Manipulation of the anabolic and catabolic responses with OP-1 and zoledronic acid in a rat critical defect model

Co-delivery of rhBMP-2 and zoledronic acid using calcium sulfate/hydroxyapatite carrier as a bioactive bone substitute to enhance and accelerate spinal fusion

Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been FDA-approved for lumbar fusion, but supraphysiologic initial burst release due to suboptimal carrier and late excess bone resorption caused by osteoclast activation have limited its clinical usage. One strategy to mitigate the pro-osteoclast side effect of rhBMP-2 is to give systemic bisphosphonates, but it presents challenges with systemic side effects and low local bioavailability. The aim of this in vivo study was to analyze if posterolateral spinal fusion (PLF) could be improved by utilizing a calcium sulfate/hydroxyapatite (CaS/HA) carrier co-delivering rhBMP-2 and zoledronic acid (ZA). Six groups were allocated (CaS/HA, CaS/HA + BMP-2, CaS/HA + systemic ZA, CaS/HA + local ZA, CaS/HA + BMP-2 + systemic ZA, and CaS/HA + BMP-2 + local ZA). 10-week-old male Wistar rats, were randomly assigned to undergo L4-L5 PLF with implantation of group-dependent scaffolds. At 3 and 6 weeks, the animals were euthanized for radiography, μCT, histological staining, or biomechanical testing to evaluate spinal fusion. The results demonstrated that the CaS/HA biomaterial alone or in combination with local or systemic ZA didn't support PLF. However, the delivery of rhBMP-2 significantly promoted PLF. Combining systemic ZA with BMP-2 didn't enhance spinal fusion. Notably, the co-delivery of rhBMP-2 and ZA using the CaS/HA carrier significantly enhanced and accelerated PLF, without inhibiting systemic bone turnover, and potentially reduced the dose of rhBMP-2. Together, the treatment regimen of CaS/HA biomaterial co-delivering rhBMP-2 and ZA could potentially be a safe and cost-effective off-the-shelf bioactive bone substitute to enhance spinal fusion.

Modeling anabolic and antiresorptive therapies for fracture healing in a mouse model of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a genetic bone fragility disorder that features frequent fractures. Bone healing outcomes are contingent on a proper balance between bone formation and resorption, and drugs such as bone morphogenetic proteins (BMPs) and bisphosphonates (BPs) have shown to have utility in modulating fracture repair. While BPs are used for OI to increase BMD and reduce pain and fracture rates, there is little evidence for using BMPs as local agents for fracture healing (alone or with BPs). In this study, we examined wild-type and OI mice (Col1a2^+/G610C ) in a murine tibial open fracture model with (i) surgery only/no treatment, (ii) local BMP-2 (10 µg), or (iii) local BMP-2 and postoperative zoledronic acid (ZA; 0.1 mg/kg total dose). Microcomputed tomography reconstructions of healing fractures indicated BMP-2 was less effective in an OI setting, however, BMP-2 +ZA led to considerable increases in bone volume (+193% WT, p < 0.001; +154% OI, p < 0.001) and polar moment of inertia (+125% WT, p < 0.01; +248% OI, p < 0.05). Tissue histology revealed a thinning of the neocortex of the callus in BMP-2 treated OI bone, but considerable retention of woven bone in the healing callus with BMP + ZA specimens. These data suggest a cautious approach may be warranted with the sole application of BMP-2 in an OI surgical setting as a bone graft substitute. However, this may be overcome by off-label BP administration.

Early bisphosphonate therapy post proximal femoral fracture fixation does not impact fracture healing: a systematic review and meta-analysis

BACKGROUND

There is conjecture on the optimal timing to administer bisphosphonate therapy following operative fixation of low-trauma hip fractures. Factors include recommendations for early opportunistic commencement of osteoporosis treatment, and clinician concern regarding the effect of bisphosphonates on fracture healing. We performed a systematic review and meta-analysis to determine if early administration of bisphosphonate therapy within the first month post-operatively following proximal femur fracture fixation is associated with delay in fracture healing or rates of delayed or non-union.

METHODS

We included randomized controlled trials examining fracture healing and union rates in adults with proximal femoral fractures undergoing osteosynthesis fixation methods and administered bisphosphonates within 1 month of operation with a control group. Data were pooled in meta-analyses where possible. The Cochrane Risk of Bias Tool and the GRADE approach were used to assess validity.

RESULTS

For the outcome of time to fracture union, meta-analysis of three studies (n = 233) found evidence for earlier average time to union for patients receiving early bisphosphonate intervention (MD = -1.06 weeks, 95% CI -2.01--0.12, I²  = 8%). There was no evidence from two included studies comprising 718 patients of any difference in rates of delayed union (RR 0.61, 95% CI 0.25-1.46). Meta-analyses did not demonstrate a difference in outcomes of mortality, function or pain.

CONCLUSIONS

We provide low-level evidence that there is no reduction in time to healing or delay in bony union for patients receiving bisphosphonates within 1 month of proximal femur fixation.

The Role Of BMPs in the Regulation of Osteoclasts Resorption and Bone Remodeling: From Experimental Models to Clinical Applications

In response to mechanical forces and the aging process, bone in the adult skeleton is continuously remodeled by a process in which old and damaged bone is removed by bone-resorbing osteoclasts and subsequently is replaced by new bone by bone-forming cells, osteoblasts. During this essential process of bone remodeling, osteoclastic resorption is tightly coupled to osteoblastic bone formation. Bone-resorbing cells, multinuclear giant osteoclasts, derive from the monocyte/macrophage hematopoietic lineage and their differentiation is driven by distinct signaling molecules and transcription factors. Critical factors for this process are Macrophage Colony Stimulating Factor (M-CSF) and Receptor Activator Nuclear Factor-κB Ligand (RANKL). Besides their resorption activity, osteoclasts secrete coupling factors which promote recruitment of osteoblast precursors to the bone surface, regulating thus the whole process of bone remodeling. Bone morphogenetic proteins (BMPs), a family of multi-functional growth factors involved in numerous molecular and signaling pathways, have significant role in osteoblast-osteoclast communication and significantly impact bone remodeling. It is well known that BMPs help to maintain healthy bone by stimulating osteoblast mineralization, differentiation and survival. Recently, increasing evidence indicates that BMPs not only help in the anabolic part of bone remodeling process but also significantly influence bone catabolism. The deletion of the BMP receptor type 1A (BMPRIA) in osteoclasts increased osteoblastic bone formation, suggesting that BMPR1A signaling in osteoclasts regulates coupling to osteoblasts by reducing bone-formation activity during bone remodeling. The dual effect of BMPs on bone mineralization and resorption highlights the essential role of BMP signaling in bone homeostasis and they also appear to be involved in pathological processes in inflammatory disorders affecting bones and joints. Certain BMPs (BMP2 and -7) were approved for clinical use; however, increased bone resorption rather than formation were observed in clinical applications, suggesting the role BMPs have in osteoclast activation and subsequent osteolysis. Here, we summarize the current knowledge of BMP signaling in osteoclasts, its role in osteoclast resorption, bone remodeling, and osteoblast–osteoclast coupling. Furthermore, discussion of clinical application of recombinant BMP therapy is based on recent preclinical and clinical studies.

Case Report: Reconstruction of a Large Maxillary Defect With an Engineered, Vascularized, Prefabricated Bone Graft

The reconstruction of complex midface defects is a challenging clinical scenario considering the high anatomical, functional, and aesthetic requirements. In this study, we proposed a surgical treatment to achieve improved oral rehabilitation and anatomical and functional reconstruction of a complex defect of the maxilla with a vascularized, engineered composite graft. The patient was a 39-year-old female, postoperative after left hemimaxillectomy for ameloblastic carcinoma in 2010 and tumor-free at the 5-year oncological follow-up. The left hemimaxillary defect was restored in a two-step approach. First, a composite graft was ectopically engineered using autologous stromal vascular fraction (SVF) cells seeded on an allogenic devitalized bone matrix. The resulting construct was further loaded with bone morphogenic protein-2 (BMP-2), wrapped within the latissimus dorsi muscle, and pedicled with an arteriovenous (AV) bundle. Subsequently, the prefabricated graft was orthotopically transferred into the defect site and revascularized through microvascular surgical techniques. The prefabricated graft contained vascularized bone tissue embedded within muscular tissue. Despite unexpected resorption, its orthotopic transfer enabled restoration of the orbital floor, separation of the oral and nasal cavities, and midface symmetry and allowed the patient to return to normal diet as well as to restore normal speech and swallowing function. These results remained stable for the entire follow-up period of 2 years. This clinical case demonstrates the safety and the feasibility of composite graft engineering for the treatment of complex maxillary defects. As compared to the current gold standard of autologous tissue transfer, this patient’s benefits included decreased donor site morbidity and improved oral rehabilitation. Bone resorption of the construct at the ectopic prefabrication site still needs to be further addressed to preserve the designed graft size and shape.

