicle screw was inserted
4, 30 mg/kg cephazoline Na was given IM before screw insertion. In Group 5, silver-plated screws were inserted. Two weeks later, the rats were anesthetized using the same method. First, sterile blood samples were drawn from the atrium. Then, placing the rats in prone position, microbiological and biopsy samples were obtained from the vertebra and surrounding muscle tissue, and also, the screws were removed. The rats were killed with high-dose potassium (10 mg). The samples were evaluated for microbiological and histological findings. After the screws were removed, a sample from the bone at entrance site of the screw was obtained, and all samples were placed in 15-ml sterile falcon tubes. The bone samples were ground in a sterile mortar, whereas muscle samples were homogenized in packages containing 10 ml of isotonic serum. After homogenization, serial dilutions were performed, and the samples were inoculated into Tryptic Soy agar. They were incubated at 37 °C for 24 h. Then, bacterial growth was evaluated qualitatively. Regarding growth, 1–3 colonies was accepted as scarce growth, and more than three colonies was accepted as intense growth. After the micro-screws were placed and mixed with 0.5 ml Tryptic Soy broth, they were inoculated into Tryptic Soy agar. The biopsy samples were fixed in 10 % formaldehyde solution, processed by routine histological methods, and embedded in paraffin. The sections were cut and stained with hematoxylin and eosin. Histologic changes, including
inflammation, necrosis, granulomas, and giant cells, were evaluated under a light microscope. Inflammation was scored as 0 = no inflammatory cells; 1 = minimal, few scattered inflammatory cells; 2 = moderate, including discrete aggregates of inflammation; and 3 = marked, diffuse inflammatory cell infiltrate. Necrosis was scored as 0 = no necrosis; 1 = minimal, less than 10 %; 2 = moderate, 10–50 %; and 3 = marked, greater than 50 % of the sections. Granulomas were scored as 0 = no granuloma; 1 = mild, only a few granulomas seen in all of the sections; 2 = moderate, several granulomas in some areas of the section; and 3 = marked, many granulomas were seen in every microscopic area of the section. Giant cells were scored as 0 = no giant cells; 1 = mild, few scattered giant cells; 2 = moderate, more abundant giant cells; and 3 = marked, many giant cells were seen in every microscopic area of the section. A Chi-squared test was used to compare the categorical variables (culture and pathological results) between the groups. Categorical variables are shown as counts (n) and percentages (%); p values of \0.05 were considered to be statistically significant. Analyses were performed by statistical software (IBM SPSS Statistics 20, SPSS Inc., An IBM Corp., Armonk, NY, USA). The results were evaluated with colleagues in the Department of Biostatistics.
Results Gross neurological deficits were not observed in the rats; cerebrospinal fluid (CSF) leakage was observed during the procedure in one rat, but after the procedure, neither neurologic deficit nor CSF fistula was observed in that rat. No systemic infection symptom, such as weight loss or fever, was observed in any of the rats. Growth in blood cultures was observed in two rats, one in the silver-plated screw group and one in the cefazolin group; nevertheless, the differences are not statistically significant. This finding might have been due to the development of cyclical bacteremia caused by local infection. Intensive growth was detected in all of the screw and tissue cultures from Group 2. The most similar group to this group was the silver-plated screw group in Group 5; growth was detected in eight rats (80 %) in the screw cultures and nine rats (90 %) in the tissue cultures. In Group 4, intense growth was detected in five screw cultures (62.5 %, n = 8), whereas sparse growth was detected in one rat (12.5 %). In the tissue cultures for this group, sparse growth was observed in two rats (25 %), and intense growth was observed in six rats (75 %). In Group 3, heavy growth was observed only in one tissue culture, and in the others, no growth was observed, including the screw
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Eur Spine J Table 1 The microbiological results and statistics of the groups Group 1 (n = 8)
