Effects of Alendronate on Lumbar Posterolateral Fusion Using Hydroxyapatite in Rabbits

There are controversies regarding the effect of alendronate on spine fusion. In order to study the effects of alendronate on fusion with porous hydroxyapatite, a total of 47 rabbits underwent posterolateral lumbar fusion. The rabbits received saline (control group), alendronate 0.5 mg/kg/week (low‐dose group), or alendronate 1 mg/kg/week (high‐dose group) per oral beginning 2 weeks before surgery. All animals were euthanized 12 weeks after surgery, and the extent of fusion was assessed by radiographs, manual palpation, computed tomography (CT) scan, mechanical testing, and histologic examination. The fusion rates by manual palpation, radiography, and CT scan were similar in all groups. There was no significant difference in pixel optic density from the CT scan. Biomechanical testing showed the tensile strength of the control group was higher than that of the treatment group including the low‐ and high‐dose group. In histologic examination, the fusion masses of control animals were characterized by a higher predominance of well‐incorporated, trabeculated bone with a prominent marrow element. The treatment group showed a higher proportion of woven bone structures and thicker bony trabeculae. There was no significant difference in the fusion rate, but the tensile strength of treatment group was significantly lower. Histologic examination showed that alendronate inhibited bone resorption and remodeling.     

Alendronate treatment promotes bone formation with a less anisotropic microstructure during intramembranous ossification in rats

There are safety concerns regarding administration of bisphosphonates to children. Little is known about the effects of bisphosphonates on bone matrix organization during bone modeling. The present study examined the effects of alendronate (ALN) on bone matrices formed by intramembranous ossification in the appendicular growing skeleton. ALN was administered to 1-week-old Sprague–Dawley rats at a dose of 0, 35, or 350 μg/kg/week for 4 or 8 weeks. The position of femoral diaphysis formed exclusively by intramembranous ossification was identified, and cross sections of cortical bone at this position were analyzed. Bone mineral density (BMD) and geometric parameters were evaluated using peripheral quantitative computed tomography. The preferential orientation degree of biological apatite (BAp) crystals in the bone longitudinal direction, which shows the degree of bone matrix anisotropy, was evaluated using microbeam X-ray diffraction analysis. We analyzed bone histomorphometrical parameters and performed bone nanomechanical tests to examine the material properties of newly developing cortical bone. The preferential orientation degree of BAp crystals significantly decreased in 35 μg/kg/week ALN-treated groups compared with vehicle-treated groups, although there were no significant differences in BMD between the two groups. The periosteal mineral apposition rate significantly increased in the 35 μg/kg/week ALN-treated group. We found a high negative correlation between bone matrix anisotropy and the regional periosteal mineral apposition rate (r = −0.862, P < 0.001). Nanomechanical tests revealed that 35 μg/kg/week ALN administration caused deterioration of the material properties of the bone microstructure. These new findings suggest that alendronate affects bone matrix organization and promotes bone formation with a less anisotropic microstructure during intramembranous ossification.     

1Alpha,25-dihydroxy-2beta(3-hydroxypropoxy)vitamin D3 (ED-71) suppressed callus remodeling but did not interfere with fracture healing in rat femora

INTRODUCTION: Because osteoporotic patients are prone to fractures, it must be considered whether or not patients undergoing drug therapies should discontinue treatment after sustaining a non-vertebral fracture. This study has tested the effect of novel active vitamin D3 analog, 1alpha,25-dihydroxy-2beta(3-hydroxypropoxy)vitamin D3 (ED-71), on the fracture healing comparing with a powerful anti-resorptive agent, alendronate, using a rat femoral fracture model. MATERIALS AND METHODS: Female SD rats (n=201) allocated into 6 groups were treated with MCT-vehicle and ED-71 at 0.025 and 0.05 microg/kg/day (EDL and EDH groups), and with saline-vehicle and alendronate at 5 and 10 microg/kg/day (ALL and ALH groups). After 4 weeks of pretreatment, osteotomy of the femur was performed. Treatment was continued until sacrifice at 6 and 16 weeks post-fracture. Fracture callus was evaluated by soft X-ray radiography, pQCT, biomechanical testing and histomorphometry. RESULTS: At 16 weeks post-fracture, new cortical shell appeared in 100% of Control (MCT and saline-vehicle), EDL and EHL, and in 67% and 56% of ALL and ALH, respectively. ED-71 treatment showed insignificantly large callus area only at 6 weeks, while alendronate treatment induced bigger callus at both 6 and 16 weeks post-fracture. The lamellar/callus area was decreased only at 6 weeks by ED-71 treatment, but both at 6 and 16 weeks by alendronate treatment. Osteoclast number in callus surface was decreased in both ED-71 and alendronate treatment groups at 6 weeks and in EDH, ALL and ALH at 16 weeks, indicating that ED-71 inhibits osteoclastic bone resorption, but its effect is less prominent than alendronate. Almost complete callus remodeling was observed in ED-71-treated groups at 16 weeks without any significant change in structural and material properties of fractured bone. CONCLUSIONS: ED-71 suppression of callus remodeling by inhibiting osteoclastic bone resorption was mild and dose-dependent and did not interfere with natural fracture healing process at 16 weeks post-fracture.     

