| Objective : The present study analyzes the biomechanical characteristics of treating distal radius fractures with dorsal ulnar fragment with only volar locking plate fixation and combined dorsal mini-plate fixation,through biomechanical methods.It explores the optimal internal fixation methods for different fracture patterns of distal radius fractures with dorsal ulnar fragment,providing a more clearer theoretical basis for the treatment of distal radius fractures with dorsal ulnar fragment.Methods:In this study,30 radial bone specimens were produced using 3D printing technology and divided into three groups to establish distal radius fracture models with dorsal ulnar fragment.Group 1 established distal radius fracture models with a dorsal ulnar fragment not exceeding the Lister tubercle;Group 2 established distal radius fracture models with a dorsal ulnar fragment exceeding the Lister tubercle;Group 3established distal radius fracture models with comminuted fractures with dorsal ulnar fragment.Each group model was randomly fixed with only volar locking plate or volar locking plate combined with the dorsal mini-plate.The prepared models were installed in a custom biomechanical fixture and subjected to non-destructive axial loading tests and failure load tests.The loading tests involved 3000 cycles of loading from 0 N to 100 N at a rate of 10 N/S for the cyclic load test,and continuous loading at a rate of 5 N/S for the failure load test.The cyclic load test recorded the displacement of the dorsal fragment at each cycle and calculated the stiffness every 1000 cycles.The failure load test generated the load-displacement curve and calculated the elastic limit and failure load of each model.Results: In the cyclic load test,all test models have not failed.Stiffness comparison of models in each group: there was no significant difference in stiffness comparison of each stage in group 2(P>0.05);In the initial stage,there was no significant difference in stiffness(P>0.05)between Group 1,which had the volar locking plate combined with the dorsal mini-plate fixed at the 1000 th cycle(247±26N/mm),2000 th cycle(292±23N/mm),and 3000 th cycle(316±29N/mm),and the stiffness values were all significantly better than those of the only volar locking plate fixed at the 1000 th cycle(204±27N/mm),2000 th cycle(242±39N/mm),and3000 th cycle(265±35N/mm),with significant differences(P<0.05).Group 3,which had the volar locking plate combined with the dorsal mini-plate fixed at the initial stage(182±16N/mm),1000 th cycle(199±22N/mm),2000 th cycle(217±19N/mm),and3000 th cycle(252±27N/mm),had significantly better stiffness values than those of the volar locking plate fixed at the initial stage(141±29N/mm),1000 th cycle(161±26N/mm),2000 th cycle(183±25N/mm),and 3000 th cycle(185±23N/mm),with significant differences(P<0.05).In Group 2,the volar locking plate combined with the dorsal mini-plate had the highest stiffness at the initial stage,1000 th cycle,2000 th cycle,and 3000 th cycle,but there was no statistically significant difference between the groups(P>0.05);In the failure load test,the elastic limits of the models in each group were compared: Group 1 had elastic limits of 1134±266N(volar locking plate fixation)and1592±231N(volar locking plate combined with dorsal mini-plate fixation),with significant differences(P<0.05);Group 2 had elastic limits of 1453±240N(volar locking plate fixation)and 1746±212N(volar locking plate combined with dorsal mini-plate fixation),with no significant difference(P > 0.05);Group 3 had elastic limits of1019±186N(volar locking plate fixation)and 1383±192N(volar locking plate combined with dorsal mini-plate fixation),with significant differences(P<0.05).The failure loads of the models in each group were compared: Group 1 had failure loads of 1543±170N(volar locking plate fixation)and 1863±182N(volar locking plate combined with dorsal mini-plate fixation),with significant differences(P<0.05);Group 2 had failure loads of1798±159N(volar locking plate fixation)and 1969±208N(volar locking plate combined with dorsal mini-plate fixation),with no significant difference(P>0.05);Group 3 had failure loads of 1249±180N(volar locking plate fixation)and 1547±151N(volar locking plate combined with dorsal mini-plate fixation),with significant differences(P<0.05).Conclusion: 1.For comminuted distal radius fractures or fractures with a small dorsal ulnar fragment that does not exceed the Lister tubercle,the stiffness and axial compression strength of the volar locking plate combined with dorsal mini-plate fixation are superior to those of the only volar locking plate,which can provide stronger fixation in the early stage of fracture healing.2.For distal radius fractures with a large dorsal ulnar fragment that exceeds the Lister tubercle,there was no significant difference in biomechanical stability between the group with only volar locking plate and the group with volar locking plate combined with dorsal mini-plate in cyclic loading and destructive testing,indicating that the biomechanical stability of the two fixation methods is essentially the same. |
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