Explanatory Factors for Periprosthetic Infection in Total Knee Arthroplasty

Round 1

Reviewer 1 Report

Dear Authors: the sentence that shocked me is "Patella should only be replaced in selected cases and certainly never systematically, since the risk 33 may be greater than the benefit." Patella replacing has been debated since 1980s, and there is no strong evidence in favour of it or not, but it is linked to clinical results. If You found than patellar prosthesis is a risk factor for infection, You should deepen this point. Also, correlation between "aged" surgeons and infection is not well explained, as it is not a direct correlation. Also, longer hospitalization should be evaluated for more factors.. overall impression is that the paper is good, but some points has to be refined together with extensive English editing. Nice job! best regards,

Author Response

Response to Reviewer 1:

First of all, we would like to express our sincere gratitude for all comments and suggestions received from the Reviewer 1. This information has certainly enriched the text for its best understanding, thank you very much indeed. We have clarified the reviewer’s questions. We have introduced the required changes both in our answers to the specific comments and in the final manuscript v1.

 

 

Reviewer 1

Dear Authors: the sentence that shocked me is "Patella should only be replaced in selected cases and certainly never systematically, since the risk 33 may be greater than the benefit." Patella replacing has been debated since 1980s, and there is no strong evidence in favour of it or not, but it is linked to clinical results. If You found than patellar prosthesis is a risk factor for infection, You should deepen this point.

Response: Thank you very much for pointing it out. We have include some new information in the abstract to clarify this section. And we have deepened this point in “Discussion section”.

Abstract

“In this study, it is found that the replacement of the patella may be a factor of infection, but it should be corroborated with randomized clinical trials. Furthermore, patients who underwent longer surgeries or those with prolonged hospital stays should be closely monitored to detect infection as soon as possible and establish the most appropriate treatment”.

 

Discussion

One of the main findings of the present study is that patients who undergo prosthetic replacement of the patella have twice the risk of developing infection in relation to those other cases in which it was not replaced (p=0.046). Although the significance was small, that information was not observed in any previously conducted study. Those studies that reported the infection rate according to whether the patella was replaced or not, obtained the majority of infections in those patients who had the patella replaced, but without being statistically significant this data. Although it is important to note that these studies reported infection as a complication of surgery, they did not conclude if it was a consequence of patellar replacement[32-36]. These randomized studies mentioned indicate that, no general recommendations can be made in this regard. It is necessary more randomized clinical trials to establish if the causal relationship between patella replacement and the appearance of infection in knee arthroplasties exists. Considering our results, the patella should not be replaced systematically, but rather select patients appropriately, as doing so may increase the risk of infection and not all patients may need a prosthetic patella.

REFERENCES:

32. Campbell DG, Duncan WW, Ashworth M, Mintz A, Stirling J, Wakefield L et al. Patellar resurfacing in total knee replacement: A ten-year randomised prospective trial. J Bone Joint Surg Br. 2006; 88(6); 734-9. Doi: 10.1302/0301-620X.88B6.16822
33. Smith AJ, Wood DJ, Li MG. Total knee replacement with and without patellar resurfacing: A prospective, randomised trial using the Profix total knee system. J Bone Joint Surg Br: 2008; 90(1): 43-9. Doi: 10.1302/0301-620X.90B1.18986
34. Zhong-Tang L, Pei-Liang F, Hai-Shan W, Yunli Z. Patellar reshaping versus resurfacing in total knee arthroplasty - Results of a randomized prospective trial at a minimum of 7years’ follow-up. Knee. 2012; 19(3): 198–202. Doi: 10.1016/j.knee.2011.03.004
35. Roberts DW, Hayes TD, Tate CT, Lesko JP. Selective patellar resurfacing in total knee arthroplasty: A prospective, randomized, double-blind study. J Arthroplasty. 2015; 30(2): 216-22. Doi: 10.1016/j.arth.2014.09.012
36. Aunan E, Næss G, Clarke-Jenssen J, Sandvik L, Kibsgard TJ. Patellar resurfacing in total knee arthroplasty: Functional outcome differs with different outcome scores. Acta Orthop. 2016. 87(2): 158-64. Doi; 10.3109/17453674.2015.1111075

Reviewer 1. Also, correlation between "aged" surgeons and infection is not well explained, as it is not a direct correlation. Also, longer hospitalization should be evaluated for more factors.. overall impression is that the paper is good, but some points has to be refined together with extensive English editing. Nice job! best regards.

