Review Reports - Investigating Material Performance in Artificial Ankle Joints: A Biomechanical Study

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

My main concern is the FE values are greatly influenced by the Poisson's ratio value. The value for UHMWPE seems to be higher than what I have seen in the literature. This has the potential to significantly change the results. Please provide the reference for the condition and source of the 0.46 Poisson's ratio reported for the UHMWPE in your study. A secondary concern is that the wear properties of these materials are not mentioned as a variable. Metal on metal or metal on polymer can produce significant wear debris particles that may cause infection, loosening, and ultimately failure of the implant. The authors should address this concern.

Here is the list of my comments.

Page 3 – excellently flammable hot and cold,

I don't understand what this statement is stating. For implants, hopefully the flammability is not an issue.

Page 3 – There are some materials with names that are capitalized and some that are not. Typically, the materials are not capitalized unless starting a sentence or is a proper noun.

Page 4 - Have you considered different polymers that are used in ankle replacements? PEEK and carbon reinforced PEEK are two materials that are on the market and being researched. UHMWPE has a lower wear resistance than PEEK, especially when paired in a joint with metallic components.

Page 4 Table 1 - Can you add the references for where these values were obtained? Young's modulus, Submission Stress, and Tensile strength are usually given as a range due to different finishing conditions (cold-worked, aged, annealed, etc.). Poisson's ratio for UHMWPE seems high. It is usually reported to be 0.32 - 0.40, depending on condition.

Page 4 section 4.2 – Tibial should be lower case t.

Page 9 Table 3 - Significant digits for each section should be the same. For example, all displacement values should have the same number of digits. They should be significant as well. I don't think 0.000001mm is significant with displacement of the ankle. 0.001 or 0.0001 levels should be fine.

Page 11 Table 4 – Same issue as Table 3 with significant digits.

Page 11 last paragraph - To complete this study, the factors of the web together with the conditions of the problem dimensions will be similar to what has been already mentioned above. Did you mean "factors web together"?

Page 12 - An amount of 155.774 HZ By contrast, the values of the total deformity of this item are much higher compared to other researched items 16.36489 mm.

An amount of 155.774 Hz by contrast, the values of the total deformity of this item are much higher compared to other researched items 16.36489 mm. Significant digits 155.74 and 16.36489 should be the same.

Table 5 – significant digits

Page 13 – Table 6 significant digits

Table 7, 8, 9, 10 – significant digits

Page 14 - [mm]2/Hz]) – 2 should be a superscript

Page 16 – You have Elastic Strain and elastic strain - Elastic strain should be lower case unless leading a sentence and consistent throughout the manuscript.

Page 16 – “reaches 4.4484×10 5-2 mm/mm and that the minimal elastic strain is 2.01×10-8 mm/mm.” I'm not sure what this 4.4484×10 5-2 mm/mm value should be. Is it 105 to the negative 2 power? 2.01×10-8 mm/mm, should have -8 superscripted.

Page 16 – “compliance with the force 2000 N,2500 N,3000 N, and 3500 N.” Put a space after the commas.

Comments on the Quality of English Language

There are numerous capitalization errors throughout the paper. There are superscript and subscript errors that need to be corrected.

Author Response

Dear Respected Reviewer,

First of all, we would like to thank you for reading and reviewing our paper.
Major revisions have been made to our manuscript, taking into consideration the following modifications below.

Point 1: Please provide the reference for the condition and source of the 0.46 Poisson's ratio reported for the UHMWPE in your study.

Response 1: : I concur with your perspective on the significance of Poisson’s ratio values, as they can significantly impact results. In our research, we incorporated Poisson’s ratio values for UHMWPE material, drawing upon a comprehensive array of reference studies, including [16, 17].

Point 2: A secondary concern is that the wear properties of these materials are not mentioned as a variable. Metal on metal or metal on polymer can produce significant wear debris particles that may cause infection, loosening, and ultimately failure of the implant.

