Fracture-related infection

Bacterial DNA enrichment for low-inoculum fracture-related infection diagnostic using high-throughput sequencing

One of the main barriers for the implementation of metagenomic sequencing in routine diagnosis of infectious diseases is the presence of host DNA. While several enrichment methods are likely to overcome this issue, their effectiveness for specimens such as bone in the case of chronic infections remains to be determined. We compared the relevance of two methods for bacterial DNA enrichment when compared to a reference protocol during pretreatment of bone samples from fracture-related infections before HTS by both Illumina Miseq and Oxford Nanopore Technology (ONT). The bacterial/human DNA ratio was higher for either protocols than the reference technique (p = 0.00012), without any significant difference between them. HTS sensitivity over culture ranged from 21.7 % to 85 %. The ability of the studied protocols to improve the bacterial/human DNA ratio depends on the sequencing technique employed. In this context, there is room for improvement in enhancing the sensitivity of HTS for diagnostic purpose.

Bone consolidation under septic condition and hardware retention: about 69 patients

INTRODUCTION

Management of infection on internal fixation hardware is particularly complex. The main aim of the present study was to assess bone consolidation rates under septic conditions in patients treated for bone and joint infection (BJI) with hardware retention. Secondary objectives were to determine a time limit beyond which it is unreasonable to retain hardware, and to assess risk factors for non-consolidation and functional results. The study hypothesis was that bone consolidation is possible under septic conditions without hardware exchange.

MATERIAL AND METHOD

A single-center retrospective observational study was conducted on 69 patients for the period January 1, 2009 to December 31, 2019. We included all patients aged over 15 years with infection after internal fixation or fusion whose files had been discussed in the multidisciplinary team meeting during the study period. Bone healing was screened for on X-ray or CT. Study data comprised type of fracture, smoking status, time to treatment for open fracture, initial surgery time, type of hardware, interval between fixation and revision, and type of irrigation. Functional results were assessed at follow-up: walking, pain, return to work and SF12 and QuickDASH scores.

RESULTS

The bone healing rate was 73.5% (50/68 patients) at a mean 24 weeks (range, 6-68 weeks). Time to revision did not significantly impact consolidation: 60% for 2 weeks (6/10 cases), 80% for 2-10 weeks (35/40 cases), and 64% for >10 weeks (9/14 cases) (p = 0.28). Smoking, longer initial surgery time and Gustilo type IIIb or IIIc were significant risks factors for non-consolidation.

DISCUSSION

Bone consolidation under septic conditions with hardware retention adhering to an established medical and surgical protocol was reliable and straightforward, without extra morbidity. These findings are encouraging, and in line with the literature. We were unable to determine a time limit beyond which hardware prevented healing.

LEVEL OF EVIDENCE

IV; descriptive epidemiological study.

Low and high body mass index and lower numbers of screws in the articular segment are risk factors for non-union of distal humeral fractures in the elderly: A multi-center retrospective study (TRON study)

Background

Distal humerus fracture in the elderly is a challenging fracture for orthopedic surgeons. Non-union is one of the serious complications of distal humerus fracture after surgery. This retrospective multicenter study aimed to estimate the incidence of distal humeral non-union after open reduction and internal fixation, determine factors related to non-union, and compare the postoperative results of cases with non-union to cases with the union.

Methods

Among 423 patients diagnosed with distal humeral fracture and who were treated by surgical therapy in 2010-2020 from our database called TRON. Only 190 subjects met the inclusion criteria. We performed a logistic regression analysis with the presence of non-union as the response variable to examine risk factors. We compare the Mayo Elbow Performance Scores of cases with non-union to cases with the union.

Results

Non-union occurred after surgery in 15 patients (7.9%). The logistic regression analysis showed that body mass index<20 kg/m2 and ≥25 kg/m2, and ≤3 screws in the articular segment were significant explanatory factors for non-union (odds ratio 10.4 and 47.8, respectively). The Mayo Elbow Performance Scores were significantly worse in patients with non-union.

Discussion

Low and high body mass index and three or fewer screws in the articular segment might be risk factors for non-union of distal humerus fracture in the elderly. Non-union is associated with poor clinical outcomes.

[Diagnostic and therapeutic work-up of infected tibial nonunion]

BACKGROUND

The failure of bone fracture healing is one of the major complications of fracture treatment, especially of the tibia due to its limited soft tissue coverage and high rate of open injuries. Although implant development is constantly progressing and modern surgical techniques are continuously improving, infected tibial nonunion plays a decisive role in terms of its variable clinical presentation.

OBJECTIVE

This article provides guidelines for the successful surgical treatment of infected tibial nonunion.

MATERIAL AND METHOD

Strategies are presented to identify infection as a cause of failure of fracture healing and to achieve infection and bone healing.

RESULTS

A significant amount of tibial nonunions primarily thought to be aseptic ultimately turn out to be infected nonunions.

