Rachel Senden

Acceleration-based gait test for healthy subjects: Reliability and reference data

Accelerometers enable us to analyse gait outside conventional gait laboratories. Before these devices can be used in large scale studies and in clinical settings a thorough evaluation of their performance in different populations is required. The aim of this study was to present an acceleration-based reference database for healthy gait. The repeatability and inter-observer reliability of acceleration-based gait analysis was investigated. The sensitivity was tested on different age groups and the effect of gender was studied. A comprehensive set of gait parameters (i.e. cadence, speed, asymmetry and irregularity) were studied in 60 women and 60 men. Basic gait parameters showed high repeatability (VC(cadence) 1.51%, ICC(cadence) 0.996) and inter-observer reliability (ICC(cadence) 0.916), while asymmetry and irregularity showed lower repeatability (VC(asym) 47.88%, ICC(asym) 0.787) and inter-observer reliability (ICC(asym) 0.449). The effects of age and gender on gait parameters were found to be consistent with those reported in studies using other methodologies. These findings and the advantages of the device support the application of AGA for routine clinical use and in daily life.

Accelerometry-based gait analysis, an additional objective approach to screen subjects at risk for falling ☆

This study investigated whether the Tinetti scale, as a subjective measure for fall risk, is associated with objectively measured gait characteristics. It is studied whether gait parameters are different for groups that are stratified for fall risk using the Tinetti scale. Moreover, the discriminative power of gait parameters to classify elderly according to the Tinetti scale is investigated. Gait of 50 elderly with a Tinneti>24 and 50 elderly with a Tinetti≤24 was analyzed using acceleration-based gait analysis. Validated algorithms were used to derive spatio-temporal gait parameters, harmonic ratio, inter-stride amplitude variability and root mean square (RMS) from the accelerometer data. Clear differences in gait were found between the groups. All gait parameters correlated with the Tinetti scale (r-range: 0.20-0.73). Only walking speed, step length and RMS showed moderate to strong correlations and high discriminative power to classify elderly according to the Tinetti scale. It is concluded that subtle gait changes that have previously been related to fall risk are not captured by the subjective assessment. It is therefore worthwhile to include objective gait assessment in fall risk screening.

Validity of an inertial measurement unit to assess pelvic orientation angles during gait, sit–stand transfers and step-up transfers: Comparison with an optoelectronic motion capture system*

An inertial measurement unit (IMU) allows kinematic evaluation of human motion with fewer operational constraints than a gold standard optoelectronic motion capture (MOCAP) system. The studys aim was to compare IMU and MOCAP measurements of dynamic pelvic orientation angles during different activities of daily life (ADL): gait, sit-to-stand (STS) transfers and block step-up (BS) transfers. A single IMU was attached onto the lower back in seventeen healthy participants (8F/9 M, age 19-31 years; BMI < 25) and optical skin markers were attached onto anatomical pelvic landmarks for MOCAP measurements. Comparisons between IMU and MOCAP by Bland-Altman plots demonstrated that measurements were between 2SD of the absolute difference and Pearsons correlation coefficients were between 0.85 and 0.94. Frontal plane pelvic angle estimations achieved a RMSE in the range of [2.7°-4.5°] and sagittal plane measurements achieved a RMSE in the range of [2.7°-8.9°] which were both lowest in gait. Waveform peak detection times demonstrated ICCs between 0.96 and 1.00. These results are in accordance to other studies comparing IMU and MOCAP measurements with different applications and suggest that an IMU is a valid tool to measure dynamic pelvic angles during various activities of daily life which could be applied to monitor rehabilitation in a wide variety of musculoskeletal disorders.

Clinimetric quality of the new 2011 Knee Society Score: High validity, low completion rate

BACKGROUND The demands of the younger and more active current total knee arthroplasty (TKA) patients are not in line with the current outcome assessments. Therefore, new questionnaires are developed or adjusted, as with the popular 1989 Knee Society Score (KSS). This study is the first to investigate the clinimetric parameters of the patient-reported outcome measurement (PROM) part of the 2011 KSS. METHODS Four-hundred-fifteen primary Dutch TKA patients were scored using the PROM part of the 2011 KSS. The scale is subdivided into an Objective (not evaluated), Satisfaction, Expectation and Function subscales. Clinimetric quality was evaluated by response and completion rate, test-retest reliability (n=29, intraclass correlation coefficient), internal consistency (n=172, Cronbachs alpha), construct validity (Pearsons correlations with 1989 KSS (n=75) and KOOS-PS (n=139)) and responsiveness (n=20, paired-samples t-test, effect sizes and floor and ceiling effects). RESULTS A response rate of 96% and completion rate of 43% were found. Reliability and internal consistency proved excellent with ICCs≥0.79 and Cronbachs alpha≥0.76 for all subscales. Strong correlations were found between the Function subscales of the 2011 KSS and KOOS-PS (r=-0.60 to -0.83). All subscales improved significantly after intervention, with exception of Walking & Standing and Discretionary Activities. 23% reached the maximum score postoperatively in Walking & Standing, indicating a ceiling effect. CONCLUSIONS The 2011 KSS is a reliable, internal consistent, construct valid and responsive questionnaire to assess the outcome of the Dutch TKA patients. Optimizations (e.g. shortening the scale, simplified design) are recommended to increase the disappointing completion rate. CLINICAL RELEVANCE The 2011 KSS is a reliable, internal consistent, construct valid and responsive questionnaire to assess the outcome of the Dutch TKA patients.

