A prospective randomized controlled trial comparing subpectineal and interfascial obturator nerve block techniques in preventing adductor muscle spasm during transurethral resection of bladder tumors

Abstract

Background

Obturator nerve block (ONB) is commonly used to prevent adductor muscle spasm during transurethral resection of bladder tumors (TURBT) involving lateral wall lesions. This study aimed to compare the clinical effectiveness and safety of ultrasound-guided subpectineal (proximal) and interfascial (distal) ONB techniques, utilizing an anatomically tailored dosing regimen adapted to the targeted fascial compartments.

Methods

This prospective randomized controlled trial included 60 patients scheduled for elective TURBT under spinal anesthesia. Patients were randomly allocated into two equal groups: subpectineal ONB (Group I, n = 30), which received a single 10 mL bolus of 0.375% bupivacaine into the single subpectineal plane, and interfascial ONB (Group II, n = 30), which received a total of 20 mL of 0.375% bupivacaine split into two separate 10 mL injections for the two distinct interfascial planes. Intraoperative adductor muscle spasm was evaluated by a blinded surgeon using a 4-grade scale (Grades I–IV). The primary outcome was the block success rate, defined as the absence of severe spasm (Grade IV) requiring rescue general anesthesia.

Results

Baseline demographic characteristics and the number of needle insertions were similar between the groups. No vascular puncture, hematoma, or bladder perforation occurred. The descriptive block success rate was high in both groups, reaching 86.7% (95% confidence interval: 74.6% to 98.8%) in Group I and 93.3% (95% Confidence Interval: 84.4% to 100%) in Group II, with no statistically significant difference observed (p = 0.671).

Conclusions

Both ultrasound-guided ONB techniques demonstrate high descriptive clinical success rates when utilizing an anatomically tailored dosing regimen. Although the non-significant p-value must be interpreted with caution due to sample size limitations, both approaches provide viable and effective options for preventing severe adductor muscle spasm during lateral wall TURBT.

Trial Registration

ClinicalTrials.gov Identifier: NCT07481123 (retrospectively registered on 02 March 2026).

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1186/s12871-026-04091-5.

Introduction

Bladder cancer is one of the most frequently diagnosed malignancies worldwide and represents a major public health burden, particularly among elderly male patients. According to global cancer statistics, bladder cancer ranks among the most common urological malignancies and is associated with substantial morbidity and healthcare costs [1]. Transurethral resection of bladder tumor (TURBT) remains the cornerstone for diagnosis, pathological staging, and initial management of bladder cancer, and the quality of this procedure has a direct impact on recurrence rate and long-term oncological outcomes [2].

Despite its central role in bladder cancer management, TURBT is associated with several intraoperative challenges that may compromise surgical safety and procedural completeness, especially during resections involving the lateral bladder wall. One of the most clinically significant complications encountered during TURBT is the obturator reflex, which results from inadvertent stimulation of the obturator nerve during electrocautery [3, 4]. This reflex manifests as sudden and forceful adductor muscle contraction and may lead to incomplete tumor resection, excessive bleeding, bladder perforation, and potential extravesical dissemination of tumor cells [3].

The obturator nerve originates from the L2–L4 nerve roots and courses in close anatomical proximity to the inferolateral bladder wall, rendering it particularly susceptible to electrical stimulation during lateral wall resections [4, 5]. Previous studies have reported a high incidence of obturator reflex during TURBT, especially when monopolar electrocautery is used, underscoring the need for effective preventive strategies to ensure both surgical safety and oncological adequacy [3, 5].

Various strategies have been proposed to reduce the risk of obturator reflex, including lowering electrocautery settings, reducing bladder distension, using bipolar energy systems, deepening general anesthesia, or administering neuromuscular blocking agents [6, 7]. However, these approaches may provide inconsistent protection and may be associated with increased anesthetic risks or postoperative complications [8]. In contrast, obturator nerve block (ONB) has been widely accepted as a reliable and effective technique for preventing adductor muscle spasm during TURBT and can be safely applied under both regional and general anesthesia [8].

The introduction of ultrasound guidance into regional anesthesia practice has markedly improved the accuracy, safety, and success rates of ONB by enabling real-time visualization of neural structures, surrounding muscles, and adjacent vascular anatomy [9, 10]. Ultrasound guidance allows precise needle placement and controlled local anesthetic spread, thereby reducing complication rates and improving block reliability compared with landmark-based or nerve stimulation techniques. As a result, ultrasound-guided ONB has become an integral component of anesthetic management during TURBT, particularly for lesions involving the lateral bladder wall.