Response: Thank you very much for pointing it out. We have include some new information in “Discussion and Limitation section”.

“When it comes to the experience of the surgeon, some literature describes that although greater experience might be considered a benefit, there is an inverse and paradoxical relationship between it and quality patient outcomes [37]. Substantial numbers of aging surgeons will bear greater workloads and their level of stress would increase [38]. Other factors that may be involved in surgeon experience, as operating room environment (teaching hospital or hospital volume) [39].”

NEW REFERENCES:

37. Schenarts PJ, Cermaj S. The Aging Surgeon. Surgical Clinics of North America. 2016. 96,1: 129-138.
38. Yu C. Letter to the Editor: The Problem of the Aging Surgeon: When Surgeon Age Becomes a Surgical Risk Factor. Clin Orthop Relat Res. 2020. 478(5): 1137-1138. Doi: 10.1097/CORR.0000000000001223.
39. Blanco JF, Díaz A, Melchor FR, da Casa C, Pescador D. Risk factors for periprosthetic joint infection after total knee arthroplasty. Archives of Orthopaedic and Trauma Surgery. 2020. 140: 239-245. doi: 10.1007/s00402-019-03304-6

 

“As limitations in the study we mainly consider its retrospective nature and that it was only performed in one hospital center, the size of the sample could be considered small (it is confined to a Spanish population) that could explain these signification. Furthermore, the variables were those already existing in the database without being able to add or modify any other. For example, the surgery duration was defined as the elapsed time from the moment the patient entered the operating room until the moment they left, instead the elapsed time time between the incision and skin closure. In future studies it would also necessary to consider the relationship between surgical experience and patella replacement rate, the length of hospitalization (a longer hospitalization should be evaluated for more factors).”

 

 

Thank you very much indeed.

Yours sincerely,

Prof. Raúl Soto-Cámara

 

Reviewer 2 Report

Dear authors, I read the manuscript with great interest as it deals with a burning issue in daily  Arthroplasty practice. Please consider the following for an updated version of the paper.

1. The study sample was until 2018. Please define why there is that lag from 2018 until the present year.
2. A more robust explanation of the clinical application of your findings and explanation of your results would add to the paper.

Author Response

Response to Reviewer 2:

First of all, we would like to express our sincere gratitude for all comments and suggestions received from the Reviewer 2. This information has certainly enriched the text for its best understanding, thank you very much indeed. We have clarified the reviewer’s questions. We have introduced the required changes both in our answers to the specific comments and in the final manuscript v1.

 

REVIEWER 2. Dear authors, I read the manuscript with great interest as it deals with a burning issue in daily Arthroplasty practice. Please consider the following for an updated version of the paper. The study sample was until 2018. Please define why there is that lag from 2018 until the present year.

Response: Thank you very much for pointing it out. We have considered until 2018 because we started the study in 2019 and we needed at least one year of minimum follow-up. In any case, due to the COVID-19 pandemic, the follow-up of new patients was stopped in 2019. We will take this consideration into account for future research, as soon as we can resume our usual activity that has been altered in our workplace, in the hospital, due to the pandemic

 

REVIEWER 2. A more robust explanation of the clinical application of your findings and explanation of your results would add to the paper.

 

Response:  Thank you very much for pointing it out. We have added new information of the clinical application of our findings and explanation of our results add to the paper, before “Conclusion section”.