CONCLUSION

The treatment of infected tibial nonunion requires extensive clinical, radiological and laboratory diagnostics as well as a profound biomechanical and biological understanding of the bone situation. This is the only way to achieve rapid osseous healing with as few revision interventions as possible.

[Translated article] Risk factors for infection of tibial plateau fractures

INTRODUCTION

Tibial plateau fractures are injuries prone to postoperative infection, with its reported incidence being higher than that of other fractures, between 5% and 12%. The primary objectives of this study were to quantify the postoperative infection rate of internal fixation of tibial plateau fractures (TPFs) and to identify the risk factors for this.

MATERIAL AND METHODS

Retrospective cohort study including patients who underwent TPF osteosynthesis between 2015 and 2020, in the same center. The study population was divided into two groups, according to the presence or absence of postoperative infection. Demographic variables related to the fracture, surgical parameters, as well as the need for reoperation were collected. Finally, in the case of debridement, the number of positive cultures and the pathogen responsible for the infection were collected, as well as the treatment applied.

RESULTS

One hundred and twenty-four patients were included, with a total of 14 infections (global infection rate of 11.3%). Risk factors for developing infection were open fractures (p=.002), Schatzker V and VI type fractures (p=.002) and the use of external fixation (p<.001). Regarding the surgical variables, only the longest ischemia time (p=.032) was identified as a risk factor. Staphylococcus aureus was the most frequently identified microorganism (43%), followed by Enterobacter cloacae (35.7%).

CONCLUSION

The overall infection rate after osteosynthesis of tibial plateau fractures was 11.3%. Different factors are associated with a higher risk of infection, including diabetes mellitus, open fractures, the use of external fixation, a higher grade in the Schatzker classification or a longer intraoperative ischemia time.

A population-based epidemiological and health economic analysis of fracture-related infection

Aims

The aim of this study was to perform the first population-based description of the epidemiological and health economic burden of fracture-related infection (FRI).

Methods

This is a retrospective cohort study of operatively managed orthopaedic trauma patients from 1 January 2007 to 31 December 2016, performed in Queensland, Australia. Record linkage was used to develop a person-centric, population-based dataset incorporating routinely collected administrative, clinical, and health economic information. The FRI group consisted of patients with International Classification of Disease 10th Revision diagnosis codes for deep infection associated with an implanted device within two years following surgery, while all others were deemed not infected. Demographic and clinical variables, as well as healthcare utilization costs, were compared.

Results

There were 111,402 patients operatively managed for orthopaedic trauma, with 2,775 of these (2.5%) complicated by FRI. The development of FRI had a statistically significant association with older age, male sex, residing in rural/remote areas, Aboriginal or Torres Strait Islander background, lower socioeconomic status, road traffic accident, work-related injuries, open fractures, anatomical region (lower limb, spine, pelvis), high injury severity, requiring soft-tissue coverage, and medical comorbidities (univariate analysis). Patients with FRI had an eight-times longer median inpatient length of stay (24 days vs 3 days), and a 2.8-times higher mean estimated inpatient hospitalization cost (AU$56,565 vs AU$19,773) compared with uninfected patients. The total estimated inpatient cost of the FRI cohort to the healthcare system was AU$156.9 million over the ten-year period.

Conclusion

The results of this study advocate for improvements in trauma care and infection management, address social determinants of health, and highlight the upside potential to improve prevention and treatment strategies.

Risk factors for infection of tibial plateau fractures

INTRODUCTION

Tibial plateau fractures are injuries prone to postoperative infection, with its reported incidence being higher than that of other fractures, between 5% and 12%. The primary objectives of this study were to quantify the postoperative infection rate of internal fixation of tibial plateau fractures (TPF) and to identify the risk factors for this.

MATERIAL AND METHODS

Retrospective cohort study including patients who underwent TPF osteosynthesis between 2015 and 2020, in the same center. The study population was divided into two groups, according to the presence or absence of postoperative infection. Demographic variables related to the fracture, surgical parameters, as well as the need for reoperation were collected. Finally, in the case of debridement, the number of positive cultures and the pathogen responsible for the infection were collected, as well as the treatment applied.

RESULTS

One hundred and twenty-four patients were included, with a total of 14 infections (global infection rate of 11.3%). Risk factors for developing infection were open fractures (P=.002), Schatzker V and VI type fractures (P=.002) and the use of external fixation (P<.001). Regarding the surgical variables, only the longest ischemia time (P=.032) was identified as a risk factor. S. aureus was the most frequently identified microorganism (43%), followed by E. cloacae (35.7%).

CONCLUSION

The overall infection rate after osteosynthesis of tibial plateau fractures was 11.3%. Different factors are associated with a higher risk of infection, including diabetes mellitus, open fractures, the use of external fixation, a higher grade in the Schatzker classification or a longer intraoperative ischemia time.

