No adverse effects of clodronate on fracture healing in rats

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.

The Effect of Bisphosphonates on Fracture Healing Time and Changes in Bone Mass Density: A Meta-Analysis

BACKGROUND

Osteoporosis is a common complication of acute fracture, which can lead to fracture delayed union or other complications and resulting in poor fracture healing. Bisphosphate is a common anti-osteoporosis drug, but its application in fracture patients is still controversial because of its inhibitory effect on bone resorption.

METHOD

Studies were acquired from literature databases in accordance with established inclusion criteria. Standard mean difference (SMD) and 95% confidence intervals (Cls) were calculated to evaluate the effectiveness of the bisphosphonates treatment in fracture patients. Data analysis was conducted with the Review Manager 5.4.1 software.

RESULTS

A total of 16 studies involving 5022 patients obtained from selected databases were examined. As expected, bisphosphate had no significant effect on fracture healing time, but it could significantly increase BMD and prevent osteoporosis. Meanwhile, bisphosphate can inhibit both bone resorption and bone formation markers, resulting in low bone turnover state.

CONCLUSION

This meta-analysis showed that bisphosphonate have no significant effect on fracture healing time but they do increase the changes in BMD and reduce bone synthesis and resorption markers. Early application of bisphosphonates after injury in the appropriate patient population should be considered.

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.

Tiludronate and clodronate do not affect bone structure or remodeling kinetics over a 60 day randomized trial

Background

Tiludronate and clodronate are FDA-approved bisphosphonate drug therapies for navicular disease in horses. Although clinical studies have determined their ability to reduce lameness associated with skeletal disorders in horses, data regarding the effect on bone structure and remodeling is lacking. Additionally, due to off-label use of these drugs in young performance horses, effects on bone in young horses need to be investigated. Therefore, the purpose of this randomized, experimental pilot study was to determine the effect of tiludronate and clodronate on normal bone cells, structure and remodeling after 60 days in clinically normal, young horses. Additionally, the effect of clodronate on bone healing 60 days after an induced defect was investigated.

Results

All horses tolerated surgery well, with no post-surgery lameness and all acquired biopsies being adequate for analyses. Overall, tiludronate and clodronate did not significantly alter any bone structure or remodeling parameters, as evaluated by microCT and dynamic histomorphometry. Tiludronate did not extensively impact bone formation or resorption parameters as evaluated by static histomorphometry. Similarly, clodronate did not affect bone formation or resorption after 60 days. Sixty days post-defect, healing was minimally affected by clodronate.

Conclusions

Tiludronate and clodronate do not appear to significantly impact bone tissue on a structural or cellular level using standard dose and administration schedules.

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.

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.

Earlier effect of alendronate in mouse metaphyseal versus diaphyseal bone healing

Healing of injured cancellous bone is characterized by a transient stage of rapid bone formation throughout the traumatized bone volume, often followed by similarly rapid resorption. This is different from the slower diaphyseal healing via an external callus. We, therefore, hypothesized that antiresorptive treatment might have an earlier positive effect in cancellous bone healing than in diaphyseal fractures. One hundred and twenty-three male C57bl6 mice received either an internally stabilized diaphyseal osteotomy of the femur or a screw inserted into the tibial metaphysis. The mice were randomized to daily alendronate injections (200 μg/kg/day), or control injections, and killed for mechanical testing after 14, 21, or 28 days. The hypothesis was tested by a three-way Anova (time, site, and drug). The ultimate force was increased by bisphosphonate treatment in both models. There was a significant interaction between time, site, and drug (p < 0.001) so that the full positive effect of alendronate was evident in the metaphysis at 14 days, but first after 28 days in the diaphysis. While the early effect in the metaphysis might be translated into earlier healing, the late effect in the diaphysis was due to delayed remodeling of the callus, which might have less clinical importance. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:793-799, 2017.

Zoledronic acid suppresses callus remodeling but enhances callus strength in an osteoporotic rat model of fracture healing

MINI-ABSTRACT

In this study, we demonstrated that the use of zoledronic acid does not impair fracture healing, but results in superior callus size and resistance at the fracture site, which could be the consequence of a lower rate of bone turnover due to its anti-catabolic effect.

OBJECTIVE

To investigate the effect of inhibition of bone remodeling by the bisphosphonate, zoledronic acid, on callus properties in an osteoporotic rat model of fracture healing.

METHODS

Ovariectomized (OVX) rats were randomly divided into four treatment groups (n=24 per group): saline control (CNT); and three systemic zoledronic acid-injected groups (0.1mg/kg), administered 1 day (ZOLD1), 1 week (ZOLW1), and 2 weeks (ZOLW2) after fracture. Rats were killed at either 6 or 12 weeks postoperatively. Postmortem analyses included radiography, microcomputed tomography, histology, histomorphometry, biomechanical tests, and nanoindentation tests.

RESULTS

Treatment with zoledronic acid led to a significant increase in trabecular bone volume within the callus, as well as in callus resistance, compared to those in the saline control rats; delayed administration (ZOLW2) reduced intrinsic material properties, including ultimate stress and elastic modulus, and microarchitecture parameters, including bone volume/total volume (BV/TV), trabecular thickness (Tb.Th), and connectivity density (Conn.D), compared with ZOLD1 at 12 weeks after surgery. OVX had a negative effect on the progression of endochondral ossification at 6 weeks. Zoledronic acid administration at an early stage following fracture may bind to early callus, and thus not affect subsequent callus formation and endochondral ossification, while delayed administration (ZOLW2) mildly suppresses bony callus remodeling.

CONCLUSION

The superior results obtained with zoledronic acid (ZOLD1, ZOLW1, and ZOLW2) compared to CNT in terms of callus size and resistance could be the consequence of a lower rate of bone turnover at the fracture site due to the anti-catabolic effect of zoledronic acid. Mild suppression of callus remodeling by delayed administration did not impair the initial phase of the fracture healing process.

Bone augmentation using a new injectable bone graft substitute by combining calcium phosphate and bisphosphonate as composite--an animal model

Objective

The aim of this study was to create a new injectable bone graft substitute by combining the features of calcium phosphate and bisphosphonate as a composite bone graft to support bone healing and to evaluate the effect of alendronate to the bone healing process in an animal model.

