Dual-functional thermosensitive hydrogel for reducing infection and enhancing bone regeneration in infected bone defects

The contamination of bone defects is a serious therapeutic problem. The treatment of infected bone defects involves rigorous infection control followed by bone reconstruction. Considering these two processes, the development of biomaterials possessing antibacterial and osteogenic properties offers a promising approach for the treatment of infected bone defects. In this study, a dual-functional, thermosensitive, and injectable hydrogel composed of chitosan (CS), quaternized CS (QCS), and nano-hydroxyapatite (nHA) was designed, and the ratio of CS to QCS in the hydrogel was optimized to enhance the antibacterial efficacy of CS while reducing the cytotoxicity of QCS. In vitro studies demonstrated that the hydrogel with an 85 %:15 % ratio of CS to QCS exhibited excellent biocompatibility and antibacterial properties while also possessing suitable mechanical characteristics and degradability. The incorporation of nHA into the hydrogel enhanced MC3T3-E1 proliferation and osteogenic differentiation. Moreover, this hydrogel demonstrated superior in vivo therapeutic effectiveness in a rabbit model of infected bone defect. In summary, this study provides a promising material design and a comprehensive one-step treatment strategy for infected bone defects.

The polymicrobial infection affects the infection recurrence rate (not failure) in treating femoral and tibial bone defects with the Masquelet technique-a comparative retrospective analysis of 54 patients with mono- and polymicrobial infections

INTRODUCTION

This study evaluated whether polymicrobial infection affects reoperation rates due to infection recurrence and treatment failure with the Masquelet technique in infected posttraumatic segmental bone defects of the femur and tibia.

METHODS

 We retrospectively analyzed patients treated between 2012 and 2021 in two trauma referral centers. We evaluated demographic data, injury, treatment, infection recurrence, failures, and bone healing rates according to whether the infection was mono- or polymicrobial. After uni-bivariate analysis between patients with polymicrobial and monomicrobial infection, we identified the variables associated with infection recurrence and failure through multivariate analysis.

RESULTS

 We analyzed 54 patients, 30 (55.55%) with tibial and 24 (44.44%) femoral segmental bone defects, with a mean follow-up of 41.7 ± 15.0 months. Forty-four (81.48%) presented monomicrobial, and 10 (18.51%) polymicrobial infections. Comparatively, the need for soft tissue reconstruction and the infection recurrence rate was significantly higher in patients with polymicrobial infections. There was no significant difference in the failure rate (20 vs. 6.81% p = 0.23). Multivariable logistic regression analysis identified the polymicrobial infection as the only independent variable associated with infection recurrence (Odds Ratio = 11.07; p = 0.0017).

CONCLUSION

 Our analysis suggests that polymicrobial infection is associated with a higher risk of infection recurrence in treating the femur and tibia segmental bone defects with the Masquelet technique. This information can help surgeons to inform patients about this and give them a realistic expectation of the outcome and the possibility of reoperation.

An injectable carboxymethyl chitosan hydrogel scaffold formed via coordination bond for antibacterial and osteogenesis in osteomyelitis

The intricate, hostile, and diverse nature of osteomyelitis (OM) poses a challenge for complete bacterial eradication and osteogenesis promotion via conventional treatment. Recently, functional hydrogels exhibiting antibacterial and osteogenic properties emerge as a promising avenue for OM wound healing in clinical practice. However, the preparation procedures and associated costs on cytokine and cell therapies for certain functional hydrogels can be complex and prohibitively expensive. In our research, a hybrid hydrogel dressing has been formulated utilizing carboxymethyl chitosan (CMCS) as the base material, and designed with inherent antibacterial, adhesion, proliferation, and differentiation characteristics, showing promise as a candidate for eradicating infection and promoting bone regeneration. The hybrid hydrogel is composed of interconnected networks of Fe3+-induced self-assembled CMCS and the antibacterial drug ciprofloxacin (CIP), resulting in excellent injectability and moldability. Notably, the CMCS/Fe3+/CIP hybrid hydrogel is capable of regulating antibacterial responses and stimulating osteogenesis in infected microenvironments without additional additives. This injectable antibacterial and osteogenic-promoting hydrogel establish a high-potential platform for low-cost, safe and effective treatment of OM by expediting the initial stages of infected bone wound repair.

Comparison of antibiotic-impregnated bone cement coverage versus vacuum sealing drainage in semi-open bone grafting using for tibial fracture with infected bone and soft tissue defect: a retrospective analysis

OBJECTIVE

To compare antibiotic-impregnated bone cement coverage (bone cement surface technique; BCS-T) versus vacuum sealing drainage (VSD) for tibial fracture with infected bone and soft tissue defect.

