Proximal humeral fracture is common and may account for up to 5% of all fractures in the aging population (1). It will affect quality of life, and even increase mortality (2). Treatments for proximal humeral fracture (PHF) include non-operative care and surgery. For the elderly patients with surgical indications, especially those who are afflicted with severe cardiac or pulmonary comorbidity, the choice of anesthesia is a dilemma. Except for general anesthesia (GA), surgery under regional anesthesia (RA) is also an ideal choice. It may preserve spontaneous respiration and minimize the risk of complications associated with GA (3). However, perfect RA presents a unique challenge to anesthesiologists since the relevant innervation is complicated. No single nerve block technique can cover the entire surgical region (4).

The deltopectoral approach for PHF surgery involves the anterior shoulder and the proximal upper arm. The innervation mainly originates from the cervical plexus and the brachial plexus (5, 6). However, the hybrid technique of the superficial cervical plexus block and the interscalene block, which is an effective mode of RA in clavicle and shoulder surgery (7–9), cannot always provide sufficient surgical anesthesia for the patients undergoing PHF surgery. In previous studies, the branches stem from the upper thoracic nerves (T1–T2, even T3), nearly impossible to be covered by a brachial plexus block, were considered to contribute to the innervation of the upper arm as well (10, 11). Zhao (12) also recommended the T2 thoracic paravertebral block (TPVB) as a supplement for RA in PHF surgery since the thoracic paravertebral space (TPVS) houses the ventral rami of nerve roots and allows local anesthetic to spread to T1 and T3. However, limited evidence is available from randomized controlled trials. Therefore, we aimed to investigate whether adding a T2 TPVB is useful and necessary to avoid the occurrence of incomplete regional anesthesia in elderly patients undergoing deltopectoral approach PHF surgery.

This randomized, observer-blinded, controlled trial was approved by the Ethics Committee of Shanghai Sixth People's Hospital (No. 2019-030, March 28, 2019, Chairperson Prof Weiping Jia) and prospectively registered at ClinicalTrials.gov (NCT03919422, April 14, 2019) before the enrolment process started on May 5, 2019.

The patients aged 65 or older, ASA grade I-II, BMI <30 kg/m², scheduled for elective deltopectoral approach PHF surgery between May 2019 and August 2020 were recruited. Exclusion criteria included a request for GA, inability to cooperate, contraindication to RA, multiple traumas, uncontrolled systemic diseases, and allergy to ropivacaine. An independent investigator (HZ) generated the randomized allocation sequence and concealed the allocation results in opaque sealed envelopes. After providing written informed consent, the participants were randomly and equally allocated to receive either combined interscalene brachial plexus with superficial cervical plexus block (IC group) or IC block supplemented with T2 TPVB (ICTP group). On the surgical day, an anesthetic nurse provided one envelope per patient to the anesthesiologist who administered the regional block (XW). After the regional block was finished, this anesthesiologist had no further role in the subsequent procedure. The surgeons, nurses, research assistants, intraoperative anesthesiologists, and outcome assessors were all kept blinded to the allocation.

Among 41 eligible patients, a total of 80 patients were included and divided equally into two groups and all patients received the interventions. The Consolidated Standards Of Reporting Trials (CONSORT) flow diagram is depicted in Figure 1. The baseline demographic data show no statistically significant differences between the two groups (Table 1).

The success rate of regional anesthesia in the ICTP group was higher compared with the IC group (77.5 vs. 52.5%, p = 0.019, Figure 2). Remifentanil was required and effective in 32.5% of patients in IC group, while 17.5% in ICTP group (p > 0.05). Conversion to GA was performed in 15% of patients in the IC group and 5% in the ICTP group, respectively (p > 0.05).

The sensory block at the medial proximal upper arm (including partial and complete block) was achieved in 85% of patients in the ICTP group, whereas only 10% in the IC group (p < 0.001). There was no significant difference in the rate of sensory block at the supraclavicular region, deltoid region, or lateral proximal upper arm between groups (p > 0.05). The sensory block assessment is summarized in Figure 3. The two study groups had a similar incidence of intraoperative adverse reactions (Table 2). No block procedure-related complications occurred in either group.

The results of our study indicated that supplementary T2 TPVB was helpful to decrease, but not absolutely avoid the occurrence of incomplete RA. With the assistance of a minor dose of remifentanil, the majority of patients avoided conversion to GA. These findings provide us evidence to discuss the pending question of whether it is necessary to perform an additional upper thoracic nerve level block with the cervical-brachial plexus block-based regional anesthesia during PHF surgery.