Acceleration-based motion analysis as a tool for rehabilitation: exploration in simulated functional knee limited walking conditions.

Objective: The aim of this study was to investigate the ability of acceleration-based gait analysis to differentiate between normal gait and different simulated functional knee limitations of increasing severity. Design: Gait of 48 healthy subjects was measured under four different walking conditions. Gait parameters (e.g., speed and asymmetry) were derived from trunk accelerations. Subjects walked a 20-m distance under four conditions: normal, simulated limited knee extension, simulated limited knee flexion, and simulated arthrodesis. The functional knee limitations were simulated using an adjustable knee brace on the right leg. Results: Acceleration-based gait analysis detected acute gait changes (i.e., speed, step length, step duration, cadence, vertical displacement, asymmetry, and irregularity) during the simulated functional knee limitations with high repeatability. The degree of change depended on the severity of the limitation, with the more severe limitations producing bigger changes in gait and the relative changes comparing well with literature values measured with laboratory-based motion analysis. Conclusions: Acceleration-based gait analysis is sensitive for different walking conditions. The easy and fast use, the production of objective gait characteristics, and the ability to differentiate functional knee limitations suggest its suitability for clinical rehabilitation.

Accelerometer-based Physical Activity Monitoring in Patients with Knee Osteoarthritis: Objective and Ambulatory Assessment of Actual Physical Activity During Daily Life Circumstances.

Background: It is important to assess physical activity objectively during daily life circumstances, to understand the association between physical activity and diseases and to determine the effectiveness of interventions. Accelerometer-based physical activity monitoring seems a promising method and could potentially capture all four FITT (i.e. Frequency, Intensity, Time, Type) components of physical activity considered by the World Health Organization (WHO). Aim: To assess the four FITT components of physical activity with an accelerometer during daily life circumstances and compare with self-reported levels of physical activity in patients with knee osteoarthritis (OA) and a healthy control group. Methods: Patients (n=30) with end-stage knee OA and age-matched healthy subjects (n=30) were measured. An ambulant tri-axial accelerometer was placed onto the lateral side of the upper leg. Physical activity was measured during four consecutive days. Using algorithm-based peak detection methods in Matlab, parameters covering the four FITT components were assessed. Self-reported physical activity was assessed using the Short questionnaire to assess health enhancing physical activity (SQUASH). Results: Knee OA patients demonstrated fewer walking bouts (154 ±79 versus 215 ±65 resp.; p=0.002), step counts (4402 ±2960 steps/day versus 6943 ±2581 steps/day; p=0.001) and sit-to-stand (STS) transfers (37 ±14 versus 44 ±12; p=0.031) compared to controls. Knee OA patients demonstrated more time sitting (65 ±15% versus 57 ±10% resp.; p=0.029), less time walking (8 ±4% versus 11 ±4% resp.; p=0.014) and lower walking cadence (87 ±11steps/min versus 99 ± 8steps/min resp.; p<0.001). Accelerometer-based parameters of physical activity were moderately-strong (Pearsons’s r= 0.28-0.49) correlated to self-reported SQUASH scores. Conclusion: A single ambulant accelerometer-based physical activity monitor feasibly captures the four FITT components of physical activity and provides more insight into the actual physical activity behavior and limitations of knee OA patients in their daily life.

Importance of correcting for individual differences in the clinical diagnosis of gait disorders

OBJECTIVE To quantify the effects of subject characteristics on gait parameters using acceleration-based gait analysis. DESIGN Cross-sectional study with a single group cohort. SETTING Hospital setting. PARTICIPANTS One hundred and twenty healthy subjects (six age decade groups of 10 men and 10 women) performed a 20-m walking test. METHODS Basic gait parameters (e.g. speed) and other clinically relevant parameters (e.g. step time asymmetry) were assessed during a 20-m walking test using a tri-axial accelerometer, attached at the level of the sacrum. Subject characteristics were recorded. RESULTS Between 34% and 51% of the variability in gait parameters was explained by age, height and gender. Subject characteristics contributed less to the variance in step time asymmetry (R(2)=0.02), gait irregularity (R(2)=0.07) and vertical displacement of the centre of mass (R(2)=0.17). Relationships identified were comparable with previous studies (e.g. faster walking speed in men, younger and taller subjects). CONCLUSIONS Age, height and gender are determinants of basic gait parameters, while their influence on gait irregularity and step time asymmetry is minimal. This indicates that gait is variable between subjects, showing the relevance of correcting gait for subject characteristics. This study describes preliminary work to build a database of gait parameters in healthy participants, describing the effects of age, gender and height. Further studies to extend this database with patients would provide further relevance to clinical practice.