METHOD

This retrospective analysis compared the clinical outcomes in patients undergoing BCS-T (n = 16) versus VSD (n = 15) for tibial fracture with infected bone and soft tissue defect at the Third Hospital of Hebei Medical University from March 2014 to August 2019. For BCS-T group, osseous cavity was filled with autograft bone graft after debridement, and then the wound was covered with a 3-mm layer of bone cement impregnated with vancomycin and gentamycin. The dressing was changed every day in the first week, and every 2 ~ 3 days in the second week. For VSD group, a negative pressure of -150 ~ -350 mmHg was maintained, and the dressing was changed every 5-7 days. All patients received antibiotics treatment based on bacterial culture results for 2 weeks.

RESULTS

The 2 groups did not differ in age, sex and key baseline characteristics, including type of Gustilo-Anderson classification, size of the bone and soft tissue defect, the percentage of primary debridement, bone transport, and the time from injury to bone grafting. The median follow-up was 18.9 months (range:12-40). The time to complete coverage of bone graft by granulation tissue was 21.2 (15.0-44.0) and 20.3 (15.0-24.0) days in the BCS-T and VSD groups, respectively (p = 0.412). The 2 groups also did not differ in wound healing time (3.3 (1.5-5.5) versus 3.2(1.5-6.5) months; p = 0.229) and bone defect healing time (5.4(3.0-9.6) versus 5.9(3.2-11.5) months; p = 0.402). However, the cost of covering material was significantly reduced in the BCS-T group (2071 ± 134 versus 5542 ± 905 yuan; p = 0.026). Paley functional classification at 12 months did not differ between the 2 groups (excellent in 87.5% versus 93.3% in the 2 groups; p = 0.306).

CONCLUSION

BCS-T could achieve clinical outcomes similar to VSD in patients receiving bone graft for tibial fracture with infected bone and soft tissue defect, but material cost was significantly reduced. Randomized controlled trials are needed to verify our finding.

Copper-containing chitosan-based hydrogels enabled 3D-printed scaffolds to accelerate bone repair and eliminate MRSA-related infection

Bone defect combined with drug-resistant bacteria-related infection is a thorny challenge in clinic. Herein, 3D-printed polyhydroxyalkanoates/β-tricalcium phosphate (PHA/β-TCP, PT) scaffolds were prepared by fused deposition modeling. Then copper-containing carboxymethyl chitosan/alginate (CA/Cu) hydrogels were integrated with the scaffolds via a facile and low-cost chemical crosslinking method. The resultant PT/CA/Cu scaffolds could not only promote proliferation but also osteogenic differentiation of preosteoblasts in vitro. Moreover, PT/CA/Cu scaffolds exhibited a strong antibacterial activity towards a broad-spectrum of bacteria including methicillin-resistant Staphylococcus aureus (MRSA) through inducing the intercellular generation of reactive oxygen species. In vivo experiments further demonstrated that PT/CA/Cu scaffolds significantly accelerated bone repair of cranial defects and efficiently eliminated MRSA-related infection, showing potential for application in infected bone defect therapy.

Current Advances and Applications of Tantalum Element in Infected Bone Defects

Infected bone defects (IBDs) cause significant economic and psychological burdens, posing a huge challenge to clinical orthopedic surgeons. Traditional approaches for managing IBDs possess inevitable shortcomings; therefore, it is necessary to develop new functionalized scaffolds. Tantalum (Ta) has been widely used in load-bearing orthopedic implants due to its good biocompatibility and corrosion resistance. However, undecorated Ta could only structurally repair common bone defects, which failed to meet the clinical needs of bacteriostasis for IBDs. Researchers have made great efforts to functionalize Ta scaffolds to enhance their antibacterial activity through various methods, including surface coating, alloying, and micro- and nanostructure modifications. Additionally, several studies have successfully utilized Ta to modify orthopedic scaffolds for enhanced antibacterial function. These studies remarkably extended the application range of Ta. Therefore, this review systematically outlines the advances in the fundamental and clinical application of Ta in the treatment of IBDs, focusing on the antibacterial properties of Ta, its functionalization for bacteriostasis, and its applications in the modification of orthopedic scaffolds. This study provides researchers with an overview of the application of Ta in the treatment of IBDs.

Masquelet technique in post-traumatic infected femoral and tibial segmental bone defects. Union and reoperation rates with high proportions (up to 64%) of allograft in the second stage

