A new possible marker: can pennation angle defined by ultrasound predict the frailty?

Background: Frailty indicates older people who are vulnerable to stressors. The relation between ultrasonographic parameters of muscle and frailty among older people has yet to be investigated.

Aims: The aim of the study is to investigate the relationship between frailty and the ultrasonographic measurements of the rectus femoris muscle (RFM).

Methods: This cross-sectional study included 301 participants who were ≥65 years. The FRAIL questionnaire assessed frailty. The thickness, cross-sectional area (CSA), fascicle length, pennation angle (PA), stiffness, and echogenicity of RFM were assessed by ultrasound. The accuracy of parameters in predicting the frailty was evaluated by ROC analysis.

Results: Of all 301 participants, 24.6% were frail. Pre-frail and frail participants had significantly lower thickness (p = 0.002), CSA (p = 0.009), and fascicle length (p = 0.043) of RFM compared to robust. PA was significantly lowest in frails (p < 0.001). The multivariate logistic regression analysis showed that PA values lower than 10.65 degrees were an independent predictor of frailty (OR = 0.83, 95% Cl: 0.70-0.97, p = 0.019). Results of ROC analysis demonstrated a satisfactory result between the PA and frailty (AUC = 0.692, p < 0.001).

Discussion: Thickness, CSA, and PA of RFM were found to be lower in frail subjects, which may indicate the changes in muscle structure in frailty. Among all parameters, lower PA values were independent predictors of frailty. These findings may indicate a novel ultrasound-based method in frailty, that is more objective and unrelated to the cross-sectional evaluation.

Conclusions: Ultrasonographic measurements of RFM, especially the lower PA may predict frailty in older people. As an objective and quantitative method, PA may be used to define frailty with acceptable sensitivity.