A Novel Syringe-Based Closed Suction System for Enhancing Skin Adherence in Microtia Reconstruction

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1) Line 21 “providing controlled negative pressure” negative pressure doesn’t exist. Maybe coauthors want to say, “alteration pressure, low pressure, vacuum pressure, etc.” Correct it

Note: old books have the word “negative pressure”, but it was incorrect

2) The introduction is very short; it must include information about the manuscript title, because in its present form, it is very poor

3) The manuscript reports pressure in Torrs, which should be reported in the international unit system, Pascal (Pa)

4) Table 1 reports on the cost in EGP. My recommendation is a change to USD for easy understanding

5) Line 117 “The mean duration of drainage was 6.81 ± 1.72 days” should use days and hours: maybe 6 days and 20 h  ± 1 day and 17 h

6) Figures 3 and 4 must improve, because at present these figures are very poor or of low quality

7) Figures 1 and 2 were not mentioned in the main text (only in the captions, so mention these figures in the text

8) The conclusion needs to be improved, because 3 lines were extremely poor

9) The manuscript has interesting results, but doesn’t have a discussion; include it

10) Co-authors included only 6 references; an international manuscript should include around 20 references

11) In general, the manuscript was prepared as a manual or report, and it must be improved according to the scientific manuscript

Author Response

Dear Reviewer,

We would like to thank you for your insightful and constructive feedback on our manuscript. We have carefully considered each point and have performed a revision to improve the scientific rigor and clarity of the paper.

The following is a point-by-point response to the comments provided:

1. Reviewer Comment: Line 21 “providing controlled negative pressure” negative pressure doesn’t exist... Correct it.

• Response: We appreciate this correction. We have replaced the term "negative pressure" with "vacuum pressure" throughout the entire manuscript, including the abstract, body text, and keywords.

2. Reviewer Comment: The introduction is very short; it must include information about the manuscript title...

• Response: The Introduction has been significantly expanded. It now provides a comprehensive background on the epidemiology, etiology, and psychosocial impact of microtia, as well as current surgical standards and emerging bioengineering frontiers . This establishes a stronger rationale for the clinical need for our device.

3. Unit Conversions (Torr to SI Units)

• Response: All pressure measurements previously reported in Torrs have been converted to the international unit system, Pascal/Kilopascal (kPa). Specifically, the generated vacuum is now correctly cited as approximately -68.93 kPa.

4. Currency Conversion

• Response: All cost analysis data in Table 1 has been converted from EGP to USD equivalents to ensure the manuscript’s economic findings are easily understood by an international audience.

5. Precision in Time Reporting

• Response: Following your suggestion, we have adjusted the reporting of drainage duration from decimals to days and hours. For example, the mean duration is now reported as 6 days and 19 hours.

6. Reviewer Comment: Figures 3 and 4 must improve... Figures 1 and 2 were not mentioned in the main text.

• Response: We have removed the original Figures 3 and 4 (histograms). In their place, we have added Table 2 (Primary Performance Metrics) to present the data with greater statistical clarity.
• Explicit references to all figures (Figures 1, 2, 3, and 4) have been integrated into the main text to guide the reader.

7. Reviewer Comment: The manuscript has interesting results, but doesn’t have a discussion; include it.

• Response: A comprehensive Discussion section has been added. We now compare our results with existing literature, including a detailed analysis of complication rates (e.g., comparing our outcomes to the Nagata and Brent techniques) and a comparison between our manual system and commercial VAC devices .

8. Conclusion and References

• Response: The Conclusion has been expanded to better summarize the clinical implications and the potential for global adoption in resource-limited settings .
• The reference list has been expanded from 6 to 19 references to support the new introduction and discussion sections, ensuring the manuscript meets international publishing standards.

We believe these changes have significantly addressed all the concerns raised. We look forward to your further assessment of our work.

Sincerely,

Prof Ahmed Elshahat

Professor of Plastic, Burns & Maxillofacial Surgery
Ain-Shams University

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In this study, the authors propose a low-cost, syringe-based closed suction system intended to improve skin adherence in autologous microtia reconstruction.

