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) and osteoporosis (OP) are two prevalent musculoskeletal conditions that primarily affect older adults. OA, a degenerative joint disease, commonly involves the lumbar spine, leading to conditions such as osteophyte formation, joint space narrowing, and vertebral sclerosis. This can lead to an overestimation of bone mineral density (BMD) when using traditional techniques like Dual-Energy X-ray Absorptiometry (DXA). In contrast, osteoporosis is a bone disease characterized by a decrease in BMD, resulting in an increased risk of fractures. The accurate assessment of BMD is crucial for diagnosing osteoporosis and initiating early interventions to prevent fractures.

Despite its established role in clinical practice, DXA has limitations in patients with osteoarthritis. The presence of OA-related changes in the lumbar spine, such as osteophytes and vertebral sclerosis, can interfere with the accurate measurement of BMD by DXA, leading to falsely elevated results. This overestimation can mislead clinicians, delaying the diagnosis and treatment of osteoporosis. Consequently, there is a need for a more reliable diagnostic method to assess BMD in patients with OA, especially in the lumbar spine.

Radiofrequency Echographic Multi-Spectrometry (REMS) is an innovative, non-ionizing diagnostic tool that uses ultrasound to assess bone density. Unlike DXA, which relies on X-rays, REMS analyzes unfiltered ultrasound signals, enabling it to overcome the limitations associated with OA-related artifacts in the lumbar spine. REMS has the potential to provide more accurate and reliable BMD measurements in patients with OA, enhancing the diagnosis of osteoporosis.

This study aims to compare the efficacy of REMS and DXA in diagnosing osteoporosis in patients with OA, focusing on the lumbar spine and femoral neck. We hypothesize that REMS will outperform DXA in identifying osteoporosis in OA patients, providing a more accurate assessment of bone health.

Methods

Study Design and Population

This prospective cohort study included 500 patients diagnosed with osteoarthritis, who were referred for BMD testing. All participants were aged between 45 and 80 years, with a mean age of 63.9 ± 11.2 years. The inclusion criteria required patients to have a medical prescription for DXA. Patients with significant medical conditions affecting bone metabolism, such as cancer, hyperparathyroidism, or ongoing treatment with anti-osteoporosis drugs, were excluded. Additionally, individuals with severely impaired mobility that prevented them from undergoing the BMD assessment were excluded.

The patients were categorized according to the severity of OA using the Kellgren-Lawrence (K-L) grading system, which classifies OA severity from 0 (no OA) to 4 (severe OA). The severity of OA in the lumbar spine was determined by radiological examination.

BMD Measurement

• DXA: BMD measurements were performed at the lumbar spine (L1-L4) and femoral neck using a Hologic Discovery W DXA scanner. DXA is considered the gold standard for BMD measurement and provides T-scores that classify bone density as normal, osteopenic, or osteoporotic based on the World Health Organization’s (WHO) criteria.
• REMS: BMD was also measured using the REMS technique, performed using an EchoStation device. This technique relies on high-resolution ultrasound to assess the bone’s microarchitecture. REMS is a non-ionizing, radiation-free method that offers several advantages, including the ability to assess bone quality and eliminate artifacts caused by OA-related changes in the lumbar spine.

Both DXA and REMS were performed on the same day to ensure accurate comparison of the results.

Flow chart showing the distribution of participants to the DEMETER Study.

Results

Demographic and Clinical Characteristics

The demographic and clinical characteristics of the study population are shown in Table 1. As expected, subjects with a more severe OA score (K-L score = 3 and K-L score = 4) were older and presented BMD values at all skeletal sites higher with respect to those with mild osteoarthritis (K-L score = 2) or absence/doubtful (K-L = 0/1). This suggests that the degree of OA severity is correlated with increasing BMD values when measured using DXA. However, this trend was not observed with REMS, where the BMD values showed an opposite trend compared to those obtained from the DXA technique.

Table 1: Anthropometric, Clinical, and Densitometric Characteristics of the Study Population Grouped According to the Kellgren–Lawrence Score

BMI-Adjusted Partial Correlation Between BMD-LS T-Scores by DXA and REMS

Figure 2 illustrates the BMI-adjusted partial correlation between BMD-LS T-scores obtained via DXA and REMS techniques in relation to osteoarthritis scores. There is a noticeable high correlation between the T-score values derived from both techniques at the lumbar spine across different osteoarthritis scores. The correlation coefficients (r) for the different OA severity groups were:

• K-L score 0/1: r = 0.98, p < 0.0001
• K-L score 2: r = 0.85, p < 0.001
• K-L score 3: r = 0.98, p < 0.0001
• K-L score 4: r = 0.45, p < 0.01

As expected, less severe OA scores had better significance, indicating stronger correlation between the BMD values measured by both DXA and REMS in these patients.

