Metacarpophalangeal arthroscopy.

Although small joint arthroscopy has become commonplace over the past decade, relatively little attention has been paid to the investigation and clinical utility of metacarpophalangeal (MP) joint arthroscopy. The literature is scant in this area and consists of only a handful of case reports. In addition, the arthroscopic anatomy of the MP joint has not as yet been reported. Six cadaveric hands (24 joints) were rigorously studied in the laboratory using standard 2.5-mm small joint arthroscopic instrumentation and 5 lb of overhead traction. Radial and ulnar portals were used with care not to injure the extensor tendons. Arthroscopic anatomic landmarks include: (1) A consistent tripartite configuration of the main radial and ulnar collateral ligaments with characteristic changes in relative fiber orientation as the digit goes from extension to flexion, (2) nonvisualization of the accessory collateral ligament from inside the joint, (3) transitional amorphous capsular fibers connecting the collateral ligaments to the volar plate and dorsal capsule, (4) four synovial recesses (radial, ulnar, volar, and dorsal-proximal), (5) metacarpal head and proximal phalanx, (6) a consistent circumferential meniscal equivalent around the margin of the proximal phalanx articular surface, and (7) the sesamoid-metacarpal articulation in the thumb MPjoint. There are published case reports on the utility of MP joint arthroscopy for synovectomy in rheumatoid arthritis and hemachromatosis and realigning Stener lesions in gamekeepers' thumbs. The current clinical series reveals preliminary experience with the technique. MP joint arthroscopy was useful in relieving a locked MP joint from a loose osteochondral body and sagittal tear in the volar plate that enfolded into the joint surface. Intra-articular release of post-traumatic volar plate and dorsal capsular contracture were readily accomplished using this technique. Juxta-articular bone lesions such as osteoid osteomas can be removed with careful preoperative planning. Gamekeeper's thumbs that are unstable on stress radiographs can undergo arthroscopy with excellent sensitivity to determine the presence of a Stener lesion before an open or arthroscopic repair. The advantages of arthroscopic versus open techniques are similar to those experienced in larger joints. With time, more indications will emerge.