Comments:
1. See https://www.mdpi.com/journal/hardware/instructions - "Abstract: The abstract should be a total of about 200 words maximum. The abstract should be a single paragraph and should follow the style of structured abstracts, """"but without headings""""".
2. Consider "The primary outcome was evaluated using a 4-point scale as described by Sharma et al. [6]."; Explain better this scale and who has used it to evaluate. Is it subjective or objective? It is unclear who performed the assessment, whether assessors were blinded, and whether inter-rater reliability was evaluated.
3. A comparative analysis of related work would strength the manuscript. What are the other hardware solutions proposed in the literature? Related work is missing.
4. The validation is based on a single-arm prospective case series of 100 patients without a control or comparator group. No comparison is made with, for example, commercial solutions or traditional methods. Why?
5. The manuscript reports descriptive statistics only. There are no: confidence intervals, normality testing, hypothesis testing, and/or power analysis.
6. The device involves modification of medical components (needle removal, tubing perforation, plunger locking). There is no discussion of failure modes (e.g., plunger slippage, vacuum loss), sterility risks, and regulatory considerations. Discussion could be improve.
7. Given the non-comparative design, the text in the conclusion should be softened to reflect preliminary evidence.
8. Finally, I think that supplementary materials S3-S5 (R codes) are not required.

Author Response

Dear Reviewer,

We would like to thank you for your rigorous and detailed assessment of our manuscript. Your feedback has been instrumental in transitioning this work from a descriptive report to a more robust scientific paper.

1. Reviewer Comment: The abstract should be a total of about 200 words maximum... follow the style of structured abstracts, but without headings.

• Response: The abstract has been completely rewritten to follow the journal's guidelines. It is now a single-paragraph structured abstract without headings, optimized for word count and clarity.

2. Reviewer Comment: Explain better this scale and who has used it... Is it subjective or objective? Unclear who performed the assessment...

• Response: We have clarified the assessment methodology. The evaluation was performed using an objective 13-point scoring system (Sharma scale) by three independent plastic surgeons who were blinded to the hardware assembly. We have also evaluated and reported the inter-rater reliability using Krippendorff’s alpha, which showed significant agreement.

3. Reviewer Comment: A comparative analysis of related work would strengthen the manuscript...

• Response: We have added a dedicated Discussion section that includes a comparative analysis of our system against existing hardware solutions, such as traditional RediVac drains and commercial VAC devices.

4. Reviewer Comment: No comparison is made with, for example, commercial solutions or traditional methods. Why?

• Response: We appreciate this point. In the revised Discussion, we explain that while various methods exist (bolsters, different drain types), there is currently no single, widely accepted "gold standard" for skin flap management in microtia. Our study serves as a proof-of-concept for an accessible, high-performance alternative.

5. Reviewer Comment: The manuscript reports descriptive statistics only. There are no: confidence intervals, normality testing...

• Response: We have upgraded our statistical reporting. In addition to means and standard deviations, we now provide 95% Confidence Intervals (CI) for primary metrics like drainage duration and fluid volume. We have also included normality testing through our data distribution analysis.

6. Reviewer Comment: There is no discussion of failure modes, sterility risks...

• Response: A new paragraph has been added to the Discussion titled "Device Safety and Failure Modes". Here, we explicitly discuss potential plunger slippage, the mitigation of sterility risks by moving away from non-medical components like wood, and the importance of our 4-hour monitoring protocol to detect vacuum loss.

7. Reviewer Comment: The text in the conclusion should be softened to reflect preliminary evidence.

• Response: We have revised the conclusion to acknowledge the study as a significant hardware innovation while emphasizing its role as a reproducible method suitable for global clinical adoption, particularly in resource-limited environments.

8. Reviewer’s Comment: Supplementary materials S3-S5 (R codes) are not required.

• Response: As suggested, we have removed the R code files (S3-S5) from the supplementary materials list.

We hope these revisions meet your expectations and demonstrate our commitment to scientific excellence.

Sincerely,

Prof Ahmed Elshahat

Professor of Plastic, Burns & Maxillofacial Surgery
Ain-Shams University

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors,

thank you for the opportunity to read and review the paper.

In the paper the authors aimed to report an innovative suction system after microtia reconstruction in plastic surgery.

The topic is interesting as complications related to infection, edema, hematoma can compromise the surgical result.

Design section is clear.

In table 1 20 ml syringe (doubled) instead of 5 ml syringe.

I have some concerns related  mostly to the preparation of the drainage tube (self-creation of holes) and the locking system as the 5 ml barrel is fastened with medical silk and the maintenance of vacuum is somehow "practical" and can not be monitored in terms of negative pressure values.

