Once-weekly teriparatide increases bone mineral density in the distal 1/10 radius, but not in the distal 1/3 radius

The effect of forearm rotation on the bone mineral density measurements of the distal radius

INTRODUCTION

Forearm dual-energy X-ray absorptiometry (DXA) is often performed in clinics where central DXA is unavailable. Accurate bone mineral density (BMD) measurement is crucial for clinical assessment. Forearm rotation can affect BMD measurements, but this effect remains uncertain. Thus, we aimed to conduct a simulation study using CT images to clarify the effect of forearm rotation on BMD measurements.

MATERIALS AND METHODS

Forearm CT images of 60 women were analyzed. BMD was measured at the total, ultra-distal (UD), mid-distal (MD), and distal 33% radius regions with the radius located at the neutral position using digitally reconstructed radiographs generated from CT images. Then, the rotation was altered from - 30° to 30° (supination set as positive) with a one-degree increment, and the percent BMD changes from the neutral position were quantified for all regions at each angle for each patient.

RESULTS

The maximum mean BMD changes were 5.8%, 7.0%, 6.2%, and 7.2% for the total, UD, MD, and distal 33% radius regions, respectively. The analysis of the absolute values of the percent BMD changes from the neutral position showed that BMD changes of all patients remained within 2% when the rotation was between - 5° and 7° for the total region, between - 3° and 2° for the UD region, between - 4° and 3° for the MD region, and between - 3° and 1° for the distal 33% radius region.

CONCLUSION

Subtle rotational changes affected the BMD measurement of each region. The results showed the importance of forearm positioning when measuring the distal radius BMD.

Impact of reference point selection on DXA-based measurement of forearm bone mineral density

Few studies have systematically evaluated the technical aspects of forearm bone mineral density (BMD) measurement. We found that BMD remained stable regardless of the reference point; however, the ROI identified was not always consistent. Our study highlights the importance of using the same reference point for serial measurements of forearm BMD.

BACKGROUND

Forearm fractures are clinically important outcomes from the perspective of morbidity, health care costs, and interruption of work. BMD of the forearm, as derived by dual-energy x-ray absorptiometry (DXA), is a better predictor of fracture at the forearm compared with BMD measured at other sites. However, very few studies have evaluated the technical aspects of selecting the ROI for forearm BMD measurement. This study aimed to compare the BMD values measured at the 1/3 radius site using three different reference points: the ulnar styloid process, the radial endplate, and the bifurcation of the ulna and radius.

METHODOLOGY

Healthy Chinese patients participating in the control group of an ongoing study at Zhejiang Provincial People's Hospital were recruited for this study. For each patient, a DXA scan (GE Lunar Prodigy) of the forearm was performed and BMD values were separately calculated using each of the three reference points to identify the ROI. Pearson correlation coefficients were calculated to examine the correlation between the BMD measures derived from each reference point. The F test and independent t test were applied for more robust analysis of the differences in the variances and means.

RESULTS

Sixty-eight healthy Chinese volunteers agreed to participate in this study. The root mean square standard deviation (RMS-SD) percentages of BMD values measured at the 1/3 radius site were 2.19%, 2.23%, and 2.20% when using the ulnar styloid process, radial endplate, and the bifurcation of the ulna and radius as the reference points, respectively. Pearson's correlation coefficients for all pairwise comparisons among these three groups were greater than 0.99. F tests and independent t tests showed p values ranging from 0.92 to 0.99. However, we observed that among 10% of patients, choosing an ROI at the ulnar styloid process led to an inability to accurately determine the BMD at the ultra-distal radius.

CONCLUSIONS

Given equal ability to determine BMD at the 1/3 radius accurately, the radial endplate or the bifurcation of the ulna and radius should be preferentially selected as the reference point for routine forearm BMD measurements in order to avoid situations in which the ultra-distal radius BMD cannot be determined.

