Monitoring activity of inpatient lower limb prosthetic users in rehabilitation using accelerometry: Validation study

Due to limited accuracy of self-reported activities of lower limb prosthetic users, there is increasing interest in providing accurate walking time for those who are mobilising using their prosthesis in the rehabilitation ward. The aim of this study was to test the accuracy of a tri axial accelerometer (ActivPAL) in measuring walking activity of amputee patients while using their prosthetic limb.

For the study, 21 subjects wore accelerometer devices taped to the thigh on both the amputated and non-amputated side. Each subject was asked to perform a set of activity routines: walking with prosthesis for 5 minutes, self-propelling in a wheel chair for 3 minutes and being pushed in a wheel chair for 3 minutes. Each activity was observed and timed by a physiotherapist and the observed times were compared with the output from accelerometer monitoring.

Using the Bland-Altman method, the mean difference between observed and ActivPal monitor for total time spent walking for the non-amputated side was 0.004 seconds (limits of agreement -0.09 to 0.10 seconds) and for amputated side was 0.11 seconds (limits of agreement -0.43 to 0.66 seconds). An analysis between monitored and observed time found the sensitivity for the non-amputated side was 90.5% and 86% for the amputated side.

The use of ActivPAL accelerometers in measuring walking time for an individual using a prosthesis is within acceptable levels of accuracy for continuous ambulation monitoring. It has potentially important clinical application for prescribing prostheses.