Material and method

In this study, 24 New Zealand white rabbits were randomly divided into two groups: a calcium phosphate alendronate group and a calcium phosphate control group. A defect was created at the proximal medial tibia and filled with the new created injectable bone graft substitute calcium phosphate alendronate or with calcium phosphate. Healing process was documented by fluoroscopy. To evaluate the potential of the bone graft substitute, the proximal tibia was harvested 2, 4, and 12 weeks after operation. Histomorphological analysis was focused on the evaluation of the dynamic bone parameters using the Osteomeasure system.

Results

Radiologically, the bone graft materials were equally absorbed. No fracture was documented. The bones healed normally. After 2 weeks, the histological analysis showed an increased new bone formation for both materials. The osteoid volume per bone volume (OV/BV) was significantly higher for the calcium phosphate group. After 4 weeks, the results were almost equal. The trabecular thickness (Tb.Th) increased in comparison to week 2 in both groups with a slight advantage for the calcium phosphate group. The total mass of the bone graft (KEM.Ar) and the bone graft substitute surface density (KEM.Pm) were consistently decreasing. After 12 weeks, the new bone volume per tissue volume (BV/TV) was still constantly growing. Both bone grafts show a good integration. New bone was formed on the surface of both bone grafts. The calcium phosphate as well as the calcium phosphate alendronate paste had been enclosed by the bone. The trabecular thickness was higher in both groups compared to the first time point.

Conclusion

Calcium phosphate proved its good potential as a bone graft substitute. Initially, the diagrams seem to show a tendency that alendronate improves the known properties of calcium phosphate as a bone graft substitute. The composite graft induced a good and constant new bone formation. Not only the graft was incorporated into the bone but also a new bone was formed on its surface. But we could not prove a significant difference between the grafts. Both implants proved their function as a bone graft substitute, but the bisphosphonate alendronate does not support the bone healing process sufficiently that the known properties of calcium phosphate as a bone graft substitute were improved in the sense of a composite graft. In this study, alendronate used as a bone graft in a healthy bony environment did not influence the bone healing process in a positive or negative way.

Use of risedronate for consolidation and callus formation in Colles fractures in postmenopausal women: SOLID study

OBJECTIVE

This open, randomized and blinded parallel-group multicenter study evaluated the efficacy of Actonel(®) (35 mg) plus calcium/vitamin D versus calcium/vitamin D alone for preserving bone mineral density (BMD) in postmenopausal women with Colles fractures.

METHODS

Patients with a Colles fracture for seven days were randomized to receive either Actonel(®) (35 mg) once a week plus calcium/vitamin D (ACD group) or calcium/vitamin D alone (CD group). The patients were evaluated after 90 and 180 days of treatment.

RESULTS

59 ACD patients and 56 CD patients completed all the evaluations. At the end of the study, the BMD of the radius at the fracture location showed a negative change in the CD group (32.8%). The loss of BMD in the ACD group (20.8%) was slightly less than that in the CD group. There was a difference in the proportions of patients with BMD losses at the end of the study period in the two treatment groups, in favor of the ACD group, although this was not statistically significant. There was no significant difference in radiological identification of callus formation between the treatment groups. In the majority of the patients, the callus could be radiologically identified after 90 days.

CONCLUSION

Postmenopausal women with Colles fractures who received risedronate sodium plus calcium/vitamin D did not show any significant difference in BMD loss in forearm fractures, in comparison with those who received calcium/vitamin D alone. Risedronate presented a tendency toward a protective effect regarding BMD loss due to immobilization. The time taken for fracture consolidation to be achieved was unaffected.

Curettage and reconstruction by the sandwich technique for giant cell tumours around the knee

PURPOSE

To evaluate outcomes of 36 patients who underwent curettage, use of phenol, and reconstruction using the sandwich technique for giant cell tumour (GCT) of bone around the knee.

METHODS

22 women and 14 men aged 19 to 46 (mean, 29.6) years underwent intralesional curettage, use of phenol, and reconstruction using the sandwich technique for GCT of the proximal tibia (n=23) or distal femur (n=13). Two of the cases were recurrences. Two, 18, and 16 tumours were classified as grade I, grade II, and grade III, respectively. Five of the grade III tumours were associated with an extra-articular pathological fracture. Patients underwent intralesional curettage, use of phenol, and reconstruction with allograft, gel foam, and cement (the sandwich technique). Pathological fractures were fixed with plates. Functional outcome was evaluated using the Musculoskeletal Tumor Society (MSTS) score.

RESULTS

The mean follow-up period was 5 (2.5-11) years. The mean MSTS score was 27.7 out of 30 (standard deviation, 3; range, 16-30). One patient with a grade III tumour in the proximal tibia had a recurrence detected elsewhere after 3 years. Her MSTS score at 2 years was 26. No patient had malignant transformation.

CONCLUSION

Intralesional curettage, use of phenol, and reconstruction with allograft, gel foam, and cement (the sandwich technique) for GCT of bone achieved good functional outcome and a low recurrence rate.

Anti-osteoporosis therapy and fracture healing

BACKGROUND

A number of medications are approved for treatment of osteoporosis. As mode of action usually is anti-catabolic/anti-resorptive or anabolic, it is of interest to know whether these drugs affect not only normal bone remodeling, but also fracture healing.

OBJECTIVE

The purpose of this paper is to give a short overview of the potential effect of various anti-osteoporotic medication on fracture healing.

METHODS

A narrative literature review was performed to describe the current knowledge.

RESULTS

Anti-catabolic/anti-resorptive drugs: for bisphosphonates, the most common class of drugs in this group, experimental studies have shown a larger and stronger callus and delayed remodeling but no evidence of delayed healing. A human monoclonal antibody to RANKL is another anti-catabolic drug, with the only report to date showing enhanced healing in an animal model. Strontium ranelate is a drug where both anti-catabolic and a weak anabolic effect have been proposed, with experimental data ranging from no effect to significant increase in both callus volume and strength. Anabolic drugs: PTH has demonstrated accelerated healing of various experimental fractures and of distal radius and pelvic fractures in humans. While the exact mechanism is not fully understood, PTH results in increased recruitment and differentiation of chondrocytes and enhancement of endochondral ossification. A monoclonal antibody to block sclerostin is another potential anabolic pathway, where animal data have shown increase in bone mass and strength. The potential effect on fracture healing is yet to be studied.

CONCLUSION

There are still large gaps in the understanding of the potential effect of anti-osteoporotic drugs on fracture healing, although based on present knowledge a recent or present fracture should not be considered as a contraindication to such treatment.