Response 2: We agree that this is an important property that materials must possess, but this research is concerned with studying mechanical behavior in terms of stresses and displacements on the one hand and vibration frequency on the other hand. In addition, mechanical strength and durability are the most important safety requirements for biomaterials. Under load-bearing conditions, mineral materials appear. Sometimes it is toxic and breaks down due to corrosion and mechanical damage [12]. We will take this topic into consideration in future research work. The reference was added and amended in paragraph 4.

Point 3: Page 3 – excellently flammable hot and cold. For implants, hopefully the flammability is not an issue.

Response 3: The material in question exhibits exceptional features suitable for diverse applications. Originally engineered for medical implanting use, this innovative alloy boasts the unique ability to be shaped through both cold and hot forming processes. With dual design options and remarkable corrosion resistance, it stands as a testament to its versatility and quality. Reference to this material can be found in the cited study [13], which has been seamlessly integrated into our research context.

Point 4: Page 3 – There are some materials with names that are capitalized and some that are not. Typically, the materials are not capitalized unless starting a sentence or is a proper noun.

Response 4: All the mentioned comments regarding the capitalization of material names have been addressed and modified accordingly in the text.

Point 5: Page 4 - Have you considered different polymers that are used in ankle replacements? PEEK and carbon reinforced PEEK are two materials that are on the market and being researched. UHMWPE has a lower wear resistance than PEEK, especially when paired in a joint with metallic components.

Response 5: We concur with your observation, as supported by reference studies highlighting polyethylene's prominence in joint design since inception and its extensive utilization in joint bearings compared to other polymeric materials. This underscores the significance of comprehensively understanding and advancing this material. Additionally, insights gleaned contribute to enhancing our understanding of polyethylene's load-bearing capacity. Furthermore, the article on PEEK, as referenced in [16, 17], has been duly considered for future investigations.

Point 6: Page 4 Table 1 - Can you add the references for where these values were obtained? Young's modulus, Submission Stress, and Tensile strength are usually given as a range due to different finishing conditions (cold-worked, aged, annealed, etc.). Poisson's ratio for UHMWPE seems high. It is usually reported to be 0.32 - 0.40, depending on condition.

Response 6: The references for obtaining these values have been meticulously cited within the text. For Young's modulus, Submission Stress, and Tensile strength, we have accounted for the variations arising from different finishing conditions, including cold-worked, aged, and annealed states. Regarding Poisson's ratio for UHMWPE, the value provided has been sourced from reputable literature in accordance with your observation.

Point 7: Page 4 section 4.2 – Tibial should be lower case t.

Response 7: This matter was adhered to in the text of the research.

Point 8: Page 9 Table 3 - Significant digits for each section should be the same. For example, all displacement values should have the same number of digits. They should be significant as well. I don't think 0.000001mm is significant with displacement of the ankle. 0.001 or 0.0001 levels should be fine.

Response 8: This matter was adhered to in the text of the research, where the answers were taken based on the results of the analysis using the finite elements method, knowing that this value is very small and can be neglected, but it was mentioned in the research to prove the weak effect in this article.

Point 9: Page 11 Table 4 – Same issue as Table 3 with significant digits.

Response 9: This matter was adhered to in the text of the research.

Point 10: Page 11 last paragraph - To complete this study, the factors of the web together with the conditions of the problem dimensions will be similar to what has been already mentioned above. Did you mean "factors web together"?

Response 10: In the study of vibration, identical boundary conditions are applied as those used in the analysis of stresses and displacements. In this revised version of the manuscript, it is clarified in the text as ‘’ To complete this study, the boundary conditions are used similar to what has been previously mentioned above.’’

Point 11: Page 12 - An amount of 155.774 HZ By contrast, the values of the total deformity of this item are much higher compared to other researched items 16.36489 mm. An amount of 155.774 Hz by contrast, the values of the total deformity of this item are much higher compared to other researched items 16.36489 mm. Significant digits 155.74 and 16.36489 should be the same.

Response 11: It's notable that the value is correlated with the hardness of the element and Young's modulus. Moreover, the total deformation and frequency are contingent on both mass and stiffness. We've maintained consistency with numerical data and have adjusted the research text accordingly.

