New model for simulation of fracture repair in full-grown beagle dogs: model characterization and results from a long-term study with ibandronate

Review of the Mechanism of Action and Use of Bisphosphonates in Horses

Bisphosphonates are a group of drugs that can reduce bone resorption by incorporating into the crystal structure of exposed hydroxyapatite where they are taken up by osteoclasts. Bisphosphonates have several other mechanisms of action including reducing pain and inflammation and altering macrophage function. There are two types of bisphosphonates - nitrogenous and non-nitrogenous, the latter of which is used in horses. This article provides a literature-based review of the proposed mechanisms of action and therapeutic uses of bisphosphonates including a brief review of bone response to disease. A review of the literature available in horses including safety data and current rules and regulations is also provided.

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.

The use of bisphosphonates to meet orthopaedic challenges

The anti-resorptive properties of bisphosphonates have been explored to manage several conditions that traditionally have required a surgical solution. In osteonecrosis, their use is predicated on the principle that bone collapse occurs during the revascularisation phase of the disease. If the associated resorptive activity were modulated, the resultant preserved joint architecture may improve clinical outcome and reduce the need for joint replacement. Pre-clinical and small-scale clinical studies have given non-conclusive support for this principle. Adequately powered clinical trials with relevant long-term endpoints are still required to firmly clarify the clinical efficacy of this treatment. Several clinical studies have shown that bisphosphonates can reduce periprosthetic bone loss and, in some situations, enhance implant fixation in the early period after joint replacement. This may be advantageous in settings where osseointegration is problematic. However, the ultimate goals of their use in joint replacement has been to reduce the incidence of late periprosthetic inflammatory osteolysis, the main cause of prosthesis failure. Population-based observational studies have associated bisphosphonate use with a lower incidence of revision surgery, supported by pre-clinical data. However, clinical trials have, to date, failed to demonstrate any efficacy for the human disease. The timing of bisphosphonate administration for secondary prevention after acute osteoporotic fracture has been subject to extensive investigation, with pre-clinical studies showing increased callus formation but decreased remodelling and no effect on the restoration of mechanical integrity of bone. Meta-analysis of clinical trial data indicates that early administration of bisphosphonate after acute fracture does not adversely affect fracture union, pain or functional outcomes. Finally, bisphosphonates have also been explored as a treatment for complex regional pain syndrome type-I. A recent meta-analysis has shown a beneficial effect on visual analogue scale pain scores, but an increase in mild adverse events.

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.

Effect of Preoperative Bisphosphonate Treatment on Fracture Healing after Internal Fixation Treatment of Intertrochanteric Femoral Fractures

Purpose

There are concerns that administration of bisphosphonate (BP) can substantially suppress bone turnover, potentially interfering with fracture healing. We investigated the effects of preoperative BP administration before internal fixation of intertrochanteric femoral fractures using fracture healing and clinical outcomes.

Materials and Methods

We retrospectively analyzed data from 130 patients who underwent internal fixation for osteoporotic intertrochanteric femoral fractures between March 2012 and July 2016. Patients previously treated with BPs for at least 3 months (BP group; n=29) were compared with the remaining patients (BP-naïve group; n=101). Radiographs were used to assess and compare fracture healing 3 months and 1 year postsurgery. The primary clinical outcome measure assessed was change in Koval score.

Results

Fracture union at 3 months after surgery was verified in 72.4% of patients (21/29) in the BP group and 90.1% of patients (91/101) in the BP-naïve group (P=0.027). Fracture union at 1 year postsurgery (BP group, 93.1% [27/29] vs. BP-naïve group, 97.0% [98/101], P=0.310) and change in Koval score (1.1 vs. 1.0, P=0.694) were not significantly different between the groups. Multivariable logistic regression analysis revealed that a history of BP administration was associated with an increased risk of delayed union at 3 months postsurgery (P=0.014).

Conclusion

Preoperative administration of BP was associated with a decreased fracture healing rate 3 months after internal fixation, compared with BP-naïve patients. Therefore, patients previously treated with a BP should be carefully allowed to wean off walking aids and transition to full weight-bearing in the early postoperative period.

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

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

Effects of 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.

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.

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.

How do bisphosphonates affect fracture healing?

Bisphosphonates (BPs) have been in use for many years for the treatment of osteoporosis, multiple myeloma, Paget's disease, as well as a variety of other diseases in which there is reduced bone mineral density. Given that bisphosphonates inhibit bone resorption, an important stage of fracture healing; this class of compounds has been widely studied in preclinical models regarding their influence on fracture healing. In animal models, bisphosphonate treatment is associated with a larger fracture callus, coincident with a delay in remodeling from primary woven bone to lamellar bone, but there is no delay in formation of the fracture callus. In humans, de novo use of bisphosphonate therapy after fracture does not appear to have a significant effect on fracture healing. Rarely, patients with long term use of Bisphosphonates may develop an atypical fracture and delay in fracture healing has been observed. In summary, bisphosphonates appear safe for use in the setting of acute fracture management in the upper and lower extremity in humans. While much remains unknown about the effects on healing of long-term bisphosphonates, use prior to "typical" fracture, in the special case of atypical fracture, evidence suggests that bisphosphonates negatively influence healing.

