Anatomic Parameters Of The Screw Channel In The Posterior Margin Of The Obturator

Nowadays,there are many research reports on the therapy of different types of acetabular fracture,but almost none of them has mentioned how to place a lag screw in the bony channel in posteromarginal obturator safely.However,according to some correlative biomechanical experiments,the stability of internal fixation can increase significantly after the placement of a lag screw in this channel.Meanwhile,this channel is very narrow,so it's very necessary to conduct detailed research on this bonny channel in posteromarginal obturator.Research ObjectiveMeasure the anatomical parameter for the placement of screw in the screw channel in the posterior margin of the obturator.Imitate the nailing process on bonny semi-pelvic specimens.Discuss a reasonable method to place the screw safely.Provide evidence of anatomy for the designation of a targeting device for the screw channel in the posterior margin of the obturator.Research MethodCT scan data of 50 normal adults was collected for the reconstruction of three-dimensional hemi-pelvic models(25 male,25 female).3-D models were reconstructed in mimicsl5.0,and disposed in Geomagic Studio 12.0.100 hollow 3-D hemi-pelvic models were required and stored in the form of.stl.The screw channel of each pelvis was confirmed using a novel method of axial perspective.Drew a vertical line from the entry point(O)to the arcuate line of pelvis(the intersection is marked as point A).Then collected point A and the symphysis pubis(B).The position of the entry point and entry angle were measured,including the maximum screw diameter,the maximum screw length,OA,AB,the intersection angle a between the entry direction and the coronal plane,the intersection angle? between the entry direction and the vertical plane,the extraversion angulation ?and the retroversion angulation ?.After statistical treatment of the measured data,13 complete bony hemi-pelvic specimens were selected to handle the imitation of nailing process(8male,5 female).None of the specimens was observed malformed or catagmatic both under eyes and X-ray.Then imitated to place a lag screw in the screw channel in posteromarginal obturator and counted the success rate.Research ResultsMale:the mean maximum screw diameter was(6.48 ±1.07)mm,the mean maximum screw length was(98.03±4.08)mm;the average OA was(7.93±2.30)mm,the average AB was(55.99 ±4.83)mm;the average ? a was(48.93 ±3.72)°,the average ? ? was(2.42± 1.10)°,the average ? ? was(79.17±9.89)°,and the average ? ? was(108.72 ±6.13)°.Female:the mean maximum screw diameter was(5.87±1.34)mm,the mean maximum screw length was(87.34±4.76)mm;the average OA was(3.77± 1.37)mm,the average AB was(63.66 ?4.74)mm;the average ? a was(47.03 ±4.18)°,the average ?? was(5.34±1.81)°,the average ? ? was(71.81 ± 10.61)°,and the average ?? was(98.12 ± 7.43)°.All the parameters were statistically significant(p<0.05).8 male hemi-pelvic bony specimens were successfully implanted a Kirschner wire which is 3.5mm in diameter,and the success rate was 100%.4 of 5 female hemi-pelvic bony specimens were successfully implanted a Kirschner wire of 3.5mm,and the success rate was 80%.Research ConclusionsIt's feasible to implant a lag screw,which is at least 3.5mm in diameter,into the screw channel in the posterior margin of the obturator.The parameters can be used for the designation of the targeting device for this screw channel.