The Correlation of Carpal Tunnel Pressure with Clinical Outcomes following Ultrasonographically-Guided Percutaneous Carpal Tunnel Release

Round 1

Reviewer 1 Report

Dear Authors,

the evaluation of the existent correlation between CTP and clinical presentation is interesting. The manuscript is well written. I have some concerns.

 

1)    Statistical analysis: Since 37 hands are few, it may be reasonable to use non-parametric tests in your analysis avoiding T test or Pearson correlation analysis. Alternatively, you can report the results of the Kolmogorov-Smirnov test assessing the normal distribution of the data.

 

2)    Nerve conducting study (EDG) ?: Electrodiagnostic studies (EDX) or nerve conduction studies (NCS). Please correct it along the manuscript.

 

3)    Page 2 Ln 83: “According to EDG, the patients with CTS were classified as mild, moderate, and severe based on the guidelines of the American Association of Electrodiagnostic Medicine”. It would be very useful to report the NCS data for each category. Please discuss why no NCS data were reported. Since mild CTS grade means the only damage of the sensitive fibers, these patients may have a lesser preoperative CTP rather than moderate and severe.

 

4)    Pag 5 Ln 193-195: I agree with this correlation. Indeed, an higher preoperative CTP means a higher damage of the median nerve thus indicating a higher CSA and prominent symptoms. For these reasons, I do not agree with the result of a non-correlation between preoperative CTP and severity of CTS. Of note, you should perform a correlation between CMAP (compound motor action potential)/ SNAP (sensory nerve action potential) parameters and CTP and CSA. A little number of hands may be the reason underlying the lack of correlation between CTP and CTS severity. Please discuss this point.

 

5)    Results 3.4 Postoperative improvement trajectory and 3.5 Predictors for trajectory pattern. “The “Fast recovery” group was associated with significantly higher pre-/post-operative CTP, as compared to the “Gradual recovery” group.”

The preoperative CTP positively correlated with preoperative BCTQ-S/ BCTQ-F/BCTQ-Total scores therefore it is reasonable that a marked reduction in post-operative CTP (table 3: -24mmHg gradual recovery vs -35mmHg Fast recovery) results in symptoms improvement. However, in the group fast recovery a higher percentage of patients belong to severe CTS. It would be expected the opposite result: since severe CTS means a dramatic damage of the median nerve, a recovery in this phase would be more difficult. Also in this case, reporting the NCS data and perform the analysis using  CMAP and SNAP rather than electrodiagnostic grade may be helpful to clarify the relationship between median nerve damage, CTP and recovery rate.

 

6) I suggest two lecture in which you can find some critical point of the existing classification of the CTS and anatomical variants that may both affect the relationship between nerve damage and NCS. For example, in normal subjects Martin-Gruber Anastomosis type 3 may simulate CTS whereas in patients with CTS it may contribute to underestimate CTS (prolonged DML and normal or higher CV). The underestimation of CTS grade may results in a poor outcome than expected after decompression. Hence, the importance to report the NCS data in your manuscript. 

-    “Evaluation of the Existing Electrophysiological Severity Classifications in Carpal Tunnel Syndrome, Journal of Clinical Medicine 2022”

-   Median-to-Ulnar Nerve Communication in Carpal Tunnel Syndrome: An Electrophysiological Study, Neurol Int 2021” 

 

Thank you for response

 

Kind regards

Author Response

Reviewers' comments:

Reviewer #1: Statistical analysis: Since 37 hands are few, it may be reasonable to use non-parametric tests in your analysis avoiding T test or Pearson correlation analysis. Alternatively, you can report the results of the Kolmogorov-Smirnov test assessing the normal distribution of the data.

Response: Thank you for your comment. We completely agree with your opinion. According to your suggestion, non-parametric tests were used to perform the statistical analyses if the normal distribution of data was not reached. Therefore, the differences in various continuous outcome variables between pre- and post-operation at various points in time during followed were assessed using the Wilcoxon Signed-rank test (Table 1). Spearman rank correlation coefficients was used to determine the strength and direction of associations between variables, and the correlation between the preoperative CSA and CTP using Pearson correlation test because data were considered to be normally distributed by the Kolmogorov-Smirnov test (Table 2). All the results associated with statistical testing remain unchanged except the correlation between preoperative CTP and the duration of symptoms. We have revised the description of statistical analysis in the Method section and the footnotes of Table 1 and Table 2. (Page 4, Line 154-165 & Page 5, Line 196 & Page 6, Line 208-210)

Nerve conducting study (EDG) ?: Electrodiagnostic studies (EDX) or nerve conduction studies (NCS). Please correct it along the manuscript.