Local dual delivery therapeutic strategies: Using biomaterials for advanced bone tissue regeneration

Bone development is a complex process involving a vast number of growth factors and chemical substances. These factors include transforming growth factor-beta, platelet-derived growth factor, insulin-like growth factor, and most importantly, the bone morphogenetic protein, which exhibits excellent therapeutic value in bone repair. However, the spatial-temporal relationship in the expression of these factors during bone formation makes the bone repair a more complicated process to address. Thus, using a single therapeutic agent to address bone formation does not seem to provide a clinically effective option. Conversely, a dual delivery approach facilitating the co-delivery of agents has proved to be a dynamic alternative since such a strategy can provide more efficient spatial-temporal action. Such delivery systems can smartly target more than one pathway or differentiation lineage and thus offer more efficient bone regeneration. This review discusses various dual delivery strategies reported in the literature employed to achieve improved bone regeneration. These include concurrent use of different therapeutic agents (including growth factors and drugs), enhancing bone formation and cell recruitment, and improving the efficiency of bone healing.

Zoledronate Bound to Ceramics Increases Ectopic Bone Volume Induced by rhBMP6 Delivered in Autologous Blood Coagulum in Rats

Autologous bone graft substitute (ABGS) containing rhBMP6 in autologous blood coagulum (ABC) with synthetic ceramics is a novel therapeutic solution for bone repair. The aim of this study was to investigate whether the application of Zoledronate (ZOL) with ABGS might enhance the properties of newly formed bone. The effect of ZOL on bone induction was tested in a rat subcutaneous implant model. ZOL bound to synthetic ceramics was added into ABGS implants, and the quantity, quality, and longevity of the induced bone were assessed by micro-CT, histomorphometry, and histology over a period of 365 days. Local use of ZOL in the ABGS implants with ceramics had no influence on the bone volume (BV) on day 14 but subsequently significantly increased BV on days 35, 50, 105, 140, and 365 compared to the control implants. Locally applied ZOL had a similar effect in all of the applied doses (2–20 µg), while its systemic use on stimulating the BV of newly induced bone by ABGS depended on the time of application. BV was increased when ZOL was applied systemically on day 14 but had no effect when applied on day 35. The administration of ZOL bound to ceramics in ABGS increased and maintained the BV over a period of one year, offering a novel bone tissue engineering strategy for treating bone defects and spinal fusions.

The Bone Regeneration Capacity of BMP-2 + MMP-10 Loaded Scaffolds Depends on the Tissue Status

Biomaterials-mediated bone formation in osteoporosis (OP) is challenging as it requires tissue growth promotion and adequate mineralization. Based on our previous findings, the development of scaffolds combining bone morphogenetic protein 2 (BMP-2) and matrix metalloproteinase 10 (MMP-10) shows promise for OP management. To test our hypothesis, scaffolds containing BMP-2 + MMP-10 at variable ratios or BMP-2 + Alendronate (ALD) were prepared. Systems were characterized and tested in vitro on healthy and OP mesenchymal stem cells and in vivo bone formation was studied on healthy and OP animals. Therapeutic molecules were efficiently encapsulated into PLGA microspheres and embedded into chitosan foams. The use of PLGA (poly(lactic-co-glycolic acid)) microspheres as therapeutic molecule reservoirs allowed them to achieve an in vitro and in vivo controlled release. A beneficial effect on the alkaline phosphatase activity of non-OP cells was observed for both combinations when compared with BMP-2 alone. This effect was not detected on OP cells where all treatments promoted a similar increase in ALP activity compared with control. The in vivo results indicated a positive effect of the BMP-2 + MMP-10 combination at both of the doses tested on tissue repair for OP mice while it had the opposite effect on non-OP animals. This fact can be explained by the scaffold’s slow-release rate and degradation that could be beneficial for delayed bone regeneration conditions but had the reverse effect on healthy animals. Therefore, the development of adequate scaffolds for bone regeneration requires consideration of the tissue catabolic/anabolic balance to obtain biomaterials with degradation/release behaviors suited for the existing tissue status.

Timing of Bisphosphonate (Alendronate) Initiation after Surgery for Fragility Fracture: A Population-Based Cohort Study

Bisphosphonates are used as first-line treatment for the prevention of fragility fracture (FF); they act by inhibiting osteoclast-mediated bone resorption. The timing of their administration after FF surgery is controversial; thus, we compared the incidence of second FF, surgery for second FF, and adverse events associated with early initiation of bisphosphonates (EIBP, within 3 months of FF surgery) and late initiation of bisphosphonates (LIBP, 3 months after FF surgery) in bisphosphonate-naïve patients. This retrospective population-based cohort study used data from Taiwan’s Health and Welfare Data Science Center (2004–2012). A total of 298,377 patients received surgeries for FF between 2006 and 2010; of them, 1209 (937 EIBP and 272 LIBP) received first-time bisphosphonates (oral alendronate, 70 mg, once a week). The incidence of second FF (subdistribution hazard ratio (SHR) = 0.509; 95% confidence interval (CI): 0.352–0.735), second FF surgery (SHR = 0.452; 95% CI: 0.268–0.763), and adverse events (SHR = 0.728; 95% CI: 0.594–0.893) was significantly lower in the EIBP group than in the LIBP group. Our findings indicate that bisphosphonates should be initiated within 3 months after surgery for FF.

Intravenous bisphosphonate therapy does not delay fracture healing in inter-trochanteric femur fractures - A randomised controlled study

Hip fractures in elderly are commonly associated with osteoporosis and surgical outcome is influenced by its concurrent management. The purpose of our study is to determine the association between timing of bisphosphonate administration in inter-trochanteric (IT) fractures and fracture healing. Patients with IT fractures (aged≥50 years) and T-score ≤ -1.5 [WHO defines osteopenia as T-score between -1 and -2.5, and osteoporosis as T-score ≤ -2.5 on DEXA scan (which was obtained post-operatively in our cohort)], who underwent proximal femoral nailing were included. Patients were divided into three groups: group 1a-intravenous bisphosphonate {ivBP [zoledronic acid (ZA)]} given within one week, group 1b-ZA at six weeks and group 2-control group. Post-operative radiographs were assessed for reduction parameters [neck-shaft angle, tip-apex distance, reduction variance]. Radiological union was determined using RUSH score and functional outcome (at one year) with Modified Harris Hip Scores. 41 (23 males), 40 (15 males) and 42 (15 males) patients were included in groups 1a, 1b and 2, respectively (no statistical difference in sex distribution among the groups; p = 0.12). Mean age in groups 1a, 1b and 2 was 71.8 ± 8.1, 75.9 ± 8.5 and 72.3 ± 10.6 years (p = 0.09). There was no significant difference in the pattern of injuries (AO classification) among the groups (p = 0.72). Mean time to union in groups 1a, 1b and 2 was 13.7,13.7 and 14.2 weeks, respectively (p = 0.69). Mean time to union in AO types A1, A2 and A3 fractures was 13.2 ± 2.1, 13.7 ± 2.8 and 16.1 ± 4.9 weeks (p = 0.01). We did not observe any association between T-scores and fracture union (hip:p = 0.52, spine:p = 0.93).The functional outcome was similar among groups (p = 0.96). Early administration of ZA did not negatively influence fracture healing in patients undergoing fixation of IT fractures. Among the various other factors analyzed, there was a statistically significant association between the fracture type (AO type A3) and longer time to fracture union.

