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INTRODUCTION
Clavicular fractures account for 35%–45% of all shoulder girdle injuries in adults, with approximately 80% occurring in the middle third [1]. Compared to the traditional conservative approach, surgical fixation demonstrates improved healing outcomes and reduced complications associated with malunion [2,3]. Clavicular fractures are still predominantly operated on under general anesthesia, largely due to the limitations associated with regional anesthesia, which stem from the complex and highly variable nerve supply of the clavicular region [4].
The superficial cervical plexus block is commonly used for clavicular anesthesia in conjunction with interscalene brachial plexus block (ISB), demonstrating a variable success rate [5,6]. However, the risk of phrenic nerve involvement has reduced the popularity of this approach, particularly in patients with borderline pulmonary functions [7,8].
Recent research in regional anesthesia has focused on site-specific nerve blocks to minimize the volume of local anesthetics and to prevent unnecessary nerve blocks [9,10]. The superior trunk of the brachial plexus (ST) and the clavipectoral fascial plane (CFP) blocks can achieve this objective by focusing on the clavicular region while minimizing adverse effects [11,12].
The ST of the brachial plexus originates from the fusion of the fifth (C5) and sixth (C6) cervical nerve roots [11]. The ST block is a refinement of the classic ISB, demonstrating enhanced analgesic efficacy and significantly reduced incidence of hemi-diaphragmatic paralysis in shoulder surgeries compared to the ISB [8,13]. The clavipectoral fascia, located deep to the clavicular origin of the pectoralis major muscle, plays a crucial role in the sensory innervation of the clavicle [12,14]. This interfascial plane block offers analgesia and minimizes the risk of direct nerve injury [15].
The supraclavicular nerve (SCN) gives sensation to the area over the clavicle, upper chest, and proximal shoulder [16]. It is believed to supply the skin before piercing the clavipectoral fascia. Therefore, it could potentially be spared if the CFP block was used only for clavicular surgeries [17]. Additionally, the SCN was occasionally implicated when the brachial plexus block failed to achieve surgical anesthesia in clavicular surgeries. Therefore, the anesthetic plan should include a SCN block to improve the success rate [10].
Selective SCN block can be achieved using a reduced anesthetic volume of 1.5–3 mL, thereby minimizing the risk of affecting the phrenic nerve, compared to the traditional superficial cervical plexus block, which requires a larger volume of 5–10 mL [9].
This study aimed primarily to compare the ST versus the CFP blocks in terms of the first rescue analgesic request times when both were augmented with a selective SCN block for clavicular surgeries. The hypothesis posited that combining an SCN block with either an ST or a CFP block can provide effective perioperative pain relief for clavicular surgeries.
MATERIALS AND METHODS
1. Study design
A prospective randomized double-blinded comparative study was conducted from January to August 2024. The study adhered to the Helsinki Declaration and CONSORT (Consolidated Standards of Reporting Trials) guidelines [18]. The study protocol received approval from the university review board (ZU-IRB# 11287-3/12-2023) and registered at clinicaltrial.gov (NCT06220591, registration date: 24-1-2024). Patient enrollment commenced on January 27, 2024.
The study included 50 patients aged 18 years and older, classified as American Society of Anesthesiologists physical status I and II, with a body mass index of 18.5–24.9 kg/m2. Patients were scheduled for elective unilateral middle-third clavicular surgeries. All patients provided written consent following a comprehensive explanation of the study's objectives and procedures as well as potential complications.
Exclusion criteria included uncooperative patients with known hypersensitivity to study drugs, opioid-dependent patients, patients with respiratory insufficiency, coagulation disorders, and those with pre-existing neurological deficits.
2. Randomization and blinding
Patients were randomly assigned to one of two groups in a 1:1 ratio through simple randomization utilizing a computer-generated randomization table, with 25 participants per group. One group consisted of patients assigned even numbers, whereas the other group comprised those with odd numbers. A blinded researcher, not involved in the interventions, implemented the randomization process. Patients and physicians participating in intraoperative and postoperative care were blinded to group allocation.
3. Preoperative preparation
All patients were hospitalized and admitted one day prior to the surgery. A comprehensive history, physical examination, and standard investigations were conducted. This involved ultrasonographic evaluation of the SCN and the ST of the brachial plexus to assess the potential for a targeted nerve block. During the preoperative visit, the authors explained the numerical pain rating scale to the patient (NRS, 0 = no pain and 10 = worst pain). All patients were required to fast for eight hours before the surgery.
