Optimal timing of a single dose of zoledronic acid to increase strength in rat fracture repair

Impact of osteoporosis and osteoporosis medications on fracture healing: a narrative review

Antiresorptive medications do not negatively affect fracture healing in humans. Teriparatide may decrease time to fracture healing. Romosozumab has not shown a beneficial effect on human fracture healing.

BACKGROUND

Fracture healing is a complex process. Uncertainty exists over the influence of osteoporosis and the medications used to treat it on fracture healing.

METHODS

Narrative review authored by the members of the Fracture Working Group of the Committee of Scientific Advisors of the International Osteoporosis Foundation (IOF), on behalf of the IOF and the Société Internationale de Chirurgie Orthopédique et de Traumatologie (SICOT).

RESULTS

Fracture healing is a multistep process. Most fractures heal through a combination of intramembranous and endochondral ossification. Radiographic imaging is important for evaluating fracture healing and for detecting delayed or non-union. The presence of callus formation, bridging trabeculae, and a decrease in the size of the fracture line over time are indicative of healing. Imaging must be combined with clinical parameters and patient-reported outcomes. Animal data support a negative effect of osteoporosis on fracture healing; however, clinical data do not appear to corroborate with this. Evidence does not support a delay in the initiation of antiresorptive therapy following acute fragility fractures. There is no reason for suspension of osteoporosis medication at the time of fracture if the person is already on treatment. Teriparatide treatment may shorten fracture healing time at certain sites such as distal radius; however, it does not prevent non-union or influence union rate. The positive effect on fracture healing that romosozumab has demonstrated in animals has not been observed in humans.

CONCLUSION

Overall, there appears to be no deleterious effect of osteoporosis medications on fracture healing. The benefit of treating osteoporosis and the urgent necessity to mitigate imminent refracture risk after a fracture should be given prime consideration. It is imperative that new radiological and biological markers of fracture healing be identified. It is also important to synthesize clinical and basic science methodologies to assess fracture healing, so that a convergence of the two frameworks can be achieved.

Bone union-promoting effect of romosozumab in an ovariectomized rat posterolateral lumbar fusion model

Spinal fixation surgery has been increasingly performed in patients with osteoporosis. Romosozumab, a drug that was introduced in Japan recently, is known to possibly promote bone healing. However, few studies have reported the therapeutic effects of romosozumab in clinical practice in Japan. Therefore, here, we investigated the effects of romosozumab dosage on bone fusion promotion using an ovariectomized rat spinal fusion model. Eight-week-old female Sprague-Dawley rats were matched by body weight and divided into three groups: 1.0 romosozumab (R) group (Evenity®, 25 mg/kg), 1/10R group (Evenity®, 2.5 mg/kg), and control (C) group (saline). Subcutaneous injections were administered twice a week for 8 weeks postoperatively. Computed tomography scans were performed every 2 weeks from the time of surgery till 8 weeks postoperatively. The mean fusion rates in terms of volume were significantly higher in the R groups [1/10R, 1.0R] than in the C group from 4 weeks postoperatively. The rate of increase was significantly higher in the 1.0R group from 4 weeks postoperatively and in the 1/10R group from 6 weeks postoperatively, than in the C group. The proportion of trabecular bone area was approximately 1.5 times higher in the R groups than in the C group. No significant differences were observed between the R groups. Our results suggest that romosozumab stimulates bone growth at the graft site, and similar effects were achieved at 1/10 of the standard dosage.

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

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

Influence of zoledronic acid and low-intensity laser on collagen fibers during the bone repair process

PURPOSE

To evaluate collagen fibers during the bone repair process in critical defects created in the tibias of rats, treated with zoledronic acid (AZ) associated with low-level laser therapy (LLLT).

METHODS

Ten rats were distributed according to treatment: group 1) saline solution; group 2) LLLT; group 3) AZ; group 4) AZ and LLLT. AZ was administered at the dose of 0.035 mg/kg at fortnightly intervals over eight weeks. Next, 2-mm bone defects were created in the tibias of all animals. The bone defects in groups 2 and 4 were irradiated LLLT in the immediate postoperative period. After periods 14 and 28 of application, the animals were euthanized, and birefringence analysis was performed.

RESULTS

Approximately 90% of the total area was occupied by collagen fibers within the red color spectrum, this area being statistically larger in relation to the area occupied by collagen fibers within the green and yellow spectrum, in the four groups. Over the 14-day period, there was no statistically significant difference between the groups. In the 28-day period, group 2 (14.02 ± 15.9%) was superior in quantifying green birefringent fibers compared to group 1 (3.06 ± 3.24%), with p = 0.009.

CONCLUSIONS

LLLT associated with ZA is effective in stimulating the neoformation of collagen fibers. The LLLT group without the association with ZA showed a greater amount of immature and less organized matrix over a period of 28 days.

Systemically administered zoledronic acid activates locally implanted synthetic hydroxyapatite particles enhancing peri-implant bone formation: A regenerative medicine approach to improve fracture fixation

Fracture fixation in an ageing population is challenging and fixation failure increases mortality and societal costs. We report a novel fracture fixation treatment by applying a hydroxyapatite (HA) based biomaterial at the bone-implant interface and biologically activating the biomaterial by systemic administration of a bisphosphonate (zoledronic acid, ZA). We first used an animal model of implant integration and applied a calcium sulphate (CaS)/HA biomaterial around a metallic screw in the tibia of osteoporotic rats. Using systemic ZA administration at 2-weeks post-surgery, we demonstrated that the implant surrounded by HA particles showed significantly higher peri‑implant bone formation compared to the unaugmented implants at 6-weeks. We then evaluated the optimal timing (day 1, 3, 7 and 14) of ZA administration to achieve a robust effect on peri‑implant bone formation. Using fluorescent ZA, we demonstrated that the uptake of ZA in the CaS/HA material was the highest at 3- and 7-days post-implantation and the uptake kinetics had a profound effect on the eventual peri‑implant bone formation. We furthered our concept in a feasibility study on trochanteric fracture patients randomized to either CaS/HA augmentation or no augmentation followed by systemic ZA treatment. Radiographically, the CaS/HA group showed signs of increased peri‑implant bone formation compared with the controls. Finally, apart from HA, we demonstrated that the concept of biologically activating a ceramic material by ZA could also be applied to β-tricalcium phosphate. This novel approach for fracture treatment that enhances immediate and long-term fracture fixation in osteoporotic bone could potentially reduce reoperations, morbidity and mortality. STATEMENT OF SIGNIFICANCE: • Fracture fixation in an ageing population is challenging. Biomaterial-based augmentation of fracture fixation devices has been attempted but lack of satisfactory biological response limits their widespread use. • We report the biological activation of locally implanted microparticulate hydroxyapatite (HA) particles placed around an implant by systemic administration of the bisphosphonate zoledronic acid (ZA). The biological activation of HA by ZA enhances peri‑implant bone formation. •Timing of ZA administration after HA implantation is critical for optimal ZA uptake and consequently determines the extent of peri‑implant bone formation. • We translate the developed concept from small animal models of implant integration to a proof-of-concept clinical study on osteoporotic trochanteric fracture patients. • ZA based biological activation can also be applied to other calcium phosphate biomaterials.

Post-Fracture Care Program: Pharmacological Treatment of Osteoporosis in Older Adults with Fragility Fractures

PURPOSE OF REVIEW

To present and discuss the recently published scientific evidence on the approach, mode of action, and timing of osteoporosis therapy initiation after fragility fractures.

