[DESIGN AND BIOMECHANICAL STUDY OF TRANSARTICULAR CUBOID BONE PLATE].

Objective: To design a new type of transarticular cuboid bone plate by measuring and collecting the anatomic data of the articular surface around cuboid, and to carry out comparative biomechanical study.

Methods: The angle α (between the fifth metatarsocuboid joint and the fifth metatarsal bone) and the angle β (between the fifth metatarsocuboid joint and the calcaneocuboid joint) were measured in 100 adults on medial oblique X-ray film and 30 adult foot specimens. Based on literature data, the transarticular cuboid bone plate was designed with an angle α of 70° and an angle β of 30°. Six adult cadaver feet were chosen and were transected approximately 15 cm proximal to the ankle. Five strain gauges were placed at the calcaneus, cuboid, and the fourth and fifth metatarsal bones. The vertical pressure was loaded on the foot at 0-600 N, the strain value was measured. Then the cuboid fracture model was established and 600 N load was given on foot to measure the strain value and compare with the strain value before fracture. The specimens were randomly divided into groups A and B (=3). Fracture was fixed with transarticular cuboid bone plate and 9 screws in group A and with double plate and 8 screws in group B, then the 600 N load was given to measure the strain value and vertical displacement of the fracture fragments.

Results: After loads of 0-600 N on the foot, the strain value of the 5 points showed an increased trend. No significant difference was found in the strain value between pre- and post-fracture at a, d, and e points >0.05), but it was significantly larger at post-fracture than pre-fracture at b and c points (<0.05). After fracture fixation, no significant difference was shown in the strain value at 5 points between groups A and B when loads of 0-600 N was given >0.05). The experimental data showed that the strain value change mainly focused on the fracture site under the same load, so the strain value after fracture fixation was similar to that before fracture at b and c points >0.05). The vertical displacement values of medial and lateral fracture fragments in group A[(0.804±0.011) mm and (0.672±0.036) mm] were significantly less than those in group B[(1.126±0.083) mm and (1.007±1.103) mm] (=-6.711, =0.003; =-5.307, =0.006).

Conclusions: Through biomechanical study, a new type of transarticular cuboid bone plate has better fixation effect.