Analysis of a Motocross Knee Brace: From the Real Model to the Numerical Finite Element Model via 3D Scanning and Reverse Engineering

Round 1

Reviewer 1 Report

The article is devoted to modelling the load on the knee joint and the influence of the kneecap on the distribution of shock load.

In this article, you are modelling the landing condition after a jump, but when modelling the reaction of the knee to a jump, it is not enough to consider only the weight, impact speed, and height of the jump. Why does your modelling not take into account the influence of ligaments, various muscle groups, meniscus, because it is between these elements that the load is distributed. It is the injuries of the meniscus and ligaments that you have listed in the introduction, but why then do you not take them into account in the modelling? Modelling is oversimplified. The simulation results are not confirmed by experimental results in any way. How is the load applied?

There is a lack of review of existing methods for assessing knee loading.

Some papers:
"An Alternative Mechanism of Non-contact Anterior Cruciate Ligament Injury During Jump-landing: In-vitro Simulation"

"The Capacity of Generic Musculoskeletal Simulations to Predict Knee Joint Loading Using the CAMS-Knee Datasets"

minor issues:

1. Line 54. "knee bracesare", maybe you mean "knee brace are".

2. Line 90. Add a ref where this picture is from. The gray arrows on gray background seems not clear.

Author Response

Please find the reply in the attached document, thank you.

Author Response File: Author Response.pdf

Reviewer 2 Report

In the article, the authors discuss the possibility of modelling the typical activity of motocross when a motorcyclist is wearing a knee brace and without it by using the finite element method by creating a computational model via 3D scanning and reverse engineering. I think this work is interesting and can be published in this journal. However, the authors should make major revisions to address the listed issues before accepting them.

1.       All the material presented is more like a technical report than a scientific manuscript, especially this related to Chapter 2 (Materials and Methods).

2.       Fig.2 is not informative and incomplete (one arrow is missing) and the block named „Brace 3D scaling" appears to be „Bracket 3D scanning '.

3.       The knee brace scanning procedure is described in detail (although the model not presented was obtained after scanning); however, how the geometric model of the lower extremity was obtained by using 3D scanning and reconstruction from MRI images is described very succinctly, with only a reference to the software it was used. The 3D scanned view of the lower extremity and MRI images are also not presented.

4.       Finite element models are not presented. Present at least the finite element model and boundary conditions for a model with a knee bracket used in the FE analysis.

5.       It is not clear how the connection between Femur and Tibia was modeled in the FEM analysis.

6.       It is not clear how the elements of the knee bracket are connected in the FEM analysis.

7.       An impact velocity of 9.9 m/s was chosen. How calculated this value and what duration of impact?

8.       In line 205 it states: „The 'end time' of the simulations was imposed at 0.001 seconds”. How is this value chosen? The maximum displacement may not be the greatest at this point in time.

9.       It would be interesting to see how the distance varies between the Tibia and Femur changes after impact.

 

10.   The conclusions are not entirely correct or informative. It is more like a summary of the manuscript than a conclusion of this work.

Author Response

Please find the reply in the attached document, thank you.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper describes the path from the human body part to the mechanical calculation model very well. The individual work steps and difficulties in converting the MRI data and the optical scan data of the individual parts of the knee support. The details of the acquisition and processing of the scan data are described comprehensively, which is very helpful for other working groups that have similar tasks.

The mention of the names of all the tools used could be reduced somewhat in the context of a scientifically neutral presentation. The same applies to the direct hyperlink to the manufacturer's website, which even appears twice in the text. Even if the manufacturer has supported the research with hardware, such a reference can be placed in a footnote or in the appendix.

The processing and creation of the FE network is also well documented. The elementation of the bones is very good and uniform. The calculation of the movement by means of explicit dynamics is very computationally time-intensive. It is questionable whether a quasi-static analysis is not more effective, especially since the viscous properties of the components are not really known.

In the evaluation, the displacement components for both cases without and with knee brace were evaluated in each direction. The vector sum of the displacement would certainly also be sufficient; instead, the strains and stresses would be interesting. Or the contact pressure in the knee joint itself. A graphical representation of the maximum stress and contact pressure as a function of displacement or load for both variants would be helpful here.

The material modelling as a non-linear material with elastic-plastic components can improve the calculation of stresses in future investigations, although the determination of these material parameters is difficult for organic materials.

 

Author Response

Please find the reply in the attached document, thank you.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors took into account all the comments and significantly reworked the manuscript. The introduction, discussion and conclusion sections look much better. In the introduction, an overview of the subject area was added, and in the discussion and conclusions, the results obtained are presented much more clearly, novelty is indicated, and numerical estimates of the results are described. In general, the article is almost ready for publication, however there are a few small errors in the text, check it please:

1)According to the rules for formatting text in articles, first put the references before the dot. (Line 34,36,42,54,83,285,362,401);
2)Line 54,420: [5 et al] what is it mean? Should be last name here "Withrow et al.";
3) 12 and 13 references are same;

Author Response

please refer to the attached document, thank you.

Author Response File: Author Response.pdf

Reviewer 2 Report

1.       Finite element models still are not presented. It is not clear how the connection in bracket assembly elements was modeled in the FEM analysis (Fig. 3 (c)).

2.       The newly presented images Fig. 7, Fig. 8 and Fig. 9 do not indicate the location of the maximum equivalent von Mises stress value.

3.       The maximum equivalent von Mises stress value in Fig. 7, Fig. 8, and Fig. 9 is the above tensile ultimate strength limit of the femur and tibia. How can this be explained?

 

4.       Looking at the calculation results, it can be seen that the difference between the version with the bracket and without the bracket is very small. How can this be explained?

Author Response

please refer to the attached document, thank you.

Author Response File: Author Response.pdf