Step activity and stride-to-stride fluctuations are negatively correlated in individuals with transtibial amputation

Validation of Proprietary and Novel Step-counting Algorithms for Individuals Ambulating With a Lower Limb Prosthesis

OBJECTIVE

To compare the accuracy and reliability of 10 different accelerometer-based step-counting algorithms for individuals with lower limb loss, accounting for different clinical characteristics and real-world activities.

DESIGN

Cross-sectional study.

SETTING

General community setting (ie, institutional research laboratory and community free-living).

PARTICIPANTS

Forty-eight individuals with a lower limb amputation (N=48) wore an ActiGraph (AG) wGT3x-BT accelerometer proximal to the foot of their prosthetic limb during labeled indoor/outdoor activities and community free-living.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Intraclass correlation coefficient (ICC), absolute and root mean square error (RMSE), and Bland Altman plots were used to compare true (manual) step counts to estimated step counts from the proprietary AG Default algorithm and low frequency extension filter, as well as from 8 novel algorithms based on continuous wavelet transforms, fast Fourier transforms (FFTs), and peak detection.

RESULTS

All algorithms had excellent agreement with manual step counts (ICC>0.9). The AG Default and FFT algorithms had the highest overall error (RMSE=17.81 and 19.91 steps, respectively), widest limits of agreement, and highest error during outdoor and ramp ambulation. The AG Default algorithm also had among the highest error during indoor ambulation and stairs, while a FFT algorithm had the highest error during stationary tasks. Peak detection algorithms, especially those using pre-set parameters with a trial-specific component, had among the lowest error across all activities (RMSE=4.07-8.99 steps).

CONCLUSIONS

Because of its simplicity and accuracy across activities and clinical characteristics, we recommend the peak detection algorithm with set parameters to count steps using a prosthetic-worn AG among individuals with lower limb loss for clinical and research applications.

Reported Outcome Measures in Studies of Real-World Ambulation in People with a Lower Limb Amputation: A Scoping Review

Background: The rapidly increasing use of wearable technology to monitor free-living ambulatory behavior demands to address to what extent the chosen outcome measures are representative for real-world situations. This scoping review aims to provide an overview of the purpose of use of wearable activity monitors in people with a Lower Limb Amputation (LLA) in the real world, to identify the reported outcome measures, and to evaluate to what extent the reported outcome measures capture essential information from real-world ambulation of people with LLA. Methods: The literature search included a search in three databases (MEDLINE, CINAHL, and EMBASE) for articles published between January 1999 and January 2022, and a hand-search. Results and conclusions: 98 articles met the inclusion criteria. According to the included studies’ main objective, the articles were classified into observational (n = 46), interventional (n = 34), algorithm/method development (n = 12), and validity/feasibility studies (n = 6). Reported outcome measures were grouped into eight categories: step count (reported in 73% of the articles), intensity of activity/fitness (31%), type of activity/body posture (27%), commercial scores (15%), prosthetic use and fit (11%), gait quality (7%), GPS (5%), and accuracy (4%). We argue that researchers should be more careful with choosing reliable outcome measures, in particular, regarding the frequently used category step count. However, the contemporary technology is limited in providing a comprehensive picture of real-world ambulation. The novel knowledge from this review should encourage researchers and developers to engage in debating and defining the framework of ecological validity in rehabilitation sciences, and how this framework can be utilized in the development of wearable technologies and future studies of real-world ambulation in people with LLA.

A Scoping Review of Physical Activity in People With Lower-Limb Loss: 10,000 Steps Per Day?

OBJECTIVE

After amputation, people with lower-limb loss (PLL) face challenges to regain their previous physical activity level. Assessing the scope of evidence regarding physical activity in PLL can identify sources of evidence and gaps within the literature that can influence amputation-related research, outcome assessment choices, and wellness activities. The purpose of this scoping review was to map the evidence regarding steps per day as a physical activity measure for PLL. Specific aims were to (1) identify research designs, (2) catalog population subgroups, (3) document steps per day measurement methods, and (4) provide descriptive data for steps per day in PLL.

METHODS

The MEDLINE, CINAHL, Embase, Web of Science, and AMED databases; and the Journal of Prosthetics and Orthotics archive were searched without language or time limits. Exclusion criteria included no PLL subjects, not peer-reviewed, and no direct step count measure. Inclusion criteria allowed any sample size, nonprosthetic use, and self-reported step count. As a scoping review, only descriptive statistics were compiled, and no methodologic quality assessment was performed.

RESULTS

Twenty-one articles using crossover (8), cohort (4), cross-section (8), and case-study (1) designs were included that reported accelerometer (19) or pedometer (2) data. Studies often mixed amputation etiologies (15/21) and most (13/21) excluded transfemoral amputations. Studies primarily examined people with transtibial amputations (81.2%) and people at independent community walking levels (Medicare functional classifications: K3 = 49.2%, K4 = 36.3%). All 21 studies had fewer than 100 participants, and overall included 515 subjects (343, 66.6% male), mean (SD) age 53.2 (22.1) years. Mean (SD) number of pooled steps per day for PLL was 5087 (2998): 5929 (3047) for transtibial amputations and 3553 (2030) for transfemoral amputations.

CONCLUSIONS

Most PLL have low activity levels compared with the 10,000 steps per day generally recommended or 6000 common in people with diabetes. Research with larger samples, defined subgroups, and data along the recovery continuum would enhance knowledge of physical activity level in PLL.

