Feasibility and Effect of a Wearable Motion Sensor Device in Facilitating In-Home Rehabilitation Program in Patients after Total Knee Arthroplasty: A Preliminary Study

Question 1:

Please review the punctuation/spaces after/before the references and also the punctuation in all sections of the paper. There are paragraphs without a final period. Some of the captions of tables have a final period, and others do not. In conclusion, one of the paragraphs has two final periods.

Reply 1:

We really apologize for our mistakes on the presentation of our manuscript. Great thanks for reviewer’s correction. All the mistakes have been corrected.

Question 2:

Citations must be placed before the final punctuation mark in a sentence. Please review the position of all citations

Reply 2:

Thanks for reviewer’s correction. All the mistakes have been corrected.

Question 3:

At the end of section “Introduction”, the authors should provide information about the organization of the paper.

Reply 3:

Thanks for reviewer’s suggestions. The information about the organization was added in the revised manuscript.

Revised text:

1. Introduction (line 93-99)

“The remainder of this paper is organized as follows. Section 2 presents the materials and methods including the design of the MSD and mobile apps, the study protocols for: the reliability of knee mobility measurements using the MSD and the feasibility of using the MSD for the post-TKA in-home rehabilitation. Section 3 provides our preliminary results and the user experience of the MSD design from the participants. Section 4 discusses the effect and clinical value of the MSD and the limitations in this study. Lastly, conclusions are presented in Section 5.”

Question 4:

The authors should include a section for the state of the art.

Reply 4:

Thanks for reviewer’s valuable suggestion. We rewrote the paragraph in the section of Introduction in order to further introduce the state-of-the-art in this study. Hope our revision could reach the reviewer’s request.

Revised text:

1. Introduction (line 64-89)

“Techniques for detecting body motions could be employed to monitor and rehabilitate disabled patients, offering independent training that has advantages over traditional rehabilitation services [15]. Inertial measurement units (IMUs), including accelerometers and gyroscopes, have been extensively used in technology-assisted rehabilitation, with sufficient accuracy [16-18]. The IMUs-based motion tracking systems, which can be used to reconstruct the position or the orientation of the body they are attached to, have advantage of cost-effectiveness and wearability, allowing for long-lasting tracking of the user motion in situated environments [19]. In our previous study, we developed a wearable motion sensor device (MSD) utilizing the wearable IMU-based sensors to trace the shoulder angular motion on the application of in assisting in-home shoulder exercise for patients with adhesive capsulitis [20]. In addition, the design of the MSD was integrated with interactive mobile apps through wireless telecommunication technologyto increase patient–provider interaction, thereby supporting the feasibility of image- and sensor-based telerehabilitation in treatment of adhesive capsulitis. Our results demonstrated preliminary success in increasing patients’ adherence to daily rehabilitation programs, which facilitated shoulder functional recovery. …..

Focusing on the potential benefits of MSD in the post-TKA telerehabilitation scenario, this study replicated the previous experience of using the MSD for treating adhesive capsulitis to verify the feasibility of an MSD-based treatment model in assisting patients with home-based exercises after TKA. The application of the MSD in this study, which contained two wearable IMU-based sensors to trace the knee angular motion and was integrated with interactive mobile apps designed forpatients and physiotherapists to respectively follow and monitor in-home exercise progress, was anticipated to improving patient compliance with post-TKA rehabilitation exercises. …..”

Question 5:

All figures and tables should appear after the first reference on the text. Tables 1 and 2 appear before.

Reply 5:

Thanks for reviewer’s correction. The sites of the tables in the manuscript have been rearranged.

Question 6:

Section conclusion is small. It should be extended to include future directions (some parts of the section Discussion should be moved to this section).

Reply 6:

Thanks for reviewer’s suggestion. We have moved parts of description on the future application for the MSD use from the section of Discussion to Conclusions.

