RESUMEN
Objective To explore the stability of unilateral external fixator for tibial fracture in its middle in condition of different distribution and number of screws. Methods The experiment model was made when eighteen human corpse tibial transverse fractures had been fixated with unilateral external fixation, which were divided into six groups. In each group, resistance fragments were adhered to be close to the transverse tibial fracture and near the screw-bone interface(SBI), including three screw distribution models, which were well distributed, close to and far off the fracture site distribution. Each model had also been accomplished according to the conditions of four and six screws before compression load of the same magnitude, the same direction and the same loading position. This method was used to observed the values of strain of SBI and axial displacement at the fracture site at grade load. Results ① Under compression condition, the models displacements and the force at Y-axial were the smallest when screw distribution was even in four or six screws and much better than those of four screws. ② The stability at the condition of six screws was stronger than that of four screws. Conclusion The even distribution of four screws is reasonable when tibial fractures are treated with unilateral external fixation, and six screws can be choosen if conditions permit.