Effect of slow-release sodium fluoride on cancellous bone histology and connectivity in osteoporosis

Glucocorticoid-induced osteoporosis: treatment update and review

Glucocorticoid-induced osteoporosis (GIO) is a serious consequence of glucocorticoid therapy leading to fractures in 30-50% of patients. A wide range of protective medications have been studied in this condition including calcium, vitamin D, vitamin D analogs, oral and intravenous bisphosphonates, sex hormones, anabolic agents and calcitonin. The mechanism of action, and evidence for these therapies, are reviewed - focusing on important trials and new evidence. Recently published guidelines are also reviewed and compared. Bisphosphonates are currently the recommended first-line therapy for the prevention and treatment of GIO. They have been shown to increase bone mineral density (BMD) at the spine and hip and to decrease the incidence of vertebral fractures (especially in postmenopausal women). Testosterone therapy and female hormone replacement therapy (HRT) have been found to increase lumbar spine BMD in hypogonadal patients on glucocorticoid therapy, but effects on hip BMD have not been consistent and there is no fracture data in the GIO population. Similarly, calcitonin increases lumbar spine BMD but has no proven fracture efficacy. The effect of selective estrogen receptor modulators, the oral contraceptive pill and strontium on GIO is relatively unknown. Parathyroid hormone (PTH 1-34) and zoledronic acid have emerged as exciting new options for the treatment of GIO. Both therapies have been found to result in gains in BMD at the spine and hip that are either noninferior or superior to those seen with oral bisphosphonate therapy. PTH 1-34 has also been found to decrease the incidence of new vertebral fractures and may be an option in high-risk patients established on long-term glucocorticoid therapy.

In vitro and in vivo evidence for stimulation of bone resorption by an EP4 receptor agonist and basic fibroblast growth factor: Implications for their efficacy as bone anabolic agents

Prostaglandin E2 receptor subtype 4 agonists (EP4A) and basic fibroblast growth factor (FGF2) stimulate bone formation, but their effects on bone resorption are controversial. To provide additional insight into the skeletal effects of EP4A and FGF2, their regulation of expression of genes associated with bone formation and resorption in aged ovariectomized (OVX) rats and in cultured mouse bone marrow cells was determined. RNA was isolated from lumbar vertebrae of OVX rats (16 months of age) treated daily for 3 weeks with FGF2 or EP4A and processed for quantitative real time-PCR analyses. mRNA expression for the receptor activator of NF-kappaB ligand (RANKL) and cathepsin K (CTSK), but not osteoprotegerin (OPG), were upregulated by both FGF2 and EP4A. Addition of FGF2 and EP4A to the medium of cultured mouse bone marrow cells increased the formation of tartrate resistant acid phosphatase (TRAP) positive cells, upregulated the expression of RANKL and CTSK, and downregulated expression for OPG. EP4A also increased the formation of actin rings, an indicator of osteoclast activation, in a dose dependent manner in osteoclasts cultured on bone slices and triggered the formation of pits as revealed by a pitting assay. Gene expression for osterix (OSX) and IGF-2, genes associated with bone formation, was significantly greater in FGF2-treated OVX rats compared with EP4A-treated OVX rats. These findings at the molecular level are consistent with previous tissue-level histomorphometric findings, and at the doses tested, support the contention that FGF2 has a stronger bone anabolic effect than EP4A. The results of these in vivo and in vitro analyses clarify the effects of FGF2 and EP4A on bone formation and resorption, and provide insight into differences in the efficacy of two potential bone anabolic agents for restoration of lost bone mass in the osteopenic, estrogen-deplete skeleton.

Addition of monofluorophosphate to estrogen therapy in postmenopausal osteoporosis: a randomized controlled trial

INTRODUCTION

Treatment of osteoporosis with high-dose fluoride alone does not reduce fracture risk. We hypothesized that the antifracture efficacy of fluoride could be optimized by its use in low doses combined with an antiresorptive agent.

EXPERIMENTAL SUBJECTS

Subjects included 80 women with postmenopausal osteoporosis who had been taking estrogen for at least 1 yr.

METHODS

Subjects were randomized to receive monofluorophosphate (MFP) (fluoride content of 20 mg/d) or placebo over 4 yr in a double-blind trial.