Effect of early administration of alendronate after surgery for distal radial fragility fracture on radiological fracture healing time

This multicentre prospective clinical trial aimed to determine whether early administration of alendronate (ALN) delays fracture healing after surgical treatment of fractures of the distal radius. The study population comprised 80 patients (four men and 76 women) with a mean age of 70 years (52 to 86) with acute fragility fractures of the distal radius requiring open reduction and internal fixation with a volar locking plate and screws. Two groups of 40 patients each were randomly allocated either to receive once weekly oral ALN administration (35 mg) within a few days after surgery and continued for six months, or oral ALN administration delayed until four months after surgery. Postero-anterior and lateral radiographs of the affected wrist were taken monthly for six months after surgery. No differences between groups was observed with regard to gender (p = 1.0), age (p = 0.916), fracture classification (p = 0.274) or bone mineral density measured at the spine (p = 0.714). The radiographs were assessed by three independent assessors. There were no significant differences in the mean time to complete cortical bridging observed between the ALN group (3.5 months (SE 0.16)) and the no-ALN group (3.1 months (SE 0.15)) (p = 0.068). All the fractures healed in the both groups by the last follow-up. Improvement of the Quick-Disabilities of the Arm, Shoulder and Hand (QuickDASH) score, grip strength, wrist range of movement, and tenderness over the fracture site did not differ between the groups over the six-month period. Based on our results, early administration of ALN after surgery for distal radius fracture did not appear to delay fracture healing times either radiologically or clinically.

Early initiation of bisphosphonate does not affect healing and outcomes of volar plate fixation of osteoporotic distal radial fractures

BACKGROUND

Bisphosphonates can adversely affect fracture-healing because they inhibit osteoclastic bone resorption. It is unclear whether bisphosphonates can be initiated safely for patients who have sustained an acute distal radial fracture. The purpose of this randomized study was to determine whether the early use of bisphosphonate affects healing and outcomes of osteoporotic distal radial fractures treated with volar locking plate fixation.

METHODS

Fifty women older than fifty years of age who had undergone volar locking plate fixation of a distal radial fracture and had been diagnosed with osteoporosis were randomized to Group I (n = 24, initiation of bisphosphonate treatment at two weeks after the operation) or Group II (n = 26, initiation of bisphosphonate treatment at three months). Patients were assessed for radiographic union and other radiographic parameters (radial inclination, radial length, and volar tilt) at two, six, ten, sixteen, and twenty-four weeks, and for clinical outcomes that included Disabilities of the Arm, Shoulder and Hand (DASH) scores, wrist motion, and grip strength at twenty-four weeks. The two groups were compared with regard to the time to radiographic union, the radiographic parameters, and the clinical outcomes.

RESULTS

No significant differences were observed between the two groups with respect to radiographic or clinical outcomes after volar locking plate fixation. All patients obtained fracture union, and the mean times to radiographic union in Groups I and II were similar (6.7 and 6.8 weeks, respectively; p = 0.65). Furthermore, the time to radiographic union was not related to osteoporosis severity or fracture type.

CONCLUSIONS

In patients with an osteoporotic distal radial fracture treated with volar locking plate fixation, the early initiation of bisphosphonate treatment did not affect fracture-healing or clinical outcomes.

LEVEL OF EVIDENCE

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

The effect of bisphosphonate and intermittent human parathyroid hormone 1-34 treatments on cortical bone allografts in rabbits

AIM

This study compares the effect of bisphosphonate and intermittent PTH administration on haversian remodeling in cortical bone allografts in rabbits.

MATERIALS AND METHODS

An intercalary heat-treated cortical bone allograft was applied to a segment skeletal defect in the left femur of Japanese white rabbits. The rabbits were randomly assigned to one of three groups: the vehicle control group (CNT); the bisphosphonate group (B group); and the intermittent PTH treatment group (P group). Periodic radiographic evaluation was performed and peripheral quantitative computerized tomography (pQCT) was used to evaluate the total bone area (Area), bone mineral density (BMD), and bone mineral content (BMC). The allografts also underwent histological examination.

RESULTS

The P group was radiographically superior in the latter stage, compared with the other groups. pQCT analysis of the allografts showed that the B group had a significantly higher Area and BMC. These parameters in the latter stage were significantly lower in the P group than in the other groups. The allograft of the B group was histologically mostly necrotic bone, whereas allograft of the P group showed abundant newly formed bone.

CONCLUSION

In rabbits, bisphosphonate prevents resorption, but suppresses remodeling and incorporation; by contrast, PTH increases resorption and accelerates allograft remodeling and incorporation. Based on our preliminary data, we suggest that further research on the manner of administration of bisphosphonate and PTH - which have contrasting effects - can be beneficial in maintaining bone strength and in regulating remodeling and allograft incorporation.

The influence of macrophage depletion on ligament healing

Despite a complex cascade of cellular events to reconstruct damaged extracellular matrix (ECM), ligament healing results in a mechanically inferior, scar-like tissue. During normal healing, the number of macrophages significantly increases within the wound site. Then, granulation tissue expands into any residual, normal ligamentous tissue (creeping substitution), resulting in a larger region of healing, greater mechanical compromise, and an inefficient repair process. To study the effects of macrophages on the repair process, bilateral, surgical rupture of their medial collateral ligaments (MCLs) was done on rats. Treatment animals received liposome-encapsulated clodronate, 2 days before rupture to ablate phagocytosing macrophages. Ligaments were then collected at days 5, 11, and 28 for immunohistochemistry (IHC) and/or mechanical testing. Clodronate treatment reduced both the M1 and M2 macrophages at day 5 and altered early healing. However, the macrophages effectively returned to control levels after day 5 and reinitiated a wound-healing response. Our results suggest that an early macrophage response, which is necessary for debridement of damaged tissue in the wound, is also important for cytokine release to mediate normal repair processes. Additionally, nonspecific inhibition of macrophages (without regard to specific macrophage populations) can control excessive granulation tissue formation but is detrimental to early matrix formation and ligament strength.

The effect of zoledronate during bone healing

Background

Bisphosphonates have become the treatment of choice for a variety of bone diseases in which excessive osteoclastic activity is an important pathologic feature. However, inhibition of osteoclastic activity could lead to inhibition of remodeling during bone healing or repair. The objective of this study is to investigate the effect of zoledronate (the most potent bisphosphonate) in the biological process of bone healing.

