Alendronate enhances osseointegration in a murine implant model

Peri-operative zoledronic acid attenuates peri-prosthetic osteolysis in a rat model of cemented knee replacement

Progressive osteolysis can occur at the cement-bone interface of joint replacements and the associated loss of fixation can lead to clinical loosening. We previously developed a rat hemiarthroplasty model that exhibited progressive loss of fixation with the development of cement-bone gaps under the tibial tray that mimicked patterns found in human arthroplasty retrievals. Here we explored the ability of a bisphosphonate (zoledronic acid, ZA) to attenuate cement-bone osteolysis and maintain implant stability. Sprague-Dawley rats (n = 59) received a poly(methylmethacrylate) cemented tibial component and were followed for up to 12 weeks. Treatment groups included peri-operative administration of ZA (ZA group), administration of ZA at 6 weeks postop (late ZA group), or vehicle (Veh group). There was a 60% reduction in the rate of cement-bone gap formation for the ZA group (0.15 mm3/week) compared to Veh group (0.38 mm3/week, p = 0.016). Late ZA prevented further progression of gap formation but did not reverse bone loss to the level achieved in the ZA group. Micromotion from five times body weight toggle loading was positively correlated with cement-bone gap volume (p = 0.009) and negatively correlated with the amount of cement in the metaphysis (p = 0.005). Reduced new bone formation and enduring nonviable bone in the epiphysis for the ZA group were found. This suggests that low bone turnover in the epiphysis may suppress the early catabolic response due to implantation, thereby maintaining better fixation in the epiphysis. This preclinical model presents compelling supporting data documenting improved maintenance of the cement-bone fixation with the use of peri-operative bisphosphonates.

Effects of antiseptic irrigation solutions on osseointegration in a cementless tibial implantation mouse model

Despite the success of standard antiseptic irrigation solutions in reducing periprosthetic joint infection (PJI) rates, there is still a need for more effective solutions. Synergistic use of povidone-iodine (PI) and hydrogen peroxide (H2O2) has shown promising results; however, the optimal solution concentration balancing bactericidal activity and osseointegration remains unknown. This study aims to evaluate the impact of these antiseptic irrigation solutions on osseointegration and the bone-implant interface strength in vivo. Forty C57BL/6 mice underwent bilateral tibial implantation surgery and were randomly allocated into three groups receiving 0.3% PI, 10% PI mixed with 3% H2O2, or saline as irrigation solutions intraoperatively. Assessments were performed on postoperative Days 1 and 28, including plain radiographs, microcomputed tomography (microCT) evaluation, histological analysis, immunohistochemistry, and biomechanical pull-out testing. No wound complications were observed. MicroCT scans revealed no differences in peri-implant trabecular bone parameters. Biomechanical pull-out testing showed no differences in the bone-implant interface strength across groups. Histological analysis indicated no differences in bone and bone marrow percentage areas among treatment groups. Immunohistochemical analysis demonstrated no differences among groups in peri-implant osteocalcin, osterix, or endomucin-positive cells. In conclusion, using either antiseptic irrigation solution showed no differences in osseointegration parameters compared to the control group, demonstrating safety and the absence of toxicity. CLINICAL RELEVANCE: Dilute 0.3% povidone-iodine and a 1:1 combination of 10% povidone-iodine mixed with 3% hydrogen peroxide can be safely used during primary and revision total joint arthroplasty without compromising osseointegration or causing wound complications.