A facile one-stage treatment of critical bone defects using a calcium sulfate/hydroxyapatite biomaterial providing spatiotemporal delivery of bone morphogenic protein-2 and zoledronic acid

Bone morphogenic proteins (BMPs) are the only true osteoinductive molecules. Despite being tremendously potent, their clinical use has been limited for reasons including supraphysiological doses, suboptimal delivery systems, and the pro-osteoclast effect of BMPs. Efforts to achieve spatially controlled bone formation using BMPs are being made. We demonstrate that a carrier consisting of a powder of calcium sulfate/hydroxyapatite (CaS/HA) mixed with bone active molecules provides an efficient drug delivery platform for critical femoral defect healing in rats. The bone-active molecules were composed of osteoinductive rhBMP-2 and the bisphosphonate, and zoledronic acid (ZA) was chosen to overcome BMP-2-induced bone resorption. It was demonstrated that delivery of rhBMP-2 was necessary for critical defect healing and restoration of mechanical properties, but codelivery of BMP-2 and ZA led to denser and stronger fracture calluses. Together, the CaS/HA biomaterial with rhBMP-2 and/or ZA can potentially be used as an off-the-shelf alternative to autograft bone.

Synergistic use of biomaterials and licensed therapeutics to manipulate bone remodelling and promote non-union fracture repair

Disrupted bone metabolism can lead to delayed fracture healing or non-union, often requiring intervention to correct. Although the current clinical gold standard bone graft implants and commercial bone graft substitutes are effective, they possess inherent drawbacks and are limited in their therapeutic capacity for delayed union and non-union repair. Research into advanced biomaterials and therapeutic biomolecules has shown great potential for driving bone regeneration, although few have achieved commercial success or clinical translation. There are a number of therapeutics, which influence bone remodelling, currently licensed for clinical use. Providing an alternative local delivery context for these therapies, can enhance their efficacy and is an emerging trend in bone regenerative therapeutic strategies. This review aims to provide an overview of how biomaterial design has advanced from currently available commercial bone graft substitutes to accommodate previously licensed therapeutics that target local bone restoration and healing in a synergistic manner, and the challenges faced in progressing this research towards clinical reality.

The Bone Morphogenetic Protein Pathway: The Osteoclastic Perspective

Bone health crucially relies on constant bone remodeling and bone regeneration, both tightly controlled processes requiring bone formation and bone resorption. Plenty of evidence identifies bone morphogenetic proteins (BMP) as major players in osteoblast differentiation and thus, bone formation. However, in recent past years, researchers also increasingly reported on the pivotal role of these multi-functional growth factors in osteoclast formation and activity. This review aims to summarize the current knowledge of BMP signaling within the osteoclast lineage, its role in bone resorption, and osteoblast-osteoclast coupling. Furthermore, subsequent clinical implications for recombinant BMP therapy will be discussed in view of recent preclinical and clinical studies.

Longitudinal in vivo monitoring of callus remodeling in BMP-7- and Zoledronate-treated fractures

Pharmacological interventions that combine pro-anabolic and anti-catabolic drugs to treat recalcitrant fractures have shown remarkable efficacy in augmenting the regenerative response. Specifically, in rodent models of fracture repair, treatment with BMP-7 and Zoledronate (ZA) has almost uniformally resulted in complete union. However, delayed remodeling may be problematic for ZA-treated fractures. The increase in newly formed bone is substantial but if translated in humans, delayed remodeling may delay functional recovery. Our objective was to determine if, and to what extent, bone morphogenetic protein (BMP) (in synergistically administered BMP-7 + ZA) can modulate the delayed hard callus remodeling caused by ZA. Callus remodeling in BMP-7-only and BMP-7 + ZA-treated osteotomies were monitored using in vivo µCT to follow the progression of healing at 6-week intervals over 24 weeks in an open femoral fracture rat model. None of the groups recovered baseline cortical bone volumes within 24 weeks post-osteotomy. Treatment prolonged the remodeling phase but the kinetics of remodeling appeared to differ between BMP and BMP + ZA groups. However, the mechanical characteristics were largely restored. Callus/bone volumes in BMP-only treated fractures peaked as early as week 3 suggesting that remodeling is stimulated prematurely. However, this rate of remodeling was not maintained as BMP-7 was found to exhibit negligible changes in callus/bone volumes between weeks 6 and 18, whereas declines in callus/bone volumes were present at these time points in the BMP-7 + ZA group. Our findings suggest that inclusion of ZA as an anti-catabolic agent may not be detrimental to the regenerative process despite a prolonged remodeling phase.

Synthesis and Characterization of a Biocomposite Bone Bandage for Controlled Delivery of Bone-Active Drugs in Fracture Nonunions

Fracture nonunions are common in orthopedics and their treatment often involves multiple surgical interventions. The aim of this study was to fabricate and characterize a gelatin-nano-hydroxyapatite membrane (GM)-based bone bandage for controlled delivery of bio-active molecules; recombinant human bone morphogenic protein-2 (rhBMP-2) and zoledronic acid (ZA) to promote osteoinduction and prevent callus resorption, respectively. In vitro cell-material interaction experiments using MC3T3 cells seeded on the GM indicated good biocompatibility. rhBMP-2-functionalized GM promoted osteogenic differentiation of MC3T3 cells and the rhBMP-2 bio-activity thus remained, as indicated by increased levels of alkaline phosphatase compared to only GM. The GM released a small amount (1.1%) of rhBMP-2 in vitro over a period of 5 weeks, demonstrating a strong interaction of rhBMP-2 with the GM. In the first animal study, the GM specimens loaded with rhBMP-2 or with the combination of rhBMP-2 + ZA were placed in the abdominal muscle pouch of rats. In the GM + rhBMP-2 + ZA group, significantly higher bone volume (21.5 ± 5.9 vs 2.7 ± 1.0 mm³) and area (3.3 ± 2.3 vs 1.0 ± 0.4 mm²) of bone were observed compared to GM + rhBMP-2 after 4 weeks, as indicated by micro-computed tomography and histomorphometry, respectively. Finally, a nonunion model in rats was used to evaluate the efficacy of the GM bandage and bio-active molecules in healing of fracture nonunions. The GM functionalized with rhBMP-2 + ZA led to higher bone formation around the fracture (63.9 ± 19.0 vs 31.8 ± 3.7 mm³) and stronger fracture callus (110.8 ± 46.8 vs 45.6 ± 17.8 N) compared to the empty controls. However, the overall union rate was only marginally improved. The GM alone or combined with ZA did not aid in bone healing in this model. Thus, this study shows that controlled delivery of rhBMP-2 + ZA via the developed GM is a promising approach that could aid in earlier full load bearing in patients with nonunion.

Adjuvant drug-assisted bone healing: Part III - Further strategies for local and systemic modulation

In this third in a series of reviews on adjuvant drug-assisted bone healing, further approaches aiming at influencing the healing process are discussed. Local and systemic modulation of bone metabolism is pursued with use of a number of drugs with completely different indications, which are characterized by a pleiotropic spectrum of action. These include drugs used to treat lipid disorders (HMG-CoA reductase inhibitors), hypertension (ACE inhibitors), osteoporosis (bisphosphonates), cancer (proteasome inhibitors) and others. Potential applications to enhance bone healing are discussed.

Phosphate functionalization and enzymatic calcium mineralization synergistically enhance oligo[poly(ethylene glycol) fumarate] hydrogel osteoconductivity for bone tissue engineering

A current approach in bone tissue engineering is the implantation of polymeric scaffolds that promote osteoblast attachment and growth as well as biomineralization. One promising polymer is oligo[poly(ethylene glycol) fumarate] (OPF), a polyethylene glycol-based material that is biocompatible, injectable, and biodegradable, but in its native form does not support robust bone cell attachment or growth. To address this issue, this study evaluated the osteoconductivity of bis[02-(methacryloyloxy)ethyl] phosphate (BP) functionalized OPF hydrogels (OPF-BP) using MC3T3-E1 pre-osteoblast cells, both before and after enzymatic mineralization with a calcium solution. The inclusion of negatively charged functional groups allowed for the tailored uptake and release of calcium, while also altering the mechanical properties and surface topography of the hydrogel surface. In cell culture, OPF-BP hydrogels with 20 and 30% (w/w) BP optimized osteoblast attachment, proliferation, and differentiation after a 21-day in vitro period. In addition, the OPF-BP30 treatment, when mineralized with calcium, exhibited a 128% increase in osteocalcin expression when compared with the non-mineralized treatment. These findings suggest that phosphate functionalization and enzymatic calcium mineralization can act synergistically to enhance the osteoconductivity of OPF hydrogels, making this processed material an attractive candidate for bone tissue engineering applications.

