BACKGROUND:The C1 type fracture of the distal radius is an intraarticular unstable fracture,which is difficult to treat.At present,there are few clinical studies about the comparison of the biomechanical differences of different internal fixation plates for distal radius fractures under different loading conditions,and there are still controversies in the selection of internal fixation plates.OBJECTIVE:To compare the biomechanical properties of different internal fixation plates for C1 type fractures of distal radius using a finite element analysis method.METHODS:The distal radius model of a healthy female volunteer was used,and the files were sequentially imported into Mimics 21.0,Geomagic Wrap 2017,and Solid Works 2021 for processing.The C1 type fracture of the distal radius was modeled.According to the plate data provided by the manufacturer,the volar oblique T-locking plate,volar fixed-angle anatomical plate,volar variable-angle locking plate and screws three-dimensional model were created and assembled with the fracture model.The material properties were given in ANSYS 19.0 to set up the relationship of interaction between the contact surfaces,and to define the loads and boundary conditions.Four load cases,including compression,dorsal flexion,palmar flexion and torsion,were applied to compare the biomechanical properties.RESULTS AND CONCLUSION:(1)In the three groups of internal fixation models,the overall displacement of the internal fixation model was mainly concentrated on the articular surface of the distal radius under four load conditions.The maximum displacement of the model under the dorsal,palmar and torsion load conditions was 2-6 times that of the displacement under the axial load,indicating that the internal fixation system was the most stable under the axial load condition.(2)The stress on the internal fixation was much greater than the stress on the bone fracture fragments.The stress of the internal fixation was mainly concentrated in the area that near to the fracture end of the bone plate,among which the stress distribution of the volar fixed-angle anatomical plate,volar variable-angle locking plate was relatively uniform,and the stress concentration of the oblique T-locking plate was the most obvious.(3)Under compressive and torsional loads,the stress of the fracture fragments was mainly concentrated in the area that around the screw holes.Under dorsal and palmar flexion,it gradually expanded from the distal end to the proximal radius.Under the same load condition,the stress of the fracture block in the oblique T-locking plate fixation state was the highest,and the peak stress of the fracture fragments in the volar variable-angle locking plate fixation system was the lowest.The difference between the peak stress of the bone fracture fragments in the fixed state of the volar fixed-angle anatomical plate and the volar variable-angle locking plate was only in the range of 0.2-6.0 MPa.(4)It is indicated that compared with the oblique T-locking plate and the volar fixed-angle anatomical plate,the volar variable-angle locking plate has more uniform stress distribution,less displacement of articular surface,and the best stability in the internal fixation in the C1 type fracture of the distal radius.

BACKGROUND:The types of acetabular double-column fractures are complex and common.At present,the traditional reconstructed bone plates are used to treat the double-column fractures,and the mismatch between them and the bone surface will increase the difficulty of surgery.Personalized bone plate can realize the adhesion of bone plate and bone surface,but the biomechanical comparison between personalized bone plate and traditional reconstructed bone plate in fixation of acetabular double column fracture is few,and the simulated posture is relatively simple.OBJECTIVE:Three-dimensional finite element method was used to analyze the biomechanical characteristics of different internal fixation methods of complex acetabular double-column fractures in various positions,providing the necessary biomechanical basis for clinical application.METHODS:The most representative two-column fracture model of complex acetabular fractures involving square area was established.A three-dimensional finite element model was established for the fixation of complex acetabular double-column fractures by four different internal fixation methods:special-shaped titanium plate fixation(group A),anterior and posterior column double titanium plate fixation(group B),anterior column reconstruction titanium plate+posterior column lag screw fixation(group C),and anterior column reconstruction titanium plate+subacetabular screw fixation(group D).Four kinds of complicated acetabular double-column fracture models with different internal fixation were simulated in the position of sitting,standing,affected side extension,affected side abduction,and affected side standing on one leg.The biomechanical properties of the four internal fixation methods were compared.RESULTS AND CONCLUSION:(1)The node displacement and mean displacement on fracture line were presented as group A＜group B＜group C＜group D in all postures.The displacement value in the one-leg standing position on the affected side was the largest compared with other postures,and the maximum displacement of the internal fixation system in group A was the smallest among the four models.There was no significant difference between the four groups in the standing position and the one-legged standing position(P＞0.05).In the position of sitting,affected side extension,and affected side abduction,there was no significant difference between group A and group B,group B and group C,and group C and group D(P＞0.05),but there was significant difference between group A and group C,group A and group D,and group B and group D(P＜0.05).(2)The maximum stress of each fracture block in group A was smaller than that in other groups,and the stress distribution of fracture block was more uniform.The stress of the internal fixator was mainly concentrated in the area near the fracture end of the bone plate.The stress distribution of the internal fixator was more uniform in groups A and B,while the stress concentration of the internal fixator in groups C and D was more obvious,and the maximum stress value of the internal fixator in group A decreased by 4.86％-54.61％compared with the other three groups.(3)In the affected side extension and abduction position,both groups A and B had a large stress shielding rate,and the maximum difference between the two groups was 5.67％.In the one-legged standing position on the affected side,the internal fixed stress shielding rate of group A was the highest,while that of group D was the lowest.(4)It is indicated that shaped personalized titanium plate fixation(group A)has better biomechanical stability than the other three groups of traditional reconstructed bone plate fixation.

