Peripheral quantitative computed tomography in evaluation of bioactive glass incorporation with bone

Construction of multileveled and oriented micro/nano channels in Mg doped hydroxyapitite bioceramics and their effect on mimicking mechanical property of cortical bone and biological performance of cancellous bone

Drawing on the structure and components of natural bone, this study developed Mg-doped hydroxyapatite (Mg-HA) bioceramics, characterized by multileveled and oriented micro/nano channels. These channels play a critical role in ensuring both mechanical and biological properties, making bioceramics suitable for various bone defects, particularly those bearing loads. Bioceramics feature uniformly distributed nanogrooves along the microchannels. The compressive strength or fracture toughness of the Mg-HA bioceramics with micro/nano channels formed by single carbon nanotube/carbon fiber (CNT/CF) (Mg-HA(05-CNT/CF)) are comparable to those of cortical bone, attributed to a combination of strengthened compact walls and microchannels, along with a toughening mechanism involving crack pinning and deflection at nanogroove intersections. The introduction of uniform nanogrooves also enhanced the porosity by 35.4 %, while maintaining high permeability owing to the capillary action in the oriented channels. This leads to superior degradation properties, protein adsorption, and in vivo osteogenesis compared with bioceramics with only microchannels. Mg-HA(05-CNT/CF) exhibited not only high strength and toughness comparable to cortical bone, but also permeability similar to cancellous bone, enhanced cell activity, and excellent osteogenic properties. This study presents a novel approach to address the global challenge of applying HA-based bioceramics to load-bearing bone defects, potentially revolutionizing their application in tissue engineering.

Outcomes of Hindfoot Arthrodesis Supplemented With Bioactive Glass and Bone Marrow Aspirate: A Retrospective Radiographic Study

Foot and ankle surgeons continue to explore bone graft alternatives that will be comparable to the reference standard of autologous bone. The purpose of the present study was to consider the outcomes of hindfoot arthrodesis supplemented with bioactive glass in patients at risk of delayed union and nonunion. We performed a retrospective radiographic review of 29 consecutive patients (48 joints) who had undergone arthrodesis of ≥1 joint of the hindfoot (ankle, subtalar, talonavicular, calcaneocuboid). All patients included in the present study had a minimum of 1 documented risk factor for osseous nonunion (history of previous nonunion, trauma, smoking, diabetes, Charcot arthropathy, obesity, age >65 years at surgery). The patients were followed up for a minimum of 24 weeks or until radiographic healing had been achieved. We found 12 (25.0%) nonunions across all 48 joints supplemented with bioactive glass. We found 4 (16.7%) nonunions in the subtalar joint, 1 (11.1%) in the calcaneocuboid joint, and 1 (11.1%) in the talonavicular joint. We found that hindfoot arthrodesis procedures supplemented with bioactive glass resulted in an incidence of union comparable to that with autograft and other bone graft substitutes.

Effect of a new bioactive fibrous glassy scaffold on bone repair

Researchers have investigated several therapeutic approaches to treat non-union fractures. Among these, bioactive glasses and glass ceramics have been widely used as grafts. This class of biomaterial has the ability to integrate with living bone. Nevertheless, bioglass and bioactive materials have been used mainly as powder and blocks, compromising the filling of irregular bone defects. Considering this matter, our research group has developed a new bioactive glass composition that can originate malleable fibers, which can offer a more suitable material to be used as bone graft substitutes. Thus, the aim of this study was to assess the morphological structure (via scanning electron microscope) of these fibers upon incubation in phosphate buffered saline (PBS) after 1, 7 and 14 days and, also, evaluate the in vivo tissue response to the new biomaterial using implantation in rat tibial defects. The histopathological, immunohistochemistry and biomechanical analyzes after 15, 30 and 60 days of implantation were performed to investigate the effects of the material on bone repair. The PBS incubation indicated that the fibers of the glassy scaffold degraded over time. The histological analysis revealed a progressive degradation of the material with increasing implantation time and also its substitution by granulation tissue and woven bone. Histomorphometry showed a higher amount of newly formed bone area in the control group (CG) compared to the biomaterial group (BG) 15 days post-surgery. After 30 and 60 days, CG and BG showed a similar amount of newly formed bone. The novel biomaterial enhanced the expression of RUNX-2 and RANK-L, and also improved the mechanical properties of the tibial callus at day 15 after surgery. These results indicated a promising use of the new biomaterial for bone engineering. However, further long-term studies should be carried out to provide additional information concerning the material degradation in the later stages and the bone regeneration induced by the fibrous material.

