Fluorescent tetracycline labeling as an aid to debridement of necrotic bone in the treatment of chronic osteomyelitis

Polychrome Bone Fluorescence: A Valuable Diagnostic Tool for Fourth-Degree Calvarial Burns. A Case Report

Fourth-degree calvarial burns are complex in management with regard to determining bone vitality and subsequent choice of defect coverage. Distinguishing viable and nonviable bone can be challenging. Tetracycline bone fluorescence is well described and in common use in maxillofacial patients with bisphosphonate osteonecrosis and has been reported in septic orthopedic surgery specifically periprosthetic joint infection. On the basis of viable bone fluoresces, the concept of polychrome fluorescence was extrapolated as a diagnostic tool for calvarial burns. Bone fluorescence presents an efficient, non-invasive, and cost-effective diagnostic tool delineating exact necrotic margins in fourth-degree burns ensuring targeted bone-sparing debridement. This report describes the use of polychrome bone fluorescence as an intraoperative tool including a single-center case report with fourth-degree calvarial burns.

The Therapeutic Effectiveness Using Fluorescence-Guided Surgery for MRONJ

Background. Long-term application of antiresorptive and/or antiangiogenic agents may cause oral disorders, including medication-related osteonecrosis of the jaw (MRONJ), which remains an incurable disease. Surgical treatment can help alleviate infection of the jaw and block the progress of the disease, but postoperative recurrence is often caused by incomplete resection of necrotic bone during surgery. The traditional method for determining the boundary of necrotic bone resection is primarily based on the color, geology, and microcirculation-based bleeding state according to the bone tissue, which is easily affected by the surgeon’s clinical experience and can cause insufficient resection of osteonecrosis bone. Recent studies have proposed using fluorescence technology-assisted necrotic bone resection. Objective. Systematic literature review was conducted to evaluate the therapeutic effectiveness of fluorescence-guided MRONJ surgery. Design. PubMed/MedLine, Scopus, and Web of Science databases were searched from inception to February 7, 2022. Randomized controlled trial (RCT) studies were evaluated according to the Cochrane risk of bias tool ROB 2, and non-RCT (N-RCT) studies were evaluated according to the ROBINS-I tool. Results. A total of 6 articles were included in the systematic review, including 4 N-RCT studies (1 retrospective study and 3 prospective studies) and 2 RCT studies, with 240 patients and 280 MRONJ lesions. The vast majority of studies were with moderate risk of bias, and the quality of the evidence was moderate. Conclusion. Evidence of moderate strength suggests that fluorescence-assisted techniques effectively determine the bone resection boundaries in MRONJ surgery. However, whether the prognosis of patients treated with fluorescence-guided surgery is significantly better than that of traditional surgery must be proved by randomized controlled studies with larger sample sizes and higher quality.

Bone-Targeted Nanoparticle Drug Delivery System: An Emerging Strategy for Bone-Related Disease

Targeted delivery by either systemic or local targeting of therapeutics to the bone is an attractive treatment for various bone metabolism diseases such as osteoporosis, osteoarthritis, osteosarcoma, osteomyelitis, etc. To overcome the limitations of direct drug delivery, the combination of bone-targeted agents with nanotechnology has the opportunity to provide a more effective therapeutic approach, where engineered nanoparticles cause the drug to accumulate in the bone, thereby improving efficacy and minimizing side effects. Here, we summarize the current advances in systemic or local bone-targeting approaches and nanosystem applications in bone diseases, which may provide new insights into nanocarrier-delivered drugs for the targeted treatment of bone diseases. We envision that novel drug delivery carriers developed based on nanotechnology will be a potential vehicle for the treatment of currently incurable bone diseases and are expected to be translated into clinical applications.