“The identification of the most important RFs is a key element to implement measures that could reduce the rate of infection after TKA. Effective strategies to minimize RF identified in this paper and previous studies must be instituted stringent in the perioperative protocols. In our study, it is found that male patients, the replacement of the patella, longer intervention and hospital stay, may be RFs of infection, but they should be corroborated with randomized clinical trials. Although it is not possible to draw absolute conclusions from this study, it must be valid to establish the bases for future studies on the subject. These results allow us to establish some preventive measures of TKA, such as surgery performed or operative time reduction, in addition to those already established in general terms such as antibiotic prophylaxis and skin preparation.”

 

Thank you very much indeed. This information has certainly enriched the text for its best understanding. Yours sincerely,

 

Prof. Raúl Soto-Cámara

Reviewer 3 Report

General comments

The main finding in this study is an association between patellar resurfacing and an increased infection rate. This finding is just barely significant (CI for OR 1.01-6.31) and the confidence interval is wide. The frequency of patients receiving a patella resurfacing is also quite high (278/907=30.6%). Considering that these data include an infection rate of 3.6% (33/907), i.e. higher than the 0.5-2% expected from literature, and that the sample size is small for a study that wishes to assess risk factors for infection, the finding should not be over interpreted. It may be considered a hypothesis generating finding that should be confirmed in larger studies, such as register studies. All this could be discussed with clarity in the discussion section and also highlighted in the conclusion.

Specific comments

Abstract:

Line 21: Rephrase: variables dependent.

Lines 25-26: The sentence “Significantly, those patients who had their patella replaced had a higher risk of …” should be rephrased to “Those patients who had their patella replaced had a significantly higher risk of…”

Line 32-33: This is a recommendation, not necessarily a conclusive finding of the study. The results say nothing about any benefit of patella resurfacing. Please make a conclusion that is supported in the results (see general comment above)

Line 67-68. The sentence “It appears that the sizes’s larger of the prosthesis, the greater the possibility of infection” does not make sense. In addition, the reference used (13) show an increased risk for infection in unicompartmental prostheses.

Line 68: Replace “throught” with “thought”

Line 73: Replace “higherrates” with “higher rates”

Lines 75-78. The aim should be rephrased in a clearer language. Is the statement of "much larger sample" warranted in this case? Larger than ref 19, which have 2573 cases?

 

Method & Material:

 

Line 96-97: Please give mean follow-up time and min-max range. This could also be accounted for in the results section instead. Important for interpretation of an infection rate.

 

Line 106-107: Do the authors interpret this presence of personnel in training as the operation being performed as a learning operation, therefore taking longer time and hence inflicting a larger risk?

 

Line 119: Rephrase “wasdefined” to “was defined”

 

Line 120: Is the time between the incision and skin closure available in the local registry?

Line 140: Were these all patients treated in the defined period (i.e. a consecutive series)? Or where any patients not analyzed, and if so, why not? Where these all primary arthroplasties or does the sample include revision cases? Please clarify.

Line 149: 278 out of 907 got a patella prosthesis, a quite high percentage (3.6%), which should be written out. Is the indication for such a prosthesis at the present institution known to the authors?

 

Line 153-154: 33 out of 907=3.6%. This infection rate should be written out! Higher than expected (0.5-2%, according to ref 6).

 

Line 164: Table 1: It is too difficult to understand which numbers the p-values refer to. Please make the table easier to interpret. And switch P-valor to P-value.

 

Line 168-171: Multivariable analysis: The precise factors that were included in the multivariable analysis should be accounted for and also which selection method that were chosen (fx. forward or backward selection). Did the authors include the significant factors from Table 1 in the multivariate analysis?

Discussion:

Line 176: Rephrase “the developing an infection in the TKAs”.

Line 177: An “is” is missing.

Line 183-184: Do the wording “has been associated with..” refer to the present study or to the literature”. Please clarify.

Line 186-190: This study did thus not find what others have found. Why? No tentative explanation is given in the discussion. Sample size too low?

 

Line 196-199: If there is “a certain trend”, please give some examples from the studies referred to. This is otherwise too vague.

 

Line 201: I can´t find a reference 37 in the reference list.

 

Line 201: “Due to the characteristics of these studies”. These studies are RCTs and this should be highlighted.

