A Novel Approach for Improving Gait Speed Estimation Using a Single Inertial Measurement Unit Embedded in a Smartphone: Validity and Reliability Study.

Background: Gait speed is a valuable biomarker for mobility and overall health assessment. Existing methods to measure gait speed require expensive equipment or personnel assistance, limiting their use in unsupervised, daily-life conditions. The availability of smartphones equipped with a single inertial measurement unit (IMU) presents a viable and convenient method for measuring gait speed outside of laboratory and clinical settings. Previous works have used the inverted pendulum model to estimate gait speed using a non-smartphone-based IMU attached to the trunk. However, it is unclear whether and how this approach can estimate gait speed using the IMU embedded in a smartphone while being carried in a pants pocket during walking, especially under various walking conditions. Objective: This study aimed to validate and test the reliability of a smartphone IMU-based gait speed measurement placed in the user's front pants pocket in both healthy young and older adults while walking quietly (ie, normal walking) and walking while conducting a cognitive task (ie, dual-task walking). Methods: A custom-developed smartphone application (app) was used to record gait data from 12 young adults and 12 older adults during normal and dual-task walking. The validity and reliability of gait speed and step length estimations from the smartphone were compared with the gold standard GAITRite mat. A coefficient-based adjustment based upon a coefficient relative to the original estimation of step length was applied to improve the accuracy of gait speed estimation. The magnitude of error (ie, bias and limits of agreement) between the gait data from the smartphone and the GAITRite mat was calculated for each stride. The Passing-Bablok orthogonal regression model was used to provide agreement (ie, slopes and intercepts) between the smartphone and the GAITRite mat. Results: The gait speed measured by the smartphone was valid when compared to the GAITRite mat. The original limits of agreement were 0.50 m/s (an ideal value of 0 m/s), and the orthogonal regression analysis indicated a slope of 1.68 (an ideal value of 1) and an intercept of -0.70 (an ideal value of 0). After adjustment, the accuracy of the smartphone-derived gait speed estimation improved, with limits of agreement reduced to 0.34 m/s. The adjusted slope improved to 1.00, with an intercept of 0.03. The test-retest reliability of smartphone-derived gait speed was good to excellent within supervised laboratory settings and unsupervised home conditions. The adjustment coefficients were applicable to a wide range of step lengths and gait speeds. Conclusions: The inverted pendulum approach is a valid and reliable method for estimating gait speed from a smartphone IMU placed in the pockets of younger and older adults. Adjusting step length by a coefficient derived from the original estimation of step length successfully removed bias and improved the accuracy of gait speed estimation. This novel method has potential applications in various settings and populations, though fine-tuning may be necessary for specific data sets.

Validity and Reliability of a Smartphone Application for Home Measurement of Four-Meter Gait Speed in Older Adults.

The four-meter gait speed (4MGS) is a recommended physical performance test in older adults but is challenging to implement clinically. We developed a smartphone application (App) with a four-meter ribbon for remote 4MGS testing at home. This study aimed to assess the validity and reliability of this smartphone App-based assessment of the home 4MGS. We assessed the validity of the smartphone App by comparing it against a gold standard video assessment of the 4MGS conducted by study staff visiting community-dwelling older adults and against the stopwatch-based measurement. Moreover, we assessed the test-retest reliability in two supervised sessions and three additional sessions performed by the participants independently, without staff supervision. The 4MGS measured by the smartphone App was highly correlated with video-based 4MGS (r = 0.94), with minimal differences (mean = 0.07 m/s, ± 1.96 SD = 0.12) across a range of gait speeds. The test-retest reliability for the smartphone App 4MGS was high (ICC values: 0.75 to 0.93). The home 4MGS in older adults can be measured accurately and reliably using a smartphone in the pants pocket and a four-meter strip of ribbon. Leveraging existing technology carried by a significant portion of the older adult population could overcome barriers in busy clinical settings for this well-established objective mobility test.

Mid-vastus total knee arthroplasty for medial osteoarthritis recovers gait balance control better than lateral parapatellar approach three months post-surgery.