Introduction The aim of this study was to describe union, reoperation and failure rates after using the induced membrane (IM) technique with ≥50% allograft over autograft to treat infected femoral and tibial segmental bone defects (SBD). Materials and methods We retrospectively analyzed patients with femoral and tibial SBD treated in our center between 2012 and 2019 using ≥50% allograft over autograft during the second stage of the Masquelet technique. We analyzed the affected bone, defect size, osteosynthesis technique used, time elapsed between the first and second stage of the technique, graft proportions, union time, reoperations, and non-union rates. Results We included 21 patients (61.90% men) with a median age of 41 (range 18-68) years. The tibia was affected in 61.90% (n:13) and the femur in 38.09% (n:8) of the cases. SBD length was 4.5 (range 3.5-14) cm. The median interval between both stages of the technique was 10 (range 6-28) weeks. The proportion of allograft used was 50 % in 10 patients, 51 to 55% in 5 patients, 56 to 59% in 4 patients, and 60 to 64% in 2. The union rate was 95.23% over a median time of 7 (range 6-12) months. There were 3 (14.28%) reoperations: 2 for relapse of infection and 1 for mechanical instability. There was one failure (4.76%). One patient presented non-union and nail break. The median follow-up after the second stage of the technique was 26 (range 13-54) months. Conclusion The use of the induced membrane technique and a high proportion of allograft (up to 64%) achieved similar union and failure rates than those reported for similar series that relied on lower allograft proportions.

Dual-functional 3D-printed composite scaffold for inhibiting bacterial infection and promoting bone regeneration in infected bone defect models

Infection is one of the pivotal causes of nonunion in large bone defect after trauma or tumor resection. Three-dimensional (3D) composite scaffold with multifunctional-therapeutic properties offer many advantages over allogenic or xenogenic bone grafting for the restoration of challenging infected bone defects. In the previous study, we demonstrated that quaternized chitosan (HACC)-grafted polylactide-co-glycolide (PLGA)/hydroxyapatite (HA) scaffold (PLGA/HA/HACC) via 3D-printing technique exhibited significantly improved antimicrobial and osteoconductive property in vitro, together with good biocompatibility in vivo. Hence, the present study further investigated whether such an innovative bone substitute could effectively inhibit the bacterial biofilm formation and promote bone regeneration in vivo. To evaluate the bone repairing effects of the 3D-printed scaffolds on infected cortical and cancellous bone defects scenarios, eighty female Sprague Dawley rats and thirty-six female New Zealand white rabbits were used to establish infected femoral shaft defect and condyle defect model, respectively. X-ray, micro-CT, microbiological and histopathological analyses were used to assess the anti-infection and bone repairing potential of the dual-functional porous scaffolds. We observed that HACC-grafted PLGA/HA scaffolds exhibited significantly enhanced anti-infection and bone regeneration capability in different infected bone defect models. In addition, the degradation rate of the scaffolds appeared to be closely related to the progress of infection, influencing the bone repairing potential of the scaffolds in infected bone defects models. In general, this investigation is of great significance as it demonstrates promising applications of the 3D-printed dual-functional PLGA/HA/HACC scaffold for repairing different types of bone defect under infection.

STATEMENT OF SIGNIFICANCE

Currently, it is clinically urgent to exploit bone substitutes with potential of bacterial inhibition and bone regeneration. However, bone scaffolds with relatively low risks of bacterial resistance and tissue toxicity used for combating infected bone defects remain to be developed. We have reported that quaternized chitosan (HACC)-grafted 3D-printed PLGA/HA composite scaffold had enhanced in vitro antimicrobial and osteoconductive property, and well cytocompatibility in our published study. This continuing study further confirmed that HACC-grafted PLGA/HA scaffolds exhibited significantly enhanced anti-infection and bone regeneration efficacy in both cortical bone defect in rat and cancellous bone defect in rabbit under infection. Meanwhile, we also found that the degradation rate of the scaffolds seemed to be closely related to the progress of infection, influencing the bone repairing potential of the scaffolds in infected bone defects models. In conclusion, this study provides significant opportunities to develop a 3D-printed bone scaffold with dual functions used for infected bone defects in future plastic and orthopaedic surgery.

Effect of gelatin sponge with colloid silver on bone healing in infected cranial defects

Oral infectious diseases may lead to bone loss, which makes it difficult to achieve satisfactory restoration. The rise of multidrug resistant bacteria has put forward severe challenges to the use of antibiotics. Silver (Ag) has long been known as a strong antibacterial agent. In clinic, gelatin sponge with colloid silver is used to reduce tooth extraction complication. To investigate how this material affect infected bone defects, methicillin-resistant Staphylococcus aureus (MRSA) infected 3-mm-diameter cranial defects were created in adult female Sprague-Dawley rats. One week after infection, the defects were debrided of all nonviable tissue and then implanted with gelatin sponge with colloid silver (gelatin/Ag group) or gelatin alone (gelatin group). At 2 and 3days after debridement, significantly lower mRNA expression levels of IL-6 and TNF-α and lower plate colony count value were detected in gelatin/Ag group than control. Micro-CT analysis showed a significant increase of newly formed bone volume fraction (BV/TV) in gelatin/Ag treated defects. The HE stained cranium sections also showed a faster rate of defect closure in gelatin/Ag group than control. These findings demonstrated that gelatin sponge with colloid silver can effectively reduce the infection caused by MRSA in cranial defects and accelerate bone healing process.