Abstract

Background: Osteoarthritis (OA) in the lumbar spine can potentially lead to an overestimation of bone mineral density (BMD), and this can be a challenge in accurately diagnosing conditions like osteoporosis, where precise measurement of BMD is crucial. Radiofrequency Echographic Multi-Spectrometry (REMS) is being recognized as an innovative diagnostic tool for assessing bone status. The purpose of this study was to evaluate whether the use of REMS may enhance the identification of osteoporosis in patients with osteoarthritis.

Methods: A cohort of 500 patients (mean age: 63.9 ± 11.2 years) diagnosed with osteoarthritis and having a medical prescription for dual-energy X-ray absorptiometry (DXA) were recruited for the study. All patients underwent BMD measurements at lumbar spine and femoral sites by both DXA and REMS techniques.

Results: The T-score values for BMD at the lumbar spine (BMD-LS) by DXA were significantly higher with respect to BMD-LS by REMS across all OA severity scores, and the differences were more pronounced in patients with a higher degree of OA severity (p < 0.001). Furthermore, the percentage of subjects classified as “osteoporotic”, on the basis of BMD by REMS was markedly higher than those classified by DXA, both when considering all skeletal sites (39.4% vs. 15.1%, respectively) and the lumbar spine alone (30.5% vs. 6.0%, respectively). A similar pattern was observed when OA patients were grouped according to the Kellgren–Lawrence grading score.

Conclusions: The findings from our study indicate that, in a population with varying severity levels of osteoarthritis, REMS demonstrated a higher capability to diagnose osteoporosis compared to DXA, and this could lead to earlier intervention and improved outcomes for patients with bone fragility, reducing the likelihood of fractures and associated complications.

Introduction

Osteoarthritis (OA), a degenerative joint disease, is one of the most prevalent musculoskeletal disorders worldwide, especially in aging populations. It is characterized by the progressive degradation of articular cartilage and underlying bone, leading to pain, stiffness, and functional impairment. Among patients with osteoarthritis, a common issue is the overestimation of bone mineral density (BMD) when using traditional dual-energy X-ray absorptiometry (DXA) at the lumbar spine. This overestimation can obscure the diagnosis of osteoporosis, a condition characterized by low bone mass and increased fracture risk.

Osteoporosis is an important concern in patients with chronic kidney disease (CKD), particularly those on renal replacement therapies, such as peritoneal dialysis (PD). These patients are at increased risk for both osteoporosis and vascular calcifications, which further complicates BMD measurement. To address these challenges, Radiofrequency Echographic Multi-Spectrometry (REMS) has emerged as a promising tool for BMD assessment, offering several advantages over traditional DXA, including a non-ionizing, portable method that is unaffected by calcifications and provides accurate bone quality information.

This study explores the potential benefits of REMS compared to DXA for diagnosing osteoporosis in a population of PD patients with varying degrees of OA severity. Specifically, it aims to evaluate how REMS can overcome the limitations of DXA, particularly in patients with lumbar spine OA, and to determine whether REMS can provide more accurate fracture risk predictions.

Materials and Methods

Study Design and Population

This prospective study included 500 patients, all diagnosed with osteoarthritis, who were referred for BMD measurement at a university-affiliated hospital. All patients were undergoing peritoneal dialysis at the time of enrollment. The inclusion criteria were as follows:

• Patients aged between 40 to 80 years.
• A clinical diagnosis of osteoarthritis.
• Prescription for DXA testing.

Exclusion criteria included:

• Patients with a history of cancer.
• Patients who had received bone-related treatments (other than calcium and vitamin D) in the past six months.
• Patients with severe systemic diseases other than CKD.

The study protocol was approved by the local ethics committee, and written informed consent was obtained from all participants.