Odanacatib increases mineralized callus during fracture healing in a rabbit ulnar osteotomy model

The effects of the cathepsin K inhibitor odanacatib (ODN) on fracture healing were monitored for ~6 and 15 weeks post-fracture in two separate studies using the unilateral transverse mid-ulnar osteotomy model in skeletally mature female rabbits. Rabbits were pre-treated for 3-4 weeks with vehicle (Veh), ODN (2 mg/kg, po, daily), or alendronate (ALN) (0.3 mg/kg, sc, twice-weekly) prior to osteotomy. In Study 1, the animals were maintained on the same respective treatment for ~6 weeks. In Study 2, the animals were also continued on the same therapy or switched from Veh to ODN or ODN to Veh for 15 weeks. No treatment-related impairment of fracture union was seen by qualitative histological assessments in the first study. Cartilage retention was detected in the calluses of ALN-treated rabbits at week-6, while calluses in the ODN and Veh groups contained bony tissue with significantly less residual cartilage. ODN treatment also markedly increased the number of cathepsin K-(+) osteoclasts in the callus, indicating enhanced callus remodeling. From the second study, ex vivo DXA and pQCT confirmed that ODN treatment pre- and post-osteotomy increased callus bone mineral content and bone mineral density (BMD) versus Veh (p < 0.001) and discontinuation of ODN post-surgery returned callus BMD to Veh. Peak load of ODN- or ALN-treated calluses were comparable to Veh. ODN increased callus yield load (20%, p = 0.056) and stiffness (26%, p < 0.05) versus Veh. These studies demonstrated that ODN increased mineralized callus during the early phase of fracture repair without impairing callus formation or biomechanical integrity at the fracture site.

Timing of the initiation of bisphosphonates after surgery for fracture healing: a systematic review and meta-analysis of randomized controlled trials

SUMMARY

We performed a systematic review and meta-analysis of randomized clinical trials. Early administration of bisphosphonates (BPs) after surgery did not appear to delay fracture healing time either radiologically or clinically. Furthermore, the anti-resorptive efficacy of BPs given immediately after surgical repair should positively affect the rate of subsequent fractures.

INTRODUCTION

Bisphosphonates (BPs) are widely used in the prophylaxis and treatment of osteoporosis. However, early administration of BPs after surgical repair of a fracture may limit the reserve capacity of bone to heal. The aim of this review and meta-analysis was to analyze the benefits and adverse effects of early administration of BPs and give recommendations regarding when BPs should be utilized.

METHODS

We identified randomized controlled trials comparing the early administration of BPs to placebo, delayed BP treatment, or no therapy in adult patients after surgery. The search was performed in PubMed, the Cochrane Library, and Embase.

RESULTS

Ten studies with 2888 patients were included. Four trials used alendronate, three trials used zoledronic, two trials used risedronate, and one trial used etidronate. Early administration of BPs was considered less than 3 months after surgery. Patients treated with BP therapy had no significant differences in radiological fracture healing times compared with patients in the control group (mean difference [MD] 0.47, 95% confidence interval [CI] -2.75 to 3.69). There were also no significant differences in the rate of delay or nonunion of fracture healing (odds ratio [OR] 0.98, 95% CI 0.64 to 1.50). However, the bone mineral density (BMD) of total hips did significantly improve after 12 months of treatment with BPs. And most bone turnover markers of patients in the study group were significantly decreased.

CONCLUSIONS

Early administration of BPs after surgery did not appear to delay fracture healing time either radiologically or clinically. Furthermore, according to the changes in BMD and bone turnover markers, the anti-resorptive efficacy of BPs given immediately after surgical repair should positively affect the rate of subsequent fractures.

Delayed/non-union of upper limb fractures with bisphosphonates: systematic review and recommendations

BACKGROUND

Bisphosphonates (BPs) are widely used for the treatment of osteoporosis. Oversuppression of bone turnover with BPs may paradoxically limit the reserve capacity of bone to heal. The aim of this review was to study the predisposition of some patients to delayed/non-union of upper limb fractures associated with BPs and give recommendations on how they should be treated.

METHODS

A systematic search of two electronic databases was conducted to identify relevant studies for inclusion. All relevant studies found were included and assessed through methodology criteria predetermined by two independent reviewers.