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

We investigated the effect of locally administered bisphosphonate on distraction osteogenesis in a rabbit model and evaluated its systemic effect. An osteotomy on the right tibia followed by distraction for four weeks was performed on 47 immature rabbits. They were divided into seven equal groups, with each group receiving a different treatment regime. Saline and three types of dosage of alendronate (low, 0.75 microg/kg; mid, 7.5 microg/kg and high 75 microg/kg) were given by systemic injection in four groups, and saline and two dosages (low and mild) were delivered by local injection to the distraction gap in the remaining three groups. The injections were performed five times weekly during the period of distraction. After nine weeks the animals were killed and image analysis and mechanical testing were performed on the distracted right tibiae and the left tibiae which served as a control group. The local low-dose alendronate group showed a mean increase in bone mineral density of 124.3 mg/cm(3) over the local saline group (analysis of variance, p < 0.05) without any adverse effect on the left control tibiae. The findings indicate that the administration of local low-dose alendronate could be an effective pharmacological means of improving bone formation in distraction osteogenesis.     

The effect of alendronate sodium on spinal fusion: a rabbit model.

BACKGROUND CONTEXT: Bisphosphonates affect bone remodeling and increase bone mass through the inhibition of osteoclasts. Their effect on osteoblasts, and the balance between osteoblastic and osteoclastic activity on bone turnover and healing, is not completely understood. Specifically, the effect of bisphosphonates on spinal fusion has yet to be determined. With the increasing use of bisphosphonates in the elderly population, this effect needs to be delineated. PURPOSE: To evaluate the effect of alendronate sodium after an intertransverse process spinal fusion in a rabbit model. STUDY DESIGN/SETTING: Randomized double-blinded in vivo study of the effect of alendronate sodium in a spinal fusion model. METHODS: Fifty New Zealand white rabbits underwent a posterolateral L5-L6 intertransverse process arthrodesis with autogenous iliac crest bone graft. The rabbits were then randomly divided into two groups. Group I received 3 cc of saline placebo per oral gavage, and Group II received 200 micrograms (approximately 0.05 mg/kg/day) of alendronate sodium dissolved in 3 cc of saline per day for 8 weeks. Upon completion, the rabbits were sacrificed and the lumbar spines harvested, radiographed and graded for motion across the fusion site with manual palpation. Two independent pathologists then prepared and sectioned each left and right fusion mass. Three random x10 fields were examined and graded for both the cephalad and caudad ends of each section (516 fields). Fusion quality was graded using an established histological scoring scale (score 0 to 7 based on fibrous and bone content of the fusion mass). RESULTS: Two rabbits died on the day of operation, and 48 rabbits survived the operation. Five additional rabbits died within the first 2 postoperative weeks. Thus, 43 rabbits (21 in Group I, 22 in Group II) completed the 8-week course of treatment. Grading each side separately, 26 of 42 fusion masses (62%) in Group I and 24 of 44 fusion masses (55%) in Group II had radiographic evidence of fusion (p=.76). With gross palpation, 11 of 21 motion segments (52%) in Group I versus 13 of 22 motion segments (59%) in Group II were determined to have a solid fusion (p=.76). Histologically, Group I had a higher median score (6.0; range, 0 to 7 vs. 1.0; range, 0 to 7; p<.0001) and a higher fusion rate (76% vs. 45%; p=.004) than Group II. CONCLUSIONS: Alendronate sodium appears to inhibit or delay bone fusion in a rabbit model. Presumably, this occurs as a result of uncoupling the balanced osteoclastic and osteoblastic activity inherent to bone healing. These findings suggest that a discontinuance of alendronate sodium postoperatively during the acute fusion period may be warranted.     

Co-treatment of PTH with osteoprotegerin or alendronate increases its anabolic effect on the skeleton of oophorectomized mice.

