Biomechanical study of novel minimally invasive dynamic hip plate for femoral subtrochanteric fractures

Abstract

Objective To perform a mechanical test of fresh cadaver specimens and compare the biomechanical properties of the novel minimal invasion dynamic hip plate (MIDHP) and the dynamic condylar screw (DCS) in treatment of subtrochanteric fractures of the femur.Methods All specimens were firstly used to simulate models of Seinsheimer type ⅡA subtrochanteric fractures of the femur,which were later divided into DCS group and MIDHP group.Based on experimental requirements,the femoral head and distal femur were embedded using seff-freezing type dental base acrylic resin powder.Torsion strength test was given in the first place,succeeded by compression strength test.Finally,destructive test was made to record the limit load.All experimental data were analyzed statistically.Results Torsion strength test showed that specimens of both groups were basically stable as the reverse was within 3°.Torque for specimens in DCS and MIDHP groups was (3.16 ± 0.13) N · m and (3.31 ± 0.27) N · m respectively as the reverse was 1.5°.Both torque and torsion stiffness had no statistical significance between the two groups,and the anti-rotation features of the two internal fixations were similar.Compression strength test showed that compression stiffness of specimens in DCS group was (532.27 ±61.02) N/mm and (581.98 ±77.56) N/mm in MIDHP group at a load of 800 N,with evidently higher compression displacement and stiffness in MIDHP group (P ＜ 0.05).Destructive test showed the maximum load of specimens in DCS and MIDHP groups was (2 994.38 ±244.81) N and (3 322.13 ± 141.21) N respectively,far higher in MIDHP group (P ＜ 0.01).Conclusions MIDHP is characterized by reasonable design,strong anti-rotation property and anti-compression property over DCS.In comparison with DCS,MIDHP has biomechanical advantage in treatment of femoral subtrochanteric fractures,for it can be performed minimally invasive and is worthy of further application. Key words: Femoral fractures ; Internal fixators ; Biomechanics