interACTION: A Portable Joint Function Monitoring and Training System for Remote Rehabilitation Following Total Knee Arthroplasty
Phase: NA
Conditions: Total Knee Arthroplasty
Sponsor: James J. Irrgang

Title: InterACTION: A Portable Joint Function Monitoring 
and Training System for Remote Rehabilitation following 
Total Knee Arthroplasty 
Principal Investigator: James Irrgang 
Trial Registration: ClinicalTrials.gov Identifier NCT02646761 
12/18/2018 

 
Abstract 
 
Background 
 
Post-operative rehabilitation is essential to optimize outcomes following orthopaedic 
surgeries. Lack of patient compliance to this prescribed rehabilitation therapy has 
been reported to be as high as 65%. This lack of rehabilitation compliance effects 
patients by prolonging pain and dysfunction and diminishing quality of life and acts 
as a strain on the healthcare system by increasing the overall burden of care, 
including increased duration of rehabilitation, increased rates of readmission, and 
re-operation. 
 
Purpose 
 
The purpose of this pilot study is to ascertain if home-based therapy with 
monitoring via telemedicine can overcome barriers to compliance and improve 
rehabilitation. 
 
Methods 
 
Sixty patients following total knee arthroplasty will be monitored for up to 10 weeks 
during their outpatient physical therapy course. For the control group, 30 of these 
patients will undergo two to three weekly sessions with a physical therapist 
supplemented by unmonitored home-based exercises. The second group of 30 
patients will fulfill their rehabilitation course with one to three sessions per week 
with a physical therapist and will use the interACTION home rehabilitation 
monitoring program to supplement these sessions. The patients in the interACTION 
group will use the device for the first two weeks of their rehabilitation in the clinic in 
order to become familiar with the device before home use. After the first two weeks 
the patient will be asked to take the device home and reduce their weekly 
outpatient visits by one visit per week. However, if the physical therapist feels it is 
best for the patient to deviate from the protocol, this is allowed. At the end of the 
10-week rehabilitation course, rehabilitation compliance, costs, and patient 
outcomes will be analyzed for differences between the two groups. 
 
Significance 
 
If home-based therapy is successful, post-operative patients in the future would be 
allowed to perform guided rehabilitation therapy at home, and physicians would be 
able to monitor patients’ rehabilitation progress without the limiting factor of 
patients being present onsite or performing the exercises incorrectly, potentially 
improving patient outcomes and lowering healthcare costs and expenditures. 
 
 
 
 
 

Background 
 
Adequate rehabilitation following total knee arthroplasty (TKA) is crucial to optimize 
patient function and quality of life. Attaining adequate strength and range of motion 
is essential to regain the function of the knee and permit patients to resume their 
regular activities after surgery. Despite acknowledgement of the importance of 
post-operative rehabilitation after TKA, the current system is far from perfect. First, 
patients are expected to perform their rehabilitation program once or twice a day 
following surgery, but traditional rehabilitation protocols generally include only one 
to three sessions of outpatient physical therapy per week. As a result, the patient is 
left to perform exercises unmonitored for the majority of their recovery period. 
Second, barriers to rehabilitation are a concern for patients, including limited 
mobility/access and growing copay expenses. Lastly, the fragmented nature of the 
physical therapy landscape does not provide the physician or patient with a 
guarantee of a standardized, proven course of rehabilitation. This also makes 
accurate and meaningful communication between the physical therapist and 
physician a difficult task. 
 
Altogether, these difficulties strain the optimal delivery of rehabilitation following 
TKA. Overall compliance to a complete rehabilitation program under the current 
standard of care approach to rehabilitation has been shown to be as low as 35% 
(Sluijs, Phys Ther, 1993). 
 
