Introduction: Nowadays, smartphones are equipped with an accelerometer module that can measure and record the body linear accelerations during walking. The aims of this study are 1) reliability assessment of smartphone accelerometer for trunk accelerometry, 2) comparison of stability indices base on trunk accelerometry between amputees and abled bodies and also ESR and multi-axis prosthetic feet users.
Methods: 11 below-knee amputees (5 multi-axis and 6 carbon prosthetic feet) and 11 abled-body subjects enrolled in this study. The dynamic stability was assessed by means of a smartphone attached to their back by means of an elastic belt during walking in a 6m walkway and normalized RMS of ML and AP directions were calculated as stability indices. The ICC, SEM, SEM% and Bland-Altman plots were used for reliability analysis, also the Independent T-test was used to compare the healthy and amputee subjects and also ESR and multiaxis prosthetic feet users. The critical alpha was set at 0.05.
Results: 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 abled-bodies (p=0.023) but not for 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) but the AP stability index was higher in ESR users.
Conclusion: 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.