Tobramycin-impregnated calcium sulfate pellets for the treatment of chronic osteomyelitis in children and adolescents

Clinical Practice Guideline by the Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA): 2023 Guideline on Diagnosis and Management of Acute Bacterial Arthritis in Pediatrics

This clinical practice guideline for the diagnosis and treatment of acute bacterial arthritis (ABA) in children was developed by a multidisciplinary panel representing the Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA). This guideline is intended for use by healthcare professionals who care for children with ABA, including specialists in pediatric infectious diseases and orthopedics. The panel's recommendations for the diagnosis and treatment of ABA are based upon evidence derived from topic-specific systematic literature reviews. Summarized below are the recommendations for the diagnosis and treatment of ABA in children. The panel followed a systematic process used in the development of other IDSA and PIDS clinical practice guidelines, which included a standardized methodology for rating the certainty of the evidence and strength of recommendation using the GRADE approach (Grading of Recommendations Assessment, Development and Evaluation) (see Figure 1). A detailed description of background, methods, evidence summary and rationale that support each recommendation, and knowledge gaps can be found online in the full text.

Pediatric musculoskeletal infections

PURPOSE OF REVIEW

The aim of this article is to review the recent guidelines and literature regarding the diagnosis and the treatment of common pediatric musculoskeletal infections: septic arthritis, osteomyelitis, pyomyositis, and Lyme disease.

RECENT FINDINGS

In the last decade, a better understanding of the causative organisms of common bacterial infections, including Kingella , leads to prompt targeted antimicrobial coverage in all musculoskeletal infections. Prompt diagnosis and treatment continues to be the mainstay in the treatment of children with osteoarticular infections. Efforts to improve early detection have lead to improving rapid lab diagnostic testing; however, more advanced diagnostics such as arthrocentesis for septic arthritis and MRI for osteomyelitis and pyomyositis, remain the gold standard. Shorter and narrowed antibiotic courses, with appropriate transition to outpatient oral treatment provide effective infection clearance and reduction in complications of disease.

SUMMARY

Advances in diagnostics, including pathogen identification as well as imaging continues to improve our ability to diagnose and treat these infections, although still lack ability to provide definitive diagnosis without more invasive nor advanced techniques.

An assessment of physical properties and the viability of osteoblast-like cells of cefazolin-impregnated calcium sulfate bone-void filler

Calcium sulfate, an injectable and biodegradable bone-void filler, is widely used in orthopedic surgery. Based on clinical experience, bone-defect substitutes can also serve as vehicles for the delivery of drugs, for example, antibiotics, to prevent or to treat infections such as osteomyelitis. However, antibiotic additions change the characteristics of calcium sulfate cement. Moreover, high-dose antibiotics may also be toxic to bony tissues. Accordingly, cefazolin at varying weight ratios was added to calcium sulfate samples and characterized in vitro. The results revealed that cefazolin changed the hydration reaction and prolonged the initial setting times of calcium sulfate bone cement. For the crystalline structure identification, X-ray diffractometer revealed that cefazolin additive resulted in the decrease of peak intensity corresponding to calcium sulfate dihydrate which implying incomplete phase conversion of calcium sulfate hemihydrate. In addition, scanning electron microscope inspection exhibited cefazolin changed the morphology and size of the crystals greatly. A relatively higher amount of cefazolin additive caused a faster degradation and a lower compressive strength of calcium sulfate compared with those of uploaded samples. Furthermore, the extract of cefazolin-impregnated calcium sulfate impaired cell viability, and caused the death of osteoblast-like cells. The results of this study revealed that the cefazolin additives prolonged setting time, impaired mechanical strength, accelerated degradation, and caused cytotoxicity of the calcium sulfate bone-void filler. The aforementioned concerns should be considered during intra-operative applications.

