Description of Specific Portals for Extensor Carpi Ulnaris Tenoscopy: Anatomical Safety Study.

Abstract

Purpose: The objective of this study was to describe potential working portals positioned directly over the extensor carpi ulnaris (ECU) tendon and assess their safety in relation to the dorsal branch of the ulnar nerve (DBUN).

Methods: A descriptive anatomical study was conducted on 15 fresh human cadaver upper limbs. Five distinct portals over the ECU were examined, and the shortest distances from these portals to the DBUN were measured. Additionally, three distances from two portals and the ulnar styloid to the point where the DBUN crosses the ECU tendon were assessed.

Results: The measurements of the distance to the DBUN from the portal at the level of the ulnocarpal joint (UCJ) from the proximal ECU (PECU) portal and from the portals located two and three centimeters proximal to the PECU indicate that no distances fell within the high-risk category (less than 3.5 mm). Measuring from the portal at the level of the UCJ to the DBUN, only one specimen fell within the medium-risk range (3.5-4.5 mm). However, in the rest of the previously described portals, all measurements corresponded to a low-risk range (more than 4.5 mm). The measurements from the distal ECU (DECU) portal to the DBUN revealed that 4 of 15 specimens had a distance less than 3.5 mm (high-risk range), whereas 2 of 15 fell within the medium-risk range.

Conclusions: Proximal portals are safer and present a lower risk of nerve injury. Three distinct zones have been defined along the ECU based on their safety characteristics. The "green zone" is the safest area, situated 1 cm proximal to the 6R portal. The "yellow zone" encompasses the area extending from 1 cm proximal to 0.5 cm distal to the 6R portal. Finally, the "red zone" is located 0.5 cm distal to the 6R portal.

Clinical relevance: For arthroscopic procedures involving the ECU, additional portals may be necessary. This anatomical study may be valuable in developing and implementing surgical techniques tailored for ECU pathology.