 

Line 202: Rephrase sentence (“Therefore etc”).

 

Line 211: Clarify that “this influence disappears when analyzed together with other factors” is referring to the present study.

 

Line 211-215: No explanation is given to why the authors used this definition.

 

Line 229: Rephrase “Other limitation..”.

 

Line 233-245: This conclusion could be substantially shortened to what is actually found in the study (see general comment)

Author Response

. Response to Reviewer 3:

First of all, we would like to express our sincere gratitude for all comments and suggestions received from the Reviewer 3. This information has certainly enriched the text for its best understanding, thank you very much indeed. We have clarified the reviewer’s questions. We have introduced the required changes both in our answers to the specific comments and in the final manuscript v1.

REVIEWER 3. General comments

The main finding in this study is an association between patellar resurfacing and an increased infection rate. This finding is just barely significant (CI for OR 1.01-6.31) and the confidence interval is wide. The frequency of patients receiving a patella resurfacing is also quite high (278/907=30.6%). Considering that these data include an infection rate of 3.6% (33/907), i.e. higher than the 0.5-2% expected from literature, and that the sample size is small for a study that wishes to assess risk factors for infection, the finding should not be over interpreted. It may be considered a hypothesis generating finding that should be confirmed in larger studies, such as register studies. All this could be discussed with clarity in the discussion section and also highlighted in the conclusion.

Response: Thank you very much for pointing it out. We have added the following information in the abstract, discussion and conclusion section.

Abstract

“In this study, it is found that the replacement of the patella may be a factor of infection, but it should be corroborated with randomized clinical trials. Furthermore, patients who underwent longer surgeries or those with prolonged hospital stays should be closely monitored to detect infection as soon as possible and establish the most appropriate treatment.”

Discussion

“Regarding the factors dependent on the health system, the experience of the surgeon and the replacement of the patella were the ones which increased the risk of developing an infectious process significantly. One of the main findings of the present study is that patients who undergo prosthetic replacement of the patella have twice the risk of developing infection in relation to those other cases in which it was not replaced (p=0.046). Although the significance was small, that information was not observed in any previously conducted study. Those studies that reported the infection rate according to whether the patella was replaced or not, obtained the majority of infections in those patients who had the patella replaced, but without being statistically significant this data. Although it is important to note that these studies reported infection as a complication of surgery, they did not conclude if it was a consequence of patellar replacement[32-36].”

“As limitations in the study, we mainly consider its retrospective nature and that it was only performed in one hospital centre, the size of the sample could be considered small (it is confined to a Spanish population) that could explain these signification. Furthermore, the variables were those already existing in the database without being able to add or modify any other. For example, the surgery duration was defined as the elapsed time from the moment the patient entered the operating room until the moment they left, instead the elapsed time time between the incision and skin closure. In future studies it would also necessary to consider the relationship between surgical experience and patella replacement rate, the length of hospitalization (a longer hospitalization should be evaluated for more factors).”

Conclusion

“Determining the RFs for the development of an infection in TKA is crucial to try to reduce this complication as much as possible.

In our study, we observed that certain risk factors could predispose to developing a possible prosthetic infection; such as male sex, increased surgical time or a prolonged hospital stay. All of these factors are widely described in the literature. Perhaps the most important fact that emerges from our study is the possible association of the infection with the patella resurfacing, which should be individually assessed, it should be corroborated in future randomized clinical trials.”

REVIEWER 3. Specific comments

Abstract: Line 21: Rephrase: variables dependent.

Response: Thank you very much for pointing it out. We have made the suggested change: “Dependents variables”.