Point 12: Table 5 – significant digits ,;Page 13 – Table 6 significant digits ,;Table 7, 8, 9, 10 – significant digits ,;Page 14 - [mm]2/Hz]) – 2 should be a superscript

Response 12: This matter was adhered to in the text of the research.

Point 13: Page 16 – You have Elastic Strain and elastic strain - Elastic strain should be lower case unless leading a sentence and consistent throughout the manuscript.

Response 13: The formatting within the research text has been revised, ensuring clarity and coherence. This particular value is deemed suitable, as corroborated by reference [3], where it was verified that there are no red flags within the design. This confirmation reassures us of the design's capability to regain its original state even after strength depletion, as highlighted in the reference.

Point 14: Page 16 – “reaches 4.4484×10 5-2 mm/mm and that the minimal elastic strain is 2.01×10-8 mm/mm.” I'm not sure what this 4.4484×10 5-2 mm/mm value should be. Is it 105 to the negative 2 power? 2.01×10-8 mm/mm, should have -8 superscripted.

Response 14: The formatting in the research text has been modified.

Point 15: Page 16 – “compliance with the force 2000 N,2500 N,3000 N, and 3500 N.” Put a space after the commas.

Response 15: The formatting in the research text has been modified.

Point 16: Comments on the Quality of English Language There are numerous capitalization errors throughout the paper. There are superscript and subscript errors that need to be corrected.

Response 16: The formatting in the research text has been modified.

With many thanks for your time and effort.
Kind regards,

Reviewer 2 Report

Comments and Suggestions for Authors

Thank you very much for you interesting manuscript. Please find my comments and suggestions in the review report in below.

In their manuscript, the authors explore biomechanical characteristics and material performance of artificial ankle joints, focusing on a salto-talaris type design. It discusses the importance of ankle joints in human movement and advancements in ankle replacement surgery. The study details human ankle anatomy and describes the design and components of the salto-talaris artificial joint. Comparative analysis validates the designed joint against a benchmark. The study highlights FEA's importance in biomechanics, emphasizing optimal material selection for joint stability and design efficiency, contributing insights for joint replacement technology. Overall, the manuscript demonstrates strong coverage of biomechanical analysis and material characterization in artificial ankle joints. Improvements in language clarity, result interpretation and acknowledgment of limitations would further enhance the manuscript's quality and contribution to the field.

GENERAL

I suggest reworking the language and sentences in the manuscript to improve readability. Here are some aspects which I find would require special attention:

Some sentences in the manuscript appear lengthy and complex, which can make the text challenging to read and understand. Breaking down complex ideas into shorter, more digestible sentences would enhance readability. Focusing on key findings and implications while minimizing unnecessary repetition or overly detailed descriptions would certainly improve the reader’s understanding.

The sentence structure in the material list of the methods section should be revised. Although it just describes the material properties, it is sometime hard to follow the context and seems to be written quickly without giving it any second thought. Here are some examples

Co-Cro-Mo material: “Its major characteristics: are very hard (high flexibility factor) allowing the possibility of narrowing down the skeleton dimensions, having enough connectivity energy between Porcelain and Alloys, and erosion proof..”. The colon appears misplaced. Why would narrowing down the skeleton (I assume the ankle bone is meant by that) speak in favour of this material? If the authors mean that a slim prosthesis design can be achieved with Co-Cor-Mo, they should mention this clearly. Lastly, there is a second full stop.

Titanium alloy material: “It really enjoys distinguishable energy, low flexibility factor, accepts wielding easily, and is open to treatment by temperature.” What is meant by “it enjoys low flexibility factor”, or “it accepts wielding easily”? What does it wield?

In the polymer material section (p.4) the authors state “due to a constellation of features including erosion proof, powerful skeleton, and biological harmony” – why does harmony play a role here? Do they mean bio-compatible?

The following sentence states “It has so long chains.”. The meaning of this sentence and the relation of it to the context is not explained to me.

Section 4.2: the heading says “trio-dimensional” while this is later referred to as “tria-dimensional”.