Methods

Thirty immature male rabbits were divided into two groups (control and experimental) of 15 animals each. Both groups were submitted to fibular osteotomy. Only in the experimental group a single dose of zoledronate was administered. After 1, 2, and 4 weeks, animals of both groups were euthanized and the osteotomy site was histomorphometrically evaluated. The associated parameters analyzed were tissue volume (TV), fractional trabecular bone volume (BV/TV), fractional woven bone volume (WoV/TV), fractional periosteal fibrous volume (FbV/TV), and medullary fibrous volume (MaV/TV).

Results

The first week of healing was characterized by small callus area (experimental group) and less periosteal fibrosis. The second week was characterized by a large quantity of woven bone and marked decrease in periosteal fibrosis in the two groups. In the control group there was also a significant increase in trabecular bone. The fourth week was characterized by increased amount of woven bone and trabecular bone in the experimental group; there was increased medullary fibrosis in the two groups, while there continued to be significantly less periosteal fibrosis in the experimental group.

Conclusions

Zoledronate does not prevent bone healing. However, the effect of zoledronate was characterized by accentuated stimulation of primary bone production and probably inhibition of remodeling, leading to retention of trabecular bone.

The Early Effects of Intramedullary Reaming of the Femur on Bone Mineral Density; an Experimental Study in Pigs

Background and Aims:

Both fracture and fracture treatment affect bone mineral density (BMD). BMD after standard intramedullary reaming of the femoral cavity and after reaming with a reamer-irrigator-aspirator (RIA) system were studied with the hypothesis that the RIA technique would lead to lower BMD levels.

Material and Methods:

Dual-energy X-ray absorptiometry (DXA) was performed on the third day after operation with standard intramedullary nailing technique (n = 6)or RIA technique (n = 7) in intact femora of young Norwegian landrace pigs.

Results and conclusion:

Significantly lower BMD were found in the mid-shaft and total femur after reaming with the RIA technique compared to the non-operated femur. Traditional reaming technique resulted in significantly higher BMD in the distal femur.

Interpretation:

The results of this study indicate that standard reaming increased BMD in the distal femur, suggesting compressive effects on trabecular bone. The RIA technique decreased BMD in the femoral diaphysis and total femur, suggesting removal of trabecular bone. A possible clinical impact of the findings remains to be investigated.

Zoledronate reduces unwanted bone resorption in intercalary bone allografts

Bone allografts are often hampered by graft incorporation and poor host bone formation. Bisphosphonates, synthetic pyrophosphate analogs, have shown promise in inhibiting bone resorption in human and animal trials. Some in vitro studies have suggested that high dose bisphosphonate may also inhibit bone formation, leading to our hypothesis that an ideal dose of bisphosphonate in allografts could protect allografts from resorption. We transplanted intercalary allografts in to the segmental defect of the rat femurs after soaking each allograft in zoledronate solution (30 microM) and then analysed bone density of the allografts six to 12 weeks after transplantation. At six and 12 weeks, the bone mineral density was higher in the experimental group compared with the control group. Qualitative radiographic and histological analysis also revealed more allograft resorption in the control group than in the zoledronate-treated group. Our data indicate that pharmacological modification of intercalary allografts with zoledronate solution can decrease osteoclast-mediated allograft resorption.

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.

The effect of zoledronate on bone remodeling during the healing process

PURPOSE

To check the effect of zoledronate in bone remodeling during bone healing.

METHODS

Thirty rabbits were divided into two groups of fifteen animals each (control and experimental group respectively). Shaft osteotomy was performed on the cranial portion of the fibula of each animal. In the experimental group, a single dose of 0.04mg/kg of zoledronate was administered. In the control group, the same volume of bi-distilled water was administered. After one, two and four weeks, animals of both groups were killed and histological sections of the fibular metaphyseal area were examined histomorphometrically. The parameters analyzed were tissue volume (TV), fractional trabecular bone volume (BV/TV) and fractional medullary fibrous volume (FbV/TV).

RESULTS

Tissue volume increased in the experimental group (237.2mm(2).10-2) compared to the control (166.62mm(2).10-2). Trabecular bone volume was significantly larger in the experimental (60.2%) than in the control group (34.8%). The amount of fibrosis volume decreased in the experimental group (22%) compared to the control (49.4%).

CONCLUSION

The effect of zoledronate is characterized by accentuated stimulus of bone formation in the metaphyseal area, resulting in a larger amount of trabecular bone volume and little fibrosis volume.

Receptor activator of nuclear factor kappaB ligand and osteoprotegerin regulation of bone remodeling in health and disease

Osteoclasts and osteoblasts dictate skeletal mass, structure, and strength via their respective roles in resorbing and forming bone. Bone remodeling is a spatially coordinated lifelong process whereby old bone is removed by osteoclasts and replaced by bone-forming osteoblasts. The refilling of resorption cavities is incomplete in many pathological states, which leads to a net loss of bone mass with each remodeling cycle. Postmenopausal osteoporosis and other conditions are associated with an increased rate of bone remodeling, which leads to accelerated bone loss and increased risk of fracture. Bone resorption is dependent on a cytokine known as RANKL (receptor activator of nuclear factor kappaB ligand), a TNF family member that is essential for osteoclast formation, activity, and survival in normal and pathological states of bone remodeling. The catabolic effects of RANKL are prevented by osteoprotegerin (OPG), a TNF receptor family member that binds RANKL and thereby prevents activation of its single cognate receptor called RANK. Osteoclast activity is likely to depend, at least in part, on the relative balance of RANKL and OPG. Studies in numerous animal models of bone disease show that RANKL inhibition leads to marked suppression of bone resorption and increases in cortical and cancellous bone volume, density, and strength. RANKL inhibitors also prevent focal bone loss that occurs in animal models of rheumatoid arthritis and bone metastasis. Clinical trials are exploring the effects of denosumab, a fully human anti-RANKL antibody, on bone loss in patients with osteoporosis, bone metastasis, myeloma, and rheumatoid arthritis.

Pharmacological agents and impairment of fracture healing: what is the evidence?

Bone healing is an extremely complex process which depends on the coordinated action of several cell lineages on a cascade of biological events, and has always been a major medical concern. The use of several drugs such as corticosteroids, chemotherapeutic agents, non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics, anticoagulants and drugs which reduce osteoclastic activity have been shown to affect bone healing. This review article presents our current understanding on this topic, focusing on data illustrating the effect of these drugs on fracture healing and bone regeneration.