RESULTS

Six papers comprising of three case reports, one nested case control study, one restrospective review and one randomized clinical trial were used. In comparative studies of pre-fracture BP use, a 6-day delay in average healing times was reported among BP users. There was no elevation in risk of non-union. Post-fracture BP use was associated with an approximate doubling of the risk of non-union. Timing of BP therapy initiation following a fracture was not associated with a difference in healing times. An atypical ulna fracture treated conservatively resulted in non-union, there was no effect of type of surgical treatment on distal radius fracture healing and there was insufficient evidence to comment on humeral fracture treatment.

CONCLUSIONS

Differences in union time between BP users and non-users are not significant enough to change current practice patterns and do not outweigh the benefits of BP therapy. There is no evidence to encourage early surgical management of BP-related upper limb fractures.

Healing of the bone with anti-fracture drugs

INTRODUCTION

Fracture healing is a complex process that leads to the restoration of tissue integrity through bone repair and represents a unique physiological characteristic of bone. Developing a better understanding of a fracture is essential to plan best noninvasive treatment for the patient. In osteoporosis, the patient who suffers of a fragility fracture is recommended to initiate a treatment with compounds active in preventing other low-energy skeletal trauma. Pharmaceutical industries are developing controlled clinical trials aiming to evaluate the capability of osteoporosis drugs to accelerate fracture healing.

AREAS COVERED

In preparing this review, a search was made with key words encompassing 'osteoporosis anti-fracture drugs and bone repair/healing', 'antiresorptives and bone repair/healing', 'bone-forming agents and bone repair/healing', and 'osteoporosis/anti-fracture drugs in fractures'. The results published in the area of the use of registered anti-fracture drugs to improve fracture repair and the efforts made to recommend measures for clinical outcomes in fracture healing acceleration are described in this report.

EXPERT OPINION

At present, the use of systemic pharmacological agents active to improve fracture healing by the clinicians is controversial and clinicians and scientists must do a better job in determining the methods of assessment for fracture healing.

Bisphosphonates: the first 40 years

The first full publications on the biological effects of the diphosphonates, later renamed bisphosphonates, appeared in 1969, so it is timely after 40years to review the history of their development and their impact on clinical medicine. This special issue of BONE contains a series of review articles covering the basic science and clinical aspects of these drugs, written by some of many scientists who have participated in the advances made in this field. The discovery and development of the bisphosphonates (BPs) as a major class of drugs for the treatment of bone diseases has been a fascinating story, and is a paradigm of a successful journey from 'bench to bedside'. Bisphosphonates are chemically stable analogues of inorganic pyrophosphate (PPi), and it was studies on the role of PPi as the body's natural 'water softener' in the control of soft tissue and skeletal mineralisation that led to the need to find inhibitors of calcification that would resist hydrolysis by alkaline phosphatase. The observation that PPi and BPs could not only retard the growth but also the dissolution of hydroxyapatite crystals prompted studies on their ability to inhibit bone resorption. Although PPi was unable to do this, BPs turned out to be remarkably effective inhibitors of bone resorption, both in vitro and in vivo experimental systems, and eventually in humans. As ever more potent BPs were synthesised and studied, it became apparent that physico-chemical effects were insufficient to explain their biological effects, and that cellular actions must be involved. Despite many attempts, it was not until the 1990s that their biochemical actions were elucidated. It is now clear that bisphosphonates inhibit bone resorption by being selectively taken up and adsorbed to mineral surfaces in bone, where they interfere with the action of the bone-resorbing osteoclasts. Bisphosphonates are internalised by osteoclasts and interfere with specific biochemical processes. Bisphosphonates can be classified into at least two groups with different molecular modes of action. The simpler non-nitrogen containing bisphosphonates (such as etidronate and clodronate) can be metabolically incorporated into non-hydrolysable analogues of ATP, which interfere with ATP-dependent intracellular pathways. The more potent, nitrogen-containing bisphosphonates (including pamidronate, alendronate, risedronate, ibandronate and zoledronate) are not metabolised in this way but inhibit key enzymes of the mevalonate/cholesterol biosynthetic pathway. The major enzyme target for bisphosphonates is farnesyl pyrophosphate synthase (FPPS), and the crystal structure elucidated for this enzyme reveals how BPs bind to and inhibit at the active site via their critical N atoms. Inhibition of FPPS prevents the biosynthesis of isoprenoid compounds (notably farnesol and geranylgeraniol) that are required for the post-translational prenylation of small GTP-binding proteins (which are also GTPases) such as rab, rho and rac, which are essential for intracellular signalling events within osteoclasts. The accumulation of the upstream metabolite, isopentenyl pyrophosphate (IPP), as a result of inhibition of FPPS may be responsible for immunomodulatory effects on gamma delta (γδ) T cells, and can also lead to production of another ATP metabolite called ApppI, which has intracellular actions. Effects on other cellular targets, such as osteocytes, may also be important. Over the years many hundreds of BPs have been made, and more than a dozen have been studied in man. As reviewed elsewhere in this issue, bisphosphonates are established as the treatments of choice for various diseases of excessive bone resorption, including Paget's disease of bone, the skeletal complications of malignancy, and osteoporosis. Several of the leading BPs have achieved 'block-buster' status with annual sales in excess of a billion dollars. As a class, BPs share properties in common. However, as with other classes of drugs, there are obvious chemical, biochemical, and pharmacological differences among the various BPs. Each BP has a unique profile in terms of mineral binding and cellular effects that may help to explain potential clinical differences among the BPs. Even though many of the well-established BPs have come or are coming to the end of their patent life, their use as cheaper generic drugs is likely to continue for many years to come. Furthermore in many areas, e.g. in cancer therapy, the way they are used is not yet optimised. New 'designer' BPs continue to be made, and there are several interesting potential applications in other areas of medicine, with unmet medical needs still to be fulfilled. The adventure that began in Davos more than 40 years ago is not yet over.

