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. 2021 Jun 4;16(6):e0252716. doi: 10.1371/journal.pone.0252716

Comparison between femoral block and PENG block in femoral neck fractures: A cohort study

Céline Allard 1, Emmanuel Pardo 1,2, Christophe de la Jonquière 1, Anne Wyniecki 1, Anne Soulier 1, Annibal Faddoul 1, Eileen S Tsai 3, Francis Bonnet 1,2, Franck Verdonk 1,2,3,*
Editor: Robert Jeenchen Chen4
PMCID: PMC8177466  PMID: 34086782

Abstract

Background

Regional analgesia is worth performing in the multimodal postoperative management of hip fracture (HF) because it reduces hospital morbidity and mortality. The aim of this study is to compare the efficacy and side effects of the recently described “Pericapsular Nerve Group (PENG) Block” with those of the femoral block, which is considered the standard of care for postoperative pain control after femoral neck fracture.

Materials and methods

We conducted a comparative observational study at a university hospital (Saint Antoine Hospital, Sorbonne University, Paris, France), where the PENG block was introduced in August 2019. We include all patients from June to October 2019, who were coming for femoral neck fractures and who had an analgesic femoral block or PENG block before their surgery. The primary outcome was the comparison of cumulative postoperative morphine consumption 48 hours after surgery.

Results

Demographics, medical charts, and perioperative data of 42 patients were reviewed: 21 patients before (Femoral group) and 21 patients after the introduction of PENG block (PENG group) in clinical practice. Thirteen total hip arthroplasties (THA) and eight hemi arthroplasties (HA) were included in each group. Demographics were also comparable. The median, postoperative, morphine equivalent consumption at 48 hours was 10 [0–20] mg and 20 [0–50] mg in Femoral and PENG groups respectively (p = 0.458). No statistically significant differences were found in postoperative pain intensity, time to ambulation, incidence of morphine-related side effects, or length of hospital stay. The postoperative muscle strength of the quadriceps was greater in the PENG group than in the Femoral group (5/5 vs. 2/5, p = 0.001).

Conclusion

In the management of hip fractures, PENG block is not associated in our study with a significant change in postoperative morphine consumption, compared to femoral block. However, it does significantly improve the immediate mobility of the operated limb, making it appropriate for inclusion in enhanced recovery programs after surgery.

Introduction

The incidence of femoral neck fracture is 330/10000 per year in Europe. It is increasing every year due to the ageing of the population. By 2050, it is estimated that worldwide, more than 4.5 million patients per year will suffer a femoral neck fracture. [1] The healthcare cost is estimated to be $17 billion per year in the United States, related not only to hospital stay but also to rehabilitation, management of complications, and associated disability [2]. Mortality related to HF in patients aged 55 years and more is estimated between 4% and 16% at one month and between 11% and 43% at one year after surgery [35]. Associated morbidity is also important with a significant loss of autonomy at one year in 50% of patients [6].

A recent Cochrane review pointed out a reduced risk of postoperative complications associated with the use of regional anesthesia (RA), a shorter delay to mobilization, and a reduced morphine consumption in hip fractures, reinforcing the value of postoperative pain control as part of a multimodal management [7].

Innervation of the hip joint depends on the femoral, the obturator, and the lateral cutaneous nerves of thigh. None of the RA technique is able to block simultaneously these three nerves and their corresponding endings, even the “3-in-1” block which can theoretically block all the three cited nerves by only one injection does not often reach the territory of the obturator nerve [8]. We usually consider the femoral nerve block as one of a standard of care for hip fractures [7]. But this bloc relieves pain only 69% of the patients with HF after 30 min [9]. In addition, it induces a motor block of the quadriceps muscle after being performed, provoking a potential delay in reeducation. A recent anatomical study shows that the anterior hip joint capsule is mainly innervated by three nerves: the femoral nerve, the obturator nerve, and, inconsistently, the accessory obturator nerve, whose joint branches pass between the iliopubic eminence and the anteroinferior iliac spine [10].

A new block, the "Pericapsular Nerve Group (PENG) block" has been described and initially developed in 2018 by Giron-Arango et al [11]. This diffusion block could provide complete postoperative analgesia with the advantage of sparing the motor function of quadriceps. Case reports have described the efficacy of this block but no study has comparatively evaluated the efficacy of PENG block versus femoral block [1214].

The main objective of this study was to evaluate the first 48 postoperative hours of morphine consumption before and after the introduction of the PENG block for patients with femoral neck fractures in our institution. The secondary objectives were to compare the motor function of quadriceps muscle, the time to ambulation and the incidence of side effects related to morphine consumption.

Materials and methods

Details of study design

In our institution, since August 1st 2019, the PENG block has been used to patients scheduled for hip arthroplasty for femoral neck fracture (total hip arthroplasty (THA) and hemi arthroplasty (HA)) as the cornerstone of postoperative analgesic protocols, in combination with systemic analgesia. The standard of care was previously the use of femoral block associated with systemic non-opioid and opioid analgesics. In order to evaluate this practice, this observational, monocentric, data-based, comparative study compared analgesic effect and functional consequences of these two types of blocks over the two periods defined as “before” and “after” the PENG block implementation on consecutive patients who met the inclusion criteria.

