Diagnostic Performance of Musculoskeletal Ultrasound for Detecting Low Appendicular Lean Mass in Adults at Risk of Osteosarcopenia

Abstract

Background/Purpose

Osteosarcopenia is a musculoskeletal syndrome associated with frailty, disability, and fracture risk. Dual-energy X-ray absorptiometry (DXA) is the reference method for body composition assessment; however, access to DXA-based muscle evaluation may be limited. Musculoskeletal ultrasound (US) is an accessible, portable, and non-ionizing imaging tool that may provide an objective assessment of muscle mass in older adults at risk of osteosarcopenia. This study aimed to evaluate the diagnostic performance of musculoskeletal ultrasound for identifying low appendicular lean mass compared with DXA in adults at risk of osteosarcopenia.

Methods

We conducted a cross-sectional analytical study in adults at risk of osteosarcopenia. Clinical assessment included SARC-F, handgrip strength, sit-to-stand test, gait speed, bone densitometry, and DXA-derived body composition. Sarcopenia was defined according to European Working Group on Sarcopenia in Older People (EWGSOP2) criteria. Musculoskeletal ultrasound was performed on the dominant side at four muscle sites: forearm flexors/brachioradialis, biceps, quadriceps, and tibialis anterior. Ultrasound-derived appendicular muscle mass was estimated using the Abe 2018 equation. Mann-Whitney U test, chi-square test, Spearman correlation, and ROC analysis were performed.

Results

Eighty-eight patients were included, with a median age of 67 years (IQR 63–70), and 84.8% were women. Twenty-three patients met EWGSOP2 criteria for sarcopenia; among them, 60.9% had osteopenia and 39.1% had osteoporosis, fulfilling criteria for osteosarcopenia. SARC-F, sit-to-stand test, and gait speed did not differ significantly between groups. On ultrasound assessment, patients with sarcopenia had lower forearm flexor/brachioradialis thickness [2.56 cm (IQR 2.25–2.95) vs. 2.85 cm (IQR 2.51–3.18), p=0.006] and tibialis anterior thickness [3.79 cm (IQR 3.55–4.13) vs. 4.14 cm (IQR 3.87–4.44), p=0.001]. The ultrasound-derived appendicular muscle mass index estimated using the Abe 2018 equation was lower in patients with sarcopenia [5.49 kg/m² (IQR 4.95–6.43)] than in those without sarcopenia [6.12 kg/m² (IQR 5.55–6.59), p=0.002]. The ultrasound-derived Abe 2018 index showed a strong positive correlation with DXA-derived appendicular lean mass index (rho=0.848, p< 0.001). In ROC analysis, the dichotomized ultrasound-derived equation showed an AUC of 0.883 (95% CI 0.796–0.970, p< 0.001) for identifying DXA-defined low appendicular lean mass.

Conclusion

US-derived appendicular muscle mass showed strong correlation with DXA and good diagnostic performance for detecting low appendicular lean mass in adults at risk of osteosarcopenia. Forearm flexor/brachioradialis and tibialis anterior thickness were the most discriminative US sites. These findings support US as a feasible tool when DXA-based body composition evaluation is not widely available.