RECENT FINDINGS

A comprehensive management approach is required to reduce mortality and morbidity associated with fragility fractures. This will help to reduce the risk of missing the diagnosis of osteoporosis as the underlying disorder while at the same time promoting the timely treatment of osteoporosis. The target is to minimize the incidence of post-traumatic disability and to reduce the imminent fracture risk. This article will present a Bone-Care algorithm for the diagnosis and management of fragility fractures in patients presenting for trauma surgery. This algorithm has been developed based on recently published national as well as international guidelines for implementation in standard clinical practice. International figures revealed that only a small proportion of those patients at high risk of sustaining a fragility fracture receive osteoporosis therapy. Based on the best currently available evidence, it is safe to start osteoporosis therapy in the acute post-fracture period (the optimal therapeutic window of romosozumab is the late endochondral phase/throughout bone remodeling). The right Bone-Care pathway ensures the delivery of a comprehensive management approach that meets the global call to action. All parameters including risk, benefit, compliance, and cost should be considered on an individual base for all kinds of therapy.

No Increased Risk of Nonunion with Bisphosphonate Use in a Medicare Claims Cohort Following Operatively Treated Long-Bone Fractures

BACKGROUND

The diagnosis of a fragility fracture represents an important intervention event for the initiation of medical osteoporosis treatments. However, it is unclear if osteoporosis medications increase the risk of nonunion if administered in the setting of acute fracture. The purpose of the present study was to investigate whether bisphosphonates or selective estrogen receptor modulators/hormone replacement therapy (SERM/HRT) are associated with nonunion following fracture in a Medicare population.

METHODS

A retrospective analysis of Medicare claims from 2016 to 2019 was performed to identify patients ≥65 years of age who had a surgically treated long-bone fracture as identified with Current Procedural Terminology (CPT) codes and International Classification of Diseases, 10th Revision (ICD-10) codes. Successive claims were linked for each beneficiary through 1 year following the fracture to determine fracture union status. Multivariable logistic regression models were specified to identify the association between medications and fracture union status while controlling for age, sex, race, Charlson Comorbidity Index (CCI), and fracture type.

RESULTS

Of the 111,343 included fractures, 10,452 (9.4%) were associated with a diagnosis of nonunion within 1 year. The nonunion group was younger (79.8 ± 8.3 versus 80.6 ± 8.4 years; p < 0.001), more likely to be White (92.4% versus 90.9%; p < 0.001), and more likely to have a CCI of ≥2 (50.9% versus 49.4%; p < 0.001). Bisphosphonate use was more common in the nonunion group (12.2% versus 11.4%; p = 0.017). When controlling for race, age, sex, and CCI, neither bisphosphonates (OR, 1.06 [95% CI, 0.99 to 1.12]; p = 0.101) nor SERM/HRT (OR, 1.13 [0.93 to 1.36]; p = 0.218) were associated with nonunion. Bisphosphonate use within 90 days post-fracture was not significantly associated with nonunion (OR, 0.94 [95% CI, 0.86 to 1.03]; p = 0.175), and the timing of medication administration did not influence fracture union status.

CONCLUSIONS

The rate of nonunion after operatively treated long-bone fractures was 9.4%. In this cohort, use of a bisphosphonate or SERM/HRT was not associated with fracture union status at 1 year. Orthopaedic surgeons should not withhold or delay initiating medical therapies for osteoporosis in the setting of acute fracture out of concern for nonunion.

LEVEL OF EVIDENCE

Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Zoledronic Acid Does Not Retard Bone Union: A Randomized Controlled Trial in Fragility Intertrochanteric Femur Fractures

BACKGROUND

Fragility hip fracture is a leading cause of death in the elderly and is common in postmenopausal women and elderly people. In the treatment of osteoporosis, bisphosphonates (BPs) are often considered first-line medications. Zoledronic acid is the most potent and long-acting BP in clinical use and is administered as an intravenous infusion. In the context of acute fractures, the use of BPs has been controversial due to conflicting reports of their positive and negative effects on fracture healing. The purpose of this study was to determine the effect of zoledronic acid on fracture healing in intertrochanteric (IT) fragility fractures.

METHODS

The study was conducted in a tertiary healthcare center after receiving scientific and ethical approval. The study included 136 patients of either gender over the age of 50 who presented with an IT femur fracture after minor trauma between November 2020 and November 2022. The total number of patients had been classified into two groups, and grouping involved random sampling: Group T (test group, n = 68; zoledronic acid injections were given on postoperative day 3) and Group C (control group, n = 68; interventions were given after fracture healing). Patients were evaluated using the Radiographic Union Score for Hip (RUSH) and Singh Index for radiological outcomes and the Harris Hip Score (HHS) for functional outcomes. The patients were followed for six months.

RESULTS

The overall mean age was 73.25 years; in Group T, it was 72.5 ± 11.9 years, and in Group C, it was 73.7 ± 11.8 years. Of 136 patients, 69 (51%) were males and 67 (49%) were females. The average fracture healing time in Group T was 12.2 ± 3.6 weeks, while it was 13.0 ± 2.8 weeks in Group C. Functional outcomes, including HHS, were found to be better in Group T than in Group C (p < 0.005). No significant difference was observed between the two groups with respect to the radiological union, the RUSH score, or Singh Index, implying no negative effect of zoledronic acid.

CONCLUSIONS

This study demonstrates that postoperative intravenous zoledronic acid therapy does not retard fracture healing. Osteoporosis management is frequently neglected because of a surgeon's fear of ZOL retarding fracture healing and a lack of awareness among patients, resulting in low compliance. Thus, opportunistic administration of zoledronic acid postoperatively can be beneficial and will increase compliance for osteoporosis management and fracture prevention to 100%.

Management of Osteoporosis Medication after Osteoporotic Fracture

The aim of this study was to provide helpful information for use in selection of an appropriate medication after osteoporotic fractures through conduct of a literature review. In addition, a review of the recommendations of several societies for prevention of subsequent fractures was performed and the appropriate choice of medication for treatment of atypical femur fractures was examined. Clinical perspective was obtained and an updated search of literature was conducted across PubMed and MEDLINE and relevant articles were selected. The articles were selected manually according to relevance, and the references for identified articles and reviews were also evaluated for relevance. The following areas are reviewed: Commonly prescribed osteoporosis medications: BPs (bisphosphonates), denosumab, and SERMs (selective estrogen receptor modulators) in antiresorptive medications and recombinant human parathyroid hormone teriparatide, recently approved Romosuzumab in anabolic agents, clinical practice guidelines for the management of osteoporosis, osteoporotic fracture, and atypical femur fracture. Most medications for treatment of osteoporosis do not delay fracture healing and the positive effect of teriparatide on fracture healing has been confirmed. In cases where an osteoporotic fracture is diagnosed, risk assessment should be performed for selection of very high-risk patients in order to prevent subsequent fractures, and administration of anabolic agents is recommended.

Bone union-promoting effect of romosozumab in a rat posterolateral lumbar fusion model

This study investigated the effect of romosozumab on bone union in a rat posterolateral lumbar fixation model. Posterolateral lumbar fixation was performed on 8-week-old male Sprague Dawley rats (n = 20). For bone grafting, autogenous bone (40 mg) was harvested from the spinous processes of the 10th thoracic vertebra until the 2nd lumbar vertebra and implanted between the intervertebral joints and transverse processes of the 4th and 5th lumbar vertebrae on both sides. Rats were matched by body weight and equally divided into two groups: R group (Evenity®, 25 mg/kg) and control (C) group (saline). Subcutaneous injections were administered twice a week until 8 weeks after surgery. Computed tomography was performed at surgery and week 8 after surgery. The area and percentage of bone trabeculae in the total area of bone fusion were calculated. Statistical analysis was performed using an unpaired t test (p < 0.05). We found that the R group rats had significantly higher mean bone union rate and volume than did the C group rats at all time courses starting week 4 after surgery. The R group had significantly higher increase rates than did the C group at weeks 4 and 6 after surgery. The percentage of bone trabeculae area in the R group was approximately 1.7 times larger than that in the C group. Thus, we demonstrated that romosozumab administration has stimulatory effects on bony outgrowth at bone graft sites. We attribute this to the modeling effect of romosozumab.

