Locally administered low-dose alendronate increases bone mineral density during distraction osteogenesis in a rabbit model

Evaluation of Effects of Systemic Zoledronic Acid Application on Bone Maturation in the Consolidation Period in Distraction Osteogenesis

ABSTRACT

Distraction osteogenesis (DO) is a physiological process that generates new bone tissue formation, using progressively separated bone fragments. Recently, several techniques have been investigated to develop the maturation of the new bone tissue. Bisphosphonates was an effective material for the acceleration of bone formation in DO procedures. The purpose of this study was to evaluate the effects of the systemic zoledronic acid application at the beginning of the consolidation period on new bone genesis in a DO model of rat femurs. The rats were divided randomly into 3 groups, as follows: Control group (CNT group) (n = 10), zoledronic acid dosage-1 (n = 10), and dosage-2 (n = 10) groups (ZA-D-1 and ZA-D-2). No treatment was administered in controls, but DO was applied to the rat femurs. A single dose of 0.1 mg/kg and 0.2 mg/kg of zoledronic acid was administered systematically at the beginning of the consolidation period after the distraction in treatment groups, respectively. Histomorphometric analyses were performed on the original distracted bone area and the surrounding bone tissue. Osteoblasts, new bone formation, and fibrosis were scored. New bone formation in the ZA-D-1 and ZA-D-2 groups, when compared with the control group, was detected highly (P < 0.05). The numbers of osteoblasts in the ZA-D-1 and ZA-D-2 groups were higher when compared with the controls (P < 0.05). Fibrosis in the controls, when compared with the ZA-D-1 and ZA-D-2 groups, was found to be higher (P < 0.05). Zoledronic acid application is an effective method for bone maturation in consolidation period in DO.

Local application of alendronate controls bone formation and β-tricalcium phosphate resorption induced by recombinant human bone morphogenetic protein-2

This study examined the ability of local alendronate (ALN) administration to control β-tricalcium phosphate (β-TCP) resorption as well as the induction of bone formation by recombinant human bone morphogenetic protein-2 (rhBMP-2). A 15-mm critical-sized bone defect was created in the diaphysis of rabbit ulnae. Nine female rabbits (4 to 5 months-old) were divided into 3 groups. Group 1 (n = 6 ulnae) animals received implants consisting of β-TCP granules and 25 μg of rhBMP-2 in 6.5% collagen gel. Group 2 (6 ulnae) and Group 3 (6 ulnae) animals received the same implants, but with 10^-6 M and 10^-3 M ALN-treated TCP granules, respectively. Two weeks postsurgery, tartrate-resistant acid phosphatase-positive cell counts, new bone formation, and residual β-TCP were evaluated. This study showed that a high dose of ALN strongly reduced osteoclastic resorption of β-TCP induced by rhBMP-2, resulting in decreased bone formation. In contrast, a low dose of ALN slightly reduced the bone resorptive effect but increased bone formation. These results suggest that osteoclast-mediated resorption plays an important role in bone formation and a coupling-like phenomenon could occur in the β-TCP-implanted area, and that administration of a low dose of ALN may solve clinical bone resorptive problems induced by rhBMP-2.

Mesoporous bioactive glasses for the combined application of osteosarcoma treatment and bone regeneration

In this study, mesoporous bioactive glass (MBG) sub-micro particles were prepared through sol-gel synthesis and possessed a uniform and spherical structure with particle size of 302 ± 43 nm, a pore size of 4 nm and a high surface area of 354 m² g^-1. Alendronate (AL) is often used for the treatment of bone associated diseases, in particular osteosarcoma. However, due to the low bioavailability and high toxicity at increased doses, local and sustained release would be an ideal approach to AL delivery. Here, MBGs and aminated MBGs (AMBG) were applied as carriers for AL loading. High encapsulation efficiency of 75% and 85% and loading efficiency of 60% and 63%, for MBG and AMBG, respectively, was achieved. The release profile of AL from AMBG showed a better sustained and controlled release mechanism compared to MBG. In vitro results demonstrated the non-cytotoxic nature of both MBG and AMBG following exposure to MG63 osteoblast like cell line. AL release from MBG and AMBG, even at lower concentration, provoked decreased MG63 proliferation. The osteogenic potential of MBG and AMBG following exposure to dental pulp stem cells was evaluated using alizarin red assay.