Ultrasound-guided ONB techniques are generally classified as distal (interfascial) or proximal (subpectineal) approaches [11]. In the interfascial technique, the anterior and posterior branches of the obturator nerve are identified and blocked separately within the interfascial planes between the adductor muscle groups. This approach typically requires multiple needle insertions and relatively higher volumes of local anesthetic to achieve complete blockade [12]. In contrast, the subpectineal approach targets the obturator nerve at a more proximal level within the fascial plane beneath the pectineus muscle, before its bifurcation, enabling blockade of both branches with a single injection targeting the proximal trunk [13]. Consequently, while the subpectineal approach requires only a single compartmental injection, the distal interfascial approach mandates independent targeting of two separate fascial layers. Therefore, to evaluate these techniques in their clinically optimal settings, the local anesthetic volume must be adapted to the number of anatomical planes targeted.

Although both ultrasound-guided interfascial and subpectineal ONB techniques are currently used in clinical practice, direct comparative evidence regarding their relative effectiveness in preventing adductor muscle spasm during TURBT remains limited [14]. Therefore, the present prospective study aimed to directly compare ultrasound-guided subpectineal and interfascial ONB techniques with respect to adductor muscle spasm prevention, block success rate, safety profile, and perioperative anesthetic outcomes in patients undergoing TURBT.

Methods

Study design and ethical approval

This prospective, randomized clinical study was conducted between August 2022 and December 2022 at the Department of Anesthesiology and Reanimation, Ankara Etlik City Hospital. The study protocol was officially approved by the Institutional Ethics Committee of Health Sciences University Dışkapı Yıldırım Beyazıt Training and Research Hospital (Approval date: 04 July 2022; Decision No: 141/09) and was conducted in accordance with the principles of the Declaration of Helsinki. Written informed consent was obtained from all participants prior to enrollment [15].

This study was originally conducted as part of a residency thesis project between August and December 2022. ClinicalTrials.gov registration (NCT07481123) was completed retrospectively in March 2026 during manuscript preparation.

Patient selection and randomization

A total of 60 patients scheduled to undergo TURBT for diagnosed lateral wall bladder tumor were included in the study. Eligible patients had an American Society of Anesthesiologists (ASA) physical status classification of II or III. Exclusion criteria included refusal to participate, communication disorders, known allergy to local anesthetics, inguinal lymphadenopathy, infection or scarring at the needle insertion site, coagulopathy, or pre-existing neuromuscular disease.

Patients were randomly allocated into two equal groups using a computer-generated randomization sequence. Group assignments were placed in sealed, opaque envelopes and opened immediately before ONB application [16]. Patients were assigned to one of two groups: Group I (n = 30), who received an ultrasound-guided subpectineal ONB, and Group II (n = 30), who received an ultrasound-guided interfascial ONB.

Anesthetic and dosing rationale & study procedures

To evaluate these regional techniques in their anatomically optimal settings, the local anesthetic volume was deliberately tailored to the number of fascial planes targeted. The subpectineal approach targets the undivided main trunk of the obturator nerve within a single, tightly enclosed fascial plane, requiring only a single 10 mL bolus. Conversely, the interfascial technique targets the anterior and posterior branches after bifurcation, which run through two separate, non-communicating interfascial compartments, thus requiring a split volume of 20 mL (10 mL per plane) to ensure adequate spread.

Standard monitoring was applied to all patients, including non-invasive blood pressure, electrocardiography, and peripheral oxygen saturation. All 60 enrolled patients underwent the assigned ultrasound-guided ONB as a preoperative intervention. Following the block, a standardized spinal anesthesia protocol was performed in the sitting position using 2.0 to 2.5 mL of 0.5% hyperbaric bupivacaine. The sensory block level was carefully monitored and strictly targeted to achieve a maximum dermatomal height of T10 (umbilical level). This specific level ensures excellent intraoperative mucosal analgesia for the bladder resection while intentionally avoiding any high-lumbar motor blockade that could independently relax the adductor muscles and confound the assessment of the ONB. Neuromuscular blocking agents were completely avoided during the initial setup. Intraoperative grading of adductor muscle spasm was performed by a urologist blinded to the group assignment. General anesthesia with systemic muscle relaxants was utilized strictly as a rescue intervention only if a patient developed severe adductor muscle spasm (Grade IV) that compromised surgical safety.

