Labandeyra, Hipólito

Background The Midclavicle Block achieves balanced methylene blue spread across both anterosuperior and posteroinferior periosteal surfaces in cadavers with intact clavicles. Objective To evaluate the anatomical distribution pattern of the Midclavicle Block in cadaveric specimens with midshaft clavicle fractures, with a focus on periosteal coverage and involvement of the fracture site. Methods An anatomical study was conducted on 10 cadavers (20 clavicular regions). A midshaft clavicle fracture model was created, and the Midclavicle Block technique was applied under ultrasound guidance. A methylene blue solution was injected, and dissections were performed to evaluate dye spread primarily in the deep muscular and the clavicular plane, including the fracture site. Probabilistic maps of dye distribution were generated. Results The anatomical dissection in the deep muscular plane revealed consistent staining of the fracture site in all specimens, along with the subclavius muscle and the clavipectoral fascia, while the pectoralis minor muscle remained unaffected in every case. As the dissection progressed toward the infraclavicular brachial plexus plane, no staining of the plexus was observed, with dye spread restricted to the subclavius muscle and adjacent clavipectoral fascia. The mean staining of the anterosuperior and posteroinferior periosteal surfaces was 55.5% (95% CI: 50.6% to 60.4%) and 53.8% (95% CI: 49.5% to 58.1%), respectively. The highest dye concentration was observed in the middle third of the clavicle, corresponding to the fracture zone. Conclusion The Midclavicle Block resulted in effective periosteal coverage and targeted fracture site staining. Clinical studies are needed to confirm its in vivo efficacy, given the limitations inherent to cadaveric specimens.