Lumbar myofascial physical properties in healthy adults: myotonometry vs. shear wave elastography measurements.

Objective: The human resting myofascial tone maintains the body tone in a neutral posture, the assessment of this and other muscle physical properties (MPP) is relevant, since, it is altered in many pathological states.

Patients and methods: Seventeen healthy subjects (8 males), between 18-50 years old, were assessed. The MPP of lower lumbar muscles was evaluated on right and left sides during prone resting position using two devices; myotonometry (stiffness, elasticity and tone) and ultrasound-based shear-wave elastography (SWE) (shear modulus). MTM measurements were performed at two anatomic points (ANp), selected by an experienced reader and at an adjacent ultra-sound determined point (USp). Myotonometry measurements of the erector spinae and SWE measurements of multifidus muscles at the L3-4 level were compared between genders and sides. The intra-reader reliability (IRR) for each device and correlations between techniques were analysed. MTM measurements performed at ANp and USp were compared. The intraclass correlation coefficient (ICC) was assessed for both devices. Correlations between stiffness (myotonometry) and shear modulus (SWE) at the respective muscle depths were assessed with Spearman correlation.

Results: Males had greater stiffness and tone than females, particularly on the dominant side. MPP assessed by myotonometry were not different between ANp and USp. Good/Excellent IRR was documented for measurements by MTM (ICC≥0.90) and SWE (ICC≥0.85). No correlation in myotonometry stiffness and SWE shear modulus was found. For myotonometry assessments, the addition of ultrasonography was not different from anatomic localizations. No correlation of measurements was found between devices assessing respective L3-4 level muscles.

Conclusions: Gender and side differences must be considered when assessing MPP in axial muscles. For MTM assessments, the addition of ultrasonography was not different to anatomic references. No correlation was found between devices.