Hematoma-like dynamic hydrogelation through natural glycopeptide molecular recognition for infected bone fracture repair

Infected bone fractures remain a major clinical challenge for orthopedic surgeons. From a tissue regeneration perspective, biomaterial scaffolds with antibacterial and osteoinductive activities are highly desired, while advanced materials capable of mimicking the pathological microenvironment during the healing process of infected tissues remain an area deserving more research. Hematoma, the gel-like blood coagulum, plays an essential role in bone fracture repair because of its ability to serve as a dynamic and temporary scaffold with cytokines for both pathogen elimination and tissue healing. In light of this, we designed a dynamic hydrogel with hematoma-like antimicrobial or reparative performance for infected bone fracture repair in this study. The proposed dynamic hydrogel network was based on the reversible recognition of a natural glycopeptide antibiotic vancomycin (Van) and its target dipeptide D-Ala-D-Ala (AA), which could serve as a hematoma-like scaffold for obliterating bacteria in the fracture region and promoting bone repair by introducing an endogenous osteogenic peptide (OGP). In vivo experiments demonstrated that the hydrogel could rapidly eradicate bacteria, improve bone regeneration and restore the local inflammatory microenvironment. Together, findings from this study imply that the use of hematoma-like dynamic hydrogel could lead to a biomimetic revolution in surgical strategies against susceptible bone fractures.

Incidence and risk factors of recurrence in limb osteomyelitis patients after antibiotic-loaded cement spacer for definitive bone defect treatment

Aims

This study was designed to characterize the recurrence incidence and risk factors of antibiotic-loaded cement spacer (ALCS) for definitive bone defect treatment in limb osteomyelitis.

Methods

We included adult patients with limb osteomyelitis who received debridement and ALCS insertion into the bone defect as definitive management between 2013 and 2020 in our clinical centre. The follow-up time was at least two years. Data on patients' demographics, clinical characteristics, and infection recurrence were retrospectively collected and analyzed.

Results

In total, 314 patients with a mean age of 52.1 years (SD 12.1) were enrolled. After a mean of 50 months' (24 to 96) follow-up, 53 (16.9%) patients had infection recurrence including 32 tibiae, ten femora, ten calcanea, and one humerus. Of all patients with recurrence, 30 (9.6%) occurred within one year and 39 (12.4%) within two years. Among them, 41 patients needed reoperation, five received antibiotics treatment only, and seven ultimately required amputations. Following multivariable analysis, we found that patients infected with Gram-negative bacilli were more likely to have a recurrence (odds ratio (OR) 2.38, 95% confidence interval (CI) 1.20 to 6.94; p = 0.046) compared to Staphylococcus aureus; segmental bone defects (OR 5.25, 95% CI 1.80 to 15.26; p = 0.002) and smoking (OR 3.00, 95% CI 1.39 to 6.50; p = 0.005) were also independent risk factors for recurrence after treatment.

Conclusion

Permanent ALCS might be an alternative strategy for definitive bone defect management in selected osteomyelitis cases. However, the overall high recurrence found suggests that it should be cautiously treated. Additionally, segmental defects, Gram-negative infections, and smoking were associated with an increased risk of infection recurrence.

Complications associated with single-level bone transport for the treatment of tibial bone defects caused by fracture-related infection

BACKGROUND

The purpose of this study was to report the outcomes of single-level bone transport with a unilateral external fixator for treatment of proximal, intermediate and distal tibial bone defects caused by fracture-related infection (FRI) and compare their complications.

METHODS

The clinical records and consecutive X-ray photographs of patients with tibial bone defects treated by single-level bone transport using a unilateral external fixator (Orthofix Limb Reconstruction System) were analyzed retrospectively, from January 2012 to December 2018. Patients were divided into the proximal group (P, n = 19), intermediate group (I, n = 25), and distal group (D, n = 18) according to the location of the tibial bone defect. The Association for the Study and Application of the Method of Ilizarov (ASAMI) standard was applied to assess the bone and functional outcomes and postoperative complications evaluated by the Paley classification.

RESULTS

A total of 62 participants were included in this study, with a median age of 36 ± 7.14 years. Sixty patients with tibial bone defects caused by FRI were successfully treated by single-level bone transport using a unilateral external fixator, with a mean bone union time (BUT) of 7.3 ± 1.71 months. According to the ASAMI criteria, there were statistical differences in bone and function results between the three groups (P vs. I vs. D, P < 0.001). The excellent and good rate of bone result in the intermediate group was higher than the other (P vs. I vs. D, 73.6% vs. 84% vs. 66.7%), and the excellent and good rate of function result in the proximal group was the highest (P vs. I vs. D, 84.2% vs. 80% vs. 73.3%). Complications were observed in 29 out of 62 patients (46.7%), with pin tract infection being the most common (14.8%), followed by axial deviation (14.8%), muscle contractures (12.7%), joint stiffness (12.7%), and soft tissue incarceration (12.7%). Other complications included delayed consolidation (12.7%), delayed union (6.3%), nonunion (4.2%), and neurological injury (8.5%). Two patients (3.2%) required below-knee amputation due to uncontrollable infection and previous surgery failure.

CONCLUSIONS

Pin tract infection was the most common complication in tibial bone transport using an external fixator. Complications of distal tibial bone transport are more severe and occur at a higher rate than in other parts. Axial deviation mostly occurred in the intermediate tibial bone transport.

