RESUMO
OBJECTIVE: Despite their recognized advantages, infraclavicular blocks, especially with the pericoracoid approach, are underutilized because the lack of simple anatomical landmarks. The goal of this study is to determine a simple, reliable and reproducible reference point by means of magnetic resonance imaging (MRI), using the anterior extremity of the coracoid process, and the pectoralis minor as a tactile reference point. METHOD: Sagittal and para-sagittal MRI sections at the coracoid process were performed on 11 patients. The relationships between the coracoid process, the nerve-vessel bundle, the pectoralis minor and the skin were measured. RESULTS: The optimal puncture point for a needle introduced strictly in an anterio-posterior direction in a supine, alert patient is located 2 cm within and 2.5 cm below the coracoid process. The injection point, defined as the distance between the skin and the tip of the needle lying in the centre of the visualized nerve-vessel bundle, is located an average of 5 cm from the skin (mean 5.02 cm, with a standard deviation of 1.03 and a confidence interval of 0.91). This injection point goes from 0.4 cm (at the most anterior part of the bundle) and 1.75 cm (at the most posterior part), with an average 1 cm from the posterior surface of the pectoralis minor (tactile reference point). Neither body mass index nor sex influence significantly the variables measured. CONCLUSIONS: The reference points defined here could allow easy and reproducible performance of this relatively simple block and make it more effective.