The effects of RANKL inhibition on fracture healing and bone strength in a mouse model of osteogenesis imperfecta

Currently, the standard treatment for osteogenesis imperfecta (OI) is bisphosphonate therapy. Recent studies, however, have shown delayed healing of osteotomies in a subset of OI patients treated with such agents. The current study sought to determine the effects of another therapy, RANKL inhibition, on bone healing and bone strength in the growing oim/oim mouse, a model of moderate to severe OI. Mice [73 oim/oim and 69 wild-type (WT)] were injected twice weekly with either soluble murine RANK (RANK-Fc) (1.5 mg/kg) or saline beginning at 6 weeks of age. At 8 weeks of age, the animals underwent transverse mid-diaphyseal osteotomies of the right femur. Therapy was continued until sacrifice at 2, 3, 4, or 6 weeks postfracture. At 6 weeks post-fracture, greater callus area (6.59 +/- 3.78 mm(2) vs. 2.67 +/- 2.05 mm(2), p = 0.003) and increased radiographic intensity (mineral density) (0.48 +/- 0.14 vs. 0.30 +/- 0.80, p = 0.005) were found in the RANK-Fc versus saline oim/oim group, indicating a delay in callus remodeling. Despite this delay, mechanical tests at 6 weeks postfracture revealed no significant differences in whole bone properties of stiffness and failure moment. Further, RANKL inhibition resulted in a greater failure moment and greater work to failure for the nonfractured contralateral WT bones compared to the nonfractured saline WT bones. Together, these results demonstrate that RANKL inhibition does not adversely affect the mechanical properties of healing bone in the oim/oim mice, and is associated with increased strength in intact bone in the WT mice.

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.

Einfluss der Bisphosphonate auf die Frakturheilung

As the population ages and the prevalence of osteoporotic fractures increases, perioperative medical care of the elderly will continue to present challenges. Bisphosphonates, in combination with calcium and vitamin D have become the first-line therapy for patients with osteoporosis. Thus, one of the frequently asked questions concerning such patients is whether individuals who have recently sustained a fracture should take inhibitors of bone resorption. This discussion is relevant because many of the patients treated with bisphosphonates do have fractures, such as patients with osteoporosis, tumor bone disease, Paget's disease or osteogenesis imperfecta. A recent fracture should not preclude the initiation of therapy, because bisphosphonates have not been shown to interfere with overall fracture strength. Bisphosphonates appear to affect callus formation differently from either estrogen or raloxifene, but no significant difference in callus strength was seen 16 weeks after fracture. In addition, current studies demonstrate a significant reduction in periprosthetic bone loss after uncemented primary hip arthroplasty.

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

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

Gene therapy with human osteoprotegerin decreases callus remodeling with limited effects on biomechanical properties

Osteoprotegerin (OPG) is a naturally occurring protein, which prevents bone resorption by inhibition of osteoclastogenesis, function, and survival. Therefore, recombinant OPG may be an attractive drug in the treatment of chronic bone resorptive diseases such as osteoporosis. Gene therapy has the potential to achieve long-term treatment by delivering genes of anti-resorptive proteins to the recipient. The effects of OPG gene therapy on fracture healing have not been described previously. The influence of OPG gene therapy on callus formation, callus tissue structural strength, apparent material properties, and histology of tibia fractures in rats was investigated after 3 weeks and 8 weeks of healing. Intramuscular administration of adeno-associated virus (AAV) vector-mediated OPG resulted in increased levels of OPG in serum of approximately 100 ng/ml throughout the study period. Control animals with fractures received transduction with an AAV reporter gene construct (AAV-enhanced green fluorescent protein (eGFP)), and in this group serum OPG levels remained at baseline (<10 ng/ml). After 3 weeks of healing, AAV-OPG treatment reduced the number of osteoclasts in the callus tissue (33%, P < 0.001). However, AAV-OPG treatment did not influence callus dimensions, callus bone mineral content (BMC), fracture structural strength, or apparent callus tissue material properties. After 8 weeks of healing, AAV-OPG treatment reduced the number of osteoclasts in the callus tissue (31%, P < 0.001) compared with AAV-eGFP fractures. Furthermore, deposition of new woven bone at the fracture line of the original cortical bone was hampered (new woven bone present: in all AAV-eGFP animals, in 41% of AAV-OPG-treated animals, P < 0.001). AAV-OPG treatment also increased callus BMC (18%, P = 0.023) compared with AAV-eGFP fractures. AAV-OPG did not influence callus dimensions, structural strength of the fractures, or ultimate stress, whereas elastic modulus was reduced in the AAV-OPG groups (37%, P = 0.039). The experiment demonstrates that AAV-OPG gene therapy decreases the fracture remodeling, but this does not influence the structural strength of healing fractures.

Osteoprotegerin treatment impairs remodeling and apparent material properties of callus tissue without influencing structural fracture strength

The influence of osteoprotegerin (OPG) treatment on callus formation, callus tissue structural strength, apparent material properties, and histology of tibia fractures in rats was investigated after 3 weeks and 8 weeks of healing. OPG was given intravenously (10 mg/kg twice weekly) during the entire observation period, and control animals with fractures received vehicle only. When compared with control fractures after 3 weeks of healing, OPG treatment reduced the number of osteoclasts in the callus tissue (93%, P < 0.001) and hampered resorption of genuine cortical bone in the fracture line; OPG treatment did not influence callus dimensions, callus bone mineral content (BMC), fracture structural strength, or callus tissue apparent material properties. When compared with control fractures after 8 weeks of healing; OPG treatment reduced the number of osteoclasts in callus tissue (92%, P < 0.001), augmented callus dimensions (anteriorposterior diameter: 12%, P = 0.034, mediolateral diameter: 13%, P = 0.013), and increased callus BMC (50%, P = 0.007); OPG treatment hampered deposition of new woven bone at the fracture line of the genuine cortical bone (new woven bone present in all vehicle animals, but only in 13% of the OPG-treated animals (P < 0.001)); OPG treatment did not influence structural strength of the fractures, but decreased apparent material properties of the callus tissue (ultimate stress: 51%, P < 0.001; elastic modulus: 42%, P = 0.033). The experiment demonstrates that OPG treatment does not influence the early callus expansion and fracture strength. However, during the subsequent period of remodelling, OPG treatment impairs the normal remodeling and consolidation processes.