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.

A Bioactive Coating Enhances Bone Allografts in Rat Models of Bone Formation and Critical Defect Repair

Bone allografts are inferior to autografts for the repair of critical-sized defects. Prior studies have suggested that bone morphogenetic protein-2 (BMP-2) can be combined with allografts to produce superior healing. We created a bioactive coating on bone allografts using polycondensed deoxyribose isobutyrate ester (PDIB) polymer to deliver BMP-2 ± the bisphosphonate zoledronic acid (ZA) and tested its ability to enhance the functional utility of allografts in preclinical Wistar rat models. One ex vivo and two in vivo proof-of-concept studies were performed. First, PDIB was shown to be able to coat bone grafts (BGs). Second, PDIB was used to coat structural allogenic corticocancellous BG with BMP-2 ± ZA ± hydroxyapatite (HA) microparticles and compared with PDIB-coated grafts in a rat muscle pouch model. Next, a rat critical defect model was performed with treatment groups including (i) empty defect, (ii) BG, (iii) collagen sponge + BMP-2, (iv) BG + PDIB/BMP-2, and (v) BG + PDIB/BMP-2/ZA. Key outcome measures included detection of fluorescent bone labels, microcomputed tomography (CT) quantification of bone, and radiographic healing. In the muscle pouch study, BMP-2 did not increase net bone volume measured by microCT, however, fluorescent labeling showed large amounts of new bone. Addition of ZA increased BV by sevenfold (p < 0.01). In the critical defect model, allografts were insufficient to promote reliable union, however, union was achieved in collagen/BMP-2 and all BG/BMP-2 groups. Statement of clinical significance: These data support the concept that PDIB is a viable delivery method for BMP-2 and ZA delivery to enhance the bone forming potential of allografts. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2278-2286, 2019.

Biomodulation of an implant for enhanced bone-implant anchorage

Aseptic loosening of implants is the major cause for revision surgery. By modulating the bone-implant interface, early bone-implant anchorage could be improved. Implant surface manipulation by the addition of osteopromotive molecules locally and systemically to promote implant integration has been described with limited success. This study describes a novel approach by making the implant capable of biologically modulating its surroundings. It was hypothesized that the early implant fixation would improve by filling the interior of the implant with a carrier providing spatio-temporal release of bone active drugs with known osteogenic effect. The implant consisted of a threaded polyether ether ketone (PEEK) hollow chamber with holes at the bottom. The implant was filled with a calcium sulphate (CaS)/hydroxyapatite (HA) carrier, delivering two bone active molecules; zoledronic acid (ZA) and bone morphogenic protein-2 (BMP-2). At first, a rat abdominal muscle pouch model indicated a sustained in-vivo release of both ¹²⁵I-rhBMP-2 (57%) and ¹⁴C-ZA (22%) from the CaS/HA carrier over a period of 4-weeks. The biomodulated implant was then inserted in the proximal tibia in rats with the following experimental groups: G1) Empty implant, G2) Implant + CaS/HA, G3) Implant + CaS/HA + ZA and G4) Implant + CaS/HA + ZA + rhBMP-2. Significantly higher bone volume (BV) was seen around the implant in groups G3 (3.3 ± 0.7 mm³) and G4 (3.1 ± 0.7 mm³) compared to the control (1.3 ± 0.4 mm³) using micro-computed tomography and qualitative histology. Group G3, also exhibited significantly higher pull-out force and absorbed energy when compared to the control group G1. These findings indicate that a low dose of ZA alone, released in a controlled manner from within a fenestrated implant is enough to improve implant anchorage without the need of adding rhBMP-2. This simple method of using a fenestrated implant containing a ceramic carrier releasing bone active molecules improved bone anchorage and could clinically reduce prosthetic failure. STATEMENT OF SIGNIFICANCE: Aseptic loosening remains as a major cause for implant revisions and early reaction of surrounding bone to the prosthesis is important for longevity. A novel approach to enhance early bone-implant anchorage is presented. The implant is filled with a carrier providing controlled release of bone active molecules. In an animal model, a calcium sulphate (CaS)/hydroxyapatite (HA) carrier was used to provide a spatio-temporal release of bone morphogenic protein-2 (BMP-2) and zoledronic acid (ZA). Significantly better bone-implant integration was achieved using ZA alone, thereby eliminating the need for adding BMP-2. The developed method of implant biomodulation holds potential to prevent implant loosening and is an alternative to prosthetic coatings or systemic drug treatment. Importantly, all constituents are approved for clinical use.

Autologous mesenchymal stem cell implantation, hydroxyapatite, bone morphogenetic protein-2, and internal fixation for treating critical-sized defects: a translational study

INTRODUCTION

Critical-sized defect (CSD) is one of the most challenging cases for orthopaedic surgeons. We aim to explore the therapeutic potential of the combination of bone marrow-derived mesenchymal stem cells (BM-MSCs), hydroxyapatite (HA) granules, bone morphogenetic protein-2 (BMP-2), and internal fixation for treating CSDs.

METHODS

This was a translational study performed during the period of January 2012 to 2016. Subjects were patients diagnosed with CSDs who had previously failed surgical attempts. They were treated with the combination of autologous BM-MSCs, HA granules, BMP-2, and mechanical stabilization. Post-operative pain level, functional outcome, defect volume, and radiological healing were evaluated after a minimum follow-up of 12 months.

RESULTS

A total of six subjects were recruited in this study. The pain was significantly reduced in all cases; with the decrease of mean preoperative visual analog scale (VAS) from 4 ± 2.2 to 0 after six month follow-up. Clinical functional outcome percentage increased significantly from 25 ± 13.7 to 70.79 ± 19.5. Radiological healing assessment using Tiedemann score also showed an increase from 0.16 ± 0.4 to 8 ± 3 at one year follow-up. No immunologic nor neoplastic side effects were found.

CONCLUSIONS

The combination of autologous BM-MSCs, HA granules, and BMP-2 is safe and remains to be a good option for the definitive treatment for CSD with previous failed surgical attempts. Further studies with a larger sample size are required to be done.

18F-fluoride as a prognostic indicator of bone regeneration

Positron emission tomography (PET) is a form of nuclear imaging, which quantitatively assesses the metabolic activity through the uptake of radioactive tracers. ¹⁸F-fluoride is a positron-emitting isotope with high affinity for bone. Despite its potential as a non-invasive measure of bone metabolism, quantitative ¹⁸F-fluoride PET has only been used sparsely in orthopaedic applications. It has been speculated that ¹⁸F-fluoride PET characterizes cellular activity of bone forming cells in the early stages of the regenerative process and therefore precedes the mineralization detected by conventional computed tomography (CT). Our aim was thus to combine in vivo PET and CT to map the spatiotemporal course of bone regeneration during fracture healing using an open femur fracture model in the rat and characterize regeneration in untreated and pharmacologically treated fractures using both imaging modalities. We hypothesized that PET ¹⁸F-fluoride tracer activity at an earlier time point is predictive of CT measured bone formation at a later time point. On the basis of the RMSE and R² metrics of linear regression models it was conceivable for bone volumes to be predicted up to three weeks in advance in a rodent model (RMSE: 14 mm³-18 mm³, R²: 0.79-0.82). Moreover, the data suggested that ¹⁸F-fluoride positron-emitting activity had the potential to separate bone formation from resorption and thus could be of interest across a wide array of orthopaedic applications. Based on this data, we conclude that ¹⁸F-fluoride positron-emitting activity is strongly correlated to bone formation and could potentially predict the volume of bone regenerated at fracture sites. The volume of bone regenerated at a fracture site can be interpreted as a measure of the healing response and ¹⁸F-fluoride should be further investigated as a predictive diagnostic tool to identify if bone fractures will heal successfully or result in delayed healing or non-union. STATEMENT OF SIGNIFICANCE: We aimed to combine in vivo PET and CT imaging to map the spatiotemporal course of bone regeneration during fracture healing using an open femur fracture model in the rat and characterize regeneration in untreated and pharmacologically treated fractures using both imaging modalities. We hypothesized that PET ¹⁸F-fluoride tracer activity at an earlier time point is predictive of CT measured bone formation at a later time point. Our data suggest that ¹⁸F-fluoride positron-emitting activity can separate bone formation from resorption and thus could be of interest across a wide array of orthopaedic applications including as a predictive diagnostic tool to identify if fractures will heal successfully or result in delayed healing or non-union.