Non-compliance, defined as incomplete or incorrect execution of prescribed 
treatments, represents significant waste in healthcare and negatively affects 
outcomes leading to prolonged pain, greater activity limitations and participation 
restrictions, a longer duration of recovery, poorer quality of life, and the potential 
for increased hospital readmissions and additional surgical interventions (Martin, 
2005). Use of telemedicine to monitor patients has overcome barriers to compliance 
and reduced costs in other fields of medicine (Elkjaer, 2012). Early attempts to 
implement telerehabilitation have demonstrated a strong potential for the success 
of this approach in improving compliance (Russell, 2010). However, effective, 
scalable monitoring of prescribed exercises is currently limited by lack of portable, 
accurate, precise, interactive, and cost-effective tools. To date, remote 
rehabilitation or home exercise programs for rehabilitation after surgery or injury 
lack adequate supervision, patient motivation, patient-therapist communication, 
and personalized treatment plans. 
 
Physical therapists can promote compliance in conventional rehabilitation by 
tracking patient adherence using log books, existing mobile apps, or activity 
monitors. However, log books rely on patients for accurate data entry and provide 
no means for communication or corrective feedback, existing mobile apps cannot 
track joint motion or provide corrective feedback, and activity monitors do not 
measure joint-specific function (quantity and quality of motion). Thus, current tools 
fail to quantify exercise over time in or out of the clinical setting. 
 
InterACTION is a joint motion monitoring and training tool consisting of a wearable, 
portable motion capture device and a web-based software application for recording 

and transmitting data. Sensors, placed on either side of a joint, collect joint motion 
and position data. Data is stored on a Bluetooth paired tablet. Motion data collected 
by interACTION is analyzed and displayed in a customizable, joint-specific manner 
in patient and therapist modes. The patient uses the system as often as indicated 
by their physical therapist to learn about the prescribed exercises, follow a 
personalized exercise program, demonstrate adherence to the treatment plan, and 
communicate problems with their physical therapist and receive interactive 
feedback. Patients also have the ability to view their rehabilitation progress. 
 
A web-accessible, password-protected portal allows a local or remote physical 
therapist to monitor the patient’s progress. Physical therapists have access to the 
data to analyze patient progress and compliance and review computer-generated 
alerts. Capabilities in the clinician portal include assessment of patient data during 
exercises and activities of daily living (ADLs), weekly progress reports by reviewing 
changes in important variables (i.e. range of motion, pain, patient-reported activity, 
participation, quality of life). The ability to monitor progress ensures the patient’s 
compliance to the treatment program and allows clinicians to update the patient’s 
exercise regimen as needed.  
 
Use of the interACTION system has the potential to allow physical therapists to 
improve patient-oriented outcomes, streamline utilization of clinical resources, and 
provide care more efficiently for a larger number of patients. In turn, patients will 
be more confident and compliant with performance of their prescribed exercise 
program and will receive feedback on their recovery progress. However, research is 
needed to demonstrate these hypothesized benefits of the interACTION system. 
 
Significance 
 
The interACTION telerehabilitation system provides flexibility and potential 
application at all stages of patient care, with easy implementation for patients at 
both the lower levels of the functional spectrum (e.g. immediately after joint 
surgery), as well as higher functioning individuals (e.g. >6 months post-op, 
athletes with persistent joint pain). The quality of care will improve as the 
therapist-patient relationship is strengthened by (i) providing valuable information 
about the patient’s daily progress, (ii) improving compliance with the prescribed 
exercises, and (iii) facilitating communication/feedback between patient and 
physical therapist. By including physical therapists’ guidance through the online 
activity manager and direct feedback, the patient will gain confidence that they are 
on the proper course for recovery. The physical therapist can monitor the progress 
of their patients to ensure joint function is improving and increase the patient’s 
motivation and compliance to the prescribed therapy. 
 
Methods 
 
 
For this randomized treatment study, we will recruit 60 patients that have 
undergone total knee arthroplasty (TKA) that are being referred for post-operative 
outpatient physical therapy. After obtaining informed consent, and upon successful 

