Optimization of Locking Plate Screw Angle Used to Treat Two-Part Proximal Humerus Fractures to Maintain Fracture Stability

Round 1

Reviewer 1 Report

Thank You for opportunity of the review of this interesting article. The following suggestion or question should be considered for future changes in this article:

1. FE method numerical models should contain all details such as for example the discretization, the material parameters, and interactions between the various components of the system. In addition, the mesh size discretization effect on the results should be discussed.
2. If the simplification of the model were used, the authors should presents its comparison with original geometry.
3. If possible the supplementary files with geometry and mesh should be added in the system.
4. In my opinion also the results (strain or stress maps and some curves -maybe force versus displacement) should be presented for models before and after optimization process. It will improve the “optimization” effect. Maybe the DOE plot should be presented?
5. How is the effect of the variable bone shape and size for possible using of the locking plate screw for humans?

Author Response

To whom it may concern,

Herewith we would like to thank the respected editor and reviewers for providing their precious time and valuable comments in improvement of our research article.

Attending to the revisions and comments noted by the reviewers for the research article manuscript entitled "Optimization of Locking Plate Screw Angle Used to Treat 2-Part Proximal Humerus Fractures to Maintain Fracture Stability", please find the appropriate modifications and answers to reviewers in this document.

Reviewer 1:

“FE method numerical models should contain all details such as for example the discretization, the material parameters, and interactions between the various components of the system. In addition, the mesh size discretization effect on the results should be discussed”

• Revised lines after revision (L96-96, L113-124): As suggested, the authors added more detailed information on the mesh, boundary conditions and parameters of the materials used. On the other hand, the discussion of the effect of discretization is beyond the scope of the research, obliquity and orthogonality levels close to 0 and 1 respectively were taken as a reference of a proper homogeneous mesh, which was achieved.

“If the simplification of the model were used, the authors should presents its comparison with original geometry” “If possible the supplementary files with geometry and mesh should be added in the system”

• Following the answer in the previous point, such comparison should be addressed if mesh and finite element analysis optimization were among the main research objectives. But, since they are not, model simplification was performed to decrease the system load, meshing and computing times. The simplification of the elements of the system was based on studies such as https://doi.org/10.1016/j.injury.2016.02.028, https://doi.org/10.1016/j.jot.2020.02.007, https://doi.org/10.1007/s10439-018-02160-6, https://doi.org/10.1016/j.addma.2020.101137. Likewise, as previously established, the quality of the mesh was checked by means of the obliquity and orthogonality values.

“In my opinion also the results (strain or stress maps and some curves -maybe force versus displacement) should be presented for models before and after optimization process. It will improve the “optimization” effect. Maybe the DOE plot should be presented?”

• Revised lines after revision (L237-239, L244-246): As suggested, the authors have added a table detailing the numerical optimization of the screw angle configuration to complement the graphical optimization comparison (Figure 6). The table compares the angles with the highest and lowest interfragmentary deformation for bending and compression tests, also the percentage of improvement for each type of test. In any case, beyond numerical optimization, the results highlight the importance of the tendency and the hierarchy of the angles of each screw pair, such as the calcar screws.

“How is the effect of the variable bone shape and size for possible using of the locking plate screw for humans?”

• Bone shape and size are undoubtedly a critical factor related to treatment performance, but it is a factor that depends primarily on the knowledge and experience of the orthopedic surgeon who is responsible for adapting the devices to the peculiarities of the patient. However, factors such as bone mass density, locking plate vertical positioning and screw angulation play a more critical role in treatment effectiveness. In this regard, the evaluation of the effect of bone geometry is outside the scope of the research.

Reviewer 2 Report

1. What are the A1, C1 and E1 screws?
2. Please attach to the work sample photos of broken bones (elements).
3. Where exactly the crack initiation and propagation took place?
4. It would be worthwhile to quote in the introduction also paper of: 1) Anil Kumar Singla, Jagtar Singh, Vishal Sharma, Munish Gupta, Qinghua Song, Dariusz Rozumek, Grzegorz M. Królczyk: Impact of cryogenic treatment on HCF and FCP performance of β-solution treated Ti-6Al-4V ELI biomaterial, Materials Vol. 13, 500, 2020.

Author Response

To whom it may concern,

Herewith we would like to thank the respected editor and reviewers for providing their precious time and valuable comments in improvement of our research article.

Attending to the revisions and comments noted by the reviewers for the research article manuscript entitled "Optimization of Locking Plate Screw Angle Used to Treat 2-Part Proximal Humerus Fractures to Maintain Fracture Stability", please find the appropriate modifications and answers to reviewers in this document.

“What are the A1, C1 and E1 screws?”

