Proximal Phalanx Intramedullary Fixation Configurations: A Comparative Biomechanical Cadaveric Study

Threaded intramedullary nails offer a fixation option for proximal phalanx fractures with the advantage of immediate mobilization, avoiding secondary hardware removal, and decreased complications associated with exposed pins. There are currently limited data comparing the strength of intramedullary devices across various configurations with the traditional fixation method of Kirschner wires (K-wires). This study compared the biomechanical strength of intramedullary nail fixation (INF) in an "I," "Y," or "X" configuration or 2 Kirschner wires in an "X" configuration for transverse proximal phalanx fractures.

Forty cadaveric proximal phalanges with simulated transverse fractures were randomized to 1 of 4 fixation groups: INF in an "I," "Y," or "X" configuration or 2 K-wires in an "X" configuration. The specimens were subjected to apex dorsal 3-point bending to failure using servohydraulic testing. Peak load to failure and stiffness were recorded. Analysis of variance was used to compare means between groups.

No statistically significant differences in mean peak load to failure were detected between groups. Stiffness differed among groups, with the INF "X" configuration producing the stiffest construct (mean stiffness, 210 N/mm), significantly stiffer than all other groups. The second stiffest construct was the INF "Y" configuration (150.9 N/mm), which was significantly higher than both the INF "I" construct (107.7 N/mm) and the K-wire construct (91.8 N/mm). There was no significant difference between the INF "I" construct and the K-wire construct.

Threaded INF in "X" or "Y" configurations offers superior stiffness compared to K-wire and "I" INF for proximal phalanx fractures.