Wearable motion sensor(s) to measure change of physical function in patients after total knee replacement.

Total knee replacement (TKR) is a successful surgical intervention for patients
with advanced osteoarthritis (OA) to reduce pain and improve physical function.
However, about 20% of the patients is not satisfied one year after TKR.
Therefore, it is necessary to gain knowledge about the factors involved in
dissatisfaction and ultimately help patients who are unsatisfied as early as
possible.

At this moment, Patient Reported Outcome Measures (PROMs) are the only
standardized way to measure success and recovery rate of TKR. A wearable sensor
system could provide an unobtrusive and inexpensive way to determine recovery
rate during rehabilitation.

Wearable sensors are used more often to measure physical function and movement
non-invasively over longer periods of time. Inertial measurement units (IMUs)
containing accelerometer, gyroscope, magnetometer and in some cases barometers
have been used to study kinematics during activities of daily living (ADL),
e.g. walking, stair climbing, getting up from a chair. Other sensors, such as
pressure insoles, smartwatches and smartphones have been used to track activity
level in a more generic way. A smartwatch with electrodes has been used to
measure skin conductance, to determine physiological stress response to both
acute and transient stimuli. Taken together, there are enough sensors that can
be used to measure physical function of patients after TKR, but the question
remains which one is the best.
In a previous study at Imec, we have measured several healthy volunteers with
multiple wearable sensors: IMUs, pressure insoles, smartwatch with electrodes
on the skin and an ECG-patch. The results of this study show that these sensors
can be used to calculate multiple parameters of physical function during
multiple activities of daily life (ADL). Where each method has a certain
accuracy (for example +/- 1 degree in calculation of the knee angle). Multiple
of these functional parameters are known to be important in physical recovery
after TKR. It remains to be determined which sensor is suitable to measure
change in physical function of TKR patients after surgery.

The aim of this study is to determine which wearable motion sensors are
suitable to measure change in physical function of TKR patients after surgery.

Following this objective, we will explore if the changes in physical function,
as measured with wearable sensors, is related to the PROMs. The results of this
study can be used to monitor patients during their recovery and provide insight
in the cause of unsatisfied patients after TKR.

The primary endpoint is based on the abovementioned primary study parameters:
* A selection of wearable motion sensors that is suitable to measure change in
physical function of TKR patients after surgery. In addition, the relation
between these functional parameters and PROMs.

Secondary endpoints:
* Relation between pre-operative expectation (of multiple ADL) of the subject
and the surgeon, and the PROMs.
* Relation between patient specific parameters (biometrics, lifestyle,
comorbidities, mental fitness), and the PROMs.
* Correlation between patient reported acute pain and physiological stress
response/ movement patterns during ADL.
* Correlation between the activity level at home of the wrist worn device
(fitbit) and the smartphone based (Sentiance application).
Rationale behind these objectives can be found in Chapter 2 of the
Investigation Protocol.

The data required for this study will be gathered from 25 patients with
osteoarthritis (wearing) of the knee, who will undergo TKR. In total, the
subjects will be measured at five separate sessions: pre-operative (2-4 weeks),
post-operative at 2 days, 2 weeks, 6 weeks and 12 weeks. Each measurement
session is the same and takes about 45 minutes.
At each measurement session , the following wearable sensors will be used:
- 15 IMUs on the lower and upper legs, pelvis, fore and upper arms, shoulders,
chest, head and feet.
- Pressure insoles in shoes (left and right)
- Smartwatch (right arm)
- ECG-sensor on chest patch.
At the first measurement session there will be asked 2 additional
questionnaires: Hospital Anxiety and depression scale, HADS: 14 questions,
expectation questionnaire based on multiple ADL: 22 questions. For the rest of
the measurement session, and each other session, the subjects will be asked to
do the following:
- 2 questionnaires (KOOS-PS: 7 questions, Patient knee implant performance,
PKIP: 24 questions)
- Let researcher apply all abovementioned sensors
- Perform the following activities. After each activity the subject will be
asked to rate the pain and confidence during that specific activity on a visual
analog scale (VAS).
o Walking at self-selected normal speed (40m).
o Stand up out of normal and deep chair (seat is 40cm from the ground)
o Timed Up and Go (TUG) (see Appendix)
o Getting in and out of a bed
o Pick keys up from the ground
o Stair climbing (at self-selected speed) 12 steps up and down.
o Standing still (10s)
o Passive Range of Motion (ROM) of knee and hip of the dominant leg. Lying on a
bed, the research assistant will bend the knee and extend hip.
In case the subject is not able to perform the activity, the activity will be
skipped and continued with the next one.

In between the measurement sessions, the subjects receive an activity monitor
(Fitbit) to take home. They will be asked to wear the monitor as much as
possible for 4 days after the session. In addition, the subjects will be
provided the option of installing an application on a mobile phone (their own,
or one provided by the researchers). The subject will be asked to carry the
mobile phone with them for 4 days.
Both the Fitbit and the application measure the movement of the subject outside
the sessions, and the Fitbit also measures the heartrate. The data of these
devices will be collected at each measurement session, so the subjects do not
have to have access to the internet.

For this study, the following patient information will be gathered from the
orthopaedic surgeon or the principal investigator:
- Biometrics of the subject
- Comorbidities
- Details of the surgical intervention and type of implant.
- Medication during and after surgery.
- Questionnaire about expectation from the surgeon about the physical
activities possible for the patient 3 months after the surgery (see folder F.
vragenlijsten).

- Answer questionnaires
- perform ADL, while wearing multiple sensors on the body.
- wear an activity monitor (Fitbit) and the optional mobile phone with
application at home.

No significant risks or immediate benefits are expected for the participants.
A potential small risk consists of skin irritation due to the wearing of the
activity monitor or the ECG-patch. This risk is mitigated with the exclusion
criteria and the instructions of the researcher for using the activity monitor.
The additional burden for the subjects consists of: the time it takes to carry
out the measurements (approx. 45 min per session) and the time it takes to
travel to the hospital for 3 additional appointments. The traveling expenses
will be reimbursed.