Fluorescent tetracycline bone labeling as an intraoperative tool to debride necrotic bone during septic hip revision: a preliminary case series

A plausible cause of persistent infection after septic hip revision may be the presence of nonviable osteomyelitic bone. Since surgical excision of these necrotic fragments is often challenging, the use of fluorescent tetracycline bone labeling (FTBL) as an intraoperative tool may pose an additional assessment aid to provide a visual index of surgical debridement. Methods: We present a single-center study performed in a university hospital from January 2018 to June 2020, in which all consecutive cases of chronic hip periprosthetic joint infection (PJI) undergoing revision using FTBL were retrospectively reviewed. In all cases, the patient was under treatment with tetracyclines at the moment of the revision surgery. During the surgery, all bone failing to fluoresce was considered nonviable and thus removed and sent for both culture and histology. Results: We include three cases in which the FTBL technique was used. In all cases, the histopathological examinations of the nonfluorescent removed bone were consistent with chronic osteomyelitis. Conclusion: The intraoperative use of FTBL successfully aided the surgeon to detect the presence of nonviable bone in all the presented cases of chronic prosthetic hip infection.

Potential of growth factor incorporated mesoporous bioactive glass for in vivo bone regeneration

Mesoporous bioactive glass (MBG) has drawn much attention due to its superior surface texture, porosity and bioactive characteristics. Aim of the present study is to synthesize MBG using different surfactants, viz., hexadecyltrimethylamonium(CTAB) (M1), poly-ethylene glycol (PEG) (M2) and pluronic P123 (M3); bioactivity study; and to understand their bone regeneration efficacy in combination with insulin-like growth factors (IGF-1) in animal bone defect model. SBF study revealed the formation of calcium carbonate (CaCO₃) and hydroxyapatite (HAp) phase over 14 days. Formation of apatite layer was further confirmed by FTIR, FESEM and EDX analysis. M1 and M2 showed improved crystallinity, while M3 showed slightly decrease in crystalline peak of CaCO₃ and enhanced HAp phase. More Ca-P layer formed in M1 and M2 supported the in vivo experiments subsequently. Degree of new bone formation for all MBGs were high, i.e., M1 (80.7 ± 2.9%), M2 (74.4 ± 2.4%) and M3 (70.1 ± 1.9%) compared to BG (66.9 ± 1.8%). In vivo results indicated that the materials were non-toxic, biodegradable, biocompatible, and is suitable as bone replacement materials. Thus, we concluded that growth factor loaded MBG is a promising candidate for bone tissue engineering application.

Green Bone: Minocycline-Induced Discoloration of Bone Rarely Reported in Foot and Ankle

The tetracycline antibiotics incorporate into bone similar to bisphosphonates. Tetracycline stains bone a fluorescent yellow and minocycline, more commonly used for chronic acne, stains bone dark green. Owing to its frequent use, the occurrence of green bone discoloration due to antibiotics in the tetracycline class is well understood. Its pigmentation can be seen through delicate, thin tissue as a dark blue-gray. Histologic inspection of this bone will confirm a benign condition without evidence of bone disease. Although yellow and green discoloration has been documented frequently in association with oral surgery, it has been reported less commonly in the lower extremity. Green discoloration of bone has rarely been reported in the foot and ankle. Unlike other forms of hyperpigmentation of the skin and bone, this entity is benign when resulting from tetracycline therapy. It is always prudent to have a clinical correlate for an unusual discoloration or hyperpigmentation of any tissue when it exists. In the absence of a definitive clinical correlation, a biopsy is warranted. The following case studies provide a pictoral of green bone as it was encountered in the foot and ankle of 2 young adult females undergoing surgery.

Use of a generic violet light in the surgical management of medication-related osteonecrosis of the jaws: a technical note

PURPOSE

Fluorescence-guided surgery has been recommended for the diagnosis of bone margins in cases of mandibular osteonecrosis. In this article, we report a case in which a generic violet light was used in order to activate bone fluorescence after the administration of tetracycline derivatives, as an alternative to a specific, more expensive equipment that is commercially available for this purpose. The patient had been using alendronate for osteoporosis, resulting in medication-related osteonecrosis of the jaws.

