Cadaveric and Ultrasound-Guided Evaluation of Two Needling Approaches Targeting the Pectoralis Minor Muscle: A Pilot Feasibility Study

<b>Background</b>: The pectoralis minor muscle can be a source of musculoskeletal-related chest pain by contributing to thoracic outlet syndrome. Needling interventions applied to chest wall muscles have an inherent risk of puncturing sensitive structures, e.g., the pleura. <b>Objective</b>: The objective of this study was to preliminarily investigate the safety and accuracy of two needling approaches targeting the pectoralis minor muscle. <b>Methods</b>: A pincer- and flat-needle approach targeting the pectoralis minor muscle was conducted in five Thiel-embalmed cadavers and 10 healthy volunteers by an experienced and a novice clinician. The needle was inserted until the clinician considered that the pectoralis minor muscle was reached. Each clinician conducted 10 needle insertions with each approach. In cadavers, the accuracy of needle placement was identified with both ultrasound imaging and anatomical dissection. In healthy volunteers, needle placement accuracy was evaluated with ultrasound imaging. <b>Results</b>: Accurate needle penetration of the pectoralis minor muscle was 80-90% and 40-70% for experienced and novice clinicians, respectively, with the pincer approach. One pleural puncture was observed in one cadaver specimen with this approach by the novice clinician. Accurate needle penetration of the pectoralis minor muscle was 100% and 90% for experienced and novice clinicians, respectively, with the flat approach. The novice clinician required 3.5 times longer to perform the flat approach than the experienced clinician. <b>Conclusions</b>: The results of this pilot feasibility study suggest that a pincer-needle approach seems to be less accurate than the flat-needle approach and substantially more error-prone for a novice clinician, which, in a clinical context, could pose a potential risk of pneumothorax based on the pleural puncture observed in one cadaver specimen. In contrast, our preliminary results revealed that the flat-needle approach could have better accuracy and safety, particularly when performed under real ultrasound guidance.