Biomechanical Comparison of Salvage Pedicle Screw Augmentations Using Different Biomaterials

Round 1

Reviewer 1 Report

 

This paper describes the effectiveness of the 4 different biomaterials to be used for augmented pedicle screws in the spine. The authors also tested the augmented pedicle screws in different pseudo-bone types (e.g osteoporotic bone) to evaluate the strength pull out of the pedicle screws from three types of bones. 

In general, there are many studies in the literature showing pedicle screw augmentation with PMMA allows for a significant increase in the pull-out strength of the screws when implanted in osteoporotic bone.

I am not sure what is the value added with the current manuscript for the readers.

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Reviewer 2 Report

The authors reported experimental investigations on the biomechanical stabilities of salvage pedicle screw augmentations using different biomaterials. The manuscript is well written and presents interesting results. There is a major concern from the reviewer. Pullout test apparently is one of the most important experimental methods, however, pullout test may only characterize the initial stability, while other effects such as fretting and stress shielding may also play important roles in the biomechanical stability of the fixation. Thus, experimental results from pullout test should be discussed and analyzed in combination of other effects such and fretting and stress shielding. The relationship between pullout force and other biomechanical effects such as fretting and stress shielding, and their overall contribution to the long-term stability of fixation should be further clarified.

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Reviewer 3 Report

The authors evaluated the biomechanical properties of screws augmented with four different materials and the effect of different pilot hole sizes and bone densities on screw fixation. They concluded that bone cement provides the most significantly augmented effect in each pilot hole size and bone density setting and could be considered preferentially to achieve larger initial stability during revision surgery, especially for bones with osteoporotic quality.

The study is well designed and written. I do not have major objections, just several, mostly minor, objections / suggestions for improvement of the quality of the study:

1. The authors provided several biochemical formulas such as [Ca10(PO4)6(OH)2]. Please specify the formulas in a regular way using the subscript option for numbers presented in formulas. Please revise all of the formulas through the text.

2. In the description of materials used for this study the authors stated that they used blocks ‘’better than normal bone’’. Please can you describe it more specifically, what does it mean, how it was defined?

3. Figure 2 – It is unclear what letter ‘’B’’ on the third and fourth screw figure represents. Please explain in the legend of the Figure.

4. In Figures 4 and 5, 7 and 8 the authors used several abbreviations. Each abbreviation should be explained in the legend of the Figure. Please revise.

5. The most important, how many samples and how many measurements were performed in each group. This should be described in more details under the methodology section. 

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Reviewer 4 Report

I'm very glad to become acquainted with such interesting research. Hope that my review will help to improve the quality of the article. The authors made significant work, but, still, there are some notes:

In the discussion it is no sense to show force values with decimal, but it's better to show confidence interval.

In the continuation of the study I advise to analyze radiological images or even to use CT for analyzing test blocks after the insertion of screws.

 

It was very exciting to become acquainted with your research.

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