The influence of age, muscle strength and speed of information processing on recovery responses to external perturbations in gait

Dynamic imbalance caused by external perturbations to gait can successfully be counteracted by adequate recovery responses. The current study investigated how the recovery response is moderated by age, walking speed, muscle strength and speed of information processing. The gait pattern of 50 young and 45 elderly subjects was repeatedly perturbed at 20% and 80% of the first half of the swing phase using the Timed Rapid impact Perturbation (TRiP) set-up. Recovery responses were identified using 2D cameras. Muscular factors (dynamometer) and speed of information processing parameters (computer-based reaction time task) were determined. The stronger, faster reacting and faster walking young subjects recovered more often by an elevating strategy than elderly subjects. Twenty three per cent of the differences in recovery responses were explained by a combination of walking speed (B=-13.85), reaction time (B=-0.82), maximum extension strength (B=0.01) and rate of extension moment development (B=0.19). The recovery response that subjects employed when gait was perturbed by the TRiP set-up was modified by several factors; the individual contribution of walking speed, muscle strength and speed of information processing was small. Insight into remaining modifying factors is needed to assist and optimise fall prevention programmes.

Clinical validation of a body-fixed 3D accelerometer and algorithm for activity monitoring in orthopaedic patients

Summary Background/Objective Activity is increasingly being recognized as a highly relevant parameter in all areas of healthcare for diagnosis, treatment, or outcome assessment, especially in orthopaedics where the movement apparatus is directly affected. Therefore, the aim of this study was to develop, describe, and clinically validate a generic activity-monitoring algorithm, satisfying a combination of three criteria. The algorithm must be able to identify, count, and time a large set of relevant daily activities. It must be validated for orthopaedic patients as well as healthy individuals, and the validation must be in a setting that mimics free-living conditions. Methods Using various technical solutions, such as a dual-axis approach, dynamic inclinometry (hip flexion), and semiautomatic calibration (gait speed), the algorithms were designed to count and time the following postures, transfers, and activities of daily living: resting/sitting, standing, walking, ascending and descending stairs, sit–stand transitions, and cycling. In addition, the number of steps per walking bout was determined. Validation was performed with healthy individuals and patients who had undergone unilateral total joint arthroplasty, representing a wide spectrum of functional capacity. Video observation was used as the gold standard to count and time activities in a validation protocol approaching free-living conditions. Results In total 992 and 390 events (activities or postures) were recorded in the healthy group and patient group, respectively. The mean error varied between 0% and 2.8% for the healthy group and between 0% and 7.5% for the patient group. The error expressed in percentage of time varied between 2.0% and 3.0% for both groups. Conclusion Activity monitoring of orthopaedic patients by counting and timing a large set of relevant daily life events is feasible in a user- and patient-friendly way and at high clinical validity using a generic three-dimensional accelerometer and algorithms based on empirical and physical methods. The algorithms performed well for healthy individuals as well as patients recovering after total joint replacement in a challenging validation set-up. With such a simple and transparent method real-life activity parameters can be collected in orthopaedic practice for diagnostics, treatments, outcome assessment, or biofeedback.

Physical functioning of low back pain patients: perceived physical functioning and functional capacity, but not physical activity is affected

Abstract Purpose: Physical functioning is a multidimensional construct covering perceived functioning, functional capacity and actual physical activity. Currently, the assessment of physical functioning in low back pain (LBP) patients has been limited to only one or two of these aspects. This study evaluates physical functioning of LBP patients by assessing the three individual aspects using questionnaires and ambulant sensor-based measurements. Methods: Actual physical activity, functional capacity and perceived functioning were measured in 26 patients undergoing patient specific treatment before, direct and 3–4 weeks after the first treatment using, respectively, sensor-based activity monitoring, sensor-based motion analysis test and the Oswestry questionnaire. Patients were compared to a healthy control group. Results: Perceived functioning and functional capacity, but not actual physical activity is impaired in pre-treatment LBP patients. After treatment, patients improved in perceived physical functioning and functional capacity approaching healthy levels, however only slight (p > 0.05) improvements in actual physical activity were found. Moreover, only few and weak correlations were found between the different aspects of physical functioning. Conclusion: Perceived functioning, actual physical activity and functional capacity are three independent outcome dimensions, being complementary but not redundant. Especially, perceived functioning and physical capacity need attention when evaluating LBP patients during rehabilitation. Implications for Rehabilitation Perceived physical functioning and physical capacity are negatively affected by low back pain and improve after treatment. Low back pain patients perform their daily activity independent of pain and complaints. Inertia sensor-based motion analysis can objectify treatment effects showing low back pain patients their progress in rehabilitation. New interventions can be justified with inertia sensor technology in low back pain patients.