Revised text:

5. Conclusion (line 491-495)

“MSD-assisted home-based rehabilitation following TKA…, which demonstrates the feasibility of the use of MSD in telerehabilitation and has crucial implications for patients and health systems. Future investigations on the usability, cost-effectiveness, and treatment efficacy of the MSD in telerehabilitation in large patient cohorts are warranted to demonstrate the viability of the MSD in real-world environments. However, the widespread use of the MSD in telerehabilitation for various musculoskeletal disorders is expected once the technology is fine tuned.”

Question 7:

Some technical details should be better explained like the algorithm that was used to convert raw data from the accelerometer and gyroscope into a quaternion. Include the pseudo-code.

Reply 7:

Thanks for reviewer’s suggestion. The algorithm was added in the revised manuscript and pseudo-code was added in the Appendix 3.

Revised text:

2. Materials and Methods

2.1.1. Wearable IMU-based sensors (line129-138)

“InvenSense’s built-in library was utilized to setup the algorithm (https://x-io.co.uk/open-source-imu-and-ahrs-algorithms/). The fusing algorithm combined gyroscope and accelerometer measurements into a single measurement of orientation as a quaternion by drifting in the yaw component of orientation only. The application could reset the drift in yaw by setting the yaw to a specified angle at any time. The algorithm also contained functions for converting this quaternion into a rotation matrix and Euler angles. In addition, the algorithm provided a measurement of linear acceleration (equal to the accelerometer measurement with the 1 g of gravity removed) and Earth acceleration (a measurement of linear acceleration in the Earth coordinate frame). The example of pseudo-code was provided in Appendix 3.”

Appendix 3: The Example of Pseudo-Code

Question 8:

As the authors state, one of the main limitations of this study is the small sample size, and in fact, this is my major issue. 12 patients were used to test their approach and this number seems insufficient to clearly state the advantage of their approach. If possible, try to include more patients in your study.

Reply 8:

Thanks for reviewer’s questions. Small case number is indeed the major drawback of our study design. However, the value of the study was to offer novel but preliminary results on the feasibility of the use of MSD in implications for post-TKA rehabilitation. We therefore recorded and presented the user experience from the participants in the MAR group, anticipating that this experience may facilitate the future development of MSD in telerehabilitation, especially in the post-TKA telerehabilitation scenario. Further description on the limitation of small case number was added in the revised manuscript. 

In addition, owing to the limitation of small case number which prevent this study from robust conclusion, we further emphasized this study as "preliminary" in the Title and tone down the Conclusion in the revised manuscript.

Revised text:

Title:

“Feasibility and effect of a Wearable Motion Sensor Device in Facilitating In-Home Rehabilitation Program in Patients After Total Knee Arthroplasty: a Preliminary Study”

4.Discussion (line 454-461)

“The main limitations of this study is the small sample size, which prevents this study from robust conclusions on the effectiveness of MSD-assisted home-based rehabilitation for patients following total knee replacement. However, the value of this study was to offer novel but preliminary results on the feasibility of the use of MSD in implications for post-TKA rehabilitation. We therefore recorded and presented the user experience from the participants in the MAR group, anticipating that this experience may facilitate the future development of MSD in telerehabilitation, especially in the post-TKA telerehabilitation scenario.”

5.Conclusion (line 481-486)

“This study proved that wearable IMU-based sensors can be used to trace the knee angular motion with acceptable reliability. In addition, the application of a wearable motion sensor device in combination with interactive mobile apps is promising in the post-TKA telerehabilitation scenario. Although with the major limitation on the small number of participants, this preliminarily study demonstrated that MSD-assisted home-based rehabilitation following TKA is a potential useful treatment model of telerehabilitation because it enhances patient adherence to an in-home exercise program, which improves functional recovery.”

Question 1:

The device is tested on small number of participants. They are suggested to include a larger number of patients.

