Study On Mechanical Properties And The Standardized Surgical Procedure Of SCAP-FN For Unstable Femoral Neck Fracture

BackgroundUnstable femoral neck fracture is difficult for surgeons and has a high complication rate.The best treatment for unstable femoral neck fracture remains unclear.In the previous study,we designed the slide compression anatomic plate-femoral neck(SCAP-FN).Although it had advantage in the mechanical properties compared to the existing internal fixation,there were still problems such as inconvenient in operation and inward movement of screws.Therefore,it needs to be improved.Objective(1)To improve the design of SCAP-FN and its supporting equipment;(2)To compare the SCAP-FN,dynamic Hip screw(DHS)fixation combined with derotational screw(DS)fixation and three cannulated compression screws(CCS)fixation in mechanical properties;(3)To establish a standardized surgical procedure for SCAP-FN,and then to assess its advantages.Methods(1)According to the previous mechanical study,the design of SCAP-FN was improved with the help of the anatomical parameters and biomechanical characteristics of the proximal femur.We also designed its supporting equipment.(2)The finite element analysis was used to compare the change in displacement of the femur-internal fixation and the rotation angle between SCAP-FN,DHS+DS,and CCS for the treatment of unstable femoral neck fracture.(3)45 fourth generation Sawbones were used to establish unstable femoral neck fracture models.The biomechanical strength between SCAP-FN,DHS+DS and CCS was evaluated by static compression test,cyclic pressure test,and torsion test.(4)Through the Sawbones bone and cadaver experiments,the standardized surgical procedure for the treatment of femoral neck fractures with SCAP-FN was initially explored,and the internal fixation installation time and fluoroscope frequency of SCAP-FN were compared with DHS+DS and CCS.Results(1)The improved SCAP-FN is mainly consisted of four parts:?)one proximal femoral anatomical plate;?)two distal cortical locking screws;?)three lag screws that slide inside the sleeve;?)three sleeves that are locked to the proximal plate and the tail cap of the sleeve.(2)The finite element analysis showed that the maximum displacement of the femur and internal fixation were SCAP-FN<DHS+DS<CCS;so was the result of the change in the rotation angle.(3)In the static pressurization experiment,SCAP-FN had the strongest vertical stiffness and 5 mm failure load.In the cyclic pressurization experiment,after 30000 times of cylic louding,the cyclic louding were 70N-700N cyclic loading,100N-1000N cyclic loading and 140N-1400N cyclic loading,the SCAP-FN had the lowest change of displacement,so was the in the toal displacement.In the torsion test,the torsional stiffness and the maximum torque:SCAP-FN>DHS+DS>CCS;the torsion angle corresponding to the maximum torque:SCAP-FN<DHS+DS<CCS(4)Based on the experiment of the fresh frozen bodies,a surgical standardization process of SCAP-FN was established.SCAP-FN compared with DHS+DS and CCS,the average time required for internal fixation installation time was DHS+DS>SCAP-FN>CCS;the average frequency of fluoroscope was DHS+DS>CCS>SCAP-FN.ConclusionsCompared to the DHS+DS and CCS,SCAP-FN had better mechanical stability.Besides,we established the standardized surgical procedure of SCAP-FN,which could reduce the operation time and the X-ray exposure time of patients and surgeons.It is the foundation for SCAP-FN's future clinical application.Although the clinical application needs to be verified in future,this study may provide a new strategy for the treatment of the femoral neck fracture.