Current Concepts of Fracture-Related Infection

Currently, fracture-related infection (FRI) still represents great challenges in front of orthopaedic surgeons, despite great advances that have been achieved regarding its diagnosis and treatment. Although both FRI and prosthetic joint infection (PJI) belong to osteoarticular infections and share similarities, FRI displays unique characteristics. Diagnosis of FRI is sometimes difficult owing to the nonspecific symptoms, and treatment is usually tricky, with a high risk of infection recurrence. In addition, the long disease course is associated with a significantly elevated risk of disability, both physically and psychologically. Moreover, such a disorder still poses heavy economic burdens to the patients, both personally and socially. Therefore, early diagnosis and reasonable treatment are the key issues for increasing the cure rate, decreasing the risks of infection relapse and disability, and improving the life quality and prognosis of the patients. In this review, we summarized the present concepts regarding the definition, epidemiology, diagnosis, and treatment of FRI.

Efficacy and safety of vancomycin-loaded calcium sulfate versus conventional surgical debridement for pediatric acute osteomyelitis: a retrospective study

BACKGROUND

The purpose of this study was to evaluate the safety and efficacy of vancomycin-loaded calcium sulfate beads and negative-pressure wound therapy (NPWT) in treating children with acute hematogenous osteomyelitis (AHOM).

METHODS

A retrospective cohort study was conducted from January 2017 to January 2020 examining children (n = 60) with AHOM who were treated with surgical debridement followed by vancomycin-loaded calcium sulfate beads and NPWT (n = 32) and compared to treatment by conventional surgical debridement (n = 28) followed by NPWT. Conventional surgical treatment consisted of fenestration of necrotic infected bone, debridement of surrounding soft tissue, and washing of the medullary canal before the application of NPWT. In the vancomycin group, the antibiotic-loaded beads were implanted after washing the medullary canal and before the application of NPWT. Epidemiological factors, complications during the procedure, outcomes at last follow-up (30.0 ± 11.7 months, range 13-58 months), and laboratory parameters were documented and compared between the two groups.

RESULTS

Good outcomes were achieved at last follow-up in 71.4% of the conventional treatment group and 75% of the vancomycin group. In the vancomycin group, it took a mean of 4.8 ± 2.5 days for CRP levels to decrease to 50% of initial inflammatory levels compared to 13 ± 9.6 days for the conventional treatment group (p = 0.001, t-test). The conventional group also had seven patients who underwent four or more surgeries whereas no patients in the vancomycin group underwent more than three surgeries (p = 0.013, chi-square test).

CONCLUSION

Localized vancomycin delivery with NPWT effective for treating cases of AHOM that required. No perioperative adverse reactions or complications occurred from this treatment method. Based on the shortened recovery period of CRP levels, prolonged administration of post-operational parenteral antibiotics can possibly be reduced with this treatment method.

Antibiotic-impregnated calcium sulfate for the treatment of pediatric hematogenous osteomyelitis

BACKGROUND

Antibiotic-impregnated calcium sulfate has excellent curative efficacy in chronic osteomyelitis. However, its curative efficacy in pediatric hematogenous osteomyelitis has not been sufficiently studied. The purpose of this study was to evaluate the curative effects of antibiotic-impregnated calcium sulfate in the treatment of pediatric hematogenous osteomyelitis.

METHODS

Overall, twenty-one pediatric patients with hematogenous osteomyelitis treated at our hospital between 2013 and 2018 were included for assessment. The clinical history, clinical manifestation, infection recurrence rate, sinus leakage, incision leakage, pathological fractures, bone growth and surgical procedures were analyzed.

RESULTS

The infection recurrence rate was 0% (0/21) at a minimum of 31 months (range 31 to 91 months) of follow-up. Postoperative incision leakage was found in one pediatric patient. Osteolysis was found in one pediatric patient. Acceleration of bone growth occurred in one pediatric patient. Retardation of bone growth occurred in one pediatric patient. Genu valgus deformity occurred in one pediatric patient.

CONCLUSIONS

Although noninfectious complications occurred, the curative effect of antibiotic-impregnated calcium sulfate in pediatric hematogenous osteomyelitis was satisfactory.

