Reliability, agreement, and validity of digital weighing scale with MatScan in limb load measurement

INTRODUCTION Standing is an essential fundamental position to carry out functional activities of daily living [1]. The ability to maintain the body in equilibrium during standing is influenced by factors such as visual input and lower-limb weight distribution [2-4]. The presence of visual input improves postural control in standing [1]. On the other hand, eyes closed (EC) during standing produces a greater body sway, resulting in postural instability leading to asymmetrical limb loading [3,5]. Limb loading distribution is said to be symmetrical when both lower limbs load equally. Functional activities such as standing and walking are said to be energy efficient when both lower limbs behave symmetrical in loading [1,7]. However, unequal limb loading in the long term may lead to complications such as osteopenia, cartilage destruction, and joint degeneration [6-7]. Hence, in clinical practice, quantification of weight distribution on lower limbs is crucial in rehabilitation of patients with lower-limb pathologies such as lower-limb fractures, amputations, joint replacements, and stroke [6]. Limb loading can be quantified by digital weighing scales (DWSs), biofeedback systems, MatScan (Tekscan Inc; South Boston, Massachusetts), ambulatory devices, and force platforms [6]. Biofeedback systems, MatScan, ambulatory devices, and force platforms provide more reliable and accurate data than DWSs [6]. However, the aforementioned devices are more expensive, require trained personnel, and are not available in common clinical practice [6,8]. Hence, they are seldom in use to measure limb load asymmetry (LLA). Conversely, using two DWSs is the conventional method used by practitioners to measure asymmetry of weight bearing on lower limbs [9]. DWSs give an instant quantitative reading of weight in kilograms [10] with a precision up to two decimal points [6,11]. DWSs are portable, cheap, less time consuming, easily accessible, light, and small [6]. DWSs do not require additional training for clinicians and patients and have good accuracy in static weight bearing measurements [6]. Despite the usefulness of DWSs, their reliability and validity have not been tested [12]. Reliability is defined as consistency of output yielded on repetitive measurements using a DWS with clinically acceptable measurement [13]. Agreement concerns the absolute measurement error, which addresses how close the measurements obtained from equipments are to one another [14]. It refers to the extent to which measurements between DWS and MatScan are identical. Validity concerns the extent to which equipment measures what it is intended to measure [14]. It refers to the degree to which limb loading measurement of a DWS correlates with the standard measurement tool. In clinical practice, force platform [6] and MatScan [15] are considered the standard tools for limb load assessment. Hence, there would be an interest in knowing whether DWSs are in agreement or could be used interchangeably with the aforementioned tools to measure LLA [16]. The aim of this study was to investigate the reliability, agreement, and validity of DWSs with MatScan to measure LLA among the nondisabled population during eyes open (EO) and EC conditions. DWSs are a commonly available tool, portable, cost-effective, and need less skill to maneuver; hence, if they are proven to be valid and reliable they could provide practitioners an objective limb load measurement suitable for everyday clinical practice. METHODS This cross-sectional study was conducted with 33 nondisabled adults (15 male, 18 female) recruited through convenience sampling from the physiotherapy department at a public university teaching hospital. Participants with impairments to the lower limb, history of lower-limb surgery, inadequate visual and hearing ability, neuromusculoskeletal impairment, and limb-length discrepancy more than 1 cm were excluded. Measurements with a DWS were administered in the Department of Physiotherapy, followed by MatScan measurements at the Department of Orthopedics and Traumatology. …