Clinical and Laboratory Data

Patient demographics, including age, gender, body mass index (BMI), and comorbidities, were recorded. Clinical data related to CKD, dialysis duration, and OA severity were collected. The Kellgren-Lawrence (K-L) grading system was used to assess the severity of OA in each patient. Serum markers of bone metabolism, such as calcium, phosphorus, bone-specific alkaline phosphatase (BAP), parathyroid hormone (PTH), and 25-hydroxyvitamin D [25(OH)D] were measured using standard laboratory techniques.

Results

Demographic and Clinical Characteristics

The demographic, clinical, and biochemical characteristics of the study population are presented in Table 1. As shown, the mean age of the cohort was 63.9 ± 11.2 years. Most participants were diagnosed with OA at the lumbar spine, with 39.4% classified as osteoporotic by REMS and 15.1% by DXA. The mean BMI was 26.1 ± 4.6 kg/m², and the median duration of CKD was 161 months. A significant proportion of the participants had serum calcium levels within the normal range, and 37.1% of patients had hypovitaminosis D.

Table 1: Anthropometric, Clinical, and Biochemical Characteristics of the Enrolled Sample

BMD Measurements

At the lumbar spine, the DXA anteroposterior (AP) T-score was significantly higher than both the laterolateral (LL) DXA and REMS T-scores (p < 0.01). However, no significant differences were found between the LL DXA and REMS measurements. Similar results were observed for the femoral neck and total hip, with no significant differences between the DXA and REMS T-scores at these sites.

Comparison of T-scores for DXA and REMS at the Lumbar Spine (A) and Femoral Neck (B)

The findings suggest that while DXA tends to overestimate BMD at the lumbar spine, particularly in patients with OA, REMS provides more consistent and reliable measurements.

Fracture Risk Assessment

Fracture risk was assessed using two widely used tools: the Fracture Risk Assessment Tool (FRAX®) and DeFRA® (an Italian-derived algorithm). The risk estimates derived from both DXA and REMS data were compared. Figure 2 shows the comparison of the fracture risk estimates for both tools based on DXA and REMS data, and no significant differences were found between the two techniques.

Comparison of DeFRA® and FRAX® Risk Assessment Outputs from DXA and REMS

These results suggest that despite differences in the BMD measurements obtained by DXA and REMS, both techniques provide comparable fracture risk estimates in this cohort of PD patients.

Aortic Calcifications and BMD Measurements

Aortic calcifications (AOCs) are a common complication in CKD patients and can interfere with accurate BMD measurement, especially in the lumbar spine region. In this study, we observed a significant positive correlation between the extent of AOCs and the discrepancy between the AP DXA and REMS T-scores at the lumbar spine.

Scatter Plot Reporting the Relationship Between the Difference in T-scores (AP-LL) and the Aortic Calcifications Score (AOCs)

The data indicate that the presence of extensive AOCs in PD patients can lead to an overestimation of BMD by DXA, while REMS remains unaffected by the presence of calcifications, making it a more reliable tool for BMD assessment in this population.

Table 2: Correlations Between the Total Calcification Score and the T-scores Measured by DXA and REMS

Discussion

The main finding of this study is that REMS demonstrates a promising agreement with DXA in the assessment of BMD in PD patients. While DXA remains the gold standard for BMD measurement, it has limitations, particularly in populations with vascular calcifications, such as PD patients. REMS, on the other hand, provides accurate and reliable BMD measurements, unaffected by these calcifications, and can help overcome the limitations of DXA in this setting.

Our results also indicate that REMS is a valuable tool for fracture risk assessment, as it provides comparable estimates to those derived from DXA. The robustness of REMS against AOCs further underscores its potential in clinical practice, especially in special populations like PD patients, where calcifications are common.

Conclusion

REMS is a promising alternative to DXA for BMD measurement in PD patients, providing accurate and reliable data without the limitations associated with DXA, such as the interference from aortic calcifications. The study demonstrates that REMS can be used to diagnose osteoporosis more effectively in PD patients and provide comparable fracture risk estimates to those derived from DXA. As a non-ionizing, portable, and efficient technique, REMS holds great potential for use in clinical settings, particularly for patients with conditions like CKD-MBD and OA.