screening/recruitment, subjects will be randomly assigned to one of two groups: 
1. Control Group: Rehabilitation performed by a physical therapist and 
supplemented with a home exercise program for a maximum of ten weeks. 
Therapy will consist of two to three visits per week as prescribed by the 
physical therapist and based on the best interest of the patient. Patients will 
record their performance of the prescribed home exercise programs on a 
paper-based exercise log on a daily basis. 
2. InterACTION Intervention Group: Rehabilitation performed by a physical 
therapist and supplemented by use of interACTION for a maximum of ten 
weeks. This will include two to three visits per week for two weeks in which 
the patient will use interACTION during routine outpatient physical therapy 
sessions to familiarize them with the system. After two weeks, the patient 
will be issued an interACTION device for home use that will guide them 
through their exercise program. At this point subjects in the interACTION 
group should continue to return to the outpatient rehabilitation facility, but 
reduce their weekly routine visit with their physical therapist by one during 
the next eight weeks of recovery, while concurrently using interACTION at 
home. Patients who attended two visits per week for the first two weeks 
should subsequently attend one visit per week. Patients who attended three 
visits per week for the first two weeks will subsequently attend one to two 
visits per week. However, if the physical therapist feels it to be in the best 
interest of the patient to deviate from the protocol, this is allowed. 
Note: InterACTION is currently under development, not a commercial 
application. The 3rd Party Developer was OpenArc, LLC (109 Vip Drive Suite 
200, Wexford, PA 15090). The mobile application is currently supported on a 
Nexus tablet with Android operating system (specifically lollipop and kitkat 
versions). The mobile application and the kinematic sensors will be provided 
to the participant, the participants will NOT use a personal device. 
 
Rehabilitation Compliance will be evaluated by the study team through the use of 
home exercise logs and interACTION reports. Logs will be reviewed at the follow-up 
visits with the research team. Outcome measures will be collected at baseline, 5 
weeks (+/- 7 days) after enrollment, and upon discharge or a maximum of 10 
weeks (+/- 7 days) after enrollment. 
 
Outcomes 
 
• 
Range of motion—Active and passive range of motion (ROM) will be 
measured with a standard goniometer while the patient lies in the supine 
position. Extension and flexion of each knee will be measured. Extension will 
be measured passively with a quad set and actively during a straight leg 
raise. The range of extension and flexion will be expressed as the difference 
between the involved and non-involved knees. 
• 
Numeric Pain Rating Scale—Subjects will be asked to rate their level of pain 
currently and their level of worst & least pain in the past 24 hours on a scale 
from 0 (no pain) to 10 (worst pain imaginable). 
• 
Activities of Daily Living Scale of the Knee Outcome Survey (ADLS)—The 
ADLS is a 14-item measure of symptoms and activity limitations for 

individuals with a variety of knee impairments. 
• 
Veterans RAND 12-Item Health Survey (VR-12)—The VR-12 is a 12-item 
patient-reported general measure of health-related quality of life that was 
adapted and developed from the RAND 36-Item Health Survey at the RAND 
Corporation and Medical Outcomes Study. 
• 
Functional performance will also be tested in all patients. The following 
functional tests will be assessed at 5- and 10-week visits: 
o Six-minute Walk Test to assesses the subject's ability to walk 
community distances. The subject is asked to walk as far as possible in 
six minutes on a closed course with standing rest breaks as needed. 
The patient is free to use their preferred assistive device. 
o The Stair Climbing Test to test basic daily function in which a patient 
ascends and descends a standard flight of stairs as quickly and safely 
as possible, using their preferred gait pattern, assistive device, and 
hand rail. 
o The Timed Up and Go Test (TUG) in which the patient sits in a 
standard armed chair, rises, walks three meters, turns around, walks 
back to the chair and sits. Excessive time to complete the TUG can 
indicate mobility impairments and potential fall risks in elderly 
patients. 
o The Unilateral Balance Test in which the patient attempts to maintain 
single leg balance for up to two minutes, with the test ending when 
the patient loses balance enough to put the opposite foot on the 
ground. 
 
Subjects will also undergo an interview to give a qualitative description of 
rehabilitation experience upon discharge from outpatient physical therapy or at the 
10-week visit. This interview will entail an open-ended discussion with patients 
about their overall rehabilitation experiences, experiences with home exercises 
(either monitored or unmonitored), experiences with clinic-based workout sessions, 
and expenses incurred during the rehabilitation process. 
 
