Monitoring of Hip Joint Forces and Physical Activity after Total Hip Replacement by an Integrated Piezoelectric Element

Round 1

Reviewer 1 Report

see attached

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper (technologies-2897410)  presents the monitoring of hip joint forces and physical activity after total hip replacement by an integrated piezoelectric element. A piezoelectric energy harvesting system integrated into the total hip stem was used to determine the resultant hip joint forces in various everyday activities.

Major revisions are recommended, and the article merits publication after addressing the following comments: 

• What is the significance and novelty of this work? More details should be provided to clarify it. There are several previous works done with piezoelectric for hip and knee implants.  
• What is the significance of the results? What are the benefits/disadvantages of piezoelectric over other transduction mechanisms (e.g., triboelectric, electromagnetic...) to be used in this health monitoring?
• In Figure 1, it is not very clear where these piezoelectric were placed on the hip implant. It would be better to have a zoomed picture that shows exactly the location of the piezoelectric sensors. Also, what is the reason behind attaching them at this specific location and not other locations such as the femoral head for example. Does changing the location will change the results?
• It is stated (pg. 5), “The curves of the calculated forces are very similar to the curves of the forces applied to the THR.” Even though the results are close to each other, but there should be an explanation for the distraction between the results from the actual forces on implant and the calculated from the piezoin Figure 2.b? What is the reason for the shift between the peaks of the actual applied force and the generated voltage peaks in Figure 2.a?
• At the level of presentation, if the manuscript is printed in black and white colors, the reader will not be able to differentiate between any multiple lines in the same figures. Therefore, the legends and the plot must be revised and replotted using different line dashes and markers. For example, Fig.2 and Fig.2 in the appendix.
• The Confusion Matrix presented in Fig.6 wasn’t clear to me, I believe there must be more discussion provided regarding this figure.
• The authors used a digital oscilloscope to measure the output voltage. For accurate measurements, the internal impedance of the measuring device should be high enough. While the reported internal resistance is 1Mohm. Is this value high enough? How can this affect the accuracy of the measurements reported in this study?
• The authors reported the resistor values used in the study with a fixed resistance of 10101 Ohm. What was the reason behind this selection of resistance value?
• Proofread is recommended to improve the article.

Proofreading is recommended. 

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have adequately addressed the comments of the original review and the paper is now much improved.  My only remaining comment is to provide a few additional details regarding exactly what dataset was used to compute the mean and standard deviation for the results shown in Figure 2 and Appendix A (this was Comment 7 in the original review).  In the revision, the authors state that the augmented force data is used, however additional details can be provided.  For example, it is still unclear if this is a single cycle taken from each patient?  Multiple cycles from each patient?  Only certain patients?  Only certain cycles?  I will accept the paper in present form, but suggest the authors add a few more details before final publication.

Reviewer 2 Report

The authors responded to all my comments, and the manuscript looks good for publication.