Use of bisphosphonates for the treatment of stress fractures in athletes

A literature review was performed to investigate the potential role of bisphosphonates for the treatment of stress fractures in athletes. Given the inhibitory action on osteoclast-mediated bone resorption, short-term suppression of bone remodeling using bisphosphonates could potentially treat stress fractures and prevent stress fractures from becoming regular fractures. To date, while there are some animal studies showing the scientific basis of bisphosphonates on stress fractures, there is still no conclusive evidence to prove any effect of bisphosphonates on stress fracture healing in humans. Further well-designed clinical trials should be carried out to establish their usefulness and safety. Until the results are available, it is prudent to limit the use of bisphosphonates for the treatment of stress fractures.

Comparison of radiographic fracture healing in the distal radius for patients on and off bisphosphonate therapy

PURPOSE

To compare healing rates of distal radius fractures in patients on bisphosphonate therapy at the time of injury to rates in those not on bisphosphonate therapy.

METHODS

A total of 196 consecutive patients treated for distal radius fractures were included in this study. Patients currently on bisphosphonate therapy at the time of injury (bisphosphonate group, n = 43) were compared to the remaining patient group (control group, n = 153). Demographic information was recorded from the patients' medical records, and radiographs were reviewed to determine fracture healing. Patients were further stratified according to age, gender, fracture complexity, type of treatment, and comorbidities. Univariate and multivariate regression were used to identify factors associated with time to radiographic fracture union.

RESULTS

The mean time to union was 55 (+/-17) days in the bisphosphonate group versus 49 (+/-14) days in the control group. Bisphosphonate use and surgical treatment were associated with a longer time to radiographic union. Bisphosphonate use was associated with increased healing times when individually controlling for age, gender, fracture complexity, or comorbidities. Bisphosphonate use was also associated with longer time to healing after adjusting for age, gender, and treatment type. Surgical fracture fixation was associated with a longer time to healing after adjusting for bisphosphonate use.

CONCLUSIONS

Current bisphosphonate use and surgical treatment were both associated with longer times to radiographic union of distal radius fractures. However, the small differences in healing times (<1 week) are not considered clinically relevant. Although further studies are needed to better define the effects of bisphosphonate therapy on fracture healing, our results suggest that bisphosphonate therapy can be continued after distal radius fractures without notable deleterious effects.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic III.

Bolus or weekly zoledronic acid administration does not delay endochondral fracture repair but weekly dosing enhances delays in hard callus remodeling

INTRODUCTION

It has been widely assumed that osteoclasts play a pivotal role during the entire process of fracture healing. Bisphosphonates (BPs) are anti-catabolic agents commonly used to treat metabolic bone diseases including osteoporosis, minimizing fracture incidence. Yet, fractures do occur in these patients and the potential for negative effects of BPs on healing has been suggested. We aimed to examine the effect of different dosing regimes of the potent BP zoledronic acid (ZA) on early endochondral fracture repair and later callus remodeling in a normal bone healing environment.

METHODS

Saline, a Bolus dose of 0.1 degrees mg/kg ZA or 5 weekly divided doses of 0.02 degrees mg/kg of ZA commenced 1 week post operatively in a rat closed fracture model. Samples at 1, 2, 4 and 6 weeks post fracture were used to analyze initial fracture union, and 12 and 26 weeks post fracture to investigate the progress of remodeling.

