Force Sensing for an Instrument-Assisted Soft Tissue Manipulation Device

Abstract

Instrument-assisted soft tissue manipulation (IASTM) is a form of mechanotherapy, e.g., massage, that uses rigid devices which may be machined or cast. The delivered force, which is a critical parameter during IASTM, is not measured and not standardized in current clinical IASTM practice. In addition to the force, the angle of treatment and stroke frequency play an important role during IASTM. For accurate IASTM treatment, there is a strong need to scientifically characterize the IASTM delivered force, angle of treatment, and stroke frequency. This paper presents a novel, mechatronic design of an IASTM device that can measure the localized pressure on the soft tissue in a clinical treatment. The proposed design uses a three-dimensional (3D) load cell, which can measure all three-dimensional force components simultaneously. The device design was implemented using an IMUduino microcontroller board which provides tool orientation angles. These orientation angles were used for coordinate transformation of the measured forces to the tool–skin interface. Additionally, the measured force value was used to compute the stroke frequency. This mechatronic IASTM tool was validated for force measurements in the direction of tool longitudinal axis using an electronic plate scale that provided the baseline force values to compare with the applied force values measured by the tool. The load cell measurements and the scale readings were found to agree within the expected degree of accuracy.

A Hand-Held Device to Apply Instrument-Assisted Soft Tissue Mobilization at Targeted Compression Forces and Stroke Frequencies

“…Second, the device should provide the operator feedback to accurately apply compression at targeted force magnitudes between 0.5 and 100 N and stroke frequencies between 0.25 and 1 Hz. These force magnitudes replicate a range of parameters used for small animal studies and clinical research [8][9][10]13,14,16,19].…”

“…However, none of these methods were validated to apply a targeted force or stroke frequency. This study has provided validation that a simple device, using a uniaxial force sensor, allows users to achieve excellent accuracy within the range of forces and stroke frequencies used for small animal research and in clinical practice [8][9][10]13,14,16,19]. To assist the adoption of this technique by other research groups, the LABVIEW data acquisition software that provides visual and audio feedback to operators, and the MATLAB software that automates data analysis, is freely available to download in the website link.…”

“…3(a)). To accurately measure force at any shaft angle, the device would require a tri-axial force sensor to capture both axial and transverse force components [13,16]. However, this would increase device complexity and cost.…”

“…The second test determined the device's accuracy and error in applying forces and stroke frequencies over a range of targeted values. This test was performed by having three individuals, with no clinical experience, use the device to dynamically stroke a rigid foam block at eight different targeted forces relevant to small animal research (0.1, 0.2, 0.3, 0.4, 0.5, 1, 3, 5 N) [8][9][10], and load a silicone pad at eight different targeted forces relevant to human clinical treatments (10, 25, 50, 75, 100, 125, 150, 175 N) [13,14,16,19]. Targeted loads were applied above and below the normal range used during IASTM treatments (0.5-100 N) to determine the loading limits of the device.…”

“…Current techniques to apply IASTM in a research setting include instrumented hand-held devices and robotic manipulators. Hand-held devices are practical but have not yet been validated to apply targeted forces and frequencies [8][9][10][12][13][14][15][16]. Robotic manipulators have been used to control the compressive force and stroke frequency during soft tissue mobilization of muscle along a single axis [17,18].…”