Effects of Zoledronic Acid Treatment on Fracture Healing, Morbidity and Mortality in Elderly Patients with Osteoporotic Hip Fractures

Background

In this study, the effects of zoledronic acid (ZolA) administered at different times to patients undergoing surgical treatment for hip fracture were investigated.

Materials and methods

Ninety patients who underwent surgical treatment for osteoporotic (OP) hip fractures between February 2013 and September 2016 in our hospital were included in the study. After surgical treatment, patients were allocated into three groups: group I—patients who had osteosynthesis using proximal femoral nail (PFN) for an intertrochanteric fracture of the femur were given ZolA within 1 week after fracture and before discharge; group II—patients who had osteosynthesis using the PFN for an intertrochanteric fracture of the femur were given ZolA within 1 month after fracture post-discharge; group III—patients in the same age group who had a hemiarthroplasty (HA) for an intertrochanteric fracture of the femur were administered ZolA before discharge. In addition, all patients were given daily oral calcium and vitamin D3. The Radiographic Union Score for Hip (RUSH), Harris Hip Score (HHS), and bone mineral density (BMD) were used at the follow-up as evaluation criteria, and complications were noted.

Results

There were no significant differences between groups in terms of demographic data and laboratory outcomes (p > 0.05). Radiographic Union Score for Hip scores were similar between groups I and II (p > 0.05). Fracture union occurred by the sixth month in all patients whose results were evaluated. No statistically significant difference was found between three groups (p > 0.05). There was no difference between the three groups in the hip and vertebrae BMD and t scores (p > 0.05). When t and BMD scores before treatment were compared with those at 1 year after treatment, a benefit from ZolA treatment was observed in all three groups (p < 0.05).

Conclusion

This study shows that the timing of ZolA administration has no effect on fracture healing and complication incidence in elderly patients with hip fractures. In addition, ZolA was found to be beneficial in increasing BMD of both femur and vertebra in all groups, but there was no significant difference between the groups.

Clinical significance

The study demonstrated that ZolA may be used early in the treatment of osteoporotic hip fractures with PFN.

How to cite this article

Sargin S, Konya MN, Gulcu A, et al. Effects of Zoledronic Acid Treatment on Fracture Healing, Morbidity and Mortality in Elderly Patients with Osteoporotic Hip Fractures. Strategies Trauma Limb Reconstr 2019;14(3):126–131.

Preclinical models for orthopedic research and bone tissue engineering

In this review, we broadly define and discuss the preclinical rodent models that are used for orthopedics and bone tissue engineering. These range from implantation models typically used for biocompatibility testing and high-throughput drug screening, through to fracture and critical defect models used to model bone healing and severe orthopedic injuries. As well as highlighting the key methods papers describing these techniques, we provide additional commentary based on our substantive practical experience with animal surgery and in vivo experimental design. This review also briefly touches upon the descriptive and functional outcome measures and power calculations that are necessary for an informative study. Obtaining informative and relevant research outcomes can be very dependent on the model used, and we hope this evaluation of common models will serve as a primer for new researchers looking to undertake preclinical bone studies. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:832-840, 2018.

In situ bone tissue engineering via ultrasound-mediated gene delivery to endogenous progenitor cells in mini-pigs

More than 2 million bone-grafting procedures are performed each year using autografts or allografts. However, both options carry disadvantages, and there remains a clear medical need for the development of new therapies for massive bone loss and fracture nonunions. We hypothesized that localized ultrasound-mediated, microbubble-enhanced therapeutic gene delivery to endogenous stem cells would induce efficient bone regeneration and fracture repair. To test this hypothesis, we surgically created a critical-sized bone fracture in the tibiae of Yucatán mini-pigs, a clinically relevant large animal model. A collagen scaffold was implanted in the fracture to facilitate recruitment of endogenous mesenchymal stem/progenitor cells (MSCs) into the fracture site. Two weeks later, transcutaneous ultrasound-mediated reporter gene delivery successfully transfected 40% of cells at the fracture site, and flow cytometry showed that 80% of the transfected cells expressed MSC markers. Human bone morphogenetic protein-6 (BMP-6) plasmid DNA was delivered using ultrasound in the same animal model, leading to transient expression and secretion of BMP-6 localized to the fracture area. Micro-computed tomography and biomechanical analyses showed that ultrasound-mediated BMP-6 gene delivery led to complete radiographic and functional fracture healing in all animals 6 weeks after treatment, whereas nonunion was evident in control animals. Collectively, these findings demonstrate that ultrasound-mediated gene delivery to endogenous mesenchymal progenitor cells can effectively treat nonhealing bone fractures in large animals, thereby addressing a major orthopedic unmet need and offering new possibilities for clinical translation.

The Effect of Bisphosphonates on the Clinical and Radiographic Outcomes of Distal Radius Fractures in Women

PURPOSE

To compare clinical and radiographic outcomes of distal radius fractures (DRF) treated with nonsurgical management in female postmenopausal patients receiving bisphosphonate (BP) therapy at the time of injury with those not receiving BP therapy.

METHODS

We prospectively enrolled 33 female postmenopausal patients with 35 DRF between December 2010 and January 2014 at 2 Level I tertiary care centers. Eleven patients with 12 DRF were currently receiving BP at the time of injury (BP group) and were compared with 22 controls with 23 DRF (CONT group) who were not receiving BP at the time of injury. All were postmenopausal women with fragility fractures managed nonsurgically. Primary outcomes were radiographic healing measured by the Radius Union Scoring System (RUSS) score and clinical and functional outcomes. Radiographs, range of motion, pinch and grip strength, Patient-Rated Wrist Evaluation scores, and Disability of the Arm, Shoulder, and Hand scores were determined at 6, 9, and 12 weeks and 1 year from time of injury and compared between groups.

RESULTS

The BP and CONT groups were similar in terms of age, comorbidities, and fracture severity. Both groups had progressively improving RUSS scores from the time of injury throughout subsequent evaluation, and all patients achieved radiographic union. Fracture healing was similar in both groups at 6, 9, and 12 weeks after injury. The RUSS scores were slightly better in the CONT group at 1 year. There were no differences in wrist range of motion, pinch, grip, Patient-Rated Wrist Evaluation, or Disability of the Arm, Shoulder, and Hand scores at any time point after injury.

CONCLUSIONS

Patients receiving BP at the time of DRF had clinical outcomes similar to those not receiving antiresorptive treatment. Although there was a small difference in RUSS scores at 1 year after injury, this was not clinically relevant and all fractures united in a similar time frame with no healing complications. These results suggest that BP may be continued throughout nonsurgical management of DRF without detrimental effects on healing or function.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic II.

The compositional and nano-structural basis of fracture healing in healthy and osteoporotic bone

Osteoporosis, a prevalent metabolic bone disorder, predisposes individuals to increased susceptibility to fractures. It is also, somewhat controversially, thought to delay or impair the regenerative response. Using high-resolution Fourier-transform infrared spectroscopy and small/wide-angle X-ray scattering we sought to answer the following questions: Does the molecular composition and the nano-structure in the newly regenerated bone differ between healthy and osteoporotic environments? And how do pharmacological treatments, such as bone morphogenetic protein 7 (BMP-7) alone or synergistically combined with zoledronate (ZA), alter callus composition and nano-structure in such environments? Cumulatively, on the basis of compositional and nano-structural characterizations of newly formed bone in an open-osteotomy rat model, the healing response in untreated healthy and ovariectomy-induced osteoporotic environments was fundamentally the same. However, the BMP-7 induced osteogenic response resulted in greater heterogeneity in the nano-structural crystal dimensions and this effect was more pronounced with osteoporosis. ZA mitigated the effects of the upregulated catabolism induced by both BMP-7 and an osteoporotic bone environment. The findings contribute to our understanding of how the repair processes in healthy and osteoporotic bone differ in both untreated and treated contexts and the data presented represents the most comprehensive study of fracture healing at the nanoscale undertaken to date.