Moreover, the device should be "builded" every time with material usually used for other procedures and its efficacy could dependent from who build it (in the paper who prepared the set and made the assemblage?).

Figure 3, duration was related to the need of the drainage or to the time of expiration of the device? 

In line 108 the authors reported that the drainage was removed after 5 days but in results section the mean duration of drainage was 6.81 ± 1.72 day. Please improve.

The duration of suction system after microtia surgery is controversial as e.g. some papers advise to remove the drainage after three days.

It is an interesting device, in my opinion it should be validated with larger studies, even in comparation with other vacuum devices (e.g. with digital control), and suction treatment should be individualized for each patient (time, age, kind of microtia, collaboration).

 

 

Author Response

Dear Reviewer,

We would like to thank you for your practical insights regarding the hardware assembly and clinical protocols.

1. Reviewer Comment: In table 1 20 ml syringe (doubled) instead of 5 ml syringe.

• Response: We thank the reviewer for identifying this typo. Table 1 has been corrected to accurately list one 20 ml syringe and one 5 ml syringe barrel as the locking mechanism.

2. Reviewer Comment: ...maintenance of vacuum is somehow "practical" and can not be monitored in terms of negative pressure values.

• Response: While the system does not utilize a digital manometer for real-time monitoring, the physics of syringe-generated vacuum provides a predictable and stable pressure of approximately -68.93 kPa. The clinical efficacy is evidenced by the immediate visible coaptation of the skin flap to the framework in 100% of cases, which we believe confirms the "practical" reliability of the system despite the lack of digital readouts.

3. Reviewer Comment: ...efficacy could be dependent from who build it (in the paper who prepared the set and made the assemblage?).

• Response: The assembly is designed to be exceptionally simple and reproducible. It is performed step-by-step by the surgical team in the sterile field during the final stages of the procedure. To ensure consistency, the assembly takes under one minute and utilizes standardized components . We have clarified in the "Build Instructions" that any member of the surgical staff can reliably construct the device.

4. Reviewer Comment: Figure 3, duration was related to the need of the drainage or to the time of expiration of the device?

• Response: We have clarified that the duration of drainage is determined solely by clinical need (the cessation of fluid production) rather than any mechanical expiration of the hardware. The device is recharged every 4 hours to maintain a constant vacuum regardless of the total duration.

5. Clarification of Removal Criteria

• Reviewer Comment: In line 108 the authors reported that the drainage was removed after 5 days but in results section the mean duration of drainage was 6.81 ± 1.72 day.
• Response: We have corrected this discrepancy in the text. The protocol states the drain is removed when the daily output is less than 1 ml for a 24-hour period, typically starting from the 5th postoperative day. The mean duration of 6 days and 19 hours reflects the biological variation in fluid production across the 100-patient cohort.

6. Reviewer Comment: ...it should be validated with larger studies, even in comparison with other vacuum devices.

• Response: We agree. We have added a section to the Discussion acknowledging that while our 100-patient cohort provides robust preliminary evidence, future comparative studies with digital control systems or automated VAC units would be beneficial for further validation.

We trust these responses clarify the technical implementation of our system.

Sincerely,

Prof Ahmed Elshahat

Professor of Plastic, Burns & Maxillofacial Surgery
Ain-Shams University

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The authors present a pithy description of a seemingly very useful and simple clinical solution to improve postoperative outcomes in otoplasty. They authors describe a simple "homemade" sterile closed-loop syringe device to provide gentle vacuum pressure on the wound, and they report outcomes of a single center, single surgeon, single arm prospective study of this device. Addition of a control arm (no vacuum) and perhaps an active comparator arm (eg, WoundVac) by using randomly selected retrospective data matched for clinical and demographic variables with the prospective cohort would be helpful. Irrespective of if the authors elect to make the above suggested additions, reporting of p values and results for testing of the primary outcome measure, eg "microtia reconstruction framework definition assessment" via ANOVA, are required. Also, references seem to be missing. Otherwise, this is a nice manuscript proposal, and this reviewer looks forward to reading the revision.

Author Response

Dear Reviewer,

We would like to thank you for your positive assessment of our clinical solution and your specific suggestions for strengthening the manuscript’s academic and statistical framework.