Settings

Before the PENG block technique was introduced, all the anesthesiologists of the department received a theoretical and practical formation in an expert center during July 2019. We constituted two groups of patients: the “femoral block” (patients operated between June 1st 2019 and August 1st 2019 with a preoperative femoral block) and the “PENG block” study groups (between August 1st 2019 and October 31 2019).

Sample size estimation

The number of subjects to be included was calculated based on data from a local cohort from our center evaluating the postoperative characteristics of patients who underwent surgery for a fracture of the proximal femur. These data showed an average morphine consumption at 48 hours of 22 milligrams (± 8mg standard deviation). With regard to the literature [15, 16] published on the benefit of a locoregional analgesia in a context of hip fracture, we anticipated a 30% decrease in morphine consumption at 48 hours with the realization of a PENG block compared to a femoral block. With an alpha risk at 0.05 and a power of 80%, inclusion of 21 patients in each group (total number of 42 patients) was considered as sufficient to observe a significant difference between both groups.

Patients

Eligible patients were aged 18 years or older, were admitted for hip arthroplasty (THA or HA) for femoral neck fracture, and had undergone a preoperative RA technique (femoral block or PENG block). The exclusion criteria were patients with chronic pain before surgery (taking opioids), patients with multiple trauma, patients who could not assess pain reliably (dementia), and patients who had surgery under spinal or epidural anesthesia.

Data collection

Information related to early postoperative pain (analgesics consumed and dose, visual analog scale (VAS) on arrival and two hours after surgery (H2)) and functional recovery of the operated limb (mobility of the quadriceps defined by the medical research council (MRC) [17] scale rated from 0 to 5) have been collected. During the following postoperative period (from discharge from recovery room (RR) until 48h postoperatively), data collected concerned postoperative pain and postoperative rehabilitation (time to ambulation and length of hospital stay). All opioids administered in the early and late postoperative period were converted to oral morphine equivalent in mg. Data were collected using the electronic health records.

Primary and secondary outcomes

The primary outcome was the difference in cumulative morphine consumption at 48 hours after surgery. The secondary outcomes were postoperative VAS scores at 2 hours (H2), 12 hours (H12), 24 hours (H24) and 48 hours (H48) after surgery, proportion of VAS ≥ 4 at H24 and H48, immediate postoperative mobility of the operated limb quadriceps as defined by the Medical Research Council (MRC) scale [17] before discharge from RR (2 hours after the end of surgery), delay before first step, incidence of side effects related to the administration of morphine within 48 hours postoperatively and length of hospitalization.

Intervention

Briefly, patients were installed in the pre-anesthesia room and monitored. The blocks were performed by an experienced anesthesiologist, using a Mindray (Shenzen, China) model TE7 ultrasound scanner with a low frequency probe (5 MHz) for the PENG block (Figs 1 and 2) and a high frequency probe (12 MHz) for the femoral nerve block.

Fig 1. Small axis ultrasound view of the PENG block.

Fig 1

Using a 5 MHz abdominal probe. Images from St. Antoine Hospital, Paris.

Fig 2. PENG block realization.

Fig 2

Needle (★) approaching the psoas tendon. ▲ represents injection zone under the psoas tendon. AIIS: Anterior inferior iliac spine, PT: Psoas tendon, IPE: Iliopublic eminence, FA: Femoral Artery, FV: Femoral Vein.

The PENG block is a diffusion block on the anterior surface of the hip joint capsule. The target nerve branches of this block are the articular branches of the femoral nerve, the obturator nerve and the accessory obturator nerve, leading to no quadricipital motor block. Using a curvilinear low-frequency ultrasound probe (5 MHz) placed in a transverse plane over the Anterior Inferior Iliac Spine (AIIS) and rotated to be aligned with the pubic ramus, a 80 mm RA needle is inserted to inject 20ml of ropivacaine 3.5 mg/ml. The landmarks of this block are externally the AIIS, internally the iliopubic eminence, the psoas tendon anteriorly and the pubic ramus posteriorly.”

Regulatory and ethical aspects

In accordance with French law on biomedical research, this observational study obtained the approval of the Institutional Review Board “Comité d’Ethique de la Recherche en Anesthésie-Réanimation (CERAR, president Prof J.E. Bazin, May 6th 2020) under the reference number IRB 00010254–2020–078.

In order to guarantee the security of personal data, the investigators collected and integrated the information anonymously into a secure database in accordance with the French Commission Nationale de l’Informatique et des Libertés (CNIL) MR-004 methodology, and registered in the Assistance Publique–Hôpitaux de Paris (AP-HP) processing register under the number 20200512144042.

Patients consented via the websites of the institution (AP-HP and Hôpital Saint-Antoine) to the possible use of their data in research aimed towards improving the quality of care, and were informed about their rights and terms of objection. This information was also included for each patient in the hospital’s welcome booklet, which was given during administrative registration and presented at the end of the hospitalization reports.

Statistical methods

The variables were compared between the groups initially by univariate analysis, by Fischer and Chi2 exact tests for the qualitative variables and by Mann-Whitney or Student’s t-test according to the normality of the quantitative variables evaluated by a Shapiro-Wilk test. The tests were bilateral, with an alpha risk of α = 0.05. Results were given as median (25th-75th percentiles) for quantitative variables and as numbers of patients (percentage proportion) for qualitative variables. A p-value of less than 0.05 was considered significant.

The results are presented in the form of a box-plot diagram. The rectangle extends from the first quartile to the third quartile and is intersected by the median. The segments at the ends of the rectangle provide information on the extreme values.