A translational murine model of aseptic loosening with osseointegration failure

An in vivo animal model of a weight-bearing intra-articular implant is crucial to the study of implant osseointegration and aseptic loosening caused by osseointegration failure. Osseointegration, defined as a direct structural and functional attachment between living bone tissue and the surface of a load-carrying implant, is essential for implant stability and considered a prerequisite for the long-term clinical success of implants in total joint arthroplasty. Compared to large animal models, murine models offer extensive genetic tools for tracing cell differentiation and proliferation. The 18- to 22-week-old C57BL/6J background mice underwent either press-fitted or loose implantation of a titanium implant, achieving osseointegration or fibrous integration. A protocol was developed for both versions of the procedure, including a description of the relevant anatomy. Samples were subjected to microcomputed tomography and underwent biomechanical testing to access osseointegration. Lastly, samples were fixed and embedded for histological evaluation. The absence of mineralized tissue and weakened maximum pull-out force in loose implantation samples indicated that these implants were less mechanically stable compared to the control at 4 weeks postoperation. Histological analysis demonstrated extensive fibrotic tissue in the peri-implant area of loose implantation samples and excellent implant osseointegration in press-fitted samples at 4 weeks. Both mechanically stable and unstable hemiarthroplasty models with either osseous ingrowth or a robust periprosthetic fibrosis were achieved in mice. We hope that this model can help address current limitations for in vivo study of aseptic loosening and lead to necessary translational benefits.

Clinical application of platelet-rich fibrin to enhance dental implant stability: A systematic review and meta-analysis

Objective

To investigate the effect of platelet-rich fibrin application on implant stability.

Study design

Five databases, namely, PubMed, Embase, Web of Science, Wiley, and China National Knowledge Infrastructure, were searched for reports published up to November 20, 2022. Randomized controlled trials (RCT), including parallel RCTs and split-mouth RCTs, with at least 10 patients/sites were considered for inclusion.

Results

After screening based on the inclusion criteria, ten RCTs were included. Low heterogeneity was observed in study characteristics, outcome variables, and estimation scales (I² = 27.2%, P = 0.19). The qualitative and meta-analysis results showed that PRF increased the effect of implant stabilizers after implant surgery.

Conclusions

The results of the present systematic review and meta-analysis suggest that PRF can increase implant stability after implant surgery. PRF may also have a role in accelerating bone healing and tends to promote new bone formation at the implant site.

Macrophage Polarization and the Osteoimmunology of Periprosthetic Osteolysis

PURPOSE OF REVIEW

Joint replacement has revolutionized the treatment of end-stage arthritis. We highlight the key role of macrophages in the innate immune system in helping to ensure that the prosthesis-host interface remains biologically robust.

RECENT FINDINGS

Osteoimmunology is of great interest to researchers investigating the fundamental biological and material aspects of joint replacement. Constant communication between cells of the monocyte/macrophage/osteoclast lineage and the mesenchymal stem cell-osteoblast lineage determines whether a durable prosthesis-implant interface is obtained, or whether implant loosening occurs. Tissue and circulating monocytes/macrophages provide local surveillance of stimuli such as the presence of byproducts of wear and can quickly polarize to pro- and anti-inflammatory phenotypes to re-establish tissue homeostasis. When these mechanisms fail, periprosthetic osteolysis results in progressive bone loss and painful failure of mechanical fixation. Immune modulation of the periprosthetic microenvironment is a potential intervention to facilitate long-term durability of prosthetic interfaces.

Recent Advances in the Evaluation of Antimicrobial Materials for Resolution of Orthopedic Implant-Associated Infections In Vivo

While orthopedic implant-associated infections are rare, revision surgeries resulting from infections incur considerable healthcare costs and represent a substantial research area clinically, in academia, and in industry. In recent years, there have been numerous advances in the development of antimicrobial strategies for the prevention and treatment of orthopedic implant-associated infections which offer promise to improve the limitations of existing delivery systems through local and controlled release of antimicrobial agents. Prior to translation to in vivo orthopedic implant-associated infection models, the properties (e.g., degradation, antimicrobial activity, biocompatibility) of the antimicrobial materials can be evaluated in subcutaneous implant in vivo models. The antimicrobial materials are then incorporated into in vivo implant models to evaluate the efficacy of using the material to prevent or treat implant-associated infections. Recent technological advances such as 3D-printing, bacterial genomic sequencing, and real-time in vivo imaging of infection and inflammation have contributed to the development of preclinical implant-associated infection models that more effectively recapitulate the clinical presentation of infections and improve the evaluation of antimicrobial materials. This Review highlights the advantages and limitations of antimicrobial materials used in conjunction with orthopedic implants for the prevention and treatment of orthopedic implant-associated infections and discusses how these materials are evaluated in preclinical in vivo models. This analysis serves as a resource for biomaterial researchers in the selection of an appropriate orthopedic implant-associated infection preclinical model to evaluate novel antimicrobial materials.