We examined the effects of 60 days of co-treatment of PTH with either OPG or alendronate in oophorectomized mice. Compared with PTH alone, co-treatment of PTH with either of these two mechanistically distinct anti-catabolics improved bone volume, mechanical strength, and appendicular and axial mineralization and prolonged the beneficial effect of PTH on BMD. INTRODUCTION: Conflicting evidence exists as to whether the anabolic effect of PTH is inhibited by the action of anti-catabolics. To examine this issue, we assessed the effects of alendronate and osteoprotegerin (OPG), two anti-catabolics with different modes of action, on the anabolic activity of PTH(1-34) in the skeleton of 4-month-old oophorectomized mice. MATERIALS AND METHODS: Mice treated with vehicle alone (PBS), alendronate alone (100 microg/kg/week), OPG alone (10 mg/kg twice a week), or PTH alone (80 microg/kg/day) were compared with each other and with animals administered PTH plus alendronate or PTH plus OPG. We assessed lumbar spine and femoral BMD at 0, 30, and 60 days. Contact radiography, histology, and histomorphometry, three-point bending assay of the femur, and serum osteocalcin and TRACP5b assays were performed at 2 months. RESULTS: Although alendronate and OPG each suppressed bone turnover, at the doses used, this was more profound with OPG. Increases in lumbar spine and femoral BMD and in trabecular bone volume were at least as great with OPG as with alendronate, and mechanical indices of femoral bone strength improved only with OPG. Both produced a plateau in spine and femoral BMD increases by 30 days. Co-treatment of PTH with each anti-catabolic produced additive increases in BMD in the femur and supra-additive increases in the lumbar spine with no plateau effects. Neither anti-catabolic impeded the PTH-induced increase in bone volume or the increase in mechanical strength of the femur. CONCLUSIONS: These studies show that the highly potent anti-catabolic OPG can produce dramatic increases in BMD and bone strength; that the temporal pattern of activity of bone formation and resorption modulators may have major influence on net skeletal accrual; and that, depending on timing, inhibition of osteoclastic activity may markedly augment the anabolic action of PTH.     

Effects of the systemic administration of alendronate on bone formation in a porous hydroxyapatite/collagen composite and resorption by osteoclasts in a bone defect model in rabbits

Several bisphosphonates are now available for the treatment of osteoporosis. Porous hydroxyapatite/collagen (HA/Col) composite is an osteoconductive bone substitute which is resorbed by osteoclasts. The effects of the bisphosphonate alendronate on the formation of bone in porous HA/Col and its resorption by osteoclasts were evaluated using a rabbit model. Porous HA/Col cylinders measuring 6 mm in diameter and 8 mm in length, with a pore size of 100 μm to 500 μm and 95% porosity, were inserted into a defect produced in the lateral femoral condyles of 72 rabbits. The rabbits were divided into four groups based on the protocol of alendronate administration: the control group did not receive any alendronate, the pre group had alendronate treatment for three weeks prior to the implantation of the HA/Col, the post group had alendronate treatment following implantation until euthanasia, and the pre+post group had continuous alendronate treatment from three weeks prior to surgery until euthanasia. All rabbits were injected intravenously with either saline or alendronate (7.5 μg/kg) once a week. Each group had 18 rabbits, six in each group being killed at three, six and 12 weeks post-operatively. Alendronate administration suppressed the resorption of the implants. Additionally, the mineral densities of newly formed bone in the alendronate-treated groups were lower than those in the control group at 12 weeks post-operatively. Interestingly, the number of osteoclasts attached to the implant correlated with the extent of bone formation at three weeks. In conclusion, the systemic administration of alendronate in our rabbit model at a dose-for-weight equivalent to the clinical dose used in the treatment of osteoporosis in Japan affected the mineral density and remodelling of bone tissue in implanted porous HA/Col composites.     

Alendronate influences bending force of femoral diaphysis after orchidectomy in rats.

BACKGROUND AND AIMS: We examined the effect of alendronate on bone following orchidectomy-induced osteoporosis. MATERIAL AND METHODS: Eighty male rats were used. Group I (C) served as the untreated control. In group II (ALN), alendronate was administered subcutaneously (18 microg/kg). In group III (ORC), rats were castrated only. In group IV (ORC+ALN), administration of alendronate (18 microg/kg) was started immediately after castration, and in group V (ORC + ALN-21) medication was started 21 days after castration. Alendronate was given twice a week for eight weeks in the treatment groups. Bone mineral density (BMD) of the proximal femur, ultimate bending forces of femoral diaphyses, ash weights of femurs (AWcc) and the calcium content (Ca) of femoral ash were determined. Histomorphometric analysis was performed on trabecular bone of proximal tibiae. RESULTS: BMD of the proximal femur was significantly decreased by orchidectomy compared with C and ALN. However, no statistical difference was observed between alendronate-treated groups (ORC + ALN and ORC + ALN-21) and the ORC group. Histologically, alendronate reduced the trabecular bone turnover. Ultimate bending force increased significantly in the ORC+ALN-21 group compared with group C, and had a good correlation with the cortical width of tibia (r = 0.53, p < 0.001). Ash weight per bone volume (AWcc) was lowest in the ORC group, whilst alendronate maintained AWcc after orchidectomy. CONCLUSION: Alendronate increased the ultimate bending force of the femoral diaphysis after orchidectomy. On the other hand, ALN treatment was not able to maintain the BMD of the proximal femur at the pre-orchidectomy level. Our results suggest that the remodelling and modelling of bone may influence the response to ALN treatment.     

