Minimal detectable change in inertial measurement unit-based trunk acceleration indices during gait in inpatients with subacute stroke

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Minimal detectable change in inertial measurement unit-based trunk acceleration indices during gait in inpatients with subacute stroke

• Tatsuya Igarashi,
• Yuta Tani,
• Ren Takeda &
• Tomoyuki Asakura 

Scientific Reports volume 13, Article number: 19262 (2023) Cite this article

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Abstract

Gait analysis using inertial measurement units (IMU) provides a multifaceted assessment of gait characteristics, but minimal detectable changes (MDC), the true change beyond measurement error, during gait in patients hospitalized with subacute stroke has not been clarified. This study aimed to determine the MDC in IMU-based trunk acceleration indices during gait in patients hospitalized with subacute stroke. Nineteen patients with subacute stroke (mean ± SD, 75.4 ± 10.9 years; 13 males) who could understand instructions, had a pre-morbid modified Rankin Scale < 3 and could walk straight for 16 m under supervision were included. As trunk acceleration indices, Stride regularity, harmonic ratio (HR), and normalized root mean square (RMS) during gait were calculated on three axes: mediolateral (ML), vertical (VT), and anterior–posterior (AP). MDC was calculated from two measurements taken on the same day according to the following formula: MDC = standard error of measurement × 1.96 × 2. The MDCs for each trunk acceleration index were, in order of ML, VT, and AP: 0.175, 0.179, and 0.149 for stride regularity; 0.666, 0.741, and 0.864 for HR; 4.511, 2.288, and 2.680 for normalized RMS. This finding helps determine the effectiveness of rehabilitation interventions in the gait assessment of patients with stroke.

Introduction

One of the major disabilities after a stroke is a decreased ability to walk. It was reported that 82% of patients had not fully recovered the ability to walk at least 3 months after stroke¹. Walking in patients with stroke is a critical ability related to the individual's quality of life^2,3 and activities of daily living⁴. The temporal regularity of the gait cycle and the smoothness and efficiency of the center of gravity shifts are often impaired in walking after stroke, and these are closely related to balance function to prevent falls⁵. Decreased ability to walk after stroke results from the combined effects of motor paralysis, sensory dysfunction, and loss of balance control systems. Therefore, much of the rehabilitation of patients with stroke focuses on improving their ability to walk^6,7.

Assessment of walking ability in the rehabilitation setting often involves visual observations and question-based clinical rating scales that rely on the expertise of the examiner. However, it has been noted that visual observational assessment of gait may not be sufficiently reliable⁸. Therefore, to accurately assess the gait of patients with stroke, it is advisable to use methods that can measure temporal and spatial parameters with high sensitivity, such as motion capture technology and inertial measurement devices. Gait analysis using an inertial measurement unit (IMU) can quantify gait characteristics such as smoothness of gait and regularity of steps derived from rhythmic motion during walking, which is difficult to evaluate with conventional gait analyzers and can evaluate gait characteristics from multiple perspectives. IMU is a highly feasible measurement method in clinical practice because of its portability and short measurement time⁹, reducing the patient’s burden. Furthermore, indicators obtained by walking with the IMU attached to the trunk (from now on collectively referred to as trunk acceleration indices) have been reported as associated with balance ability⁵ and trunk function¹⁰ after stroke, indicating their usefulness in gait assessment.

For the clinician to understand the clinical changes in a patient, the results measured by a tool must recognize minimal changes that are considered to be beyond simple measurement errors¹¹. This minimum change is referred to as the minimal detectable change (MDC)¹² or the smallest detectable change (SDC)^13,14. Identifying the measures’ MDCs allows discrimination between measurement error and true change, which is a valuable insight in determining the effectiveness of rehabilitation interventions. MDC of trunk acceleration indices has been reported in healthy people¹⁵ and patients with chronic stroke^16,17. However, the MDC of trunk acceleration indices during walking in inpatients with subacute stroke is yet to be clarified. Since the degree of ambulation due to recovery or compensation after stroke depends on the disease stage, clarifying the MDC of gait indices in early onset cases is a useful insight for clinicians to understand the clinical changes in their patients. This study clarifies the MDCs of trunk acceleration indices during walking in patients hospitalized with subacute stroke.

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