| Objective: To investigate the biomechanical stability of the percutaneous minimally invasive screw rod system for fixing intertrochanteric femoral fractures by comparing with proximal femoral nail antirotation(PFNA)and proximal femoral locking compression plate(PFLCP).The biomechanical stability of the percutaneous minimally invasive screw rod system for fixation of intertrochanteric femoral fractures was investigated.Methods: Thirty Sybone simulated femoral standard experimental bones(left side)of the same size,length,material,diameter and side were selected and randomly divided into three groups.The proximal femoral nail antirotation(PFNA),proximal femoral locking compression plate(PFLCP)and percutaneous minimally invasive screw rod system were implanted according to the relevant standard surgical operation specifications.The internal fixation was removed,and each model group was then randomly divided into 2 subgroups(n=5),and intertrochanteric osteotomy was performed with a wire saw according to AO fracture typing to prepare A1.1 and A3.1 intertrochanteric femoral fracture models,A1.1 was divided into screw rod system group(A1.1),PFNA group(A1.1),and PFLP group(A1.1);A3.1 was divided into screw rod system group(A3.1),PFNA group(A3.1),and PFLP group(A3.1).The fracture model was repositioned and fixed,Simulating a human in a unipedal standing state,it was fixed on a microcomputer-controlled electronic universal testing machine,and axial compression test,torsion test and maximum axial compression damage test were performed on each fracture model respectively to generate displacement curves and calculate the corresponding axial compression stiffness and torsion stiffness,and record the maximum axial compression load and specimen damage.Results:(1)Biomechanical determination of A1.1 fracture model:(1)Axial compression test:When the load was 400 N and 600 N,there was no statistical significance in the axial displacement of the femoral head among the three groups(P > 0.05).When the load was800 N,1000N and 1200 N,the axial displacement of the femoral head in the PFNA group was the minimum,while that in the screw rod system system group was the maximum(P < 0.05).When the load was 400 N,600N,there was no significant difference in the axial compression stiffness of the femoral head in the three fixation groups(P > 0.05),and when the load was800 N,1000N and 1200 N,the axial compression stiffness of the PFNA group was greater than that of the PFLCP group and the screw rod system,and the difference was statistically significant(P < 0.05),and the axial compression stiffness of the PFLCP group was greater than that of the screw rod system group(P < 0.05);(2)Torsion test: under the same torsion angle,the torque of the three fixation methods was approximately the same(P > 0.05);under the same torsion angle,there was no significant difference in the torsional stiffness of the three fixation methods(P > 0.05);(3)Maximum axial compression failure test: the maximum loads of PFNA,PFLCP and screw rod system were 2870.00±45.28 N,2632.00±110.32 N and2068.00±44.38 N,respectively,and the difference was statistically significant(P < 0.05).(2)Biomechanical determination of A3.1 fracture model:(1)Axial compression test: When the load was 400 N,there was no statistical significance in axial displacement of femoral head among the three groups(P > 0.05).When the load was increased to 600 N,the axial displacement of femoral head in PFNA group was smaller than that in PFLCP group and screw rod system group(P < 0.05),and there was no significant difference between PFLCP group and screw rod system group(P > 0.05).When the load was 800 N,1000N and 1200 N,the axial displacement of femoral head in the screw rod system group increased significantly,and there was a significant difference between the PFNA group and PFLCP group(P < 0.05).The axial displacement of femoral head in the PFLCP group was significantly greater than that in the PFNA group(P < 0.05).When the load was 400 N,there were differences in axial compression stiffness between PFNA group,PFLCP group and screw rod system group(P <0.05),but there was no significant statistical significance in axial compression stiffness between PFLCP group and screw rod system group(P > 0.05).When the load was 800 N,1000N and 1200 N,The axial compression stiffness of PFNA group was significantly higher than that of PFLCP group and screw rod system group,and the difference was statistically significant(P < 0.05).The axial compression stiffness of PFLCP group was higher than that of screw rod system group(P < 0.05).(2)Torsion test: When the torsion Angle was 1° and 2°,the torque of PFLCP group was significantly greater than that of PFNA group and screw rod system group,and the difference was statistically significant(P < 0.05).There was no significant difference between the PFNA group and screw rod system group(P > 0.05).When the torsion Angle was 3°,4° and 5°,the torque of PFLCP group was the maximum.The torque of screw rod system group was the least,and there was significant difference among the three groups(P < 0.05).When the torsional angles were 1° and 2°,the torsional stiffness of PFLCP group was significantly different from that of PFNA group and screw rod system group(P < 0.05),but there was no statistical difference between PFNA group and screw rod system group(P > 0.05),when the torsional angle was 3°,4°,5°,the torsional stiffness of the PFLCP fixation method was the largest,the PFNA fixation method was the second largest,and the screw rod system fixation torsional stiffness was the smallest,and there was a significant difference between the torsional stiffness of the three fixation methods(P < 0.05).(3)The maximum axial compression failure test: the maximum loads of PFNA,PFLCP and screw rod system were 1776.00±43.93 N,1584.00±59.41 N and 1244.00±37.82 N,and there were statistical differences among the three groups(P < 0.05).Conclusion: For biomechanical stability,all three fixation methods could achieve good stability of A1.1 and A3.1 intertrochanteric fracture models;the results of this biomechanical test showed that the three fixation methods could meet the requirements of intertrochanical femoral fracture fixation in terms of resistance to axial compression and rotation,and had good mechanical stability.Although the screw rod system group did not have superiority in axial compression stiffness,torsional stiffness,and maximum axial load compared with the PFNA and PFLCP groups,it could also make the intertrochanical femoral fracture model obtain biomechanical strength,so the screw rod system has certain significance and value for maintaining stability in the treatment of intertrochanical femoral fractures. |
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