Treatment of renal transplant recipients with low bone mineral density: a randomized prospective trial of alendronate, alfacalcidol, and alendronate combined with alfacalcidol

We sought to compare the treatment modalities of alendronate, alfacalcidol, and alendronate combined with alfacalcidol in renal transplant recipients with low bone mineral density. Sixty-four kidney graft recipients (22 women, 42 men) were recruited to this study. Of these 64 patients, 9 served as the control group with T scores more than -1. The remaining 55 patients randomly assigned to treatment had T scores less than -1 and were assigned to 3 groups: group 1 received alfacalcidol (0.5 microg/d); group 2, alendronate (10 mg/d); and group 3, alendronate (10 mg/d) + alfacalcidol (0.5 microg/d per os). Twenty-five patients were allocated to alfacalcidol, 13 patients to alendronate, and 17 patients to alendronate + alfacalcidol treatment. Bone mineral densities of the lumbar spine and femoral neck were measured before and 12 months after treatment. The groups were compared for risk factors of osteoporosis, biochemistry, and bone mineral density. Kruskal-Wallis, one-way ANOVA, and Student t tests were used. With the alendronate + alfacalcidol group, bone mineral density at the lumbar spine significantly increased by 7.9% (P = .006) with a significant improvement in T score (P = .003). Bone mineral density at the femoral neck significantly increased by 8% in the alendronate + alfacalcidol group (P = .01) with a significant improvement in T score (P = .02). The use of a combination of alendronate and alfacalcidol seemed to be safe and more effective than the separate use of the 2 agents to improve bone mass in renal transplant recipients.     

Long-term therapy of ovariectomy-induced osteopenia with parathyroid hormone analog SDZ PTS 893 and bone maintenance in retired breeder rats

The aim of the study was to assess the long-term anabolic effect of the parathyroid hormone (PTH) analog SDZ PTS 893 in a dose-response manner, and to determine the ability of the antiresorptive agents estradiol and alendronate to maintain bone mass after withdrawal of SDZ PTS 893. One hundred thirty retired breeder Wistar rats were distributed into 13 groups with 10 rats in each group: 1 baseline group, 2 sham groups, and 10 ovariectomized groups. Treatment was initiated 12 weeks after ovariectomy. SDZ PTS 893 treatment was administered daily subcutaneously (Monday to Friday) for 36 weeks. Treatment regimens were as follows: (1) baseline (-12 weeks); (2) ovariectomy (ovx) (0 weeks); (3) sham (36 weeks); (4) ovx (36 weeks); (5) SDZ PTS 893 12.5 microg/kg/day (36 weeks); (6) SDZ PTS 893 25 microg/kg/day (36 weeks); (7) SDZ PTS 893 50 microg/kg/day (36 weeks); (8) SDZ PTS 893 100 microg/kg/day (36 weeks); for the maintenance part of the study: (9) sham (48 weeks); ovx animals treated with SDZ PTS 893, 50 microg/kg/day for 36 weeks followed by 12 weeks of treatment regimens: (10) placebo; (11) SDZ PTS 893 50 microg/kg/day; (12) estradiol 10 microg/kg/day; or (13) alendronate 28 microg/kg (2 injections/week). The effects of ovx, SDZ PTS 893 treatment, and maintenance regimens were measured at four skeletal sites: lumbar vertebra; femoral diaphysis; distal femoral metaphysis; and proximal femoral metaphysis (femoral neck). At these sites, bone density and bone strength were measured as treatment endpoints. Furthermore, bone dimensions were measured at the midpoint of the femur. The results showed that SDZ PTS 893 increased bone strength in a dose-dependent manner at all skeletal sites tested. At the vertebral body and distal femoral metaphysis, apparent ash density increased in a similar way. There was a slight decrease in cortical density at the mid-diaphyseal site. Static histomorphometry showed increased bone area due to a decreased marrow area (endosteal net bone gain) but also due to increased tissue area (periosteal net bone gain). For maintenance, continuous SDZ PTS 893 therapy was most efficient, followed by alendronate and estradiol treatment with regard to preservation of bone mass and strength. It is concluded that the new PTH analog SDZ PTS 893 has a highly anabolic, dose- and time-dependent effect on all skeletal sites tested. Bone formation is induced at both endosteal and periosteal surfaces.     