Response: Thank you for your comment. We have revised our terminology and stated “nerve conduction study (NCS)” throughout the manuscript. (Page 2, Line 55, 63, 80, 83, 84 & Page 5, Line 180, 182, 205 & Page 6, Line 231 & Page 8, Line 283, 288, 311, 314, 316 & Page 9, Line 319, 321, 339)

Page 2 Ln 83: “According to EDG, the patients with CTS were classified as mild, moderate, and severe based on the guidelines of the American Association of Electrodiagnostic Medicine”. It would be very useful to report the NCS data for each category. Please discuss why no NCS data were reported. Since mild CTS grade means the only damage of the sensitive fibers, these patients may have a lesser preoperative CTP rather than moderate and severe.

Response: Thank you for your constructive suggestions. In present study, we aimed to evaluate the correlation between the carpal tunnel pressure (CTP) and the clinical presentations. We apology for our unclear statement in the diagnosis of CTS using NCS and the corresponding classification of CTS. In classification of NCS grade, there were many classification systems reported. We originally classified the 37 patients based on the NCS cutoff values according to a previous study by Kuo et al [1]. Thank you for your comments. We revisit our data and re-classify our patients according to the most common criteria, the guidelines of the American Association of Electrodiagnostic Medicine [2]. Therefore, there were changes of patient numbers in mild, moderate, and severe NCS grade. We have revised it in the Method section as the following: “The electrophysiological diagnosis of CTS using NCS was established based on the guidelines of the American Association of Electrodiagnostic Medicine [16]. According to the results of NCS, the severity of CTS was classified as mild, moderate, and severe [16].” (Page 2, Line 82-85) and in the Result section. (Page 3, Line 179-181) Furthermore, according to your suggestions, we recorded the CMAP (compound motor action potential) and SNAP (sensory nerve action potential) data and updated the results of the pre-operative CTP, SNAP, and CMAP in each category as the supplementary Table 1. Based on the current severity of CTS, there is no significant difference in pre-operative CTP among groups. For SNAP and CMAP, there were significant between-group differences in the moderate and severe groups (Please see the attachment for supplementary Table 1).

Page 5 Ln 193-195: I agree with this correlation. Indeed, an higher preoperative CTP means a higher damage of the median nerve thus indicating a higher CSA and prominent symptoms. For these reasons, I do not agree with the result of a non-correlation between preoperative CTP and severity of CTS. Of note, you should perform a correlation between CMAP (compound motor action potential)/ SNAP (sensory nerve action potential) parameters and CTP and CSA. A little number of hands may be the reason underlying the lack of correlation between CTP and CTS severity. Please discuss this point.

Response: Thank you for your valuable comments. We have evaluated the correlation between CMAP/ SNAP parameters and CTP according to your suggestion. The results showed no significant correlation between CMAP/SNAP parameters and the preoperative CTP. We have added these findings in the Results section and Table 2 (Page 5, Line 203-205). We also acknowledged that the limited patient number might lead to no significant correlation between CMAP/SNAP parameters and the preoperative CTP. We have stated this as one of our study limitations: “Theoretically, higher CTP might lead to more severe damage to the median nerve that is presented with worse NCS results including severity grade, SNAP and CMAP. In the current study, our results failed to demonstrate the correlation between NCS parameters and the preoperative CTP. In addition to the individual variations of CTP in symptomatic CTS, the limited patient number is another possible reason leading to the insignificant results. Thus, a larger scale study is necessary to confirm our findings.” (Page 8, Line 318 – Page 9, Line 324)

Results 3.4 Postoperative improvement trajectory and 3.5 Predictors for trajectory pattern. “The “Fast recovery” group was associated with significantly higher pre-/post-operative CTP, as compared to the “Gradual recovery” group.”

The preoperative CTP positively correlated with preoperative BCTQ-S/ BCTQ-F/BCTQ-Total scores therefore it is reasonable that a marked reduction in post-operative CTP (table 3: -24mmHg gradual recovery vs -35mmHg Fast recovery) results in symptoms improvement. However, in the group fast recovery a higher percentage of patients belong to severe CTS. It would be expected the opposite result: since severe CTS means a dramatic damage of the median nerve, a recovery in this phase would be more difficult. Also in this case, reporting the NCS data and perform the analysis using CMAP and SNAP rather than electrodiagnostic grade may be helpful to clarify the relationship between median nerve damage, CTP and recovery rate.

Response: Thank you for your comment. We agree with your opinion that severe CTS is expected to represent a dramatic damage of the median nerve and the neurophysiological recovery in such patients would be more difficult. However, the recovery pattern stated in this study is defined as the recovery of function and symptom using the BCTQ score in patients following percutaneous UCTR. According to your suggestions, we have updated the SNAP and CMAP data in addition to the NCS severity grade in the Results section (Page 5, Line 181-183, 203-205), Table 2, Table 3, and supplementary Table 1. There is no significant difference in NCS data including severity grade, SNAP, and SMAP between two trajectory groups. That is, according to our results, clinical recovery is not related to the NCS results. Rivlin et al [3] also reported the postoperative improvement after CTR overall was also not statistically different between groups with differing electrodiagnostic study severity.