Bioactive glass in the treatment of chronic osteomyelitis in children: Description of four consecutive cases and literature review

INTRODUCTION

Chronic osteomyelitis in children is a rare condition. Debridement surgery, along with appropriate antibiotic therapy, is widely agreed to represent the best procedure in the treatment of chronic osteomyelitis but can result in an extensive dead space formation. In this study, we evaluated the use of bioactive glass to address dead space management.

METHODS

Four consecutive cases of chronic osteomyelitis treated with antibiotic therapy, one stage- surgical debridement and bioglass implantation between September 2016 and February 2017 were prospectively followed for a minimum of three years. Two cases followed acute hematogenous osteomyelitis, two cases followed fracture fixation. Clinical, histology, laboratory and radiographic findings were recorded. Primary endpoint was eradication of infection. Possible complication related to bioglass application were investigated.

RESULTS

All patients achieved healing at the latest follow-up of minimum three years. No successive surgical treatments were required at any time. No complications related to the bioglass were detected. Radiographic reconstruction of normal anatomy progressed through the years.

CONCLUSIONS

Bioglass for the treatment of dead space after surgical debridement appears a viable option in the treatment of chronic osteomyelitis in children.

Intramedullary Canal Injection of Vancomycin- and Tobramycin-loaded Calcium Sulfate: A Novel Technique for the Treatment of Chronic Intramedullary Osteomyelitis

Aim

In this study, we present a detailed surgical technique for treating chronic osteomyelitis (COM) of the intramedullary canal with injectable tobramycin and vancomycin-loaded calcium sulfate (CS).

Background

Chronic osteomyelitis of the long bones has been treated using antibiotic-impregnated polymethyl methacrylate (PMMA), which typically requires a second procedure for removal.

Technique

Removal of the infected intramedullary nail (if any), copious irrigation, canal reaming, and intramedullary canal injection of vancomycin- and tobramycin-loaded calcium sulfate as a single-stage procedure for the treatment of COM of long bones.

Conclusion

Intramedullary injection of vancomycin- and tobramycin-loaded CS can be used as a single-stage procedure for the treatment of long bone intramedullary COM. Further studies are necessary to compare the long-term outcomes of antibiotic-coated CS vs other antibiotic carriers for infection eradication.

Clinical significance

The authors have endeavored to explain the best surgical technique to eradicate long bones COM with injectable tobramycin and vancomycin-loaded CS.

How to cite this article

Elhessy AH, Rivera JC, Shu HT, et al. Intramedullary Canal Injection of Vancomycin- and Tobramycin-loaded Calcium Sulfate: A Novel Technique for the Treatment of Chronic Intramedullary Osteomyelitis. Strategies Trauma Limb Reconstr 2022;17(2):123–130.

Simulated large joint fluid model for evaluating intra-articular antibiotic delivery systems: initial evaluation using antibiotic-loaded calcium sulfate beads

Introduction: Local antimicrobial delivery via calcium sulfate (CaSO4) beads is used as an adjunctive treatment for periprosthetic joint infection. There is limited clinical information describing the performance of antimicrobial-loaded CaSO4 (ALCS) in large-scale applications. We developed a simulated large joint model to study properties of eluting ALCS. Methods: The in vitro testing platform was an adapted standardized model for tribological testing of prosthetic total hips and total knees (ASTM F732). The model was 70 mL total fluid volume, 25 % bovine serum, and 75 % phosphate-buffered saline, using ISO standard 14242-1 for human synovial fluid simulation. Four brands of CaSO4 were evaluated. Each 10 mL of CaSO4 was loaded with 1.2 grams (g) of tobramycin and 1 g of vancomycin powders. A 35 mL bead volume, equaling 175 beads, of each product was placed in incubated flasks. The test period was 6 weeks with scheduled interval fluid exchanges. Fluid samples were tested for antibiotic and calcium concentrations and pH. Results: Antibiotic elution showed an initial burst on Day 1, followed by a logarithmic reduction over 1 week. Tobramycin fully eluted within 2.5 weeks. Vancomycin showed sustained release over 6 weeks. Calcium ion concentrations were high, with gradual decrease after 3 weeks. All four CaSO4 products were inherently acidic. Fluid became more acidic with the addition of antibiotics primarily driven by vancomycin. Discussion: Clinicians should be cognizant of tobramycin elution burst with ALCS in large loads. The main driver of acidic pH levels was vancomycin. We propose that joint complications may result from lowered fluid acidity, and we suggest clinical study of synovial pH.