Effects of vitamin K2 (menatetrenone) and alendronate on bone mineral density and bone strength in rats fed a low-magnesium diet

In this study, we examined changes in bone parameters and bone strength in rats fed low-Mg diets (experiment 1) and the effects of vitamin K2 (MK-4, experiment 3) and alendronate (ALN, experiment 2) in this model. In experiment 1, 5-week-old male Wistar rats were fed three low-Mg diets (Mg 9, 6, 3 mg/100 g diet) for 4 weeks. Although the cortical bone mineral content (CtBMC) and cortical thickness (CtTh) of the femoral diaphysis in all low-Mg-diet groups were the same as or greater than those in the intact group (Mg: 90 mg/100 g diet), the maximum load and elastic modulus were significantly reduced in the 3-mg-Mg group. In experiment 2, 4-week-old Wistar rats were fed a 6-mg-Mg diet for 8 weeks, and the effect of ALN (2, 20, and 200 microg/kg twice a week) was evaluated. The administration of ALN at 200 microg/kg increased the cortical bone mineral content (CtBMC), CtTh, and maximum load, but had no effect on the elastic modulus, as compared with the low-Mg-control group. In experiment 3, the effect of MK-4 was evaluated under the same conditions as in experiment 2. The administration of MK-4 had no effect on CtBMC, CtTh, or bone components of the femoral diaphysis. However, MK-4 inhibited the decreases in maximum load and elastic modulus due to the low-Mg diet. Since there is no other experimental model in which there is a decrease in bone mechanical properties without a decrease in bone mineral content, the low-Mg diet model is considered to be an excellent model for examining bone quality. Our results from this model suggest that MK-4 and ALN affect bone mechanical properties by different mechanisms.     

The effects of local and systemic alendronate delivery on wear debris‐induced osteolysis in vivo

We investigated the effects of locally and systemically administered alendronate on wear debris‐induced osteolysis in vivo. Endotoxin‐free titanium particles were injected into rabbit femurs, prior to insertion of a nonweight‐bearing polymethylmethacrylate plug into the distal femur canal. Then the particles were repeatedly injected into the knee 2, 4, and 6 weeks after the implantation. Alendronate was incorporated at three different concentrations (0.1, 0.5, and 1.0 wt %) into bone cement for local delivery. For systemic delivery, alendronate was subcutaneously injected (1.0 mg/kg/week) 1 week after the implantation and then once a week until sacrifice. Eight weeks postoperatively, there was significant evidence of osteolysis surrounding the plug in the control group compared with markedly blocked osteolysis in the 0.5 wt % and the 1.0 wt % groups, and the systemic group. There was a concentration‐dependent effect of alendronate‐loaded bone cement on the improvement of peri‐prosthetic bone stock. Notably, no significant differences were found between the 0.5 wt % and the systemic group in peri‐prosthetic bone stock and implant fixation. Collectively, although the biological efficacy after the systemic delivery of alendronate was slightly higher than that in the local treatment groups, alendronate‐loaded bone cement may be therapeutically effective in inhibiting titanium particle‐induced osteolysis in vivo. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:893–899, 2010     

Effects of alendronate on particle-induced osteolysis in a rat model

BACKGROUND: Particle-induced osteolysis is currently a major problem affecting the long-term survivorship of total joint replacements. Alendronate is a third-generation bisphosphonate that blocks osteoclastic bone resorption. The objective of this study was to determine whether alendronate could prevent particle-induced osteolysis or restore (reverse) bone loss in established osteolysis. METHODS: A rat model of particle-induced osteolysis was used. A specially designed polyethylene implant was placed in the proximal part of the right tibia of seventy-two animals. Following four weeks of healing, the animals were randomized into control groups, a prevention group, or a treatment group. In the prevention group, animals received intra-articular injections of high-density polyethylene particles (mean size, 2 m; all <10 m) at four, six, and eight weeks postoperatively. Alendronate (0.01 mg/kg/day) was administered concomitantly through an implantable pump from the fourth week through the tenth week. In the treatment group, animals were also exposed to polyethylene particles at four, six, and eight weeks, to establish bone loss, but they received alendronate subsequently, from the tenth week through the sixteenth week, to treat the bone loss. Positive (particle-only) and negative (saline-solution-only) control groups were assessed as well. Tissues were harvested at ten weeks in the prevention group and at sixteen weeks in the treatment group. Histological analyses and histomorphometric determinations of the periprosthetic bone volume were carried out. RESULTS: Histological examination showed a rim of new bone (neocortex) around the implant in the untreated and saline-solution-treated control animals (no polyethylene particles). Treatment with saline solution (no polyethylene particles) did not affect periprosthetic bone. Animals exposed to polyethylene particles had bone loss. In those that received alendronate, the bone loss was either prevented or reversed, and the quantity of neocortical and trabecular bone was increased compared with that of the controls. Alendronate effectively preserved periprosthetic bone in both the prevention and treatment groups. In the prevention arm, the mean periprosthetic bone volume of the neocortex and the surrounding trabecular bone, as determined with histomorphometry, was 21.5% +/- 6.5% in the saline-solution-treated controls (no particles), 13.1% +/- 5.9% in the particle-treated animals, and 32.6% +/- 6.4% in the alendronate-treated animals (p < 0.001). In the treatment arm, the mean periprosthetic bone volume was 27.2% +/- 5.6% in the saline-solution-treated controls, 17.7% +/- 6.2% in the particle-treated animals, and 30.2% +/- 5.9% in the alendronate-treated animals (p = 0.002). CONCLUSIONS: In our model, the intra-articular injection of polyethylene particles caused substantial bone loss around a loaded implant. Alendronate effectively prevented and treated the particle-induced periprosthetic bone loss.     