As such, I recommend a thorough revision of spelling and sentence structure throughout the manuscript. More cohesion and a smoother contextual transition is required here for the reader to be able to follow. While the manuscript covers various aspects of the study comprehensively (especially in the introduction and discussion), there could be improvements in the overall flow and cohesion between sections. Ensuring that each paragraph transitions smoothly to the next would improve the readability and coherence of the manuscript.

INTRODUCTION

Overall, while the introduction provides a foundational understanding of the importance and challenges of ankle joint biomechanics, further clarity on the specific research objectives and their connection to material performance analysis would strengthen the introduction and enhance the coherence of the manuscript. This would help readers better anticipate the content and scope of the study presented in the manuscript. To better link the introduction with the subsequent sections of the manuscript (e.g., materials and methods, results), the introduction could explicitly mention the focus on material performance analysis and how it addresses the identified challenges in ankle joint replacement.

METHODS

While the methods provide a solid overview of the experimental setup, some sections could benefit from additional clarity on specific experimental procedures or steps. Providing more detailed step-by-step instructions could enhance reproducibility and understanding.

RESULTS

Figure 18: I suggest cropping the picture to the ankle design, not showing the program’s menu bar etc.

DISCUSSION/CONCLUSION

While the authors provide good references to other studies and managed to link the discussion to the challenges stated in the introduction, I would welcome to establish a stronger linkage to their results. The manuscript could be improved through a more detailed discussion of how specific results led to a specific conclusion, or how they can be used to address the challenges mentioned in the introduction. This would provide transparency and clarity regarding the reasoning behind each conclusion.

In addition, it would be helpful to include a limitations paragraph addressing the potential impact of any assumptions made in the FE analysis or the limitations associated with the experimental design (and analysis methods).

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The comments on the quality of English are included in the GENERAL section of my review report.

Author Response

Dear Respected Reviewer,

First of all, we would like to thank you for reading and reviewing our paper.
Major revisions have been made to our manuscript, taking into consideration the following modifications below.

Point 1: Some sentences in the manuscript appear lengthy and complex, which can make the text challenging to read and understand. Breaking down complex ideas into shorter, more digestible sentences would enhance readability. Focusing on key findings and implications while minimizing unnecessary repetition or overly detailed descriptions would certainly improve the reader’s understanding.

Response 1: The text was indeed revised to address this matter and underwent formatting adjustments.

Point 2: The sentence structure in the material list of the methods section should be revised. Although it just describes the material properties, it is sometime hard to follow the context and seems to be written quickly without giving it any second thought. Here are some examples Co-Cro-Mo material: “Its major characteristics: are very hard (high flexibility factor) allowing the possibility of narrowing down the skeleton dimensions, having enough connectivity energy between Porcelain and Alloys, and erosion proof..”. The colon appears misplaced. Why would narrowing down the skeleton (I assume the ankle bone is meant by that) speak in favour of this material? If the authors mean that a slim prosthesis design can be achieved with Co-Cor-Mo, they should mention this clearly. Lastly, there is a second full stop.

Response 2: I concur with your point. Each material's characteristics were succinctly elucidated to facilitate identification of internal materials in the research and delineate their respective features. This aids in determining the structural dimensions, particularly in terms of bone corrosion, facilitating relaxation. The text has been appropriately revised to emphasize the material's features and significance.

Point 3: Titanium alloy material: “It really enjoys distinguishable energy, low flexibility factor, accepts wielding easily, and is open to treatment by temperature.” What is meant by “it enjoys low flexibility factor”, or “it accepts wielding easily”? What does it wield?

Response 3: It has been modified to the term ‘’malleability’’. This property facilitates the formation and manufacturing of various biomechanical shapes, rendering it resistant to brittle fractures under loading and preventing shattering. The text has been revised accordingly, including necessary formatting adjustments.

Point 4: In the polymer material section (p.4) the authors state “due to a constellation of features including erosion proof, powerful skeleton, and biological harmony” – why does harmony play a role here? Do they mean bio-compatible?

Response 4: This term refers to biocompatibility, a crucial aspect for any implant placed within the human body. Biocompatible materials are designed to prevent inflammatory reactions or toxicity. In the research, this term has been appropriately modified. It entails incorporating various features into the material during design and sterilization processes to ensure compatibility with the human body. Reference [14] has been included in the text to support this assertion.