BMI-adjusted partial correlation between BMD-LS T-scores by DXA technique and BMD-LS T-score by REMS technique according to osteoarthritis score (K-L score 0/1 = (A), K-L score 2 = (B), K-L score 3 = (C), and K-L score 4 = (D)).

Comparison of T-Score BMD-LS by DXA and REMS Techniques

shows the values of T-score BMD at the lumbar spine, measured by DXA and REMS techniques, according to the OA score. The values of BMD-LS by DXA were significantly higher compared to BMD-LS by REMS at all OA scores. In particular, the difference became more significant as the degree of severity of OA increased (p < 0.001).

Values of BMD expressed as a T-score at the lumbar spine by DXA and REMS techniques grouped by OA score.

Osteoporotic, Osteopenic, and Normal Classifications by DXA and REMS

illustrates osteoarthritis patients categorized as “osteoporotic,” “osteopenic,” or “normal” based on BMD T-score values obtained through both DXA and REMS techniques, either at the lumbar spine alone (Figure 4A) or across all skeletal sites (Figure 4B). Notably, the REMS technique allows a larger percentage of OA patients to be classified as osteoporotic or osteopenic at the lumbar spine compared to DXA (30.5% and 52.0% vs. 6.0% and 34.5%, respectively). Conversely, the percentage of subjects classified as normal by DXA was higher than that by REMS (59.5% vs. 17.5%, respectively).

Similarly, when considering all skeletal sites, the percentage of patients with OA classified as osteoporotic was significantly higher with REMS compared to DXA (39.4% vs. 15.1%, respectively). On the contrary, the percentage of subjects with OA classified as osteopenic or normal at all skeletal sites by DXA was similar and higher than that by REMS (51.1% and 30.4% vs. 54.5% and 9.5%, respectively).

The proportion of osteoarthritis (OA) patients categorized as “osteoporotic,” “osteopenic,” or “normal” based on BMD T-score values acquired through DXA and REMS techniques specifically at the lumbar spine (A) or across all skeletal sites (B).

Classification of Osteoporotic, Osteopenic, and Normal Patients by K-L Score

shows the percentage of patients classified as having osteoporosis, osteopenia, or normal on the basis of BMD at the lumbar spine (Figure 5A) or at all skeletal sites (Figure 5B) according to the K-L grading score. A similar trend was observed when the patients were grouped according to the severity of the OA grade. Specifically, as the severity of OA increased, the percentage of patients classified as osteoporotic by REMS also increased, while DXA classification remained lower.

Percentage of patients classified as “osteoporotic,” “osteopenic,” or “normal” at the lumbar spine alone (A) or at all skeletal sites (B) according to the K-L score.

Discussion

The key finding from this study is the superior ability of REMS in diagnosing osteoporosis compared to DXA, especially in patients with osteoarthritis. The limitations of DXA in OA patients are well-documented, as OA-related changes in the lumbar spine often result in overestimated BMD. REMS, by contrast, is not affected by these artifacts and provides a more accurate measure of bone density, especially in the lumbar spine, where OA-related changes are most pronounced.

The study also shows that REMS is able to detect osteoporosis in a significantly higher percentage of OA patients compared to DXA. This enhanced diagnostic capability could lead to earlier intervention and improved outcomes for patients at risk of fragility fractures. Additionally, the non-ionizing nature of REMS makes it a safer alternative for frequent monitoring of bone health, especially in populations like pregnant women, children, and those requiring repeated imaging.

Conclusion

In conclusion, REMS is a promising technology for evaluating BMD in patients with osteoarthritis. It provides a more accurate and reliable diagnosis of osteoporosis compared to DXA, particularly in the lumbar spine. Given its non-ionizing nature and ability to eliminate OA-related artifacts, REMS could become a valuable tool for clinicians, offering a safer and more effective alternative for assessing bone health in OA patients. Further studies are needed to validate these findings and explore the potential of REMS in other clinical populations.

Future Directions

The future of BMD assessment lies in integrating new technologies like REMS with traditional methods to enhance diagnostic accuracy. Longitudinal studies will be crucial to assess the predictive value of REMS in identifying patients at high risk for fractures. Furthermore, combining REMS with other biomarkers of bone metabolism could offer a more comprehensive approach to diagnosing and managing osteoporosis in OA patients.