Alendronate enhances antibiotic-impregnated bone grafts in the treatment of osteomyelitis

Bisphosphonates are systemic drugs. There is limited knowledge about their effects when applied locally and in osteomyelitis treatment. A prospective longitudinal randomised controlled study was designed in rat tibia to test the efficacy of local or systemically administered bisphosphonates for controlling the osteolytic reactions and possible effects on local infection control. Tibial osteomyelitis was induced in 72 Wistar albino rats with Staphylococcus aureus ATCC 25923 strain. Débridement was performed on all rats in all groups. No other treatment was given to the control group. Treatment groups received "plain bone grafts", "vancomycin-loaded bone grafts", "vancomycin-loaded bone grafts+systemic alendronate", "alendronate-impregnated bone grafts" and "vancomycin+alendronate-impregnated grafts". Study results were evaluated by swab cultures, radiology, quantitative computed tomography, dual-energy X-ray absorptiometry (DEXA) and histopathology. S. aureus was eradicated in groups II and IV by the sixth week. Diaphyseal widening, bone deformation, diaphyseal widening and osteolysis scores were significantly lower (p < 0.05), and bone mineral content, density measurements and DEXA scores were significantly higher (p = 0.001) with alendronate administration. Histology revealed marked osteoblastic activity. Local alendronate interfered with local infection control. Even though local alendronate at the given dose has stronger effects, the possible effects on the local inflammatory process needs to be clarified.     

Treatment with a Potent Cathepsin K Inhibitor Preserves Cortical and Trabecular Bone Mass in Ovariectomized Monkeys

The cysteine protease cathepsin K is involved in osteoclast-mediated bone resorption. We evaluated the effect of daily oral dosing of an inhibitor of human cathepsin K (SB-462795 [relacatib]) for 9 months on bone turnover, mass, and architecture in estrogen-deficient cynomolgus monkeys. Ovariectomized animals were treated orally with relacatib at 1, 3, or 10 mg/kg/day, or oral vehicle plus alendronate at 0.05 mg/kg by IV injection once every 2 weeks. The control groups, ovariectomized and sham-ovariectomized animals, received vehicle (all groups n = 20 animals). Samples for biomarker analysis were collected at various times, bone mass changes were evaluated at 6 and 9 months of treatment, and histomorphometric analysis was performed at 9 months. Relacatib significantly reduced urinary N-telopeptide excretion within 1 week of treatment at all dose levels, an effect that was maintained at the highest dose level. At some time points bone formation markers were elevated at the lowest dose of relacatib. Animals treated with relacatib had dose-dependent preservation of areal bone mineral density reaching statistical significance in distal femur. In femur neck there was significant preservation of total volumetric BMD (vBMD) by relacatib. By histomorphometry, relacatib reduced indices of bone resorption and formation at cancellous sites as did alendronate. In cortical bone, osteonal bone formation rate was reduced by alendronate but preserved at low and medium doses of relacatib. Thus, relacatib preserved cortical and cancellous bone mass in ovariectomized monkeys.     