Group 2 (n = 10)
Group 3 (n = 10)
Group 4 (n = 8)
Group 5 (n = 10)
p
0.506
Blood No growth
8 (100.0)
10 (100.0)
10 (100.0)
7 (87.5)
9 (90.0)
3? colonies (heavy)
0
0
0
1 (12.5)
1 (10.0)
Screw No growth
8 (100.0)
0
10 (100.0)
2 (25.0)
2 (20.0)
1–3 colonies (poor)
0
0
0
1 (12.5)
0
3? colonies (heavy)
0
10 (100.0)
0
5 (62.5)
8 (80.0)
7 (87.5)
0
9 (90.0)
0
1 (10.0)
\0.001
Tissue No growth 1–3 colonies (poor)
1 (12.5)
0
0
2 (25.0)
0
3? colonies (heavy)
0
10 (100.0)
1 (10.0)
6 (75.0)
9 (90.0)
cultures. In the control group (Group 1), sparse growth was observed only in one tissue culture, and in the others, no growth was observed, including the screw cultures. Comparisons of the microbiological results among the groups are shown in Table 1. Regarding the screw cultures, there were statistically significant differences among the groups (p \ 0.001). According to pairwise comparisons, there were statistically significant differences between the control and infected groups (p \ 0.001), control and silver-plated screw groups (p \ 0.001), infected and rifamycin groups (p \ 0.001), rifamycin and cefazolin groups (p \ 0.004), control and cefazolin groups (p \ 0.008), and the rifamycin and silverplated screw groups (p \ 0.001). No significant differences were detected for the other paired comparisons (p [ 0.05). Regarding the tissue cultures, there were statistically significant differences among the groups (p \ 0.001). According to pairwise comparisons, there were statistically significant differences between the control and infected groups (p \ 0.001), control and cefazolin groups (p \ 0.001), control and silver-plated screw groups (p \ 0.001), infected and rifamycin groups (p \ 0.001), rifamycin and cefazolin groups (p \ 0.001), and the rifamycin and silver-plated screw groups (p \ 0.001). No significant differences were detected for the other paired comparisons (p [ 0.05). Comparisons of the pathological results among the groups are shown in Table 2. Dense inflammation was observed in three specimens from Group 2 (30 %), four specimens from Group 4 (50 %) and one specimen from Group 5 (10 %). However, dense inflammation was not observed in the control Group and Group 3. Focal necrosis was observed in three specimens from Group 2 (30 %), two specimens from Group 3 (20 %), and two specimens from Group 4 (25 %). Yet, dense inflammation was not observed in the control group and Group 5. Dense granuloma formation and giant cells
123
\0.001
were observed in one specimen from Group 3 (10 %) and one specimen from Group 4 (12.5 %). In the pathological examination, regarding necrosis, there were statistically significant differences among the groups (p = 0.035). According to pairwise comparisons, there was a statistically significant difference between the control and infected groups (p \ 0.04) and the cefazolin and infected groups (p \ 0.04), but there were no significant differences for the other paired comparisons (p [ 0.05). There were no statistically significant differences between groups for the other parameters (p [ 0.05).
Discussion and conclusion The infection rate has been reported as 3–8.5 % in spinal surgery operations using instrumentation because the instrument provides a suitable environment for bacterial colonization, and pathogen bacteria can adhere to these areas and colonize. This condition prolongs disease duration, causes lengthened hospital stay, and increases treatment expenses while decreasing patient life quality. In the present study, the efficacy of antibiotic prophylaxis was compared to efficacies of silver-plated screws and local rifamycin for preventing infection, using a rat infection model that was defined by Ofluoglu et al. [10]. Barker reported in his meta-analysis study that prophylactic antibiotic usage was beneficial [7]. Watters et al. [11] reported in their review that antibiotic usage was level of C according to evidence-based medicine. In the same study, the authors also reported that there was no consensus about antibiotic type or dose in the literature and that widespectrum antibiotic use for instrument-based surgeries had an evidence level of C [11]. Walters et al. [12] indicated in their study on sheep discs that cefazolin was effective against the development of discitis. In our study, intense