Bifocal versus trifocal bone transport for the management of tibial bone defects caused by fracture-related infection: a meta-analysis

BACKGROUND

The purpose of this meta-analysis was to compare the efficacy and outcomes of bifocal bone transport (BFT) and trifocal bone transport (TFT) for the treatment of tibial bone defects caused by fracture-related infection (FRI).

METHODS

The literature searches of Cochrane Library, Embase, Google Scholar databases, PubMed/Medline, and Web of Science for literature published up to September 20, 2022, were performed. The quality of the included studies was evaluated according to the MINORS scale. Patients were divided into the BFT group and the TFT group, depending on the site of the osteotomy. The demographic data, defect size (DS), external fixation time (EFT), external fixation index (EFI), bone and functional results, complications, and autologous bone grafting (ABG) were extracted and analyzed using the Review Manager software (version 5.3).

RESULTS

Five studies included 484 patients with tibial bone defects treated by bone transport investigated in this meta-analysis, with a mean bone defect of 9.3 cm. There were statistical differences in DS (MD =  - 2.38, 95% CI - 3.45 to - 1.32, P < 0.0001), EFT (MD = 103.44, 95% CI 60.11 to 146.77, P < 0.00001), and EFI (MD = 26.02, 95% CI 14.38 to 37.65, P < 0.00001) between BFT group and TFT group. There was no statistical difference in bone results (RR = 0.98, 95% CI 0.91 to 1.06, P = 0.67), functional results (RR = 0.94, 95% CI 0.82 to 1.07, P = 0.37), complications (OR = 1.57, 95% CI 0.59 to 4.14, P = 0.36), and ABG (RR = 1.2, 95% CI 0.78 to 1.84, P = 0.42) between two groups.

CONCLUSIONS

TFT was a feasible and practical method in the treatment of massive tibial bone defects caused by FRI to receive shorter EFT and satisfactory bone and functional results.

Antibiotic-loaded hydroxyapatite scaffolds fabricated from Nile tilapia bones for orthopaedics

This work aimed to develop new antibiotic-coated/ antibiotic-loaded hydroxyapatite (HAp) scaffolds for orthopaedic trauma, specifically to treat the infection after fixation of skeletal fracture. The HAp scaffolds were fabricated from the Nile tilapia (Oreochromis niloticus) bones and fully characterized. The HAp scaffolds were coated with 12 formulations of poly (lactic-co-glycolic acid) (PLGA) or poly (lactic acid) (PLA), blended with vancomycin. The vancomycin release, surface morphology, antibacterial properties, and the cytocompatibility of the scaffolds were conducted. The HAp powder contains elements identical to those found in human bones. This HAp powder is suitable as a starting material to build scaffolds. After the scaffold fabrication, The ratio of HAp to β-TCP changed, and the phase transformation of β-TCP to α-TCP was observed. All antibiotic-coated/ antibiotic-loaded HAp scaffolds can release vancomycin into the phosphate-buffered saline (PBS) solution. PLGA-coated scaffolds obtained faster drug release profiles than PLA-coated scaffolds. The low polymer concentration in the coating solutions (20%w/v) gave a faster drug release profile than the high polymer concentration (40%w/v). All groups showed a trace of surface erosion after being submerged in PBS for 14 days. Most of the extracts can inhibit Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus (MRSA). The extracts not only caused no cytotoxicity to Saos-2 bone cells but also can increase cell growth. This study demonstrates that it is possible to use these antibiotic-coated/ antibiotic-loaded scaffolds in the clinic as an antibiotic bead replacement.

Wound alpha defensin levels are significantly higher in patients with fracture related infection: A pilot, prospective cohort study

BACKGROUND

In absence of frank purulence, wound cultures represent 'gold-standard' for diagnosis of fracture related infection (FRI). However, these are time-intensive, and may be falsely negative, necessitating the need for accurate and rapid biomarker-based diagnosis. We conducted this study to determine the accuracy of 3 wound-based biomarkers for the diagnosis of FRI.

METHODS

This was a prospective cohort study on adult patients who underwent an operative procedure for an upper or lower limb fracture. Wound fluid levels of alpha-defensin (AD), neutrophil elastase (NE) and IL-6 were evaluated on post-operative day 2, and patients were followed up for one month. Patients were categorized as cases (FRI) or controls (no FRI), on the basis of the consensus definition of FRI. Univariate analysis, along with receiver operating characteristic (ROC) analysis was performed.

RESULTS

48 patients were included. AD levels showed a 2.6-fold elevation in cases (n = 26, Median = 23.74 µg/ml) as compared to controls (n = 22, Median = 8.78 µg/ml). The area under the curve for this variable was 0.71 (95% Confidence Intervals = 0.56 - 0.86). The levels of NE and IL-6 were not significantly different between cases and controls.

CONCLUSION

Wound AD levels are significantly elevated in patients with FRI. However, these results need to be validated in a larger cohort of patients before it can be used as a biomarker of FRI.