RESULTS AND DISCUSSION

There were progressive increases in lumbar spine bone density over the duration of the study (MFP, 22%; placebo, 6%; P < 0.0001). In the trabecular bone of L3, these increases were even greater (MFP, 49%; placebo, 2.5%; P < 0.0001). In the proximal femur, there were smaller but significant treatment effects (P = 0.015). Total body scans and their subregions also showed significantly greater increases in the MFP group. Bone formation markers increased significantly in the MFP group at yr 1. Hyperosteoidosis was present in biopsies from five of seven MFP subjects, with osteomalacia in two of seven. The hazards ratio for vertebral fractures was 0.20 (95% confidence interval, 0.05-1.30), and the incidence rate ratio was 0.12 (95% confidence interval, 0.06-0.23; P < 0.01). The hazards ratio for nonvertebral fractures was 3.3 (95% confidence interval, 0.8-12.0).

CONCLUSIONS

We conclude that fluoride at 20 mg/d produces substantial increases in bone mineral density but still interferes with bone mineralization. This indicates that most previous studies with this ion have used toxic doses and that much lower doses should be assessed to find a safe dose window for the use of this powerful anabolic agent.

Selected extraskeletal effects of systemic treatment with basic fibroblast growth factor in ovariectomized rats

Basic fibroblast growth factor (bFGF) is a pleiotropic mitogen with a potent bone-forming effect, rendering it a potential osteoporosis therapy. This study examined selected extraskeletal effects of bFGF in ovariectomized rats, a well-established model of human postmenopausal osteopenia, to more fully characterize side effects associated with bFGF treatment. Five-month-old, osteopenic, ovariectomized rats were injected subcutaneously with vehicle or bFGF (1 mg/kg) daily for 3 weeks. Hematologic and biochemical analyses were performed; and kidneys, livers, and proximal tibiae were examined histologically and histomorphometrically. bFGF administration resulted in anemia that was due to a shift toward granulocyte production in the bone marrow. Increased granulocyte production was also observed in the liver of bFGF-treated rats, which exhibited a markedly increased number and area of hematopoietic foci. bFGF administration also caused mild glomerular hypertrophy that was not attended by significant biochemical evidence of glomerular dysfunction. The bone anabolic effect of subcutaneous bFGF administration was confirmed in the proximal tibia, and was associated with a significant decrease in urine fractional excretion of calcium in bFGF-treated rats. Though bFGF strongly stimulates bone formation at osteopenic skeletal sites, its extraskeletal effects may restrict the long-term use of bFGF in its current form as an osteoporosis therapy.

Histopathologic changes in metabolic bone disease

Metabolic bone disease encompasses a heterogeneous group of disorders that influence skeletal metabolism and structure. They are generally diagnosed at an advanced stage and manifest clinically with stunted skeletal growth in children and pathologic fractures in adults. Biochemical markers for bone metabolism are equivocal and microscopic examination of labeled bone remains the gold standard for the diagnosis and accurate monitoring of the response to therapy. This article reviews the role of microscopic bone changes in the diagnosis and management of metabolic bone disease.

Anabolic action of parathyroid hormone on cortical and cancellous bone differs between axial and appendicular skeletal sites in mice

The mouse is being increasingly used to study the anabolic action of parathyroid hormone (PTH) on the skeleton. The efficacy of intermittent PTH treatment on bone varies widely among tested strains of mice with differences in peak bone mass and structure. We have therefore examined the responses of skeletal sites with high or low cancellous bone mass to PTH treatment in a single strain with genetically low bone mass. Mature C57BL/6 mice were ovariectomized (ovx) or sham operated and, after 4 weeks, treated with PTH(1-34) (40 microg/kg/day, 5 days/week sc) or vehicle for 3 or 7 weeks. Two doses of fluorescent labels were given to the animals 9 and 3 days before euthanasia. Histomorphometry was performed on sections of the proximal tibia, tibial diaphysis, and vertebral body. The results indicate that 4 to 11 weeks of ovx induced a approximately 44% loss of cancellous bone in the proximal tibia and a approximately 25% loss of cancellous bone in the vertebra with impaired trabecular architecture and high bone turnover. In the intact animals, PTH increased cancellous bone volume to a greater extent in the vertebral body than in the proximal tibia, a site with lower cancellous bone volume at the outset. In the ovx mice, PTH increased cancellous bone volume to a greater extent in the vertebral body, a site displaying moderate cancellous bone loss, than in the proximal tibia, a site with severe cancellous bone loss. Conversely, the treatment added a little cortical bone to the tibia, a highly loaded site, but did not significantly increase cortical width of the vertebral body, a less loaded site. We conclude that, for intermittent PTH treatment to be maximally effective, there must be an adequate number of trabeculae present at the beginning of treatment, regardless of estrogen status. Our results also support an interaction between PTH anabolic action and mechanical loading.

