2025/10/18 by Gillian D. Saffy, G Lamacraft, J. Janse van Rensburg +1 · 1 voice · 1 citation
Medicine · #Anesthesia and Pain Management #Spine and Intervertebral Disc Pathology #Spinal Hematomas and Complications
paper · pdf · doi:10.1111/anae.70040
openalex publication_date 2025/10/18 · openalex created_date 2025/10/18 · openalex updated_date 2026/07/26
The erector spinae plane block, first described in 2016 for managing chronic neuropathic pain, is an effective ultrasound-guided technique for providing thoracic analgesia [1]. However, similar lumbar blocks have been less successful, likely due to anatomical differences in the fascial planes [2]. The lumbar paraspinal muscles are thicker, and the thoracolumbar fascia is more prominent [3], serving as a barrier to fluid spread [4]. The clinical effect of a lumbar erector spinae plane block depends on where the injectate spreads [2-4]. Anterior spread to the paravertebral space, epidural space or lumbar plexus is necessary for analgesia in hip [5] or abdominal surgeries, whereas posterior spread is useful for spinal surgery [6]. We aimed to characterise injectate spread after lumbar erector spinae plane block to clarify its clinical applications. We undertook a prospective, interventional study of 12 patients with chronic hip pain who were receiving therapeutic hip blocks. We did not study patients with BMI > 30 kg.m-2 or other contraindications for magnetic resonance imaging (MRI) or regional blockade. Following the hip block, a baseline lumbar spine MRI scan was performed. The patient was then positioned prone. We injected 30 ml 0.9% saline into the erector spinae plane at the L4 level on the contralateral side to the hip block. An ultrasound-guided, parasagittal, in-plane technique was used to direct the needle to the posterolateral tip of the L4 transverse process. We performed an MRI scan 30 min after the injection to investigate injectate spread, and a senior radiologist analysed each image to record the anatomical spread (Fig. 1). We found that injectate spread was directed posteriorly in all patients into the erector spinae muscles. In four patients, injectate spread was directed anteriorly to structures where nerves would be blocked. In one patient, injectate spread was anterior but only into the quadratus lumborum muscle and not an area where nerves would be blocked. Mean (SD) craniocaudal spread of injectate was 140 (25.2) mm, covering 5.7 (1.1) vertebral levels. This yields 5.2 ml of injectate per vertebral level, consistent with previous studies (Table 1). The consistent posterior spread indicates the lumbar erector spinae plane block may yield reliable analgesia for spinal surgery. However, the unpredictable anterior spread suggests it is less reliable for surgeries requiring anaesthesia to the ventral rami or related structures. This difference may be because injectate spread is determined by needle tip position relative to the middle layer of the thoracolumbar fascia. The thick, dense fascial layer acts as a barrier, which compartmentalises the injectate [3]. Some may suggest placing the needle tip anterior to the middle thoracolumbar fascia for anterior spread, but our study did not investigate this needle tip position. The operator technique presented challenges. The depth of the lumbar transverse processes made visualising the L4 transverse process difficult. Despite confirmation of needle position by feeling the needle abut the bone and observing the erector spinae muscles lift, we cannot dismiss the possibility that the needle tip entered the middle thoracolumbar fascia during injection, allowing for anterior spread on the five occasions this occurred. Patient differences in the thickness and porosity of the middle thoracolumbar fascia could also contribute to unpredictable spread. Flaviano et al. placed the needle tip anterior to the tip of L3, L4 and L5 deliberately to achieve a satisfactory block for hip surgery [7]. Practitioners can tailor the needle tip position anterior to the middle thoracolumbar fascia to achieve more predictable anterior spread when required. The volume of injectate determines the spread. Our finding of 5.2 ml per lumbar vertebral level is consistent with existing literature [8], but using a higher volume, such as 40 ml as seen in other studies [5, 6], might lead to more frequent anterior spread. We observed that some patients experienced discomfort towards the conclusion of the injection due to tissue distension, which suggests not all participants tolerated a higher volume. Study limitations include a small sample size and the use of saline. We recommend further research using higher-quality ultrasound to better identify the middle thoracolumbar fascia and its relationship to the needle tip position to achieve more predictable spread. A Central University of Technology/University of the Free State collaboration grant supported this study. This grant did not exert influence on the researchers' data acquisition, interpretation or compilation of findings. We acknowledge Johan Botes for his assistance in finalising and submitting the manuscript. No competing interests declared.