A less invasive operative method using a medial cannulated cancellous screw and single plate fixation for the treatment of transcondylar fracture of the humerus in elderly patients in multicenter (TRON group) study

BACKGROUND

Double plate fixation for transcondylar fracture (TCF) tends to be more invasive to the soft tissue, and often carries a higher risk of postoperative complications, including ulnar nerve neuropathy. This study presents the outcomes of TCF of the distal humerus between patients treated with a single plate and cannulated cancellous screw fixation and patients treated with double plate fixation.

METHODS

Between 2011 and 2021, 371 cases involving treatment of distal humeral fracture were recorded in our multicenter (named TRON group) database. Patients of ≥ 65 years of age with TCF treated with opeb n reduction and internal fixation were included. Clinical outcomes were assessed by the Mayo elbow performance score, range of motion, and total elbow arc joint. Complications included fracture-related infection (FRI) and ulnar neuropathy.

RESULTS

There were significant differences in the average operative time (CCS group vs. Plate group: 119.0 min vs. 186.5 min; p < 0.001) and average tourniquet time (CCS group vs. Plate group: 91.5 min vs. 121.0 min; p < 0.001). FRI occurred as a complication in the Plate group (n = 6). The rates of FRI did not differ to a statistically significant extent (CCS group vs. Plate group: 0% vs. 9.2%; p = 0.477). No patients underwent reoperation. The rate of sensory symptoms in the Plate group was higher than that in the CCS group (CCS group: none [n = 25], numbness [n = 1] vs. Plate group: none [n = 57], numbness [n = 15], sensory depression [n = 2]; p = 0.039).

DISCUSSION

Among patients of ≥ 65 years of age with TCF, the clinical outcomes of patients treated with medial CCS and lateral/posterolateral plate did not differ from those of patients who received double plate fixation, and the former treatment was associated with significantly fewer complications, including ulnar nerve palsy. In addition to double plate fixation, this less invasive method of medial CCS and single plate fixation should be considered as a treatment option for TCF in elderly patients.

Current therapeutic interventions combating biofilm-related infections in orthopaedics : a systematic review of in vivo animal studies

Aims

Biofilm-related infection is a major complication that occurs in orthopaedic surgery. Various treatments are available but efficacy to eradicate infections varies significantly. A systematic review was performed to evaluate therapeutic interventions combating biofilm-related infections on in vivo animal models.

Methods

Literature research was performed on PubMed and Embase databases. Keywords used for search criteria were “bone AND biofilm”. Information on the species of the animal model, bacterial strain, evaluation of biofilm and bone infection, complications, key findings on observations, prevention, and treatment of biofilm were extracted.

Results

A total of 43 studies were included. Animal models used included fracture-related infections (ten studies), periprosthetic joint infections (five studies), spinal infections (three studies), other implant-associated infections, and osteomyelitis. The most common bacteria were Staphylococcus species. Biofilm was most often observed with scanning electron microscopy. The natural history of biofilm revealed that the process of bacteria attachment, proliferation, maturation, and dispersal would take 14 days. For systemic mono-antibiotic therapy, only two of six studies using vancomycin reported significant biofilm reduction, and none reported eradication. Ten studies showed that combined systemic and topical antibiotics are needed to achieve higher biofilm reduction or eradication, and the effect is decreased with delayed treatment. Overall, 13 studies showed promising therapeutic potential with surface coating and antibiotic loading techniques.

Conclusion

Combined topical and systemic application of antimicrobial agents effectively reduces biofilm at early stages. Future studies with sustained release of antimicrobial and biofilm-dispersing agents tailored to specific pathogens are warranted to achieve biofilm eradication.

Cite this article: Bone Joint Res 2022;11(10):700–714.

Masquelet technique with radical debridement and alternative fixation in treatment of infected bone nonunion

Background

Infected bone nonunion is the toughest problem in fracture-related infection, leading to high disability and recurrence. The aim of this study was to evaluate the effectiveness of the Masquelet technique with radical debridement and alternative fixation in the management of infected bone nonunion.

Patients and Methods

A retrospective study of prospectively collected data in two trauma centers was performed from 2016 to 2020. Patients diagnosed as infected bone nonunion were included in this study. The initial implant was removed and all patients received a two-stage Masquelet procedure with radical debridement and alternative fixation. The disappearance of inflammatory manifestations and regression of infection indicators (such as interleukin-6 (IL-6), C-reactive protein, white blood cell count) to the normal range were regarded as radical debridement. The alternative fixation depended on local soft tissue conditions. Results were evaluated according to clinical and radiographic assessment and patient satisfaction.

Results

A total of 23 patients were included in our study. Six of them received internal fixation, while the other 17 received external fixation. Of the 23 cases, 21 were successfully reconstructed without infection recurrence, except 2 reinfected cases. Mean full weight bearing time was 6.6 months follow-up post last surgery. Out of the 23, 20 cases had satisfactory functional outcomes without additional bone or soft tissue comorbidities. Discrepancies in leg length and joint stiffness were observed in three cases and marked as unsatisfied results.

