Umbrella over erector spinae plane block: wide coverage, narrow clarity

TO THE EDITOR

We read with interest the umbrella review by De Cassai et al. [1] assessing the erector spinae plane block (ESPB) for vertebral surgeries. The synthesis confirms reduced 24-hour opioid use with ESPB and statistically lower early pain scores, yet the clinical magnitude of the pain reduction appears modest (mostly < 1/10 point on 0–10 scales). The article also reports consistent decreases in postoperative nausea and vomiting (PONV). Together, these are encouraging signals for multimodal analgesia. We would like to offer three considerations that may refine the interpretation and guide future work.

First, the umbrella review excluded systematic reviews and meta-analyses (SRMAs) that used other regional anaesthesia (RA) techniques as comparators, retaining those with sham/no block [1]. This design clarifies ‘any-benefit versus none,’ but it limits the fundamental question most clinicians face—which RA technique is preferable for a given spine procedure? Recent SRMAs comparing ESPB with active comparators such as the thoracolumbar interfascial plane block or local wound infiltration suggest that relative effectiveness may vary depending on the comparator and surgical context [2,3]. Notably, at least one included SRMA appears to have pooled trials with non-placebo comparators (e.g., local wound infiltration) [3]. Clarifying how such SRMAs were handled would help reconcile the stated eligibility criteria with the evidence summarized.

Second, ESPB was associated with an estimated reduction of 8.70 to 18.69 mg in 24-hour morphine milligram equivalents (MME), while improvements in pain scores were minor [1]. Because well-run perioperative pathways aim to minimize pain in both groups, small numerical differences are expected. We agree that minimal clinically important difference (MCID) thresholds should not be applied dogmatically; however, future syntheses could prioritize outcomes that convert opioid sparing into tangible patient benefits, e.g., time-to-first rescue, opioid-free hours, pruritus/sedation, PONV, readiness for mobilization, and quality-of-recovery metrics alongside pain scores. The distinction between statistical significance and clinically meaningful benefit, as well as the need to interpret pain outcomes considering the minimal clinically important difference, has been emphasized in recent postoperative pain literature [4].

Third, the review highlights high heterogeneity across nearly all outcomes with limited success in exploration and no meta-regression across SRs; in addition, the corrected covered area (CCA) of approximately 24% signals substantial overlap of primary trials across SRs, reducing independence among pooled SR-level estimates [1]. Future research may reduce heterogeneity through standardized reporting of ESPB technique (block level, laterality, timing relative to incision, injectate composition), uniform outcome definitions, predefined subgroup analyses, and consistent opioid conversion metrics.

To conclude, we concur with the authors’ statement that comparative effectiveness versus other blocks and infiltration techniques is the clinically meaningful next question [1]. A prospectively registered overview, focusing on active comparators (and, where feasible, a network meta-analysis), would directly inform the choice of technique across diverse spine procedures. We commend the authors for openly discussing limitations and for registering their protocol. We hope these suggestions help sharpen future evidence syntheses and translate ESPB’s opioid-sparing signal into patient-centered gains.