Can a Smartphone be used for Balance Assessment during Walking in Lower Limb Amputees?

Nowadays, smartphones are equipped with an accelerometer module that can measure and record the body linear accelerations during walking. The aims of this study were: 1) reliability assessment of smartphone accelerometer for trunk accelerometry; 2) comparison of stability indices base on trunk accelerometry between the amputee and able-bodied subjects; and 3) comparison between energy storage and release (ESR) and multi-axis prosthetic feet users.

Eleven below-knee amputees (5 multi-axis and 6 ESR prosthetic feet) and 11 able-bodied subjects enrolled in this comparative study. The dynamic stability was assessed using a smartphone attached to their back through an elastic belt during walking in a 6-m walkway. Also, normalized root mean squares (nRMS) of mediolateral (ML) and anteroposterior (AP) directions were calculated as stability indices. The intraclass correlation coefficient (ICC), standard error of measurement (SEM), SEM%, and Bland-Altman plots were used for reliability analysis. The Independent T-test was also used to compare the healthy and amputee subjects as well as ESR and multiaxis prosthetic feet users. The critical alpha was set at 0.05.

The results showed that the accelerometer has the ICC values more than 0.97 and 0.89 for test-retest and inter-session, respectively. Amputees had significantly higher trunk accelerations in ML direction compared to able-bodied subjects (p=0.023) but not in AP direction (p=0.496). Although the results were not significant between ESR and multi-axis prosthetic feet (AP P= 0.16, ML P=0.44), the AP stability index was higher in ESR users (AP Multi-axis=117.45, ESR=127.38).

The smartphone can be used as a reliable measurement tool in clinical environments to assess the stability indices based on trunk accelerometry in transtibial amputees. More studies should be conducted to obtain more reliable results.