METHODS

The treatment protocol includes preoperative administration of doxycycline and the application of a generic violet light during surgery in order to observe the fluorescence of bone in response to excitation through the light emitted by this device.

RESULTS

With an effective visualization of the limit between healthy and devitalized bone tissue, it was possible to perform the necrotic tissue removal. The lesion regressed from stage 2 to stage 0, with no clinical or radiographic evidence of necrotic bone.

CONCLUSIONS

These results suggest the feasibility of using a generic violet light source as a low-cost alternative for fluorescence-guided surgery.

3D printed β-TCP bone tissue engineering scaffolds: Effects of chemistry on in vivo biological properties in a rabbit tibia model

In this study the effects of 3D printed SiO2 and ZnO doped tricalcium phosphate (TCP) scaffolds with interconnected pores were evaluated on the in vivo bone formation and healing properties of a rabbit tibial defect model. Pure and doped TCP scaffolds were fabricated by a ceramic powder-based 3D printing technique and implanted into critical sized rabbit tibial defects for up to 4 months. In vivo bone regeneration was evaluated using chronological radiological examination, histological evaluations, SEM micrographs and fluorochrome labeling studies. Radiograph results showed that Si/Zn doped samples had slower degradation kinetics than the pure TCP samples. 3D printing of TCP scaffolds improved bone formation. The addition of dopants in the TCP scaffolds improved osteogenic capabilities when compared to the pure scaffolds. In summary, our findings indicate that addition of dopants to the TCP scaffolds enhanced bone formation and in turn leading to accelerated healing.

Influence of single and binary doping of strontium and lithium on in vivo biological properties of bioactive glass scaffolds

Effects of strontium and lithium ion doping on the biological properties of bioactive glass (BAG) porous scaffolds have been checked in vitro and in vivo. BAG scaffolds were prepared by conventional glass melting route and subsequently, scaffolds were produced by evaporation of fugitive pore formers. After thorough physico-chemical and in vitro cell characterization, scaffolds were used for pre-clinical study. Soft and hard tissue formation in a rabbit femoral defect model after 2 and 4 months, were assessed using different tools. Histological observations showed excellent osseous tissue formation in Sr and Li + Sr scaffolds and moderate bone regeneration in Li scaffolds. Fluorochrome labeling studies showed wide regions of new bone formation in Sr and Li + Sr doped samples as compared to Li doped samples. SEM revealed abundant collagenous network and minimal or no interfacial gap between bone and implant in Sr and Li + Sr doped samples compared to Li doped samples. Micro CT of Li + Sr samples showed highest degree of peripheral cancellous tissue formation on periphery and cortical tissues inside implanted samples and vascularity among four compositions. Our findings suggest that addition of Sr and/or Li alters physico-chemical properties of BAG and promotes early stage in vivo osseointegration and bone remodeling that may offer new insight in bone tissue engineering.

Enhanced bone regeneration with carbon nanotube reinforced hydroxyapatite in animal model

In order to improve the inherently poor mechanical properties of hydroxyapatite (HAp) and to increase its feasibility as load bearing implant material, in the present investigation, functionalised (HFC1 and HFC2) and non-functionalized (HC1 and HC2) multi-walled carbon nanotubes were used as reinforcing material with HAp. Significant improvement with respect to fracture toughness, flexural strength and impact strength of the composites was noticed. In vitro biological properties of HAp-carbon nanotube (CNT) biocomposites have also favored uniform and systematic apatite growth on their surface. Subsequently, in vivo osseous ingrowth at bone defect of rabbit femur was evaluated and compared using radiology, push out test, fluorochrome labeling, histology and scanning electron microscopy after 2 and 4 months respectively. The results demonstrated growth of web like soft callus from the host bone towards the implant, ensuring strong host bone interaction. Toxicological studies of the liver and kidney cells exhibited no abnormality, thereby confirming non-toxicity of the CNT in the animal body. Host-implant biomechanical strength showed high interfacial strength of the composites, indicating their high potentials to be used for bone remodeling applications.

