A wearable mobility assessment device for total knee replacement: A longitudinal feasibility study

Int J Surg. 2015 Jun;18:14-20. doi: 10.1016/j.ijsu.2015.04.032. Epub 2015 Apr 10.


Background: Total knee replacement currently lacks robust indications and objective follow-up metrics. Patients and healthcare staff are under-equipped to optimise outcomes. This study aims to investigate the feasibility of using an ear-worn motion sensor (e-AR, Imperial College London) to conduct objective, home-based mobility assessments in the peri-operative setting.

Methods: Fourteen patients on the waiting list for knee replacement, and 15 healthy subjects, were recruited. Pre-operatively, and at 1, 3, 6, 12 and 24 weeks post-operatively, patients underwent functional mobility testing (Timed Up and Go), knee examination (including range of motion), and an activity protocol whilst wearing the e-AR sensor. Features extracted from sensor motion data were used to assess patient performance and predict patients' recovery phase.

Results: Sensor-derived peri-operative mobility trends correlated with clinical measures in several activities, allowing functional recovery of individual subjects to be profiled and compared, including the detection of a complication. Sensor data features enabled classification of subjects into normal, pre-operative and 24-week post-operative groups with 89% (median) accuracy. Classification accuracy was reduced to 69% when including all time intervals.

Discussion: This study demonstrates a novel, objective method of assessing peri-operative mobility, which could be used to supplement surgical decision-making and facilitate community-based follow-up.

Keywords: Mobility; Post-operative; Sensor; Total knee replacement.

Publication types

  • Observational Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Arthroplasty, Replacement, Knee / rehabilitation*
  • Biomechanical Phenomena
  • Case-Control Studies
  • Exercise Therapy / instrumentation*
  • Feasibility Studies
  • Female
  • Humans
  • Longitudinal Studies
  • Male
  • Middle Aged
  • Osteoarthritis, Knee / surgery*
  • Postoperative Period
  • Prospective Studies
  • Range of Motion, Articular
  • Recovery of Function