Measuring, valuing, and incorporating patient and caregiver productivity costs in economic evaluations: a scoping review and environmental scan.

Ultrasound-guided interscalene brachial plexus block is recommended by procedure-specific postoperative pain management (PROSPECT) guidelines as an effective analgesic strategy for shoulder surgery, including continuous catheter techniques when prolonged analgesia is required []. Conventional intrafascial interscalene block has historically been associated with a high incidence of hemidiaphragmatic paresis due to phrenic nerve involvement, which may limit its use in patients with reduced respiratory reserve [,]. Extrafascial techniques have therefore been investigated as strategies to preserve analgesia while reducing hemidiaphragmatic paresis and respiratory impairment compared with conventional intrafascial approaches [–]. These approaches have been described using a lateral-to-medial trajectory, positioning the needle or catheter tip immediately outside the brachial plexus sheath at the C5–6 level [,]. Extraplexus injection outside the brachial plexus sheath has been reported to provide effective analgesia comparable to an intraplexus approach, supporting further evaluation of targets outside the immediate perineural space for shoulder surgery []. In the context of multimodal analgesia for shoulder surgery, a reliable catheter placement method is needed that can be integrated into routine perioperative practice without requiring advanced expertise in fascial plane identification. The middle scalene muscle (MSM) is a substantially larger anatomical target than the narrow scalene groove; targeting the MSM body rather than the immediate perineural space may therefore offer technical simplicity and reproducibility while still allowing effective local anesthetic delivery. However, detailed technical guidance on achieving stable intramuscular catheter positioning within the MSM is limited. Continuous perineural infusion has been reported to prolong analgesia and reduce opioid requirements compared with single-shot techniques in a range of surgical settings []. A technique that targets a large, clearly identifiable anatomical structure while avoiding direct proximity to neural elements would therefore represent a valuable addition to the multimodal analgesic armamentarium across different levels of operator experience. Furthermore, with a lateral-to-medial approach, the catheter must traverse the MSM transversely before reaching the scalene groove at its tip; partial postoperative withdrawal could theoretically move the tip into the muscle belly and away from the target plexus. With our cranial-to-caudal approach, the catheter is advanced along the MSM parallel to the transverse process; partial withdrawal would theoretically be more likely to keep the tip within the groove region. To our knowledge, the influence of catheter insertion direction within the MSM on catheter tip stability relative to the scalene groove has not been evaluated. Therefore, we developed a novel cranial-to-caudal out-of-plane technique using the C6 transverse process as a reliable bony landmark, based on the anatomical study of Martinoli et al. []. Unlike conventional lateral-to-medial extrafascial approaches, our technique advances the needle in a cranial-to-caudal direction toward the acoustic shadow of the C6 posterior tubercle, positioning the catheter tip within the MSM in close proximity to the scalene groove, as illustrated in . We hypothesised that this trajectory would keep the catheter more parallel to the scalene groove during cervical movement, potentially improving tip stability and the consistency of local anesthetic delivery. The present case series describes the feasibility of this novel technique and the analgesic outcomes observed in patients undergoing overnight-admission shoulder surgery within a standardized multimodal analgesic regimen.