Are Suprapectineal Quadrilateral Surface Buttressing Plates Performances Superior to Traditional Fixation? A Finite Element Analysis

Round 1

Reviewer 1 Report

The paer is very interesting and could be accepted in the present form, I suggest a check of  references 

Author Response

We thank the Reviewer for his/her positive feedback. We have checked and corrected all the references, as suggested.

The authors, January 2021

Reviewer 2 Report

The authors did a stress-strain analysis of two plates to fix acetabular fractures using a finite element method. They used two plates, a new one SQBP with two configurations of screws and the traditional SPP (with one configuration of screws). Some clarifications are needed, but overall the study is acceptable. I would recommend to improve the readability of the text and make the figure clearer. I divide specific comments into major and minor:

 

Major

1. I see that you evaluated stress and strain properties, but how do you evaluate the stability of the plate?
2. Figure 1 is hard to understand. Figures b and c are almost identical.
3. If I am not wrong, SQBP plate has been described, but SPP has not. The only mention was that it is a standard plate. I would recommend to briefly describe SPP better.
4. If I have understood correctly, the screws of the quadrilateral side for SQBP C2 are not attached. So, what is the purpose of this configuration?
5. I would not start a section with a figure. See 2.1.3 and 3.1.1.
6. It is very hard to see any differences within the subfigures of Figure 3. I would highlight the differences, or change the figure to focus on the message.
7. Table 2. What is the readon of using Penta6 for cartilage tissue and Tetra4 for the others?
8. L154-155. What do you mean by this sentence? What do you mean by a shared mesh?
9. L163-165. Was there not loading in the direction perpendicular to the direction of the screw? Why?
10. Figure 5. Why two coordinate systems are used?
11. L187-188. Regarding “z direction describes the compression and traction”, the T-shape fracture has two directions, right? Then, could not compression-traction be in two directions?
12. The text mentions “are located at the pubic tubercle”, but this is not highlighted in the figure.
13. Figure 6. It is weird that the scale is with steps of 16.66 MPa and then the last interval is huge. The reader cannot distinguish the differences among cases. Like Figure 3, please, try another way to present the results (focus on your message).
14. Regarding “a clear reduction of the stresses at the pubic tubercle induced by the bone-plate larger contact is visible,” this is not visible in the Figure.
15. Table 6. Did you try to obtain the results with another mesh? Were the results very different? How dependent are the results from the mesh refinement?
16. Figure 7. Again, it is difficult to see the differences that you want to highlight.
17. Be careful with the use of English. Sentences like in line L230 and L233 are too long. Please, avoid the use of too long subordinate sentences. The same for lines 288-292, or 355-359.
18. Figure 8 a and c. Did you take into account the same number of cells in all cases?
19. Figure 8. X axis of all subfigures is not clear.
20. Figure 8. I think that is not clear the meaning of the three cases. The reader understands T for transverse, and T-sp for T-shape. Then, why are there three sub-cases for each configuration?
21. Figure 8 b and d are not clear without further clearer description.
22. Why 0 %? Would 0 % be expected as optimal?
23. Section 4 is mainly a summary of the results. I would change it to relate your results to other studies. Only [41] and [42] are mentioned. Limitations are also missing.

Minor

1. What do you mean by “anatomical reduction”?
2. L49-50. I think a reference is missing here.
3. I would briefly describe how the “freehand” command works.
4. Ileum or ilium?
5. “obtained” instead of “realized”?
6. Figure 3 caption. “models” instead of “model”?
7. I think that a colon “:” is not the most appropriate here.
8. “Number of” instead of “number or”?
9. “were” instead of “where”?
10. A comma is missing after epsilon_shear.
11. “anther”?
12. “arise” instead of “arises”?
13. What do you mean by “point couples”?
14. “The aim”.
15. “transtectal”? what do you mean?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

This study compares, by means of the finite element method two fixation plates (SQPB and SPP) in two fracture configurations (transverse and T-shaped). The optimisation of internal plating for fractures is a challenging area. Enhanced understanding of how the various fixation options affect the fracture movement is certainly of interest. However, the manuscript lacks full clinical justification for the study motivation and study design.  In particular, two different screw fixation arrangements are presented as modelling cases. However, the clinical justification for these is unclear. In addition, numerical results are directly dependent on modeling assumptions made. In my opinion, these major concerns need to be addressed before the recommendation to be published in Applied Sciences.

Specific comments are described below.

Abstract

Line 29. The authors state that the SBBP may be a valid therapeutic option. More clinical justification and validation is needed to state this conclusion.

Introduction

Line 60. The second objective is more a step towards the real aim of the study: to compare different fixation environments.

Materials and Methods

The internal plates modeled have general geometries. Please do not include patient specific.

Are the three cases considered in the study done clinically? If not, what is the mechanical/study design reason for including them?

Which is the reason behind the different screw lengths used? Please justify further.

The fractures are modeled by deleting elements in the fracture region. It is suggested to mesh after delimiting the fracture region.

Have the authors analyzed the effect on including the cartilage volume on the results? How does it affect to the stress distribution?

Meshing: have the authors made a sensitivity analysis? The mesh seems to be highly homogeneous. Computational costs could have been reduced by making it heterogeneous.

Contact implementation: is the contact between the screws and the bone modeled with a tie contact?

Loading conditions: please justify further the force applied (2032 N)

The strain-based model proposed by Perren does not refer to optimal or acceptable ranges. It states that the strain tolerance is greatest for granulation tissue, intermediate for cartilage, and least for bone. What about the shear strain ranges? Where have them been taken from?

Results:

Most of the mechanobiological models of bone are expressed in terms of strains rather than in stresses. Can the authors justify or validate the stress levels obtained in the bone? How can we know if it is too high of too low?

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

I would like to thank the authors since all comments have been addressed. I have only minor comments, and I consider that after addressing them, it can be published.

1. L73. accurate instead of arcurate?

2. I would say that the tension in the direction perpendicular to the screws would affect the strains. It seems that they have been neglected, and no comment is included. Is there any reason to neglect this effect?

3. I think that the quality of figure 8 (especially b and d) can be improved. Mainly increasing the resolution, and making the lines wider improves.

4. L466. I would add that the resultant external forces have been simplified. No muscles have been considered, only a particular loading condition has been considered, etc.

 

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The authors have responded thoroughly to the previous criticisms in the first review. However, it is of main concern the contact conditions implemented between the screws and the bone. As commented by the authors, both the bone and screws share the mesh and this, of course, directly affects the results predicted by the model. Since the main objective of the work is to compare the stability of different fixation plates, screw-bone contact must be implemented.  Therefore, the paper cannot be published in its current form.

Author Response

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Author Response File: Author Response.pdf

Round 3

Reviewer 3 Report

The authors have put in a lot of work to enhance the manuscript.  However, now the exact contribution of the study has become clear, it has also become clear that it is, in this reviewer's opinion, insufficient to justify a publication in Applied Sciences for several reasons:

• The insufficient novelty of this study.  
• The strong dependence of the results to the modelling assumptions made
• The limited validation of the in silico results  

Author Response

Dear Reviewer,

we are sorry that you did not appreciate our research, however we thank you for the precious and constructive criticisms you addressed to us.

Best regards