Bone tissue response following local drug delivery of bisphosphonate through titanium oxide nanotube implants in a rabbit model

OBJECTIVES

The objective of this study was to evaluate whether surface chemistry-controlled TiO₂ nanotube structures may serve as a local drug delivery system for zoledronic acid improving implant-bone support.

METHODS

Twenty-four screw-shaped Ti implants with surface chemistry-controlled TiO₂ nanotube structures were prepared and divided into a zoledronic acid-formatted test and a native control group. The implants were inserted into contra-lateral femoral condyles in 12 New Zealand White rabbits. Bone support was evaluated using resonance frequency analysis (RFA) and removal torque (RTQ), as well as histometric analysis following a 3-weeks healing interval.

RESULTS

Zoledronic acid-formatted TiO₂ nanotube test implants showed significantly improved implant stability and osseointegration measured using RFA and RTQ compared with control (p < 0.05), and showed significantly enhanced new bone formation within the root of the threads compared with control (p < 0.05).

CONCLUSIONS

TiO₂ nanotube implants may prove to be a significant delivery system for drugs or biologic agents aimed at supporting local bone formation. Additional study of candidate drugs/agents, optimized dosage and release kinetics is needed prior to evaluation in clinical settings.

Use of a fluorescent probe to monitor the enhanced affinity of rh-BMP-2 to silicated-calcium phosphate synthetic bone graft substitutes under competitive conditions

A comparative investigation was undertaken on 1-2mm sized granules of two forms of synthetic bone graft substitute (SBG) with identical pore structure but varied bulk chemistry, stoichiometric hydroxyapatite (HA) and silicate substituted (0.8wt% Si) hydroxyapatite (SA), to assess the influence of SBG chemistry on the relative affinity of an osteogenic growth factor (GF), recombinant human bone morphogenetic protein-2 (rhBMP-2). A previously described novel fluorescent probe, fluoresceinthioureidoaminocaproic acid (FTCA), was covalently attached to rhBMP-2 to give FTCA-rhBMP-2 and facilitate the quantitative monitoring of GF uptake and release from the two chemistries of SBG. The relative affinity of rhBMP-2 for the HA and SA granules was assessed at a physiologically relevant concentration of 300ngmL^-1 from three (increasingly complex) environments; phosphate buffered saline (PBS), minimum Eagles' medium (MEM) and serum supplemented MEM (SCEM) in order to closely mimic clinical bone repair procedures. The results demonstrated that rhBMP-2 affinity to SBGs was highly sensitive to both SBG chemistry and the composition of the local environment. Under the most physiologically relevant competitive conditions of SCEM, rhBMP-2 showed greater affinity to SA (P<0.05) such that 50% of the rhBMP-2 in solution was adsorbed to the SA granules after only 15min, as compared to 30% adsorbed to the HA granules. Subsequent investigation of the desorption of adsorbed GF from the SBGs demonstrated that a significantly higher percentage of the adsorbed rhBMP-2 was desorbed from HA as compared to SA granules. Together, these observations suggested that at physiologically relevant concentrations and conditions, rhBMP-2 has a greater affinity to silicate-substituted hydroxyapatite as compared to stoichiometric hydroxyapatite, which may in part explain the enhanced osteoconductivity and reported osteoinductivity for silicate-substituted hydroxyapatite based SBGs.

Local bisphosphonate reduces migration and formation of radiolucent lines adjacent to cemented acetabular components

AIMS

Post-operative migration of cemented acetabular components as measured by radiostereometric analysis (RSA) has a strong predictive power for late, aseptic loosening. Also, radiolucent lines predict late loosening. Migration has been reduced by systemic bisphosphonate treatment in randomised trials of hip and knee arthroplasty. Used as a local treatment, a higher local dose of bisphosphonate can be achieved without systemic exposure. We wished to see if this principle could be applied usefully in total hip arthroplasty (THA).

PATIENTS AND METHODS

In this randomised placebo-controlled, double-blinded trial with 60 participants, we compressed gauze soaked in bisphosphonate solution (ibandronate) or saline against the acetabular bone bed immediately before cementing the acetabular component. RSA, classification of radiolucent lines, the Harris Hip Score (HHS) and the Western Ontario McMasters Universities Osteoarthritis Index (WOMAC) were carried out at three-, six-, 12-, and 24-month follow-up.

RESULTS

Migration of the cemented acetabular component relative to the pelvis was reduced by movement almost half in the ibandronate group, when measured as maximum total point or as movement of the femoral head (p = 0.001 and 0.004, respectively). Radiolucent lines after one year were classified as absent, partial or complete, and correlated with treatment (rho 0.37; p = 0.004). Only three of 30 patients in the ibandronate group had complete lines, compared with 13 of 28 in the placebo group (p = 0.002). There were no significant effects on HHS or WOMAC score.

CONCLUSION

Considering the power of RSA to predict loosening of cemented acetabular components, and the likelihood that radiolucent lines indicate risk of loosening, these data suggest that local treatment with a bisphosphonate can reduce the risk of late aseptic loosening. Cite this article: Bone Joint J 2017;99-B:317-24.

Proceedings of the 2016 Santa Fe Bone Symposium: New Concepts in the Management of Osteoporosis and Metabolic Bone Diseases

The Santa Fe Bone Symposium is an annual meeting of healthcare professionals and clinical researchers that details the clinical relevance of advances in knowledge of skeletal diseases. The 17th Santa Fe Bone Symposium was held in Santa Fe, New Mexico, USA, on August 5-6, 2016. The program included plenary lectures, oral presentations by endocrinology fellows, meet-the-professor sessions, and panel discussions, all aimed to provide ample opportunity for interactive discussions among all participants. Symposium topics included recent developments in the translation of basic bone science to patient care, new clinical practice guidelines for postmenopausal osteoporosis, management of patients with disorders of phosphate metabolism, new and emerging treatments for rare bone diseases, strategies to enhance fracture healing, and an update on Bone Health Extension for Community Healthcare Outcomes, using a teleconferencing platform to elevate the level of knowledge of healthcare professionals in underserved communities to deliver best practice care for skeletal diseases. The highlights and important clinical messages of the 2016 Santa Fe Bone Symposium are provided herein by each of the faculty presenters.

Topical bisphosphonate augments fixation of bone-grafted hydroxyapatite coated implants, BMP-2 causes resorption-based decrease in bone

Bone allograft is used in total joint arthroplasties in order to enhance implant fixation. BMPs are known to stimulate new bone formation within allograft, but also known to accelerate graft resorption. Bisphosphonates are strong inhibitor of bone resorption. The aim of this study was to investigate whether the bisphosphonate zoledronate was able to counteract the accelerated graft resorption without interfering with the BMP induced bone formation. In the present study the two drugs alone and in combination were studied in our canine model of impaction bone grafting. We included 10 dogs in this study. Cancellous allograft bone grafts were soaked in either saline or zoledronate solution (0.005mg/mL) and then vehicle or BMP2 (0.15mg rhBMP2) was added. This produced four treatment groups: A) control, B) BMP2, C) zoledronate and D) BMP2+zoledronate. The allograft treated with A, B, C or D was impacted into a circumferential defect of 2.5mm around HA-coated porous Ti implants. Each dog received all four treatment groups with two implants in the distal part of each femur. The group with allograft soaked in zoledronate (C) showed better biomechanical fixation than all other groups (p<0.05). It had less allograft resorption compared to all other groups (p<0.005) without any statistically significant change in new bone formation. The addition of BMP2 to the allograft did not increase new bone formation significantly, but did accelerate allograft resorption. This was also the case where the allograft was treated with BMP2 and zoledronate in combination (D). This caused a decrease in mechanical implant fixation in both these groups compared to the control group, however only statistically significant for the BMP2 group compared to control. The study shows that topical zoledronate can be a valuable tool for augmenting bone grafts when administered optimally. The use of BMP2 in bone grafting procedures seems associated with a high risk of bone resorption and mechanical weakening.

