Finite Element Analysis Of Single And Double Plates In The Treatment Of Senile Osteoporotic Distal Femoral Type A3 Fractures

Background:For elderly osteoporotic distal femoral type A3 fractures,functional reduction,strong and stable internal fixation,and secondary fracture healing are the main treatment methods.Since the fracture of thin cortex and sparse trabecular structure is usually accompanied by metaphyseal bone compression or bone defect,the simple application of lateral locking plate or LISS plate in the treatment of senile osteoporotic distal femoral type A3 fracture has the risk of insufficient bone holding force to internal fixation,insufficient stability of internal fixation device,and longterm stress concentration on lateral plate leading to fatigue fracture of plate.Therefore,it is clinically proposed to combine the medial plate to improve the stability of the internal fixation device.The medial plate solves the instability of the eccentric fixation of the single plate by reconstructing the continuity of the medial bone.At the same time,the combined fixation of the medial and lateral double plates can evenly disperse the stress to both sides of the femur to reduce stress concentration and improve the fixation effect.At present,most of the studies on the treatment of senile osteoporotic distal femoral A3 fractures with single and double plates are retrospective analysis of clinical cases,and there is a lack of single and double plate control studies and biomechanical studies.Objective:Through the finite element analysis method,the biomechanical differences between single and double plate in the treatment of senile osteoporotic distal femoral fractures were compared,hoping to provide some reference and help for clinical work.Methods:One elderly male patient with osteoporosis was selected.According to the CT scan data of femur,Mimics 21.0,Geomagic Studio 2014,Sloidworks2021 and Ansys2021 software were used to establish the A3 type fracture model of distal femur in elderly patients with osteoporosis.Three finite element models were obtained by assembling lateral locking plate,lateral locking plate + medial reconstruction plate and lateral locking plate + medial proximal tibial plate.Axial load,torsional load and three-point bending load were applied to the three models.The maximum equivalent stress and stress cloud diagram of the internal fixation device and femur in the three models and the maximum displacement of the fracture end were obtained,and the results were discussed and analyzed.Results:1.Under the axial load,the stress of the femur and the stress of the internal fixation device in the lateral locking plate group showed stress concentration in the fracture end area,and the stress of the femur,the stress of the internal fixation device and the displacement of the fracture end exceeded the set standard under the load of800 N and 1000 N,and there was a risk of plate fracture and fracture nonunion.In the double plate system,the maximum equivalent stress of the femur and the internal fixation device and the displacement of the fracture end were within a reasonable range,and there was no significant difference between the two groups.2.Under torsional load,the maximum equivalent stress and fracture displacement of femur and internal fixation device in the lateral locking plate group were greater than those in the double plate system,the maximum equivalent stress and fracture displacement of femur in the lateral locking plate + medial reconstruction plate group were the smallest in the double plate system,and the maximum equivalent stress of internal fixation device in the lateral locking plate +medial proximal tibial lateral plate group was the smallest.3.Under three-point bending loading,the maximum equivalent stress and fracture displacement of the femoral and internal fixation devices in the lateral locking plate group were greater than those in the double plate system,and the maximum equivalent stress and fracture displacement of the femoral and internal fixation devices in the lateral locking plate + medial proximal tibial lateral plate group were slightly smaller than those in the lateral locking plate group + medial reconstruction plate group.Conclusion:In the treatment of elderly osteoporotic distal femoral type A3 fractures with lateral locking plate alone,there is a risk of stress absorption at the fracture end,failure of internal fixation device,and obvious displacement of the fracture end,which may lead to surgical failure.The medial plate in the double plate system can restore the medial support and continuity,strengthen the internal fixation and the stability of the fracture end,which is conducive to fracture healing.3.In the double plate system,there was no significant difference in the experimental results between the lateral locking plate + medial reconstruction plate group and the lateral locking plate + medial proximal tibial lateral plate group under axial,torsional and three-point bending loading.