Additionally, the physical therapists that are using the device with the study 
subjects will be interviewed to describe their experience with patient rehabilitation 
after surgery, and about their experience with the interACTION system. 
 
The physical therapist will also be asked to complete the Clinician Survey, which will 
be administered by a research staff upon discharge of the patient, or a maximum of 
10 weeks (+/- 7 days) after enrollment. All subjects participating in the study will 
be informed that their compliance will be evaluated by their physical therapist at 
this time of discharge, or a maximum of 10 weeks (+/- 7 days) after enrollment. 
 
Statistical Analysis 
 
For the baseline data, continuous variables were compared with the two-sample t-
test and categorical variables were compared with Fisher’s exact test or a chi-
square test.  
 

For the primary outcome (value, ratio of ADLS to cost), the Wilcoxon rank sum test 
was used to compare between the Control Group and interACTION Group. P-Values 
below *p=0.05 were considered statistically significant for all outcomes. For the 
remainder of the cost analyses parameters (weeks of physical therapy, number of 
physical therapy visits, and total cost), a two-sample t-test was used to compare 
between groups.     
 
For other clinical outcomes data, if the distribution was normal at each time point, 
then a repeated measures ANOVA was used. A repeated measures ANOVA was 
used to compare difference between groups for the ADLS, Passive ROM (flexion), 
and Active ROM (flexion). Otherwise, if some time points had normal data and 
others did not then a two-sample t-test was used for normally distributed data and 
the Wilcoxon rank sum test was used for non-normally distributed data.  
 
For the functional performance tests that were assessed at the 5- and 10-week 
visits, a z-score (or standard score) was used to calculate a cumulative score for 
the Six-minute Walk Test (distance in feet), Stair Climb Test (time divided by 
steps), TUG (time), and Surgical Unilateral Balance (time). The z scores are the 
average of the z scores for each of the functional tasks.  On average, the z scores 
are close to zero, meaning that the overall individuals within the group, the scores 
for each subject are not different than the mean score across all subjects. 
Differences between the cumulative z-scores were assessed using a two-sample t-
test.  
 
Recruitment Methods 
 
Recruitment will be primarily done through UPP/CMI Orthopaedic Surgery clinics, 
which routinely care for patients that have undergone TKA. Patients will be 
identified through physicians who will be the primary medical provider in their 
perioperative care. Prior to the patient's first outpatient physical therapy visit, the 
study’s research coordinator or research assistant will screen these patients, using 
the provided screening form, for inclusion/exclusion criteria and enroll/randomize 
those who meet the study’s parameters. Subjects will not be recruited from skilled 
nursing facilities. 
 
Recruitment flyers for the study will be made available at Orthopaedic Clinics and 
also at the Physical Therapist Outpatient Clinics. The flyer will be used to give 
potential patients information about the study and to enable them to contact us if 
they would like to participate. Potential patients may also be given flyers if they 
desire, so that they may have the contact information for the study in the event 
that the potential patient has any questions or concerns regarding the study. 
 
Inclusion criteria 
 
Males and females between 40 and 80 years of age that have undergone primary 
unilateral TKA who have been referred for post-operative outpatient physical 
therapy will be eligible to participate in this study. Additionally, eligible subjects 
also need to be able to perform pre-defined exercises that they would normally 

perform in a physical rehabilitation program. 
 
The Physical therapists that will be asked to complete the Clinician Survey must 
have a patient participating in the study to be considered eligible. 
 
Exclusion Criteria 
 
• 
Individuals outside the aforementioned age range (Adults <40 or >80 years 
of age) 
• 
Patients with BMI >40 at the time of surgery (shown to predict poorer 
outcomes) 
• 
Individuals who are not free of any co-disability or comorbidity that would 
specifically impede, disallow, or otherwise hinder performance of 
rehabilitation exercises 
• 
Individuals who cannot physically receive or understand audio and visual 
feedback from the joint motion tracking system during or after performance 
of rehabilitation exercises. 
 
This information will be acquired through the initial patient screening questionnaire 
given to potential participants during the recruitment period. These participants will 
be interviewed about their ability to use electronic data in the form of audiovisual 
feedback, about existing or pre-existing conditions that could negatively influence 
rehabilitation measures outlined in this study, and patients will be made aware that 
assistive devices can be used during the collection of all outcome measures.  
 
