Dataset Information

IMU-based gait analysis in lower limb prosthesis users: Comparison of step demarcation algorithms.

ABSTRACT: BACKGROUND:Inertial Measurement Unit (IMU)-based gait analysis algorithms have previously been validated in healthy controls. However, little is known about the efficacy, performance, and applicability of these algorithms in clinical populations with gait deviations such as lower limb prosthesis users (LLPUs). RESEARCH QUESTION:To compare the performance of 3 different IMU-based algorithms to demarcate steps from LLPUs. METHODS:We used a single IMU sensor affixed to the midline lumbopelvic region of 17 transtibial (TTA), 16 transfemoral (TFA) LLPUs, and 14 healthy controls (HC). We collected acceleration and angular velocity data during overground walking trials. Step demarcation was evaluated based on fore-aft acceleration, detecting either: (i) maximum acceleration peak, (ii) zero-crossing, or (iii) the peak immediately preceding a zero-crossing. We quantified and compared the variability (standard deviation) in acceleration waveforms from superposed step intervals, and variability in step duration, by each algorithm. RESULTS:We found that the zero-crossing algorithm outperformed both peak detection algorithms in 65% of TTAs, 81% of TFAs, and 71% of HCs, as evidenced by lower standard deviations in acceleration, more consistent qualitative demarcation of steps, and more normally distributed step durations. SIGNIFICANCE:The choice of feature-based algorithm with which to partition IMU waveforms into individual steps can affect the quality and interpretation of estimated gait spatiotemporal metrics in LLPUs. We conclude that the fore-aft acceleration zero-crossing serves as a more reliable feature for demarcating steps in the gait patterns of LLPUs.

SUBMITTER: Bastas G

PROVIDER: S-EPMC6062463 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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IMU-based gait analysis in lower limb prosthesis users: Comparison of step demarcation algorithms.

Bastas Gerasimos G Fleck Joshua J JJ Peters Richard A RA Zelik Karl E KE

Gait & posture 20180522

<h4>Background</h4>Inertial Measurement Unit (IMU)-based gait analysis algorithms have previously been validated in healthy controls. However, little is known about the efficacy, performance, and applicability of these algorithms in clinical populations with gait deviations such as lower limb prosthesis users (LLPUs).<h4>Research question</h4>To compare the performance of 3 different IMU-based algorithms to demarcate steps from LLPUs.<h4>Methods</h4>We used a single IMU sensor affixed to the mid ...[more]

PMID: 29807270

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Project description:ObjectiveTo evaluate the content, construct, and discriminant validity of the Narrowing Beam Walking Test (NBWT), a performance-based balance test for lower limb prosthesis users.DesignCross-sectional study.SettingResearch laboratory and prosthetics clinic.ParticipantsUnilateral transtibial and transfemoral prosthesis users (N=40).InterventionsNot applicable.Main outcome measuresContent validity was examined by quantifying the percentage of participants receiving maximum or minimum scores (ie, ceiling and floor effects). Convergent construct validity was examined using correlations between participants' NBWT scores and scores or times on existing clinical balance tests regularly administered to lower limb prosthesis users. Known-groups construct validity was examined by comparing NBWT scores between groups of participants with different fall histories, amputation levels, amputation etiologies, and functional levels. Discriminant validity was evaluated by analyzing the area under each test's receiver operating characteristic (ROC) curve.ResultsNo minimum or maximum scores were recorded on the NBWT. NBWT scores demonstrated strong correlations (ρ=.70‒.85) with scores/times on performance-based balance tests (timed Up and Go test, Four Square Step Test, and Berg Balance Scale) and a moderate correlation (ρ=.49) with the self-report Activities-specific Balance Confidence scale. NBWT performance was significantly lower among participants with a history of falls (P=.003), transfemoral amputation (P=.011), and a lower mobility level (P<.001). The NBWT also had the largest area under the ROC curve (.81) and was the only test to exhibit an area that was statistically significantly >.50 (ie, chance).ConclusionsThe results provide strong evidence of content, construct, and discriminant validity for the NBWT as a performance-based test of balance ability. The evidence supports its use to assess balance impairments and fall risk in unilateral transtibial and transfemoral prosthesis users.