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.

Effects of bisphosphonates on appendicular fracture repair in rodents

The balance between osteoclastic bone resorption and osteoblastic bone formation is ultimately responsible for maintaining a structural and functional skeleton. Despite their strength, bones do break and the main cause of fractures are trauma and decreased bone mineral density as a result of aging and/or pathology that weakens the bone's microarchitecture and subsequently, its material properties. Osteoporosis is a disease marked by increased osteoclast activity and decreased osteoblastic activity tipping the remodeling balance in favor of bone resorption and can be caused by aging, glucocorticoids, disuse and estrogen-deficiency. Ultimately, this leads to brittle and weaker bones which become more prone to trauma or stress-induced fractures. The current treatment for preventing and treating osteoporotic fractures is the use of antiresorptive drugs such as bisphosphonates (BPs) and denosumab, but unfortunately, their long-term use, especially with alendronate and ibandronate, has been associated with increased risk of atypical femoral fractures (AFFs); femoral diaphyseal fractures distal to the lesser trochanter but proximal to the supracondylar flare. The purpose of this review is to examine the information that exists in the literature examining the effects of BPs on fracture repair of long bones in rodent (rat and mouse) models. The focus on rodents stems from the scientific community's unresolved need to develop small animal models to examine the molecular, cellular, tissue and biomechanical mechanisms responsible for the development of AFFs and how best they can be treated.

Muscle-Specific Micro-Ribonucleic Acids miR-1-3p, miR-133a-3p, and miR-133b Reflect Muscle Regeneration After Single-Dose Zoledronic Acid Following Rotator Cuff Repair in a Rodent Chronic Defect Model

BACKGROUND

Zoledronic acid improves bone microarchitecture and biomechanical properties after chronic rotator cuff repair (RCR) in rats. Besides the positive effects of zoledronic acid on bone mineral density and bone microarchitecture, bisphosphonates have positive effects on skeletal muscle function.

PURPOSES/HYPOTHESIS

The purposes of this study were to (1) longitudinally evaluate circulating bone- and muscle-specific serum micro-ribonucleic acids (miRNAs) and (2) investigate supraspinatus muscle tissue after tenotomy and delayed RCR in a rat model. It was hypothesized that zoledronic acid would improve muscle regeneration after chronic RCR in rats.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 34 male Sprague-Dawley rats underwent unilateral (left) supraspinatus tenotomy (time point 1) with delayed transosseous RCR after 3 weeks (time point 2). All rats were sacrificed 8 weeks after RCR (time point 3). Animals were randomly assigned to 2 groups. One day after RCR, the control group was given 1 mL of subcutaneous saline solution, and the intervention group was treated with a subcutaneous single-dose of 100 µg/kg body weight of zoledronic acid. All 34 study animals underwent miRNA analysis at all 3 time points. In 4 animals of each group, histological analyses as well as gene expression analyses were conducted.

RESULTS

Circulating miRNAs showed significantly different expressions between both study groups. In the control group, a significant downregulation was observed for muscle-specific miR-1-3p (P = .004), miR-133a-3p (P < .001), and miR-133b (P < .001). Histological analyses showed significantly higher rates of regenerating myofibers on the operated side (left) of both study groups compared with the nonoperated side (right; P = .002). On the nonoperated side, significantly higher rates of regenerating myofibers were observed in the intervention group compared with the control group (P = .031). The myofiber cross-sectional area revealed significantly smaller myofibers on both sides within the intervention group compared with both sides of the control group (P < .001). Within the intervention group, significantly higher expression levels of muscle development/regeneration marker genes embryonal Myosin heavy chain (P = .017) and neonatal Myosin heavy chain (P = .016) were observed on the nonoperated side compared with the operated side.

CONCLUSION

An adjuvant single-dose of zoledronic acid after RCR in a chronic defect model in rats led to significant differences in bone- and muscle-specific miRNA levels. Therefore, miR-1-3p, miR-133a-3p, and miR-133b might be used as biomarkers for muscle regeneration after RCR.

CLINICAL RELEVANCE

Adjuvant treatment with zoledronic acid may improve muscle regeneration after chronic RCR in humans, thus counteracting fatty muscle infiltration and atrophy.

Determining the pharmacologic window of bisphosphonates that mitigates severe injury-induced osteoporosis and muscle calcification, while preserving fracture repair

Following severe injury, biomineralization is disrupted and limited therapeutic options exist to correct these pathologic changes. This study utilized a clinically relevant murine model of polytrauma including a severe injury with concomitant musculoskeletal injuries to identify when bisphosphonate administration can prevent the paradoxical decrease of biomineralization in bone and increased biomineralization in soft tissues, yet not interfere with musculoskeletal repair.

INTRODUCTION

Systemic and intrinsic mechanisms in bone and soft tissues help promote biomineralization to the skeleton, while preventing it in soft tissues. However, severe injury can disrupt this homeostatic biomineralization tropism, leading to adverse patient outcomes due to a paradoxical decrease of biomineralization in bone and increased biomineralization in soft tissues. There remains a need for therapeutics that restore the natural tropism of biomineralization in severely injured patients. Bisphosphonates can elicit potent effects on biomineralization, though with variable impact on musculoskeletal repair. Thus, a critical clinical question remains as to the optimal time to initiate bisphosphonate therapy in patients following a polytrauma, in which bone and muscle are injured in combination with a severe injury, such as a burn.

METHODS

To test the hypothesis that the dichotomous effects of bisphosphonates are dependent upon the time of administration relative to the ongoing biomineralization in reparative bone and soft tissues, this study utilized murine models of isolated injury or polytrauma with a severe injury, in conjunction with sensitive, longitudinal measure of musculoskeletal repair.

RESULTS

This study demonstrated that if administered at the time of injury, bisphosphonates prevented severe injury-induced bone loss and soft tissue calcification, but did not interfere with bone repair or remodeling. However, if administered between 7 and 21 days post-injury, bisphosphonates temporally and spatially localized to sites of active biomineralization, leading to impaired fracture callus remodeling and permanence of soft tissue calcification.

CONCLUSION

There is a specific pharmacologic window following polytrauma that bisphosphonates can prevent the consequences of dysregulated biomineralization, yet not impair musculoskeletal regeneration.

Timing of osteoporosis therapies following fracture: the current status

In most patients, osteoporosis is diagnosed only after the occurrence of the first fragility fracture. It is of utmost importance to start osteoporosis medications immediately in these patients to prevent future fractures and also to reduce associated mortality and morbidity. There remains a hesitancy over initiating osteoporotic medications, specifically for antiresorptive agents like bisphosphonates following an acute fracture due to concern over their effect on fracture healing. The purpose of this review is to study the effect of the timing of initiation of different osteoporosis medications on healing after an acute fracture. Most of the human studies, including randomized control trials (RCTs), did not find any significant negative effect on fracture healing with early use of bisphosphonate after an acute fracture. Anabolic agents like teriparatide have shown either neutral or beneficial effects on fracture healing and thus can be started very early following any osteoporotic fracture. Although human studies on the early use of other osteoporosis medications like denosumab or strontium ranelate are very sparse in the literature, none of these medications have shown any evidence of delay in fracture healing. To summarize, among the commonly used anti-osteoporosis agents, both bisphosphonates and teriparatide are safe to be initiated in the early acute post-fracture period. Moreover, teriparatide has shown some evidence in favor of reducing fracture healing time.