RESULTS

ZA did not alter the rate of endochondral fracture union. All fractures united by 6 weeks, with no difference in the progressive reduction of cartilaginous soft callus between control and treatment groups over time. ZA treatment increased hard callus bone mineral content (BMC), volume and increased callus strength at 6 and 26 weeks post fracture. Hard callus remodeling commenced at 4 weeks post fracture with Bolus ZA treatment but was delayed until after 6 weeks in the Weekly ZA group. By 12 and 26 weeks, Bolus ZA had equivalent callus content of remodeled neo-cortical bone to the Saline controls, whereas Weekly ZA remained reduced compared to Saline controls at these times (P<0.01). Callus material properties such as peak stress were significantly reduced in both ZA groups at 6 weeks. At 26 weeks, Bolus ZA-treated calluses generated peak stress equivalent to control values, whereas Weekly ZA callus peak stress remained significantly reduced, indicating remodeling delay.

CONCLUSIONS

Osteoclast inhibition with ZA does not delay endochondral fracture repair in healthy rats. Bolus ZA treatment increased net callus size and strength at 6 weeks while allowing hard callus remodeling to proceed in the long term, albeit more slowly than control. Prolonged bisphosphonate dosing during repair does not delay endochondral ossification but can significantly affect remodeling long after the drug is ceased.

Mechanisms of action of bisphosphonates: similarities and differences and their potential influence on clinical efficacy

Bisphosphonates (BPs) are well established as the leading drugs for the treatment of osteoporosis. There is new knowledge about how they work. The differences that exist among individual BPs in terms of mineral binding and biochemical actions may explain differences in their clinical behavior and effectiveness.

INTRODUCTION

The classical pharmacological effects of bisphosphonates (BPs) appear to be the result of two key properties: their affinity for bone mineral and their inhibitory effects on osteoclasts.

DISCUSSION

There is new information about both properties. Mineral binding affinities differ among the clinically used BPs and may influence their differential distribution within bone, their biological potency, and their duration of action. The antiresorptive effects of the nitrogen-containing BPs (including alendronate, risedronate, ibandronate, and zoledronate) appear to result from their inhibition of the enzyme farnesyl pyrophosphate synthase (FPPS) in osteoclasts. FPPS is a key enzyme in the mevalonate pathway, which generates isoprenoid lipids utilized for the post-translational modification of small GTP-binding proteins that are essential for osteoclast function. Effects on other cellular targets, such as osteocytes, may also be important. BPs share several common properties as a drug class. However, as with other families of drugs, there are obvious chemical, biochemical, and pharmacological differences among the individual BPs. Each BP has a unique profile that may help to explain potential clinical differences among them, in terms of their speed and duration of action, and effects on fracture reduction.

Managing osteoporosis in patients with fragility fractures: did the British Orthopaedic Association guidelines have any impact?

INTRODUCTION

The incidence of fragility fractures could double in the next 50 years. Effective treatments for osteoporosis exist and the British Orthopaedic Association (BOA) has guidelines governing how to manage underlying osteoporosis in patients with fragility fractures. This study assessed how well two trauma units treat underlying osteoporosis and whether the BOA guidelines made any impact.

PATIENTS AND METHODS

Case notes of patients with a fracture of their proximal femur admitted during January and February in 2003, 2004 and 2005 were reviewed. The results were analysed for differences between site and year.

RESULTS

A total of 602 case notes were reviewed. There was a significant difference in the number of patients discharged on osteoporosis medication between the two sites (27% at LRI, 8% at KGH; P < 0.001), but not between 2003 and 2005 (22% and 16%; P = 0.16). Of the patients started on treatment, 83% were started on calcium and/or vitamin D(3) supplements.

CONCLUSIONS

The number of patients who had their underlying osteoporosis addressed was low and the type of treatment sub-optimal. This suggests the BOA guidelines have not made an impact and further work is required to improve the management of these patients.

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

We hypothesized that ZA treatment would bolster fracture repair. In a rat model for closed fracture healing, a single dose of ZA at 0, 1, or 2 wk after fracture significantly increased BMC and strength of the healed fracture. Delaying the dose (1 or 2 wk after fracture) displayed superior results compared with dosing at the time of fracture.

INTRODUCTION

Bisphosphonates are known to increase bone strength and thus the resistance to fracture by decreasing osteoclastic bone resorption. These properties may enable bisphosphonates to also increase the strength of fracture repair. Zoledronic acid (ZA) is a potent bisphosphonate with a high affinity for bone mineral, allowing bolus intravenous dosing in a range of indications. In this study, we examined the application of bolus dose ZA in endochondral fracture repair.

MATERIALS AND METHODS

Carbon-14 labeled ZA was used in a closed rat fracture model. Rats were divided into five treatment groups (n = 25 per group): saline control, local ZA (0.01 mg/kg), and three systemic bolus ZA groups (0.1 mg/kg) with different administration times: at fracture, 1 wk after fracture, and 2 wk after fracture. Rats were killed 6 wk postoperatively. Postmortem analyses included radiography, QCT, microCT, biomechanical testing, scintillation counting, autoradiography, and histology.