4. Intraoperative care
An intravenous (IV) line was inserted in the preparation room, and fluid administration commenced. Midazolam was administered intravenously at a dosage of 0.05 mg/kg. Standard monitoring equipment was implemented upon transfer to the operating theatre, including five-lead electrocardiography, a pulse oximeter, and non-invasive blood pressure measurement. In the ST group (n = 25), patients underwent a selective SCN block followed by ST (C5,6) blockage of the brachial plexus. In the CFP group (n = 25), patients underwent a selective SCN block followed by a CFP blockage on the medial and lateral ends of the operated clavicle. All procedures were conducted in a sterile environment in the operating room. Intraoperative sedation was maintained using dexmedetomidine 0.2–0.7 mcg/kg/minute as needed.
The blocks were performed using an ultrasound machine (GE Ultrasound Korea, Ltd.) with a high-frequency linear transducer (8–12 MHz). A Stimuplex needle, 50 mm, 22-gauge short bevel, was utilized (B. Braun). The local anesthetic mixture consisted of lidocaine 2% (7.5 mL) and bupivacaine 0.5% (7.5 mL) combined with 100 mg of MgSO4 10% (1 mL) and 4 mg of dexamethasone 0.4% (1 mL) [19,20].
1) Selective supraclavicular nerve block
Patients were positioned supine semi-recumbent, with the head and back supported. The anesthetist stood adjacent to the patient's head, with the ultrasound machine on the opposite side. After crossing the deep cervical fascia, the operator scanned the SCN on the outer border of the sternomastoid muscle, which was 2–3 cm from the clavicle. The skin was prepared with 1 mL of lidocaine 1%, and a sterile 22-gauge blunt 50 mm needle was advanced close to the nerve using the in-plane technique [16]. The local anesthetic mixture of 2 mL was injected in 0.5 mL aliquots after ensuring no blood was aspirated to encircle the SCN (Fig. 1).
2) Superior trunk of the brachial plexus block
The US probe was positioned in the same position after the SCN block was performed, and it was subsequently moved medially to scan the scalene muscles and the C5, C6 nerve roots. Then, the C5,6 nerve roots were followed distally until their union to form the ST down to the supraclavicular area. The needle was directed from lateral to medial, using an in-plane technique. The injection was administered before the suprascapular, long thoracic, and subclavian nerve branching [11,13]. A local anesthetic mixture was deposited as 9 mL posteriorly/inferior to the nerve complex and 6 mL anteriorly/superiorly, with care to avoid direct contact with the nerve complex (Fig. 2).
3) Clavipectoral fascial plane block
After performing the SCN block, the needle was advanced in a caudal to cranial direction to inject 15 mL of local anesthetic mixture in 0.5 mL aliquots beneath the clavipectoral fascia in order to separate it from the periosteum of the clavicle [12]. The injection was administered at both ends of the clavicle, with 7.5 mL injected on each side (Fig. 3).
The onset of the sensory block was observed from the completion of the local anesthetic injection to the loss of pinprick sensation in the skin overlying the clavicle. The motor activity of the deltoid and biceps muscles was evaluated 20 minutes post-block using the modified Bromage score (MBS) [21]. A score of 4 indicates normal muscle power in the examined muscle groups, 3 indicates decreased power while retaining the ability to function against resistance, 2 indicates the ability to move against gravity but not against resistance, 1 indicates random motor activity of the affected muscle groups, and zero indicates the absence of motor activity. Block failure was defined as the failure to achieve surgical anesthesia within 30 minutes after completing the block procedure. In these cases, the surgery would proceed under general anesthesia, and the patient would be excluded from the study.
The diaphragmatic excursion was evaluated using M-mode ultrasonography of the relevant hemidiaphragm. The range of diaphragmatic descent from the end-expiratory phase to maximum inspiration was documented for analysis. Patients were examined preoperative and intraoperative (1 hour after the block completion). The percentage difference between pre- and post-block values was calculated for analysis. A reduction of 25% to 75% from the baseline value suggests the presence of paresis, whereas a reduction exceeding 75% indicates paralysis [22]. The occurrence of dyspnea or the necessity for oxygen therapy in a patient is considered a clinically significant change.
5. Postoperative care
The postoperative pain management protocol included paracetamol 1 g administered every 8 hours and ketorolac 30 mg IV given every 8 hours. Nalbuphine 10 mg was administered as rescue analgesia when the NRS ≥ 4, with a maximum limit of 160 mg/day [23]. Clavicular pain was evaluated at baseline and hourly for the first four hours, followed by assessments at 6, 8, 12, 18, 20, and 24 hours postoperatively. The potential adverse effects, including hypoxia, dyspnea, hoarseness, hiccups, and Horner's syndrome, were assessed postoperatively within the first 24 hours. Patient and surgeon satisfaction was evaluated using a 7-point Likert-like verbal rating scale [24]. The patient was asked to express his satisfaction at the end of the first 24 hours post-procedure as follows: 1 = extremely dissatisfied, 2 = dissatisfied, 3 = somewhat dissatisfied, 4 = unsatisfied, 5 = somewhat satisfied, 6 = satisfied, and 7 = extremely satisfied.