Sequential treatment with basic fibroblast growth factor and PTH is more efficacious than treatment with PTH alone for increasing vertebral bone mass and strength in osteopenic ovariectomized rats

The study was designed 1) to determine whether treatment with basic fibroblast growth factor (bFGF) and PTH is more efficacious than treatment with PTH alone for increasing bone mass and strength and improving trabecular microarchitecture in osteopenic ovariectomized rats, and 2) to assess whether prior and concurrent administration of the antiresorptive agents estrogen and risedronate suppresses the bone anabolic response to treatment with bFGF alone and sequential treatment with bFGF and PTH. Three-month-old female Sprague Dawley rats were ovariectomized (OVX) or sham-operated (sham) and maintained untreated for 1 yr. Baseline sham and OVX rats were killed at this time (15 months of age). Groups of rats were injected sc with estrogen (10 microg/kg, 4 d/wk), risedronate (5 microg/kg, 2 d/wk), or vehicle. At the end of the second week of antiresorptive treatment, catheters were inserted into the jugular veins of all rats, and vehicle or bFGF at a dose of 250 microg/kg was injected daily for 14 d. Three groups of rats were killed at the end of bFGF treatment. The remaining rats were continued on their respective antiresorptive therapy and injected sc with vehicle or synthetic human PTH-(1-34) at a dose of 80 microg/kg, 5 d/wk, for 8 wk. Lumbar vertebrae were processed for cancellous bone histomorphometry and biomechanical testing. Ovariectomy resulted in a decrease in vertebral bone mass and strength. Treatment of OVX rats for 14 d with bFGF markedly increased osteoblast surface, osteoid surface, and osteoid volume compared with vehicle treatment of sham and OVX rats. Furthermore, osteoid bridges were observed extending between preexisting trabeculae in bFGF-treated OVX rats. Prior and concurrent administration of estrogen and risedronate did not suppress these bone anabolic effects of bFGF. Treatment of OVX rats with PTH alone increased vertebral cancellous bone mass and strength to the level of vehicle-treated sham rats. Sequential treatment of OVX rats with bFGF and PTH further augmented vertebral bone mass and strength to a level above that observed in OVX rats treated with PTH alone. The improvements in bone mass and strength were associated with an increase in trabecular thickness in OVX rats treated with PTH alone and with an increase in trabecular thickness and node to terminus ratio, an index of trabecular connectivity, in OVX rats treated sequentially with bFGF and PTH. Cotreatment with estrogen and risedronate did not suppress the anabolic response of bone to bFGF and PTH. In fact, a trend for an even greater increase in cancellous bone mass and node to terminus ratio was observed in OVX rats treated with risedronate, bFGF, and PTH. These findings indicate that sequential treatment with bFGF and PTH is more efficacious than treatment with PTH alone for increasing bone mass and strength and improving trabecular microarchitecture in osteopenic OVX rats.

Sequential treatment with basic fibroblast growth factor and parathyroid hormone restores lost cancellous bone mass and strength in the proximal tibia of aged ovariectomized rats

