An Integrated Approach for Designing and Analyzing Lumbar Vertebral Biomodels with Artificial Disc Replacement

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article “An Integrated Approach for Designing and Analyzing Lumbar Vertebral Biomodels with Artificial Disc Replacement” aims are development an integrated approach for 3D lumbar vertebral bio model design, analysis and applying it for investigation of degeneration and the replacement of lumbar 20 artificial discs. The authors create for this purpose the model of two vertebra and one intervertebral disc and investigated the stress distribution in the developed system under external physiological load. Mechanical properties of vertebrae were chosen as linear and mechanical properties of intervertebral discs was not-linear Mooney-Rivlin like material mechanical properties. The investigation is actual and interesting for understanding of reasons why artificial intervertebral disc degenerates. The correct answer can increase the proper functioning time of artificial disc. On the other hand, I found two thinks which should be improved in the article. One of them, in my opinion, the convergence process of numerical investigation should be explained in more details. The second, it was mentioned about validation of the proposed model in the text, but I missed any comparisons of obtained results with good known models and/or experimental data. Therefore, the article is novel and actual, but can be publish just after improvements mentioned above.

Author Response

Dear Reviewer,

Thank you for your valuable feedback. 
We have carefully considered your comments and would like to address them in detail.

Point 1: Convergence process explanation:
Thank you for your valuable comment. In our study, hexahedral elements were utilized for constructing the mesh, while quadrilateral elements were employed for the core mesh [22]. The mesh sizes were systematically reduced, leading to finer discretization. The convergence was monitored by assessing the changes in the results as the mesh was refined. The convergence criteria were set such that the variation in the results reached less than 1% with respect to the change in mesh size. This was achieved by carefully refining the mesh until a consistent solution was obtained. Table 1 provides a detailed number of the nodes and elements after refinement for the various components of the vertebrae and disc models for both ProDisc and CHARITÉ implant cases.

Point 2: Comparison with existing models and experimental data:
Thank you for your valuable comment. We clarified this aspect in the discussion section in which a comparison with both experimental and clinical studies have made. More specifically, we cited the work of Niosi et al., 2006 [29], Noailly et al., 2011 [30], and Kurtz et al., 2007 [31] who highlight the importance of model validation through rigorous comparisons.

Thank you for your time and consideration.

Sincerely,

Reviewer 2 Report

Comments and Suggestions for Authors

The work presented describes an approach to desgn and analyse a 3D L3-L4 lumbar vertebral biomodel with lumbar artificial discs of 2 types. The study describes the biomodels preparation mechanisms and 3d techniques used, namely starting from the use of radiographic images and computed tomography data from the study sample. Additionally, the study evaluates mechanical properties in the implantation area and between disc components to assess the function of these artificial discs in restoring functional movement.

FE simulations are extensively described and the four physiological motion conditions fully characterized. The results obtained are analysed in terms of the ROM angle and Von_mises stress distribution in the bearing surface. 

In the results section, authors compare ROM results from their simulations with those from an experimental reference work, stating they are in accordance, but without describing the experimental conditions with which results were obtained, it is difficult to support the statement. Please specify what are "considered normal lumbar movement" related to reference [29]. Further detail from this reference would be useful to be presented here, for comparison purposes.

Since the results discussion is presented further in the next section, a sentence stating this, would be useful at this stage of the manuscript.

Overall, the manuscript is clearly written and the majority of conclusions are supported by the results. One last remark: disk stability is not characterized only by ROM studies like are presented here. Please be careful when implying this in the conclusions.

Author Response

Dear Reviewer,

Thank you for your valuable feedback. 
We have carefully considered your comments and would like to address them in detail.

Point 1: Specifics on experimental reference [29]:
Thank you for your valuable comment. In the revised manuscript, we included a more comprehensive description of the experimental setup and conditions used in reference [29] to establish the context for our comparison of ROM results. 
We provided additional information to define and contextualize what is deemed as normal lumbar movement, drawing on the specific findings and criteria outlined in reference [29].

Point 2: Acknowledgment of results discussion in the next section:
Thank you for your valuable comment. We included a sentence in the results section, indicating that further discussion of the results will be presented in the subsequent section. This enhanced the flow and clarity of the manuscript. 

Point 3: Consideration of disk stability beyond ROM studies:
Thank you for your valuable comment. In the conclusion section, we will exercise caution in implying that disk stability is not solely characterized by ROM studies. We expanded on this aspect to provide a more nuanced understanding of disk stability, considering additional relevant factors. 

Thank you for your time and consideration.

Sincerely,

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

My comments have been taken into account. The article can be published.

Reviewer 2 Report

Comments and Suggestions for Authors

Authors introduced all the previous recommendations in the present version of the manuscript. Nothing else to add. Can proceed to the next phase.