Abstract
Background Early postoperative physical activity in elderly patients suffering from proximal femoral fractures may reduce mortality. We hypothesized that activity trackers can reliably and objectively monitor the in-hospital mobilization, correlating with functional independence and quality of life. Methods Three different tracker types (Fitbit™ flex, Misfit™ Shine, and Axivity AX3) at three locations (wrist, ankle, and femur) recorded steps and signal vector magnitudes (SVM) in 22 patients. They were 81 ± 8 years old, were equally distributed between the sexes, and had an ASA score of 2.5 ± 0.6. Single protocoled activity events (n = 191) were clinically categorized into 4 levels and correlated with the monitored signals. Additionally, 2 ± 1 and 8 ± 3 days after the operation, the EuroQol-5D and the Barthel-20 index supplemented this data. Results All measurements at the wrist (Fitbit, Misfit) resulted in unacceptable accuracy; however, sensitivity and specificity reached around 90% using the Misfit at the ankle. Applying this combination, the correlation between real and measured steps (R2 = 0.99) and the category discrimination were statistically significant (p < 0.002). A discriminant analysis featured the calculation of four activity levels based on SVM measurements using the Axivity tracker at the femur. A cluster analysis showed a 100% agreement between the clinically observed and the calculated activity levels. The amount of active minutes or periods and both the EuroQol-5D and the Barthel-20 indices significantly increased between the analyzed time points after the operation. However, only the Barthel-20 was associated with the measured activity levels (p < 0.01). Conclusion The Misfit and the Axivity trackers can reliably monitor activity in elderly patients after operative treatment of proximal femur fractures. However, the wear location is decisive. Objectively measured activity correlated with functional independence and quality of life.
Highlights
Postoperative physical activity in elderly patients suffering from proximal femoral fractures may reduce mortality
A 3-axis accelerometer, Axivity AX3 (Newcastle upon Tyne, UK) was evaluated, which had the possibility of analyzing the raw accelerometer data and to develop and apply an own, adapted algorithm for activity measurement based on the calculated signal vector magnitudes (SVM)
During 121 protocoled activity events, physical activity was analyzed by registered steps
Summary
Postoperative physical activity in elderly patients suffering from proximal femoral fractures may reduce mortality. Three different tracker types (Fitbit flex, Misfit Shine, and Axivity AX3) at three locations (wrist, ankle, and femur) recorded steps and signal vector magnitudes (SVM) in 22 patients. They were 81 ± 8 years old, were distributed between the sexes, and had an ASA score of 2.5 ± 0.6. The Misfit and the Axivity trackers can reliably monitor activity in elderly patients after operative treatment of proximal femur fractures. Proximal femoral fractures are common in elderly patients and are associated with a high mortality of around 25–30% within the first year [1] This is determined by a variety of factors as comorbidity and age, which cannot or only partially be altered [2]. Activity trackers that are known as step counters or wearables have recently obtained growing interest for surveillance of motion and physical activity and have been successfully validated in young people [6,7,8]; differences between various
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