Simplifying ultrasound suprascapular notch exploration for regional anesthesia

The suprascapular nerve block at the notch level is commonly performed. However, ultrasound identification of the notch remains challenging due to significant anatomical variability. We conducted a combined ultrasound and dry bone anatomical study to better characterize the suprascapular notch and develop a simplified classification system tailored for anesthesiologists.

We performed an observational anatomical study on 71 dry scapulae. The shape of the suprascapular notch was assessed using the Rengachary classification. We also measured the maximum depth (the deepest point of the notch) and the superior transverse diameter (the maximum distance between the edges of the notch). Additionally, an ultrasound observational study was conducted on 108 healthy volunteers to evaluate notch shape and determine the same measurements.

Based on ultrasound findings, the most common notch types were type III (34%, n=70), type II (31%, n=63), and type IV (20%, n=42). Non-parametric analysis revealed no significant association between notch type and participant age, sex, height, or weight. Furthermore, the distribution of notch types did not differ significantly between the left and right sides. For types II-IV, the median maximum depth was 5 mm [4-6], and the median superior transverse diameter was 18 mm [15-20]. Similar results were observed in the dry scapula analysis, though a high degree of variability in notch types was noted.

Our findings revealed that notch types II-IV, according to the Rengachary classification, are the most prevalent. Nonetheless, the suprascapular notch shows substantial anatomical diversity. To address this, we propose a simplified ultrasound-based classification, centered on the presence or absence of a clearly identifiable notch. This system aims to support clinical decision-making in regional anesthesia and enhance consistency in practice.