A comparison of risk between the lateral decubitus and the beach-chair position when establishing an anteroinferior shoulder portal: A cadaveric study

Purpose: The purpose of this study was to assess, using a technique that minimally distorts the normal anatomy, the risk of injury when establishing a 5 o'clock shoulder portal in the lateral decubitus versus beach-chair position. Methods: The anteroinferior portal was simulated with Kirschner wires (K-w) drilled orthogonally at the 5 o'clock position in 13 fresh frozen human cadaveric shoulders. The neighboring neurovascular structures were identified through an anteroinferior window made in the inferior glenohumeral ligament. Their relations to the K-w and surrounding structures were recorded in both positions. Results: The median distance from the musculocutaneous nerve to the K-w was shorter in the lateral decubitus position than in the beach chair position (13.16 mm v 20.49 mm, P =.011). The cephalic vein was closer to the portal in the beach-chair position than in the lateral decubitus position (median 8.48 mm v 9.93 mm, P =.039). The axillary nerve was closer to the K-w in the lateral decubitus position than in the beach-chair position (median 21.15 turn v 25.54 mm, P =.03). No differences in the distances from the K-w to the subscapular and anterior circumflex arteries were found when comparing both positions. The mean percentage of subscapular muscle height from its superior border to the K-w was 53.03%. Conclusions: This study showed the risk of injury establishing a transubscapular portal in either position. The musculocutaneous nerve and the cephalic vein are the most prone to injury. In general, the beach-chair position proved to be safer. Clinical Relevance: Inserting anchor devices orthogonally would permit stronger fixation but presents the risk of damaging neurovascular structures. This study focused on showing the neurovascular risk of performing full orthogonal insertion. Considering the good results reported with the usual superior-anterior portals, we do not recommend performing a transubscapular portal in routine shoulder arthroscopy.