System for Evaluation and Compensation of Leg Length Discrepancy for Human Body Balancing

Round 1

Reviewer 1 Report

This study tries to construct a system to detect leg length difference between two sides of body, and the effort is impressed. However, there are some concerns from me to be clarified.

Major concerns:

1)      Has the system been valuated with other measurement means, e.g. MRI, manual measurements? Only when we know real leg lengths, can we know if this system works..  

2)      As we know, a lot of reasons could affect the GRFs from two feet when standing, e.g. use of more dominated/non-dominated side force, asymmetrical spine/pelvis. This study should have excluded other reasons.

Author Response

Response to Reviewer 1 Comments

We would like to express our gratitude for valuable comments of Editor and anonymous reviewers.

Point 1: Has the system been valuated with other measurement means, e.g. MRI, manual measurements? Only when we know real leg lengths, can we know if this system works. 


As we stated in section 5.4.3 the system has been validated on a healthy volunteer by using standing on the blocks method and by using a tape measure. Further validation has been done on the same healthy volunteer in a way that LLD was simulated and our system successfully compensated discrepancy which corresponds with standing on the block method. At the moment our system is on initial clinical trials and thorough validation is undertaken by using standing on the block and tape measure methods.

Point 2: As we know, a lot of reasons could affect the GRFs from two feet when standing, e.g. use of more dominated/non-dominated side force, asymmetrical spine/pelvis. This study should have excluded other reasons.

Thank you for your observation. We are aware of the various effects that can influence GRF. That is exactly the reason for the inclusion of two cameras (Fig. 4) as a part of the proposed system. The front and the side cameras track referent anatomical points (presented as red dots in Fig. 2) and physician is notified in case of asymmetrical spine/pelvis (this situation is described in 4.1.2 Scenario 2).

Kind regards,

Authors

Reviewer 2 Report

Dear authors, the manuscript deals with an interesting approach to identify leg length discrepancies based on the COM position / weight distribution between both feet. The COM can be moved in the "right" position based on changing the heights of your implemented force plates. The manuscript is well structured and reflects the quality of the previous research conducted from the group. While I think your machine is really interesting and well validated (in a mathematical model and in healthy adults) a test with real patients is unfortunately lacking. It would be interesting to see (in future works) how patients react to the system and how the performance actually is to traditional methods. Again, this can be tested in the future. 

The machine is great, without a doubt, however what are the practical implications? Will each Podologist buy one of your machines to improve the insole prescription? 

What about the functional leg length discrepancy? There have been studies showing that the static measurement is of limited interest as humans tend to move rather than being static. A whole branch of literature is reviewing the influence of leg length discrepancy with a special focus on surgery or orthotics. Maybe you can emphasize in the introduction and conclusion why your device could help with this regard. (see https://www.ncbi.nlm.nih.gov/pubmed/24703513 and https://www.ncbi.nlm.nih.gov/pubmed/28793888). As per the guidelines your research should be as much "open" as possible for other researchers to reproduce. May you think of a way to provide the Simulink Model or other to the very passionate readers. Overall a great manuscript with the only downfall that you have not measured any patients. Please make sure that you evolve the clinical implications and explain why/how your research may improve the orthotics or medical care in general.
Well done, 
Clint Hansen

Author Response

Response to Reviewer 2 Comments 

We would like to express our gratitude to valuable comments of Editor and anonymous reviewers.

Point 1: While I think your machine is really interesting and well validated (in a mathematical model and in healthy adults) a test with real patients is unfortunately lacking. It would be interesting to see (in future works) how patients react to the system and how the performance actually is to traditional methods. Again, this can be tested in the future. 


Response 1: Thank you for your nice words. We agree with you that tests on real patients would increase a quality of the paper, however, clinical validation requires substantial time (12 to 24 months). We decided to share our current results with broad scientific community as simulations and laboratory experiments confirmed quality of the system and we received positive feedback from several practitioners that are willing to test the proposed method on real patients. Furthermore, based on promising preliminary results we received funds for the design and construction of the system under Proof-of-Concept program from Croatian agency HAMAG BICRO. At the moment clinical trials on 35 patients already started and we hope to have clinical results in the next 18 months.