RESULTS

Single-dose systemic ZA administration significantly increased callus volume, callus BMC, and mechanical strength. Perioperative treatment increased mechanical strength by 30% compared with controls (p < 0.05). Administering the systemic dose at 1 or 2 wk after fracture further increased mechanical strength compared with controls by 44% and 50%, respectively (p < 0.05). No significant differences in mechanical parameters were seen with local injection at the dose studied. Autoradiographic analysis indicated that ZA binds significantly to bone that is present at the time of administration. ZA quantification indicated that delayed administration significantly increased the uptake efficiency in the callus. Histological and microCT analysis showed that ZA treated calluses had a distinctive internal structure consisting of an intricate network of retained trabecular bone.

CONCLUSIONS

The timing of a single systemic dose of ZA plays an important role in the modulation of callus properties in this rat fracture model; delaying the single dose produces a larger and stronger callus.

Preliminary study on the effect of parenteral naloxone, alone and in association with calcium gluconate, on bone healing in an ovine "drill hole" model system

Background

Several diseases affect bone healing and physiology. Many drugs that are commonly used in orthopaedics as "analgesics" or anti-inflammatory agents impair bone healing. Stressful conditions are associated with decreased serum osteocalcin concentration. High endorphin levels alter calcium metabolism, blocking the membrane channels by which calcium normally enters cells. The consequent decrease of intracellular calcium impairs the activities of calcium-related enzymes. Naloxone is a pure opioid antagonist. Morphine-induced osteocalcin inhibition was abolished when osteoblasts were incubated with naloxone. Naloxone restored the altered cellular and tissue physiology by removing β-endorphins from specific receptors. However, this is only possible if the circulating Ca concentration is adequate. The aim of the present study was to evaluate the efficacy of parenteral naloxone administration in inducing fast mineralization and callus remodelling in a group of sheep with a standardised bone lesion.

Methods

Twenty ewes were randomly assigned to 4 treatment groups. Group A acted as control, group B received a solution of calcium gluconate, group C a solution of naloxone, and group D a solution of calcium gluconate and naloxone. A transverse hole was drilled in the left metacarpus, including both cortices, then parenteral treatment was administered intramuscularly, daily for four weeks. Healing was evaluated by weekly radiographic examination for eight weeks. For quantitative evaluation, the ratio of the radiographic bone density between the drill area and the adjacent cortical bone was calculated. After eight weeks the sheep were slaughtered and a sample of bone was collected for histopathology

Results

Group D showed a higher radiographic ratio than the other groups. Sheep not treated with naloxone showed a persistently lower ratio in the lateral than the medial cortex (P < 0.01). Histopathology of bone samples showed more caverns and fewer osteoblasts in group D than in the other groups (P ≤ 0.001).

Conclusion

A low-dose parenteral regimen of naloxone enhances mineralization and remodelling of the callus in healing cortical defects in sheep, especially if associated with calcium gluconate.

Bisphosphonates: mode of action and pharmacology

The profound effects of the bisphosphonates on calcium metabolism were discovered over 30 years ago, and they are now well established as the major drugs used for the treatment of bone diseases associated with excessive resorption. Their principal uses are for Paget disease of bone, myeloma, bone metastases, and osteoporosis in adults, but there has been increasing and successful application in pediatric bone diseases, notably osteogenesis imperfecta. Bisphosphonates are structural analogues of inorganic pyrophosphate but are resistant to enzymatic and chemical breakdown. Bisphosphonates inhibit bone resorption by selective adsorption to mineral surfaces and subsequent internalization by bone-resorbing osteoclasts where they interfere with various biochemical processes. The simpler, non-nitrogen-containing bisphosphonates (eg, clodronate and etidronate) can be metabolically incorporated into nonhydrolysable analogues of adenosine triphosphate (ATP) that may inhibit ATP-dependent intracellular enzymes. In contrast, the more potent, nitrogen-containing bisphosphonates (eg, pamidronate, alendronate, risedronate, ibandronate, and zoledronate) inhibit a key enzyme, farnesyl pyrophosphate synthase, in the mevalonate pathway, thereby preventing the biosynthesis of isoprenoid compounds that are essential for the posttranslational modification of small guanosine triphosphate (GTP)-binding proteins (which are also GTPases) such as Rab, Rho, and Rac. The inhibition of protein prenylation and the disruption of the function of these key regulatory proteins explains the loss of osteoclast activity. The recently elucidated crystal structure of farnesyl diphosphate reveals how bisphosphonates bind to and inhibit at the active site via their critical nitrogen atoms. Although bisphosphonates are now established as an important class of drugs for the treatment of many bone diseases, there is new knowledge about how they work and the subtle but potentially important differences that exist between individual bisphosphonates. Understanding these may help to explain differences in potency, onset and duration of action, and clinical effectiveness.

