Feasibility of the use of a novel soft tissue stiffness meter

Abstract

Simple but objective measurement of soft tissue consistency would be advantageous in the assessment of many neurological, lymphostatic and venous disorders. The aim of the present study was to evaluate the feasibility of using a novel hand-held computerized soft tissue stiffness meter (STSM). The STSM describes the soft tissue stiffness (STS) in the form of the instantaneous force (N) by which the tissue resists the constant deformation produced by a cylindrical intender. Firstly, the STSM was used to test elastomer samples with known mechanical properties. In the in vivo assessment, 12 healthy, nondisabled adults (age range, 24–57 years) and 16 subjects with chronic myofascial neck pain syndrome (age range, 27–55 years) were studied. To study the reproducibility (coefficient of variation (CV(%))) of the method, the measurement sites were either marked with a marker pen (marked points) or localized anatomically (unmarked points). Measurements were made from the dorsal forearm (Arm), trapezius (Tra), levator scapulae (Lev), infraspinatus (Inf) and deltoideus (Del) muscle areas. STS in the forearm was studied during different types of short-term relative isometric loading of the muscle as well as during venous occlusion. STS values of the myofascial trigger points in the Lev muscles were evaluated bilaterally. A linear, positive relationship was found between the indenter force (N) and the dynamic compressive modulus (MPa) of elastomer stiffness (r2 = 0.90, n = 9). Intra- and interrater CVs of marked and unmarked sites varied between 4.31% and 12.06%. STS increased linearly along the relative muscle load (r2 = 0.96) and nonlinearly during the venous occlusion (r2 = 0.97). Statistically significant regional variation of STS was found between the different measurement sites (p < 0.05). In conclusion, STSM can evaluate tissue stiffness quantitatively and yield reproducible data.