Bisphosphonate (YM529) delays the repair of cortical bone defect after drill-hole injury by reducing terminal differentiation of osteoblasts in the mouse femur

We evaluated the effects of YM529, a nitrogen-containing bisphosphonate, on the repair of cortical bone after drill-hole injury at the tissue-, cell- and gene-levels in the femur of mice. Eight-week-old male C57BL/6N mice were treated with an intravenous injection of 0.01, 0.05 and 0.1 mg/kg body weight (BW) of YM529, or the vehicle (VC) once a week from 8 weeks of age until sacrifice. At 10 weeks of age (day 0), a drill-hole was made in the diaphysis of bilateral femurs. Femoral specimens were obtained at days 3, 5, 7, 10, 14, 21 and 28 after surgery. Histology and histomorphometry confirmed the early woven bone formation in 7 days after injury in all four groups, but the following lamellar bone repair in the cortical tissue area delayed only in the YM529-treated groups. Since the findings were not dose-dependent, following evaluations were performed in VC and YM529 0.1 mg/kg BW dose groups. Calcein-labeled surface of regenerated bone decreased at day 21 in the YM529 group. At day 0, CFU-f number and mineralized nodule area that developed from marrow cells were significantly smaller in YM529 group than in VC group. At day 5, however, these values increased to levels similar to those in VC group. The mRNA expression levels of BMP-2, cbfa1, osterix, type I collagen, and osteocalcin in the injured bone and marrow cells at days 3 and 5 were similar in the two groups, but were higher in YM529 group at day 7 compared with that in the VC group. At day 14, the levels of these mRNAs were still high, while that of osteocalcin was significantly reduced compared to the VC group. These data indicate that the action of YM529 on bone formation is bimodal, stimulatory on the developments of osteogenic cells for the woven bone regeneration and inhibitory on the terminal differentiation of osteoblasts for the later remodeling, consequently leading to a delay in the lamellar bone healing in the cortical tissue area.

Alendronate inhibits bone resorption at the bone-screw interface

In the current study, we investigated whether the systemic administration of alendronate, a third-generation bisphosphonate, suppressed the loosening of screws at the bone-screw interface. We systemically administered alendronate to rats fitted with external fixators. External fixators with two half pins were applied to the right femurs of rats, and alendronate was administrated once a week during a 5-week postoperative period. Radiographic, histologic, and immunohistochemical findings subsequently were analyzed. Treatment with alendronate reduced the width of the fibrous loosening membrane and the number of osteoclasts at the bone-screw interface. These findings indicate that systemic treatment with alendronate exerts an inhibitory effect on local bone resorption at the bone-screw interface.

Delayed osteotomy but not fracture healing in pediatric osteogenesis imperfecta patients receiving pamidronate

This study evaluated factors influencing fracture (n = 197) and osteotomy (n = 200) healing in children with moderate to severe OI. Pamidronate treatment was associated with delayed healing after osteotomy, but not after fracture. The data suggest that both pamidronate and mechanical factors influence bone healing in this cohort.

INTRODUCTION

Intravenous pamidronate is widely used to treat children with moderate to severe osteogenesis imperfecta (OI). However, the effect of this treatment on bone healing is not well characterized. We therefore retrospectively analyzed the healing of lower limb fractures and osteotomies in children with moderate to severe OI, both before and after the start of pamidronate treatment.

MATERIALS AND METHODS

Bone healing was evaluated on standard radiographs after 197 lower limb fractures (132 femur and 65 tibia) in 82 patients (age at fracture, 0.0-19.9 years) and 200 intramedullary rodding procedures in 79 patients (age at surgery, 1.2-19.8 years). Delayed healing was diagnosed when a fracture or osteotomy line was at least partially visible 12 months after the event.

RESULTS

Delayed fracture healing was observed more frequently during than before pamidronate treatment. However, the effect of pamidronate was no longer significant when age differences were taken into account (odds ratio [OR], 1.76; 95% CI, 0.61-5.10). Better mobility status was a strong independent predictor of delayed healing after fractures that occurred during pamidronate treatment. After osteotomies, delayed healing was more frequent when pamidronate had been started before surgery (OR, 7.29; 95% CI, 2.62-20.3), and this effect persisted after adjustment for multiple confounders. During pamidronate treatment, older age (OR per year of age, 1.25; 95% CI, 1.06-1.47) and osteotomy of the tibia (OR, 3.51; 95% CI, 1.57-7.82) were independent predictors of delayed healing.

CONCLUSIONS

This study suggests that pamidronate therapy is associated with delayed healing of osteotomy sites after intramedullary rodding procedures. Better mobility status, but not pamidronate treatment, seems to be predictive of delayed healing after fractures.

Transient retention of endochondral cartilaginous matrix with bisphosphonate treatment in a long-term rabbit model of distraction osteogenesis

Bisphosphonates induce major increases in strength of callus in distraction osteogenesis in the short term. Poor understanding of the underlying mechanism, however, raises concerns about long-term consequences. In this long-term study in 32 rabbits, zoledronic acid transiently increased trabeculae by delayed temporal progression of endochondral bone remodeling but did not prevent radiographic completion of bone repair.

INTRODUCTION

We hypothesized that bisphosphonate inhibition of osteoclast-mediated resorption would retain bone during repair, producing a larger callus in the short term. However, if remodeling was not restored, completion of the bone repair process in the long term could be jeopardized.

MATERIALS AND METHODS

Juvenile rabbits underwent right tibial osteotomy and 2 weeks of distraction, followed by a period of consolidation. Animals received saline (controls) or zoledronic acid (ZA; 0.1 mg/kg at surgery and again 2 weeks later), and distracted tibias were examined by radiograph, DXA, histology, and histomorphometry at 2, 4, 6, 18, and 44 weeks after surgery.

RESULTS

Regenerated bone in ZA-treated animals was denser than controls on radiographs at 6 weeks and had more distinct radiodense trabeculae and retention of original cortices at 18 weeks. By 44 weeks, controls and ZA-treated animals were radiographically healed and indistinguishable. Regenerate BMD and BMC increased between 2 and 4 weeks in all animals, with a greater effect in ZA. At 6 weeks, BMD and BMC in ZA-treated animals were 1.6- and 2-fold greater, respectively, than controls (p < 0.01). From 6 to 44 weeks, the control values gradually increased and approached the ZA-treated values. Regenerate bone volume and trabecular number by histomorphometry were from 1.6- to 2-fold greater in ZA-treated animals at 6 and 18 weeks (p < 0.05). Endochondral cartilaginous matrix volume was up to 2.4-fold greater in ZA-treated animals at 2 and 4 weeks (p < 0.05). TRACP+ cells in ZA-treated animals were larger with more nuclei. Mineral apposition rate and osteoblast number and surface were lower in ZA-treated animals at 6 weeks (p < 0.01) but not at later times.