REVIEWER 3. Lines 25-26: The sentence “Significantly, those patients who had their patella replaced had a higher risk of …” should be rephrased to “Those patients who had their patella replaced had a significantly higher risk of…”

Response: Thank you very much for pointing it out. We have made the suggested change: “Those patients who had their patella replaced had a significantly higher risk of”

REVIEWER 3. Line 32-33: This is a recommendation, not necessarily a conclusive finding of the study. The results say nothing about any benefit of patella resurfacing. Please make a conclusion that is supported in the results (see general comment above)

Response: Thank you very much for pointing it out. We have modified the sentence in “Abstract section”:

“In this study, it is found that the replacement of the patella may be a factor of infection, but it should be corroborated with randomized clinical trials. Furthermore, patients who underwent longer surgeries or those with prolonged hospital stays should be closely monitored to detect infection as soon as possible and establish the most appropriate treatment.”

 

REVIEWER 3. Line 67-68. The sentence “It appears that the sizes’s larger of the prosthesis, the greater the possibility of infection” does not make sense. In addition, the reference used (13) show an increased risk for infection in unicompartmental prostheses.

Response: Thank you very much for pointing it out. We have clarified this sentence:

“Depending on the type of prosthesis, there has been a certain tendency to have a higher infection rate for total arthroplasties compared to unicondylar ones. So we would have to say that, as postulated in the second international consensus on musculoskeletal infections [13], a smaller prosthesis may represent also a smaller substrate for microbial colonization. Although no conclusive studies have been conducted linking this in theory, replacing the patella implies an increase in the prosthetic surface that can end up in an infection, but more detailed studies need to be performed on this. Therefore, it could be thought that patellar replacement is another RF in terms of developing a periprosthetic infection.”

REVIEWER 3. Line 68: Replace “throught” with “thought”

Response: Thank you very much for pointing it out. We have made the suggested change “thought”

REVIEWER 3. Line 73: Replace “higherrates” with “higher rates”

Response: Thank you very much for pointing it out. We have made the suggested change “higher rates”.

REVIEWER 3. Lines 75-78. The aim should be rephrased in a clearer language. Is the statement of "much larger sample" warranted in this case? Larger than ref 19, which have 2573 cases?

 Response: Thank you very much for pointing it out. We have made the suggested change in the aim:  “This study aims to identify risk factors associated with infection after a TKA”.

REVIEWER 3. Method & Material:

Line 96-97: Please give mean follow-up time and min-max range. This could also be accounted for in the results section instead. Important for interpretation of an infection rate.

Response: Thank you very much for pointing it out. We have made the suggested change:

“The mean follow-up period after surgery was 2.3 years (SD 0.6) and the minimum and maximum were 1.5 and 3 years respectively.”

REVIEWER 3. Line 106-107: Do the authors interpret this presence of personnel in training as the operation being performed as a learning operation, therefore taking longer time and hence inflicting a larger risk?

Response: Thank you very much for pointing it out. The presence of personnel in training does not have to entail a longer intervention time, since the surgery is also performed by the main surgeon. Trainees only assist with simple tasks. But in our opinion it is not without risk as far as infection is concerned. That is, for example, the trainees may be holding the separators, and may not have taken all the precautions in matters of asepsis. 

REVIEWER 3. Line 119: Rephrase “wasdefined” to “was defined”

Response: Thank you very much for pointing it out. We have made the suggested change “was defined”.

REVIEWER 3. Line 120: Is the time between the incision and skin closure available in the local registry?

Response: Thank you very much for pointing it out. No it's not in the local registry. We have added the following sentence as limitation in the discussion section:

“As limitations in the study, we mainly consider its retrospective nature and that it was only performed in one hospital centre, the size of the sample could be considered small (it is confined to a Spanish population) that could explain these signification. Furthermore, the variables were those already existing in the database without being able to add or modify any other. For example, the surgery duration was defined as the elapsed time from the moment the patient entered the operating room until the moment they left, instead the elapsed time time between the incision and skin closure. In future studies it would also necessary to consider the relationship between surgical experience and patella replacement rate, the length of hospitalization (a longer hospitalization should be evaluated for more factors).”

REVIEWER 3. Line 140: Were these all patients treated in the defined period (i.e. a consecutive series)? Or where any patients not analyzed, and if so, why not? Where these all primary arthroplasties or does the sample include revision cases? Please clarify.