6. Outcome measures
The primary outcome was the time until the patient's first request for rescue analgesia. The secondary outcomes were the total nalbuphine dosage consumed in the first 24 hours postoperative, the onset of sensory block, the degree of the relevant upper limb motor impairment using the MBS, the ipsilateral diaphragmatic excursion before and one hour after the block, and the NRS scores during the ipsilateral arm movement at predetermined intervals within the first 24 hours. Lastly, satisfaction levels were evaluated for both the surgeon and the patient after the surgical procedure and at the end of the first postoperative day.
7. Sample size
A pilot study was conducted with 10 patients in each group to estimate the mean ± standard deviation (SD) time to the first request for rescue analgesia (in hours) for the ST and CFP block groups. The mean times were 15.30 ± 3.18 hours and 12.96 ± 2.58 hours, respectively. Based on these estimates, with a 95% two-sided confidence level and 80% study power, the required sample size was calculated using OpenEpi, resulting in 25 patients per group. No patient required conversion to general anesthesia in the preliminary pilot study, and given the study's benign nature and short duration, the dropout rate in estimating the sample size was not considered.
8. Statistical analysis
All data were collected, tabulated, and statistically analyzed using IBM Corp., released in 2015 (IBM SPSS Statistics for Windows, Version 23.0; IBM Corp). Quantitative data were represented as mean ± SD or median (interquartile range), while qualitative data were expressed as numbers and percentages. A t-test was utilized for variables with normal distribution, a Mann–Whitney U-test for non-normal distribution, and a paired t-test for paired variables. The Fisher's exact or Chi-square tests were used to compare categorical variables. The level of statistical significance was set at a P value of < 0.05. Bootstrap for the Independent Sample Test (1000) was used to calculate a 95% confidence interval (CI) for data with non-normal distribution.
RESULTS
Fifty-four patients scheduled for middle-third clavicular surgeries were enrolled in this study. Four patients were excluded: two for failing to target the SCN, one due to undetected chronic opioid use during the enrollment stage, and one who declined to participate. The remaining 50 participants were equally randomized to receive either an ST block or a CFP block after selectively blocking the SCN (Fig. 4). No patients required a switch to general anesthesia during the surgery.
There were no substantial differences between the groups regarding the patient's characteristics or surgery duration (Table 1).
The time before the first rescue analgesic request was significantly longer in the ST group (18.76 ± 0.89 hours) than in the CFP group (15.34 ± 1.38 hours), with a mean difference of 3.42 hours (95% CI: 2.76 to 4.08, P < 0.001). A similar finding was observed regarding total nalbuphine consumption in the first 24 hours following surgery, where the ST group exhibited significantly lower consumption (10 ± 0 mg) compared to the CFP group (16.8 ± 6.27 mg), with a mean difference of –6.8 mg (95% CI: –9.17 to –4.4, P < 0.001). The onset of sensory block was comparable in both groups, with 4.92 ± 0.95 minutes in the ST group and 4.72 ± 0.68 minutes in the CFP group, with a mean difference of 0.2 minutes (95% CI: –0.27 to 0.671, P = 0.397).
The CFP group exhibited no impairments in ipsilateral upper limb motor function, as evidenced by an MBS score of 4 for the deltoid and biceps muscles in all patients. In the ST group, there was a notable decline in the motor function of the deltoid or biceps muscles, with 12 cases scoring 3, 11 cases scoring 2, and 2 cases scoring 1. This indicated a statistically significant difference (P < 0.001) (Table 2).
Regarding ipsilateral diaphragmatic excursion, there was no statistically significant difference between the groups preoperatively. Following the procedure, the mean diaphragm range of motion was significantly lower in the ST group, measuring 4.18 ± 0.46 cm, compared to the CFP group, which measured 5.06 ± 0.47 cm, with a mean difference of –0.88 cm (95% CI: –1.14 to –0.62, P < 0.001) (Table 3). The percentage difference between pre- and post-block values in the CFP group was not statistically significant. Conversely, two patients in the ST group exhibited reductions exceeding 25% from their baseline values (28% and 26.3%). The remaining participants in the ST group demonstrated reductions of less than 25% in their baseline diaphragmatic excursion values. Despite the statistically significant difference, no patients showed symptoms of respiratory insufficiency or required oxygen therapy.