Risedronate improves bone architecture and strength faster than alendronate in ovariectomized rats on a low-calcium diet

Clinical evidence suggests that, compared with alendronate, risedronate reduces fracture risk faster and more potently, with less bone mass gain. We tested the hypothesis that risedronate improves bone quality faster than alendronate using calcium-deficient, ovariectomized (OVX) rats. Female Sprague–Dawley rats at 24 weeks of age were divided into sham-operated and OVX groups and fed a low-calcium (0.05 %) diet under paired feeding. After 12 weeks, OVX rats were divided into five groups and treated with vehicle, risedronate (3.5 and 17.5 μg/kg/week, s.c.) or alendronate (7 and 35 μg/kg/week, s.c.). Rats were killed 6–8 weeks later and the bone architecture and strength of the left femur were evaluated by micro-computed tomography and a three-point bending test. Trabecular bone mineral density (BMD), number and thickness were significantly lower in OVX rats than in the sham-operated group. Cortical BMD, bone area (Ct.Ar), and thickness (Ct.Th) were similarly decreased. Risedronate significantly improved Ct.Ar (+8 %) and Ct.Th (+9 %) at 6 weeks, while alendronate only caused a significant improvement in Ct.Ar (+8 % at 6 weeks) and only at the higher dose. At 8 weeks, both risedronate and alendronate significantly increased trabecular BMD compared with the vehicle. Bone strength parameters showed a significant correlation between Ct.Ar and Ct.Th. Risedronate significantly improved maximum load at 6 weeks, while alendronate failed to produce any significant changes. Our results suggest that risedronate is superior to alendronate at improving cortical bone architecture and strength, and that enhanced bone quality partly accounts for risedronate’s efficacy.     

Effects of alendronate on bone quality and remodeling in glucocorticoid-induced osteoporosis: a histomorphometric analysis of transiliac biopsies.

Effects of alendronate (ALN) on bone quality and turnover were assessed in 88 patients (52 women and 36 men aged 22-75 years) who received long-term oral glucocorticoid exposure. Patients were randomized to receive oral placebo or alendronate 2.5, 5, or 10 mg/day for 1 year and stratified according to the duration of their prior glucocorticoid treatment. Transiliac bone biopsies were obtained for qualitative and quantitative analysis after tetracycline double-labeling at the end of 1 year of treatment. As previously reported in glucocorticoid-induced osteoporosis, low cancellous bone volume and wall thickness were noted in the placebo group as compared with normal values. Alendronate treatment was not associated with any qualitative abnormalities. Quantitative comparisons among the four treatment groups were performed after adjustment for age, gender, and steroid exposure. Alendronate did not impair mineralization at any dose as assessed by mineralization rate. Osteoid thickness (O.Th) and volume (OV/BV) were significantly lower in alendronate-treated patients, irrespective of the dose (P = 0.0003 and 0.01, respectively, for O.Th and OV/BV); however, mineral apposition rate was not altered. As anticipated, significant decreases of mineralizing surfaces (76% pooled alendronate group; P = 0.006), activation frequency (-72%; P = 0.004), and bone formation rate (-71%; P = 0.005) were also noted with alendronate treatment. No significant difference was noted between the changes observed with each dose. Absence of tetracycline label in trabecular bone was noted in approximately 4% of biopsies in placebo and alendronate-treated groups. Trabecular bone volume, parameters of microarchitecture, and resorption did not differ significantly between groups. In conclusion, alendronate treatment in patients on glucocorticoids decreased the rate of bone turnover, but did not completely suppress bone remodeling and maintained normal mineralization at all alendronate doses studied. Alendronate treatment did not influence the osteoblastic activity, which is already low in glucocorticoid-induced osteoporosis.     

Evaluation of recombinant human bone morphogenetic protein-2 as a bone-graft substitute in a canine segmental defect model.

A study was performed in dogs to evaluate the dose-response characteristics and effectiveness of recombinant human bone morphogenetic protein-2 with a collagen sponge carrier in a segmental defect model. Twenty-seven dogs underwent bilateral radial osteotomies with creation of a 2.5-cm diaphyseal defect. All received autogenous cancellous bone graft in one defect and a collagen implant in the other. These implants contained recombinant human bone morphogenetic protein-2 at the following doses: group 1 at 0 microg (three dogs, 0 microg/ml total implant volume), group 2 at 150 microg (three dogs, 50 microg/ml), group 3 at 600 ,g (three dogs, 200 microg/ml), group 4 at 2,400 microg (three dogs, 800 microg/ml), group 5 at 0 microg (five dogs, 0 microg/ml), group 6 at 150 microg (five dogs, 200 microg/ml), and group 7 at 600 microg (five dogs, 50 microg/ml). The defects were stabilized with external fixators. The dogs in groups 1-4 were killed at 12 weeks postoperatively, and those in groups 5-7 were killed at 24 weeks postoperatively except for one dog in group 7, which was killed at 48 weeks. Evaluation included monthly radiographs, biomechanical testing, and nondemineralized histology. All 27 radii with autogenous cancellous bone graft and all 19 implants treated with recombinant human bone morphogenetic protein-2 achieved radiographic and histologic union and gross stability. The eight radii treated with collagen carrier alone went on to radiographic and histologic nonunion and were grossly unstable at death. A dose-dependent occurrence of cyst-like bone voids was noted radiographically and histologically. Biomechanical performance tended to be better at the lowest dose studied at 12 weeks, and all three doses performed better than the placebo (p < 0.05) at 12 and 24 weeks. By 24 weeks, radiolucent areas corresponding to histologic bone voids persisted radiographically, although there was evidence of early bone remodeling. This remodeling progressed to 48 weeks in the single animal followed to this time point, although bone voids remained. These radiologic findings were confirmed histologically. Recombinant human bone morphogenetic protein-2 in a collagen sponge carrier has significant osteoinductive activity in this canine segmental defect model. A dose-response relationship is evident, with heterotopic bone and cyst-like void formation at higher doses and a minimum effective dose of 0-150 microg. At 12 and 24 weeks postoperatively, biomechanical parameters achieved by defects treated with recombinant human bone morphogenetic protein-2 were comparable with those of autograft controls and were significantly stronger than those of the placebo (p < 0.05).     