IGF-loaded silicon and zinc doped brushite cement: physico-mechanical characterization and in vivo osteogenesis evaluation

Dopants play critical roles in controlling the physical, mechanical, degradation kinetics, and in vivo properties of calcium phosphates. The aim of the present study was to evaluate the effects of silicon (Si) and zinc (Zn) dopants on the physico-mechanical and in vivo osteogenesis properties of brushite cements (BrCs) alone and in combination with insulin like growth factor 1 (IGF-1). Addition of 0.5 wt% Si did not alter the setting time, β-TCP content, and compressive strength of BrCs significantly; however, 0.25 wt% Zn incorporation was accompanied by a significant decrease in mechanical strength from 4.78 ± 0.21 MPa for pure BrC to 3.78 ± 0.59 MPa and 3.28 ± 0.22 MPa for Zn-BrC and Si/Zn-BrC, respectively. The in vivo bone regeneration properties of doped BrCs alone and in combination with IGF-1 were assessed and compared using chronological radiography, histology, scanning electron microscopy and fluorochrome labeling at 2 and 4 months post implantation in a rabbit femoral defect model. Based on in vivo characterization focusing on osteogenesis and vasculogenesis, Si-BrC and Si/Zn-BrC showed the best performance followed by Zn-BrC and pure BrCs. Addition of IGF-1 further improved bone regeneration. Our findings confirm that addition of Si and/or Zn alters the physico-mechanical properties of BrCs and promotes the early stage in vivo osseointegration and bone remodeling properties.

Luminescence-based Imaging Approaches in the Field of Interventional Molecular Imaging

Luminescence imaging-based guidance technologies are increasingly gaining interest within surgical and radiologic disciplines. Their promise to help visualize molecular features of disease in real time and with microscopic detail is considered desirable. Integrating luminescence imaging with three-dimensional radiologic- and/or nuclear medicine-based preinterventional imaging may overcome limitations such as the limited tissue penetration of luminescence signals. At the same time, the beneficial features of luminescence imaging may be used to complement the routinely used radiologic- and nuclear medicine-based modalities. To fully exploit this integrated concept, and to relate the largely experimental luminesce-based guidance approaches into perspective with routine imaging approaches, it is essential to understand the advantages and limitations of this relatively new modality. By providing an overview of the available luminescence technologies and the various clinically evaluated exogenous luminescent tracers (fluorescent, hybrid, and theranostic tracers), this review attempts to place luminescence-based interventional molecular imaging technologies into perspective to the available radiologic- and/or nuclear medicine-based imaging technologies. At the same time, the transition from anatomic to physiologic and even molecular interventional luminescence imaging is illustrated.

Intraoperative detection of viable bone with fluorescence imaging using Visually Enhanced Lesion Scope in patients with bisphosphonate-related osteonecrosis of the jaw: clinical and pathological evaluation

There is no standard surgical protocol of bisphosphonate-related osteonecrosis of the jaws (BRONJ), because of the impossibility to visualize this feature intraoperatively. The aim of this study was to introduce how to provide preoperative labeling of the viable bone with minocycline bone fluorescence technique (MBFT) by using VELscope® and investigate histopathologically.

INTRODUCTION

The American Association of Oral and Maxillofacial Surgeons (AAOMS) and the Japanese Society of Oral and Maxillofacial Surgeons (JSOMS) now recommend a more conservative treatment strategy. There is no standard surgical protocol of bisphosphonate-related osteonecrosis of the jaws (BRONJ) because of the impossibility to visualize this feature intraoperatively. The aim of this study was to introduce a mechanism providing preoperative labeling of a viable bone using minocycline bone fluorescence technique (MBFT) with VELscope® and to histopathologically investigate.

METHODS

This report describes a surgical technique used in six patients with BRONJ who underwent jawbone resection under minocycline bone fluorescence imaging using VELscope®. Subsequently, we investigated and compared the clinical findings using VELscope® and histopathological findings.