The motion tracking sensors utilized in this study contain a wireless Bluetooth 
module that has been approved by the FCC and will not interfere with devices such 
as pacemakers, defibrillators, or other indwelling devices and therefore these 
patient’s will not be specifically excluded. 
 
Informed consent will be obtained after the screening procedures have been 
performed, but prior to performing any of the research interventions/interactions. 
The information obtained during screening is not of a sensitive nature and will only 
be used to determine if the subject is eligible for full participation in the study. 
 
Participation in this study is completely voluntary. An investigator will go over the 
consent form with each participant who will then have the opportunity to ask 
questions and decide to participate. There is no possibility of coercion, as coercion 
to enroll in a research study would not depend on the research staff providing 
clinical care. Participation in this study does not influence current or future clinical 
care the participant may be undergoing. 
 
Risks 
 
Patients will perform a standard rehabilitation while wearing IMU motion-tracking 
sensors. A software application running on a tablet will wirelessly collect sensor 
data, display live motion data to guide patient performance of exercise tasks, and 
send performance data to servers for online review by the subject’s physical 

therapist. As these are standard rehabilitation exercises, there is no increased risk 
of pain or injury in performing these activities compared to the current standard 
method of performing the exercises. There is no risk of impaired rehabilitation due 
to decreased supervision. The use of IMU motion-tracking sensors poses no likely 
increased risk of physical or mental pain, or distress to the study subjects. There is 
no risk to the patients or others in their household of interference with in-dwelling 
electronic devices such as pacemakers or defibrillators. 
 
Exercise data will be stored on both the tablet device and also transmitted during 
participant session. This data is de-identified, and the device is password protected 
using the device’s native security. The data will be encrypted via SSL during 
transmission to the Microsoft Azure Cloud server, and also when accessing that 
server from Pitt’s internal servers.  
 
Data sharing was not identified or planned in this version, including contacts, texts, 
and geo-location information. As mentioned before, to prevent interception of 
exercise data, Exercise data will be stored on both the tablet device and 
transmitted during participant session. This data is de-identified, and the device is 
password protected using the device’s native security. The data will be encrypted 
via SSL during transmission to the Microsoft Azure Cloud server, and when 
accessing that server from Pitt’s internal servers. 
 
The most likely infrequent risk to the subject may be discomfort from wearing the 
sensors as well as potential spillage of water/fluids on the device which could 
interfere with its functioning; however, there is no risk of electrical shock if the 
device gets wet. This device is designed to be comfortable to wear and is based on 
commonly used, commercially available body straps, and will come with usage 
precautions. Some subjects may also experience mild skin irritation from sweat 
build-up where the straps are worn. Patients will be able to communicate with their 
therapists in weekly visits or by phone regarding painful events or difficulties with 
exercise. 
 
Participants will perform several different strength tests. Risks of injury will be 
minimized by allowing adequate time for warm-up, stretching, and familiarization 
with the task. Qualified individuals will administer the tests. Participants will be 
closely monitored by a member of the study staff. In the event that the participant 
needs first aid treatment, a certified athletic trainer, physical therapist, or 
orthopaedic surgeon will administer the appropriate care. 
 
Participant confidentiality will be maintained at all times. All records will be assigned 
a case number. Information collected in this study will be stored in a locked file 
cabinet in a secure office and will be accessible only to the research staff. Electronic 
files will be stored on the UPMC and/or Pitt secure networks behind the firewall. 
Subjects will not be identified in any publications or presentation of the research 
results. 
 
Potential Benefits 
 

This study aims to increase knowledge related to use of the interACTION device to 
supplement post-operative rehabilitation after TKA. If the interACTION device leads 
to improved post-operative outcomes, patients in the future would benefit from use 
of the device to supplement their post-operative rehabilitation program. If 
beneficial, use of the interACTION device would result lead to the same or better 
outcomes with fewer in-clinic physical therapy visits, thus improving the value of 
care with lowered healthcare costs and expenditures.