Utility of radius bone densitometry for the treatment of osteoporosis with once-weekly teriparatide therapy

Objectives

As clinics that treat patients with osteoporosis do not usually have central dual-energy X-ray absorptiometry (DXA), bone density is often measured with radial DXA. However, no long-term evidence exists for radius bone density outcomes following treatment with once-weekly teriparatide in actual medical treatment.

Methods

We evaluated changes in bone density at 6-, 12-, and 18-month intervals using radial DXA in patients treated with once-weekly teriparatide for more than 6 months.

Results

A significant increase in bone mineral density (BMD) was observed at the 1/3 and 1/10 radius sites 12 months after the initiation of once-weekly teriparatide. We also observed that the rate of change in BMD was greater at the distal 1/10 radius than at the 1/3 radius.

Conclusions

Considering these points, the effect of once-weekly teriparatide therapy can be observed at the radius. In clinics that do not have central DXA, but instead have radial DXA, these findings can help to evaluate the effect of once-weekly teriparatide treatment on osteoporosis.

24-Month Open-Label Teriparatide Once-Weekly Efficacy Research Trial Examining Bone Mineral Density in Subjects with Primary Osteoporosis and High Fracture Risk

Introduction

To clarify the additional efficacy and safety benefits of 24 months’ treatment with the once-weekly formulation of teriparatide, which is currently used for 72 weeks.

Methods

This was a multicenter, open-label, single-arm study conducted in Japan. Subjects who were 65 years or older with prevalent vertebral fractures received once-weekly subcutaneous injection of 56.5 μg teriparatide for 24 months. The main outcome measure was percentage change from baseline in lumbar (L2–L4) BMD measured by dual-energy X-ray absorptiometry.

Results

A total of 189 subjects received at least one dose of the once-weekly formulation of teriparatide. Lumbar, femoral neck, and total hip BMD increased significantly compared with baseline at Weeks 24, 48, 72, and 104. In addition, significant increases in lumbar (+1.5%) and femoral neck (+0.8%) BMD were noted at Week 104 compared with Week 72. Significant increases from baseline in BMD for radius 1/10 were noted at Weeks 24 and 104. No substantial increases were noted in the cumulative incidences of new vertebral fracture and other types of fracture after Week 72. The safety profile seen in the first 72 weeks remained unchanged until 104 weeks.

Conclusion

The once-weekly formulation of teriparatide is effective and safe for the treatment of osteoporosis over 24 months. The limitation of this study is that this was an open-label, single-arm study.

Funding: Asahi Kasei Pharma Corporation.

Clinical Trial Registration: JapicCTI-132276.

Treatment responses with once-weekly teriparatide therapy for osteoporosis

Monitoring bone mineral density is useful to assess treatment response for osteoporosis, but it does not always reflect fracture prevention. Two types of bone mineral density thresholds were used to analyze data from a once-weekly teriparatide trial, and they appear to be useful indicators of treatment success for osteoporosis.

INTRODUCTION

This study aimed to clarify whether the criteria of treatment response could be used to evaluate treatment success with once-weekly teriparatide.

METHODS

The data of subjects whose lumbar or femoral neck bone mineral density (BMD) was measured in the TOWER study were included. The least significant change (LSC) and the absolute change were used as the criteria for judgment of treatment success. The correlation between the incidence of fractures and the treatment response was also assessed.

RESULTS

There was no significant difference in baseline characteristics between the placebo and teriparatide groups. Once-weekly teriparatide therapy for 72 weeks showed treatment success in 79.2 % of the subjects for lumbar BMD and 44.1 % for femoral neck BMD by LSC and in 50.5 and 39.6 % by absolute change, respectively. A lower incidence of vertebral fracture was observed in patients who achieved treatment success for lumbar BMD. With the LSC, some treatment success was observed in the early phase of treatment, and it increased with treatment duration.

CONCLUSIONS

It appears that the LSC could be used as a surrogate efficacy indicator at an earlier stage of treatment, and the absolute criterion of -2.5SD was confirmed as a useful marker of long-term treatment success.