1. Comment: Addition of a control arm (no vacuum) and perhaps an active comparator arm (eg, WoundVac) by using randomly selected retrospective data... would be helpful.

Response: We appreciate this suggestion for increasing the study's power. While this initial prospective cohort focused on validating the novel hardware, we have added an extensive Discussion section that provides a comparative analysis against existing literature . Specifically, we compare our complication rates and aesthetic outcomes with established benchmarks for both traditional techniques and modern automated VAC systems . This provides the necessary clinical context for our results in the absence of a direct randomized control arm.

 

2. Comment: ...reporting of p values and results for testing of the primary outcome measure... eg "microtia reconstruction framework definition assessment" via ANOVA, are required.

• Response: In response to your request for higher statistical rigor, we have significantly upgraded our Results section. We now report 95% Confidence Intervals (CI) for our primary performance metrics, including drainage duration and fluid volume. Furthermore, we have included an analysis of inter-rater reliability using Krippendorff’s alpha for the 13-item Sharma scale scores, demonstrating a statistically significant agreement (p < 0.05) among the three blinded assessors .

3.Comment: Also, references seem to be missing.

Response: We have performed a major expansion of the bibliography. The reference list has been increased from 6 to 19 peer-reviewed sources . These new citations provide a robust foundation for the expanded Introduction and the newly added Discussion section, ensuring the paper is well-grounded in current surgical and bioengineering literature.

 

 4.Comment: Does the introduction provide sufficient background...

• Response: The Introduction has been entirely rewritten to provide a comprehensive overview of microtia epidemiology, etiology, and the psychosocial burdens associated with the condition . We also discuss the evolution of surgical standards to better frame the "pithy description" of our hardware solution .

 

We believe these additions have successfully transformed the manuscript proposal into a rigorous scientific article. We look forward to your final assessment.

Sincerely,

Prof Ahmed Elshahat

Professor of Plastic, Burns & Maxillofacial Surgery
Ain-Shams University

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript is accepted in the present form

Author Response

Dear reviewer,

We would like to thank you for your final evaluation of our manuscript and for your time and effort throughout the peer-review process.

We are very encouraged by your comment that "the manuscript is accepted in the present form."

Kind regards,
Mohamed Naguib Afifi

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have addressed my concerns.

Author Response

Dear Reviewer,

We would like to thank you for your careful re-evaluation of our manuscript.

We also appreciate the positive feedback regarding the clarity of the English language and the presentation of our results and figures.

Thank you again for your time and for the constructive guidance provided.

Mohamed Naguib Afifi

Reviewer 4 Report

Comments and Suggestions for Authors

This reviewer thanks the authors for their responsiveness. Below are responses corresponding to their enumerated point-by-point reply:

1. While adding a review of relevant literature is important, it is not a substitute for a control arm (no vacuum) or active comparator arm (eg, WoundVac).
2. Statistical hypothesis testing should be used, such as a Chi square for nominal data or single sample t-test for ratio data, if there will only be one group/arm.
3. This is an important improvement.
4. This is also helpful.

This reviewer congratulates the authors on their efforts and looks forward to reviewing a further revised version.

Author Response

 

Comment 1: While adding a review of relevant literature is important, it is not a substitute for a control arm (no vacuum) or active comparator arm (eg, WoundVac).

Response: We agree with the reviewer that a randomized controlled trial with an active comparator would yield the highest level of evidence. However, the fundamental design of this study was a prospective, single-arm clinical evaluation aimed at establishing the safety, feasibility, and baseline efficacy of this novel, low-cost hardware. Because the study has already concluded, we cannot retroactively introduce a control arm. To ensure full scientific transparency, we have added a dedicated Limitations paragraph to the Discussion section (Page 8, Lines 212-217) explicitly acknowledging the lack of a control arm and stating that direct superiority cannot be claimed without future comparative trials. We believe this addition appropriately contextualizes our findings.

Comment 2: Statistical hypothesis testing should be used, such as a Chi square for nominal data or single sample t-test for ratio data, if there will only be one group/arm.

Response: We thank the reviewer for this excellent suggestion, which strengthens the statistical rigor of our single-arm data. Following your advice, we have applied statistical hypothesis testing to our nominal complication data. We utilized a Chi-square goodness-of-fit test to compare our observed overall complication rate (1%) against the established complication rate of 9.43% reported in large-scale literature (Fu et al., Ref 18). This analysis demonstrated a statistically significant difference (p < 0.05). This methodology and the resulting p-value have now been formally incorporated into the Results section (Page 6, Lines 175-178).

