Trans-4 Portal as a New Portal for Accessing the Lunate in Wrist Arthroscopy: a Cadaveric Study

BACKGROUND: Evolving wrist arthroscopy requires creating new portals, and creating portals reciprocally leads to increased indications for arthroscopic wrist procedures. To facilitate access to the lunate bone and fossa for new arthroscopic procedures, a new portal was used. This is a cadaveric study of this portal. OBJECTIVES: In this cadaveric study, we evaluated a portal in wrist arthroscopy for procedures involving the lunate bone and lunate fossa. MATERIALS AND METHODS: Seventeen wrists from 10 fresh cadavers were included in this study. After diagnostic arthroscopy, a portal (Trans-4) was made through the fourth extensor compartment, exactly along the lunate’s long axis under direct visualization from the 3-4 portal. Strand retractors were used to protect the extensor tendons and posterior capsule. Lunate bone core decompression and osteoscopy were done through the portal. At the end of the procedure, the position of the decompression hole in the lunate and any possible injury to the extensor tendons, distal radius cartilage, lunate cartilage, and perilunate ligaments were investigated. RESULTS: Lunate bone decompression was performed successfully in all cases using the trans-4 portal. In 15 wrists, the lunate hole was located in the middle third. In the other two wrists, it was located slightly radial in one case and slightly on the ulnar side in the other case. There was no cortical penetration during decompression, and no extensor tendon, superficial nerve branches, or peri-lunate ligament injuries were observed. CONCLUSIONS: The trans-4 portal could be a safe working portal in wrist arthroscopy that enables access to the lunate bone and lunate fossa.