Outcome Analysis of the Use of Cerament® in Patients with Chronic Osteomyelitis and Corticomedullary Defects

Background: Chronic osteomyelitis (OM) is a progressive but mostly low-grade infection of the bones. The management of this disease is highly challenging for physicians. Despite systematic treatment approaches, recurrence rates are high. Further, functional and patient-reported outcome data are lacking, especially after osseous defects are filled with bioresorbable antibiotic carriers. Objective: To assess functional and patient-reported outcome measures (PROM) following the administration of Cerament^® G or V due to corticomedullary defects in chronic OM. Methods: We conducted a retrospective study from 2015 to 2020, including all patients who received Cerament^® for the aforementioned reason. Patients were diagnosed and treated in accordance with globally valid recommendations, and corticomedullary defects were filled with Cerament^® G or V, depending on the expected germ spectrum. Patients were systematically followed up, and outcome measures were collected during outpatient clinic visits. Results: Twenty patients with Cierny and Mader type III OM were included in this study and followed up for 20.2 ± 17.2 months (95%CI 12.1–28.3). Ten of these patients needed at least one revision (2.0 ± 1.3 revisions per patient (95%CI 1.1–2.9) during the study period due to OM persistence or local wound complications. There were no statistically significant differences in functional scores or PROMs between groups. Conclusion: The use of Cerament^® G and V in chronic OM patients with corticomedullary defects appears to have good functional outcomes and satisfactory PROMs. However, the observed rate of local wound complications and the OM persistence rate may be higher when compared to previously published data.

Efficacy Evaluation of Ciprofloxacin-Loaded Poly (Trimethylene Carbonate) Implants in the Treatment of Chronic Osteomyelitis

In this study, poly (trimethylene carbonate) (PTMC) with excellent biocompatibility was synthesized via ring-opening of TMC to prepare the Ciprofloxacin-loaded PTMC implants, and antibacterial effects in vitro or in vivo of the resulting implants were investigated to evaluate the potential for treating chronic osteomyelitis. The in vitro results showed the Ciprofloxacin-loaded PTMC implants could sustain release ciprofloxacin at a release amount of about 90 μg/d for 28 days and possessed excellent antibacterial effect, as evidenced by the smaller size of the antibacterial ring of 32.6 ± 0.64 mm and the biofilm inhibition of 60% after 28 days of release. The in vivo results showed that after 28 days of treatment, the body weight and the white blood cell counts of chronic-osteomyelitis-model rats in the treatment group reached 381.6 ± 16.8 g and (7.86 ± 0.91) ×10⁹/L, respectively, returning to normal rapidly compared with the control and blank group, indicating the remarkable antibacterial effect of the Ciprofloxacin-loaded PTMC implants. X-ray images and HE staining results also confirmed that most of the proximal and middle parts of the tibia returned to typical structures and new and trabecular bone had been formed for the rats in the treatment group, and no inflammatory cells were found as compared to the control and blank groups, after 28 days of treatment. The significant lower number of colonies of (9.92 ± 1.56) × 10 CFU/g in the treatment group also suggests that the Ciprofloxacin-loaded PTMC implants achieve a practical antibacterial effect through a local application.

Antibiotic-loaded calcium sulfate in clinical treatment of chronic osteomyelitis: a systematic review and meta-analysis

Background

Present work was aimed to gather accessible evidence on the eradication rates and related postoperative complications of antibiotic-loaded calcium sulfate (CS) as an implant in the treatment of chronic osteomyelitis (COM).