RNA-seq Analysis of Peri-Implant Tissue Shows Differences in Immune, Notch, Wnt, and Angiogenesis Pathways in Aged Versus Young Mice

The number of total joint replacements (TJRs) in the United States is increasing annually. Cementless implants are intended to improve upon traditional cemented implants by allowing bone growth directly on the surface to improve implant longevity. One major complication of TJR is implant loosening, which is related to deficient osseointegration in cementless TJRs. Although poor osseointegration in aged patients is typically attributed to decreased basal bone mass, little is known about the molecular pathways that compromise the growth of bone onto porous titanium implants. To identify the pathways important for osseointegration that are compromised by aging, we developed an approach for transcriptomic profiling of peri-implant tissue in young and aged mice using our murine model of osseointegration. Based on previous findings of changes of bone quality associated with aging, we hypothesized that aged mice have impaired activation of bone anabolic pathways at the bone-implant interface. We found that pathways most significantly downregulated in aged mice relative to young mice are related to angiogenic, Notch, and Wnt signaling. Downregulation of these pathways is associated with markedly increased expression of inflammatory and immune genes at the bone-implant interface in aged mice. These results identify osseointegration pathways affected by aging and suggest that an increased inflammatory response in aged mice may compromise peri-implant bone healing. Targeting the Notch and Wnt pathways, promoting angiogenesis, or modulating the immune response at the peri-implant site may enhance osseointegration and improve the outcome of joint replacement in older patients. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Progressive loss of implant fixation in a preclinical rat model of cemented knee arthroplasty

Aseptic loosening of total knee arthroplasty continues to be a challenging clinical problem. The progression of the loosening process, from the initial well-fixed component, is not fully understood. In this study, loss of fixation of cemented hemiarthroplasty was explored using 9-month-old Sprague-Dawley rats with 0, 2, 6, 12, 26 week end points. Morphological and cellular changes of cement-bone fixation were determined for regions directly below the tibial tray (epiphysis) and distal to the tray (metaphysis). Loss of fixation, with a progressive increase in cement-bone gap volume was found in the epiphysis (0.162  mm³ /week), but did not progress appreciably in the metaphysis (0.007 mm³ /week). In the epiphysis, there was an early and sustained elevation of osteoclasts adjacent to the cement border and development of a fibrous tissue layer between the cement and bone. There was early formation of bone around the cement in the metaphysis, resulting in a condensed bone layer without osteoclastic bone resorption or development of a fibrous tissue layer. Implant positioning was also an important factor in the cement-bone gap formation, with greater gap formation for implants that were placed medially on the tibial articular surface. Loss of fixation in the rat model mimicked patterns found in human arthroplasty where cement-bone gaps initiate under the tibial tray, at the periphery of the implant. This preclinical model could be used to study early biological response to cemented fixation and associated contributions of mechanical instability, component alignment, and periprosthetic inflammation.

