Effect of a figure-of-eight cerclage wire with two Kirschner wires on fixation strength for transverse metacarpal shaft fractures: an in vitro study with artificial bone

Abstract

Background: Metacarpal shaft fractures are a common type of hand fracture. Despite providing strong fixation strength, plate fixation has numerous shortcomings. Concerning internal fixation with Kirschner wires (K-wires), although this approach is frequently used to treat metacarpal shaft fractures, the lack of functional stability may result in fixation failure.

Objective: To evaluate the effect of figure-of-eight cerclage wire on fixation for transverse metacarpal shaft fractures using two K-wires.

Materials and methods: We used a saw blade to create transverse metacarpal shaft fractures in 14 fourth-generation artificial third metacarpal bones (Sawbones, Vashon, WA, USA), which were assigned to groups undergoing fixation with two K-wires (KP) or with two K-wires and figure-of-eight cerclage wire (KP&F8). All specimens were subjected to material testing, specifically cantilever bending tests. The maximum fracture force and stiffness of the two fixation types were determined on the basis of the force-displacement data. The Mann-Whitney U test was used to compare between-group differences in maximum fracture force and stiffness.

Results: The maximum fracture force of the KP group (median ± interquartile range = 97.30 ± 29.70 N) was significantly lower than that of the KP&F8 group (153.2 ± 69.50 N, p < 0.05; Figure 5a), with the median of the KP&F8 group exceeding that of the KP group by 57.5%. Similarly, stiffness was significantly lower in the KP group (18.14 ± 9.84 N/mm) than in the KP&F8 group (38.25 ± 23.49 N/mm; p < 0.05; Figure 5b), with the median of the KP&F8 group exceeding that of the KP group by 110.9%.

Conclusion: The incorporation of a figure-of-eight cerclage wire increased the maximum fracture force and stiffness by 57.5 and 110.9%, respectively, compared with those achieved in standard two K-wire fixation. Therefore, hand surgeons are advised to consider the proposed approach to increase fixation strength.

Keywords: Figure-of-eight cerclage wire; K-wire; Metacarpal shaft fracture.

Fig. 1

Artificial metacarpal bones with transverse shaft fractures. a Lateral view. b Cross-sectional view

Fig. 2

Artificial metacarpal bones with transverse shaft fracture subjected to fixation. a Two K-wire fixation. b Two K-wire fixation with a figure-of-eight cerclage wire. The top and bottom images present the lateral and dorsal views, respectively

Fig. 3

Radiographs of the specimens. a Two K-wire fixation. b Two K-wire fixation with a figure-of-eight cerclage wire. The top and bottom images present the lateral and dorsal views, respectively

Fig. 4

Experimental setup for the cantilever bending tests

Fig. 5

Box plot showing the a maximum fracture force and b stiffness of the specimens. *p < 0.05