Conclusions

Infected bone nonunion can be successfully managed using the Masquelet technique under radical debridement combined with an alternative fixation method.

Implant surface culture may be a useful adjunct to standard tissue sampling culture for identification of pathogens accounting for fracture-device-related infection: a within-person randomized agreement study of 42 patients

BACKGROUND AND PURPOSE

Identification of pathogens causing fracture-device-related infection (FDRI) is always a challenge as the positive rate of standard tissue sampling culture (TSC) remains unsatisfactory. This study evaluates the efficiency of implant surface culture (ISC) as an adjunct to standard TSC for identification of FDRI-associated microorganisms.

PATIENTS AND METHODS

Between November 2020 and March 2022, patients diagnosed with FDRI defined by the International Fracture-Related Infection (FRI) Consensus Group, and indicated for implant removal, underwent both methods for bacteria detection. The test order of ISC and TSC was randomly selected for each patient included, as a within-person randomized design. For ISC, the recovered implants were gently covered with tryptic soy agar after rinsing with normal saline twice, and then incubated at 37℃ 5% CO2 for up to 14 days. For TSC, 5 specimens were sampled and sent to the Clinical Laboratory of Southern Medical University Nanfang Hospital, Guangzhou, for culture and identification.

RESULTS

42 consecutive patients were included, with a mean age of 46 years. The most frequent infection site and implant type were the tibia (21 cases) and plates with screws (30 cases), respectively. Altogether 21 patients were found with positive outcomes by both methods, and the identified pathogens were consistent. ISC found an additional 15 patients showing positive results, which were negative by TSC. Furthermore, the mean culture time of ISC was shorter than that of TSC (1.5 days vs. 3.2 days).

INTERPRETATION

ISC may be a useful adjunct to TSC for detection of bacteria causing FDRI, with a relatively higher positive rate and a shorter culture time.

Concentrations of co-administered vancomycin and meropenem in the internal dead space of a cannulated screw and in cancellous bone adjacent to the screw - Evaluated by microdialysis in a porcine model

BACKGROUND

Cannulated screws are often used in the management of open lower extremity fractures. These fractures exhibit broad contamination profiles, necessitating empirical Gram-positive and Gram-negative antibiotic coverage. To ensure full antibiotic protection of the cannulated screw and the bone tissue, it is generally accepted that target tissue antibiotic concentrations, as a minimum, reach and remain above relevant epidemiological cut-off minimal inhibitory concentrations (T>MIC) for a sufficient amount of time.

METHODS

8 female pigs were included. Microdialysis catheters were placed in the internal dead space of a cannulated screw placed in tibial cancellous bone, in tibial cancellous bone adjacent to the screw (mean distance to the screw: 3 mm), and in cancellous bone on the contralateral tibia. Following single-dose simultaneous intravenous administrations of vancomycin (1000 mg) and meropenem (1000 mg), microdialysates and plasma were dynamically sampled over 8 h. The applied MIC targets ranged from 1 to 4 µg/mL for vancomycin and 0.125-2 µg/mL for meropenem RESULTS: For both drugs, and for all MIC targets investigated (except for the high vancomycin target: 4 µg/mL), the internal dead space of the cannulated screw had the shortest T>MIC. At the low MIC targets T>MIC ranged between 88 and 449 min across sampling sites for vancomycin (1 µg/mL), and 148-406 min for meropenem (0.125 µg/mL). For the high MIC targets, T>MIC ranged between 3 and 446 min for vancomycin (4 μg/mL) and 17-181 min for meropenem (2 μg/mL). Vancomycin displayed longer T>MIC (2 and 4 μg/mL), higher area under the concentration time curve (AUC_0-last) and peak drug concentration in the proximal tibial cancellous bone without a screw nearby. For meropenem, only the cancellous bone AUC_0-last was significantly higher on the side with no screw.

CONCLUSION

We found short T>MIC, particularly for the high MIC targets for vancomycin and meropenem, both inside the cannulated screw and in cancellous bone adjacent to the screw. The presence of a cannulated screw impaired the penetration of especially vancomycin into cancellous bone adjacent to the screw. More aggressive or different vancomycin and meropenem approaches may be considered to encompass contaminating differences and to ensure a theoretically more sufficient antibiotic protection of cannulated screws when used in the management of open lower extremity fractures.

What Factors Affect Outcome in the Treatment of Fracture-Related Infection?