Biomimetic Composite Coatings for Activation of Titanium Implant Surfaces: Methodological Approach and In Vivo Enhanced Osseointegration

Innovative nanomaterials are required for the coatings of titanium (Ti) implants to ensure the activation of Ti surfaces for improved osseointegration, enhanced bone fracture healing and bone regeneration. This paper presents a systematic investigation of biomimetic composite (BC) coatings on Ti implant surfaces in a rat model of a diaphyseal femoral fracture. Methodological approaches of surface modification of the Ti implants via the usual joining methods (e.g., grit blasting and acid etching) and advanced physicochemical coating via a self-assembled dip-coating method were used. The biomimetic procedure used multi-substituted hydroxyapatite (ms-HAP) HAP-1.5 wt% Mg-0.2 wt% Zn-0.2 wt% Si nanoparticles (NPs), which were functionalized using collagen type 1 molecules (COL), resulting in ms-HAP/COL (core/shell) NPs that were embedded into a polylactic acid (PLA) matrix and finally covered with COL layers, obtaining the ms-HAP/COL@PLA/COL composite. To assess the osseointegration issue, first, the thickness, surface morphology and roughness of the BC coating on the Ti implants were determined using AFM and SEM. The BC-coated Ti implants and uncoated Ti implants were then used in Wistar albino rats with a diaphyseal femoral fracture, both in the absence and the presence of high-frequency pulsed electromagnetic shortwave (HF-PESW) stimulation. This study was performed using a bone marker serum concentration and histological and computer tomography (micro-CT) analysis at 2 and 8 weeks after surgical implantation. The implant osseointegration was evaluated through the bone–implant contact (BIC). The bone–implant interface was investigated using FE-SEM images and EDX spectra of the retrieved surgical implants at 8 weeks in the four animal groups. The obtained results showed significantly higher bone–implants contact and bone volume per tissue volume, as well as a greater amount of newly formed bone, in the BC-coated Ti implants than in the uncoated Ti implants. Direct bone–implant contact was also confirmed via histological examination. The results of this study confirmed that these biomimetic composite coatings on Ti implants were essential for a significant enhancement of osseointegration of BC-coated Ti implants and bone regeneration. This research provides a novel strategy for the treatment of bone fractures with possible orthopedic applications.

Is three-dimensional-printed custom-made ultra-short stem with a porous structure an acceptable reconstructive alternative in peri-knee metaphysis for the tumorous bone defect?

Background

Long-lasting reconstruction after extensive resection involving peri-knee metaphysis is a challenging problem in orthopedic oncology. Various reconstruction methods have been proposed, but they are characterized by a high complication rate. The purposes of this study were to (1) assess osseointegration at the bone implant interface and correlated incidence of aseptic loosening; (2) identify complications including infection, endoprosthesis fracture, periprosthetic fracture, leg length discrepancy, and wound healing problem in this case series; and (3) evaluate the short-term function of the patient who received this personalized reconstruction system.

Methods

Between September 2016 and June 2018, our center treated 15 patients with malignancies arising in the femur or tibia shaft using endoprosthesis with a 3D-printed custom-made stem. Osseointegration and aseptic loosening were assessed with digital tomosynthesis. Complications were recorded by reviewing the patients’ records. The function was evaluated with the 1993 version of the Musculoskeletal Tumor Society (MSTS-93) score at a median of 42 (range, 34 to 54) months after reconstruction.

Results

One patient who experienced early aseptic loosening was managed with immobilization and bisphosphonates infusion. All implants were well osseointegrated at the final follow-up examination. There are two periprosthetic fractures intraoperatively. The wire was applied to assist fixation, and the fracture healed at the latest follow-up. Two patients experienced significant leg length discrepancies. The median MSTS-93 score was 26 (range, 23 to 30).

Conclusions

A 3D-printed custom-made ultra-short stem with a porous structure provides acceptable early outcomes in patients who received peri-knee metaphyseal reconstruction. With detailed preoperative design and precise intraoperative techniques, the reasonable initial stability benefits osseointegration to osteoconductive porous titanium, and therefore ensures short- and possibly long-term durability. Personalized adaptive endoprosthesis, careful intraoperative operation, and strict follow-up management enable effective prevention and treatment of complications. The functional results in our series were acceptable thanks to reliable fixation in the bone-endoprosthesis interface and an individualized rehabilitation program. These positive results indicate this device series can be a feasible alternative for critical bone defect reconstruction. Nevertheless, longer follow-up is required to determine whether this technique is superior to other forms of fixation.