IMPACT

This scoping review has identified gaps in the research related to steps per day as a measure of physical activity in people with lower-limb loss to guide future research.

LAY SUMMARY

People with lower-limb loss take fewer steps per day than suggested for general health. Increasing steps per day may be a useful goal for this population, and this study is a first step in improving knowledge of physical activity levels in people with lower-limb loss.

Technology for monitoring everyday prosthesis use: a systematic review

BACKGROUND

Understanding how prostheses are used in everyday life is central to the design, provision and evaluation of prosthetic devices and associated services. This paper reviews the scientific literature on methodologies and technologies that have been used to assess the daily use of both upper- and lower-limb prostheses. It discusses the types of studies that have been undertaken, the technologies used to monitor physical activity, the benefits of monitoring daily living and the barriers to long-term monitoring, with particular focus on low-resource settings.

METHODS

A systematic literature search was conducted in PubMed, Web of Science, Scopus, CINAHL and EMBASE of studies that monitored the activity of prosthesis users during daily-living.

RESULTS

Sixty lower-limb studies and 9 upper-limb studies were identified for inclusion in the review. The first studies in the lower-limb field date from the 1990s and the number has increased steadily since the early 2000s. In contrast, the studies in the upper-limb field have only begun to emerge over the past few years. The early lower-limb studies focused on the development or validation of actimeters, algorithms and/or scores for activity classification. However, most of the recent lower-limb studies used activity monitoring to compare prosthetic components. The lower-limb studies mainly used step-counts as their only measure of activity, focusing on the amount of activity, not the type and quality of movements. In comparison, the small number of upper-limb studies were fairly evenly spread between development of algorithms, comparison of everyday activity to clinical scores, and comparison of different prosthesis user populations. Most upper-limb papers reported the degree of symmetry in activity levels between the arm with the prosthesis and the intact arm.

CONCLUSIONS

Activity monitoring technology used in conjunction with clinical scores and user feedback, offers significant insights into how prostheses are used and whether they meet the user's requirements. However, the cost, limited battery-life and lack of availability in many countries mean that using sensors to understand the daily use of prostheses and the types of activity being performed has not yet become a feasible standard clinical practice. This review provides recommendations for the research and clinical communities to advance this area for the benefit of prosthesis users.

Residual limb fluid volume change and volume accommodation: Relationships to activity and self-report outcomes in people with trans-tibial amputation

BACKGROUND

Fluctuations in limb volume degrade prosthesis fit and require users to accommodate changes using management strategies, such as donning and doffing prosthetic socks.

OBJECTIVES

To examine how activities and self-report outcomes relate to daily changes in residual limb fluid volume and volume accommodation.

STUDY DESIGN

Standardized, two-part laboratory protocol with an interim observational period.

METHODS

Participants were classified as "accommodators" or "non-accommodators," based on self-report prosthetic sock use. Participants' residual limb fluid volume change was measured using a custom bioimpedance analyzer and a standardized in-laboratory activity protocol. Self-report health outcomes were assessed with the Socket Comfort Score and Prosthesis Evaluation Questionnaire. Activity was monitored while participants left the laboratory for at least 3 h. They then returned to repeat the bioimpedance test protocol.

RESULTS

Twenty-nine people were enrolled. Morning-to-afternoon percent limb fluid volume change per hour was not strongly correlated to percent time weight-bearing or to self-report outcomes. As a group, non-accommodators ( n = 15) spent more time with their prosthesis doffed and reported better outcomes than accommodators.

CONCLUSION

Factors other than time weight-bearing may contribute to morning-to-afternoon limb fluid volume changes and reported satisfaction with the prosthesis among trans-tibial prosthesis users. Temporary doffing may be a more effective and satisfying accommodation method than sock addition. Clinical relevance Practitioners should be mindful that daily limb fluid volume change and prosthesis satisfaction are not dictated exclusively by activity. Temporarily doffing the prosthesis may slow daily limb fluid volume loss and should be investigated as an alternative strategy to sock addition.

Step Activity and 6-Minute Walk Test Outcomes When Wearing Low-Activity or High-Activity Prosthetic Feet

OBJECTIVE

To determine changes in average daily step count (ADSC) and 6-minute walk test (6MWT) due to use of low-activity feet (LA) and high-activity energy-storage-and-return (ESAR) feet, and examine the sensitivity of these measures to properly classify different prosthetic feet.

DESIGN

Individuals with transtibial amputations (n = 28) participated in a 6-week, randomized crossover study. During separate 3-week periods, participants wore either a LA foot (eg, solid-ankle-cushioned-heel) or an ESAR foot. Differences in 6MWT and ADSC at the end of the 3-week period were recorded.

RESULTS

Subjects performed similarly in the 6MWT with the LA and ESAR foot (P = 0.871) and ADSC (P = 0.076). The correct classification of ESAR is only 51.9% and 61.5% with 6MWT and ADSC, respectively. For the LA foot, correct classification is less than 50% for both tests.

CONCLUSIONS

Neither ADSC or 6MWT are responsive to changes in prosthetic feet. The pitfalls and shortcomings of these instruments with regard to their ability to detect differences in prosthetic feet are outlined. Based on these results, it is not recommended that the 6MWT and ADSC are used as a means to assess outcomes for different prosthetic feet.