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Technical Brief

A Sensor System to Measure Force Applications of a Brace for Pectus carinatum

[+] Author and Article Information
Tomasz Bugajski

Biomedical Engineering Graduate Program,
University of Calgary,
2500 University Drive N.W.,
Calgary, AB T2N 1N4, Canada
e-mail: tbugajsk@ucalgary.ca

Douglas Kondro

Biomedical Engineering Graduate Program,
University of Calgary,
2500 University Drive N.W.,
Calgary, AB T2N 1N4, Canada
e-mail: dakondro@ucalgary.ca

Kartikeya Murari

Biomedical Engineering Graduate Program,
Department of Electrical and Computer Engineering,
University of Calgary,
2500 University Drive N.W.,
Calgary, AB T2N 1N4, Canada
e-mail: kmurari@ucalgary.ca

Janet Ronsky

Biomedical Engineering Graduate Program,
Department of Mechanical and
Manufacturing Engineering,
Faculty of Kinesiology,
University of Calgary,
2500 University Drive N.W.,
Calgary, AB T2N 1N4, Canada
e-mail: jlronsky@ucalgary.ca

1Corresponding author.

Manuscript received January 9, 2018; final manuscript received August 6, 2018; published online November 5, 2018. Assoc. Editor: Elizabeth Hsiao-Wecksler.

J. Med. Devices 13(1), 014501 (Nov 05, 2018) (6 pages) Paper No: MED-18-1005; doi: 10.1115/1.4041190 History: Received January 09, 2018; Revised August 06, 2018

Pectus carinatum (PC) presents itself as a protrusion on the chest wall of adolescent individuals. Current treatment for PC is performed with a Pectus carinatum orthosis (PCO) that applies a compressive force to the protrusion. While this treatment is accepted, the magnitude of compressive forces applied remains unknown leading to excessive or deficient compression. Although the need for this quantitative data is recognized, no studies reporting the data or methods are available. The purpose of this study was to design an accurate force measurement system (FMS) that could be incorporated into a PCO with minimal bulk. Components of the FMS were three-dimensional (3D)-printed and incorporated into an existing PCO design. The FMS was calibrated using a custom indenter that applied forces to the FMS in a controlled manner. Evaluation of the FMS on five human participants was also performed. A reliability measure of the FMS was calculated for analysis. The FMS was implemented into the PCO and able to withstand the applied forces. The calibration revealed an increase in load cell error with increased magnitude of applied force (mean error [SD] = 5.59 N [6.48 N]). Participants recruited to evaluate the FMS demonstrated reliable forces (R = 96%) with smaller standard deviations than those during the calibration. The FMS was shown capable of measuring PCO forces but requires further testing and improvement. This system is the foundational component in a wireless, minimalistic sensor system to provide real time force feedback to both the clinician and patient.

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References

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Figures

Grahic Jump Location
Fig. 1

The protrusion (boxed in black) on the chest wall associated with PC

Grahic Jump Location
Fig. 2

The PC orthosis developed by Braceworks (Calgary, AB) and its major components: (a) aluminum bar, (b) pad with a black carbon shell, (c) straps (right arrow—back strap, left arrow—shoulder strap), and (d) Boa closures

Grahic Jump Location
Fig. 3

(a) The backing surface attached to the pad of the PCO, allowing a flat surface for the incorporation of the load cells on the sites of the four sockets and (b) the replica surface containing the load cells attached with epoxy

Grahic Jump Location
Fig. 4

The full assembly of FMS. The load cells on the replica surface inserted into the sockets contained on the backing surface. The backing surface was glued onto the pad of the PCO.

Grahic Jump Location
Fig. 5

Schematic of the pad and the nine locations (points) of force application when calibrating the FMS. Each colored circle represents a load cell.

Grahic Jump Location
Fig. 6

Calibration curve (mean [SD]) of the FMS. The light gray line represents the original data before utilizing the least square method. The dark gray line represents the data after performing the least squares method. The black line (poly) is the fitted line on the least square data, used for obtaining the equation that converts voltage to pound force.

Grahic Jump Location
Fig. 7

The new calibration curve (mean [SD]) of the FMS only containing location 1. The light gray line represents the original data before utilizing the least square method. The dark gray line represents the data after performing the least squares method. The black line (poly) is the fitted line on the least square data, used for obtaining the equation that converts voltage to pound force.

Grahic Jump Location
Fig. 8

Mean (SD) of the CF and PF for each participant

Grahic Jump Location
Fig. 9

A schematic of the backing (a) with flexural bending in the transverse plane (b) and sagittal plane (c). A schematic of the replica (d) with flexural bending in the transverse plane (e) and sagittal plane (f). P represents the load applied to the FMS, and l is the length of the assumed beam.

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