Treatment of intra-articular distal femur fracture by our slot-designed compression bolt combined with bilateral locking compression plates: a biomechanical analysis / 中华创伤骨科杂志

ABSTRACT

Objective:To evaluate the biomechanical stability of our slot-designed compression bolt (SCB) combined with bilateral locking compression plates (LCPs) in the treatment of intra-articular distal femur fracture.Methods:In 24 adult male knee specimens treated with formalin, the femoral bony part was preserved to establish standard models of intra-articular distal femur fracture (AO type 33-C1). According to the random number table, the fracture models were divided into 2 equal groups: an experimental group ( n=12) subjected to fixation with one SCB combined with bilateral LCPs with 10 locking screws and a control group ( n=12) subjected to fixation with bilateral LCPs with 12 locking screws. In each model, a vertical ballast test was conducted to record the maximum axial displacement of the system and a horizontal torsion test to calculate the torsional stiffness of the system. When the loading pressure was 0-1,000 N in the biomechanical machine, structural abnormalities were observed in the 2 groups of models and the system maximum axial displacement and system torsional stiffness were compared between the 2 groups. Results:When the vertical ballast pressure was 400 N, 600 N, 800 N and 1,000 N, the maximum axial displacement of the system was, respectively, (0.14±0.01) mm, (0.25±0.01) mm, (0.41±0.02) mm and (0.63 ± 0.02) mm in the experimental group, and (0.15 ± 0.01) mm, (0.26 ± 0.01) mm, (0.46 ± 0.03) mm, and (0.67 ± 0.04) mm in the control group. Compared with the control group, the average maximum axial displacement in the experimental group decreased significantly under the axial pressure of 600-1,000 N ( P<0.05). When the horizontal torsion reached 5°, the torsional stiffness was, respectively, (2.00±0.12) Nm/° and (2.02±0.07) Nm/° in the experimental group and the control group, showing no significant difference between the 2 groups ( P>0.05). Conclusions:In the treatment of intra-articular distal femur fracture, compared with simple bilateral LCPs, our SCB combined with bilateral LCPs demonstrate similar torsional stability but better axial biomechanical stability. As our SCB has advantages of bilateral compression and minimal invasion in operation, it may be a new option for the reduction and compression treatment of intra-articular fractures.