Title:Does Osteoporosis reduce the primary tilting stability of cementless acetabular cups?

Transcription

1 Author's response to reviews Authors: Christoph von Schulze Pellengahr Lars V von Engelhardt (larsvictor@gmx.de) Bernd Wegener (Bernd.Wegener@med.uni-muenchen.de) Peter E Müller (peter.mueller@med.uni-muenchen.de) Andreas Fottner (Andreas.Fottner@med.uni-muenchen.de) Patrick Weber (Patrick.Weber@med.uni-muenchen.de) Ole Ackermann (Ole.Ackermann@Sana.de) Matthias Lahner (M.Lahner@Klinikum-Bochum.de) Wolfram Teske (W.Teske@Klinikuim-Bochum.de) Version:3Date:11 February 2015 Author's response to reviews: see over

2 Author's response to reviews Title: Does Osteoporosis reduce the primary tilting stability of cementless Authors: Christoph von Schulze Pellengahr Lars V von Engelhardt (larsvictor@gmx.de) Bernd Wegener (Bernd.Wegener@med.uni-muenchen.de) Peter E Müller (peter.mueller@med.uni-muenchen.de) Andreas Fottner (Andreas.Fottner@med.uni-muenchen.de) Patrick Weber (Patrick.Weber@med.uni-muenchen.de) Ole Ackermann (Ole.Ackermann@Sana.de) Matthias Lahner (M.Lahner@Klinikum-Bochum.de) Wolfram Teske (W.Teske@Klinikuim-Bochum.de) Version: 3 Date: 28 Jaqnuary 2015 Author's response to reviews: see over

3 Dear Biomed Central Editorial Team, February 11 th, Object: MS: Does Osteoporosis reduce the primary tilting stability of cementless Christoph von Schulze Pellengahr, Lars Victor von Engelhardt et al. Thank you for consideration of our manuscript for publication in your journal. We have reviewed the above manuscript according to your reviewer s comments. Best regards Lars Engelhardt Reviewer's report Version:2Date:15 September 2014 Reviewer:Antonio Maestro Reviewer's report: Really there are no recomendations. I think it s possible to publish the paper and the article could be accepted. The only thinhg, and and in order to future articles, could be to make the laboratory work with other commercial avaliable cups, to knew the difference between them. Thanks for your recommendation in regard to future articles. Further trials with other commercial cups are surely of practical interest. Level of interest:an article of importance in its field Quality of written English:Acceptable Statistical review:no, the manuscript does not need to be seen by a statistician. Declaration of competing interests: The authors have declared that they have no competing interests Review #1 has no suggested changes for the manuscript.

4 Reviewer's report Version:2Date:28 September 2014 Reviewer:Edmundo Berumen-Nafarrate Reviewer's report: I recomen to have moré pictures of the bone And prosthesis As recommended, a picture of the prepared bone (Fig. 1) and two pictures of the prostheses used in this study have been added (Fig. 3 and 4). The porpouse of the article is to compare normal bone against osteporotic bone And it simce that the effort it is to compare to brand names Resulta are not that Clear The aim of the study was to assess the influence of the bone quality on the primary implant stability. To assess the influence of different cup designs, different brand names with different designs were tested in this study. We were not interested to compare just brand names. To clarify this remark of the 2 nd reviewer, the aims were added to the background/purpose section within the abstract and within the manuscript (page 2 and 5). In the results section, we added that different types of threaded and press-fit cups (shape, material, surfacing) were tested (page 9). This might prevent a misunderstanding. Level of interest:an article of outstanding merit and interest in its field Quality of written English:Acceptable Statistical review:yes, but I do not feel adequately qualified to assess the statistics. Declaration of competing interests: I declare that I have not competíng interest Review #2 has no further suggested changes for the manuscript.