Response: Thank you very much for pointing it out. They are all patients treated with a primary arthroplasty in the defined period. There are no unanalyzed patients. Reviews are not included.

REVIEWER 3. Line 149: 278 out of 907 got a patella prosthesis, a quite high percentage (3.6%), which should be written out. Is the indication for such a prosthesis at the present institution known to the authors?

Response: Thank you very much for pointing it out. In fact there is no specific protocol or indication in our institution. Whether or not the patella is replaced is left to the choice of the main surgeon.

REVIEWER 3. Line 153-154: 33 out of 907=3.6%. This infection rate should be written out! Higher than expected (0.5-2%, according to ref 6).

Response: Thank you very much for pointing it out. Indeed, the infection rate is higher than expected and we are working to reduce it.

REVIEWER 3. Line 164: Table 1: It is too difficult to understand which numbers the p-values refer to. Please make the table easier to interpret. And switch P-valor to P-value.

Response: Thank you very much for pointing it out. We have made the suggested change and the table easier to interpret.

REVIEWER 3. Line 168-171: Multivariable analysis: The precise factors that were included in the multivariable analysis should be accounted for and also which selection method that were chosen (fx. forward or backward selection). Did the authors include the significant factors from Table 1 in the multivariate analysis?

Response: Thank you very much for pointing it out. We included the significant factors from Table 1 in the multivariate analysis. And we have clarified “Method section” and “Result section”:

“To quantify the magnitude of the association between variables, the odds ratio (OR) was calculated using a forward selection multivariate regression analysis, adjusted for sex and age, which included all those variables that obtained statistical significance in the previously univariate analysis”.

“In the multivariate analysis performed (forward selection), with the significant factors from Table 1, the factors that were related to a greater probability of developing a post-surgical infection after TKA were: male sex (OR 2.99; 95% confidence interval (CI) 1.32-5.74), previous experience of the surgeon over 10 years (OR 2.64; 95% CI 1.01-6.97) or replacement of the patella by a prosthetic implant (OR 2.07; 95% CI 1.01-6.31) (Table 2)”.

REVIEWER 3. Discussion:

Line 176: Rephrase “the developing an infection in the TKAs”.

Response: Thank you very much for pointing it out. We have clarified the sentence:

“The most important finding of this study could be the association between patellar replacement and the possibility of developing an infection”.

REVIEWER 3. Line 177: An “is” is missing.

Response: Thank you very much for pointing it out. We have made the suggested change.

REVIEWER 3. Line 183-184: Do the wording “has been associated with..” refer to the present study or to the literature”. Please clarify.

Response: Thank you very much for pointing it out. We have clarified the sentence:

“In our study, male sex is the only patient-dependent factor that has been associated with an increased risk of developing an infection in the TKAs, becoming up to 3 times higher.”

REVIEWER 3. Line 186-190: This study did thus not find what others have found. Why? No tentative explanation is given in the discussion. Sample size too low?

Response: Thank you very much for pointing it out. Indeed, one of the limitations of the study is the sample size that can explain these small differences, we have added this in the limitations:

“As limitations in the study, we mainly consider its retrospective nature and that it was only performed in one hospital centre, the size of the sample could be considered small (it is confined to a Spanish population) that could explain these signification. Furthermore, the variables were those already existing in the database without being able to add or modify any other. For example, the surgery duration was defined as the elapsed time from the moment the patient entered the operating room until the moment they left, instead the elapsed time time between the incision and skin closure. In future studies it would also necessary to consider the relationship between surgical experience and patella replacement rate, the length of hospitalization (a longer hospitalization should be evaluated for more factors).

REVIEWER 3. Line 196-199: If there is “a certain trend”, please give some examples from the studies referred to. This is otherwise too vague.

Response: Thank you very much for pointing it out, we have clarified these sentences and we give some examples from the studies referred to.