Ultrasound-guided ONB techniques

All ONBs were performed preoperatively under ultrasound guidance by an experienced anesthesiologist with more than five years of experience in ultrasound-guided regional anesthesia, using a high-frequency linear ultrasound transducer and strict aseptic technique.

Interfascial technique (Group II)

The interfascial ONB was performed according to previously described ultrasound-guided techniques. The ultrasound probe was positioned parallel to the inguinal crease to visualize the adductor muscle compartments. The anterior branch of the obturator nerve was targeted between the adductor longus and adductor brevis muscles, and the posterior branch was targeted between the adductor brevis and adductor magnus muscles. A 22-gauge block needle was advanced strictly using an in-plane technique from lateral to medial under continuous, real-time ultrasound visualization of the needle tip and shaft. A total of 20 mL of 0.375% bupivacaine was administered, split into two separate 10 mL injections into each independent interfascial plane following negative aspiration (Fig. 1).

Fig. 1.

Interfascial technique application

Subpectineal technique (Group I)

The subpectineal ONB was performed using the proximal technique described by Taha. The ultrasound probe was placed medial to the inguinal crease and oriented cranially to visualize the pectineus muscle, obturator externus muscle, and the superior pubic ramus. The block needle was advanced strictly using the identical in-plane technique under continuous, real-time ultrasound visualization, directed beneath the posterior fascia of the pectineus muscle into the subpectineal fascial plane. After negative aspiration, a single 10 mL bolus of 0.375% bupivacaine was injected to target the main trunk of the obturator nerve before its bifurcation (Fig. 2).

Fig. 2.

Subpectineal technique application

Outcome measures

The primary outcome of the study was block success rate, defined as the absence of severe adductor muscle spasm (Grade IV) during surgery without the need for additional intervention.

Adductor muscle spasm was assessed intraoperatively by a urologist blinded to group allocation and graded as follows:

• Grade I, no movement or palpable muscle twitching;

• Grade II, palpable muscle twitching without movement;

• Grade III, slight movement of the thigh not interfering with the surgical procedure;

• Grade IV, vigorous movement interfering with the surgical procedure [17].

Secondary outcomes included the incidence and distribution of adductor muscle spasm grades, number of needle insertion attempts and block-related complications.

Statistical analysis

Statistical analysis was performed using SPSS software (version 22.0; IBM Corp., Armonk, NY, USA). Normality of data distribution was assessed using the Kolmogorov–Smirnov and Shapiro–Wilk tests. Continuous variables were expressed as mean ± standard deviation and compared using the independent samples t-test or Mann–Whitney U test, as appropriate. Categorical variables were expressed as number (percentage) and analyzed using the chi-square test or Fisher’s exact test. A p-value < 0.05 was considered statistically significant. This study was conducted in accordance with the CONSORT (Consolidated Standards of Reporting Trials) guidelines for randomized controlled trials.

Sample size calculation was evaluated based on intraoperative adductor muscle spasm data derived from reference literature. In the proximal subpectineal technique described by Taha [13], a high success rate was indicated, whereas Tiwari et al. [17] observed a clinical success rate of 76% utilizing the distal interfascial technique under ultrasound guidance alone. To account for these clinical benchmarks and accommodate potential dropouts, a total of 60 patients (30 patients per group) were enrolled. However, given that the primary outcome was dichotomous and prior data on categorical outcomes were limited, a post-hoc power analysis based on the actual primary outcome data observed in this study (success rates of 86.7% in Group I versus 93.3% in Group II) was conducted. This analysis revealed that the actual statistical power to detect a significant difference between the two techniques was only 11.4% (with an alpha level of 0.05). Consequently, due to this limited sample size, the trial was heavily underpowered to establish either definitive superiority or therapeutic equivalence, carrying an inherently high risk of Type II error.

Results

Baseline demographic and clinical characteristics

A total of 60 patients were included in the study. Of these, 30 patients were allocated to the ultrasound-guided subpectineal ONB (Group I) and 30 patients to the ultrasound-guided interfascial ONB (Group II). All enrolled patients completed the study, and no exclusions occurred after randomization.

Demographic and clinical characteristics of the study population are summarized in Table 1. The two groups were comparable with respect to age, ASA physical status, and block laterality.

Table 1.