Do osteoporotic fractures constitute a greater recalcitrant challenge for skeletal regeneration? Investigating the efficacy of BMP-7 and zoledronate treatment of diaphyseal fractures in an open fracture osteoporotic rat model

Osteoporotic fractures may pose a challenge for skeletal regeneration. This study investigates if pharmaceutical interventions such as bone morphogenetic protein 7 (BMP-7) alone or in combination with Zoledronate have equivalent efficacy in osteoporotic bone? Our findings suggest they do and that an osteoporotic bone environment may increase sensitivity to BMP-7.

INTRODUCTION

Osteoporosis is thought to contribute to delayed or impaired bone healing. Bone morphogenetic protein 7 (BMP-7) alone or synergistically combined with zoledronate (ZA) has proven effective in augmenting the regenerative response in healthy young male rats. Yet their comparative efficacy in an osteoporotic bone environment is unknown. Our study aimed to answer the following questions using the ovariectomized (OVX) rat model of osteoporosis: Do osteoporotic fractures pose a greater challenge for skeletal regeneration? Are interventions with BMP-7-alone or combined with ZA of equivalent efficacy in osteoporotic bone?

METHODS

Sham operations (n = 33) or ovariectomies (n = 34) were performed in 12-week-old female Sprague-Dawley rats. Mid-diaphyseal open femoral osteotomies were created at 24 weeks of age and the rats allocated to either (i) untreated, (ii) BMP-7-only or (iii) BMP-7 + ZA treatment groups. At 6 weeks post-osteotomy, fracture healing was evaluated by radiography, μCT and 3-point bending mechanical tests.

RESULTS

Cumulatively, radiological, micro-structural and mechanical measures were equivalent in both healthy and osteoporotic environments. A reduced response to BMP-7-alone was observed in healthy rats that may be age/gender- or protocol/fracture-model dependent. Conversely, the BMP-7-only treated OVX group attained 100 % union in addition to significantly increased measures of mineralized bone volume, total callus volume, peak force and absorbed energy relative to untreated OVX fractures.

CONCLUSIONS

Our findings refute the hypothesis that osteoporotic fractures constitute a greater recalcitrant challenge for skeletal regeneration. Furthermore, our results suggest that an oestrogen-deficient environment may in fact cause an increased sensitivity to BMP-7.

Effects of Bisphosphonate Administration on Cleft Bone Graft in a Rat Model

OBJECTIVE

Bone grafts in patients with cleft lip and palate can undergo a significant amount of resorption. The aim of this study was to investigate the effects of bisphosphonates (BPs) on the success of bone grafts in rats.

DESIGN

Thirty-five female 15-week-old Fischer F344 Inbred rats were divided into the following experimental groups, each receiving bone grafts to repair an intraoral CSD: (1) Graft/saline: systemic administration of saline and (2) systemic administration of zoledronic acid immediately following surgery (graft/BP/T0), (3) 1 week postoperatively (graft/BP/T1), and (4) 3 weeks postoperatively (graft/BP/T2). As an additional control, the defect was left empty without bone graft.

MAIN OUTCOME MEASURES

Microcomputed tomography and histologic analyses were performed in addition to evaluation of osteoclasts through tartrate-resistant acid phosphatase staining.

RESULTS

Bone volume fraction (bone volume/tissue volume) for the delayed BP treatment groups (graft/BP/T1 = 45.4% ± 8.8%; graft/BP/T2 = 46.1% ± 12.4%) were significantly greater than that for the graft/saline group (31.0% ± 7.9%) and the graft/BP/T0 (27.6% ± 5.9%) 6 weeks postoperatively (P < .05). Hematoxylin and eosin staining confirmed an evident increase in bone volume and fusion of defect margins with existing palatal bone in the graft/BP/T1 and graft/BP/T2 groups. The graft/BP/T0 group showed the lowest bone volume with signs of acute inflammation.

CONCLUSIONS

Delayed BP administration following cleft bone graft surgery led to significant increase in bone volume and integration compared with saline controls. However, BP injection immediately after the surgery did not enhance bone volume, and rather, may negatively affect bone graft incorporation.

Effects of Teriparatide Compared with Risedronate on Recovery After Pertrochanteric Hip Fracture: Results of a Randomized, Active-Controlled, Double-Blind Clinical Trial at 26 Weeks

BACKGROUND

Osteoporosis drugs might affect fracture-healing. We therefore studied the effects of teriparatide in comparison with risedronate on recovery after pertrochanteric hip fractures.

METHODS

The study was a randomized, multicenter, active-controlled, 78-week trial comparing teriparatide (20 μg/day) with risedronate (35 mg/week) initiated within 2 weeks after fixation of a low-trauma pertrochanteric hip fracture (AO/OTA 31-A1 or 31-A2). The main inclusion criteria were a bone mineral density T-score of ≤-2.0 and 25-OH-vitamin D of ≥9.2 ng/mL. During the first 26 weeks, patients received study medication with oral or injectable placebo plus calcium and vitamin D in a double-blinded fashion. Secondary (Timed Up-and-Go [TUG] test, hip pain, Short Form [SF]-36 health status, and safety) and exploratory (radiographic outcomes and ability to walk) 26-week end points are reported.

RESULTS

Of the 224 patients who were randomized, 171 (86 teriparatide, 85 risedronate) were included in the analysis. The mean age was 77 ± 8 years, 77% were female, and 26% had a prior history of low-trauma fracture. The teriparatide group completed the TUG test in a shorter time at 6, 12, 18, and 26 weeks (differences of -5.7, -4.4, -3.1, and -3.1 seconds, respectively; p = 0.021 for the overall difference). They also reported less pain on a visual analog scale immediately after the TUG test at 12 and 18 weeks (adjusted absolute differences of 10.6 and 11.9 mm, respectively; p < 0.05). There were no significant between-group differences in the SF-36 score, Charnley hip pain score, ability to walk, or use of walking aids during follow-up. Radiographic healing at 6, 12, and 26 weeks, mechanical failure of the implant (teriparatide, 7; risedronate, 8), loss of reduction (teriparatide, 2; risedronate, 4), and nonunion (0 cases) were not significantly different. Mild hypercalcemia and hyperuricemia were more frequent with teriparatide.

CONCLUSIONS

Teriparatide was associated with less pain and a shorter time to complete the TUG test between 6 and 26 weeks compared with risedronate. Other fracture-recovery outcomes were similar. The results should be interpreted with caution as these were secondary end points.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Does the Time of Postoperative Bisphosphonate Administration Affect the Bone Union in Osteoporotic Intertrochanteric Fracture of Femur?

Purpose

This study was designed to investigate the effect of bisphosphonate administration starting time on bone healing and to identify the best administration time following surgical treatment of osteoporotic intertrochanteric fractures.

Materials and Methods

Two hundreds and eighty four patients (284 hips; 52 males, 232 females) who underwent surgery following osteoporotic intertrochanteric fracture from December 2002 to December 2012 were retrospectively analyzed. The average follow-up period was 68.4 months. The patients were divided into three groups according to the time of bisphosphonate administration after operation: 1 week (group A; n=102), 1 month (group B; n=89), and 3 months (group C; n=93). Koval scores and change of Koval scores 1 year after operation were used for clinical evaluation. For radiologic evaluation, the time of callus appearance across the fracture line on sagittal and coronal radiographs and the time to absence of pain during hip motion was judged as the time of bone union.

Results

Koval scores one year after surgery for groups A, B, and C were 2.44, 2.36, and 2.43 (P=0.895), respectively. The mean time of union was 12.4, 11.9, and 12.3 weeks after operation in the three groups (P=0.883), respectively. There were zero cases of nonunion. There were 3, 5, and 7 cases of fixative displacement in the three groups, respectively, but the distribution showed no significant difference (P>0.472).