The R Software (version 3.6.2 for Macintosh, GNU GPL licenses, The R foundation for statistical computing, Vienna, Austria) and the Rstudio interface Version 1.2.5033 (Boston, USA) were used to perform the statistical analyses.

Results

A total of 42 consecutive patients were included: 21 in the "Femoral block" group and 21 in the "PENG block" group. This population was predominantly female (61.9%, 26 patients), with a median age of 80.5 years Interquartile range (IQR) (70.2, 86.7). Preoperative characteristics (age, gender, ASA, weight/height, co-morbidities) were comparable in both groups. Surgical characteristics in each group were also comparable. There were 8 HA and 13 THA in each group. The surgical approaches performed were comparable between the two groups (Table 1).

Table 1. Patients demographics and surgical characteristics of patients in both groups.

Femoral block PENG block p-value
Sample size, n 21 21
Sociodemographic Characteristics
 Age (IQR) in years 77.0 (68.0, 84.0) 83.0 (71.0, 88.0) 0.38
 Male, n (%) 5 (23.8) 11 (52.4) 0.11
 BMI (IQR) in kg/m2 22.0 (20.0, 24.0) 23.1 (20.8, 24.9) 0.53
 Number of patients with AGIRG score > 3, n (%) 18 (85.7) 15 (71.4) 0.45
Surgical characteristics
 ASA classification, n (%)
  1 3 (14.3) 3 (14.3) 1.00
  2 9 (42.9) 10 (47.6)
  3 9 (42.9) 8 (38.1)
   Preoperative hemoglobin (IQR) in g/dl 13.6 (12.0, 14.3) 12.0 (11.4, 13.4) 0.14
   Time between trauma and surgery in hours (IQR) 39.0 (25.5, 46.5) 49.0 (25.0, 96.0) 0.25
   Preoperative VAS score (IQR) 4.5 (3.0, 8.5) 5.0 (3.0, 7.0) 0.61
   Number of patients who received preoperative morphine, n (%) 11 (52.4) 9 (42.9) 0.76
   Dose of preoperative morphine in mg (IQR) 18.0 (0.0, 50.0) 0.0 (0.0, 24.0) 0.15
   Number of patients who received stage 1 and/or 2 analgesics, n (%) 21 (100.0) 20 (95.2) 1.00
   Type of surgery
  HA, n (%) 8 (38.1) 8 (38.1) 1.00
  THA, n (%) 13 (61.9) 13 (61.9)
   Surgical approach
  Anterior, n (%) 12 (57.1) 13 (61.9) 0.43
  Posterior, n (%) 8 (38.1) 5 (23.8)
  Lateral, n (%) 1 (4.8) 3 (14.3)
   Administered doses of sufentanil in μg (IQR) 20.0 (15.0, 25.0) 20.0 (20.0, 25.0) 0.99
   Operating time in minutes (IQR) 101.0 (100.0, 120.0) 95.5 (88.5, 111.3) 0.17

Abbreviations: ASA, American Society of Anesthesiologist; AGIRG, Autonomy Gerontology Iso-Ressources Group; IQR, InterQuartile Range; VAS, Visual Analog Scale.

a = values are given as median 95% CI or percentages.

b = p-value compares Femoral block group versus PENG block group.

c = Fisher test was used to compare qualitative variable, t-test for quantitative variable.

No difference in cumulative morphine consumption at 48 hours was documented between the two groups (20 (0, 50) mg vs 10 (0, 20) mg, p = 0.478), in the PENG block and the femoral block groups respectively) (Fig 3).

Fig 3. Morphine consumption at different times: Before leaving the RR, 12 hours postoperatively (H12), 24 hours postoperatively (H24) and 48 hours postoperatively (H48).

Fig 3

Explanation of the figure: Box-plot diagram: The rectangle extends from the first quartile to the third quartile and is intersected by the median. The segments at the ends of the rectangle provide information on the extreme values.

The postoperative pain measured by the VAS showed no difference between the two groups, whatever the time of evaluation (Fig 4).

Fig 4. Postoperative VAS score at different times: Arriving in RR, before leaving the RR, 12 hours postoperatively (H12), 24 hours postoperatively (H24) and 48 hours postoperatively (H48).

Fig 4

Explanation of the figure: Box-plot diagram: The rectangle extends from the first quartile to the third quartile and is intersected by the median. The segments at the ends of the rectangle provide information on the extreme values.

Twenty-four hours after surgery, two (9%) patients in the "PENG block" group reported having a VAS ≥ 4, versus three (14%) patients in the "femoral block" group (p = 1.00).

Forty-eight hours after surgery, two (9%) patients in the "PENG block" group had an VAS ≥ 4 versus two (9%) patients in the "femoral block" group (p = 1.00).

Regarding the inferior limb motricity, there is a statistically significant difference between the two groups with a median MRC score mobility in the PENG block group rated at 5 IQR (4, 5) which means normal muscle strength of the quadriceps of the operated hip versus a median score of 2 IQR (2, 3.8) in the femoral block group (p<0.001).

There is no statistically significant difference in the time to first step, which is a median of two days (2, 3), between the groups (p = 0.88). The median length of hospitalization was 12 days (7, 12.5) in the PENG Block group versus 11 days (7, 15) in the femoral block group (p = 0.69).