Long-term pretreatment with alendronate inhibits calvarial defect healing in an osteoporotic rat model

INTRODUCTION

This study aimed to observe the effects of long-term alendronate pretreatment on the healing of osteoporotic calvarial defects, and further investigate the effect of alendronate combined with once-weekly parathyroid hormone following 12 weeks of alendronate treatment in ovariectomized rats.

MATERIALS AND METHODS

Thirty 3-month-old female rats were ovariectomized, and 24 rats received alendronate for 12 weeks. Then, a critical defect was created in the calvaria of all animals. Immediately after osteotomy, the animals received one of five treatments for 8 weeks: (1) continuation of vehicle (group E), (2) alendronate followed by vehicle (group A), (3) continuation of alendronate (group B), (4) alendronate followed by once-weekly parathyroid hormone alone (group C), or (5) continuation of alendronate combined with once-weekly parathyroid hormone (group D). Calvarial defect healing was assessed using dual-energy X-ray absorptiometry, micro-computed tomography, histology, and sequential fluorescence labeling.

RESULTS

Group E showed a significantly higher volume of newly formed bone than groups A, B, C, and D. Evidence of new dense bone formation in group E was observed histologically. In addition, the immunohistochemical expression of runt-related transcription factor 2 was increased in group E but inhibited in groups A, B, C, and D. Sequential immunofluorescence also showed inhibited mineral apposition in groups A, B, C, and D compared with group E.

CONCLUSION

The present study shows that long-term pretreatment with alendronate inhibited calvarial defect healing in osteoporotic rats, and this effect could not be reversed by stopping alendronate, switching to parathyroid hormone, or combining with once-weekly parathyroid hormone.

Once-weekly parathyroid hormone combined with ongoing long-term alendronate treatment promotes osteoporotic fracture healing in ovariectomized rats

This study examined the effect of once-weekly parathyroid hormone (PTH) combined with alendronate upon osteoporotic fracture healing after long-term alendronate anti-osteoporosis therapy. Seventy-six 12-week-old female Sprague-Dawley rats were either sham operated or bilaterally ovariectomized (OVX). Following confirmation of osteoporosis 3 months after OVX, the remaining 64 animals received alendronate therapy. After 3 months of alendronate treatment, all rats underwent unilateral transverse tibial osteotomy. Animals were immediately randomly assigned to one of four groups: (1) alendronate followed by vehicle (ALN-VEH), (2) continuation of alendronate (ALN-ALN), (3) alendronate followed by once-weekly PTH alone (ALN-PTH), (4) continuation of alendronate combined with once-weekly PTH (ALN-ALN + PTH) until collection at 4 or 8 weeks after osteotomy. The fractured tibia was assessed using x-ray, dual-energy x-ray absorptiometry, microcomputed tomography, biomechanical testing, histology, and sequential fluorescence labeling. The ALN-ALN + PTH treatment significantly increased total callus volume, mineralized callus volume, mineralized callus volume/total callus volume, and biomechanical strength of the callus relative to ALN-VEH and ALN-PTH treatments at both 4 and 8 weeks and produced more mature trabecular bone compared with ALN-ALN treatment at 8 weeks. RANKL/osteoprotegerin (OPG) are osteoclastogenesis markers, while cluster of differentiation 31 (CD31) is an important marker of angiogenesis. Qualitative immunohistochemical analysis revealed that CD31 and OPG expression was was strong after ALN-ALN + PTH compared with ALN-ALN treatment, whereas RANKL expression was weak after ALN-ALN + PTH versus ALN-PTH treatment. Our study showed that once-weekly PTH combined with alendronate was beneficial in promoting the healing of fractures acquired after long-term alendronate therapy in OVX-induced osteoporotic rats.

Current concepts in the management of bisphosphonate associated atypical femoral fractures

Bisphosphonates are a class of drugs used as the mainstay of treatment for osteoporosis. Bisphosphonates function by binding to hydroxyapatite, and subsequently targeting osteoclasts by altering their ability to resorb and remodel bone. Whilst aiming to reduce the risk of fragility fractures, bisphosphonates have been associated with atypical insufficiency fractures, specifically in the femur. Atypical femoral fractures occur distal to the lesser trochanter, until the supracondylar flare. There are a number of the differing clinical and radiological features between atypical femoral fractures and osteoporotic femoral fractures, indicating that there is a distinct difference in the respective underlying pathophysiology. At the point of presentation of an atypical femoral fracture, bisphosphonate should be discontinued. This is due to the proposed inhibition of osteoclasts and apoptosis, resulting in impaired callus healing. Conservative management consists primarily of cessation of bisphosphonate therapy and partial weightbearing activity. Nutritional deficiencies should be investigated and appropriately corrected, most notably dietary calcium and vitamin D. Currently there is no established treatment guidelines for either complete or incomplete fractures. There is agreement in the literature that nonoperative management of bisphosphonate-associated femoral fractures conveys poor outcomes. Currently, the favoured methods of surgical fixation are cephalomedullary nailing and plate fixation. Newer techniques advocate the use of both modalities as it gives the plate advantage of best reducing the fracture and compressing the lateral cortex, with the support of the intramedullary nail to stabilise an atypical fracture with increased ability to load-share, and a reduced bending moment across the fracture site. The evidence suggests that cephalomedullary nailing of the fracture has lower revision rates. However, it is important to appreciate that the anatomical location and patient factors may not always allow for this. Although causation between bisphosphonates and atypical fractures is yet to be demonstrated, there is a growing evidence base to suggest a higher incidence to atypical femoral fractures in patients who take bisphosphonates. As we encounter a growing co-morbid elderly population, the prevalence of this fracture-type will likely increase. Therefore, it is imperative clinicians continue to be attentive of atypical femoral fractures and treat them effectively.

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.

Comparison of Vascular Morphometry in Jawbones and Long Bones: Micro-CT Study in a Rat Model Treated with Zoledronic Acid

The study was aimed at investigating the effect of zoledronic acid on vascular morphometry in jawbones and long bones on a rat model. Twenty-four skeletal mature Sprague-Dawley female rats were administered oncologic dose of zoledronic acid (ZA) or normal saline for 4 weeks and then subjected to tooth extraction on the mandible and maxilla and a bone defect creation on the femur. After the surgical procedures, ZA or saline treatment was continued until sacrifice at week 2, week 4, and week 8 postoperatively. Vascular perfusion with MICROFIL was performed on all the animals. Micro-CT analysis demonstrated a tendency of decreased vessel density and vessel number in ZA-treated groups but no statistical difference. In conclusion, the neovessel formation is suppressed but not significantly by ZA treatment, indicating that angiogenesis inhibition may contribute to the development of MRONJ but does not play a key role.

Effect of Age and Sodium Alendronate on Femoral Fracture Repair: Biochemical and Biomechanical Study in Rats

BACKGROUND

Bisphosphonates are drugs widely used to reduce bone resorption, increase bone mineral density and control age-related bone loss. Although there are studies reporting differences in bone structure between young and old adults, it is still difficult to predict changes related to bone aging. The aim of this study was to evaluate the effect of age and sodium alendronate on bone repair of femoral fractures in rats.

METHODS

Wistar rats (n = 40) were allocated into groups: O (control old-rats), Y (control young-rats), OA (alendronate old-rats) and YA (alendronate young-rats). All animals underwent linear fracture surgery followed by fixation. Groups OA and YA received 1 mg/kg alendronate three times a week until euthanasia. Biochemical analysis of calcium and alkaline phosphatase was done. After euthanasia, femurs were evaluated in relation to cross-section and flexural strength, with three-point bending test. Data were submitted to statistical analysis with significance level of 0.05.