This international, multi-center study investigated the effect of individual components of surgery on the clinical outcomes of patients treated for fracture-related infection (FRI). All patients with surgically treated FRIs, confirmed by the FRI consensus definition, were included. Data were collected on demographics, time from injury to FRI surgery, soft tissue reconstruction, stabilization and systemic and local anti-microbial therapy. Patients were followed up for a minimum of one year. In total, 433 patients were treated with a mean age of 49.7 years (17−84). The mean follow-up time was 26 months (range 12−72). The eradication of infection was successful in 86.4% of all cases and 86.0% of unhealed infected fractures were healed at the final review. In total, 3.3% required amputation. The outcome was not dependent on age, BMI, the presence of metalwork or time from injury (recurrence rate 16.5% in FRI treated at 1−10 weeks after injury; 13.1% at 11−52 weeks; 12.1% at >52 weeks: p = 0.52). The debridement and retention of a stable implant (DAIR) had a failure rate of 21.4%; implant exchange to a new internal fixation had a failure rate of 12.5%; and conversion to external fixation had a failure rate of 10.3% (adjusted hazard ratio (aHR) DAIR vs. Ext Fix 2.377; 95% C.I. 0.96−5.731). Tibial FRI treated with a free flap was successful in 92.1% of cases and in 80.4% of cases without a free flap (HR 0.38; 95% C.I. 0.14−1.0), while the use of NPWT was associated with higher recurrence rates (HR 3.473; 95% C.I. 1.852−6.512). The implantation of local antibiotics reduced the recurrence from 18.7% to 10.0% (HR 0.48; 95% C.I. 0.29−0.81). The successful treatment of FRI was multi-factorial. These data suggested that treatment decisions should not be based on time from injury alone, as other factors also affected the outcome. Further work to determine the best indications for DAIR, free flap reconstruction and local antibiotics is warranted.

Risk factors for fracture-related infection after open reduction and internal fixation of proximal humerus fractures: A multicenter retrospective study of 496 fractures (TRON group study)

INTRODUCTION

One of the complications of the surgical therapy for proximal humerus fractures is fracture-related infection (FRI). This multicenter study aimed to investigate the incidence of FRI and clarify the risk factors associated with FRI in patients receiving open reduction and internal fixation for proximal humerus fracture.

MATERIAL AND METHODS

Among 684 patients diagnosed as having proximal humerus fracture and who were treated by surgical therapy in 13 institutions (named TRON group) from 2015 through 2020, 496 patients (men, n = 134, women, n = 362; mean [SD] age, 68.5 [14.5] years; mean [SD] body mass index [BMI], 23.0 [4.4] kg/m²) were included as subjects. Excluded were 188 patients due to less than 12 month's follow-up, patients who underwent osteosynthesis using neither plate nor nail and those with open fracture. We extracted the following as risk factors of FRI: sex, BMI, smoking status, diabetes, glenohumeral fracture dislocation, fracture classification, approach, implant, waiting period, type of anesthesia, operative time and blood loss during surgery. We conducted logistic regression analysis to investigate the risk factors of FRI using these extracted items as explanatory variables and the presence or absence of FRI as the response variable.

RESULT

FRI occurred after surgery for proximal humerus fracture in 9 of the 496 patients (1.8%). The causative organism was methicillin-susceptible Staphylococcus aureus in 4 patients, Pseudomonas aeruginosa in one patient and Enterococcus faecalis in one patient. In the other 3 patients, causative organisms were not detected. The univariate analysis showed significant differences for present of glenohumeral fracture dislocation (p = 0.004). Logistic regression analysis showed glenohumeral fracture dislocation to be the significant explanatory factor for FRI (odds ratio 12.3, p = 0.0375).

CONCLUSION

This study revealed an infection rate following open reduction and internal fixation of proximal humerus fracture of 1.8% (9 patients) and that Staphylococcus was the most frequent causative organism. Glenohumeral fracture dislocation is a significant risk for postoperative FRI.

Application of 68Ga-citrate PET/CT for differentiating periprosthetic joint infection from aseptic loosening after joint replacement surgery

AIMS

We aimed to evaluate the utility of ⁶⁸Ga-citrate positron emission tomography (PET)/CT in the differentiation of periprosthetic joint infection (PJI) and aseptic loosening (AL), and compare it with ^99mTc-methylene bisphosphonates (^99mTc-MDP) bone scan.

METHODS

We studied 39 patients with suspected PJI or AL. These patients underwent ⁶⁸Ga-citrate PET/CT, ^99mTc-MDP three-phase bone scan and single-photon emission CT (SPECT)/CT. PET/CT was performed at ten minutes and 60 minutes after injection, respectively. Images were evaluated by three nuclear medicine doctors based on: 1) visual analysis of the three methods based on tracer uptake model, and PET images attenuation-corrected with CT and those not attenuation-corrected with CT were analyzed, respectively; and 2) semi-quantitative analysis of PET/CT: maximum standardized uptake value (SUVmax) of lesions, SUVmax of the lesion/SUVmean of the normal bone, and SUVmax of the lesion/SUVmean of the normal muscle. The final diagnosis was based on the clinical and intraoperative findings, and histopathological and microbiological examinations.