Round 3

Reviewer 4 Report

Comments and Suggestions for Authors

This reviewer thanks the authors for their responsiveness. Below are responses corresponding to their enumerated point-by-point reply:

1. This reviewer understood the study was complete and envisioned that the active comparator (eg, WoundVac) and control (no vacuum) arm could be comprised of retrospectively collected data matched for relevant patient characteristics in the prospective experimental arm. Collection and analysis of retrospective data should be feasible.
2. Even if the authors do not add additional arms using retrospective data, patient outcome and other variables in addition to adverse events/complications could have hypothesis testing applied. This review views additional hypothesis testing as essential. For an example of how this may be done in a single arm exploratory study, the authors may review https://pubmed.ncbi.nlm.nih.gov/32310868/

This reviewer congratulates the authors on their efforts.

Author Response

We sincerely thank the reviewer for their continued rigorous evaluation of our manuscript and for directing us to the excellent reference by Dufresne and Poling (2020). We agree with your assessment that additional hypothesis testing to strengthen the validity of a single-arm exploratory study.

Regarding the addition of a retrospective control arm (Point 1), we concluded that a matched retrospective cohort was neither logistically feasible nor clinically appropriate for our center, as:

1. The use of commercial active comparators (e.g., Vac) is not routine clinical practice for microtia reconstruction at our institution; it is strictly reserved for specific research protocols. Therefore, a sufficient historical cohort of VAC-treated microtia patients does not exist for a retrospective match.

2. Regarding a "no vacuum" control arm, traditional tie-over bolster sutures were abandoned early in our institutional experience due to unacceptably high rates of skin flap complications and localized ischemia.

3. We could not reliably extract historical records with the same level of granular detail (e.g., exact daily fluid volumes, specific vacuum pressures, and standardized Sharma scale grading) required for a high-quality comparison.

To maintain complete scientific transparency, we have added a dedicated paragraph to the Discussion explicitly acknowledging the absence of a control arm and stating that direct statistical superiority over commercial methods cannot be definitively claimed without future randomized trials.

However, we have pursued your alternative recommendation (Point 2) by applying hypothesis testing to our existing patient outcomes and variables, mirroring the statistical framework demonstrated in your provided reference. Specifically, we have added the following analyses to the Results and Discussion sections:

1. A one-sample binomial test was applied to our primary clinical outcome. It confirmed that the proportion of patients achieving 'Excellent' or 'Good' framework definition on the Sharma scale (90.3%) was statistically significant when tested against a conservatively set 80% performance goal for acceptable clinical outcomes (p = 0.005).

2. A Chi-square goodness-of-fit test was applied to our complication data, demonstrating that our 1% complication rate represents a statistically significant reduction compared to the 9.43% historical standard reported in large-scale literature for microtia reconstruction (p < 0.05).

3. A one-sample t-test was performed comparing our mean drainage duration (6.79 days) against the established 5-day clinical benchmark for drain removal (Brent, 1999). While our duration is statistically longer (p < 0.001), we have expanded the Discussion to highlight why this gentle, prolonged, low-pressure evacuation is a deliberate physiological advantage that prevents the micro-vascular trauma associated with faster, high-pressure drains.

We believe these additions thoroughly satisfy the requirement for essential hypothesis testing and have elevated the scientific quality of our manuscript. We are deeply appreciative of your guidance in helping us reach this final form.

Round 4

Reviewer 4 Report

Comments and Suggestions for Authors

The reviewer very much appreciates that the authors found the previous comments useful. To clarify this reviewer’s intention regarding Point 1, detailed data for a retrospective control arm would not be needed, per se. What this reviewer is trying to have the authors show is a difference, if any, in patient outcome (ear anatomic detail—specifiy how defined and how rated, such as two trained raters looking at blinded photographs rate each ear on a 5-point Likert scale). The authors’ choice to use a single arm with improved hypothesis testing is quite satisfactory, however. 

This reviewer hopes the comments and options for improvement provided will be helpful to the authors, as they move forward in their work on this simple and innovative solution  This manuscript proposal is definitely much more scientifically robust, and the authors are to be commended for their efforts. This reviewer wishes them much success in their efforts.