In this retrospective study, the 48-h fentanyl consumption was significantly less in the T group as compared to the E group. Fentanyl requirements were on higher side after the 18th hour in group E. Though TEA is not always shown to be the most effective modality in MRFs (Adhikary et al., 2019a) and the outcomes of the TEA administration have been inconsistent in the MRFs scenario (Peek et al., 2019; McKendy et al., 2017), our study confirms otherwise.

Major limitations of TEA are it is technically more demanding and the incidence of hypotension, lower limb weakness, and retention of urine dictates intensive care admission and improved nursing care (Zaw et al., 2015; Tran et al., 2016). Though considered as a gold standard, TEA is contraindicated in neuraxial or head injuries and anticoagulant therapy. Recent study incriminates TEA worsening in-hospital complications and increase length of hospital stay (Carrier et al., 2009). The TPVB is another alternative for unilateral MRF-related pain (McKendy et al., 2017; Womack et al., 2019; Ho et al., 2011). But it has a steep learning curve and a risk of procedure-associated complications such as a pulmonary hemorrhage (Thomas et al., 1999; Kus et al., 2013) with landmark technique and a pleural puncture with ultrasound guidance have been reported. Further, we perceive in posterior rib fracture the TPVB would be a difficult proposition due to distorted anatomy. A contrast study demonstrated an US-guided TPVB acts through a unilateral epidural spread with volumes of 20ml (Diwan & Nair, 2020a).

In a thoracic ESPB, the injection point is more posterior close to the posterior rib fracture site and the target is the erector spinae plane (ESP), where the dorsal rami are positioned. At a target 3-cm lateral to the spinous process, injections made deep to the erector spinae muscle (ESM) demonstrated a cephalad to caudal, paravertebral, and an epidural spread (Wardhan & Kantamneni, 2020; Forero et al., 2016; Adhikary et al., 2018).. A cadaveric study and a clinical case report demonstrate the dye spread from the erector spina plane at the level of T5 into the paravertebral and epidural spaces, though this may not be reproduced at all levels (Diwan et al., 2019; Diwan & Nair, 2020b). Moreover, we hypothesize that in posterolateral MRF’s with fractured costotransverse junctions, ribs, and the ligaments a dorsal local anesthetic (LA) deposition in the erector spinae plane would percolate on ventral aspect into the thoracic paravertebral space (PVS) and the epidural spaces. One of the major advantages of thoracic ESPB is its implementation in anticoagulated patient, which of course is a contraindication for thoracic PVB and TEA (Adhikary et al., 2019b) The serratus anterior plane block (SAPB) is suggested ahead of TEA, and thoracic PVB in an algorithm proposed for the management of MRFs (May et al., 2016) has shown a limited posterior spread of LA with SAPB (Kunigo et al., 2018). Similarly, though a thoracic ESPB is currently included in the algorithm for pain management (Williams et al., 2020) of multiple rib fractures, to our knowledge, a comparison between two or more techniques is lacking.

A small sample exploratory analysis of a retrospective data has its inherent limitations. To demonstrate superiority of block efficacy amongst comparable techniques requires a larger population and a prospective study. In consequence, it is impossible to recommend TEA as the choice for unilateral MRF’s. If parameters like incentive spirometry and pain on cough were not evaluated could be another limitation. Though both groups included infusions through the catheter, the initial volumes and infusion volumes vary in the T and E groups, as the latter is closed low-volume compartment and the former is open and high-volume compartment. Catheters and infusion may be unavailable and are costly. Moreover, many anesthesiologists in clinical practice tend perform single bolus or intermittent injections through the catheter for varying reasons. Besides, in polytrauma patients, it is difficult to distinguish the correct pain scores as these patients receive opioid infusions.

Though ESPB is effective in improving pulmonary function with a modest reduction in pain scores when implemented in rib fracture (Adhikary et al., 2019a; Luftig et al., 2018), in our study, both groups had patients with polytrauma and the analgesic outcomes of TEA and thoracic ESPB may have been obscured. Probably a sub-group analysis of patients with fractured ribs of 3, 3–5, and more than 5 and the effects of the interventional technique should have been performed. However, in our study, a small sample size is a limitation for a sub-group analysis. All these flaws could be addressed by performing prospective, well-designed, randomized controlled trial between interventional groups addressing pain management for MRF’S.

For its ease of insertion, maintenance of catheter, and infusion without any adverse effects, thoracic ESPB remains the first choice for all posterolateral MRF’S in our institution. Our study emphasizes the role of thoracic ESPB as an alternative technique for posterior and lateral rib fractures and add to the existing literature (Adhikary et al., 2019a; Luftig et al., 2018).