The Effects of Long-term Use of Nitrogen-containing Bisphosphonates on Fracture Healing

Nitrogen-containing bisphosphonates (N-BPs) are pharmaceutical agents that have been used for many years to treat osteoporosis, multiple myeloma, Paget's disease, metastatic bone disease, and a variety of other diseases in which bone mineral density is reduced. Given that N-BPs inhibit bone resorption, an important stage in the fracture healing process, they have been extensively studied in preclinical models for their activity. In animal models, treatment with N-BPs is associated with a larger callus formation in fracture area and delay in remodeling from primary woven bone to lamellar bone, but there is no delay in formation of the fracture callus. In humans, all existing evidence suggest that initiating treatment with N-BPs, after upper and lower limb fractures, does not appear to have a significant effect on fracture healing. Rarely, patients with long-term use of N-BPs may develop "atypical fractures" and delay in their healing. Therefore, this clinical condition is not fully understood and many questions remain unanswered. Similarly, there are few studies about the benefits of stopping a long-term treatment with them, if a fracture occurs. Although most studies support that chronic N-BP therapy may lead to fracture healing delay, this is not fully documented. On the other hand, there are studies that are in complete disagreement with them. All of the above suggest that there is a need for more detailed future research into larger patient populations and different types of fractures, with sufficient data on the type, dosage, route and duration of administration of N-BPs, and the control methods of fracture healing, in order to have a safe final conclusion on the effect of their long-term administration in this highly complex process.

Effects of Local Low-Dose Alendronate Injections Into the Distraction Gap on New Bone Formation and Distraction Rate on Distraction Osteogenesis

Bisphosphonates that constrain bone resorption have a direct effect on osteoclast function. In this experimental study, the effects of low-dose local alendronate injections on the distraction gap (DG) in rabbit mandible at 2 different rates were evaluated.The experimental study was conducted on 20 male, New Zealand white rabbits. The animals were divided into 3 experimental groups and 1 control group. Group 1 consisted of animals with distraction at the rate of 1 mm/day, receiving postoperative local low-dose alendronate local injections into the DG. Group 2 consisted of animals with distraction at the rate of 2 mm/day, receiving postoperative 0.75 μg/kg of alendronate local injections into the DG. Group 3 consisted of animals with distraction at the rate of 2 mm/day, receiving postoperative 0.2 mL local saline injections into the DG. Group 4 consisted of animals with distraction at the rate of 1 mm/day, receiving postoperative 0.2 mL local saline injections into the DG. All the injections were performed immediately postoperatively and for all groups at 1, 2, 3, and 4 weeks following surgery. The distraction zones were evaluated using dual-energy X-ray absorptiometry and histological analysis.Histologically, bone healing was found to be significantly accelerated in Groups 1 and 4 compared with Groups 2 and 3 (P < 0.05). Bone healing was superior in Group 1 and the difference was statistically significant compared with Group 4. There was a significant increase in mean bone mineral density in the 1 mm daily rate groups (Groups 1 and 4) compared with the 2 mm daily rate groups (Groups 2 and 3) (P < 0.05).Local low-dose alendronate injections could be an effective way for improving bone formation in distraction osteogenesis. Furthermore, the results of this study did not support the hypothesis that injections of local low-dose alendronate may allow 2 mm/day instead of 1 mm/day of elongation in the rabbit mandible.