One of the main findings of the present study is that patients who undergo prosthetic replacement of the patella have twice the risk of developing infection in relation to those other cases in which it was not replaced (p=0.046). Although the significance was small, that information was not observed in any previously conducted study. Those studies that reported the infection rate according to whether the patella was replaced or not, obtained the majority of infections in those patients who had the patella replaced, but without being statistically significant this data. Although it is important to note that these studies reported infection as a complication of surgery, they did not conclude if it was a consequence of patellar replacement[32-36]. These randomized studies mentioned indicate that, no general recommendations can be made in this regard. It is necessary more randomized clinical trials to establish if the causal relationship between patella replacement and the appearance of infection in knee arthroplasties exists. Considering our results, the patella should not be replaced systematically, but rather select patients appropriately, as doing so may increase the risk of infection and not all patients may need a prosthetic patella.

REFERENCES:

32. Campbell DG, Duncan WW, Ashworth M, Mintz A, Stirling J, Wakefield L et al. Patellar resurfacing in total knee replacement: A ten-year randomised prospective trial. J Bone Joint Surg Br. 2006; 88(6); 734-9. Doi: 10.1302/0301-620X.88B6.16822
33. Smith AJ, Wood DJ, Li MG. Total knee replacement with and without patellar resurfacing: A prospective, randomised trial using the Profix total knee system. J Bone Joint Surg Br: 2008; 90(1): 43-9. Doi: 10.1302/0301-620X.90B1.18986
34. Zhong-Tang L, Pei-Liang F, Hai-Shan W, Yunli Z. Patellar reshaping versus resurfacing in total knee arthroplasty - Results of a randomized prospective trial at a minimum of 7years’ follow-up. Knee. 2012; 19(3): 198–202. Doi: 10.1016/j.knee.2011.03.004
35. Roberts DW, Hayes TD, Tate CT, Lesko JP. Selective patellar resurfacing in total knee arthroplasty: A prospective, randomized, double-blind study. J Arthroplasty. 2015; 30(2): 216-22. Doi: 10.1016/j.arth.2014.09.012
36. Aunan E, Næss G, Clarke-Jenssen J, Sandvik L, Kibsgard TJ. Patellar resurfacing in total knee arthroplasty: Functional outcome differs with different outcome scores. Acta Orthop. 2016. 87(2): 158-64. Doi; 10.3109/17453674.2015.1111075

 REVIEWER 3. Line 201: I can´t find a reference 37 in the reference list.

Response: Thank you very much for pointing it out, reference 37 was a mistake.

REVIEWER 3. Line 201: “Due to the characteristics of these studies”. These studies are RCTs and this should be highlighted.

Response: Thank you very much for pointing it out. We have clarified the sentence with that information:

These randomized studies mentioned indicate that, no general recommendations can be made in this regard.

REVIEWER 3. Line 202: Rephrase sentence (“Therefore etc”).

Response: Thank you very much for pointing it out. We have rephrased the sentence:

 

These randomized studies mentioned indicate that, no general recommendations can be made in this regard. It´s necessary more randomized clinical trials to establish if exist the causal relationship between patella replacement and the appearance of infection in knee arthroplasties.

 

REVIEWER 3. Line 211: Clarify that “this influence disappears when analyzed together with other factors” is referring to the present study.

Response: Thank you very much for pointing it out. We have clarified the sentence:

“However, in our study, this influence disappears when analyzed together with other factors”. 

REVIEWER 3. Line 211-215: No explanation is given to why the authors used this definition.

 Response: Thank you very much for pointing it out. We have clarified the sentence: and we have added some information as limitation in the discussion section:

“Contrary to what was considered in other studies, in which the duration of the surgery is defined as the time interval that extends from the first incision in the skin to the complete closure of the wound [4,31], in this work it has been considered as the interval that elapses from when the patient enters the operating room until leaving it, due to possible iatrogenesis of the environment”.

“As limitations in the study we mainly consider its retrospective nature and that it was only performed in one hospital center, the size of the sample could be considered small (it is confined to a Spanish population) that could explain these signification. Furthermore, the variables were those already existing in the database without being able to add or modify any other. For example, the surgery duration was defined as the elapsed time from the moment the patient entered the operating room until the moment they left, instead the elapsed time between the incision and skin closure.”

