Midclavicle block: An anatomical study.

Background: Recent studies indicate that clavipectoral fascia plane block (CPB) efficacy may stem from injectate distribution to the anterosuperior clavicular periosteum. We conducted an anatomical study combining the CPB with injection within the subclavius muscle.

Objective: Our hypothesis was that the anaesthetic injectate would fully cover both the anterosuperior and posteroinferior surfaces of the clavicular periosteum in the midclavicular region.

Design: Observational human cadaver study.

Setting: Laboratory of Surgical Neuroanatomy, Unit of Anatomy and Human Embryology of the Faculty of Medicine and Health Sciences, University of Barcelona.

Participants: Five fresh human cadavers.

Interventions: The cadavers received both a CPB and subclavius muscle injections under ultrasound guidance in 10 clavicular regions.

Main outcome measures: After the procedures on the cadaveric models, an anatomical dissection by planes was performed to evaluate the distribution pattern of methylene blue on the clavicular periosteum. A probabilistic map of the colour spectrum and staining temperature on the clavicular surfaces was generated.

Results: Methylene blue stained 37 ± 16% of the anterosuperior surface and 23 ± 13% of the posteroinferior surface of the clavicular periosteum, particularly in the middle third of each surface. Although the staining did not achieve complete circumferential coverage or perfect alignment between the surfaces, the areas exhibited a close relationship, indicating significant distribution and relevant coverage.

Conclusion: Our anatomical study demonstrates that the midclavicular block achieves effective distribution around the middle third of the clavicle, although complete circumferential anaesthesia of the clavicular periosteum was not achieved. Although this block may provide periosteal and bone anaesthesia, it does not address other sources of pain, such as muscle spasms and skin components. Additional clinical studies are needed to evaluate the overall efficacy of this dual block technique for clavicle surgery.