There were 4 cases of Acute urine retention in the PENG block group versus 3 in the femoral block group (p = 1.00) and 2 cases of confusion in the femoral block group versus 6 in the PENG block group (p = 0.24). No statistically significant difference was observed in the incidence of these side effects.

Discussion

Main findings of the present study

This study documented that PENG block is comparable to femoral block for postoperative pain control but produces less quadriceps muscle block. The PENG block has been described very first in 2018 for preoperative management of femoral neck fracture [11]. We observed no significant difference in cumulative morphine consumption at 48 hours after surgery between the two groups. Similarly, no statistically significant difference was also found in pain scores, length of stay, or incidence of morphine-related adverse events. However, the immediate mobility of the operated limb quadriceps as measured by the MRC scale was different between the two groups, with an average mobility rating of 5 in the PENG block group versus 2 in the femoral block group (p < 0.001).

To our knowledge, this study is the first one to compare PENG block with another block (here, femoral block) in femoral neck fracture.

Implication and explanation of findings

Interestingly, while the analgesia area covered by the PENG block is theoretically larger than the one covered by the femoral block, by blocking other nerves involved in hip innervation such as the joint branches of the obturator and accessory obturator nerves, postoperative morphine consumption was not statistically different between the two groups. This can be explained by some points. First, the time from arrival at the emergency department on suspicion of a femoral neck fracture, and the surgery is particularly short in our center thanks to a dedicated care line for these patients, which is a critical point in limiting morphine requirements [18]. Da Costa et al. report a median time between emergency department management and surgery of 24.7 hours IQR (18.8,37.8) in our institution [19], which is significantly lower than what is observed in other countries (32.7 hours) [20]. Second, the mean morphine consumption is twice lower in the current study compared to previous studies [21]. This could be related to the population here described, as one of the exclusion criteria was severe dementia, which implies an impossibility to autonomously and reliably evaluate pain. A meta-analysis by Moschinski et al. [22] reports that postoperative morphine consumption could be significantly different in demented patients compared to non-demented. Finally, one of the other potential reasons for the absence of a statistically significant difference on the primary endpoint concerns the way the blocks were performed. Still, few studies relate the execution modalities of the PENG block as the possibility of a benefit from a continuous RA injection. Moreover, the local anesthetic (LA) solution used in the original PENG block study [11] consisted of 20 ml of bupivacaine, 2.5 mg/ml adrenaline, or 20 ml ropivacaine and 5 mg/ml adrenaline combined with dexamethasone. However, in the present study, the LA used was 20 ml ropivacaine at 3.5 mg/ml and without any adjuvants that could have prolonged the duration of postoperative analgesia.

One of the major theorical advantages of the PENG block—compared to femoral block—confirmed by this study is the preservation of quadricipital motricity of the operated limb from the immediate postoperative period. This is due to the diffusion zone of the PENG block, which includes only the articular branches of the femoral nerve, the obturator nerve, and the accessory obturator nerve [11], thus excluding the motor branches of the femoral nerve, which are anesthetized by the femoral block and are responsible for quadricipital motor innervation. In a previous study, Ghodki et al showed that only 13% of the 30 patients receiving femoral nerve block present a normal quadricipital motricity 12 hours after surgery and, more interestingly, that 17% of them still have muscle weakness 24 hours after surgery [23]. At the opposite, the PENG block, by allowing an intact mobility in the immediate postoperative period of the operated limb, would be synonymous with a reduction of the time to first step and even of the length of stay. This has not been demonstrated in this study, probably due to a lack of early mobilization by physiotherapists in our institution, in patients operated on with an HA or THA until 48 hours.

Limitations of the study

Finally, one of the limitations of this study is its monocentric and databased design and inter-operator variability, which therefore potentially leads to inconsistency in the efficacy of the RA performed, thus diminishing the power of the study. In the study by Mistry et al [24], it is reported that the injection zone of the local anesthesia (LA) in the PENG block is very important and would influence the effectiveness of the block. Optimal injection is reflected in the ultrasound vision of a medial diffusion towards the iliopubic eminence.

Even if the sample size was statiscally calculated, another limitation of the study is the small number of patients.

Conclusion

In conclusion, PENG block may provide equivalent postoperative morphine consumption, compared to femoral block in patients operated on for femoral neck fractures. However, postoperative quadricipital mobility is significantly preserved with PENG block, which could be exploited by an earlier lifting in the context of ERAS. Further studies with a prospective multicentric design and with a greater number of patients should be done to confirm this result.

Acknowledgments

We would like to thank all the anesthesiologists, surgeons, nurses and patients who participated in the realization of this work.

Data Availability

Data cannot be shared publicly because of PHI contents. Data are available from the Institutional Data Access “Protection des Donnees de l’APHP” (contact via protectiondesdonnees.aphp6@aphp.fr) for researchers who meet the criteria for access to confidential data.

Funding Statement

The authors received no specific funding for this work.

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Decision Letter 0

Robert Jeenchen Chen

25 Feb 2021

PONE-D-21-01032

PAF study: Peng block in Emergency Arthroplasty of the Upper Extremity of the Femur : a before/after study

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If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

We look forward to receiving your revised manuscript.

Kind regards,

Robert Jeenchen Chen, MD, MPH

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

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2. Please amend either the title on the online submission form (via Edit Submission) or the title in the manuscript so that they are identical.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: First, I would like to express sincere gratitude to get an opportunity to review the manuscript. The endeavor of the authors is appreciated, as the topic seems to be relevant and promising. The authors have compared PENG block with femoral nerve block for arthroplasty surgery in femoral neck fractures. However, there is some scope for its improvement.

