The Effect of Degenerative Changes on the Stressed State of the Intervertebral Disc and Adjacent Tissues: A Finite Element Study

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this manuscript, Ardatov et al., determined the mechanical interaction of intervertebral disc (L1-L2) and adjacent tissues in degenerative conditions using finite element analysis. Based on their research findings, authors observed the increase in bone stress due to stiffness of cartilage, and the dislocation tendencies of stress on all components of the model.  Manuscript is well organised and explained well. All figures and tables in the manuscript are clear and legible. Minor language corrections can further improve the manuscript. There are some limitations on the data presented in the manuscript that authors can address before it can be accepted.

Comments:

• Data is based on the modelling of only 1 IVD. Moreover, this data is based on hypothetical combinations of different severity of degeneration in AF and NP. It would be better if authors can model in more IVDs or apply their current results for verification using more IVDs.
• Authors need to add statistical analysis for their results.
• Authors should be more specific about their conclusions in the manuscript.

 

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript addresses the biomechanical effects of intervertebral disc degeneration on the stress state of the lumbar motion segment using finite element analysis. The topic is highly relevant for spine research and clinical biomechanics. The article is well organized and provides a clear description of the modeling approach and results. The systematic comparison of nine degeneration scenarios is a strong aspect of the study. The findings are of potential clinical interest, as they highlight how disc stiffening leads to higher stress levels in adjacent bone structures. However, there are several limitations that need to be addressed before the manuscript can be considered for publication. 

Comments

1. Validation of the FE model is lacking. Please compare your results with published experimental or in vivo studies of lumbar biomechanics to strengthen the conclusions.

2. The exclusion of spinal ligaments and paraspinal muscles should be explicitly discussed as a limitation, since these tissues significantly affect load distribution.

3. Provide more details on the material models used for the annulus fibrosus and nucleus pulposus. Consider discussing how anisotropy and viscoelasticity might alter your findings.

4. Figures illustrating stress distribution should be improved (consistent color scales, quantitative annotations, clearer legends).

5. The conclusion section would benefit from a more precise statement on the clinical relevance of the findings, particularly regarding fracture risk or treatment planning.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

1. The finite element model lacks a convergence analysis.
2. In the boundary condition setup, although the ultimate loading of the model has been determined, displacement was chosen as the boundary condition. However, the daily activities of the spine are governed by external loads rather than displacement control. A detailed justification for this choice is required.
3. How was the analysis model experimentally validated?
4. What is the imitation (simulation/approximation) approach applied in this study?
5. Equation (5) represents the Von Mises stress, yet the formula annotation states that σy is a yield stress. Is this the same as the yield strength listed in Table 1?
6. In Figures 3–12, all stresses are reported as Von Mises stresses. Were they calculated using Eq. (5)? If so, should this instead be referred to as yield stress?
7. Please clarify the meaning of C01 and C10 in Eq. (2).
8. Stiffness is a structural property, typically expressed in (N/mm), and its value depends on the geometry of the disc. In contrast, the elastic modulus is a material property (unit: MPa). Why does this study adopt stiffness rather than elastic modulus?

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

All my review comments have been addressed.