Strategies of enhancing bone regenerate formation in distraction osteogenesis

Distraction osteogenesis (DO) is a commonly used technique in multiple orthopedic sub-specialties, including trauma, oncology and pediatrics. This technique aims to produce new bone formation in the distraction gap in a controlled manner. The issue with this technique has been the high risk of complications, one of which is poor regenerate formation during the distraction process. Although several factors (including patient and operative factors) and techniques (including surgical, mechanical and pharmacological) have been described to ensure successful regenerate formation during the process of DO, these factors are sometimes difficult to control clinically. Our aim from this review is to highlight the different factors that affect DO, modalities to assess the regenerate and review treatment options for poor regenerate in the distraction gap. In addition, we propose a management protocol derived from the available literature that can be used to facilitate the management of inadequate regenerate formation.

PLGA-linked alendronate enhances bone repair in diaphysis defect model

Alendronate (ALN) is known as an anti-resorptive drug for the treatment of osteoporosis. Recently, ALN was found to stimulate osteogenic differentiation in mesenchymal stem cells and enhance new bone formation in calvarial bone defects. Previous in vitro and in vivo studies found that the effective concentration of ALN was approximately 1-10   μm. In the present study, a poly (lactic-co-glycolic acid) (PLGA) cross-linked ALN (PLGA-ALN) with a short-term controlled-release property for local application to enhance bone repair was developed. An in vitro drug-release kinetic test showed that PLGA-ALN microspheres released an effective concentration (50-100 nm) of ALN for 9 days. The effect of PLGA-ALN on bone repair was tested in a rat femoral bone defect model. The biomechanical study results showed that the maximal strength, stiffness and energy absorption were significantly increased in the PLGA-ALN group compared with the PLGA group. The microstructure of the newly formed bone at the defect site was analysed using microcomputed tomography. The PLGA-ALN group significantly improved the trabecular bone volume at the defect site compared with the PLGA group. The fibril collagen and immunolocalized bone morphogenetic protein 2 were evident in the newly formed trabecular bone in the PLGA-ALN group. Local use of newly developed PLGA-ALN-enhanced bone repair was attributable to increasing bone matrix formation, which improved the ultrastructure of the newly formed bone and thus increased the biomechanical properties of the repaired bone. It is suggested that PLGA-ALN may be a potential bone graft substitute to enhance bone repair. Copyright © 2016 John Wiley & Sons, Ltd.

Effects of combined therapy of alendronate and low-intensity pulsed ultrasound on metaphyseal bone repair after osteotomy in the proximal tibia of aged rats

Bisphosphonates and low-intensity pulsed ultrasound (LIPUS) are both known to maintain or promote callus formation during diaphyseal fracture healing. However, the effect of these treatments on the repair of metaphyseal fractures has not been elucidated. To evaluate the effects of bisphosphonates and/or LIPUS on cancellous bone healing, an osteotomy was performed on the proximal tibial metaphysis of 9-month-old Sprague-Dawley rats (n = 64). Treatment with alendronate (1 μg/kg/day), LIPUS (20 min/day), or a combination of both was administered for 2 or 4 weeks, after which changes in bone mineral density (BMD), bone histomorphometric parameters, and the rate of cancellous bony bonding were measured. Alendronate suppressed bone resorption parameters at 2 weeks (p = 0.019) and increased bone volume and BMD at 4 weeks (p = 0.034 and p = 0.008, respectively), without affecting bony bonding. LIPUS had no significant effect on any of the histomorphometric parameters at 2 or 4 weeks, but significantly increased in BMD at 4 weeks (p = 0.026) as well as the percentage of bony bonding at both 2 and 4 weeks (p < 0.01). The combined therapy also showed significantly increased BMD compared with the control group at 4 weeks (p = 0.010) and showed a trend toward increased bony bonding. In conclusion, alendronate and LIPUS cause an additive increase in BMD at the affected metaphysis: alendronate increases the bone volume at the osteotomy site without interrupting metaphyseal repair, whereas LIPUS promotes metaphyseal bone repair, without affecting bone histomorphometric parameters.