Total knee arthroplasty (TKA) approaches affect recovery outcomes, with different levels of residual loss of muscle strength and functional deficits. The current study compared the gait balance control in older individuals 3 months after TKA via the lateral parapatellar approach (LPPA) and mid-vastus approach (MVA) in terms of the inclination angle (IA) of the center of pressure (COP) to the body's center of mass (COM) vector, and the rate of change of IA (RCIA). In a gait laboratory, 12 patients with severe medial knee osteoarthritis who had undergone bilateral TKA via LPPA and 12 via MVA were evaluated and compared against 12 healthy controls for their balance control during gait 3 months after surgery. The participants' kinematic data and ground reaction forces were measured synchronously using an 8-camera motion capture system and three forceplates, respectively, from which the COM, COP, IA and RCIA were calculated using a 13-body-segment model. The LPPA group showed significantly greater sagittal IA during DLS (p < 0.01) but less sagittal and frontal RCIA throughout the gait cycle (p < 0.04) compared to controls. The MVA showed better recovery in the balance control with most IA and RCIA variables similar to those of the healthy controls throughout the gait cycle. The patients with LPPA walked with a compromised balance control throughout the gait cycle while the MVA group showed close-to-normal balance control with a slight decrease in sagittal RCIA during SLS. The current between-approach findings were likely related to the differences in the muscles involved during surgery, suggesting that MVA may be a better choice than LPPA when taking short-term gait balance control into consideration.

Demographic Characteristics and Population Simulation of Newly Invasive Fall Armyworm on Arachis hypogaea (Fabales: Fabaceae) and Dominant Green Manure Plant in Taiwan.

Spodoptera frugiperda (J.E. Smith) is a severe and fast-spreading pest of numerous agro-economic crops, including miscellaneous, vegetables, and green manure crops. Understanding pest ecology represents a core component in integrated pest management decision-making. In Taiwan, peanut (Arachis hypogaea L.) is an important miscellaneous crop, whereas sesbania (Sesbania roxburghii Merr.) is the most frequently used green manure crop. To improve the S. frugiperda management in Taiwan, the demographic characteristics and population simulation of this pest reared on peanut and sesbania leaves were analyzed using the age-stage, two-sex life table theory. The intrinsic rate of increase, finite rate of increase, and net reproductive rate of S. frugiperda were higher when reared on peanut (0.1625 d-1, 1.1764 d-1, 264.9 offspring) than on sesbania (0.0951 d-1, 1.0997 d-1, and 30.3 offspring). Population projection of S. frugiperda on peanut demonstrated that this crop is a more suitable host plant than sesbania. Yet, this suboptimal host still assures an increasing trend of more than 357-fold individuals in 75 d, from the initial cohort of 10 eggs. Our data suggest that green manure plants in fallowing fields may support the pest's survival all year round, and may be responsible for a successful establishment and unexpected outbreaks of this invasive pest on the neighboring crops in Taiwan. Our study thus highlights the importance of assessing the population dynamics and areawide pest management of an invasive polyphagous pest on a noneconomic crop to mitigate the potential risk of reinfestation and thus outbreaks.

A Non-Linear Osteometric Modeling Method for Three-Dimensional Mandibular Morphological Changes During Growth: One-Year Monitoring of Miniature Pigs Using Cone-Beam Computed Tomography.

Knowledge of mandibular growth and development is essential for diagnosis of malformation and early interception. A previous method of quantifying mandibular growth using the distances between selected anatomical landmarks over the growth period does not provide a complete, quantitative description of the continuous growth patterns. The current study aimed to bridge the gap by measuring the 3D continuous growth of the mandible in miniature pigs using cone-beam computerized tomography (CBCT). The mandibles of the pigs were CBCT-scanned monthly over 12 months, and the 3D mandibular models were reconstructed. A new non-linear, time-dependent osteometric modeling approach was developed to register two consecutive mandible models by searching for the corresponding points with the highest likelihood of matching the anatomical and morphological features so that the morphological changes patterns for each month could be described using color maps on the models. The morphological changes of the mandible were found to decrease anteriorly, with the condyle region and the posterior part of the ramus growing faster than the rest of the mandible. The condyle region showed the fastest growth rate and the posterior ramus the second during the growth period, while the middle and anterior corpus regions showed the slowest growth rates. In conclusion, the current results revealed the non-linear patterns and rates of morphological changes in different growth regions and the whole mandible. The new approach may also be useful for future studies on the growth of the mandible in other animals.