The deltopectoral approach covers from the anterior shoulder to the proximal upper arm. The innervation (including dermatome, myotome, and sclerotome) mainly involves supraclavicular nerve (C3–C4), suprascapular nerve (C5–C6), axillary nerve (C5–C6), lateral pectoral nerve (C5–C7), and musculocutaneous nerve (C5–C7) (16–18). These nerves originate from the cervical and brachial plexus, but their contributions vary across individuals. In the present study, the superficial cervical and interscalene brachial plexus blocks provided complete surgical anesthesia for merely 52.5% of the patients in the IC group. It means that this surgical region is not consistently innervated by the above nerves. Relatively, with the supplement of T2 TPVB, 77.5% of the patients in the ICTP group did not require rescue anesthesia. Although this was not an ideal outcome for clinical application even achieved statistic difference, it at least proved that adding a T2 TPVB was beneficial to improve the regional anesthetic effect in part of the population.

The reason for incomplete regional anesthesia possibly is multifactorial. Firstly, the inferior trunk perhaps was not thoroughly blocked due to the fact that the interscalene block mainly targets the superior and middle trunks. The C8 root is difficult to be absolutely blocked by the spread of LA during the interscalene groove or TPVS (19). Therefore, the combination mode of different approaches should be improved for a more comprehensive brachial plexus block. The hybrid technique of interscalene and supraclavicular approach, interscalene and C8 block, or selective trunks block was recently proposed to completely block the three brachial trunks in PHF surgery (11, 20–22). However, none of the modes was supported by neither the large cohort of patients nor the randomized controlled trial. Interestingly, the authors also mentioned that the above techniques were unable to provide a sensory block to the medial aspect of the proximal upper arm due to the missing block of T2–T3. Regrettably, none of them proposed adding an upper thoracic nerve block in PHF surgery. Secondly, T2 TPVB failed to block the sensory of the medial proximal upper arm in 15% of patients, which might be attributable to the unexpected spread of local anesthetic (LA). In a previous study, the researchers administered TPVB at the T3 level and found that the LA mainly spread to T3–T5 rather than T2 (23). The study of Naja and Lönnqvist (24) also proved that sensory spread was usually observed below the level of injection, with very limited cephalad spread. The study conducted by Ruscio et al. (25) concluded that the sagittal approach TPVB had a higher success rate than both transversal in-plane and out-of-plane techniques (93/81/83%). In a cadaver study, a higher injection volume resulted in a larger number of stained thoracic nerves (26). Thus, a modified TPVB technique based on volume or approach might provide a more successful RA.

Under this situation, to weigh the pros and cons, the risks of TPVB should be taken into account. In our study, the incidences of adverse reactions were not significantly different between the two groups, although seemed a little higher compared with the previous studies (27–29). This slight discrepancy might be due to the sensibility of remifentanil in the elderly (30). As the method described by Pangthipampai et al. (31), we also injected the LA into the apex of TPVS at the level of the transverse process, which is far from the intervertebral foramen. This will help to prevent unintentional epidural spread and neuraxial complications. However, zero block-related complication does not mean no potential risk. The necessity of adding a T2 TPVB should be considered seriously since a minor dose of remifentanil infusion was also an effective rescue option. To anxious patients, GA with LMA is more acceptable rather than TPVB or opioids.

We acknowledge some limitations of this study. Firstly, all the block procedures were performed by a single anesthesiologist. This limited the generalizability of our findings, although it reduced performance bias. Secondly, to reduce the incidences of diaphragmatic paralysis and pneumothorax, the combination use of supraclavicular approach and interscalene approach brachial plexus block was not adopted in our study, which might be relevant to the insufficient anesthesia. Lastly, to evaluate the risks of T2 TPVB in elderly patients, we excluded the young population. This might lead to selection bias.

In conclusion, supplementary T2 TPVB is useful to avoid insufficient regional anesthesia during PHF surgery in some elderly patients. However, considering the potential risks, it is not an ideal option while a minor dose of remifentanil can provide a satisfactory rescue effect. Whether to apply this technique should be decided according to the situation of the patient and the experience of the anesthesiologist.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by Ethics Committee of Shanghai Sixth People's Hospital. The patients/participants provided their written informed consent to participate in this study.

JZ and WJ conceived and led the study design. XW prepared the draft of this manuscript and performed the regional block procedures. HZ administered the randomization and group allocation. QZ recruited the participants. ZX and YC collected the outcome data. JL analyzed the data. All authors read and approved the final version of the manuscript.

This trial was supported by the Research Foundations of Shanghai Municipal Health Commission (Nos. 202040257 and 201940510).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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