REVIEWER 3. Line 229: Rephrase “Other limitation..”.

Response: Thank you very much for pointing it out. We have eliminated the sentence.

REVIEWER 3. Line 233-245: This conclusion could be substantially shortened to what is actually found in the study (see general comment)

Response: Thank you very much for pointing it out. We have reviewed and shortened the conclusion section

Conclusions

Determining the RFs for the development of an infection in TKA is crucial to try to reduce this complication as much as possible.

In our study, we observed that certain risk factors could predispose to developing a possible prosthetic infection; such as male sex, increased surgical time or a prolonged hospital stay. All of these factors are widely described in the literature. Perhaps the most important fact that emerges from our study is the possible association of the infection with the patella resurfacing, which should be individually assessed, it should be corroborated in future randomized clinical trials.

 

 

 

Thank you very much indeed. This information has certainly enriched the text for its best understanding. Yours sincerely,

 

Prof. Raúl Soto-Cámara

Round 2

Reviewer 1 Report

I would like to congratulate with the Authors for the paper and the R1 version they proposed. One more suggestion, that is a personal impression not supported from studies but it is supported by clinical practice. More aged surgeons use to perform more complex cases than younger surgeons, and this could also explain a higher prevalence on infection more than higher volumes and level of stress, while I agree that in teaching hospitals more personnel is involved (anesthesia and orthopedic residents, medical students, educational visitors, young nurses, specialists to manage instruments and modular implants..). Finally, some minor English editing is still needed. Again: nice job, well done!

Author Response

Response to Reviewer 1:

First of all, we would like to express our sincere gratitude for all comments and suggestions received from the Reviewer 1. This information has certainly enriched the text for its best understanding, thank you very much indeed. We have clarified the reviewer’s questions. We have introduced the required changes both in our answers to the specific comments and in the final manuscript v2.

 

 

Reviewer 1

I would like to congratulate with the Authors for the paper and the R1 version they proposed. One more suggestion, that is a personal impression not supported from studies but it is supported by clinical practice. More aged surgeons use to perform more complex cases than younger surgeons, and this could also explain a higher prevalence on infection more than higher volumes and level of stress, while I agree that in teaching hospitals more personnel is involved (anesthesia and orthopedic residents, medical students, educational visitors, young nurses, specialists to manage instruments and modular implants..). Finally, some minor English editing is still needed. Again: nice job, well done!

Response: Thank you very much for pointing it out. We have added that information in the discussion section. Finally, we have used a professional scientific editing service.

When it comes to the experience of the surgeon, some literature describes that although greater experience might be considered a benefit, there is an inverse and paradoxical relationship between it and quality patient outcomes [37]. Substantial numbers of aging surgeons will bear greater workloads and their level of stress would increase [38]. Other factors that may be involved in surgeon experience, as operating room environment (teaching hospital or hospital volume) [39]. In our opinion, more aged surgeons use to perform more complex cases than younger surgeons, and this could also explain a higher prevalence on infection; while teaching hospitals more personnel is involved (anesthesia and orthopedic residents, medical students, educational visitors, young nurses, specialists to manage instruments and modular implants).

 

 

Thank you very much indeed.

Yours sincerely,

Prof. Raúl Soto-Cámara

 

Reviewer 2 Report

Dear authors, I read the updated version of the manuscript.

Comments well addressed.

Please provide a clear version of the updated manuscript.

 

Author Response

Response to Reviewer 2:

First of all, we would like to express our sincere gratitude for all comments and suggestions received from the Reviewer 2. This information has certainly enriched the text for its best understanding, thank you very much indeed. We have clarified the reviewer’s questions. We have introduced the required changes both in our answers to the specific comments and in the final manuscript v2.

 

REVIEWER 2. Dear authors, I read the updated version of the manuscript. Comments well addressed. Please provide a clear version of the updated manuscript.

Thank you very much indeed. We send you a new version (2) of the updated manuscript.

Yours sincerely,

 

Prof. Raúl Soto-Cámara