Selection Of Internal Fixators And Finite Element Analysis For Unstable Intertrochanteric Fractures With Coronal Shear

Objective:With social development and increase in the aging population,the incidence of hip fracture has been kept increasing recently.Although various internal fixation techniques have been developed to sustain intertrochanteric fracture,the complications barely diminished.In 1949,Boyd classification emphasized the potential coronal fracture,which has not been regarded recently.Proximal femoral locking compression plate(PFLCP),a new and improved internal fixator for intertrochanteric fractures,was designed especially for osteoporotic patients.Outcomes of PFLCP and extra anterior plate to treat intertrochanteric fracture with coronal plane shear were discussed to provide evidence and choice for clinical treatment.Methods:(1)CT image of normal femur and intertrochanteric fracture with coronal plane shear was obtained from department of medical imaging,Shandong provincial hospital.The normal adult femur CT data was selected,and software such as Mimics,SolidWorks and Abaqus was used in the finite element analysis.The hip joint loads of 300 N,600 N,1200 N and 1800 N were applied to both group of finite element models as well as constrains to cover the daily activities,and the stress distribution and value and the displacement on the fracture plane of each model were observed to compare the different outcomes of two internal fixation systems.2)Medical record and image from the hospital and follow-up data were used to analyze the efficacy of this treatment retrospectively.Statistical comparison on surgical bleeding,time,surgical incision size,postoperative full weight bearing time of affected limb,bedridden time,length of hospital stays,hip function,and postoperative complication were operated.The patients were followed up 1 months,3 months,9 months and 1 year after surgery to estimate hip function.And there was statistically significant(P<0.05)using SPSS software to analysis.Result:92 cases of intertrochanteric fracture were collected and 14 were recognized as coronal plane shear and involved in the research.Seven of the 14 were classified as AO A2.2,while other 7 were A2.3.Follow-up period ranged 12 months to 3 years,16 months in average.Both intramedullary nailing and extramedullary fixation surgery could successfully complete.None of severe complication such as implant rupture,redisplacement or cutting out was observed during the follow-up.Compared to intramedullary nailing,extramedullary fixation presented shorter surgical time and larger incision.Nevertheless,there was no statistical difference in surgical bleeding,full weight bearing time,bedridden time,length of hospital stay,complication and Harris score.The results of finite element analysis showed that the maximum stress value of the femoral bone tissue,the maximum stress value of the internal fixator,and the maximum fracture displacement in the two internal fixation models all increased gradually along with the rising axial load.Bone stress in double plate group is higher than the PFNA model,and the internal fixator stress and the fracture displacement is slightly less than the PFNA model.The maximum displacement of the fracture under 1800N load in the two fixation methods was approximately 1mm.Conclusion:For intertrochanteric fracture with coronal plane shear,both intramedullary fixation and extramedullary fixation can achieve the effect of internal fixation.However,neither of the two internal fixation methods can meet the needs of patients with early weight-bearing walking.Most of the postoperative bedridden time were over 3 months.Complications such as postoperative pain and reduced joint range of motion were more common in both groups than normal intertrochanteric fractures,indicating that the current treatment methods are not good enough to meet the treatment needs of this type of fracture,and there is much for improvement.Finite element analysis proves that both intramedullary fixation and double plate fixation can provide effective fixation and have better control of fracture displacement.The maximum stress of the internal fixation is similar,but the internal fixation could fail under such stress.Therefore,patients suffered from this type of fracture must stay in bed and avoid weight-bearing after surgery.The results are consistent with the case analysis.In terms of practical application,due to the particularity of coronal splitting,some operational difficulties in the process of intramedullary nailing may be magnified,which requires accurate technique of the surgeon.Our research proves that there is little significant difference between the treatment of coronal split femoral intertrochanteric fractures with double plates and intramedullary nails.Due to the difficulty during placing intramedullary nails,unskilled operator,or economic problem or inaccessibility,intramedullary nails may not be the best for all cases,and double plate treatment can be an effective alternative.