Local administration of alendronate reduced peri-tunnel bone loss and promoted graft-bone tunnel healing with minimal systemic effect on bone in contralateral knee

Continued systemic administration of alendronate was reported to reduce peri-tunnel bone resorption and promoted graft-bone tunnel healing at the early stage post-anterior cruciate ligament (ACL) reconstruction. However, systemic increase in bone mineral density (BMD) in the contralateral intact knee was observed. We tested if single local administration of alendronate into the bone tunnel during ACL reconstruction could achieve similar benefits yet without the systemic effect on bone. Seventy-two rats with unilateral ACL reconstruction were divided into three groups: saline, low-dose (6 μg/kg) and mid-dose (60 μg/kg) alendronate. For local administration, alendronate was applied to the bone tunnels for 2 min before graft insertion and repair. At weeks 2 and 6, the reconstructed complex was harvested for high-resolution computed tomography (vivaCT) imaging followed by biomechanical test or histology. Our results showed that local administration of low-dose alendronate showed comparable benefits on the reduction of peri-tunnel bone loss, enhancement of bone tunnel mineralization, tunnel graft integrity, graft osteointegration and mechanical strength of the reconstructed complex at early stage post-reconstruction, yet with minimal systemic effect on mineralized tissue at the contralateral intact knee. A single local administration of alendronate at the low-dose therefore might be used to promote early tunnel graft healing post-reconstruction.

Comparison of local and systemic alendronate on distraction osteogenesis

This study compared the effect of systemic and local administration of alendronate on distraction osteogenesis in rabbit mandibles. Thirty New Zealand white rabbits were allocated to 3 groups: 10 rabbits for systemic alendronate; 9 for local alendronate; and 11 as controls. After a 5 day latency period, distraction was performed at a rate of 0.8mm/day for 9 days via a custom-made distractor. Animals were killed at the end of the consolidation period of 28 days. The distracted mandibles were harvested and evaluated by plain radiography, computed tomography (CT), dual energy X-ray absorptiometry (DEXA), and histomorphometry. Histologically, comparing the systemic and local alendronate groups, there were no statistically significant differences in the bone healing parameters, but each group showed a statistically superior effect over the control group (p<0.05). Quantitative CT evaluation showed a significant difference mean in the density of the regeneration between experimental and control groups. There was a significant increase in mean bone mineral density in the experimental groups compared with the control group. Histologic, CT, and DEXA analysis demonstrated that using systemic and local alendronate may be effective in accelerating new bone formation in the distraction gap in rabbit mandibles.

Locally administered zoledronic Acid therapy for giant cell tumor of bone

Giant cell tumor of bone is locally aggressive and occurs in the meta-epiphyseal region of long bones. Because of its high recurrence rate, local adjuvant therapies such as phenol or liquid nitrogen have been recommended. In the present study, zoledronic acid, a nitrogen-containing bisphosphonate, was administered locally as an adjuvant during a biopsy. An otherwise healthy 43-year-old man presented with pain and swelling in the right knee. Plain radiographs showed an osteolytic lesion of the right proximal tibia. An open biopsy was performed and the intraoperative pathologic diagnosis was giant cell tumor of bone. Following biopsy, the defect was filled with betatricalcium phosphate, and 4 mg of zoledronic acid was locally administered into the tumor lesion. Two months after the biopsy, curettage and bone grafting were performed. Sections were obtained during the curettage for histology to evaluate the response to bisphosphonate treatment. Histologic examination revealed massive tumor cell death in the lesion in which both stromal cells and osteoclast-like giant cells were necrotic. Curettage was performed and the defect was filled with a commercial preshaped hydroxyapatitetricalcium phosphate bone substitute. Eighteen months after curettage, the patient had regained full range of motion and good function of the knee, and radiographs at 18 months after curettage revealed no recurrence of giant cell tumor of bone.

