Motio Case Study 2: Utilizing Technology for Evaluating Functional Level in Transtibial Prosthesis Users - A Comparative Study

In today’s blog post of the Motio Case Study Series, we decided to present a study that compares the utilization of the Motio StepWatch technology to a traditional functional level rating method.

INTRODUCTION 

This brief study presents a technological approach for evaluating the functional level of transtibial prosthesis users. The assessment involved the daily use of a pedometer to collect step data-derived metrics, which, in conjunction with a small set of clinical information, facilitated a more objective Functional level determination compared to standard approaches. 

The primary objective of this study was to showcase the repeatability and reliability of this technology-driven functional assessment. Moreover, we aimed to emphasize the limitations of traditional functional level rating methods, as they fail to measure the individual's capacity to perform everyday activities under real-life conditions.

CASE PRESENTATION 

A 63-year-old female patient with a right transtibial amputation for 40 years who wears a prosthesis. Additionally, she has a hip prosthesis on the contralateral side. Clinically rated as a K-2, her prosthetic components suit her functional level. She does not require ambulation aids, even though she lives in an area with cobblestone streets and uneven terrain.

MANAGEMENT AND OUTCOME 

Two evaluations of her functional outcomes were performed at a six-month interval. Assessments involved retrieving AMPPRO and 2-Minute Walk Test (2MWT) results in the clinic and utilizing an activity monitor for 9 days to track step counts during community ambulation. Step count served a dual purpose: deriving performance metrics and identifying 2-minute gait bouts, referred to here as blind 2 Minute Continuous Walk Tests (B2MCWT).

The initial evaluation took place in August, coinciding with the town's popular festivities, in which she participated. In contrast, in February, six months later, no major events took place, and the patient only followed her daily routines, which consisted of extended walks along her town's boardwalk.

Table 1 - Sample of pedometer-collected data in the two evaluation periods. 

Table 1 presents a summary of select metrics obtained through pedometer data during the evaluation periods.

DISCUSSION 

By analyzing the daily step data, we observed a decline in both the average and maximum daily step count during the second assessment compared to the first.

While there are limited recommendations regarding the optimal step count for amputees, the studies reviewed in ​1​ indicate an average of 5929±3047 steps per day for transtibial amputees, which the patient surpasses by, on average, 45.6%.   

The patient's cadence values in both evaluations align with published reference values​ [2]​, which indicate a mean reference value of 103.78±9.48 steps per minute for transtibial amputees. Interestingly, her best-achieved cadences are typical of more active patients according to existing literature​ [3]​.

When comparing the 2MWT results in the clinic with the same continuous walking time collected blindly, in both evaluations, the patient covered an average of 12.9% less ground in two minutes of continuous walking (Table 1). This discrepancy can be attributed to the patient's unawareness of data collection, eliminating the potential influence of the "white-coat effect." This notable difference was significantly influenced by the patient's high daily step count, which positively affected her potential to vary cadence and her energy expenditure.

Regarding gait intensity, defined thresholds [​4]​ categorize the patient in a high-intensity range (+80 steps per minute) 37.1% of the time in the first evaluation and 43.8% in the second. This demonstrates her capacity to achieve a high cadence and vary it, which is crucial for assessing Functional levels.

CONCLUSION 

The Motio Functional Level assessment, which integrated clinical judgment with data from the pedometer-based evaluation, scored the patient above 3.5 on both evaluations. These results diverge from the previously assigned K level of 2, determined through in-clinic assessments like the AMPPRO and the PLUS-M™. The Motio Functional Level was largely influenced by the high number of steps taken per day during the patient’s daily life, which positively impacted her energy expenditure, and by her potential to vary cadence.

Daily monitoring provides valuable insights compared to clinic visits with less variability in gait speed and medium-intensity cadence.

This case study highlights the importance of real-life monitoring of prosthetic users through automated methods. Automated tests are not affected by short pauses, turns, different terrains, or obstacles, which can negatively impact the patient's reported average performance. This method will not only help clinicians saving time during appointments but also improve patient care, ensuring that the best is being offered.

Check out our blog post that highlights how the Motio StepWatch™ System can help improve communication and patient care!

REFERENCES 

​​[1] Wong CK, et al., Phys Ther. 2021 

​[2] Schmid-Zalaudek, K. et al., J Clin Med. 2022 

​[3] Godfrey B, et al. Journal of Prosthetics and Orthotics. 2018 

​[4] Orendurff MS, et al. J Rehabil Assist Technol Eng. 2016​