This study was designed to determine whether sequential treatment with basic fibroblast growth factor (bFGF) and parathyroid hormone (PTH) can restore lost cancellous bone mass and strength at a severely osteopenic skeletal site in aged ovariectomized (OVX) rats. Female Sprague-Dawley rats were subjected to sham surgery or ovariectomy at 3 months of age and maintained untreated for the first year after surgery. At 15 months of age, groups of baseline control and OVX rats were killed and catheters were inserted in the jugular veins of all remaining rats. Two groups of OVX rats were injected intravenously (iv) daily with bFGF for 14 days at a dose of 200 microg/kg body weight. At the end of bFGF treatment, one group was killed whereas the other group was subjected to 8 weeks of treatment with synthetic human PTH 1-34 [hPTH(1-34)] consisting of subcutaneous (sc) injections 5 days/week at a dose of 80 microg/kg. Another group of OVX rats was treated iv with vehicle for 2 weeks followed by treatment with PTH alone for 8 weeks. Other groups of sham-operated control rats and OVX rats were treated iv and sc with vehicle alone. The right proximal tibia from each rat was processed undecalcified for quantitative bone histomorphometry and the left proximal tibia was subjected to biomechanical testing. Baseline and vehicle-treated OVX rats were severely osteopenic because their tibial cancellous bone volumes were less than 5% compared with mean values of 20.3% and 15.0% in baseline and vehicle-treated control rats, respectively. Treatment of OVX rats for 2 weeks with bFGF alone did not significantly increase tibial cancellous bone volume but induced marked increases in osteoid volume, osteoblast surface, and osteoid surface. Sequential treatment of aged OVX rats with bFGF and PTH increased tibial cancellous bone volume (15.1%) and load to failure to at least the level of vehicle-treated control rats. Tibial cancellous bone volume (10.8%) and load to failure also were significantly increased by treatment with PTH alone, and these variables were not significantly different from those of OVX rats treated with bFGF + PTH. However, tibial ash density was significantly greater in OVX rats treated sequentially with bFGF and PTH compared with OVX rats treated with PTH alone. Our findings suggest that sequential treatment with bFGF and PTH may be useful for restoration of lost cancellous bone in the severely osteopenic, estrogen-deplete skeleton, but it cannot be concluded with certainty that this sequential treatment has a greater bone restorative effect than treatment with PTH alone.

Fluoride for treating postmenopausal osteoporosis

OBJECTIVES

To assess the efficacy of fluoride therapy on bone loss, vertebral and non-vertebral fractures and side effects in postmenopausal women.

SEARCH STRATEGY

We searched Medline, Current Contents and the Cochrane Controlled Trial Registry up to December 1998.

SELECTION CRITERIA

Two independent reviewers selected RCTs which met predetermined inclusion criteria.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data using predetermined forms and assessed the methodological quality of the trials using a validated scale. For dichotomous outcomes, relative risks (RR) were calculated and for continuous outcomes, weighted mean differences (WMD) of percentage change from baseline were calculated. Where heterogeneity existed (determined by a chi-square test) a random effects model was used.

MAIN RESULTS

Eleven studies (1429 subjects) met the inclusion criteria. The increase in lumbar spine bone mineral density (BMD) was found to be higher in the treatment group than in the control group with a WMD 8.1% (95%CI: 7.15,9.09) after two years of treatment and 16.1%(95%CI: 14.65,17.5) after four years. The RR for new vertebral fractures was not significant at two years [0.87 (95%CI: 0.51,1.46)] or at four years [0.9(95%CI: 0.71,1.14)]. The RR for new non-vertebral fractures was not significant at two years 1.2(95%CI: 0.68,2.1) but was increased at four years in the treated group 1.85(95%CI: 1.36,2.5), especially if used at high doses and in a non slow release form. The RR for gastrointestinal side effects was not significant at two years 2.18(95%CI: 0.86,1.21) but was increased at four years in the treated group 2.18(95%CI: 1.69,4.57) especially if fluoride was used at high doses and in a non slow release form. The number of withdrawals and dropouts was not different between treated and control groups at two and four years.

REVIEWER'S CONCLUSIONS

Although fluoride has an ability to increase BMD at lumbar spine, it does not result in a reduction of vertebral fractures. In increasing the dose of fluoride, one increases the risk of non-vertebral fracture and gastrointestinal side effects without any effect on the vertebral fracture rate.