Pamidronate prevents bone loss associated with carrageenan arthritis by reducing resorptive activity but not recruitment of osteoclasts.

Carrageenan arthritis is associated with high-turnover bone loss. We sought to determine whether the bisphosphonate pamidronate can modify this effect of inflammatory arthritis. Sixty mature, New Zealand White rabbits were randomly assigned to five groups: normal; normal with a therapeutic dose of pamidronate (300 microg/kg/day, administered subcutaneously); arthritis (induced in the right tibiofemoral joint with 10 intraarticular carrageenan injections); arthritis with a therapeutic dose of pamidronate (300 microg/kg/day, subcutaneous); and arthritis with a low dose of pamidronate (7.5 microg/kg/day, subcutaneous). All animals received the fluorochrome calcein green (0.5 g/l/day) in drinking water ad libitum from days 21 to 49. Undecalcified, transverse sections of the distal femur were photographed or imaged to determine bone volume; new bone volume; resting, eroded, osteoid, and osteoblast perimeters; and osteoclast number. Results were evaluated with analysis of variance and pairwise Bonferroni's tests. In trabecular bone adjacent to the joint affected by carrageenan arthritis, resting perimeter was substantially reduced compared with normal joints, and primary indices of osteoblast and osteoclast activity were abnormally high (p < 0.001). Daily treatment with a therapeutic dose of pamidronate (300 microg/kg/day, subcutaneous) during the induction of arthritis significantly decreased new bone volume, osteoid perimeter, and osteoblast perimeter compared with the untreated arthritis group (p < 0.001). Osteoclast number and eroded perimeter remained abnormally high despite treatment with pamidronate. The concomitant increase of bone volume and these osteoclast indices show that pamidronate prevents bone loss in this model of experimental inflammatory arthritis by inhibiting the resorptive activity, but not the formation or recruitment, of osteoclasts. These findings are relevant to the use of bisphosphonates in the treatment of rheumatoid arthritis.     

Locally applied simvastatin promotes bone formation in a rat model of spinal fusion

Simvastatin, an inexpensive lipid‐lowering drug widely used to prevent cardiovascular disorders, is known to increase osteoblastic activity, inhibit osteoclastic activity, and stimulate osteoblastic production of bone morphogenetic protein 2. Furthermore, local simvastatin application increased bone formation in animal models of fracture or bone defects. We investigated the effect of locally applied simvastatin in a rat model of spinal fusion. We performed posterolateral lumbar fusion surgery with iliac crest autograft in 36 rats divided into group I (n = 17; implanted with a gelatin scaffold) and group II (n = 19; implanted with a gelatin scaffold infused with 0.5 mg simvastatin). The rats were euthanized at 6 or 12 weeks postoperatively, and the spines were explanted and assessed. The fusion rates in group II (16.7%: 6 weeks, 30%: 12 weeks) were considerably higher than those in groups I (0%: 6 weeks, 0%: 12 weeks). The 6‐ and 12‐week radiographic scores were significantly higher in group II than in group I. High‐resolution micro‐computerized tomography revealed that the tissue and bone volumes of the callus tended to be higher in group II than in group I. Histologic analysis of the spines explanted after 12 weeks demonstrated new bone formation between the transverse processes in group II, but thicker and wider individual trabeculae with fibrotic tissue and muscle fiber between the transverse processes in group I. Locally applied simvastatin was efficacious in accelerating bone formation in our rat model of spinal fusion, supporting its potential clinical application as a promoter of bone morphogenesis in spinal fusion. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1942–1948, 2017.