RESULTS

Histopathological examinations showed that the non-fluorescent moiety was consistent with the BRONJ lesions.

CONCLUSIONS

The surgical treatments that were exactly performed using MBFT with VELscope® offered successful management of BRONJ. This bone fluorescence helped to define the margins of resection, thus improving surgical therapy for extended osteonecrosis.

Comparison of tissue-engineered bone from different stem cell sources for maxillary sinus floor augmentation: a study in a canine model

PURPOSE

To compare the potential of tissue-engineered bone derived from different stem cell sources for canine maxillary sinus augmentation.

MATERIALS AND METHODS

Bilateral maxillary sinus floor augmentations were performed in 6 beagles and were randomly repaired with 3 graft types: Bio-Oss granules alone (n = 4; group A), a complex of osteoblasts derived from bone marrow mesenchymal stem cells (BMMSCs) and Bio-Oss (n = 4; group B), and a complex of osteoblasts derived from periodontal ligament stem cells (PDLSCs) and Bio-Oss (n = 4; group C). After 12 weeks, fluorescent labeling, maxillofacial computed tomography, scanning electron microscopy, and histologic and histomorphometric analyses were used to evaluate new bone deposition, mineralization, and remodeling in the augmented area.

RESULTS

The osteogenic capacity was greater in groups B and C than in group A. The level tended to be higher in group C than in group B; however, the difference was not statistically significant.

CONCLUSIONS

Seeding of PDLSCs or BMMSCs onto Bio-Oss can promote bone formation and mineralization and maintain the maximum volume of the augmented maxillary sinus. These tissue-engineered bone complexes might be a good option for augmentation of the maxillary sinus in edentulous patients.

Ex vivo human trabecular bone model for biocompatibility evaluation of calcium phosphate composites modified with spray dried biodegradable microspheres

Our aim was to study the suitability of the ex-vivo human trabecular bone bioreactor ZetOS to test the biocompatibility of calcium phosphate bone cement composites modified with spray dried, drug loaded microspheres. We hypothesized, that this bone bioreactor could be a promising alternative to in vivo assessment of biocompatibility in living human bone over a defined time period. Composites consisting of tetracycline loaded poly(lactic-co-glycolic acid) microspheres and calcium phosphate bone cement, were inserted into in vitro cultured human femora head trabecular bone and incubated over 30 days at 37°C in the incubation system. Different biocompatibility parameters, such as lactate dehydrogenase activity, alkaline phosphatase release and the expression of relevant cytokines, IL-1β, IL-6, and TNF-α, were measured in the incubation medium. No significant differences in alkaline phosphatase, osteocalcin, and lactate dehydrogenase activity were measured compared to control samples. Tetracycline was released from the microspheres, delivered and incorporated into newly formed bone. In this study we demonstrated that ex vivo biocompatibility testing using human trabecular bone in a bioreactor is a potential alternative to animal experiments since bone metabolism is still maintained in a physiological environment ex vivo.

Reconstruction of osteomyelitis defects

Reconstruction of large skeletal defects secondary to osteomyelitis remains a challenging problem. Osteomyelitis can result from a variety of etiologies; most often, it is a consequence of trauma to a long bone. Despite advances in antibiotic therapy, treatment of chronic osteomyelitis requires adequate surgical debridement, which can often lead to large soft tissue and bone loss. Free vascularized bone can be used to reconstruct large skeletal defects greater than 6 cm or bone defects of smaller size that failed to heal with nonvascularized bone grafting. The length, cortical strength, and anatomic configuration of the free vascular fibular graft make it an ideal bone graft to bridge extremity defects, and it can be transferred with skin, fascia, and muscle to fill soft tissue defects in the recipient site.

Tetracycline labeling as a measure of humeral head viability after 3- or 4-part proximal humerus fracture

HYPOTHESIS

Specifically located humeral head biopsies from three-part proximal humerus fractures taken at the time of hemiarthroplasty will show greater tetracycline labeling under fluorescent microscopy than those biopsies taken from four-part fractures. Additionally, biopsies from younger patients would show greater fluorescence than older patients.