RESULTS

There was no difference in calcium and alkaline phosphatase levels (p > 0.05). Young animals presented lower cross-section than older animals (p < 0.05). Only fractured side, young animals presented major flexural strength than older animals (p < 0.05). There was no difference between the animals that used or not alendronate in relation to cross-section and flexural strength (p > 0.05). When compared fractured and non-fractured femurs, major cross-section on fractured side was observed (p < 0.05). Flexural strength presented higher values in femurs on non-fractured side (p < 0.05). There was correlation of weight and cross-section (R = +0.91) and weight with flexural strength of fractured and non-fractured side, respectively (R = -0.97 and -0.71).

CONCLUSION

In short, there was no difference of calcium and alkaline phosphatase during the bone repair process. Age has influence in cross-section and flexural strength. Alendronate showed no association with these factors.

Topical co-administration of zoledronate with recombinant human bone morphogenetic protein-2 can induce and maintain bone formation in the bone marrow environment

Background

Bone morphogenetic proteins (BMPs) induce osteogenesis in various environments. However, when BMPs are used alone in the bone marrow environment, the maintenance of new bone formation is difficult owing to vigorous bone resorption. This is because BMPs stimulate the differentiation of not only osteoblast precursor cells but also osteoclast precursor cells. The present study aimed to induce and maintain new bone formation using the topical co-administration of recombinant human BMP-2 (rh-BMP-2) and zoledronate (ZOL) on beta-tricalcium phosphate (β-TCP) composite.

Methods

β-TCP columns were impregnated with both rh-BMP-2 (30 µg) and ZOL (5 µg), rh-BMP-2 alone, or ZOL alone, and implanted into the left femur canal of New Zealand white rabbits (n = 56). The implanted β-TCP columns were harvested and evaluated at 3 and 6 weeks after implantation. These harvested β-TCP columns were evaluated radiologically using plane radiograph, and histologically using haematoxylin/eosin (H&E) and Masson’s trichrome (MT) staining. In addition, micro-computed tomography (CT) was performed for qualitative analysis of bone formation in each group (n = 7).

Results

Tissue sections stained with H&E and MT dyes revealed that new bone formation inside the β-TCP composite was significantly greater in those impregnated with both rh-BMP-2 and ZOL than in those from the other experimental groups at 3 and 6 weeks after implantations (p < 0.05). Micro-CT data also demonstrated that the bone volume and the bone mineral density inside the β-TCP columns were significantly greater in those impregnated with both rh-BMP-2 and ZOL than in those from the other experimental groups at 3 and 6 weeks after implantations (p < 0.05).

Conclusions

The topical co-administration of both rh-BMP-2 and ZOL on β-TCP composite promoted and maintained newly formed bone structure in the bone marrow environment.

Timing of Bisphosphonate Initiation After Fracture: What Does the Data Really Say?

Introduction:

Osteoporosis is often not clinically recognized until after a fracture occurs. Individuals who have 1 fracture are at increased risk of future fractures. Prompt initiation of osteoporosis treatment following fracture is critical to reducing the rate of future fractures. Antiresorptives are the most widely used class of medications for the prevention and treatment of osteoporosis. Many providers are hesitant to initiate antiresorptives in the acute post-fracture period. Concerns include interference with bone remodeling necessary for successful fracture healing, which would cause increased rates of non-union, malunion, and refracture. While such concerns should not extend to anabolic medications, physicians may also hesitate to initiate anabolic osteoporosis therapies due to high cost and/or lack of familiarity. This article aims to briefly review the available data and present a digestible narrative summary to familiarize practicing orthopaedic surgeons with the essential details of the published research on this topic.

Results:

The results of 20 clinical studies and key pre-clinical studies related to the effect of anti-resorptive medications for osteoporosis on fracture healing are summarized in the body of this narrative review.

Discussion & Conclusions:

While few level I studies have examined the impact of timing of initiation of osteoporosis medications in the acute post-fracture period, the few that have been published do not support these concerns. Specifically, data from level I clinical trials indicate that initiating bisphosphonates as early as 2 weeks post-fracture does not increase rates of non-union or malunion. By reviewing the available data, we hope to give clinicians the confidence to initiate osteoporosis treatment promptly post-fracture.

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.

Zoledronic Acid Substantially Improves Bone Microarchitecture and Biomechanical Properties After Rotator Cuff Repair in a Rodent Chronic Defect Model

BACKGROUND

Bone mineral density at the humeral head is reduced in patients with chronic rotator cuff tears. Bone loss in the humeral head is associated with repair failure after rotator cuff reconstruction. Bisphosphonates (eg, zoledronic acid) increase bone mineral density.

HYPOTHESIS

Zoledronic acid improves bone mineral density of the humeral head and biomechanical properties of the enthesis after reconstruction of chronic rotator cuff tears in rats.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 32 male Sprague-Dawley rats underwent unilateral (left) supraspinatus tenotomy with delayed transosseous rotator cuff reconstruction after 3 weeks. All rats were sacrificed 8 weeks after rotator cuff repair. Animals were randomly assigned to 1 of 2 groups. At 1 day after rotator cuff reconstruction, the intervention group was treated with a single subcutaneous dose of zoledronic acid at 100 µg/kg bodyweight, and the control group received 1 mL of subcutaneous saline solution. In 12 animals of each group, micro-computed tomography scans of both shoulders were performed as well as biomechanical testing of the supraspinatus enthesis of both sides. In 4 animals of each group, histological analyses were conducted.

RESULTS

In the intervention group, bone volume fraction (bone volume/total volume [BV/TV]) of the operated side was higher at the lateral humeral head (P = .005) and the medial humeral head (P = .010) compared with the control group. Trabecular number on the operated side was higher at the lateral humeral head (P = .004) and the medial humeral head (P = .001) in the intervention group. Maximum load to failure rates on the operated side were higher in the intervention group (P < .001). Cortical thickness positively correlated with higher maximum load to failure rates in the intervention group (r = 0.69; P = .026). Histological assessment revealed increased bone formation in the intervention group.

CONCLUSION

Single-dose therapy of zoledronic acid provided an improvement of bone microarchitecture at the humeral head as well as an increase of maximum load to failure rates after transosseous reconstruction of chronic rotator cuff lesions in rats.

CLINICAL RELEVANCE

Zoledronic acid improves bone microarchitecture as well as biomechanical properties after reconstruction of chronic rotator cuff tears in rodents. These results need to be verified in clinical investigations.

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.

Effect of Osteoporosis Medication on Fracture Healing: An Evidence Based Review

A systematic search was conducted and relevant studies that evaluated the influence of osteoporosis medications (bisphosphonates [BPs], denosumab, selective estrogen receptor modulators [SERMs], recombinant human parathyroid hormone teriparatide [TPTD], and strontium ranelate [SrR]) on wrist, hip, and spine fracture healing, were selected. BPs administration did not influence fracture healing and clinical outcomes after distal radius fracture (DRF). Similar results were observed in hip fracture, but evidence is lacking for spine fracture. Denosumab did not delay the non-vertebral fractures healing in one well-designed study. No studies evaluated the effect of SERMs on fracture healing in humans. One study reported shorter fracture healing times in TPTD treated DRF patients, which was not clinically meaningful. In hip fracture, recent studies reported better pain and functional outcomes in TPTD treated patients. However, in spine fracture, recent studies found no significant differences in fracture stability between TPTD treated patients and controls. Evidence is lacking for SrR, but it did not influence wrist fracture healing in one study. In comparisons between TPTD and BPs, fracture healing and physical scores were not significantly different in hip fracture by 1 study. In spine fracture, controversy exists for the role of each medication to the fracture stability, but several studies reported that fracture site pain was better in TPTD treated patients than BPs treated patients. Considering no clinical data of negative fracture healing of the antiresorptive medication and the danger of subsequent fracture after initial osteoporotic fracture, there is no evidence to delay initiation of osteoporosis medications after fracture.