Methods

Databases including PubMed, EMBASE, Medline, Ovid and Cochrane library were searched from their dates of initiation until November 2021. Two independent authors scrutinized the relevant studies based on the effectiveness of radical debridement combined with antibiotic-loaded CS for COM; data extraction and quality assessment of the Methodological Index for Non-Randomized Studies (MINORS) criteria were also performed by the authors. In addition, clinical efficacy mainly depended on the evaluation of eradication rates and complications, and all the extracted data are pooled and analyzed by STATA 16.0.

Results

A total of 16 studies with 917 patients (920 locations) were recruited, with an overall eradication rate of 92%. Moreover, the overall reoperation rate, overall refracture rate, overall delayed wound healing rate, and the rate of aseptic wound leakage were 9.0%, 2.0%, 20.0%, and 12.0%, respectively. Moreover, the choice of tobramycin-loaded CS or vancomycin combined with gentamicin-loaded CS did not affect the eradication rate, and the incidence of postoperative complications in COM patients (all $$P>0.05$$ P > 0.05 ). The general quality of the included studies was fair.

Conclusions

Our meta-analysis indicated that the overall eradication rate of COM treated with antibiotic-loaded CS was 92%. Delayed healing is the most common postoperative complication. The choice of tobramycin-loaded CS or vancomycin combined with gentamicin-loaded CS did not affect the eradication rate and the incidence of postoperative complications in COM patients.

Treatment of chronic osteomyelitis with antibiotic-impregnated polymethyl methacrylate (PMMA) - the Cierny approach: is the second stage necessary?

Background

Chronic osteomyelitis is a challenge for orthopedic surgeons. Most patients with osteomyelitis receive two-stage management according to Cierny-Mader. The first stage includes radical debridement and insertion of an antibiotic-impregnated cement spacer (ACS) (beads, rods, nails, or blocks) into the bone defect. The second stage is performed 6–8 weeks later, when the spacer is removed and a cancellous autograft is placed within the bone defect. The possibility of ACS as definitive management for osteomyelitis, avoiding the second stage, is presented.

Methods

Sixteen patients with osteomyelitis received radical debridement and insertion of an ACS in all forms into the bone defect as a definitive management. In 8 patients, the tibia was infected, 4 had femur infection, 2 humerus, 1 fibula, and 1 ankle. The mean age at the time of the first stage of reconstruction was 49 years (range, 13–71 years). According to the Cierny-Mader classification, 1 patient was C-M IA, another was IB, 7 IIIA, 6 IIIB, and 1 was 4A. All B hosts had systemic illnesses. The mean follow-up period was 6 years (1.5–16 years).

Results

No patient exhibited radiographic evidence of excessive bone loss. Signs of recurrence of osteomyelitis were not noted in any of the patients, and no fractures had occurred by the last follow-up.

Conclusion

Our study suggests that a proportion of patients with planned retention of ACS appear to function well without requiring further surgical intervention, especially in elderly or vulnerable patients.

A comparison of the vancomycin calcium sulfate implantation versus fenestration decompression for the treatment of sclerosing osteomyelitis

OBJECTIVE

To compare the clinical efficacy of vancomycin calcium sulfate implantation and fenestration decompression in the treatment of sclerosing osteomyelitis.

METHOD

A retrospective analysis for 46 cases of sclerosing osteomyelitis were admitted to our department between June 2010 to June 2020. Twenty-one patients were treated with fenestration decompression, twenty-five patients were treated with vancomycin calcium sulfate implantation. The postoperative hospital stay, days of drainage tube placement, visual analogue scale scores, C-reactive protein and erythrocyte sedimentation rate were compared between the two groups.

RESULTS

The visual analogue scale scores of both groups were significantly lower than before treatment (p < 0.05), but the difference between them was not statistically significant. Patients treated by vancomycin calcium sulfate implantation had shorter postoperative hospital stay and days of drainage tube placement compared to those treated by fenestration decompression (p < 0.05). C-reactive protein and erythrocyte sedimentation rate in both groups were significantly lower than before treatment, but the improvement effect of vancomycin calcium sulfate implantation was better (p < 0.05).