Eur Spine J Table 2 The pathological results and statistics for the groups Group 1 (n = 8)
Group 2 (n = 10)
Group 3 (n = 10)
Group 4 (n = 8)
Group 5 (n = 10)
p
0.119
Inflammation Absent
1 (12.5)
0
1 (10.0)
0
0
Rare
4 (50.0)
2 (20.0)
6 (60.0)
1 (12.5.0)
3 (30.0)
Focal
3 (37.5)
5 (50.0)
3 (30.0)
3 (37.5.0)
6 (60.0)
Dense
0
3 (30.0)
0
4 (50.0)
1 (10.0)
Necrosis Absent
7 (87.5)
1 (10.0)
5 (50.0)
5 (62.5)
4 (4.0)
Rare
1 (12.5)
6 (60.0)
3 (30.0)
1 (12.5)
6 (60.0)
Focal
0
3 (30.0)
2 (20.0)
2 (25.0)
0
Absent Rare
6 (75.0) 0
6 (60.0) 1 (10.0)
6 (60.0) 0
3 (37.5) 2 (25.0)
6 (60.0) 0
Focal
2 (25.0)
3 (30.0)
3 (30.0)
2 (25.0)
4 (40.0)
Dense
0
0
1 (10.0)
1 (12.5)
0
0.035
Granuloma 0.545
Giant cell Absent
6 (75.0)
6 (60.0)
6 (60.0)
3 (37.5)
6 (60.0)
Rare
0
1 (10.0)
0
2 (25.0)
0
Focal
2 (25.0)
3 (30.0)
3 (30.0)
2 (25.0)
4 (40.0)
Dense
0
0
1 (10.0)
1 (12.5)
0
growth was observed in 75 % of the screws and 62.5 % of the tissue cultures from rats treated with a single-dose antibiotic prophylaxis. However, there was not a statistically significant difference between the antibiotic prophylaxis and infected groups. The reason for these results may be the small number of subjects in the groups. Compared to the local rifamycin group, the efficacy was found to be lower, and this difference was statistically significant. In present study, only the effect of single-dose cefazolin was evaluated. Because of there is no standard consensus about systemic antibiotic prophylaxis in literature in spinal surgery only single-dose cefazolin was used. In this context, various antibiotics have been used for prophylaxis in spinal surgery [7, 11]. In the future, a study can be planned to compare of multi-dose cefazolin and other antibiotics in experimental models. In addition, it is understood that different doses of cefazolin has been used in prophylaxis in various studies. Rifamycins were first isolated in 1957 from Streptomyces mediterranei. Rifamycin SV, which became the first member of this class to enter clinical use as an intravenous antibiotic. The rifamycins have a unique mechanism of action, selectively inhibiting bacterial DNA-dependent RNA polymerase, and show no cross-resistance with other antibiotics in clinical use [13]. Rifamycin is an agent that especially effect on gram positive microorganisms and Mycobacterium tuberculosis. The effect of rifamycin on gram negative microorganisms is quite less compared to gram positive microorganisms [13].
0.545
Senneville et al. [14] reported in their study, investigating S. aureus infection in knee and femur prostheses, that rifamycin combined treatments were more effective. In the same study, long-term systemic use of rifamycin was reported to be toxic to the liver. Muttaiyah et al. [15] reported that using clindamycin and rifamycin-soaked external ventricular drainage catheters decreased catheter-dependent ventriculitis. In the present study, a similarity was observed between the local rifamycin use and control groups. No growth was observed in the screw-inoculated cultures in the two groups. Among the tissue samples, 1–3 colonies were observed in the culture in one rat from control group, whereas intense cultural growth was observed in one rat from the group using local rifamycin. This condition was thought to be the result of rifamycin presence at high doses in the surgical area without systemic side effects. Secinti et al. [16] compared polarized silver-plated screws with normal screws in rabbits in terms of infection and reported that there was a statistically significant difference between them. In our study, there was a small difference between the titanium screw and silver-plated screw groups, but this difference was not statistically significant. In addition, in the pathological examination, there was also not a statistically significant difference. Finally, as a well-known and cheap agent rifamycin should be considered as a local agent in the prophylaxis of spinal surgery. The present study demonstrated that local rifamycin usage was more effective than the other compared methods for preventing of infection.
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Eur Spine J Conflict of interest
None.
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