CONCLUSIONS

Disruption of TRACP+ cell function by ZA during bone regeneration seems to lead to an accretion of cancellous bone built on a larger endochondral cartilaginous matrix and increased bone mass, consistent with reported increases in short-term callus strength. This increase in bone mass, caused by a delay in remodeling, provided a transient advantage without preventing radiographic completion of the bone repair process in the long term. Noncontinuous treatment with nitrogen-containing bisphosphonates thus can have short-term beneficial effects without preventing long-term bone repair.

Bisphosphonates may reduce recurrence in giant cell tumor by inducing apoptosis

Giant cell tumor of bone is an aggressive tumor characterized by extensive bone destruction and high recurrence rates. This tumor consists of stromal cells and hematopoietic cells that interact in an autocrine manner to produce tumoral osteoclastogenesis and bone resorption. This autocrine regulation may be disrupted by novel therapeutic agents. Nonspecific local adjuvant therapies such as phenol or liquid nitrogen have been used in the treatment of giant cell tumor, but specific adjuvant therapies have not been described. The bisphosphonates pamidronate and Zoledronate can induce apoptosis in giant cell tumor culture in a dose-dependent manner. We established giant cell tumor cultures from patients with extensive destruction of bone. One of the four cultures formed osteoclastlike giant cells in vitro after more than six passages without exogenous receptor activator of NF-kappaB ligand or macrophage colony stimulating factor. Annexin V staining, presence of active cleaved form of caspase-3, and disappearance of poly (ADP-ribose) polymerase on Western blotting indicated activation of apoptosis by bisphosphonates in giant cell tumor. These results indicate that topical or systemic use of pamidronate or zoledronate can be a novel adjuvant therapy for giant cell tumor by targeting osteoclastlike giant cells, mononuclear giant cell precursor cells, and the autocrine loop of tumor osteoclastogenesis.

Zoledronic acid prevents osteopenia and increases bone strength in a rabbit model of distraction osteogenesis

Prolonged healing times and stress-shielding osteopenia remain problematic in distraction osteogenesis. In this study of 30 rabbits, zoledronic acid increased regenerate volume, mineralization, and tibial strength and prevented osteopenia over a 6-week period. Translation to the clinical setting, if safe, could improve outcomes in distraction osteogenesis in children.

INTRODUCTION

Because the external fixators for limb lengthening and reconstruction are designed to control the positions of bone fragments accurately, they also produce stress-shielding effects on the forming regenerate and surrounding bone. Osteopenia, leading to refracture and limitations on rehabilitation, are common consequences, potentially increasing morbidity and detracting from final clinical outcome.

MATERIALS AND METHODS

We examined the effect of zoledronic acid on distraction osteogenesis in 42 immature male NZW rabbits. The model chosen results in reliable regenerate formation and stress-shielding osteopenia. Fourteen animals received either Saline, zoledronic acid 0.1 mg/kg at surgery (ZOL), or another dose 2 weeks postoperatively (Redosed ZOL). Rabbits underwent DXA for bone mineral content and bone mineral density in regenerate and surrounding segments of operated and contralateral tibias. After death at 6 weeks, 30 pairs of tibias underwent quantitative computerized tomography (QCT) and four-point bend testing, and 12 were examined by histomorphometry. The study was powered at 0.8 to show differences of 1.3 SDs for mineral and mechanical parameters.

RESULTS

Osteopenia observed in tibias of the Saline group was absent in ZOL and Redosed ZOL tibias, the latter exhibiting higher bone mineral density and bone mineral content over contralateral regions (p < 0.01). Regenerate bone mineral content was higher in ZOL and Redosed ZOL versus Saline groups at 4 and 6 weeks (p < 0.01). Cross-sectional area was 49% and 59% greater at 6 weeks in ZOL and Redosed ZOL regenerates compared with the Saline group (p < 0.01). ZOL and Redosed ZOL tibias were 29% and 89% stronger by four-point bending than the Saline group (p < 0.01). Histomorphometry in the regenerate of ZOL and Redosed ZOL groups revealed higher trabecular bone volume and trabecular number compared with the Saline group (p < 0.001).

CONCLUSIONS

Zoledronic acid administration led to significantly greater bone area, mineral content, strength, and trabecular number with reduced stress-shielding osteopenia in this model of distraction osteogenesis. These data suggest that intraoperative and postoperative zoledronic acid administration could improve outcomes in children undergoing limb lengthening.

Long-term administration of clodronate does not prevent fracture healing in rats

Clinicians have been concerned that fractures do not heal properly in individuals exposed to bisphosphonate treatment, a treatment that strongly affects bone metabolism. The current study attempted to clarify the long-term effects of clodronate (dichloromethylene bisphosphonate) treatment on fracture healing in growing rats. Clodronate was administered subcutaneously twice a week in a dose of 2 mg/kg or 10 mg/kg. Physiologic saline served as a control. After 24 weeks of treatment, the tibiae were fractured, and the treatment was continued for another 4 weeks and 8 weeks. At both end points the cross-sectional areas of the callus, measured by peripheral quantitative computed tomography, were greater in the clodronate-treated rats than in controls, but there were no significant differences in bone mineral density. There were no significant differences between treatments in radiologic healing, histomorphometry, or in mechanical failure load of the callus with the exception of increased tensile stiffness at a dose of 2 mg/kg at 4 weeks. Clodronate treatment does not seem to prolong the fracture healing process, even when administered on a long-term basis before the fracture. Clodronate increases the size of the callus, but has only a minor effect on its biomechanical properties. The current results suggest that long-term clodronate treatment does not inhibit fracture healing.