Point 5: The following sentence states “It has so long chains.”. The meaning of this sentence and the relation of it to the context is not explained to me.

Response 5: That is, this can be explained based on the structural composition, as it is characterized by very long polymer chains that help to transfer the load more efficiently through the basic polymeric chains, which are the characteristics of the material in terms of features and through strengthening interactions between molecules, This leads to obtaining a very durable material, which gives us excellent stress results. Compared with the studied materials [14].

Point 6: Section 4.2: the heading says “trio-dimensional” while this is later referred to as “tria-dimensional”.

Response 6 : The text was indeed revised to address this matter and underwent formatting adjustments.

Point 7: As such, I recommend a thorough revision of spelling and sentence structure throughout the manuscript. More cohesion and a smoother contextual transition is required here for the reader to be able to follow. While the manuscript covers various aspects of the study comprehensively (especially in the introduction and discussion), there could be improvements in the overall flow and cohesion between sections. Ensuring that each paragraph transitions smoothly to the next would improve the readability and coherence of the manuscript.

Response 7 : We acknowledge the need for a comprehensive revision, focusing on spelling, sentence structure, cohesion, and contextual transitions throughout the manuscript. Enhancing the flow and cohesion between sections is essential to ensure readers can seamlessly follow the content. While the manuscript effectively covers diverse aspects of the study, particularly in the introduction and discussion sections, we recognize the opportunity for improvement in the overall flow and coherence. We prioritized refining the transitions between paragraphs to enhance readability and coherence.

Point 8: Overall, while the introduction provides a foundational understanding of the importance and challenges of ankle joint biomechanics, further clarity on the specific research objectives and their connection to material performance analysis would strengthen the introduction and enhance the coherence of the manuscript. This would help readers better anticipate the content and scope of the study presented in the manuscript. To better link the introduction with the subsequent sections of the manuscript (e.g., materials and methods, results), the introduction could explicitly mention the focus on material performance analysis and how it addresses the identified challenges in ankle joint replacement.

Response 8 : This command has been adhered to in the text of the research [6].

Point 9: While the methods provide a solid overview of the experimental setup, some sections could benefit from additional clarity on specific experimental procedures or steps. Providing more detailed step-by-step instructions could enhance reproducibility and understanding.

Response 9 : This command has been adhered to in the text of the search The joint was designed using the CATIA program and was retrieved into the Ansys program. The analysis was done with the importance of studying vibration in the same program, and the validity of the design was verified by comparison, as found in the aforementioned references.

Point 10: Figure 18: I suggest cropping the picture to the ankle design, not showing the program’s menu bar etc.

Response 10 : This command has been adhered to in the text of the research.

Point 11: While the authors provide good references to other studies and managed to link the discussion to the challenges stated in the introduction, I would welcome to establish a stronger linkage to their results. The manuscript could be improved through a more detailed discussion of how specific results led to a specific conclusion, or how they can be used to address the challenges mentioned in the introduction. This would provide transparency and clarity regarding the reasoning behind each conclusion.

Response 11: We appreciate your acknowledgment of the references provided and the connection established between the discussion and the challenges outlined in the introduction. We recognize the opportunity to strengthen the linkage to our results for improved transparency and clarity. Moving forward, we worked in this revised version on providing a more detailed discussion elucidating how specific results contribute to our conclusions and how they can effectively address the challenges highlighted in the introduction. This will enhance the manuscript's coherence and provide readers with a clearer understanding of the rationale behind each conclusion.

Point 12: In addition, it would be helpful to include a limitations paragraph addressing the potential impact of any assumptions made in the FE analysis or the limitations associated with the experimental design (and analysis methods).

Response 12 : We acknowledge the importance of addressing potential limitations in our study. We included a dedicated paragraph in the manuscript discussing any assumptions made in the Finite Element (FE) analysis and highlighting limitations associated with the analysis. This is hoped to provide readers with a comprehensive understanding of the scope and potential constraints of our study, enhancing the overall transparency and credibility of our findings.