Point 2: The machine is great, without a doubt, however what are the practical implications? Will each Podologist buy one of your machines to improve the insole prescription?

Response 2: Thank you for nice words. As we stated in previous response, the system is already used by practitioners and in the next 18 months we expect to receive valuable feedback from test on real patients. The main purpose of the system is exactly as you stated – improvement of the quality for shoe lift and shoe insoles prescriptions. Moreover, in case of clinical treatments (slowing down or stopping the growth of the longer leg, shortening the longer leg and lengthening the shorter leg) practitioners will have opportunity to track the status of a patient, validate the quality of surgical treatment and take necessery steps in order to improve the quality of life for a person suffering LLD.

Point 3: What about the functional leg length discrepancy?

Response 3: Functional or apparent LLD is defined as a mechanical change in the lower extremities, such as varus and valgus deformities of knees and feet, as well as scoliosis of the spine. Even though our system allows for detection of functional LLD, in this paper we focused on anatomical LLD and prepared the system for clinical trials on this particular problem. In our future research we plan to investigate functional LLD by determining mathematical models and methods for changing roll and pitch of moving platforms (angles α and β in Equ. (7)), thus allowing practitioners to determine status of functional LLD.

Point 4: There have been studies showing that the static measurement is of limited interest as humans tend to move rather than being static. A whole branch of literature is reviewing the influence of leg length discrepancy with a special focus on surgery or orthotics. Maybe you can emphasize in the introduction and conclusion why your device could help with this regard. (see https://www.ncbi.nlm.nih.gov/pubmed/24703513 and https://www.ncbi.nlm.nih.gov/pubmed/28793888).

Response 4: The mechanical design of the proposed system is based on parallel manipulators that provide a firm ground for trajectory planning and measurement of walk dynamics. As we stated in previous response our focused was on anatomical LLD. Research on LLD is a very broad field and it is very challenging to include all possible situations in a single paper. The results that we presented herein are the first step in thorough investigation of LLD that we plan to take in years to come.

Point 5: As per the guidelines your research should be as much "open" as possible for other researchers to reproduce. May you think of a way to provide the Simulink Model or other to the very passionate readers.

Response 5: In case our paper gets accepted for publication we plan to share developed Simulink model with research community through ResearchGate.

Point 6: Overall a great manuscript with the only downfall that you have not measured any patients. Please make sure that you evolve the clinical implications and explain why/how your research may improve the orthotics or medical care in general.

Response 6: Thank you for nice words. As we already stated in our response to Point 1 we agree with your statement that the quality of the paper would increase if tests on real patients were included. However, this requires significant time and our intention was to share our promising results with research community as soon as possible. In that way we expect to receive feedback on our work and possibly get more practitioners that are willing to use the proposed system, thus widening the range of clinical tests and acquiring more experience.

Kind regards,

Authors

Round 2

Reviewer 2 Report

Dear authors, 

am not sure what to make of your revision. I dont see any changes to the manuscript... 

Your answers are good but please be so kind to at least try to emphasize on them in the manuscript as other scientists will raise similar questions and it will only improve your manuscript. Emphasize on the previously raised points in your introduction and in the discussion/conclusion and you are good to go... PLease state that the SIMULINK model will be published and maybe already do it for the revision process on https://www.biorxiv.org/ to make sure you will do it ;). 

As for now I will stick to my initial revision as you have not made any changes to the uploaded document. 

Kind regards, 

Clint Hansen

Author Response

Response to Reviewer 2 Comments – (Round 2)

We would like to express our gratitude to valuable comments of Editor and anonymous reviewers.

Changes in the original manuscript, as a response to reviewers' comments, are in red. We emphasized the reviewer's comments in the Introduction and Conclusion.

We shared the Simulink model with the research community through ResearchGate (addition in Point 5 in 1^st response to Reviewer 2). We put the Simulink model in References ([31]).

url: https://www.researchgate.net/publication/333668115_Virtual_Simulation_Model_for_Evaluation_and_Compensation_of_Leg_Length_Discrepancy_for_Human_Body_Balancing

doi: 10.13140/RG.2.2.13399.52644

Kind regards,

Authors

Round 3

Reviewer 2 Report

Well done! Keep up your good work and am looking forward to seeing your patient results!

Clint Hansen