| Background:Pelvic crescent fracture-dislocation is a subtype of lateral compression injury.In particular,Day type-II injury covers 1/3 of the sacroiliac articulation,but at present,there is still a controversy on the operative approach and fixation technique in clinical practice.We have put forward closed reduction and percutaneous cross-screw fixation for treating type-II crescent fracture-dislocation.In order to identify its biomechanical properties and clinical effects,we designed this subject of research.Objective:1.To compare five internal fixation methods in the biomechanical stability of Day type-II pelvic crescent pelvic fracture-dislocation,to provide a theoretical basis for clinical practice.2.To investigate the clinical effect of treating Day type-II pelvic crescent fracture-dislocation by percutaneous cross-screw fixation.Methods:1.A digital model was built for screw penetrating through the posterior iliac bone tunnel.The angle between it and different planes was calculated,and the correlative distance was measured.2.5 different fixations were established and applied to the finite element model of Day type-Ⅱ pelvic crescent fracture-dislocation.600-N stress was applied to S1 vertebral endplate,for a comparison of stress and displacement distribution between pelvis and crescent bone blocks.3.5 pelvic specimen models were built as said and tested.Load was applied at the speed of 15N/s in the range of 0-600N,and displacement-stress data was recorded and made into a graph.4.A retrospective review was performed of 56 patients with Day type-II crescent pelvic fracture dislocation that had received operative treatment.Among them,35 patients received percutaneous cross-screw fixation,while 21 received open reduction-fixation,and both groups of patients’ conditions during operation and hospitalization were recorded;Matta scores were assigned after operation,and the Majeed functional scores of pelvis were recorded in the final follow-up visit.Results:1.The angle between hollow screw and horizontal plane,coronal plane as well as sagittal plane showed no statistically significant difference between the sexes(P>0.05);The theoretical maximum length of hollow screw,the minimum distance between its running direction and iliac bone beside sacroiliac articulation,the minimum distance between entry point and iliac bone beside sacroiliac articulation,and the distance to the leading edge of sacroiliac articulation were less in women than in men,showing a statistically significant difference(P<0.05).2.The maximum pelvic displacements in the finite element model were compared as follows:model E<model D<model A<model C<model B.The maximum displacements of crescent bone blocks were compared as follows:model E<model B<model D<model A<model C.The displacement-stress curve slopes in the pelvic specimen model were compared as follows:model E>model D>model A>model C>model B.3.The percutaneous fixation group had advantages in operation duration,bleeding volume,operative incision length and average hospital stay,and all differences were statistical significance(P<0.01).The difference in Matta scores after operation and Majeed scores in the final follow-up was not statistically significant(P>0.05).Conclusions:1.The fixation with 3 crossed screws has the best biomechanical properties,similar to the fixation with 2 crossed screws in global mechanical stability;but the fixation of crescent bone blocks with 1 screw has poorer stability than with 2 screws.2.The fixation of both iliac fractures and sacroiliac articulations shows better biomechanical properties than that of iliac fractures or sacroiliac articulations;the fixation of sacroiliac articulations shows higher stability than that of iliac fractures.3.The posterior open reduction and fixation of mere iliac fractures recommended in most literatures is not applicable due to its poor biomechanical properties.4.The percutaneous cross-screw fixation method has a good clinical effect in treating Day type-Ⅱ crescent fracture-dislocation,and needs a certain learning curve.It is worth popularizing and applying. |
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