BACKGROUND:The types of acetabular double-column fractures are complex and common.At present,the traditional reconstructed bone plates are used to treat the double-column fractures,and the mismatch between them and the bone surface will increase the difficulty of surgery.Personalized bone plate can realize the adhesion of bone plate and bone surface,but the biomechanical comparison between personalized bone plate and traditional reconstructed bone plate in fixation of acetabular double column fracture is few,and the simulated posture is relatively simple.OBJECTIVE:Three-dimensional finite element method was used to analyze the biomechanical characteristics of different internal fixation methods of complex acetabular double-column fractures in various positions,providing the necessary biomechanical basis for clinical application.METHODS:The most representative two-column fracture model of complex acetabular fractures involving square area was established.A three-dimensional finite element model was established for the fixation of complex acetabular double-column fractures by four different internal fixation methods:special-shaped titanium plate fixation(group A),anterior and posterior column double titanium plate fixation(group B),anterior column reconstruction titanium plate+posterior column lag screw fixation(group C),and anterior column reconstruction titanium plate+subacetabular screw fixation(group D).Four kinds of complicated acetabular double-column fracture models with different internal fixation were simulated in the position of sitting,standing,affected side extension,affected side abduction,and affected side standing on one leg.The biomechanical properties of the four internal fixation methods were compared.RESULTS AND CONCLUSION:(1)The node displacement and mean displacement on fracture line were presented as group A＜group B＜group C＜group D in all postures.The displacement value in the one-leg standing position on the affected side was the largest compared with other postures,and the maximum displacement of the internal fixation system in group A was the smallest among the four models.There was no significant difference between the four groups in the standing position and the one-legged standing position(P＞0.05).In the position of sitting,affected side extension,and affected side abduction,there was no significant difference between group A and group B,group B and group C,and group C and group D(P＞0.05),but there was significant difference between group A and group C,group A and group D,and group B and group D(P＜0.05).(2)The maximum stress of each fracture block in group A was smaller than that in other groups,and the stress distribution of fracture block was more uniform.The stress of the internal fixator was mainly concentrated in the area near the fracture end of the bone plate.The stress distribution of the internal fixator was more uniform in groups A and B,while the stress concentration of the internal fixator in groups C and D was more obvious,and the maximum stress value of the internal fixator in group A decreased by 4.86％-54.61％compared with the other three groups.(3)In the affected side extension and abduction position,both groups A and B had a large stress shielding rate,and the maximum difference between the two groups was 5.67％.In the one-legged standing position on the affected side,the internal fixed stress shielding rate of group A was the highest,while that of group D was the lowest.(4)It is indicated that shaped personalized titanium plate fixation(group A)has better biomechanical stability than the other three groups of traditional reconstructed bone plate fixation.

BACKGROUND:The C1 type fracture of the distal radius is an intraarticular unstable fracture,which is difficult to treat.At present,there are few clinical studies about the comparison of the biomechanical differences of different internal fixation plates for distal radius fractures under different loading conditions,and there are still controversies in the selection of internal fixation plates.OBJECTIVE:To compare the biomechanical properties of different internal fixation plates for C1 type fractures of distal radius using a finite element analysis method.METHODS:The distal radius model of a healthy female volunteer was used,and the files were sequentially imported into Mimics 21.0,Geomagic Wrap 2017,and Solid Works 2021 for processing.The C1 type fracture of the distal radius was modeled.According to the plate data provided by the manufacturer,the volar oblique T-locking plate,volar fixed-angle anatomical plate,volar variable-angle locking plate and screws three-dimensional model were created and assembled with the fracture model.The material properties were given in ANSYS 19.0 to set up the relationship of interaction between the contact surfaces,and to define the loads and boundary conditions.Four load cases,including compression,dorsal flexion,palmar flexion and torsion,were applied to compare the biomechanical properties.RESULTS AND CONCLUSION:(1)In the three groups of internal fixation models,the overall displacement of the internal fixation model was mainly concentrated on the articular surface of the distal radius under four load conditions.The maximum displacement of the model under the dorsal,palmar and torsion load conditions was 2-6 times that of the displacement under the axial load,indicating that the internal fixation system was the most stable under the axial load condition.(2)The stress on the internal fixation was much greater than the stress on the bone fracture fragments.The stress of the internal fixation was mainly concentrated in the area that near to the fracture end of the bone plate,among which the stress distribution of the volar fixed-angle anatomical plate,volar variable-angle locking plate was relatively uniform,and the stress concentration of the oblique T-locking plate was the most obvious.(3)Under compressive and torsional loads,the stress of the fracture fragments was mainly concentrated in the area that around the screw holes.Under dorsal and palmar flexion,it gradually expanded from the distal end to the proximal radius.Under the same load condition,the stress of the fracture block in the oblique T-locking plate fixation state was the highest,and the peak stress of the fracture fragments in the volar variable-angle locking plate fixation system was the lowest.The difference between the peak stress of the bone fracture fragments in the fixed state of the volar fixed-angle anatomical plate and the volar variable-angle locking plate was only in the range of 0.2-6.0 MPa.(4)It is indicated that compared with the oblique T-locking plate and the volar fixed-angle anatomical plate,the volar variable-angle locking plate has more uniform stress distribution,less displacement of articular surface,and the best stability in the internal fixation in the C1 type fracture of the distal radius.