Reply 1:               

Thanks for reviewer’s questions. Small case number is indeed the major drawback of our study design. However, the value of the study was to offer novel but preliminary results on the feasibility of the use of MSD in implications for post-TKA rehabilitation. We therefore recorded and presented the user experience from the participants in the MAR group, anticipating that this experience may facilitate the future development of MSD in telerehabilitation, especially in the post-TKA telerehabilitation scenario. Further description on the limitation of small case number was added in the revised manuscript. 

In addition, owing to the limitation of small case number which prevent this study from robust conclusion, we further emphasized this study as "preliminary" in the Title and tone down the Conclusion in the revised manuscript.

Revised text:

Title:

“Feasibility and effect of a Wearable Motion Sensor Device in Facilitating In-Home Rehabilitation Program in Patients After Total Knee Arthroplasty: a Preliminary Study”

4.Discussion (line 454-461)

“The main limitations of this study is the small sample size, which prevents this study from robust conclusions on the effectiveness of MSD-assisted home-based rehabilitation for patients following total knee replacement. However, the value of this study was to offer novel but preliminary results on the feasibility of the use of MSD in implications for post-TKA rehabilitation. We therefore recorded and presented the user experience from the participants in the MAR group, anticipating that this experience may facilitate the future development of MSD in telerehabilitation, especially in the post-TKA telerehabilitation scenario.”

5.Conclusion (line 481-486)

“This study proved that wearable IMU-based sensors can be used to trace the knee angular motion with acceptable reliability. In addition, the application of a wearable motion sensor device in combination with interactive mobile apps is promising in the post-TKA telerehabilitation scenario. Although with the major limitation on the small number of participants, this preliminarily study demonstrated that MSD-assisted home-based rehabilitation following TKA is a potential useful treatment model of telerehabilitation because it enhances patient adherence to an in-home exercise program, which improves functional recovery.”

Question 2:

The Algorithm used for processing raw signal is unclear.

Reply 2:

Thanks for reviewer’s suggestion. The algorithm was added in the revised manuscript and pseudo-code was also added in the Appendix 3.

Revised text:

2. Materials and Methods

2.1.1. Wearable IMU-based sensors (line129-138)

“InvenSense’s built-in library was utilized to setup the algorithm (https://x-io.co.uk/open-source-imu-and-ahrs-algorithms/). The fusing algorithm combined gyroscope and accelerometer measurements into a single measurement of orientation as a quaternion by drifting in the yaw component of orientation only. The application could reset the drift in yaw by setting the yaw to a specified angle at any time. The algorithm also contained functions for converting this quaternion into a rotation matrix and Euler angles. In addition, the algorithm provided a measurement of linear acceleration (equal to the accelerometer measurement with the 1 g of gravity removed) and Earth acceleration (a measurement of linear acceleration in the Earth coordinate frame). The example of pseudo-code was provided in Appendix 3.”

Appendix 3: The Example of Pseudo-Code

Question 3:

How do the App measure the angle of knee flexion and extension?

Reply 3:

Thanks for reviewer’s question. As the descriptions in section of Materials and Methods (2.1.1. Wearable IMU-based sensors; line 116-121), The initial calibration process involved placing the sensor on a horizontal fixture to measure the offset for each axis and to eliminate nonzero deviations. The sensors on the thigh served as a reference point, enabling raw data from the sensor on the proximal tibia to be used to construct a quaternion using the algorithm; thus, the relative angle changes on the knee joint could be converted into a structure based on the motion of the knee. In this way, we could measure the maximal flexion and extension of the targeted knee. 

Question 1:

I would advise changing the title to emphasize "feasibility" only or to call the effects "preliminary" (given the extremely small group sizes).

Reply 1: 

Thanks for reviewer’s suggestion. We have revised the title as: “Feasibility and effect of a Wearable Motion Sensor Device in Facilitating In-Home Rehabilitation Program in Patients After Total Knee Arthroplasty: a Preliminary Study”

Question 2:

ll. 58: The data situation for an increase in PA after TKA is indeed poor, but the methodological problems in this assessment should also be mentioned. in particular, the large national differences in the extent of rehabilitation measures granted (from several weeks of inpatient care to completely self-reliant) and the different study time points make conclusive statements difficult.

