Efficiency of antibiotic-loaded polymethylmethacrylate rods for treatment of the implant-related infections in rat spine

STUDY DESIGN

A study of local treatment of the implant-related infections in animal spine.

OBJECTIVE

: This study aims to investigate the efficiency of antibiotic-loaded polymethylmethacrylate rods for treatment of the implant-related infections.

SUMMARY OF BACKGROUND DATA

Today's implant-related vertebral infections are challenging in spinal surgery. In addition to resolving this problem, systemic antibiotic treatment is necessary to study and develop the effectiveness of locally applied treatment methods.

METHODS

Twenty-four female white Sprague Dawley rats were randomized in 3 different groups, each consisting of 8 animals. Under general anesthesia, 3 mm titanium microscrew was implanted in the thoracic vertebra. All 3 groups were inoculated with the same concentration of Staphylococcus aureus (10 colony-forming units/10 μL). Group 1 was assigned as a control group and received no additional therapy, group 2 was given single intraperitoneal doses of vancomycin, and group 3 was implanted vancomycin buffered acrylic rods.

RESULTS

The results were analyzed by Fischer exact test. The comparison between the groups revealed a significantly higher therapeutic effect (P<0.05) in the local therapy group and in the systematic treatment group compared with the control group. The success of the treatment in the systemic treatment group was statistically not significantly different (P>0.05) compared with the outcome of the locally treated group.

CONCLUSIONS

This study shows the success of antibiotic-loaded polymethylmethacrylate rods for the treatment of the spinal implant infections. Further research involving clinical studies is required to increase the efficacy and the clinical applicability of the technique.

Role of biofilms in neurosurgical device-related infections

Bacterial biofilms have recently been shown to be important in neurosurgical device-related infections. Because the concept of biofilms is novel to most practitioners, it is important to understand that both traditional pharmaceutical therapies and host defense mechanisms that are aimed at treating or overcoming free-swimming bacteria are largely ineffective against the sessile bacteria in a biofilm. Bacterial biofilms are complex surface-attached structures that are composed of an extruded extracellular matrix in which the individual bacteria are embedded. Superimposed on this physical architecture is a complex system of intercellular signaling, termed quorum sensing. These complex organizational features endow biofilms with numerous microenvironments and a concomitant number of distinct bacterial phenotypes. Each of the bacterial phenotypes within the biofilm displays a unique gene expression pattern tied to nutrient availability and waste transport. Such diversity provides the biofilm as a whole with an enormous survival advantage when compared to the individual component bacterial cells. Thus, it is appropriate to view the biofilm as a multicellular organism, akin to metazoan eukaryotic life. Bacterial biofilms are much hardier than free floating or planktonic bacteria and are primarily responsible for device-related infections. Now that basic research has demonstrated that the vast majority of bacteria exist in biofilms, the paradigm of biofilm-associated chronic infections is spreading to the clinical world. Understanding how these biofilm infections affect patients with neurosurgical devices is a prerequisite to developing strategies for their treatment and prevention.

Management of postoperative infections after spinal instrumentation

The authors retrospectively reviewed 452 consecutively treated patients who underwent a spinal instrumentation procedure at a single institution to establish which patients and which surgical approaches might be associated with an increased risk of developing deep wound infections and to determine the efficacy with which the institution's current treatment strategy eradicates these infections. Wound infections occurred in 17 patients (10 men and seven women) with spinal instrumentation (incidence 3.8%). All infections occurred after posterior spinal instrumentation procedures (7.2%); there were no infections after anterior instrumentation procedures regardless of the level. Each patient was assigned an infection risk factor (RF) score depending on the number of RFs identified in an individual patient preoperatively. The mean RF score of patients who developed infections was 2.18, whereas the mean RF score for a procedure-matched, infection-free control group was 0.71. The mean number of days from surgery to clinical presentation was 27.6 days (range 4-120 days), and the mean increase in hospitalization time for the subset of patients who developed infections was 16.6 days. The most common organism isolated from wound cultures was Staphylococcus aureus (nine of 17 cases). Of the 17 patients, five had infections involving multiple organisms. All patients were infection free at a minimum of 8 months follow-up review. The current treatment regimen advocated at this institution consists of operative debridement of the infected wound, a course of intravenous followed by oral antibiotic medications, insertion of an antibiotic-containing irrigation-suction system for a mean of 5 days, and maintenance of the instrumentation system within the infected wound.

Management of postoperative infections after spinal instrumentation

The authors retrospectively reviewed 452 consecutively treated patients who underwent a spinal instrumentation procedure at a single institution to establish which patients and which surgical approaches might be associated with an increased risk of developing deep wound infections and to determine the efficacy with which the institution's current treatment strategy eradicates these infections. Wound infections occurred in 17 patients (10 men and seven women) with spinal instrumentation (incidence 3.8%). All infections occurred after posterior spinal instrumentation procedures (7.2%); there were no infections after anterior instrumentation procedures regardless of the level. Each patient was assigned an infection risk factor (RF) score depending on the number of RFs identified in an individual patient preoperatively. The mean RF score of patients who developed infections was 2.18, whereas the mean RF score for a procedure-matched, infection-free control group was 0.71. The mean number of days from surgery to clinical presentation was 27.6 days (range 4-120 days), and the mean increase in hospitalization time for the subset of patients who developed infections was 16.6 days. The most common organism isolated from wound cultures was Staphylococcus aureus (nine of 17 cases). Of the 17 patients, five had infections involving multiple organisms. All patients were infection free at a minimum of 8 months follow-up review. The current treatment regimen advocated at this institution consists of operative debridement of the infected wound, a course of intravenous followed by oral antibiotic medications, insertion of an antibiotic-containing irrigation-suction system for a mean of 5 days, and maintenance of the instrumentation system within the infected wound.