CONCLUSION

Both treatment methods can relieve pain effectively. Compared with fenestration decompression, vancomycin calcium sulfate implantation can shorten the treatment time effectively, control the infection better.

Clinical Practice Guideline by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America: 2021 Guideline on Diagnosis and Management of Acute Hematogenous Osteomyelitis in Pediatrics

This clinical practice guideline for the diagnosis and treatment of acute hematogenous osteomyelitis (AHO) in children was developed by a multidisciplinary panel representing Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA). This guideline is intended for use by healthcare professionals who care for children with AHO, including specialists in pediatric infectious diseases, orthopedics, emergency care physicians, hospitalists, and any clinicians and healthcare providers caring for these patients. The panel's recommendations for the diagnosis and treatment of AHO are based upon evidence derived from topic-specific systematic literature reviews. Summarized below are the recommendations for the diagnosis and treatment of AHO in children. The panel followed a systematic process used in the development of other IDSA and PIDS clinical practice guidelines, which included a standardized methodology for rating the certainty of the evidence and strength of recommendation using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach. A detailed description of background, methods, evidence summary and rationale that support each recommendation, and knowledge gaps can be found online in the full text.

Culture-negative chronic hematogenous osteomyelitis in a two months old girl: a case report

Background

Previous articles have focused on the diagnosis and treatment of acute hematogenous osteomyelitis. Here, we present a case of chronic hematogenous osteomyelitis in a 2-month-old girl. The diagnostic procedure was unusual and difficult due to negative culture results.

Case presentation

A girl aged 2 months and 23 days had fever and swelling in her right lower leg for 7 days. On the basis of her medical history, physical, and histological examination results; and radiologic and magnetic resonance imaging findings, a diagnosis of chronic osteomyelitis was made. The patient underwent surgical treatment and was discharged successfully. The patient showed good recovery and no sequelae at the 12-month follow-up.

Conclusion

Hematogenous osteomyelitis in babyhood is different from that at any other age. Hematogenous osteomyelitis-related bone destruction in babyhood is more serious and occurs faster. The transition from acute hematogenous osteomyelitis to chronic hematogenous osteomyelitis takes only 7 days. To the best of our knowledge, this chronic hematogenous osteomyelitis patient is the youngest ever reported.

Treatment of Chronic Hematogenous Osteomyelitis in Children With Antibiotic Impregnated Calcium Sulphate

BACKGROUND

The purpose of this study was to evaluate the clinical and radiologic outcome of chronic hematogenous osteomyelitis (CHOM) in children, treated with single-stage debridement and dead space management using antibiotic impregnated calcium sulphate pellets.

METHODS

The authors retrospectively evaluated a consecutive series of 34 patients who presented with CHOM from 2011 to 2017. In each case, CHOM was classified according to the Beit CURE classification. Following thorough surgical debridement, the resulting dead space in the bone was filled with the antibiotic impregnated beads before primary closure.

RESULTS

Of the 31 patients available for follow up, effective regeneration of bone was confirmed in all cases, with radiographic bone healing typically observed at around 12 weeks. None of the children required reoperation for infection and none had recurrence of infection at the time of final review. The beads were completely absorbed within 3 months. No systemic adverse reactions to the local delivery of antibiotics were observed in this study.

CONCLUSIONS

The authors found that single-stage debridement in conjunction with antibiotic impregnated calcium sulphate was an effective means of treating CHOM in children, with effective eradication of infection in every case.

LEVEL OF EVIDENCE

Level IV-Retrospective case series. See instructions for authors for a complete description of levels of evidence.