5 Reviewer's report Version:2Date:15 December 2014 Reviewer:Mattia Loppini Reviewer's report: The authors performed an interesting study comparing the primary stability of pressfit and threaded cups in normal and osteoporotic bone. However, the manuscript needs major compulsory revisions before it could be considered for publication in the BMC Journal. Please, see below. Abstract The aim and conclusion in the abstract should be the same of those in the manuscript. As recommended, the aims and the conclusion in the abstract were rewritten according to the manuscript (page 2 and 3). Introduction Fine Review #3 has no suggested changes for the introduction. Methods The authors should clarify the criteria to assess the bone quality with Q-CT. They could also add a reference. Done (page 7). Furthermore two references were added as recommended (Ref. No. 1 and 7, page 18 and 19). The paragraph In contrast to ventral parts of the acetabulum. should be moved in the discussion section. We agree. The paragraph has been moved as recommended (page 7 and 10). Please clarify the test used for the statistical analysis to compare the results between the normal and osteoporotic group. I would also suggest to clarify the criteria to chose a parametric or non-parametric test. I would see also the power analysis on your sample. Although it is difficult to achieve a large number of specimens, the readers should now power of your results. Why did the authors do not perform a direct comparison between press-fit and

6 threaded cup in both groups? Please add the P value when you report the statistical significance of your comparisons. Again, why did the authors do not perform a direct comparison between press-fit and threaded cup in both groups? To prevent a misunderstanding, the statistical method to compare the results between the groups has now been rewritten in the methods section. The decision to use confidence intervals in this study was made with the Department of Statistics of the Ludwig-Maximilians-University Munich. As usual, the confidence intervals were stated at the 95% confidence level. A power analysis is not feasible for these descriptive statistics. Furthermore, confidence intervals are also helpful in determining whether the sample size was large enough to detect a significant difference (page 7 and 10). The hypothesis of this study was that the initial implant stability is different in osteoporotic and normal bone. Therefore, a comparison between press fit and threaded cups was not performed in this study. However, in regard to the values in tables 1 and 2, the two threaded cups in this study seem to have a higher initial implant stability as the two press-fit cups investigated in this study. Further trials with comparisons of different cup types might be a subject of future studies. Discussion The Discussion should start with a statement of the answers to the research question. If the research question has been posed as a hypothesis the acceptance of rejection of that hypothesis should be stated. The authors should also provide a comprehensive comment on their results. What did they expect? How did they explain their results? Done. As recommended, the discussion starts with the hypothesis posed in this study. We also documented the rejection of the hypothesis and stated our results in regard to the clinical situation. We also mentioned what we expected (page 10). An explanation of our results is given in later parts of the discussion. I would suggest to expand the comparison with previous study. Comparison and contrast to what has been previously presented, especially if there is a contrast that would suggest caution, should be stated. A comparison to previous studies has been performed (Plitz et al., Hadjari et al., Ohlin et al., Jäger et al., etc. -> page 10 and 11). We stated, that a further literature research on the primary stability of hip cups in human bone was unsuccessful (page 12). Additional studies using artificial materials as bone substitutes were mentioned and compared to our results (page 12).

7 I would also see a paragraph stating points of strength and limitations of the study. You could state here the limitations of cadaveric study. Do you believe that the size of the cup can play a critical role? Could your results be different with a different size of the cup? As recommended, limitations of cadaveric studies have been added to the discussion (page 10). We also discussed that the size of the cup might influence our results. This limitation has also been added to the discussion as recommended (page 11). In my opinion, the last sentence of the conclusion is not supported by your results. We agree. The sentence has been deleted as recommended (page 13). Figure 1 I would suggest to provide a figure with higher quality. Done (Fig. 2). Tables You should add the P value. The accuracy or precision is revealed by the confidence intervals. The confidence intervals are depicted in both tables. As commonly used, a confidence level of 95% (p <.05) was selected (page 16 and 17). Level of interest:an article whose findings are important to those with closely related research interests Quality of written English:Needs some language corrections before being published Statistical review:yes, and I have assessed the statistics in my report. Declaration of competing interests: I have no competing interests.