Anatomical Basis for Arthroscopy of the Proximal Interphalangeal Joints.

Background: Arthroscopy is a widely used minimally invasive technique. Nevertheless, no report describes the arthroscopic anatomy of the proximal interphalangeal (PIP) joint for portal creation. To facilitate arthroscopy, this study elucidated the anatomy of the lateral bands of the extensor mechanism and collateral ligaments of PIP joints.

Methods: A total of 39 fingers from the right hands of 10 cadavers (4 males, 6 females) were evaluated in this study. We defined the extension line from the proximal interphalangeal volar crease as the C-line. We also defined an imaginary line along the distal edge of the proximal phalanx, which is parallel to the C-line, as the J-line. The distance between J-line and C-line was measured. On the C-line and J-line, we measured the following: from the dorsal skin to the lateral edge of the lateral band (LB), the dorsal edge of the collateral ligament (CL) and from the lateral band and the collateral ligament (D), the width of the finger (W). The finger half-width (M) was measured on the J-line. Comparison between the digits and comparison between radial and ulnar distance were measured and statistical analysis was performed.

Results: All PIP joint spaces were distal from the C-line, except for one ring finger. The average distances between the J-line and C-line were 1.8-3.2 mm. On the C-line, only 11 cases (14.1%) showed an interval between the lateral bands and the collateral ligaments, but, on the J-line 72, cases (92.3%) had such an interval. The interval was located 1.6-2.9 mm in a dorsal direction from the midlateral on the J-line.

Conclusions: Portal creation at the J-line is safer than at the C-line. This study revealed that safe portals for arthroscopy of the PIP joint are 2 mm dorsal to the midlateral line of the finger on the J-line.