Effects of ibandronate on bone quality: preclinical studies

Osteoporosis is a skeletal disorder characterized by low bone mass and deterioration of bone microarchitecture resulting in bone fragility, which increases the risk of fracture. The clinical efficacy of bisphosphonates is evaluated through improvements in bone mineral density (BMD) and reductions in the risk for fracture. However, as bisphosphonates are administered long term, there is increasing interest in their effects on bone quality, which includes bone mass, strength and architecture. Ibandronate is a potent, nitrogen-containing bisphosphonate with significant antifracture efficacy when administered daily and in regimens with extended between-dose intervals. Clinical studies with ibandronate are supported by an extensive preclinical program that investigated the efficacy and bone safety of ibandronate in various animal models of osteoporosis. In preclinical studies, treatment with ibandronate maintained, or improved the quality, strength and architecture of bone. Intermittent and daily ibandronate regimens provided similar benefits. During ibandronate treatment, the bone retains its capacity for repair and bone mineralization is not adversely affected. Notably, positive relationships among BMD, bone strength and bone architecture have been demonstrated. This review describes the preclinical evidence for the preservation of bone quality with ibandronate, irrespective of the dosing regimen and even when administered at doses higher than those used therapeutically.

Treating osteoporosis with bisphosphonates and addressing adherence: a review of oral ibandronate

Osteoporosis is a common, chronic condition, affecting approximately half of all postmenopausal Caucasian women in the US. Vertebral fractures occur as a result of osteoporosis and lead to increased hospitalisation and mortality, and adversely affect patient quality of life. The burden of osteoporosis on healthcare systems is expected to rise as the elderly population continues to grow. Yet there are many medications for preventing and treating osteoporosis. Oral bisphosphonates are first-line treatment for osteoporosis, with demonstrated efficacy in increasing bone mineral density and reducing bone turnover, which reduces the incidence of fractures. However, adherence to medication is suboptimal, with approximately 40% of patients discontinuing treatment within 6 months. Recent reports have suggested simplifying the dosage regimen as a strategy to help address this issue. Ibandronate is a potent, nitrogen-containing bisphosphonate which is administered once-monthly. Preclinical studies initially revealed the feasibility of extending the between-dose interval. Subsequent clinical studies have provided further evidence of the positive effects of extended-interval ibandronate administration in reducing the risk of vertebral fractures through increasing bone mineral density and reducing bone turnover without compromising bone quality. These studies have also demonstrated that ibandronate has a safety profile similar to placebo. Ibandronate has recently been approved for use in the US to treat postmenopausal osteoporosis. This review summarises the efficacy and safety of once-monthly oral ibandronate and discusses the implications of such a treatment in primary care in the US.

Ibandronate: pharmacology and preclinical studies

Over the past three decades, changes to the chemical structures of the bisphosphonates have resulted in progressive improvements in their antiresorptive potencies. Ibandronate is a potent, nitrogen-containing bisphosphonate that possesses a tertiary nitrogen group on its R2 side chain and a hydroxyl group on its R1 side chain, which together confer one of the highest antiresorptive potencies of all bisphosphonates. In common with other nitrogen-containing bisphosphonates, ibandronate is a strong inhibitor of farnesyl pyrophosphate synthase, which probably accounts for its major effects on osteoclast activity. In addition, it binds strongly to hydroxyapatite. The pharmacological efficacy and safety of various continuous and intermittent regimens of ibandronate have been extensively investigated in experimental models of osteoporosis in several animal species, including rats, dogs, and monkeys. In ovariectomized (OVX) rats, intermittent (dosing interval 2, 4, and 6 weeks) and continuous ibandronate regimens provided equivalent results per total dose irrespective of the dosing regimen. Similar results were obtained in OVX dogs and monkeys. High doses of ibandronate many times those used therapeutically were well tolerated and did not impair bone quality or mineralization in rats. Moreover, bone mass, architecture, and strength were maintained or improved, and bone healing was not adversely affected in animal models, regardless of whether ibandronate was administered intermittently or daily. The findings from all these studies demonstrate the efficacy and safety of intermittent ibandronate regimens and support the development of such regimens for the clinical management of postmenopausal osteoporosis.