Pretreatment with Pamidronate Decreases Bone Formation but Increases Callus Bone Volume in a Rat Closed Fracture Model

Clinical concerns have been raised over prior exposure to bisphosphonates impairing fracture healing. To model this, groups of male Wistar rats were assigned to saline control or treatment groups receiving 0.15 mg/kg (low dose), 0.5 mg/kg (medium dose), and 5 mg/kg (high dose) Pamidronate (PAM) twice weekly for 4 weeks. At this point, closed fractures were made using an Einhorn apparatus, and bisphosphonate dosing was continued until the experimental endpoint. Specimens were analyzed at 2 and 6 weeks (N = 8 per group per time point). Twice weekly PAM dosing was found to have no effect on early soft callus remodeling at 2 weeks post fracture. At this time point, the highest dose PAM group gave significant increases in bone volume (+ 10%, p < 0.05), bone mineral content (+ 30%, p < 0.01), and bone mineral density (+ 10%, p < 0.01). This PAM dosing regimen showed more substantive effects on hard callus at 6 weeks post fracture, with PAM treatment groups showing + 46-79% increased bone volume. Dynamic bone labeling showed reduced calcein signal in the PAM-treated calluses (38-63%, p < 0.01) and reduced MAR (32-49%, p < 0.01), suggesting a compensatory reduction in bone anabolism. These data support the concept that bisphosphonates lead to profound decreases in bone turnover in fracture repair, however, this does not affect soft callus remodeling.

Synthetic hydroxyapatite: a recruiting platform for biologically active molecules

Background and purpose - Targeted delivery of drugs is important to achieve efficient local concentrations and reduce systemic side effects. We hypothesized that locally implanted synthetic hydroxyapatite (HA) particles can act as a recruiting moiety for systemically administered drugs, leading to targeted drug accretion.Methods - Synthetic HA particles were implanted ectopically in a muscle pouch in rats, and the binding of systemically circulating drugs such as zoledronic acid (ZA), tetracycline and ¹⁸F-fluoride (¹⁸F) was studied. The local biological effect was verified in an implant integration model in rats, wherein a hollow implant was filled with synthetic HA particles and the animals were given systemic ZA, 2-weeks post-implantation. The effect of HA particle size on drug binding and the possibility of reloading HA particles were also evaluated in the muscle pouch.Results - The systemically administered biomolecules (ZA, tetracycline and ¹⁸F) all sought the HA moiety placed in the muscle pouch. Statistically significant higher peri-implant bone volume and peak force were observed in the implant containing HA particles compared with the empty implant. After a single injection of ZA at 2 weeks, micro HA particles showed a tendency to accumulate more ¹⁴C-zoledronic acid (¹⁴C-ZA) than nano-HA particles in the muscle pouch. HA particles could be reloaded when ZA was given again at 4 weeks, showing increased ¹⁴C-ZA accretion by 73% in microparticles and 77% in nanoparticles.Interpretation - We describe a novel method of systemic drug loading resulting in targeted accretion in locally implanted particulate HA, thereby biologically activating the material.

Bone union after spinal fusion surgery using local bone in long-term bisphosphonate users: a prospective comparative study

Bisphosphonates are the most commonly used drugs for osteoporosis and long-term use of bisphosphonates may affect fusion rate after spinal fusion surgery. There was significant delayed union after 6 months in long-term bisphosphonates users; however, there were no significant difference in fusion rate of long-term bisphosphonate users. Therefore, spinal fusion surgery should not be hesitated in long-term bisphosphonates users.

PURPOSE

Bisphosphonates (BPs) are the most popular class of drugs for treatment of postmenopausal osteoporosis. Long-term use of BPs may also inhibit the spinal fusion process after posterior lumbar interbody fusion (PLIF). We compared bone fusion rates of long-term BPs users and non-users after undergoing spinal fusion surgery.

METHODS

A total of 97 postmenopausal women who were candidates for single-level PLIF were recruited from 2015 to 2016. Participants were divided into two groups, with 63 patients in a long-term BPs user group and 34 patients in a non-user group. Serum C-terminal cross-linking telopeptide (CTX) levels were checked for bone resorption markers. Bone fusion rates were calculated at 6 months and 1 and 2 years after the surgery. Clinical outcomes were measured using the Oswestry Disability Index (ODI) and visual analog scale (VAS).

RESULTS

Serum CTX level was dramatically decreased in the long-term BPs user group (p < 0.05). Fusion rates at 6 months after surgery were 42% in the non-user group and 26% in the long-term BPs user group (p = 0.035). However, fusion rates were 82% in the long-term BPs user group and 87% in the non-user group at 2 years after surgery (p > 0.05). There was no significant difference between the two groups in ODI or VAS.

CONCLUSIONS

Even though there was significant delayed union after 6 months in long-term BPs users, at the 2-year postoperative follow-up, there was no significant difference in bone fusion rate between the two groups. Long-term BPs users showed fusion rates greater than 80% and clinical outcome improvements that were comparable to those in non-users. No significant effect on fusion rate after PLIF was found in long-term BPs users.

Biological factors involved in alveolar bone regeneration: Consensus report of Working Group 1 of the 15th European Workshop on Periodontology on Bone Regeneration

BACKGROUND AND AIMS

To describe the biology of alveolar bone regeneration.

MATERIAL AND METHODS

Four comprehensive reviews were performed on (a) mesenchymal cells and differentiation factors leading to bone formation; (b) the critical interplay between bone resorbing and formative cells; (c) the role of osteoimmunology in the formation and maintenance of alveolar bone; and (d) the self-regenerative capacity following bone injury or tooth extraction were prepared prior to the workshop.

RESULTS AND CONCLUSIONS

This summary information adds to the fuller understanding of the alveolar bone regenerative response with implications to reconstructive procedures for patient oral rehabilitation. The group collectively formulated and addressed critical questions based on each of the reviews in this consensus report to advance the field. The report concludes with identified areas of future research.

Effect of low-level laser therapy and zoledronic acid on bone repair process

This study aimed to evaluate, through histomorphometric analysis, the bone repair process in the tibia of rats treated with zoledronic acid and submitted to 808-nm low-level laser therapy (LLLT) by using arsenide aluminum gallium laser. For this purpose, 20 rats were used and distributed according to treatment: group 1-saline administration; group 2-treated with LLLT; group 3-treated with zoledronic acid; and group 4-treated with zoledronic acid and LLLT. The zoledronic acid was administered at a dose of 0.035 mg/kg every 2 weeks for 8 weeks. Subsequently, bone defects of 2 mm were prepared in the tibias of all groups. The bone defects in groups 2 and 4 were irradiated with LLLT in the immediate post-operative period. After 14 and 28 days of application, the animals were submitted and euthanized for histomorphometric analysis. The results were submitted to statistical analysis (α = 5%), and the intragroup comparison was performed using the t test. On the other hand, for intergroup comparison, the ANOVA test was performed, and to the groups presenting statistically significant difference, the Student-Newman-Keuls test was used. In intergroup comparison, group 1 (mean ± SD= 45.2 ± 18.56%) showed a lower bone formation compared with groups 2 (64.13 ± 3.51%) (p = 0.358) and 4 (15.2 ± 78.22%) (p = 0.049), at the 14-day period. Group 3 (20.99 ± 7.42%) also presented a lower amount of neoformed bone tissue, with statistically significant difference when compared with groups 1 (p = 0.002), 2, and 4 (p ≤ 0,001). After 28 days, group 1 presented a lower amount of neoformed bone tissue compared with the other groups, with p = 0.020. Thus, it was concluded that LLLT associated with zoledronic acid is effective for stimulating bone formation in surgically created defects in rats, at the periods studied.