Conclusion

The initiating time of bisphosphonate administration following surgery does not affect the clinical outcomes in patients with osteoporotic intertrochanteric fracture.

A Biphasic Calcium Sulphate/Hydroxyapatite Carrier Containing Bone Morphogenic Protein-2 and Zoledronic Acid Generates Bone

In orthopedic surgery, large amount of diseased or injured bone routinely needs to be replaced. Autografts are mainly used but their availability is limited. Commercially available bone substitutes allow bone ingrowth but lack the capacity to induce bone formation. Thus, off-the-shelf osteoinductive bone substitutes that can replace bone grafts are required. We tested the carrier properties of a biphasic, calcium sulphate and hydroxyapatite ceramic material, containing a combination of recombinant human bone morphogenic protein-2 (rhBMP-2) to induce bone, and zoledronic acid (ZA) to delay early resorption. In-vitro, the biphasic material released 90% of rhBMP-2 and 10% of ZA in the first week. No major changes were found in the surface structure using scanning electron microscopy (SEM) or in the mechanical properties after adding rhBMP-2 or ZA. In-vivo bone formation was studied in an abdominal muscle pouch model in rats (n = 6/group). The mineralized volume was significantly higher when the biphasic material was combined with both rhBMP-2 and ZA (21.4 ± 5.5 mm³) as compared to rhBMP-2 alone (10.9 ± 2.1 mm³) when analyzed using micro computed tomography (μ-CT) (p < 0.01). In the clinical setting, the biphasic material combined with both rhBMP-2 and ZA can potentially regenerate large volumes of bone.

Combination therapy with BMP-2 and a systemic RANKL inhibitor enhances bone healing in a mouse critical-sized femoral defect

Recombinant human BMP-2 (rhBMP-2) is a potent osteoinductive agent, but has been associated not only with bone formation, but also osteoclastogenesis and bone resorption. Osteoprotegerin (OPG) is a RANKL inhibitor that blocks differentiation and function of osteoclasts. We hypothesized that the combination of local BMP-2 (recombinant protein or a product of gene therapy) plus systemic OPG-Fc is more effective than BMP-2 alone in promoting bone repair. To test this hypothesis we used a mouse critical-sized femoral defect model. Col2.3eGFP (osteoblastic marker) male mice were treated with rhBMP-2 (group I), rhBMP-2 and systemic OPG (group II), rhBMP-2 and delayed administration of OPG (group III), mouse BM cells transduced with a lentiviral vector containing the BMP-2 gene (LV-BMP-2; group IV), LV-BMP-2 and systemic OPG (group V), a carrier alone (group VI) and administration of OPG alone (group VII). All bone defects treated with BMP-2 (alone or combined with OPG) healed, whereas minimal bone formation was noted in animals treated with the carrier alone or OPG alone. MicroCT analysis showed that bone volume (BV) in rhBMP-2+OPG and LV-BMP-2+OPG groups was significantly higher compared to rhBMP-2 alone (p<0.01) and LV-BMP-2 alone (p<0.001). Similar results were observed in histomorphometry, with rhBMP-2 alone defects exhibiting significantly lower bone area (B.Ar) compared to rhBMP-2+OPG defects (p<0.005) and LV-BMP-2 defects having a significantly lower B.Ar compared to all BMP-2+OPG treated groups (p≤0.01). TRAP staining demonstrated a major osteoclast response in the groups that did not receive OPG (rhBMP-2, LV-BMP-2 and sponge alone) beginning as early as 7days post-operatively. In conclusion, we demonstrated that locally delivered BMP-2 (recombinant protein or gene therapy) in combination with systemically administered OPG improved bone healing compared to BMP-2 alone in a mouse critical-sized bone defect. These data indicate that osteoclasts can diminish healing responses to BMP-2 and that RANKL inhibition may thus accentuate BMP-2 efficacy.

Effect of zoledronic acid on spinal fusion outcomes in an ovariectomized rat model of osteoporosis

To evaluate the effect of zoledronic acid (ZA) on spinal fusion in ovariectomized (OVX) rats. Female SD rats (n = 50) were OVX or sham-operated and randomized into five groups: Sham, OVX control, ZOL-20 (20 µg/kg), ZOL-100 (100 µg/kg), and ZOL-500 (500 µg/kg). Eight weeks after OVX, bilateral lumbar spinal fusion was performed using autologous iliac bone with ZA or saline according to the grouping. The lumbar spines were harvested at 8 weeks and subjected to radiographic, manual palpation, micro-computed tomographic (micro-CT), and histological analysis. The manual palpation result differed significantly only between the ZOL-500 (fused: partially fused: not fused, 9:0:0) and OVX control (4:2:3) (p < 0.05). The radiographic scales were also differed significantly only between these two groups. According to the micro-CT results, the bone volume fraction (BV/TV) were significantly higher in all ZA-treated groups (54.2%, 65.9%, and 73.6%) than OVX control (43.7%) (p < 0.01). At clinical dose or lower, ZA didn't alter the spinal fusion, but a higher dose increased the spinal fusion rate significantly. This study suggests ZA may have a positive effect on spinal fusion in the presence of osteoporosis, and spinal fusion surgery outcome is not likely to be altered by ZA at clinical dose.

Local application of ibandronate/gelatin sponge improves osteotomy healing in rabbits

Delayed healing or non-union of skeletal fractures are common clinical complications. Ibandronate is a highly potent anti-catabolic reagent used for treatment of osteopenia and fracture prevention. We hypothesized that local application of ibandronate after fracture fixation may improve and sustain callus formation and therefore prevent delayed healing or non-union. This study tested the effect of local application of an ibandronate/gelatin sponge composite on osteotomy healing. A right-side distal-femoral osteotomy was created surgically, with fixation using a k-wire, in forty adult male rabbits. The animals were divided into four groups of ten animals and treated by: (i) intravenous injection of normal saline (Control); (ii) local implantation of absorbable gelatin sponge (GS); (iii) local implantation of absorbable GS containing ibandronate (IB+GS), and (iv) intravenous injection of ibandronate (IB i.v.). At two and four weeks the affected femora were harvested for X-ray photography, computed tomography (CT), biomechanical testing and histopathology. At both time-points the results showed that the calluses in both the ibandronate-treated groups, but especially in the IB+GS group, were significantly larger than in the control and GS groups. At four weeks the cross sectional area (CSA) and mechanical test results of ultimate load and energy in the IB+GS group were significantly higher than in other groups. Histological procedures showed a significant reduction in osteoclast numbers in the IB+GS and IB i.v. groups at day 14. The results indicate that local application of an ibandronate/gelatin sponge biomaterial improved early osteotomy healing after surgical fixation and suggest that such treatment may be a valuable local therapy to enhance fracture repair and potentially prevent delayed or non-union.

The masquelet induced membrane technique with BMP and a synthetic scaffold can heal a rat femoral critical size defect

Long bone defects can be managed by the induced membrane technique together with autologous bone graft. However, graft harvest is associated with donor site morbidity. This study investigates if a tricalcium phosphate hydroxyapatite scaffold can be used alone or in combination with bone active drugs to improve healing. Sprague Dawley rats (n = 40) were randomized into four groups. (A) scaffold, (B) BMP-7, (C) BMP-7 + scaffold, and (D) BMP-7 + scaffold + systemic bisphosphonate at 2 weeks. Locked femoral nailing was followed by 6 mm segment removal and implantation of an epoxy spacer. At 4 weeks, the spacers were removed and the defects grafted. Eleven weeks later, the bones were explanted for evaluation with radiography, manual assessment, micro-CT, histology, and Fourier Transform Infrared spectroscopy (FTIR). Isolated scaffolds (A) did not heal any defects, whereas the other treatments led to healing in 7/10 (B), 10/10 (C), and 9/10 (D) rats. Group D had greater volume of highly mineralized bone (p < 0.01) and higher bone volume fraction (p < 0.01) compared to all other groups. A synthetic scaffold + BMP-7 combined with a bisphosphonate improved the callus properties in a rat femoral critical size defect, compared to both BMP-7 and scaffold alone or the two combined.