Raloxifene, estrogen, and alendronate affect the processes of fracture repair differently in ovariectomized rats

We investigated the effects of inhibitors of bone resorption (estrogen, raloxifene, and alendronate) on the processes of fracture repair in ovariectomized (OVX) rats. One hundred forty female Sprague-Dawley rats at 3 months of age were either OVX or sham-operated and divided into five groups: sham control, OVX control, estrogen (17alpha-ethynyl estradiol [EE2], 0.1 mg/kg), raloxifene (Rlx, 1.0 mg/kg), and alendronate (Aln, 0.01 mg/kg) groups. Treatment began immediately after the surgery. Four weeks postovariectomy, prefracture controls were killed and bilateral osteotomies were performed on the femoral midshafts and fixed with intramedullary wires. Treatment was continued and fracture calluses were excised at 6 weeks and 16 weeks postfracture for evaluation by X-ray radiography, quantitative computed tomography (QCT,) biomechanical testing, and histomorphometry. At 6 weeks postfracture, Aln and OVX had larger calluses than other groups. Sham and OVX had higher ultimate load than EE2 and Rlx, with Aln not different from either control. Aln calluses also contained more mineral (bone mineral content [BMC]) than all other groups. By 16 weeks postfracture, OVX calluses were smaller than at 6 weeks and the dimensions for Aln had not changed. Aln had higher BMC and ultimate load than OVX, EE2, and Rlx. EE2 and Rlx had similar biomechanical properties, which were similar to sham. Interestingly, OVX and Aln animals were heavier than other groups at all time points; therefore, ultimate load was normalized by body weight to show no significant differences in strength of the whole callus between groups at either 6 weeks or 16 weeks postfracture. However, Aln strongly suppressed remodeling of the callus, resulting in the highest content of woven bone, persistent visibility of the original fracture line, and lowest content of lamellar bone, compared with other groups. Therefore, the larger Aln callus appeared to be a remarkable, morphological adaptation to secure the fracture with inferior material. In conclusion, OVX-stimulated bone turnover resulted in the fastest progression of fracture repair that was most delayed with Aln treatment, consistent with marked suppression of bone resorption and formation activity. Estrogen and Rlx had similar effects that were generally similar to sham, indicating that mild suppression of bone turnover with these agents has insignificant effects on the progression of fracture repair.

Effect of pamidronate on distraction osteogenesis and fixator-related osteoporosis

We examined the effect on bone mineral density (BMD), bone mineral content (BMC) and mechanical properties of a single 1.0 mg/kg dose of the bisphosphonate pamidronate (Novartis), in a distraction osteogenesis model in immature rabbits. Twenty rabbits underwent a tibial osteotomy. Ten rabbits received pamidronate 1.0 mg/kg via ear vein intra-operatively while 10 received saline infusions only. After a 24 h latency, all underwent distraction of 0.375 mm twice daily for 15 days. The animals were culled at 42 days. After culling, the distracted and non-distracted tibiae were examined by quantitative computer tomography (QCT). The volumetric bone mineral density (vBMD, mg/cm(3)) in the bone proximal and distal to the regenerate in the operated limb was increased by a mean of 11 and 14%, respectively, compared to controls (P<0.05). The vBMD of the regenerate bone was increased by a mean of 8% over controls (NS, P=0.17). The bone mineral content (BMC, mg) was increased by 23% (proximal and distal) (P<0.05) in the bone surrounding the lengthening and there was a 17% trend towards an increase in the regenerate (NS, P=0.3). Four-point bending analysis documented that the load to failure was increased by 32% from 436 to 574 N (P<0.01) in the pamidronate group. The modulus of elasticity was not different between the control and pamidronate groups (P=0.3), and in both groups was only approximately one-third of the intact tibiae (P<0.001). The administration of a single dose of pamidronate can improve the bone mineral density, content and mechanical properties of a bone undergoing distraction osteogenesis.

Long-term effect of incadronate disodium (YM-175) on fracture healing of femoral shaft in growing rats

The aim of this study was to investigate the long-term effect of incadronate on fracture healing of the femoral shaft in rats. Female Sprague-Dawley 8-week-old rats were injected subcutaneously (sc) with either vehicle (V group) or two doses of incadronate (10 microg/kg and 100 microg/kg) three times a week for 2 weeks. Right femoral diaphysis was then fractured and fixed with intramedullary stainless wire. Just after fracture, incadronate treatment was stopped in pretreatment groups (P groups: P-10 and P-100) or continued in continuous treatment groups (C groups: C-10 and C-100). All rats were killed at 25 weeks or 49 weeks after surgery. Fractured femur was evaluated radiologically and mechanically and then stained in Villanueva bone stain and embedded in methyl methacrylate. Undecalcified cross-sections from the fracture area were evaluated microradiologically and histomorphometrically. Radiographic observation showed that the fracture line disappeared in all groups. Cross-sectional area in the C-100 group was the biggest among all groups and in the C-10 group was larger than that in the V group at 25 weeks. Histological and histomorphometric observations showed that the process of fracture healing was delayed under continuous treatment with incadronate as evidenced by the delay of both lamellar cortical shell formation and resolution of original cortex in C groups. Percent linear labeling perimeter, mineral apposition rate (MAR), and bone formation rate (BFR) in C groups significantly decreased compared with the other groups, indicating that the callus remodeling was suppressed under continuous treatment, especially with a high dose. Mechanical study showed that the stiffness and ultimate load of the fractured femur in the C 100 group were the highest among all groups at both 25 weeks and 49 weeks. In conclusion, this study showed that long-term continuous treatment with incadronate delayed the process of fracture healing of femur in rats, especially under high dose but it did not impair the recovery of mechanical integrity of the fracture.

Clodronate increases mineralization of callus after Colles' fracture: a randomized, double-blind, placebo-controlled, prospective trial in 32 patients

In a randomized study of 32 postmenopausal women with a Colles' fracture, we studied whether 8 weeks of treatment with clodronate, a bisphosphonate, could prevent posttraumatic osteopenia. The patients were treated with a plaster splint for 4 weeks. The bone mineral density (BMD) of the forearm bones was measured at 2 levels with dual-energy x-ray absorptiometry (DEXA) 2, 6 and 12 months after the fracture. At 2 months, in the clodronate group, there was a median 53% higher BMD in the fracture region of the radius than in the uninjured radius. In the placebo group, we found a 33% higher BMD in the fractured radius at that level than in the uninjured radius. This increase in BMD of the fractured radius, caused by clodronate, was statistically significant. At 12 months, the BMD of the fracture side had been reduced by 17% and 12%, respectively, at that time it was still significantly increased in the clodronate group alone. In the ulna at the same level, we found no significant changes in BMD in either group on either side at any time. At 2 months, at the level between the distal and middle thirds, in the fractured radius, the median BMD was 7% lower in the clodronate group and 6% lower in the placebo group than in the uninjured radius. Although the reduction in BMD at that level was significant, there was no difference between the two treatment groups. At this level, the ulna on the fractured side showed a similar pattern, with a 5% lower BMD in the clodronate group and a 4% lower BMD in the placebo group. This osteopenia showed a small but significant progression on the fractured side after 6 and 12 months.