Bone anabolic effects of basic fibroblast growth factor in ovariectomized rats

The purpose of this study was to characterize the bone anabolic effects of basic fibroblast growth factor (bFGF) in ovariectomized (OVX) rats. Female Sprague Dawley rats were subjected to ovariectomy or sham surgery at 3 months of age and maintained untreated for 2 months post surgery. Groups of OVX rats were then treated iv with bFGF at doses of 100 or 200 microg/kg day for 7 or 14 days. Another group of OVX rats and a group of sham-operated control rats were treated iv with vehicle alone for 14 days. Certain groups of bFGF-treated OVX rats were killed at 7 or 14 days after withdrawal of treatment. The right tibiae were processed undecalcified for quantitative bone histomorphometry. Vehicle-treated OVX rats were characterized by decreased cancellous bone volume associated with increased bone turnover. Treatment of OVX rats with bFGF strongly stimulated bone formation, as indicated by marked increases of at least a factor of 10 in osteoblast surface, osteoid surface, and osteoid volume. Furthermore, new osteoid spicules were observed within the marrow cavity of these animals. Osteoclast surface was markedly decreased in bFGF-treated OVX rats, but this finding may be secondary to the extensive osteoid surface. The strongest bone anabolic effects occurred in OVX rats treated with the higher dose of bFGF for 14 days, but these animals exhibited a bone mineralization defect, as evidenced by abundant osteoid and a lack of double fluorochrome labeling, despite markedly increased osteoblast surface. However, the newly-formed osteoid rapidly calcified after withdrawal of bFGF treatment. The data indicate that bFGF not only stimulates bone formation on pre-existing bone surfaces but also induces de novo formation of bone spicules within the marrow cavity, which results in partial restoration of lost cancellous bone mass in osteopenic OVX rats after only 14 days of treatment with the growth factor. These findings suggest that bFGF merits consideration for development as a potential treatment for patients with severe osteopenia who are unresponsive to conventional osteoporosis therapies.

The effects of twelve weeks of bed rest on bone histology, biochemical markers of bone turnover, and calcium homeostasis in eleven normal subjects

This study was undertaken to examine the effects of 12 weeks of skeletal unloading on parameters of calcium homeostasis, calcitropic hormones, bone histology, and biochemical markers of bone turnover in 11 normal subjects (9 men, 2 women; 34 +/- 11 years of age). Following an ambulatory control evaluation, all subjects underwent 12 weeks of bed rest. An additional metabolic evaluation was performed after 12 days of reambulation. Bone mineral density declined at the spine (-2.9%, p = 0.092) and at the hip (-3.8%, p = 0.002 for the trochanter). Bed rest prompted a rapid, sustained, significant increase in urinary calcium and phosphorus as well as a significant increase in serum calcium. Urinary calcium increased from a pre-bed rest value of 5.3 mmol/day to values as high as 73 mmol/day during bed rest. Immunoreactive parathyroid hormone and serum 1,25-dihydroxyvitamin D declined significantly during bed rest, although the mean values remained within normal limits. Significant changes in bone histology included a suppression of osteoblastic surface for cancellous bone (3.1 +/- 1.3% to 1.9 +/- 1.5%, p = 0.0142) and increased bone resorption for both cancellous and cortical bone. Cortical eroded surface increased from 3.5 +/- 1.1% to 7.3 +/- 4.0% (p = 0.018) as did active osteoclastic surface (0.2 +/- 0.3% to 0.7 +/- 0.7%, p = 0.021). Cancellous eroded surface increased from 2.1 +/- 1.1% to 4.7 +/- 2.2% (p = 0.002), while mean active osteoclastic surface doubled (0.2 +/- 0.2% to 0.4 +/- 0.3%, p = 0.020). Serum biochemical markers of bone formation (osteocalcin, bone-specific alkaline phosphatase, and type I procollagen extension peptide) did not change significantly during bed rest. Urinary biochemical markers of bone resorption (hydroxyproline, deoxypyridinoline, and N-telopeptide of type I collagen) as well as a serum marker of bone resorption (type I collagen carboxytelopeptide) all demonstrated significant increases during bed rest which declined toward normal during reambulation. Thus, under the conditions of this study, the human skeleton appears to respond to unloading by a rapid and sustained increase in bone resorption and a more subtle decrease in bone formation.

Fluoride potentiates the osteogenic effects of IGF-I in aged ovariectomized rats

The molecular mechanisms whereby fluoride stimulates osteogenic cell proliferation are not clearly established. However, fluoride has been shown to enhance the protein tyrosine phosphorylation of various constituents of intracellular signaling cascades in osteoblastic cells following stimulation of growth factor receptors such as the insulin-like growth factor-I (IGF-I) receptor. Such in vitro findings provided the rationale for testing whether the administration of fluoride could enhance IGF-I effects on bone mass in vivo. Adult ovariectomized osteopenic rats were treated with sodium fluoride at a dose of 6 mg/kg per day in drinking water for 8 weeks in association with IGF-I either at a dose of 2 mg/kg per day, which is capable of increasing bone mass, or at a lower dose without detectable skeletal effects. Bone mineral density (BMD) and content (BMC) were evaluated by dual-energy X-ray absorptiometry at the levels of the lumbar spine and proximal, midshaft, and total tibia before and after 8 weeks of treatment. During this period, fluoride alone did not significantly influence BMD/BMC at any skeletal site. However, it potentiated the effect of the higher dose of IGF-I on bone mass at the level of the proximal tibia. When administered in combination with the lower dose of IGF-I, which per se did not modify bone mass, it appeared to sensitize tibial bone to the effects of IGF-I. These changes were associated with a concomitant increase in osteocalcin, taken as a reflection of bone formation. These results indicate that fluoride could potentiate the osteogenic effects of IGF-I on bone in adult ovariectomized rats.