Comparison of baseline demographic and clinical characteristics between groups

Variable	Group I (Subpectineal) (n = 30)	Group II (Interfascial) (n = 30)	p value
Age (years), mean ± SD	69.2 ± 5.6	66.2 ± 6.9	0.071
ASA physical status, n (%)			0.542
- ASA II	22 (73.3)	24 (80.0)
- ASA III	8 (26.7)	6 (20.0)
Block side, n (%)			0.791
- Right	12 (40.0)	11 (36.7)
- Left	18 (60.0)	19 (63.3)

SD standard deviation, ASA American Society of Anesthesiologists

The mean age was 69.2 ± 5.6 years in Group I and 66.2 ± 6.9 years in Group II (p = 0.071). In Group I, 22 patients (73.3%) were classified as ASA II and 8 patients (26.7%) as ASA III, whereas in Group II, 24 patients (80.0%) were ASA II and 6 patients (20.0%) were ASA III (p = 0.542). The ONB was performed on the right side in 12 patients (40.0%) and on the left side in 18 patients (60.0%) in Group I, and on the right side in 11 patients (36.7%) and on the left side in 19 patients (63.3%) in Group II (p = 0.791).

Needle insertion attempts and block-related complications

The comparison of needle insertion attempts and block-related complications between the two groups is presented in Table 2. The mean number of needle insertion attempts was 1.23 ± 0.50 in Group I and 1.27 ± 0.58 in Group II (p = 0.814).

Table 2.

Comparison of needle insertion attempts and block-related complications

Variable	Group I (n = 30)	Group II (n = 30)	p value
Number of needle insertions, mean ± SD*	1.23 ± 0.50	1.27 ± 0.58	0.814
Success by attempt number, n (%)
1 attempt	24 (80.0)	24 (80.0)
2 attempts	5 (16.7)	4 (13.3)
3 attempts	1 (3.3)	2 (6.7)
Vascular puncture, n	0	0
Other complications**, n	0	0

* SD, standard deviation

**Hematoma or bladder perforation

A single needle insertion was sufficient in 24 patients (80.0%) in each group. Two insertion attempts were required in 5 patients (16.7%) in Group I and in 4 patients (13.3%) in Group II, while three attempts were required in 1 patient (3.3%) in Group I and 2 patients (6.7%) in Group II.

No vascular puncture occurred in either group during block application. In addition, no other block-related complications, including hematoma formation or bladder perforation, were observed in any patient during the perioperative period.

Block success rates

The primary outcome of clinical block success, defined as the complete absence of severe surgery-limiting adductor muscle spasm (Grade IV), was high in both cohorts. Group I (subpectineal approach) demonstrated a descriptive success rate of 86.7% (95% Confidence Interval: 74.6% to 98.8%; 26 out of 30 patients), while Group II (interfascial approach) demonstrated a descriptive success rate of 93.3% (95% Confidence Interval: 84.4% to 100%; 28 out of 30 patients). The absolute risk difference between the two techniques was 6.6% (95% Confidence Interval: -8.7% to 21.9%), which was not statistically significant (p = 0.671).

To evaluate this non-significant result further, a post-hoc power analysis was performed based on these actual primary success rates with our sample size of 30 patients per group and a significance level (alpha) of 0.05. This analysis revealed that the actual statistical power to detect a significant difference between these two high-performing techniques was only 11.4%. Therefore, the non-significant p-value in this trial indicates that the study is underpowered to establish either definitive superiority or clinical equivalence, carrying an inherent risk of a Type II error (false negative). The detailed distribution of all intraoperative adductor muscle spasm grades is summarized in Table 3.

Table 3.

Comparison of block success and failure rates based on adductor muscle spasm grades between groups

Outcome	Group I (n = 30), n (%)	Group II (n = 30), n (%)	p value
Successful block, n (%)	26 (86.7%) [95% CI: 74.6% to 98.8%]	28 (93.3%) [95% CI: 84.4% to 100%]	0.671*
Grade I	24 (80.0%)	26 (86.7%)	0.488
Grade II	2 (6.7%)	1 (3.3%)	0.500
Grade III	0 (0.0%)	1 (3.3%)	0.500
Block failure, n (%)	4 (13.3%)	2 (6.7%)	0.671*
Grade IV	4 (13.3%)	2 (6.7%)	0.671

* Absolute risk difference in block success between the two groups was 6.6% (95% CI: -8.7% to 21.9%).

All 60 patients initially underwent the assigned ultrasound-guided ONB followed by spinal anesthesia as the planned primary anesthetic technique. Intraoperatively, patients who experienced block failure defined as severe Grade IV adductor muscle spasm interfering with the surgery were immediately converted to general anesthesia with the administration of neuromuscular blocking agents to ensure surgical safety. Accordingly, 4 patients (13.3%) in Group I and 2 patients (6.7%) in Group II required conversion to general anesthesia due to intraoperative block failure (p = 0.671).