Single-stage debridement with implantation of antibiotic-loaded calcium sulphate in 34 cases of localized calcaneal osteomyelitis

Background and purpose - The successful eradication of calcaneus infection with limb salvage remains a challenge. We describe the outcomes of cortical bone windowing followed by eggshell-like debridement and implantation of antibiotic-loaded calcium sulphate (CS) for localized (Cierny-Mader type III) calcaneal osteomyelitis (CO).Patients and methods - We report a retrospective study of 34 patients. Infection followed trauma or orthopedic surgery in 30 patients and hematogenous spread in 4 patients. 31 patients had a sinus tract, accompanied by a soft tissue defect in 3 patients. All patients received cortical bone windowing, debridement, multiple sampling, local implantation of vancomycin- and gentamicin-loaded CS, skin closure or flap coverage, and culture-specific systematic antibiotic treatment in a single-stage procedure. Patients were followed up for a median of 26 months.Results - Infection was eradicated in 29 patients after the single-stage surgery, and all of the 5 recurrent infections were cleared by repeated surgery without amputation. Other adverse events included 11 patients with aseptic wound leakage and 1 unrelated death. Compared with those before surgery, the median postoperative scores of the American Orthopaedic Foot & Ankle Society (AOFAS) ankle hindfoot scale (65 vs. 86 vs. 89) and the visual analog scale (VAS) for pain (6 vs. 3 vs. 1) improved at the 1-year and 2-year follow-up.Interpretation - This single-stage protocol, cortical bone windowing, and eggshell-like debridement combined with local implantation of antibiotic-loaded CS is effective in treating type III CO. However, the incidence of aseptic wound leakage is high.

Effects of Intraoperative Intrawound Antibiotic Administration on Spinal Fusion: A Comparison of Vancomycin and Tobramycin in a Rat Model

BACKGROUND

Local, intrawound use of antibiotic powder, such as vancomycin and tobramycin, in spinal fusion surgery has become an increasingly common prophylactic measure in an attempt to reduce rates of postsurgical infection. However, the effects of localized antibiotic delivery on fusion remain unclear. The objective of this study was to examine the in vivo effects of intraoperative local delivery of 2 antibiotics commonly used in bone-grafting surgery on spinal fusion outcomes in a rat model.

METHODS

Single-level (L4-L5), bilateral posterolateral intertransverse process lumbar fusion surgery was performed on 60 female Lewis rats (6 to 8 weeks of age) using syngeneic iliac crest allograft mixed with clinical bone-graft substitute and varying concentrations of antibiotics (n = 12 each): (1) control without any antibiotics, (2) low-dose vancomycin (14.3 mg/kg), (3) high-dose vancomycin (71.5 mg/kg), (4) low-dose tobramycin (28.6 mg/kg), and (5) high-dose tobramycin (143 mg/kg). Eight weeks postoperatively, fusion was evaluated via micro-computed tomography (µCT), manual palpation, and histological analysis, with blinding to treatment group. In the µCT analysis, fusion-mass volumes were measured for each rat. Each spine specimen (L4-L5) was rated (manual palpation score) on a scale of 2 to 0 (2 = fused, 1 = partially fused, and 0 = non-fused).

RESULTS

The mean fusion-mass volume on µCT (mm) was as follows: control, 29.3 ± 6.2; low-dose vancomycin, 26.3 ± 8.9; high-dose vancomycin, 18.8 ± 7.9; low-dose tobramycin, 32.7 ± 9.0; and high-dose tobramycin, 43.8 ± 11.9 (control versus high-dose vancomycin, p < 0.05; and control versus high-dose tobramycin, p < 0.05). The mean manual palpation score for each group was as follows: control, 1.46 ± 0.58; low-dose vancomycin, 0.86 ± 0.87; high-dose vancomycin, 0.68 ± 0.62; low-dose tobramycin, 1.25 ± 0.71; and high-dose tobramycin, 1.32 ± 0.72 (control versus high-dose vancomycin, p < 0.05). The histological analyses demonstrated a similar trend with regard to spinal fusion volume.

CONCLUSIONS

Intraoperative local application of vancomycin, particularly at a supraphysiological dosage, may have detrimental effects on fusion-mass formation. No inhibitory effect of tobramycin on fusion-mass formation was observed.

CLINICAL RELEVANCE

When spine surgeons decide to use intraoperative intrawound antibiotics in spinal fusion surgery, they should weigh the reduction in surgical site infection against a possible inhibitory effect on fusion.