Reflection ultrasound velocities and histomorphometric and connectivity analyses: correlations and effect of slow-release sodium fluoride

To better understand how structural and functional bone properties contribute to the changes in bone biomechanical properties revealed by ultrasound critical angle reflectometry (UCR) analysis, we measured both UCR velocities and histomorphometric properties in bone biopsy specimens from 33 osteoporotic patients before and following intermittent slow-release sodium fluoride (SRNaF) and continuous calcium citrate administration. Mean skeletal fluoride exposure was 17 months, and mean skeletal fluoride content was 0.203 +/- 0.088 SD% bone ash. Intermittent SRNaF and continuous calcium citrate promoted significant increases in trabecular thickness (122 +/- 18 SD microm to 131 +/- 20, p = 0.020), mineral apposition rate (0.79 +/- 0.26 to 1.05 +/- 0.40 microm/day, p = 0.014), and a significant decline in eroded surface (3.9 +/- 1.6 to 2.8 +/- 1.4%, p = 0.002). There were also significant increases in node number (0.193 +/- 0.100 to 0.368 +/- 0.245, p < 0.01) and node-to-node strut length (0.076 +/- 0.087 to 0.191 +/- 0.173, p < 0.01) relative to total cancellous area. Cortical UCR velocity did not change but cancellous velocity significantly increased by 97 m/s following therapy (p = 0.0005). When compared against the significant changes in bone histomorphometry and connectivity, the sum of both cancellous and cortical ultrasound velocities was significantly correlated with node number/area (R2 = 0.305, p < 0.0001) and node-to-node strut length/area (R2 = 0.372, p < 0.0001) and to a lesser extent with mineral apposition rate (R2 = 0.106, p = 0.032). Multiple regression analysis demonstrated that 40% of the variance in the sum of the UCR velocities can be accounted for by the variability in these histomorphometric and connectivity parameters. There were no significant correlations between the sum of cortical and cancellous ultrasound velocities and cancellous bone volume (R2 = 0.014, p = 0533), trabecular thickness (R2 = 0.012, p = 0.47), or bone mineral density (R2 = 0.003, p = 0.80). These observations indicate that velocity measurements with the UCR methodology show an improvement in bone elasticity associated, in part, with an improvement in the rate of bone mineralization and an improvement in bone quality at the structural level as shown by microarchitecture.

Hydroxyapatite and fluorapatite coatings for fixation of weight loaded implants

Survivor analysis of total hip replacement recently has shown disappointing results in younger patients. To improve this, ceramic coatings have been applied to prostheses for cementless use. A new fluorine containing coating, fluorapatite, has been shown to increase bone ingrowth compared with hydroxyapatite in unloaded models. In a weight loaded model, the effects of hydroxyapatite and fluorapatite coated implants on implant fixation and bone ingrowth were evaluated. Eight hydroxyapatite and fluorapatite coated implants with porous surface were inserted into the medial femoral condyles of 8 mature dogs in a paired design. The implants initially were surrounded by a gap communicating with the joint space and were loaded during each gait cycle. After 25 weeks, no differences in pushout data or bone ingrowth between hydroxyapatite and fluorapatite coated implants were found. An important finding was the absence of foreign body reaction in the bone. Neither hydroxyapatite nor fluorapatite coatings delaminated during implantation or as a result of the pushout test. Bone repair activity remained in the initial gap zone, but most of the bone was of the lamellar type. No difference in bone remodeling between the hydroxyapatite and fluorapatite coated implants was found in the initial gap zone. Microprobe analysis showed no increase in fluorine content around the fluorapatite coated implants. The hydroxyapatite and fluorapatite coatings seem efficacious after a 25-week implantation period under weight loaded conditions.