Specific concerns:

1. The title mentions about emergency arthroplasty. Why were such replacement surgery done in emergency basis?

2. It seems the terms ‘before and after’ to be inappropriate. I think it would be better to mention ‘comparison of two procedures’.

3. Kindly mention the principle of the PENG block.

4. Kindly provide Institutional Review Board reference number and date.

5. Was informed written consent taken from the participants of the study?

6. It would be better if study design were clearly mentioned in title, abstract and main text.

Section wise comments

1. Kindly frame title such that it is accurate, informative, descriptive, succinct, simple and specific. The information from title is not convincing.

a. The author may consider modifying the title.

b. Title should contain design of the study.

c. Kindly avoid abbreviations.

d. The words ‘upper extremity’ in needs to be removed. Instead ‘neck of femur fracture would make more sense’.

2. Methods sections is supposed to be core of any study. Here, methods section contains inadequate information. For example, following components for methods section need to be well described.

i. Details of Study design

ii. Setting

iii. Sample size estimation

iv. Sampling technique

v. Participant

vi. Primary and secondary outcome variables with working definition

vii. Intervention/issue of interest (exposure)

viii. Comparison

ix. Ethics and end point

x. Statistical analysis

3. The discussion section needs to be described scientifically. Kindly frame it along the following lines:

a. Main findings of the present study

b. Comparison with other studies

c. Implication and explanation of findings

d. Strengths and limitations

e. Conclusion, recommendation and future directions

Reviewer #2: The research compared the efficacy and side effects of the “Pericapsular Nerve Group (PENG) Block” with those of the femoral block. The study is interesting and the result is encouraging and practical. The limit is the small scale of the sample.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: Yes: Dr Satish Prasad Barnawal

Reviewer #2: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PLoS One. 2021 Jun 4;16(6):e0252716. doi: 10.1371/journal.pone.0252716.r002

Author response to Decision Letter 0


17 Mar 2021

Response to reviewers #1 and #2

� Reviewer #1

First, I would like to express sincere gratitude to get an opportunity to review the manuscript. The endeavor of the authors is appreciated, as the topic seems to be relevant and promising. The authors have compared PENG block with femoral nerve block for arthroplasty surgery in femoral neck fractures. However, there is some scope for its improvement.

First of all, we would like to thank the Dr. Satish Prasad Barnawal for spending time to review our manuscript. It is a great honor to read his comments so that our work would be better after revising it. We hope that our changes would suit his expectations.

Sincerely,

Allard Céline, MD and Verdonk Franck, MD, PhD

Specific concerns:

1. The title mentions about emergency arthroplasty. Why were such replacement surgery done in emergency basis?

Our study concerns only arthrosplasties in the femoral neck fracture setting. So that, all surgeries were done in an emergency basis as delayed surgeries (>24 hours) have been associated with an increase in mortality and incidence of pneumonia, myocardial infarction, and pulmonary embolism at 30 days (1,2).

2. It seems the terms ‘before and after’ to be inappropriate. I think it would be better to mention ‘comparison of two procedures’.

Accordingly to this comment, we corrected our manuscript title which is now “Comparison between femoral block and PENG block in femoral neck fractures : a cohort study”.

3. Kindly mention the principle of the PENG block.

We added the principle of the PENG block in the material and methods section, “intervention” paragraph.

“The PENG block is a diffusion block on the anterior surface of the hip joint capsule. The target nerve branches of this block are the articular branches of the femoral nerve, the obturator nerve and the accessory obturator nerve, leading to no quadricipital motor block. Using a curvilinear low-frequency ultrasound probe (5 MHz) placed in a transverse plane over the Anterior Inferior Iliac Spine (AIIS) and rotated to be aligned with the pubic ramus, a 80 mm RA needle is inserted to inject 20ml of ropivacaine 3.5 mg/ml. The landmarks of this block are externally the AIIS, internally the iliopubic eminence, the psoas tendon anteriorly and the pubic ramus posteriorly.”

4. Kindly provide Institutional Review Board reference number and date.

We added a specific section to clarify this ethical point of utmost importance as “Regulatory and Ethical Aspects” in “Material and methods”, as following:

“In accordance with French law on biomedical research, this observational data-based study obtained the approval of the Institutional Review Board “Comité d’Ethique de la Recherche en Anesthésie-Réanimation (CERAR, president Prof J.E. Bazin, May 6th 2020) under the reference number IRB 00010254 - 2020 – 078.

In order to guarantee the security of personal data, the investigators collected and integrated the information anonymously into a secure database in accordance with the French Commission Nationale de l’Informatique et des Libertés (CNIL) MR-004 methodology, and registered in the Assistance Publique – Hôpitaux de Paris (AP-HP) processing register under the number 20200512144042.”

5. Was informed written consent taken from the participants of the study?

Our study is observational and data-based. In accordance with the French law on biomedical research, all participants of the study as well as all patients from the Assistance Publique -Hôpitaux de Paris signed a consent for possible use of their hospitalization data, as it was done here. In addition, information was delivered through the hospital’s welcome booklet, and in all medical reports at the hospital discharge. To clarify this point to the readers of Plos One, we added this information in the “Regulatory and Ethical Aspects” section as following :

“Patients consented via the websites of the institution (AP-HP and Hôpital Saint-Antoine) to the possible use of their data in research aimed towards improving the quality of care, and were informed about their rights and terms of objection. This information was also included for each patient in the hospital’s welcome booklet, which was given during administrative registration and presented at the end of the hospitalization reports.”

