| Objective: A three-dimensional finite element model of simple external fixation technique and intramedullary nail combined with external fixation technique was constructed,through the CT scan data of large femoral bone defect and large tibial bone defect.The biomechanical characteristics of the model were calculated and analyzed.Combined with the comparison of the prognosis results of intramedullary nail combined with external fixation technique in the treatment of large tibial bone defect,the data support was provided for the subsequent optimization of clinical internal and external fixation plan for large tibial bone defect.Methods:(1)3D CT reconstruction was performed according to the data after CT scanning of large femoral and tibial bone defects.3D finite element model of intramedullary nail combined with external fixation was obtained by geometric model reversal,INTERNAL and external fixation 3D modeling,mesh model division,and finite element pre andpostprocessingg.The strength specificity and stability of the internal and external fixation 3d finite element models of large femoral and tibial bone defects were compared,and the biomechanical characteristics of the models were calculated and analyzed.(2)According to the inclusion and exclusion criteria,the clinical data of 30 patients with large femoral and tibial bone defects treated in our hospital from December 2017 to December 2021 were retrospectively analyzed.Patients treated with external fixator alone were included in the conventional group,and the patients treated with intramedullary nail combined with external fixator were included in the study group.The differences in the treatment efficacy indicators,knee joint function,ankle joint function,joint range of motion,pain degree,sleep quality and anxiety psychological score indicators were compared between the two groups.SPSS 21.0software was used to describe the measurement data meeting the normal distribution in the form of mean ± standard deviation( ± ),and the enumeration data were described in the form of frequency [n(%)].Fisher ’s exact test was used to compare enumeration data between the two groups,and independent sample t-test or Mann-Whitney U test was used to compare measurement data between the two groups.Differences were considered statistically significant at P < 0.05.Results:(1)The equivalent stress and torsional stiffness of the femoral and tibial intramedullary nail combined with external fixator groups under the axial loading of 700 N on the plateau were significantly higher than those of the intramedullary nail group,the external fixation group and the healthy group and the intramedullary nail group was the highest,and the differences were statistically significant(P < 0.05).Tibial torsional stiffness of the intramedullary nail + external fixator group was significantly higher than that of the intramedullary nail group,the external fixation group and the healthy group and the intramedullary nail group was the highest,and the differences were statistically significant(P < 0.05).(2)Compared with the control group,the femoral and tibial experiment groups had significantly lower bone lengthening length,mineralization time in the regeneration area,postoperative bone end cleaning and bone graft rate,external fixation index,intraoperative blood loss,broken end healing time,mechanical axial deviation,length of the affected limb,external fixation time,external fixator index,healing index and healing rate at the docking site significantly higher(P < 0.05).The range of motion of knee flexion,knee function score,AHS,Baird-Jackson,SF-36 and ADL scores of the two groups increased after surgery,and the range of motion of knee flexion,Lysholm knee function score,AKSS score,AHS score,Baird-Jackson,SF-36,ADL scores and excellent and good rate of postoperative outcome of the experiment group significantly higher than the control group(P < 0.05).The NRS,PSQI,VRS,and SAS scores of the two groups were decreased,and the NRS,PSQI,VRS,and SAS scores of the experiment group were lower then the control group(P < 0.05).The rate of complications in experiment group was significantly lower(P < 0.05).Conclusions:(1)Based on the Any Body Modeling System,a muscle tissue model is constructed and the biomechanical characteristics of using intramedullary nails combined with external fixator for femoral and tibial bone defects are analyzed.The combination of intramedullary nails and external fixation system can provide stable structural strength,effectively reducing stress concentration of fixation screws and transverse deviation of distraction bone segments.(2)The combination of intramedullary nails and external fixation system can provide a stable mechanical environment for distraction area,reducing the occurrence of axial deviation and soft tissue incarceration through the action of intramedullary nail guides.(3)Intramedullary nail fixation after distraction phase provides stable mechanical support for bone regeneration,which can remove the external fixator in the early mineralization phase,shorten the external fixation time,and reduce complications such as pin tract infection,angular deformities,adjacent joint stiffness,and psychological burden.(4)The combination of intramedullary nails and external fixation system is an practical method for the treatment of massive bone defects of lower limb,which can simultaneously correct limb shortening deformity. |