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.

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.

The effect of graft application and allopurinol treatment on calvarial bone defect in rats1

Purpose

To investigate the effects of allopurinol administration on osteoinductive reaction and bone development with graft material.

Methods

Thirty-six Wistar albino rats were divided into 3 groups. In the control group, calvarial bone defect was only created without any treatment. In the Defect + Graft group, allograft treatment was performed by forming 8 mm calvarial bone defect. In the Defect + Graft + Allopurinol group, alloplastic bone graft was placed in the calvarial bone defect and then, allopurinol (50 mg/kg/day) treatment was intraperitoneally applied for 28 days.

Results

Histopathological examination revealed inflammation, congestion in the vessels, and an increase in osteoclast cells in the defect area. We also observed that new osteocyte cells, increase in connective tissue fibers, and new bone trabeculae. Osteopontin expression was positive in osteoblast cells and lacunated osteocyte cells were located in the periphery of the new bone trabeculae. Osteopontin expression was also positive in osteoblasts and osteocytes cells of new bone trabeculae in the graft site.

Conclusion

It has been shown that allopurinol treatment in rat calvaria defects may induce osteoblastic activity, matrix development, mature bone cell formation and new bone formation when used with autogenous grafts.

Zoledronic acid administration enhances fracture healing in the osteoporotic fractures in ovariectomized rabbits

Objectives: To evaluate the radiological, histological and mechanical effects on osteoporotic fracture healing of single-dose zoledronic acid (ZA) applied to an animal model with an experimentally created osteoporotic bone fracture. Methods: A total of 14 adult, female New Zealand rabbits, aged 5-6 months were used in the study. Bone mineral density (BMD) values were calculated from bone densitometry measurements and recorded. Bilateral ovariectomy was then applied to all the rabbits. At 10 weeks after ovariectomy, bone densitometry was again performed on all the animals and the BMD values were compared. Osteoporosis was accepted as having developed in animals determined with a reduction of 28% in BMD values. After the placement of a K-wire intramedullarly in the femurs of the rabbits, a closed fracture was created with the standard method. The animals were then randomly separated into 2 groups as the zoledronic acid group (ZAG) and the control group (CG). An infusion of 0.1 mg/kg ZAwas administered to the ZAG animals from the ear vein. With visualisation of bone union rabbits were sacrificed by decapitation. Radiological, mechanical and histological assesments were then applied. Results: In the histological evaluation, the mean histological score was determined as 5.00 in the ZAG and 3.00 in the CG. The difference between the groups was found to be statistically significant (p < 0.001). In the radiological evaluation, the mean score was 7.00 in the ZAG and 6.25 in the CG. Even though higher points were obtained by the ZAG in the inter-observer evaluations, the difference between the groups was not statistically significant (p = 0.073). In the mechanical evaluation, the elasticity collapse in negative proportion to rigidity was measured as 2.91 mm in the ZAG and 3.96 mm in the CG (p = 0.686). The rigidity data of the ZAG were higher in the mechanical tests but the difference between the groups was not statistically significant (p = 0.086). Conclusion: As the results of the study showed that the ZAG had higher values than those of the CG in all the histological, mechanical and radiological evaluations, the application of a single dose of ZA can be considered to increase the healing of osteoporotic fractures.

Combination therapy with low-dose teriparatide and zoledronate contributes to fracture healing on rat femoral fracture model

Background

Delay in fracture healing or non-union can be devastating complication. Recent studies have reported that teriparatide (TP) demonstrated effectively on callus formation and mechanical strength and zoledronate (ZA) increased the callus size and resistance at the fracture site in rat fracture model. In this study, the effects of combination therapy with low dose TP and ZA on fracture healing was evaluated.

Methods

From 1 week post-operation, TP (5 times a week administration) and ZA (0.1 mg/kg single administration) were administered by dividing the rats into the following five groups: TP 1 μg group {T(1): TP 1 μg/kg}, ZA group (ZA:0.1 mg/kg), TP1 μg+ZA group {T(1)+ZA: TP 1 μg/kg+ZA}, TP 10 μg+ZA group {T(10)+ZA: TP 10 μg/kg + ZA}, and control group (C: administered saline). Rt femurs were excised 7 weeks after the surgery; bone fusions were evaluated with soft X-ray images on a 4-point scale. And the histopathological examination was performed in demineralized and non-demineralized specimens. Furthermore, the Radiographic Union Scale was conducted in all specimens.

Results

About the bone fusions rates, C, T(1), ZA, T(1)+ZA, and T(10)+ZA groups demonstrated 20.0%, 55.6%, 70.0%, 70.0%, and 80.0%, respectively, and with 4-point scale, each group was 0.50, 1.56, 2.00, 2.60, and 2.80 points, respectively. The callus volume was significantly increased to 16.66 mm² and 17.75 mm² in the T(1)+ZA and T(10)+ZA groups, respectively, while 10.65 mm² (p < 0.05) in the C group. Furthermore, the callus area in the T(10)+ZA group was also observed to have significantly increased to 78.78%, compared with 54.63% and 44.11% in the C and T(1)+ZA groups, respectively (p < 0.01). Histopathologically, cartilage tissue and immature callus formation were observed at the bone junction in the C group; however, the osseous bridge formation of mature callus was observed in the ZA, T(1)+ZA, and T(10)+ZA groups.

Conclusion

It is suggested that administration of low dose TP and ZA in combination may lead to the treatment of delayed union of fracture. We hope the combination treatment may become one of new therapeutic strategy.

Update on the Comprehensive Approach to Fragility Fractures

The prevention and treatment of fragility fractures continuously evolve. Adequate fracture care should involve treating the fracture itself and the underlying bone disease. Although effective treatments of osteoporosis are available, a large proportion of patients with fragility fractures are not prescribed antiosteoporotic medications after their injury. Recent advances in diagnostic tools, medications, and implementation of Fracture Liaison Services allow for more effective and comprehensive treatment or fragility fractures. In the Fracture Liaison Service model, a physician and physician extenders coordinate care. This includes a thorough medical and surgical history, metabolic bone disease laboratory testing, dual-energy x-ray absorptiometry screening, treatment, and long-term follow-up. Treatment options include nonpharmacologic treatment with calcium and vitamin D and antiresorptive and anabolic agents. Antiresorptive agents such as bisphosphonates and denosumab are first-line treatments for osteoporosis and anabolic agents such as teriparatide are effective in reducing bone density loss and have implications in fracture healing. In addition, new anabolic agents including antisclerostin antibodies and parathyroid hormone-related protein show promise as potential treatments to increase bone density.

The effects of bisphosphonates on osteoporotic patients after lumbar fusion: a meta-analysis

Purpose

We conducted a meta-analysis of controlled clinical trials to evaluate the efficacy of bisphosphonates in lumbar fusion.

Introduction

Bisphosphonates reduce bone resorption and remodeling by osteoclast activity inhibition, inactivation, and apoptosis. However, it remains controversial whether bisphosphonate therapy affects spinal fusion.

Methods

We searched MEDLINE, Cochrane CENTRAL, ScienceDirect, EMBASE, and Google Scholar to identify studies reporting the effects of bisphosphonates on osteoporotic patients after lumbar fusion. Secondary sources were identified from the references of the included literature. Pooled data were analyzed using RevMan 5.1.