Posterolateral Spondylodesis Using Bioactive Glass S53P4 and Autogenous Bone in Instrumented Unstable Lumbar Spine Burst Fractures

Background and Aims

A prospective long-term follow-up study of bioactive glass (BAG)-S53P4 and autogenous bone (AB) used as bone graft substitutes for posterolateral spondylodesis in treatment of unstable lumbar spine burst fractures during 1996–1998 was conducted.

Material and Methods

The lumbar fractures were fixed using posterior USS instrumentation. BAG was implanted on the left side of the fusion-bed and AB on the right side. The operative outcome was evaluated on X-rays and CT scans, and a clinical examination was also performed.

Results

The Oswestry score was excellent, and the mean pain score 1. The mean compression rate of the injured vertebral body was 25%. A solid bony fusion was seen on CT scans on the AB side in all patients and on the BAG side in five patients, and a partial fusion in five patients, resulting in a total fusion-rate of 71% of all fused segments in the BAG group.

Conclusions

Our long-term results show that BAG-S54P4 bone graft material is safe to be used as a bone graft extender in spine surgery.

Evaluation of optical density of bone defects filled with calcium phosphate cement and bioactive glass in rats

Purpose: To evaluate new bone formation, by the analysis of optical density, in rat femoral defects filled with calcium phosphate cement (CPC) and bioactive glass (BG). Methods: Twenty-one rats were divided into three groups, Group I (CPC), Group II (BG), and Group III (control), and assessed after 7, 15, and 30 days. Three bone cavities were made in the left femur and filled with CPC, BG, and no material (control). Digital images were obtained and the results were subjected to statistical analysis of variance (ANOVA), complemented by the Friedman and Kruskal-Wallis nonparametric tests, with a significance level of 5%. Results: Regarding optical density, Group I showed statistical values significantly higher than Group III and also higher, although not statistically significant, than Group II, in all observation periods. When Groups II and III were compared, Group II showed higher optical density values, without statistically significant differences, in all periods. Conclusion: The biomaterials analyzed showed higher optical density in relation to the control group in all observation periods, calcium phosphate cement being the best option in the repair of bone defects, but without statistically significant differences in relation to bioactive glass.

Bioceramic inlays do not improve mechanical incorporation of grit-blasted titanium stems in the proximal sheep femur

The aim of the present study was to determine, if bioactive glass (BG) surface inlays improve osseointegration of titanium implants in the proximal femur of adult sheep. In simulation of uncemented primary stems (nine animals), only the proximal part of the implants was grit-blasted and three surface slots of the grit-blasted region were filled with sintered BG microspheres. Primary stems were implanted using press-fit technique. In revision stem simulation (eight animals), grit-blasting was extended over the whole implant and seven perforating holes of the stem were filled by sintered BG granules. Revision stems were implanted with a mixture of autogenous bone graft and BG granules. Comparison with solid partially or fully grit-blasted control stems implanted in the contralateral femurs was performed in the primary and revision stem experiments at 12 and 25 weeks, respectively. Implant incorporation was evaluated by torsional failure testing and histomorphometry. Only one-third of the primary stems anchored mechanically to bone. The revision stems incorporated better and the BG inlays of the revision stems showed ingrowth of new bone. However, there were no significant differences in the torsional failure loads between the stems with BG inlays and the control stems. In conclusion, surface BG inlays gave no measurable advantage in mechanical incorporation of grit-blasted titanium implants. Overall, the proximal sheep femur, characterized by minimal amount of cancellous bone and the presence of adipocytic bone marrow, seemed to present compromised bone healing conditions.

Radio-opaque bioactive glass markers for radiostereometric analysis

The objective of the study was to test the hypothesis that resorbable radio-opaque bioactive glass markers can be used in radiostereometric analysis (RSA). Cones made from (1) bioactive glass 1-06 with 2.5 wt.% BaSO(4), (2) glass 1-06 with 10 wt.% BaSO(4), (3) glass 1-06 without any additives and (4) nearly inert glass were created. The in vitro surface reactivity, as a surrogate of bioactivity, was analyzed using a simulated body fluid (SBF) immersion test. The in vivo performance was evaluated in the rat femur using biomechanical testing as well as histological and microcomputed tomography analysis of marker incorporation into bone. A phantom model RSA study using a porcine radius with a soft tissue envelope was carried out to determine the accuracy and precision of spherical markers for the measurement of fracture micromotion. SBF immersion studies and bone implantation studies showed that the addition of BaSO(4) slightly reduced surface reactivity in vitro and the bone-bonding properties of the bioactive glass in vivo. In the simulated RSA study with the selected resorbable marker composition (bioactive glass with 10 wt.% BaSO(4)), the accuracy of translation and rotation measurements in the longitudinal axis was +/-51 microm and +/-0.87 degrees , respectively. The precision of translation and rotation measurements in the longitudinal axis were 9 microm and 0.18 degrees , respectively. Bioactive glass markers with BaSO(4) additive appear to have adequate bone-bonding properties for marker stability and sufficient radio-opacity for RSA, but further preclinical comparison studies with tantalum markers are necessary.