• The PHILOS locking plate used in the investigation has nine screw holes in the proximal area, of which, according to the study by Fletcher et al. (https://doi.org/10.1016/j.jse.2019.02.013), only six of the nine were selected due to the low mechanical stress surrounding them. As shown in Figure 3, the screw holes are named from top to bottom by the alphabet (A to E), and the columns are numbered from left to right (1 to 2). Therefore, screws A1, C1 and E1, represent the row and column of screws used in the study.

“Please attach to the work sample photos of broken bones (elements).”

• The research was performed solely by finite element analysis and not by physical experimentation, the simulation represents an ideal 2-part humerus fracture with fracture at the surgical neck based on Neer's classification, as it is the simplest fracture and gives a wider range of experimentation (such as screw angles) due to its simplicity. Also, one of the most studied, gr. https://doi.org/10.1016/j.injury.2016.02.028 and https://doi.org/10.1007/s10439-018-02160-6 .

“Where exactly the crack initiation and propagation took place?”

• Fracture and propagation of bone or locking plate? Neither is studied in the present investigation; the study focuses on the screw angle configuration that provides the least interfragmentary strain in an ideal 2-part humerus fracture with fracture at the surgical neck, based on Neer's classification. Therefore, the scenario outlined for the finite element analysis takes place after the fracture occurred, during ORIF treatment, mechanically tested not up to the point of failure.

“It would be worthwhile to quote in the introduction also paper of: 1) Anil Kumar Singla, Jagtar Singh, Vishal Sharma, Munish Gupta, Qinghua Song, Dariusz Rozumek, Grzegorz M. Królczyk: Impact of cryogenic treatment on HCF and FCP performance of β-solution treated Ti-6Al-4V ELI biomaterial, Materials Vol. 13, 500, 2020.”

• Revised lines after revision (L61-62): As suggested, the paper was cited naturally in the introduction section.

Round 2

Reviewer 1 Report

Thank You very much for author's response. I am not satisfy with the author's answers. In my opinion the authors should add similar figures like fig. 2, 3 and 4 in current article for numerical simulations like for example in: https://doi.org/10.1016/j.injury.2016.02.028 and much more accurately implement the previous suggestions like: “In my opinion also the results (strain or stress maps and some curves -maybe force versus displacement) should be presented for models before and after optimization process. It will improve the “optimization” effect. Maybe the DOE plot should be presented?” or "If possible the supplementary files with geometry and mesh should be added in the system.". 

Author Response

o whom it may concern,

Attending to the revisions and comments noted by the reviewers for the research article manuscript entitled "Optimization of Locking Plate Screw Angle Used to Treat 2-Part Proximal Humerus Fractures to Maintain Fracture Stability", please find the appropriate modifications and responses to reviewers in this document.

Reviewer 1:

“Thank You very much for author's response. I am not satisfy with the author's answers.

In my opinion the authors should add similar figures like fig. 2, 3 and 4 in current article for numerical simulations like for example in: https://doi.org/10.1016/j.injury.2016.02.028

• As suggested, Fig. 4 was added to the manuscript, like Fig. 2 in the example article for numerical simulations. However, Fig. 3 presented in the example article is not required for the purposes of this study, as interfragmentary strain was calculated as indicated in L65-70 and L205-207. The maximum displacement values were taken from the finite element analysis for each run. Finally, with respect to Fig. 4, since the strain between each scenario present a maximum difference of 0.5%, we consider presenting these results in table format, as shown in Table 1.

and much more accurately implement the previous suggestions like: “In my opinion also the results (strain or stress maps and some curves -maybe force versus displacement) should be presented for models before and after optimization process. It will improve the “optimization” effect. Maybe the DOE plot should be presented?” or

• Following the answer in the previous point, strain or stress maps are not necessary for the purposes of the study, because the interfragmentary strain theory (L65-70) (https://doi.org/10.1016/j.injury.2020.10.009) is used to obtain the strain in the fracture zone (L205-207), and thus evaluate the effect of the blocking plate on the bone healing process (L163-164). So, the authors have added a table detailing the numerical optimization of the screw angle configuration to complement the graphical optimization comparison (Figure 7). The table compares the angles with the highest and lowest interfragmentary deformation for bending and compression tests, also the percentage of improvement for each type of test. In any case, beyond numerical optimization, the results highlight the importance of the tendency and the hierarchy of the angles of each screw pair, such as the calcar screws. As suggested, Figure 6 is included showing Pareto diagrams (DOE diagrams) to determine the magnitude and importance of the effects on the latest optimization

"If possible the supplementary files with geometry and mesh should be added in the system."

• The authors consider that the supplementary files are outside the scope of the manuscript. On the other hand, following the previous recommendations, details of the FE numerical model have been included, such as meshing, boundary conditions and parameters of the materials used.