The NRS scores did not show statistically significant differences between the groups before and during the first 4 hours after surgery. However, the NRS was significantly higher in the CFP group at 6, 8, 12, 16, and 24 hours after the operation, whereas it was significantly higher in the ST group at 18 hours post-surgery (Table 4). Patient and surgeon satisfaction did not show a statistically significant difference between the two groups (Table 5). No adverse events were observed within the first 24 hours postoperatively.
DISCUSSION
This comparative randomized study assessed the analgesic properties of the selective SCN block with either the ST of the brachial plexus or CFP block for mid-third clavicular surgeries. The study showed that both groups provided adequate surgical anesthesia with extended postoperative analgesia. The ST group demonstrated superior analgesic effects, lasting longer before the first rescue analgesia and with less nalbuphine consumption than the CFP group. However, preserving the phrenic nerve and lacking upper limb motor impairment may favor the CFP block, particularly when upper limb motor activity or pulmonary function is more clinically significant.
The findings indicate that the analgesic effects of the ST group exceeded those of the CFP group in relation to the time until the first rescue analgesia was administered. Nonetheless, the minimal clinically important difference (MCID) in NRS pain scores at various time points (MCID = 1.5) and the overall nalbuphine usage over 24 hours (MCID = 10 mg) was not achieved.
The NRS scores were higher in the CFP group at 6, 8, 12, 16, and 24 hours after surgery, whereas the ST group had higher scores at 18 hours postoperatively. The inconsistent finding at 18 hours may be due to the method used for evaluating pain intensity, which followed predetermined intervals within the first 24 hours postoperatively. The assessment of the NRS at 18 hours coincided with the washout of the ST block effects in most patients. In contrast, the block effects in the CFP group diminished earlier, and these patients had already been administered standard rescue analgesics for pain control.
The findings of the current study align with prior research on regional block fo shoulder surgeries [13]. Previous studies demonstrated that selective ST blockade offers pain relief comparable to that achieved with the ISB in these surgical procedures. Studies have also examined the use of the CFP block in combination with the intermediate cervical plexus block (ICPB) for the middle-third clavicular surgeries [25]. Consistent with the present findings, these investigations concluded that the CFP block provides adequate surgical anesthesia while significantly reducing diaphragmatic involvement compared to the ISB combined with ICPB.
Previous studies reported conflicting effects of ST block on diaphragmatic function [8,26]. Kim et al. [8] demonstrated that the ST block effectively preserved diaphragmatic function while providing significant analgesia during shoulder arthroscopic surgeries compared to the ISB. The findings of Robles et al. [26] are inconsistent with these results. The investigation into the effects of the ST block on respiratory parameters after shoulder surgeries demonstrated that a significant number of patients showed both clinical and radiological signs of diaphragmatic impairment compared to those undergoing the traditional ISB.
In the current study, the CFP block effectively preserved upper limb motor activity and diaphragmatic movement. In contrast, the ST block led to a decline in the motor activity of the deltoid and biceps muscles. Additionally, patients who received the ST block experienced a decrease in the range of diaphragmatic movement, although this change was not clinically significant.
Our study showed that selective SCN block augmented the clavicular anesthesia and postoperative analgesia of the ST and the CFP blocks. Consistent with the present findings, Sivashanmugam et al. [9] found that combining the selective SCN block with the ST block, the SCUT block, was adequate and could be used solely for clavicular surgeries. It is important to highlight that the first report of pain in their study occurred at 5 ± 1.2 hours, whereas in the current research, it occurred at 8 hours in the ST group. The observed difference can be ascribed to the reduced anesthetic volume of 5 mL in their study compared to the 15 mL utilized in this trial.
The current study has some limitations that should be considered. First, the study was conducted at a single center with a relatively small sample size and a tailored local anesthetic regimen. Second, the authors did not evaluate the efficacy of blocks for procedures involving the clavicle's periphery. Third, pain intensity measurements were evaluated at specified intervals, which revealed inconsistent results at specific time points due to the timing of rescue analgesic administration in both groups. Therefore, further research is needed to establish a consensus on the optimal approach to regional clavicular anesthesia.
In conclusion, combining the selective SCN block with the ST and CFP blocks effectively provided surgical anesthesia and postoperative analgesia for procedures involving the middle third of the clavicle. The ST block showed better analgesic properties than the CFP block. Unlike the ST block, the CFP block maintained phrenic nerve sparing and upper limb motor function. Therefore, the authors recommend that patients undergoing clavicular fracture surgeries should be given the option of either technique for their operative anesthesia or included in a multimodal analgesia plan during the perioperative period. This should be conducted while considering the patient's comorbidities and clinical context.
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