6. It would be better if study design were clearly mentioned in title, abstract and main text.

We fully agree with Dr. Satish Prasad Barnawal’s comment. We changed the manuscript so that the study design is much well explained. This study is a cohort study : comparative and single-center.

7. Methods sections is supposed to be core of any study. Here, methods section contains inadequate information.

Accordingly to the Dr. Satish Prasad Barnawal’s comment, we rewrite the methods to improve the manuscript quality. We added some subheadings so that the comprehension of section is clearer.

8. The discussion section needs to be described scientifically.

We changed the discussion section to be more accurate by adding subheadings.

� Reviewer #2

The research compared the efficacy and side effects of the “Pericapsular Nerve Group (PENG) Block” with those of the femoral block. The study is interesting and the result is encouraging and practical. The limit is the small scale of the sample.

We would like to thank reviewer #2 for all the time spent to review our work. We hope that this revised version would suit his/her expectations. We fully agree with reviewer #2 that one of the limits of this study is the small sample of population. We found these results encouraging and will certainly conduct another prospective study with a more important number of patients to confirm the latter.

Sincerely,

Allard Céline, MD and Verdonk Franck, MD, PhD

Decision Letter 1

Robert Jeenchen Chen

11 Apr 2021

PONE-D-21-01032R1

Comparison between femoral block and PENG block in femoral neck fractures: a cohort study

PLOS ONE

Dear Dr. Franck,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please revise accordingly. 

Please submit your revised manuscript by May 26 2021 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Robert Jeenchen Chen, MD, MPH

Academic Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #3: All comments have been addressed

Reviewer #4: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #3: Yes

Reviewer #4: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #3: Yes

Reviewer #4: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #3: Yes

Reviewer #4: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #3: Yes

Reviewer #4: No

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #3: The article is of scientific interest and in line with the aims of the journal. The manuscript restates the authors guidelines and does not require a revision of the English language by a native speaker. The changes made after the reviews have certainly increased the quality of the article. I recommend its publication after minor revision.

KEYWORDS

In order to improve the visibility of the article, do not use keywords already present in the title.

ABSTRACT

Materials and methods: "42 patients were reviewed: 21 patients before (Femoral group) and 21 patients ..." delete all information relating to the included patients and move it to the results section. In the materials and methods section there should be only the inclusion and exclusion criteria and not information on the patients included.

INTRODUCTION

The introduction should be extended.

MATERIALS AND METHODS

"of 21 patients in each group (total number of 42 patients) was" move to the results section.

Statistical analysis was adequately performed-

RESULTS AND DISCUSSION

The results are written very fluently and are adequately argued in the discussion.

LIMITS

Add the small number of patients.

CONCLUSIONS

Invite future studies that resolve the limitations expressed above.

FIGURES

The figures are of good quality.

TABLES

The tables are well made and adequately cover the text.

REFERENCES

The references are recent and the text is adequate.

Reviewer #4: Comment on the manuscript Number PONE-D-21-01032R1

Comparison between femoral block and PENG block in femoral neck fractures: a

cohort study

The idea of the research is interesting for the readers of the journal. The authors compared the effect of 2 types of nerve block ( Femoral nerve block and Pericapsular Nerve Group Block) on the postoperative pain relief and recovery of patient who underwent hip replacement after fracture neck of femur. They used for this multiple parameters as mentioned in the study. They found no significant difference between both nerve blocks except in one parameter which is the quadriceps muscle strength. This parameter was for the advantage of the Pericapsular Nerve Group Block.

The article submitted for me to review was the second version of the article. I acknowledge the improvements that the Authors did on the first version of the manuscript which has met most of the recommendations of the previous reviewers. In spite of this there is still a room for improvement. I have the following recommendation:

• I recommend the authors lit the article being reviewed by an english language specialist.

• Lines 38 and 88 and other locations: The Term “intermediate hip replacements” is strange and not known in orthopedic surgery. Did the authors mean hemi arthroplasty or bipolar arthroplasty? Please explain and I recommend to use the world wide known terminology.

• Line 104: there is nothing called the upper extremity of the femur. Please Replace with fracture of the proximal femur.

• The abbreviation IQR is repeatedly used in the article without mentioning what it does mean. This was mention under one of the tables. Please write it in full text at the first time to appear in the text.

• Some spelling mistakes:

- Line 71: PEricapsular should be "Pericapsular.

- Line 90: Associated to …. Please replace using : Associated with .

- Line 137: an experimented anesthesiologist please replace with experienced anesthesiologist

I recommend to accept the article for publication after considering the previous recommendations.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #3: No

Reviewer #4: Yes: Dr. Ayman F. AbdelKawi, MD

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PLoS One. 2021 Jun 4;16(6):e0252716. doi: 10.1371/journal.pone.0252716.r004

Author response to Decision Letter 1


19 Apr 2021

Response to reviewers #3 and #4

� Reviewer #3

The article is of scientific interest and in line with the aims of the journal. The manuscript restates the authors guidelines and does not require a revision of the English language by a native speaker. The changes made after the reviews have certainly increased the quality of the article. I recommend its publication after minor revision.

