Thumb carpometacarpal ligaments inside and out: a comparative study of arthroscopic and gross anatomy from the robert a. Chase hand and upper limb center at stanford university.

Purpose We propose to identify and correlate arthroscopic internal ligaments with external ligaments, providing an accurate roadmap for arthroscopic ligament and joint anatomy. Ligamentous laxity is considered an important risk factor in developing the common basilar arthritis of the thumb. Controversy exists as to the precise ligamentous anatomy of the thumb carpometacarpal (CMC) joint (CMC-I); description of the internal arthroscopic anatomy is limited. Methods We performed CMC-I joint arthroscopy using the 1-Ulnar (1U) and thenar portals in five cadavers, seeking to identify the following seven ligaments arthroscopically: the superficial anterior oblique ligament (sAOL), deep anterior oblique ligament (dAOL), ulnar collateral ligament (UCL), dorsal trapeziometacarpal ligament (DTM-1), posterior oblique ligament (POL), dorsal central ligament (DCL), and dorsal radial ligament (DRL). After grading articular changes of the trapezium, we passed Kirschner wires (K-wires) (0.028) outside-in to mark the arthroscopic insertion of each ligament on the trapezium. Gross dissection was performed to confirm the wire placement; the anatomic identity and position of joint stabilizing ligaments, and the location of frequently used portals. Results The volar ligaments-the sAOL, dAOL, and UCL-were highly variable in their arthroscopic appearance and precise location. The sAOL is a thin veil of membranous tissue that variably drapes across the anterior joint capsule. The reported dAOL and UCL, in our study, correlated to a thickened portion of this veil around the volar beak and was not consistently identified with gross dissection. In contrast, the arthroscopic appearance and location of the dorsal ligaments-DTM-I, POL, DCL, and DRL-were consistent in all specimens. Conclusion Our study further defines and correlates the arthroscopic and external ligamentous anatomy of the CMC-I joint.