Bisphosphonates: From Bench to Bedside

The discovery and development of the bisphosphonates (BPs) as a major class of drugs for the treatment of bone diseases has been a fascinating journey that is still not over. In clinical medicine, several BPs are established as the treatments of choice for various diseases of excessive bone resorption, including Paget's disease of bone, myeloma and bone metastases, and osteoporosis. Bisphosphonates are chemically stable analogues of inorganic pyrophosphate, and are resistant to breakdown by enzymatic hydrolysis. Bisphosphonates inhibit bone resorption by being selectively taken up and adsorbed to mineral surfaces in bone, where they interfere with the action of the bone-resorbing osteoclasts. Bisphosphonates are internalized by osteoclasts and interfere with specific biochemical processes. Bisphosphonates can be classified into at least two groups with different molecular modes of action. The simpler non-nitrogen-containing bisphosphonates (such as clodronate and etidronate) can be metabolically incorporated into nonhydrolyzable analogues of adenosine triphosphate (ATP) that may inhibit ATP-dependent intracellular enzymes. The more potent, nitrogen-containing bisphosphonates (such as pamidronate, alendronate, risedronate, ibandronate, and zoledronate) are not metabolized in this way but can inhibit enzymes of the mevalonate pathway, thereby preventing the biosynthesis of isoprenoid compounds that are essential for the posttranslational modification of small GTP-binding proteins (which are also GTPases) such as rab, rho, and rac. The inhibition of protein prenylation and the disruption of the function of these key regulatory proteins explain the loss of osteoclast activity and induction of apoptosis. The key target for bisphosphonates is farnesyl pyrophosphate synthase (FPPS) within osteoclasts, and the recently elucidated crystal structure of this enzyme reveals how BPs bind to and inhibit at the active site via their critical N atoms. In conclusion, bisphosphonates are now established as an important class of drugs for the treatment of many bone diseases, and their mode of action is being unraveled. As a result their full therapeutic potential is gradually being realized.

Ibandronate treatment for osteoporosis: rationale, preclinical, and clinical development of extended dosing regimens

Ibandronate is a potent nitrogen-containing bisphosphonate available as a once-monthly oral formulation for the treatment and prevention of osteoporosis. Preclinical experiments with estrogen-depleted rats, dogs, and monkeys demonstrated the efficacy of daily and intermittent ibandronate dosing. Initial clinical trials explored the optimal dosing regimens for oral administration in humans. The Oral Ibandronate Osteoporosis Vertebral Fracture Trial in North America and Europe (BONE) and Monthly Oral Ibandronate in Ladies (MOBILE) trials demonstrated that long-term daily and intermittent administration of ibandronate was efficacious for increasing bone mineral density, reducing markers of bone turnover, and preventing fractures, while maintaining bone quality. These preclinical and clinical ibandronate trials provided progressive evidence that a simple, long interval dosing regimen could offer efficacy and safety comparable with currently available bisphosphonates. It is anticipated that once-monthly ibandronate may have a positive impact on patient adherence, and ultimately, on fracture protection in osteoporotic women.

Ibandronate: the evolution of a once-a-month oral therapy for postmenopausal osteoporosis

Bisphosphonates have been shown to be highly effective in preventing and treating postmenopausal osteoporosis (PMO) and the associated risk of fracture. However, poor adherence with bisphosphonate therapies for PMO results in a high incidence of otherwise preventable fractures. The chronicity of this condition requires long-term treatment, but fewer than one in two women remains on daily bisphosphonate therapy for 1 yr. A good way to reduce the risk of osteoporotic fractures is through development of equally efficacious formulations with more convenient dosing regimens. Weekly formulations of bisphosphonates have been introduced that demonstrate comparable efficacy to daily formulations with slightly improved adherence. Recently, a new formulation utilizing a third-generation nitrogen-containing bisphosphonate--ibandronate--has been approved with a monthly dosing regimen. The pharmacokinetics and high potency of ibandronate, similar with other bisphosphonates, facilitate lower mg doses and longer-interval dosing frequencies with similar efficacy and enhanced tolerability. Preclinical studies and clinical trials have consistently demonstrated that it is the total cumulative dose of ibandronate that determines efficacy. The convenience of once-monthly dosing may ultimately improve adherence and clinical outcomes among the growing population of postmenopausal women at risk of osteoporosis.

Oral ibandronate: a less frequently administered therapeutic option for postmenopausal osteoporosis

Osteoporosis is a severe condition, associated with significant disability as a result of fragility fractures and increased mortality. Oral bisphosphonates effectively reduce the risk of osteoporotic fracture and are generally well tolerated. Unfortunately, patient outcomes are often compromised by suboptimal therapeutic adherence. In other disease areas, reduced dosing frequency has been shown to improve therapeutic adherence. A positive impact for adherence has been observed with a reduction in the bisphosphonate dosing frequency from daily to weekly. However, overall adherence remains suboptimal. Ibandronate is a potent nitrogen-containing bisphosphonate specifically designed for less frequent than weekly administration, without compromise for efficacy or tolerability. This article reviews the pharmacology, efficacy and tolerability of oral ibandronate when administered with extended dosing intervals in postmenopausal osteoporosis.