In Group I, adductor muscle spasm was graded as Grade I in 24 patients (80.0%), Grade II in 2 patients (6.7%), and Grade IV in 4 patients (13.3%), with no Grade III spasm observed. In Group II, Grade I spasm was observed in 26 patients (86.7%), Grade II in 1 patient (3.3%), Grade III in 1 patient (3.3%), and Grade IV in 2 patients (6.7%). Overall, adductor muscle spasm was graded as Grade I in 83.3%, Grade II in 5.0%, Grade III in 1.7%, and Grade IV in 10.0% of all patients included in the study.

The distribution of adductor muscle spasm grades was similar between the two groups across all grades (p > 0.05 for all comparisons).

Discussion

Despite the widespread use of ultrasound-guided ONB techniques during TURBT, direct comparative evidence between subpectineal and interfascial approaches remains limited. Most of the available studies have evaluated these techniques separately or have reported overall block success rates using heterogeneous outcome definitions. In particular, studies directly comparing the two approaches using clinically relevant, surgery-limiting adductor muscle spasm as a primary endpoint are scarce. The present study was therefore designed to address this gap by directly comparing ultrasound-guided subpectineal and interfascial ONB techniques using a standardized spasm grading system that includes severe (Grade IV) adductor muscle spasm.

From a clinical perspective, the interfascial ONB is among the most widely used ultrasound-guided techniques for preventing obturator reflex during TURBT and is well established in routine clinical practice. By facilitating targeted ultrasound-guided blockade of both obturator nerve branches, this approach has shown consistent and reproducible clinical effectiveness across different surgical settings. Sinha et al. evaluated an ultrasound-guided interfascial ONB performed without nerve stimulation and reported a high block success rate of 93%, defined by a significant reduction in thigh adduction strength, supporting the effectiveness of this technique when accurately applied [12]. Nevertheless, variability in reported success rates has been described, depending on the methodology and criteria used to define block success. In a comparative study conducted during TURBT, complete ONB was achieved in 76% of patients in the ultrasound-guided interfascial injection group, whereas an 88% success rate was reported in the nerve stimulation–assisted ONB [17]. Importantly, block success in that study was defined using strict early motor response criteria assessed by nerve stimulation. Despite this difference in overall block completeness, only a limited number of clinically relevant obturator reflex events were observed intraoperatively in both groups. Taken together, these findings suggest that, when clinically meaningful intraoperative endpoints are considered, the interfascial approach provides effective and clinically acceptable obturator reflex suppression during TURBT.

From a neurophysiological and anatomical perspective, the obturator nerve consists of relatively small-diameter fibers with a thin epineurium, making it highly susceptible to low volumes of local anesthetics once precise fascial deposition is achieved. In our study, we deliberately opted for a ‘per-plane standardized volume’ (10 mL per targeted anatomical compartment) rather than a total fixed volume for both cohorts. Because the subpectineal approach targets the undivided main nerve trunk within a single, tightly enclosed fascial compartment beneath the pectineus muscle, a single 10 mL bolus is structurally and neurophysiologicallysufficient to facilitate complete longitudinal spread around the nerve. Conversely, in the distal interfascial technique, the nerve has already divided into anterior and posterior branches that run within two completely isolated, non-communicating fascial planes. Administering less than 10 mL per plane in the distal group would run the clinical risk of under-dosing or failing to spread properly within one of these independent compartments. Therefore, utilizing 10 mL for Group I and 20 mL (10 mL x 2) for Group II reflects the most authentic, anatomically adapted, and clinically correct application of each respective regional technique.

The subpectineal ONB technique was first described by Taha as a proximal interfascial approach that targets the obturator nerve within the fascial plane beneath the pectineus muscle, before its bifurcation into the anterior and posterior branches [13]. Structurally, this allows the administration of local anesthetic as a single bolus at a single site, whereas the distal interfascial technique targets the two branches separately across two distinct planes [12]. Subsequent anatomical and clinical studies have also demonstrated that local anesthetic injected into the fascial plane between the pectineus and obturator externus muscles may spread proximally through the obturator canal, surrounding both branches of the obturator nerve. In a prospective observational study using an in-plane ultrasound-guided proximal approach, all blocks were reported to be successful, supporting the effectiveness of accurate interfascial targeting [18] .