I suggest two lecture in which you can find some critical point of the existing classification of the CTS and anatomical variants that may both affect the relationship between nerve damage and NCS. For example, in normal subjects Martin-Gruber Anastomosis type 3 may simulate CTS whereas in patients with CTS it may contribute to underestimate CTS (prolonged DML and normal or higher CV). The underestimation of CTS grade may results in a poor outcome than expected after decompression. Hence, the importance to report the NCS data in your manuscript. 

-   “Evaluation of the Existing Electrophysiological Severity Classifications in Carpal Tunnel Syndrome, Journal of Clinical Medicine 2022”

-   Median-to-Ulnar Nerve Communication in Carpal Tunnel Syndrome: An Electrophysiological Study, Neurol Int 2021” 

Response: Thank you for your valuable comment. As the above response to your comments, we have updated two NCS data, SNAP and CMAP, and related analyses in our revised manuscript. Furthermore, we also made a statement reflecting your critical comment and the two important references: “Clinically, various NCS severity classifications do not always accurately reflect the severity of CTS [35]. Martin-Gruber anastomosis, the normal anatomical innervation variant, might lead to underestimation of CTS severity in NCS [36]. Furthermore, postoperative recovery after CTR has been reported to be independent of the electrodiagnostic study severity [14]. Our results also indicated that the NCS results is not related to the postoperative recovery pattern.” (Page 8, Line 311-316)

※Please see the attachment for references

Author Response File: Author Response.docx

Reviewer 2 Report

 

Dear Editor and Authors,

Thank you for the opportunity to review the manuscript entitled “The correlation of carpal tunnel pressure with clinical outcomes following ultrasonographically-guided percutaneous  carpal tunnel release.” The authors evaluated the correlation between carpal tunnel pressure (CTP) and the clinical presentations, and  explored the possible predictors for the postoperative recovery pattern in patients with carpal tunnel syndrome. They included 37 patients and concluded that preoperative CTP was well correlated with the clinical presentations and might be a useful predictor for the postoperative clinical recovery pattern. The study is interesting well-designed and should be of interest of the Journal readers.

I have some additional minor suggestions:

-        Introduction: line 52, explain abbreviations when used for the first time (BCTQ scores), electrodiagnostic grade of nerve conducting study (EDG) – also explain the exact meaning of the abbrev.

-        Line 77 – should be  “consecutive patients”

-        Explain the use of the Stryker device for CT pressure measurement (it should be explained what is it originally for and the innovative use here should be highlighted)

-        Explain what techniques you offer to your patients and when you qualify the patient for percutaneous UCTR versus open technique.

 

Author Response

Reviewers' comments:

Reviewer #2: Introduction: line 52, explain abbreviations when used for the first time (BCTQ scores), electrodiagnostic grade of nerve conducting study (EDG) – also explain the exact meaning of the abbrev.

Response: Thank you for your comment. We have revised the “BCTQ scores” into “Boston Carpal Tunnel Questionnaire” and “electrodiagnostic grade of nerve conducting study (EDG)” into “the severity of nerve conduction study (NCS)” according to your suggestion. (Page 2, Line 51-52)

Line 77 – should be  “consecutive patients”

Response: Thank you for your comment. We have revised it according to your suggestion. (Page 2, Line 77)

Explain the use of the Stryker device for CT pressure measurement (it should be explained what is it originally for and the innovative use here should be highlighted)

Response: Thank you for your comment. The Stryker device was originally designed for intra-compartmental pressure measurement in compartment syndrome, as what we stated in the Methods section: “….via the pressure measurement system (Intra-Compartmental Pressure Monitor System,…” (Page 2, Line 89-90) The application of this Stryker device for CTP measurement had been reported by Sanz et al [1]. Thank you for your valuable suggestion. We have added this reference following this equipment description for the off-label use. (Page 2, Line 91)

Explain what techniques you offer to your patients and when you qualify the patient for percutaneous UCTR versus open technique.

Response: Thank you for your comment. We described the UTCR technique in the Method section as: “After the preoperative CTP measurement, the entire transverse carpal ligament was released by an ultrasound-guided operation under a local anesthesia, similar to our previous study [18-20] (Fig.1e)” (Page 3, Line 107-109). In our practice, the percutaneous UCTR have been our standard surgical release method for idiopathic CTS including revisional surgery [2]. The safety and effectiveness of percutaneous UCTR have been studied for years [3-6]. To date, more than 4000 percutaneous UTCR procedures were performed by our team [2].

※Please see the attachment for references

Author Response File: Author Response.docx