Project description:Despite their importance to fall prevention research, little is known about the details of real-world fall events experienced by lower limb prosthesis users. This gap can be attributed to the lack of a structured, population-specific fall survey to document these adverse health events. The objective of this project was to develop a survey capable of characterizing the circumstances and consequences of fall events in lower limb prosthesis users. Best practices in survey development, including focus groups and cognitive interviews with diverse samples of lower limb prosthesis users, were used to solicit input and feedback from target respondents, so survey content would be meaningful, clear, and applicable to lower limb prosthesis users. Focus group data were used to develop fall event definitions and construct a conceptual fall framework that guided the creation of potential survey questions and response options. Survey questions focused on the activity, surroundings, situation, mechanics, and consequences of fall events. Cognitive interviews revealed that with minor revisions, survey definitions, questions, and response options were clear, comprehensive, and applicable to the experiences of lower limb prosthesis users. Administration of the fall survey to a national sample of 235 lower limb prosthesis users in a cross-sectional preliminary validation study, found survey questions to function as intended. Revisions to the survey were made at each stage of development based on analysis of participant feedback and data. The structured, 37-question lower limb prosthesis user fall event survey developed in this study offers clinicians and researchers the means to document, monitor, and compare fall details that are meaningful and relevant to lower limb prosthesis users in a standardized and consistent manner. Data that can be collected with the developed survey are essential to establishing specific goals for fall prevention initiatives in lower limb prosthesis users.

Project description:BackgroundClinicians are routinely required to make decisions about fall risk among lower limb prosthesis (LLP) users. These decisions can be guided by standardized clinical balance tests but require population- and test-specific cutoff scores and validity indices to categorize individuals as probable fallers or nonfallers on the basis of test performance. Despite the importance of cutoff scores and validity indices to clinical interpretation of clinical balance test scores, they are rarely reported for LLP users. In their absence, clinicians cannot use results from clinical balance tests to assess the likelihood of a fall by any one patient.ObjectiveDerive cutoff scores, and associated validity indices, for clinical balance tests administered to established unilateral LLP users.DesignCross-sectional study.SettingOutpatient clinic and research laboratory.ParticipantsEstablished ambulatory unilateral transtibial and transfemoral prosthesis users (n?=?40).InterventionNot applicable.Main outcome measure(s)Optimal cutoff scores and related validity indices (ie, area under the curve, sensitivity, specificity, likelihood ratios) were computed for five balance tests, the activities-specific balance confidence scale (ABC), timed up and go (TUG), four square step test (FSST), Berg balance scale (BBS), and narrowing-beam walking test (NBWT).ResultsCutoff scores were identified for the NBWT (?.43/1.0), TUG (?8.17?seconds], FSST (?8.49 seconds), BBS (?50.5/56), and ABC (?80.2/100). Validity indices (ie, area under the curve, sensitivity, specificity, and likelihood ratios) for the NBWT, TUG, and FSST had greater diagnostic accuracy and provided more information about the probability of a fall than those for the BBS or ABC.ConclusionPerformance above or below identified cutoff scores for the NBWT, FSST, and TUG provides information about potentially important shifts in the probability of falling among established unilateral LLP users. These results can serve as initial benchmarks to reduce uncertainty surrounding fall risk assessment in established unilateral LLP users but require future prospective evaluation.Level of evidenceIII.

Project description:ObjectiveTo evaluate test-retest reliability and related measurement properties of items developed to assess best, worst, and average prosthetic socket comfort.DesignMethodological research to assess test-retest reliability of 4 individual socket comfort survey items. Socket comfort items were included in a self-report paper survey, which was administered to participants 2 to 3 days apart.SettingGeneral community.ParticipantsA minimum convenience sample of participants (N=63) was targeted for this study; 72 lower limb prosthesis users (>1y postamputation) completed the survey and were included in the final dataset.InterventionsNot applicable.Main outcome measureThe expanded socket comfort score (ESCS) was adapted from the original socket comfort score (SCS). The original SCS is a single-item self-report instrument developed to assess a lower limb prosthesis user's current socket comfort. Three additional items were designed to assess the user's best, worst, and average socket comfort over the previous 7 days.ResultsBest, worst, and average socket comfort items demonstrated better reliability, as indicated by higher intraclass correlation coefficients. As such, these items also exhibited lower measurement error and smaller minimal detectable change values than the item that measured current socket comfort. However, test-retest coefficients for all 4 ESCS items were below the level desired for evaluation of within-individual changes of socket comfort.ConclusionsItems that assess best, worst, and average comfort provide a more stable measurement of socket fit than the existing SCS instrument. Although administration of all 4 ESCS items may provide more comprehensive assessment of a lower limb prosthesis user's socket fit, administrators should expect variations in scores over time owing to the variable nature of the underlying construct over time. Future research should examine whether the ESCS provides an improved overall assessment of socket fit.

Dataset Information

IMU-based gait analysis in lower limb prosthesis users: Comparison of step demarcation algorithms.

Publications

IMU-based gait analysis in lower limb prosthesis users: Comparison of step demarcation algorithms.

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