Biomechanical study of a modified application of Ilizarov external mini-fixator for metacarpal neck fractures: a comparative analysis.

Background: Metacarpal neck fractures are common and there are numerous surgical methods available, but each has certain disadvantages and limitations. We modified the conventional Ilizarov external mini-fixator and this study is designed to compare the biomechanical stability of a modified Ilizarov external mini-fixator with conventional fixation methods for metacarpal neck fractures and to provide a basis for its clinical application.

Methods: Forty fresh porcine metacarpal specimens were used to create metacarpal neck fracture models. The specimens were randomly assigned to four fixation groups (n = 10) as follows: (1) modified Ilizarov external mini-fixator (IEF), (2) retrograde crossed Kirschner wires (KW), (3) antegrade intramedullary Kirschner wires (IK), and (4) locking plate fixation (LP). In the IEF group, the modified design involved crossing two Kirschner wires (K-wires) through the fracture line, with their tails bent twice and connected to the external fixator frame. Biomechanical testing was performed using a modified three-point bending test. Maximum fracture force and bending stiffness were calculated from the force-displacement curves. Kruskal-Wallis test was used to compare statistical differences in maximum fracture force and stiffness among the groups, followed by post hoc pairwise comparisons adjusted with Bonferroni corrections.

Results: The median maximum fracture force values (± interquartile range, IQR) for each group were as follows: IEF 160.3 ± 55.6 N, LP 173.5 ± 42.6 N, KW 91.1 ± 23.1 N, and IK 79.8 ± 37.8 N. The corresponding stiffness values were as follows: IEF 29.5 ± 10.4 N/mm, LP 32.9 ± 10.4 N/mm, KW 17.2 ± 11.3 N/mm, and IK 18.2 ± 13.7 N/mm. The IEF group demonstrated significantly higher maximum fracture force and stiffness than the KW and IK groups; however, no statistically significant differences were observed in the IEF group compared with the LP group.

Conclusion: The modified Ilizarov external mini-fixator provided significantly greater biomechanical stability for metacarpal neck fractures than retrograde crossed K-wires and antegrade intramedullary K-wires, achieving comparable performance to the locking plate system. This modified design combines the simplicity and minimally invasive advantages of K-wire fixation with enhanced stability, potentially facilitating early joint mobilization and minimizing the risk of complication.