Avascular Necrosis of the Hip Compromises Gait Balance Control in Female Juveniles With Unilateral Developmental Dysplasia Treated in Toddlerhood.

Avascular necrosis of the hip (AVN) is one of the most severe complications of surgical reduction when treating developmental dysplasia of the hip (DDH). The current study identified the differences in the balance control during walking in terms of the inclination angle (IA) of the center of pressure (COP) to the center of mass (COM), and the rate of change of IA (RCIA) between female juveniles with and without secondary AVN at the hip who were treated for unilateral DDH during toddlerhood as compared to their healthy peers. When compared to female healthy controls, the non-AVN group showed bilaterally similar compromised balance control with significantly decreased IA (p < 0.05) but increased RCIA (p < 0.04) in the sagittal plane during single-limb support (SLS) of the unaffected side, and in the frontal plane during terminal double-limb support (DLS) of the affected side. In contrast, the AVN increased between-side differences in the sagittal IA (p = 0.01), and sagittal and frontal RCIA during DLS (p < 0.04), leading to bilaterally asymmetrical balance control. Secondary AVN significantly reduced IA and RCIA in the sagittal plane (p < 0.05), and reduced range of RCIA in the frontal plane during initial DLS (p < 0.05). The trend reversed during terminal DLS, indicating a conservative COM-COP control in the sagittal plane and a compromised control in the frontal plane during body weight acceptance, with a compromised COM-COP control in the frontal plane during weight release. The current results suggest that increased between-side differences in the sagittal IA, and sagittal and frontal RCIA during DLS are a sign of AVN secondary to treated unilateral DDH in female juveniles, and should be monitored regularly for early identification of the disease.

Bilateral Asymmetry in Balance Control During Gait in Children with Treated Unilateral Developmental Dysplasia of the Hip.

INTRODUCTION: About 1% of the newborn population has developmental dysplasia of the hip (DDH), altering joint biomechanics, gait performance and balance control. Pemberton's osteotomy is used in early treatment but it remains unclear whether it will help the patient regain normal balance control during gait. The current study aimed to identify the changes of the whole-body balance control during level walking in children treated for unilateral DDH during toddlerhood, in terms of inclination angles (IA) of the line joining the body's center of mass (COM) and center of pressure (COP), and the rate of change of IA (RCIA). MATERIALS AND METHODS: Twelve girls (DDH group; age: 7.1 ± 2.1 years) who had been treated with Pemberton's osteotomy for unilateral DDH during toddlerhood and twelve healthy controls (Control group; age: 7.6 ± 2.1 years) walked at their preferred walking speed while IA, RCIA and temporal-spatial parameters were calculated from measured kinematic and forceplate data, and were compared using independent t-tests. RESULTS: Compared to the Control group, the DDH group showed significantly decreased sagittal IA (p = 0.042) but increased range of sagittal RCIA during SLS on the unaffected side (p = 0.006), and increased peak sagittal RCIA during DLS (p < 0.008). In the frontal plane, the altered COM-COP control occurred mainly during stance phase of the affected side, showing a decreased range of RCIA during SLS (p = 0.033) followed by decreased IA (p = 0.045) with an increased peak value of RCIA (p = 0.023) during terminal DLS. CONCLUSIONS: The children with treated unilateral DDH showed compromised, bilaterally different balance control strategies with altered COM-COP control during gait, not only during stance in the frontal plane as expected, but even more so during swing in the sagittal plane. It is thus suggested that routine assessment of the morphological changes and/or altered balance control of both the unaffected and affected hips is equally important for early identification of any signs of insidious hip problems, deteriorating balance control or increased risk of loss of balance.

Recovery of balance control in bilateral medial knee osteoarthritis after total knee arthroplasty during level walking.