Fewer bone histomorphometric abnormalities with intermittent than with continuous slow-release sodium fluoride therapy

To help resolve the uncertainty whether sodium fluoride (NaF) therapy should be given intermittently or continuously, we examined iliac crest bone biopsies (before and after treatment) and fragility fracture rates in 35 intermittently treated (group I) and 69 continuously treated (group C) patients; all received calcium. The following statistically significant results were obtained. Reduction in vertebral fracture rate was similar in the two groups. Trabecular thickness and the structurally more important mineralized thickness increased only in group I. Group I also accumulated less excess osteoid (surface, volume). Mean osteoid thickness did not change in either group because of a bimodal distribution of wide seams with osteoblasts and double tetracycline labels, and thin seams without osteoblasts or labels. Osteoid was lamellar. Osteoid in abnormal sites (within bone marrow or bone, or around osteocytes) was found less frequently in group I. Adjusted apposition rate declined and mineralization lag time increased in both groups because of extended unlabelled osteoid seams. Erosion surface increased only in group C. Hook and/or tunnel erosion was seen less frequently in group I; it was closely associated with osteoid in abnormal sites and correlated with osteoid surface. Extended osteoid surface may have forced osteoclasts to hollow out trabeculae, leaving the empty osteoid shell in marrow. Excess osteoid volume and eroded surface and osteoid and erosion in abnormal sites correlated with bone fragility in group C. We conclude that intermittent therapy is to be preferred because it (1) increased mineralized trabecular thickness, (2) did not cause excessive osteoid accumulation and erosion, (3) showed less osteoid and erosion in abnormal sites and (4) led to a similar reduction in the vertebral fracture rate as did continuous treatment. The question of whether intermittency of therapy has some other effect independent of the cumulative dose of fluoride administered cannot be answered by this study.

Comparison of nonrandomized trials with slow-release sodium fluoride with a randomized placebo-controlled trial in postmenopausal osteoporosis

The results of slow-release sodium fluoride (SR-NaF) treatment in two nonrandomized trials involving 65 patients with postmenopausal osteoporosis from the primary site and 121 patients from collaborative sites were compared with those obtained from 54 treated patients and 56 patients taking placebo from a randomized controlled trial. Spinal fracture data were analyzed separately in mild to moderate bone loss of lumbar spine (baseline L2-L4 bone density [BD] > or = 65% young normal) and in severe bone loss (BD < 65%). Since demographic and fracture data were similar among fluoride-treated patients from the three trials at each stratum of bone loss, their data were combined. In mild to moderate bone loss, SR-NaF treatment in the combined group virtually eliminated new spinal fractures with 96.6% of patients remaining fracture-free. The Fluoride group had a markedly lower individual vertebral fracture rate (0.025 vs. 0.188/patient year, p = 0.0001) and group vertebral fracture rate (0.029 vs. 0.175/patient year, relative risk [RR] 0.12, p = 0.0001) than the Placebo group. In severe bone loss, the combined treated group had a significantly lower new spinal fracture rate than the Placebo group, although the differences were not as marked (group vertebral fracture rate of 0.150 vs. 0.276/patient year, RR 0.54, p = 0.03). In the combined fluoride-treated group, the L2-L4 bone mass rose by 4-6%/year for 4 years, and the femoral neck BD increased by 1-2%/year during first 2 years. The radial shaft BD did not change. The Placebo group did not show a change in bone mass at any site. The prevalence (percentage) of patients with related gastrointestinal side effects and nonvertebral fracture rates did not differ significantly between the combined SR-NaF group and the Placebo group (hip fracture rate of 0.0045/patient year in SR-NaF and 0.0053/patient year in Placebo; appendicular fracture other than hip (see text) rate of 0.0193/patient year in SR-NaF and 0.0159/patient year in Placebo). A subgroup analysis showed a low baseline L2-L4 BD, high prevalent spinal fractures, and reduced body weight to be important determinants of the development of spinal fracture during SR-NaF treatment. Concomitant medications (estrogen, vitamin D, thiazide and thyroid hormone) were not independent predictors of the spinal fracture risk. Only 17% of fluoride-treated patients were nonresponders (new spinal fractures or a fall/no change in L2-L4 bone mass). Thus, the effects of SR-NaF treatment on the spinal fracture rate from nonrandomized trials were similar to those of the treated group of the randomized trial but different from those of the Placebo group. The similarity of response of nonrandomized trials with that of the randomized controlled trial and the resultant combined analysis further validate the efficacy and safety of SR-NaF in the treatment of postmenopausal osteoporosis.