Results

Seven studies met the inclusion criteria. There were significant differences in solid intervertebral fusion (RD=0.07, 95% CI: −0.00 to 0.15, P=0.05), subsequent VCFs (RD=−0.21, 95% CI: −0.30 to −0.12, P<0.00001), pedicle screw loosening (RD=−0.17, 95% CI: −0.28 to −0.05, P=0.006), and cage subsidence (RD=−0.25, 95% CI: −0.42 to −0.07, P=0.005) between two groups. No significant differences between two groups were found regarding implant fixation failure (RD=−0.06, 95% CI: −0.22 to 0.10, P=0.48).

Conclusion

This meta-analysis showed that bisphosphonates may increase solid intervertebral fusion and decrease subsequent VCFs, pedicle screw loosening, and cage subsidence.

Negative effect of zoledronic acid on tendon-to-bone healing

Background and purpose - Outcome after ligament reconstruction or tendon repair depends on secure tendon-to-bone healing. Increased osteoclastic activity resulting in local bone loss may contribute to delayed healing of the tendon-bone interface. The objective of this study was to evaluate the effect of the bisphosphonate zoledronic acid (ZA) on tendon-to-bone healing. Methods - Wistar rats (n = 92) had their right Achilles tendon cut proximally, pulled through a bone tunnel in the distal tibia and sutured anteriorly. After 1 week animals were randomized to receive a single dose of ZA (0.1 mg/kg IV) or control. Healing was evaluated at 3 and 6 weeks by mechanical testing, dual-energy X-ray absorptiometry and histology including immunohistochemical staining of osteoclasts. Results - ZA treatment resulted in 19% (95% CI 5-33%) lower pullout strength and 43% (95% CI 14-72%) lower stiffness of the tendon-bone interface, compared with control (2-way ANOVA; p = 0.009, p = 0.007). Administration of ZA did not affect bone mineral density (BMD) or bone mineral content (BMC). Histological analyses did not reveal differences in callus formation or osteoclasts between the study groups. Interpretation - ZA reduced pullout strength and stiffness of the tendon-bone interface. The study does not provide support for ZA as adjuvant treatment in tendon-to-bone healing.

Healing in peri-implant gap with BMP-2 and systemic bisphosphonate is dependent on BMP-2 dose-A canine study

The bone-implant interface of cementless orthopedic implants can be described as a series of uneven sized gaps with discontinuous areas of direct bone-implant contact. Bridging these voids and crevices by addition of an anabolic stimulus to increase new bone formation can potentially improve osseointegration of implants. Bone morphogenetic protein 2 (BMP-2) stimulates osteoblast formation to increase new bone formation but also indirectly stimulates osteoclast activity. In this experiment, we investigate the hypothesis that osseointegration, defined as mechanical push-out and histomorphometry, depends on the dose of BMP-2 when delivered as an anabolic agent with systemic administration of the anti-resorptive agent zoledronate to curb an increase in osteoclast activity. Four porous coated titanium implants (one with each of three doses of surface-applied BMP-2 (15 µg; 60 µg; 240 µg) and untreated) surrounded by a 0.75 mm empty gap, were inserted into the distal femurs of each of twelve canines. Zoledronate IV (0.1 mg/kg) was administered 10 days into the observation period of 4 weeks. Bone-implant specimens were evaluated by mechanical push-out test and histomorphometry. The 15 µg implants had the best fixation on all mechanical parameters and largest surface area covered with new bone compared to the untreated, 60 and 240 µg implants, as well as the highest volume of new bone in the implant gap compared to 60 and 240 µg implants. The results in a canine implant model demonstrated that a narrow range of BMP-2 doses have opposite effects in bridging an empty peri-implant gap with bone, when combined with systemic zoledronate. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1406-1414, 2018.

Dose-Dependent Resorption of Allograft by rhBMP-2 Uncompensated by New Bone Formation-A Canine Study With Implants and Zoledronate

BACKGROUND

Impacted bone allograft is used to restore lost bone in total joint arthroplasties. Bone morphogenetic proteins (BMPs) can induce new bone formation to improve allograft incorporation, but they simultaneously invoke a seemingly dose-dependent allograft resorption mediated by osteoclasts. Bisphosphonates effectively inhibit osteoclast activity. Predicting allograft resorption when augmented with bone morphogenetic protein 2 (BMP-2), we intended to investigate whether a balanced bone metabolism was achievable within a range of BMP-2 doses with systemic zoledronate treatment.

METHODS

Implants were coated with 1 of 3 BMP-2 doses (15 μg, 60 μg, and 240 μg) or left untreated. Implants were surrounded by a 2.5-mm gap filled with impacted morselized allograft. Each of the 12 dogs included received 1 of each implant (15 μg, 60 μg, 240 μg, and untreated), 2 in each proximal humerus. During the 4-week observation period, zoledronate intravenous (0.1 mg/kg) was administered to all animals 10 days after surgery as anticatabolic treatment. Implant osseointegration was evaluated by histomorphometry and mechanical push-out tests.

RESULTS

Untreated implants had the best mechanical fixation and superior retention of allograft as compared to any of the BMP-2 implants. Both mechanical implant fixation and retention of allograft decreased significantly with BMP-2 dose increments. Surprisingly, there was no difference among the treatment groups in the amount of new bone.

CONCLUSION

The use of BMP-2 to augment impaction-grafted implants cannot be recommended even when combined with systemic zoledronate.

Evaluation of mandibular fracture healing in rats under zoledronate therapy: A histologic study

INTRODUCTION

To evaluate fracture healing in mandible of rats under zoledronate therapy.

METHODS

A total of 135 Wistar rats were randomly allocated into 3 groups. Group L received two intravenous infusion of 0.06 mg/kg zoledronate 6 weeks apart. Group H received the same dose of zoledronate as group L once a week for 6 weeks and group C were treated with normal saline. Seven days after the last infusion, rats underwent unilateral mandibular osteotomy to replicate a fracture. Fifteen rats from each group were sacrificed 2, 4, and 6 weeks after surgery. Fracture calluses were examined and scored using a histological grading system (1 to 10).

RESULTS

After 2 weeks, substantial woven bone and some lamellar bone were seen in control and L groups. In group H, healing was delayed and consisted of fibrous and cartilaginous tissue and some woven bone. After 4 weeks, most of woven bone in control group was replaced with lamellar bone but in group L, comparatively less bone remodeling occurred. In group H, healing process was nearly the same as that at 2 weeks. After 6 weeks, complete bone remodeling was seen in control group. In group L, bone remodeling was under way and in group H, histological findings were nearly the same as those at 2 and 4 weeks. Except for L and control groups at 2 weeks, healing score was significantly different between all corresponding groups.

CONCLUSION

Zoledronate therapy delayed healing process of mandibular fracture in rats in a dose-dependent manner.

Local application of an ibandronate/collagen sponge improves femoral fracture healing in ovariectomized rats

Non-union is a major clinical problem in the healing of fractures, especially in patients with osteoporosis. The systemic administration of drugs is time consuming and large doses are demanding and act slowly, whereas local release acts rapidly, increases the quality and quantity of the bone tissue. We hypothesize that local delivery demonstrates better therapeutic effects on an osteoporotic fracture. The aim of this paper is to investigate the effect of the local application of ibandronate loaded with a collagen sponge on regulating bone formation and remodeling in an osteoporotic rat model of fracture healing. We found that the local delivery of ibandronate exhibited excellent effects on improving the bone microarchitecture and suppressed effects on bone remodeling. At 4 weeks, more callus formation and improvement of mechanical character and microstructure were observed in a local delivery via μCT, mechanical test, histological research and serum analysis. The suppression of bone remodeling was compared with a systemic treatment at 12 weeks, and the structural mechanical properties and microarchitecture were also improved with local delivery. This research identifies an earlier, safer and integrated approach for local delivery of ibandronate with collagen and provides a better strategy for the treatment of osteoporotic fracture in rats.