First of all, we would like to thank the reviewer #3 for spending time to review the new version of our manuscript. We hope that our changes would suit his expectations.

Sincerely,

Allard Céline, MD and Verdonk Franck, MD, PhD

Specific concerns:

1. KEYWORDS

In order to improve the visibility of the article, do not use keywords already present in the title.

We deleted the keyword “PENG block” which already appear in the title.

2. ABSTRACT

Materials and methods: "42 patients were reviewed: 21 patients before (Femoral group) and 21 patients ..." delete all information relating to the included patients and move it to the results section. In the materials and methods section there should be only the inclusion and exclusion criteria and not information on the patients included.

We re-wrote this section so that this information appears in the section “results” and not in the “materials and methods” section.

3. INTRODUCTION

The introduction should be extended.

We added some information in the “introduction” paragraph.

Line 54 “By 2050, it is estimated that more than 4.5 million patients worldwide per year will suffer a femoral neck fracture. (1)”

Line 67 “even the “3-in-1” block which can theoretically block all the three nerves by only one injection does not often reach the territory of the obturator nerve (8).”

4. LIMITS

Add the small number of patients.

This limitation of the study is added in line 296 “Even if the sample size was statistically evaluated, another limitation of the study is the small number of patients.”

5. CONCLUSIONS

Invite future studies that resolve the limitations expressed above.

We added this sentence in the conclusion section in line 304 “Further studies with a prospective multicentric design and with a greater number of patients should be done to confirm these results.” 

� Reviewer #4

The idea of the research is interesting for the readers of the journal. The authors compared the effect of 2 types of nerve block (Femoral nerve block and Pericapsular Nerve Group Block) on the postoperative pain relief and recovery of patient who underwent hip replacement after fracture neck of femur. They used for this multiple parameters as mentioned in the study. They found no significant difference between both nerve blocks except in one parameter which is the quadriceps muscle strength. This parameter was for the advantage of the Pericapsular Nerve Group Block.

The article submitted for me to review was the second version of the article. I acknowledge the improvements that the Authors did on the first version of the manuscript which has met most of the recommendations of the previous reviewers. In spite of this there is still a room for improvement. I have the following recommendation:

• I recommend the authors lit the article being reviewed by an english language specialist.

• Lines 38 and 88 and other locations: The Term “intermediate hip replacements” is strange and not known in orthopedic surgery. Did the authors mean hemi arthroplasty or bipolar arthroplasty? Please explain and I recommend to use the world wide known terminology.

• Line 104: there is nothing called the upper extremity of the femur. Please Replace with fracture of the proximal femur.

• The abbreviation IQR is repeatedly used in the article without mentioning what it does mean. This was mention under one of the tables. Please write it in full text at the first time to appear in the text.

• Some spelling mistakes:

- Line 71: PEricapsular should be "Pericapsular.

- Line 90: Associated to …. Please replace using : Associated with .

- Line 137: an experimented anesthesiologist please replace with experienced anesthesiologist

We would like to thank Dr. Ayman F. AbdelKawi, MD for all the time spent to review our work.

We changed our manuscript by respecting all his remarks and suggestions. We sent the manuscript to an English native speaker (Dr. Eileen Tsai) to check the language. We hope that it will now suit his expectations.

Sincerely,

Allard Céline, MD and Verdonk Franck, MD, PhD

Decision Letter 2

Robert Jeenchen Chen

13 May 2021

PONE-D-21-01032R2

Comparison between femoral block and PENG block in femoral neck fractures: a cohort study

PLOS ONE

Dear Dr. Franck,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please revise accordingly.

Please submit your revised manuscript by Jun 27 2021 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Robert Jeenchen Chen, MD, MPH

Academic Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #3: All comments have been addressed

Reviewer #5: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #3: Yes

Reviewer #5: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #3: Yes

Reviewer #5: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #3: Yes

Reviewer #5: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #3: Yes

Reviewer #5: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #3: I thank the authors for the corrections made. The work has been improved and is now acceptable for publication.

Reviewer #5: This study was a before and after protocol, comparing the phase of femoral block to newly applied PENG block. The methods were simple. Simply, the authors showed non-inferiority of PENG regarding perioperative pain control, and the results seemed to be sound. I would address some minor comments.

Minor comments

#1. Regarding the inclusion criteria, I do not understand how the author managed those who the block was not sufficient, and the technique of analgesia was converted to other ways (general anesthesia or spinal?).

#2. I understand that calculating sample size was so difficult. However, for me, a 30% decrease of morphine consumption in 48 hours seemed to be too large. Reference # 15 and # 16 would not generate the idea of 30% decrease. I do not have the impression that the effects of block last for 48 hours. The pain scores in the surgery or morphine consumption in OR or PACU would have some reason.

#3. The authors showed that the MRC scale before discharge from RR was different. Please wrote the timing of MRC measurement in the result (line 221 to 224). How long the muscle weakness last would be a good discussion point. The description of ERAS in discussion seemed to be over-speculation. It can be deleted.

#4. In the conclusions, the authors wrote that PENG provided “equivalent”. However, because of the small sample size, probably the description would be written in more mild way.

#5. For me, the description of acknowledgment was too broad. Probably, a little more specific description would be favorable.

#6. Regarding figure legends, the publishers will request the title of figure and the explanation.