Reply 2: 

Thanks for reviewer’s valuable suggestions. We agreed with the limitations of methodological problems in assessment. Further descriptions on this statement was added in our revised manuscript.

Revised text:

4.Discussion (line 461-464)

“Second, owing to the large national differences on the post-TKA rehabilitation protocol, the protocol used in this trial including the exercise contents, the different study time points and the short follow-up period may exist potential bias resulting in difficulty in making conclusive statements.”

Question 3:

ll. 188: Why do you describe the group(s) (MAR | HE) as over 40 when most of the participants must have been over 60 (cf. table 1 - Please correct the font size in the header of table 2).

Reply 3: 

Thanks for reviewer’s questions. Because this is a prospective study design, the enrollment criteria was initially set for the patients aged over 40 years. We intended to enroll younger patients who may be supposed to familiar with the App use. However, after the enrollment began, indeed, all the enrolled patients was aged over 60 years as reviewer mentioning.

We have revised the description in the manuscript and changed the font size in the header of table 2.

Revised text:

2. Materials and Methods  (line 212)

“ A total of 12 patients aged over 60 years who had received…”

Question 4:

l.188-196: Since data on patients' pain were collected (VAS), information on analgesic use would also be helpful.

Reply 4: 

Thanks for reviewer’s suggestion. We apologize for failure in recording the analgesic use in our study design. We added this as one of our limitation in our revised manuscript.

Revised text:

4.Discussion (line 464-466)

“Third, we only recorded the post-operative pain score during follow-ups without documenting the analgesic use, which may mask the influence of pain on patient adherence to training program.”

Question 5:

A general question: why did you compare the MAR and HE group and not 2 MAR groups with the patients who already have experience with apps (i) and those patients who do not have this very experience yet (ii)? This would be a much more important research question in my view. 

Reply 5:

Thank for your valuable question. In our study design, we intended to directly compare the effectiveness of novel MAR training with the conventional HE which is generally adopted for post-TKA training in most countries, or at least in Taiwan. In addition, to enhance the compliance for the exercise in rehabilitation after TKA is the clinical unmet need as we have mentioned in the Introduction. Therefore, direct comparison between MAR and HE was supposed to prove our hypothesis on the effect of MAR on enhancing patient adherence to exercise program.

However, we really appreciate reviewer’s point of view on the influence of apps experience among the participants. We wish we may soon kick off new study design on this interesting issue, once new study project is ready and the equipment has been fine-tuned. 

Question 6:

ll.355: Here you also summarize the first (technical-methodical) part of your study - why then not also in the Conclusions (ll.456)?

Reply 6:

Thanks for reviewer’s suggestion. We added more descriptions in the conclusion.

Revised text:

5.Conclusion (line 481-482)

“This study proved that wearable IMU-based sensors can be used to trace the knee angular motion with acceptable reliability. In addition, the application of a wearable motion sensor….”

Question 7:

Please tone down the statements in the Conclusions to make it clear that these are preliminary results of a pilot study. 

Reply 7:

Great thanks for reviewer’s suggestion. We have tried to tone down the text in the conclusion.

Revised text:

5.Conclusion (line 482-485)

“The application of a wearable motion sensor device in combination with interactive mobile apps is promising in the post-TKA telerehabilitation scenario. Although with the major limitation on the small number of participants, this preliminarily study demonstrated that MSD-assisted home-based rehabilitation following TKA is a potential useful treatment model of telerehabilitation because it enhances patient adherence to an in-home exercise program, which improves functional recovery.”

Question 8:

Typos:

Table 2: Please check font sizes and spacing

l.420: "over 10"

l.445: "[36] The"

l.462: "systems."

Reply 8:

Thanks for reviewer’s correction. All the mistakes have been corrected.