Older adults are at higher risk of falling following total knee arthroplasty (TKA). However, it remains unclear how long a full recovery of the balance control during gait post-TKA will take. The current study aimed to bridge this knowledge gap via long-term follow-up gait analyses. Twelve older adults with severe bilateral medial knee osteoarthritis (OA) before, 3 and 12 months after TKA, and twelve healthy controls were evaluated for their balance control during level walking, in terms of the inclination angle (IA) of the center of pressure to center of mass vector, and the rate of change of IA (RCIA). The patients before TKA showed significantly increased sagittal IA but decreased RCIA throughout the gait cycle (p < 0.04) compared to controls, suggesting a compromised balance control. Three months post-TKA, deviations in IA remained, although those in RCIA were improved to normal. One-year post-TKA, no significant differences were found in any of the IA- and RCIA-related variables between patient and Control groups. The results show that TKA surgery was effective in reducing the deviations in the center of mass-center of pressure control in patients with severe bilateral knee OA, and full recovery of balance control can be expected 1 year after surgery.

Compromised balance control in older people with bilateral medial knee osteoarthritis during level walking.

About half of the elderly population has knee osteoarthritis (OA), showing altered gait patterns with increased fall risk. The current study aimed to identify the effects of severe bilateral medial knee osteoarthritis on gait balance control, in terms of the inclination angle (IA) of the center of pressure to center of mass vector, and the rate of change of IA (RCIA). Fifteen older adults with severe bilateral medial knee OA and 15 healthy controls walked at their preferred walking speed while the kinematic and forceplate data were measured to calculate IA, RCIA and temporal-spatial parameters. The OA group showed compromised gait balance control, due to a decreased average and range of sagittal RCIA over double-limb support (DLS, p < 0.002) and single-limb support (SLS, p < 0.002), as well as an increased sagittal IA (DLS, p < 0.005). Significantly decreased frontal RCIA averages during DLS, heel-strike and toe-off, and decreased RCIA ranges during SLS and swing (p < 0.027) were also observed. Reducing RCIA during DLS appeared to help reduce the loading rate and pain at the knees, and reduced RCIA at the subsequent SLS. The results indicated an increased risk of loss of balance in the OA group, and may warrant regular monitoring for reduced RCIA during gait to determine fall risk.

Postural adjustments in adolescent idiopathic thoracic scoliosis during walking.

INTRODUCTION: Adolescent idiopathic scoliosis (AIS) is the most common type of three-dimensional spinal deformity. Identifying the postural adjustments or changes for different phases and events is needed for developing programs to improve the AIS gait, but such information has been limited. The current study aimed to fill the gap via three-dimensional motion analysis of quiet standing and level walking in patients with severe thoracic AIS. MATERIALS AND METHODS: Sixteen female adolescents with AIS (Lenke 1 or 2, age: 14.9 ±â€¯1.7 years, height: 154.7 ±â€¯5.0 cm, mass: 41.7 ±â€¯7.2 kg) and sixteen sex-, age- and BMI-matched healthy controls (age: 14.8 ±â€¯2.7 years, height: 154.9 ±â€¯5.6 cm, mass: 44.7 ±â€¯6.3 kg) participated in the current study with informed written consent. The kinematic and kinetic changes between the trunk, pelvis, and lower limb segments, and at the lumbosacral level at different gait events were measured during quiet standing and level walking. RESULTS: The homogeneity of the current patient group helped reduce the effects of the level and severity of spinal deformity on inter-subject variability that has been associated with controversies over reported gait variables in AIS. The current results support the hypothesis that postural adjustments involving the trunk, pelvis and lower limb segments were needed in severe thoracic AIS during both quiet standing and level walking, and differed between concave and convex sides at different key gait events during level walking. CONCLUSIONS: Although scoliotic spinal deformity occurred mainly in the frontal plane, postural adjustments in all three planes were present at key events during level walking with associated joint loading changes in patients with severe thoracic AIS. Monitoring of such adjustments and the associated joint kinetic changes will be helpful for assessing the disease and treatment outcomes.