RESULTS

Overall, 23 and 16 patients were diagnosed with PJI and AL, respectively. The sensitivity and specificity of three-phase bone scan and SPECT/CT were 100% and 62.5%, 82.6%, and 100%, respectively. Attenuation correction (AC) at 60 minutes and non-AC at 60 minutes of PET/CT had the same highest sensitivity and specificity (91.3% and 100%), and AC at 60 minutes combined with SPECT/CT could improve the diagnostic efficiency (sensitivity = 95.7%). Diagnostic efficacy of the SUVmax was low (area under the curve (AUC) of ten minutes and 60 minutes was 0.814 and 0.806, respectively), and SUVmax of the lesion/SUVmean of the normal bone at 60 minutes was the best semi-quantitative parameter (AUC = 0.969).

CONCLUSION

⁶⁸Ga-citrate showed the potential to differentiate PJI from AL, and visual analysis based on uptake pattern of tracer was reliable. The visual analysis method of AC at 60 minutes, combined with ^99mTc-MDP SPECT/CT, could improve the sensitivity from 91.3% to 95.7%. In addition, a major limitation of our study was that it had a limited sample size, and more detailed studies with a larger sample size are warranted. Cite this article: Bone Joint Res 2022;11(6):398-408.

Tibial bone and soft-tissue concentrations following combination therapy with vancomycin and meropenem - evaluated by microdialysis in a porcine model : should patients with open fractures have higher doses of antibiotics?

Aims

Prompt and sufficient broad-spectrum empirical antibiotic treatment is key to preventing infection following open tibial fractures. Succeeding co-administration, we dynamically assessed the time for which vancomycin and meropenem concentrations were above relevant epidemiological cut-off (ECOFF) minimal inhibitory concentrations (T > MIC) in tibial compartments for the bacteria most frequently encountered in open fractures. Low and high MIC targets were applied: 1 and 4 µg/ml for vancomycin, and 0.125 and 2 µg/ml for meropenem.

Methods

Eight pigs received a single dose of 1,000 mg vancomycin and 1,000 mg meropenem simultaneously over 100 minutes and 10 minutes, respectively. Microdialysis catheters were placed for sampling over eight hours in tibial cancellous bone, cortical bone, and adjacent subcutaneous adipose tissue. Venous blood samples were collected as references.

Results

Across the targeted ECOFF values, vancomycin displayed longer T > MIC in all the investigated compartments in comparison to meropenem. For both drugs, cortical bone exhibited the shortest T > MIC. For the low MIC targets and across compartments, mean T > MIC ranged between 208 and 449 minutes (46% to 100%) for vancomycin and between 189 and 406 minutes (42% to 90%) for meropenem. For the high MIC targets, mean T > MIC ranged between 30 and 446 minutes (7% to 99%) for vancomycin and between 45 and 181 minutes (10% to 40%) for meropenem.

Conclusion

The differences in the T > MIC between the low and high targets illustrate how the interpretation of these results is highly susceptible to the defined MIC target. To encompass any trauma, contamination, or individual tissue differences, a more aggressive dosing approach may be considered to achieve longer T > MIC in all the exposed tissues, and thereby lower the risk of acquiring an infection after open tibial fractures.

Cite this article: Bone Joint Res 2022;11(2):112–120.

Fracture-related infection in osteoporotic bone causes more severe infection and further delays healing

Aims

With the ageing population, fragility fractures have become one of the most common conditions. The objective of this study was to investigate whether microbiological outcomes and fracture-healing in osteoporotic bone is worse than normal bone with fracture-related infection (FRI).

Methods

A total of 120 six-month-old Sprague-Dawley (SD) rats were randomized to six groups: Sham, sham + infection (Sham-Inf), sham with infection + antibiotics (Sham-Inf-A), ovariectomized (OVX), OVX + infection (OVX-Inf), and OVX + infection + antibiotics (OVX-Inf-A). Open femoral diaphysis fractures with Kirschner wire fixation were performed. Staphylococcus aureus at 4 × 10⁴ colony-forming units (CFU)/ml was inoculated. Rats were euthanized at four and eight weeks post-surgery. Radiography, micro-CT, haematoxylin-eosin, mechanical testing, immunohistochemistry (IHC), gram staining, agar plating, crystal violet staining, and scanning electron microscopy were performed.

Results

Agar plating analysis revealed a higher bacterial load in bone (p = 0.002), and gram staining showed higher cortical bone colonization (p = 0.039) in OVX-Inf compared to Sham-Inf. OVX-Inf showed significantly increased callus area (p = 0.013), but decreased high-density bone volume (p = 0.023) compared to Sham-Inf. IHC staining showed a significantly increased expression of TNF-α in OVX-Inf compared to OVX (p = 0.049). Significantly reduced bacterial load on bone (p = 0.001), enhanced ultimate load (p = 0.001), and energy to failure were observed in Sham-Inf-A compared to Sham-Inf (p = 0.028), but not in OVX-Inf-A compared to OVX-Inf.

Conclusion

In osteoporotic bone with FRI, infection was more severe with more bone lysis and higher bacterial load, and fracture-healing was further delayed. Systemic antibiotics significantly reduced bacterial load and enhanced callus quality and strength in normal bone with FRI, but not in osteoporotic bone.

Cite this article: Bone Joint Res 2022;11(2):49–60.