Assessment of Two Distinct Anatomical Landmarks for Suprascapular Nerve Injection: A Cadaveric Study.

Abstract

The suprascapular nerve block (SSNB) is a commonly used procedure for the management of pain in various shoulder pathologies. Both image-guided and landmark-based techniques have been utilized successfully for SSNB, though more consensus is needed regarding the optimal method of administration. This study aims to evaluate the theoretical effectiveness of a SSNB at two distinct anatomic landmarks and propose a simple, reliable way of administration for future clinical use. 14 upper extremity cadaveric specimens were randomly assigned to either receive an injection 1cm medial to the posterior acromioclavicular (AC) joint vertex or 3cm medial to the posterior AC joint vertex. Each shoulder was injected with a 10ml Methylene Blue solution at the assigned location, and gross dissection was performed to evaluate the anatomic diffusion of the dye. The presence of dye was specifically assessed at the suprascapular notch, supraspinatus fossa, and spinoglenoid notch to determine the theoretic analgesic effectiveness of a SSNB at these two injection sites. Methylene Blue diffused to the suprascapular notch in 57.1% of the 1 cm group and 100% of the 3 cm group, the supraspinatus fossa in 71.4% of the 1 cm group and 100% of the 3 cm group, and the spinoglenoid notch in 100% of the 1 cm group and 42.9% of the 3 cm group. Given its superior coverage at the more proximal sensory branches of the suprascapular nerve, a SSNB injection performed 3 cm medial to the posterior AC joint vertex provides more clinically adequate analgesia than an injection site 1cm medial to the AC junction. Performing a SSNB injection at this location allows for an effective method of anesthetizing the suprascapular nerve.