Bisphosphonates in orthopedic applications

Bisphosphonates (BPs) exert potent effects on the skeleton. As such, there are important questions relating to how treatment with BPs for metabolic disorders might affect outcomes of orthopedic problems. A further question is what role, if any, might BPs play as adjunctive therapeutics for orthopedic problems. This article outlines the research thus far in the application of BPs to the management of osteonecrosis, bone repair, and joint arthroplasty. Many animal studies show a benefit to decreasing bone resorption in models of osteonecrosis. These include studies in both small and large animals, backed up by limited human data. Further clinical trials are underway for this indication. In bone repair, again, multiple studies exist. There are concerns that BPs could interfere with the normal processes of healing. Some of the controversy about benefits or adverse effects of BPs in this context can be distilled down to effects of dosing and administration. With some exceptions, longer intervals between dosing seem to be more beneficial while not producing adverse healing effects in animal studies. In joint arthroplasty, animal studies suggest a role for topical or systemic BPs for enhancing bone on-growth to implant surfaces and strength of mechanical fixation, although these are yet to be confirmed in clinical studies. Clinical studies show that BPs inhibit periprosthetic bone loss due to strain-adaptive remodeling and after impaction bone grafting, although an efficacy in inhibiting inflammatory bone loss due to wear particle-induced osteolysis has not been confirmed. Lastly, as anabolic drugs have become available, there is increasing interest in their combined use with BPs. From experimental data, manipulation of both the anabolic and catabolic responses is a powerful approach in models of bone repair.

Effect of risedronate on bone resorption during consolidation phase of distraction osteogenesis: a rabbit model

PURPOSE

To evaluate the effects of continuous local injection of risedronate in the prevention of bone resorption in a lengthened segment.

METHODS

11 male rabbits underwent subperiosteal osteotomy of the left tibia and an external fixator was applied anteromedially. After a lag phase of one week, a 2-week distraction phase and a 5-week consolidation phase followed. Risedronate was continuously injected into the centre of the distracted segment at a rate of 10 micro g/kg/day during the first 14 days of consolidation by a subcutaneously implanted osmotic pump. A control group received purified buffer solution (PBS) using the same protocol. The lengthened bone segments were evaluated using radiography, quantitative computed tomography, and 3-point bending mechanical test.

RESULTS

Risedronate injection prevented osteopenia as compared to PBS injection. The mean bone mineral content, volumetric density and cross-sectional area of the lengthened segments were significantly higher in the risedronate group than in controls (as much as 65%, 30%, and 25%, respectively). There was no significant difference between the 2 groups regarding the ultimate load to failure.

CONCLUSION

Continuous local injection of risedronate into the lengthened segment can prevent osteopenia during distraction osteogenesis but fails to enhance mechanical strength of newly distracted segments.

Effects of alendronate on bone formation and osteoclastic resorption after implantation of beta-tricalcium phosphate

The aim of this study was to determine the effects of alendronate (ALN) on osteoclastic resorption of beta-tricalcium phosphate (beta-TCP) and bone formation. beta-TCP blocks of 75% porosity, with or without ALN treatment, were implanted into cavities drilled in rabbit femoral condyles. New bone formation, residual amount of beta-TCP, and the number of tartrate-resistant acid phosphatase-positive cells were evaluated 2 weeks after surgery. The results show that local application of ALN at a concentration of 10(-2) to 10(-6)M reduced the number of osteoclasts on the surface of beta-TCP. New bone formation was also inhibited by ALN in a dose-dependent manner. Thus, inhibition of osteoclast formation resulted in reduced beta-TCP resorption and bone formation. These results suggest that osteoclast-mediated resorption plays an important role in bone formation and a coupling-like phenomenon could occur in beta-TCP-filled bone defects.