MATERIAL AND METHODS

Nineteen consecutive adult patients (range 43-83 years) underwent hemiarthroplasty as definitive treatment for 20 displaced three- and four-part proximal humerus fractures after having received 500 mg of tetracycline hydrochloride orally every six hours for the immediate five preoperative days. Humeral head biopsies were taken from four pre-determined locations intraoperatively. The biopsies were prepared and analyzed with fluorescent microscopy.

RESULTS

All specimens in each biopsy location demonstrated fluorescence. There was no difference between the mean rank gray values for the four biopsy locations (p = 0.78 with the Friedman test). There was no difference between the mean rank gray values for the four biopsy locations when analyzed according to three-part vs four-part fracture (p > 0.05 with the Mann-Whitney test). There was an inverse relationship between age and fluorescence for the anterosuperior biopsy location (p = 0.033 with Spearman correlation).

DISCUSSION

Vascular supply is preserved in displaced three- and four-part proximal humerus fractures. With intact vascularity to the humeral head, head-preserving techniques utilizing stable, site-specific fixation and minimal dissection should be considered in the treatment of displaced three- and four-part proximal humerus fractures.

CONCLUSION

Vascular supply is preserved in displaced three- and four-part proximal humerus fractures, especially in younger patients in the anterosuperior aspect of the humeral head.

LEVEL OF EVIDENCE

Basic Science Study.

Fluorescence-guided bone resection in bisphosphonate-associated osteonecrosis of the jaws

PURPOSE

To date, the therapy of bisphosphonate-associated osteonecrosis of the jaws (BONJ) has been hampered by the lack of imaging modalities that enable the extent of necrosis to be visualized. This study aims to demonstrate the feasibility of tetracycline fluorescence guided bone resection in the surgical management of BONJ.

PATIENTS AND METHODS

Following a 10-day preoperative administration of doxycycline in patients suffering from BONJ, sufficient doxycycline is incorporated into viable bone to be visualized with a certified medical lamp emitting exciting light at 400 to 460 nm.

RESULTS

Viable and necrotic bone can be discriminated intraoperatively in a routine and reproducible manner by doxycycline bone fluorescence.

CONCLUSION

In the therapy of BONJ, conservative concepts are to be favored. The fact that necrotic bone can now be selectively resected signifies an improvement of the conservative surgical therapy of BONJ.

Feasibility of a tetracycline-binding method for detecting synovial fluid basic calcium phosphate crystals

OBJECTIVE

Basic calcium phosphate (BCP) crystals are common components of osteoarthritis (OA) synovial fluid. Progress in understanding the role of these bioactive particles in clinical OA has been hampered by difficulties in their identification. Tetracyclines stain calcium phosphate mineral in bone. The aim of this study was to investigate whether tetracycline staining might be an additional or alternative method for identifying BCP crystals in synovial fluid.

METHODS

A drop of oxytetracycline was mixed with a drop of fluid containing synthetic or native BCP, calcium pyrophosphate dihydrate (CPPD), or monosodium urate (MSU) crystals and placed on a microscope slide. Stained and unstained crystals were examined by light microscopy, with and without a portable broad-spectrum ultraviolet (UV) pen light. A small set of characterized synovial fluid samples were compared by staining with alizarin red S and oxytetracycline. Synthetic BCP crystals in synovial fluid were quantified fluorimetrically using oxytetracycline.

RESULTS

After oxytetracycline staining, synthetic and native BCP crystals appeared as fluorescent amorphous aggregates under UV light. Oxytetracycline did not stain CPPD or MSU crystals or other particulates. Oxytetracycline staining had fewer false-positive test results than did alizarin red S staining and could provide estimates of the quantities of synthetic BCP crystals in synovial fluid.

CONCLUSION

With further validation, oxytetracycline staining may prove to be a useful adjunct or alternative to currently available methods for identifying BCP crystals in synovial fluid.