Bioactive glass granules as extender of autogenous bone grafting in cementless intercalary implant of the canine femur

BACKGROUND AND AIMS

Ceramic bone graft substitutes have a potential to be used as replacement of allogeneic bone grafting and, under optimal distribution of particle size, they may even provide mechanical support. The current study examined the efficacy of bioactive glass granules as an extender of autogenous bone grafting in a segmental bone replacement model of the canine femur.

MATERIAL AND METHOD

A 16 mm long segment of the femur shaft was bilaterally replaced with an intercalary titanium implant in eight animals. The implant had cementless grooved proximal and distal stems. In one leg, the peri-implant space was packed with composite graft consisting of a mixture of bioactive glass granules and autogenous bone graft in proportion of 50:50. In the opposite leg, the peri-implant space was treated with autogenous bone graft alone. After surgery, unlimited functional loading was allowed. The outcome was evaluated at three months.

RESULTS

Eight out of sixteen autografted implants and seven out of sixteen composite-grafted implants were radiographically incorporated and clinically stable at three months. In the paired comparison, the proximal components of composite-grafted implants showed lower maximum load under torsional testing (p = 0.068), less new bone in the longitudinal grooves of the stems (p = 0.036) and lower affinity of new bone to implant surface (p = 0.046). The distal components of the two sides showed a similar trend for less new bone in the grooves and lower bone affinity of new bone in the distal composite-grafted components.

CONCLUSIONS

The current study suggests that supplementation of periprosthetic bone graft with bioactive ceramic particles may not help to promote healing of cementless implants under high dynamic loading conditions.

Effect of zoledronic acid on incorporation of a bioceramic bone graft substitute

Many osteoporotic fracture patients are candidates for concurrent treatment with bisphosphonates and bioceramic bone graft substitutes. Osteopromotive silica-based bioactive glasses are known to induce accelerated local bone turnover and adjunct antiresorptive agents, such as zoledronic acid, may affect the process. The current study examined the effect of adjunct zoledronic acid therapy on bioactive glass incorporation. In Harlan Sprague-Dawley rats (n = 80), a standardized region of the proximal tibia was subjected to ablation of local bone marrow and filled with bioactive glass (BG) microspheres. Experimental animals received zoledronic acid (1.5 mug/kg, s.c., once a week, started 1 week before surgery) or doxycycline (a metalloproteinase inhibitor) (33 mg/kg, daily gavage) as a control agent. BG incorporation and geometric bone properties were followed by sequential pQCT imaging. The final outcome at 8 weeks was analyzed by digital radiography, histomorphometry, BEI-SEM, EDXA and muCT. The mRNA levels of markers for bone resorption (cathepsin K, TRACP, MMP-9, MMP-13) and synthesis (type I, II, III collagens, osteocalcin, osteonectin, osteopontin) were measured for determination of local bone turnover. Bones filled with BG microspheres produced 2.5-fold more intramedullary new bone than controls with bone marrow ablation only, but the BG filling delayed the recovery of pQCT strength strain index (SSI) of the bones. Adjunct therapy with zoledronic acid enhanced new bone formation on BG microspheres and particularly improved the SSI values of the BG-filled bones (P < 0.05). The zoledronic acid therapy alone (without BG filling) produced the highest amount of intramedullary new bone (6-fold more than in unfilled controls, P < 0.001) but did not show a similar benefit in SSI. The analyses of mRNA expression confirmed high local bone turnover in all bones with BG filling. At the 9th week of zoledronic acid treatment, bones with and without BG filling showed increased mRNA levels of bone resorption markers and decreased mRNA levels of markers for synthesis, indicating that a corrective resorption process was already in progress in response to massive accumulation of medullary new bone at earlier stages of the therapy. Adjunct antiresorptive therapy seems to be beneficial for incorporation of bioactive glass microspheres and does not block local natural remodeling processes. In the current model, the therapy even resulted in favorable remodeling of the tubular bone structure.