Regarding the operational convenience of the two technologies, our results indicate that the procedural difficulty measured objectively by the number of needle puncture attempts was highly similar between the groups, with 80% of patients in both cohorts requiring only a single skin puncture. If one wishes to consider the theoretical ergonomics of these techniques, it can be hypothesized that the subpectineal approach may offer superior anatomical convenience when encountering technical difficulties. Adjusting the needle tip within a single, continuous fascial plane beneath the pectineus muscle could potentially be less technically demanding than repositioning a needle across two separate, deeper interfascial planes as required by the interfascial technique. Nevertheless, this remains a theoretical assumption that was not directly measured or proven by our data, and it should serve as a prospective direction for future trials focusing on learning curves and procedural duration.

Han et al. compared ultrasound-guided interfascial and subpectineal ONB techniques in patients undergoing TURBT and reported high block success rates for both approaches. In their randomized study, 25 patients were allocated to each group, with block success rates of 96% for the proximal approach and 92% for the distal approach, finding no statistically significant difference between the techniques [11] . Similarly, in the present study, the clinical success rates defined as the absolute absence of severe, surgery-limiting adductor muscle spasm (Grade IV) were 86.7% in the subpectineal group and 93.3% in the interfascial group. While these percentages appear visually close, it must be emphasized that with the current sample size of this study, no statistically significant differences could be observed between the two groups. Given the low post-hoc power calculated from our actual clinical data, this study is inherently limited in its ability to detect true, smaller, yet clinically meaningful differences between the proximal and distal approaches. Therefore, our findings should be interpreted with caution, as the lack of statistical significance does not definitively prove therapeutic equivalence.

Several limitations of the present study should be acknowledged. First, the most prominent methodological limitation is the unavoidable discrepancy in the total volume and subsequent total mass of local anesthetic administered between the groups (10 mL in Group I versus 20 mL in Group II). While this dosing regimen was strictly designed to respect the distinct regional anatomy of a single-plane proximal blockade versus a dual-plane distal blockade, it introduces an inherent confounding variable, making it impossible to fully differentiate whether the success is driven by the anatomical access route itself or by the total drug volume. Second, the relatively modest sample size limited our statistical power to 11.4%, as detailed in the results, which restricts our ability to confirm therapeutic equivalence or superiority definitively. Third, the single-center design and the retrospective registration of the trial on ClinicalTrials.gov due to its origin as a residency project should be taken into account when interpreting the findings. Lastly, long-term functional and oncological outcomes were not assessed.

Despite the statistical limitations, these findings carry important implications for routine clinical practice. Both ultrasound-guided techniques provided excellent descriptive success rates exceeding 85% when tailored to their targeted anatomical planes. From a practical perspective, the subpectineal approach provides an attractive, volume-sparing alternative (utilizing only 10 mL), which can be highly advantageous in elderly patients or individuals with significant cardiovascular co-morbidities where local anesthetic volume restrictions are desired. On the other hand, the distal interfascial approach remains a robust and reliable option when a larger volume (20 mL) can be safely tolerated to ensure independent dual-compartment block spread. Anesthesiologists can confidently utilize either technique based on individual patient profiles, anatomical clarity, and specific clinical constraints.

Conclusions

In conclusion, while both ultrasound-guided subpectineal and interfascial ONB techniques demonstrated high descriptive clinical success rates with comparable procedural convenience, the present study was subject to major sample size and statistical power limitations. These constraints preclude any definitive conclusions regarding the comparative superiority or therapeutic equivalence of the two approaches. Consequently, the findings must be interpreted with caution, and larger, adequately powered, multi-center randomized controlled trials are strictly mandatory to validate these results and to identify any subtle technique-related differences in ONB efficacy.

Authors' contributions

Conceptualization, Y.S. and O.T.A.; methodology, O.T.A.; software, Y.S.; validation, H.C.K.; formal analysis, S.G.K.; investigation, Y.S.; resources, Y.S.; data curation, S.G.K.; writing - original draft preparation, O.T.A.; writing - review and editing, O.T.A.; visualization, H.C.K. and S.G.K.; supervision, H.C.K.; project administration, O.T.A. All authors have read and approved the final manuscript.

Funding

This research received no external funding.

Data availability

The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

The study was conducted in accordance with the Declaration of Helsinki. The study protocol was approved by the Institutional Ethics Committee of Health Sciences University DışkapıYıldırımBeyazıt Training and Research Hospital (Approval No: 141/09; 04 July 2022), and the clinical trial was operationally executed at Ankara Etlik City Hospital. Written informed consent was obtained from all participants.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.