Pin Insertion to the Interosseous Hood Minimize the Finger Motion Restriction for the Proximal Phalangeal...

Background: The purpose of this study was to identify the optimal pin insertion point to minimize finger motion restriction for proximal phalangeal fixation in cadaver models. Methods: We used 16 fingers from three fresh-frozen cadavers (age, 82-86 years). Each finger was dissected at the level of the carpometacarpal joint and fixated to a custom-built range of motion (ROM)-measuring apparatus after skin removal. The pin was inserted into the bone through four gliding soft tissues: the interosseous hood, dorsal capsule, lateral band, and sagittal band. Then, each tendon was pulled by a prescribed weight in three finger positions (flexion, extension, and intrinsic plus position). Changes in the metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) angles were measured before and after pinning. We compared the differences between the insertion points using the Tukey-Kramer post hoc test. Results: Placement of pins into the sagittal band significantly restricted MCP joint flexion, while placement into the dorsal capsule and lateral band significantly restricted PIP joint flexion. Only placement into the interosseous hood showed no significant difference in joint angles between the three finger positions compared to pre-pin insertion. There were no significant effects on MCP, PIP, and DIP joint extension. Conclusions: The ROM of the MCP joint was obstructed due to pinning in most areas of insertion. However, pin insertion to the interosseous hood did not obstruct the finger flexion ROM compared to that of other gliding soft tissues; therefore, we believe that the interosseous hood may be a suitable pin insertion point for proximal phalangeal fixation.