The impact of zoledronic acid on regenerate and native bone after consolidation and removal of the external fixator: an animal model study

We investigated the role of zoledronic acid on the regenerate and native bone after consolidation and removal of the external fixator in a rabbit model of distraction osteogenesis using 28 New Zealand white rabbits. The rabbits were randomly distributed into two groups. The first group received three doses of zoledronic acid (ZA) 0.1 mg/kg subcutaneously at weekly intervals while the second group received injections of sterile saline. Distraction started on day 7 at a rate of 0.8 mm/day for 12 days. At week 3 the average lengthening, regenerate density, and regenerate continuity were comparable between the two groups. At week 11 the regenerate in the treated group had a significant increase in Bone Mineral Density (BMD) and Bone Mineral Content (BMC) compared to the placebo group. On axial compression, the regenerate showed an increase in the peak load and a higher modulus of elasticity in the treated group. At 6 months, radiographs demonstrated signs of osteopenia of the proximal metaphysis in the control group, and failure of new bone formation around the pin sites in the treated group. BMC and BMD value differences between the two groups were not statistically significant. Histologically, there was persistence of more bone trabeculae in the medullary canal of the regenerate with the persistence of the pin-holes in the treated group. Mechanically, the regenerates in the treated group remain stronger in resisting the axial compression. The proximal fragment in the treated group exhibited a statistically significant decrease in the peak load, toughness and efail %. In conclusion, bisphosphonate-treated rabbits have a stronger regenerate during distraction, and directly after removal of the fixator. They do not develop disuse osteopenia in their lengthened tibia. This treatment may shorten the time in the external fixator and prevent fragility fractures in the treated extremity. However, its long-term safety has not yet been established.

The use of alendronate in the treatment of avascular necrosis of the femoral head

The use of bisphosphonates in the treatment of avascular necrosis of the femoral head is an encouraging but relatively new option with most published data being derived from small trials with limited follow-up. We present a clinicoradiological analysis of 395 hips with avascular necrosis which were treated with oral alendronate for three years with a mean follow-up of four years (1 to 8).

Our results show an improvement in the clinical function, a reduction in the rate of collapse and a decrease in the requirement for total hip replacement, compared with the findings of other studies in which no treatment was given. This improvement is particularly marked if the treatment is begun in the pre-collapse stages of the disease. Even in Ficat stage-III hips some benefit was obtained from treatment with alendronate by at least a delay in the need for total hip replacement.

Optimal increase in bone mass by continuous local infusion of alendronate during distraction osteogenesis in rabbits

Several methods have been used to increase bone mass in distraction osteogenesis. Since bone resorption as well as regeneration is stimulated in the distracted segment, bisphosphonate can be a beneficial agent for distraction osteogenesis. Here, we examined the effects of bisphosphonate injected continuously into the regenerate on bone volume, and architectural and mechanical properties of distraction osteogenesis. The left tibia of Japanese White rabbits (n=66) was subjected to slow distraction using an external fixator. At the beginning of the consolidation phase, alendronate (7 microg/kg/day) was infused directly into the lengthened segment for 14 days using an osmotic pump. Control rabbits were infused with phosphate buffered saline (PBS). The tibiae were monitored weekly by soft X-ray and dual-energy X-ray absorptiometry (DXA). The animals were sacrificed at 4, 6, and 8 weeks after operation to examine bone mineral density (BMD) and cortical bone thickness (CBT) by peripheral quantitative computerized tomography (pQCT), while the mechanical property of the lengthened tibia was measured by three-point bending test. In PBS-infused control animals, bone mineral content around the lengthened segment began to decrease after the first week of consolidation phase, forming a tubular bone structure with thin cortex. Infusion of alendronate increased peak bone mineral content around the lengthened segment. At the end of the experiment, volumetric BMD, CBT and mechanical strength of the lengthened segment of the treatment group were approximately twice those of the control animals. Alendronate infused in this manner significantly prevented the osteopenia that critically began early in the consolidation phase, though the dose used in this study was relatively low and no adverse events were noted.