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Reviewer #3: No

Reviewer #5: No

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PLoS One. 2021 Jun 4;16(6):e0252716. doi: 10.1371/journal.pone.0252716.r006

Author response to Decision Letter 2


16 May 2021

Response to reviewers #3 and #5

� Reviewer #3

I thank the authors for the corrections made. The work has been improved and is now acceptable for publication.

Dear Reviewer #3,

Thank you again for reviewing our work. We hope to work with you again soon.

Sincerely yours,

Dr. Céline ALLARD and Dr. Franck VERDONK 

� Reviewer #5

This study was a before and after protocol, comparing the phase of femoral block to newly applied PENG block. The methods were simple. Simply, the authors showed non-inferiority of PENG regarding perioperative pain control, and the results seemed to be sound. I would address some minor comments.

Minor comments

#1. Regarding the inclusion criteria, I do not understand how the author managed those who the block was not sufficient, and the technique of analgesia was converted to other ways (general anesthesia or spinal?).

This study is a before and after protocol comparing two types of analgesic block -femoral block and PENG block- before a total hip arthroplasty (THA) or hemi arthroplasty (HA) both performed in emergency for hip fracture. Both analgesic blocks were performed in the pre-anesthesia room, right before entering the operating room.

All surgeries were done under general anesthesia as written in the methods section. We made the decision, prior to data collection and analysis, to exclude patients operated under spinal anesthesia considering that spinal anesthesia will modify pain and muscle strength evaluation after the surgery, in addition to the potential systemic effect of local anesthetics and morphine in this setting.

#2. I understand that calculating sample size was so difficult. However, for me, a 30% decrease of morphine consumption in 48 hours seemed to be too large. Reference # 15 and # 16 would not generate the idea of 30% decrease. I do not have the impression that the effects of block last for 48 hours. The pain scores in the surgery or morphine consumption in OR or PACU would have some reason.

We totally agree with this comment. However, calculating sample size was very difficult because there is actually no study in the literature comparing morphine consumption after femoral block and another type of analgesic block. References #15 and #16 evoke the possibility of a 30% decrease in morphine consumption.

We also agree with the reviewer that the effect of analgesic block may not last for more than 24 hours. The primary end point of this study was the cumulative morphine consumption at 48 hours after the surgery as one of the common endpoints in studies focusing on peri-operative medicine 1,2. That being said, the pain scores after surgery recorded in PACU didn’t show any significant difference between the two groups of patients.

#3. The authors showed that the MRC scale before discharge from RR was different. Please wrote the timing of MRC measurement in the result (line 221 to 224). How long the muscle weakness last would be a good discussion point. The description of ERAS in discussion seemed to be over-speculation. It can be deleted.

We thank the reviewer for his comment. We added this sentence in the methods section to explain when the MRC score was measured :

“immediate postoperative mobility of the operated limb quadriceps as defined by the Medical Research Council (MRC) scale (17) before discharge from RR (2 hours after the end of surgery).”

We deleted the paragraph concerning ERAS in the discussion and added this sentence concerning the duration of the muscle weakness after a femoral block :

“In a previous study, Ghodki et al showed that only 13% of the 30 patients receiving femoral nerve block present a normal quadricipital motricity 12 hours after surgery and, more interestingly, that 17% of them still have muscle weakness 24 hours after surgery.”

#4. In the conclusions, the authors wrote that PENG provided “equivalent”. However, because of the small sample size, probably the description would be written in more mild way.

We modified the conclusion to address this comment :

“In conclusion, in this study, PENG block may provide equivalent postoperative morphine consumption, compared to femoral block in patients operated on for femoral neck fractures.”

#5. For me, the description of acknowledgment was too broad. Probably, a little more specific description would be favorable.

We modified a bit the acknowledgment section :

“We would like to thank all the anesthesiologists, surgeons, nurses and patients who participated in the realization of this work.”

#6. Regarding figure legends, the publishers will request the title of figure and the explanation.

The titles of the figures already are in the manuscript. The figures were uploaded separately in the Plos one online submission form, as it was asked.

We added the explanation of the figure in the manuscript :

“Explanation of the figure : box-plot diagram : the rectangle extends from the first quartile to the third quartile and is intersected by the median. The segments at the ends of the rectangle provide information on the extreme values.”

Decision Letter 3

Robert Jeenchen Chen

21 May 2021

Comparison between femoral block and PENG block in femoral neck fractures: a cohort study

PONE-D-21-01032R3

Dear Dr. Franck,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Robert Jeenchen Chen, MD, MPH

Academic Editor

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

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Reviewer #3: All comments have been addressed

Reviewer #5: All comments have been addressed

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Reviewer #3: Yes

Reviewer #5: (No Response)

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Reviewer #3: Yes

Reviewer #5: (No Response)

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Reviewer #3: Yes

Reviewer #5: (No Response)

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Reviewer #3: Yes

Reviewer #5: (No Response)

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Reviewer #5: (No Response)

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Reviewer #3: No

Reviewer #5: No

Acceptance letter

Robert Jeenchen Chen

25 May 2021

PONE-D-21-01032R3

Comparison between femoral block and PENG block in femoral neck fractures: a cohort study

Dear Dr. Verdonk:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

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on behalf of

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    Data Availability Statement

    Data cannot be shared publicly because of PHI contents. Data are available from the Institutional Data Access “Protection des Donnees de l’APHP” (contact via protectiondesdonnees.aphp6@aphp.fr) for researchers who meet the criteria for access to confidential data.


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