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Trapeziometacarpal and scaphotrapezial arthroscopy portals
Trapeziometacarpal joint portals
Standard portals
Menon initially presented his work on arthroscopy of the trapeziometacarpal joint (TMJ) as a meeting exhibit in 1994. He then published his experience with the arthroscopic management of trapeziometacarpal arthritis in 1996. He described two working portals: a volar portal just radial to the abductor pollicis longus (APL) tendon and a dorsal portal that is just ulnar to the APL along the line of the joint. Berger independently developed his technique for arthroscopic evaluation of the first carpometacarpal joint, which he first presented as an instructional course in 1995. He then published his clinical work in 1997. He named the volar radial portal the 1-R portal and the dorsal 
ulnar portal the 1-U portal ( ). He defined the term dorsal as being in the plane of the thumbnail and volar in the plane of the distal pulp. The terms radial and ulnar referred to the thumb when its nail is parallel to the fingernails with the thumb supinated and radially abducted. He noted that the plane of the 1-R portal passes through the nonligamentous capsule just lateral to the anterior oblique ligament (AOL). This portal is preferred for viewing the dorsoradial ligament (DRL), posterior oblique ligament (POL), and the ulnar collateral ligament (UCL). The plane of the 1-U portal, which is just posterior and ulnar to the extensor pollicis brevis (EPB), passes between the DRL and POL. This portal provides views of the AOL and UCL. Both portals are along the radial border of the thumb, which makes it difficult to assess the lateral side of the joint. There is no true internervous plane because branches of the superficial radial nerve surround the field and are at risk for injury with improper technique. The radial artery courses immediately posterior and ulnar to the arthroscopic field.
Modified radial portal
Orellana and Chow described a modified radial portal (RP) for improving the radial view of the TMJ. The RP is located just distal to the oblique ridge of the trapezium following a line along the radial border of the flexor carpi radialis (FCR) tendon rather than the APL. In an anatomic study of six cadaver arms, the superficial radial nerve (SRN) was located a mean of 6.3 mm (4–8 mm) from the 1-U portal and 7.8 mm (4–12 mm) from the RP. The radial artery passed within 2.7 mm (2–3.5 mm) of the 1-U portal and within 10 to 15 mm from the RP. To establish the RP, the scope is placed in the 1-U portal. The light source is pointed to the RP, which lies just radial to the AOL. A 22-gauge needle is inserted just distal to the ridge of the trapezium. The skin is incised, followed by blunt dissection through the capsule and insertion of the trocar and cannula, and then the arthroscope.
Thenar portal
A thenar portal was subsequently described by Walsh et al. This portal is placed by illuminating the thenar eminence with the arthroscope in the 1-U portal, and then inserting an 18-gauge needle through the bulk of the thenar muscles at the level of the TMJ, approximately 90 degrees from the 1-U portal. This portal did not appear to violate the important deep AOL, which is the major restraint against thumb metacarpal dorsal subluxation. They measured the distances of the surrounding neurovascular structures to three portals in a cadaver study of seven limbs. The SRN typically has a major volar branch (SR1) and a major dorsal branch that subdivides into a volar (SR2) branch and dorsal (SR3) branch. SR1 generally parallels the first extensor compartment whereas SR2 crosses the first web space. The mean distance from SR2 was 11.6 ± 1.0 mm for the 1-U portal, 25.7 ± 1.2 mm for the 1-R portal, and 33.7 ± 1.68 mm for the thenar portal. The mean distance from SR3 was 12.9 ± 1.1 mm for the 1-U portal, 7.4 ± 1.3 mm for the 1-R portal, and 19.07 ± 1.17 mm for the thenar portal. The mean distance from the radial artery was 13.3 ± 1.1 mm for the 1-U portal, 20.7 ± 0.9 mm for the 1-R portal, and 29.4 ± 1.15 mm for the thenar portal. The motor branch of the median nerve was an average of 23.0 ± 1.6 mm from the thenar portal. No published clinical series exist on the use of these two accessory portals as of yet.
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