| Objective: To study the structure of the posterior column of the acetabulum with three-dimensional CT reconstruction technique,and measure the parameters of osseous tunnel for the antegrade lag screw.To provide a theoretical basis for the clinical application of antegrade lag screw in acetabular posterior column.Methods: 30 complete pelvic CT image data of healthy adults were collected in our hospital CT room between September 2015 and September 2016,including 15 males and 15 females.Cases with bone lesions,anatomic abnormalities and abnormal situation was excluded.The image data was saved in DICOM format and input into Mimicsl7.1 software,then the 3D reconstruction of the pelvis images was conducted.Simulated retrograde lag screw was insert into the posterior column of the acetabulum with ischial tuberosity and lesser sciatic notch as the entry point respectively,screw diameter,screw length,the angle between the screw and sagittal plane as well as coronal plane was measured;the distance between the optimal entry point and the edge of the arcuate line as well as the ending point of the arcuate line was measured,the parameters of nail security osseous tunnel was also measured.The data were statistically analyzed,and the differences between the different gender were compared.Results: The ischial tuberosity group:the diameter and length of the retrograde lag screw was(12.83 + 1.76)mm,(139.87 + 6.57)mm respectively in male,the angle between the screw and the sagittal plane as well as the coronal plane was(9.80 + 1.61)°,(14.46 + 3.94)° respectively in male,the diameter and length of the retrograde lag screw was(10.53 + 1.59)mm,(125.47 + 7.19)mm respectively in female,the angle between the screw and the sagittal plane as well as the coronal plane was(8.07 + 1.58)°,(10.93 + 3.05)° respectively in female.The lesser sciatic notch group:the diameter and length of the retrograde lag screw was(10.60±1.55)mm,(112.73±6.98)mm respectively in male,the angle between the screw and the sagittal plane as well as the coronal plane was(19.27±3.35)°,(40.73±2.46)° respectively in male,the diameter and length of the retrograde lag screw was(9.33±1.23)mm,(93.93±9.84)mm respectively in female,the angle between the screw and the sagittal plane as well as the coronal plane was(15.67±3.11)°,(42.13±4.25)° respectively in female.The diameter of the retrograde lag screw,the length of the retrograde lag screw,the angle the screw and the sagittal plane as well as the coronal plane was significant difference between male and female as well as the ischial tuberosity group and the lesser sciatic notch group.The distance between the optimal entry point and the edge of the arcuate line as well as the ending point of the arcuate line was(13.76 + 1.96)mm,(16.08 + 3.77)mm respectively in male,the distance between the optimal entry point and the edge of the arcuate line as well as the ending point of the arcuate line was(12.83±1.75)mm,(15.14 + 2.56)mm respectively in female.The distance was significant difference between male and female.The entry point of the antegrade lag screw which was in the safe zone formed an approximate "triangle"(?BCD)area in iliac plate,the security osseous channel of the lag screw formen an approximation "tetrahedron"(A-BCD).In male group the length of the screw AB was(102.67±4.32)mm,the angle between the screw AB and the sagittal plane as well as the coronal plane was(7.74±2.59)°,(23.17±3.92)° respectively.The distance between the point B and the ASIS?PSIS as well as the ending point of the arcuate line was(68.29±2.73)mm?(46.34±2.57)mm?(32.16±4.35)mm respectively.In female group the length of the screw AB was(99.54±3.97)mm,the angle between the screw AB and the sagittal plane as well as the coronal plane was(6.07±2.25)°,(20.27±4.28)° respectively.The distance between the point B and the ASIS?PSIS as well as the ending point of the arcuate line was(66.34±2.89)mm?(46.59±2.26)mm?(33.69±5.13)mm respectively.In male group the length of the screw AD was(133.96±6.37)mm,the angle between the screw AD and the sagittal plane as well as the coronal plane was(10.21±2.74)°,(9.27±2.87)° respectively.The distance between the point D and the ASIS?PSIS as well as the ending point of the arcuate line was(85.07±4.90)mm?(82.14±4.82)mm?(30.49±4.30)mm respectively.In female group the length of the screw AD was(120.65±6.07)mm,the angle between the screw AD and the sagittal plane as well as the coronal plane was(7.87±2.53)°,(9.30±2.69)° respectively.The distance between the point D and the ASIS?PSIS as well as the ending point of the arcuate line was(75.24±4.37)mm ?(69.27±4.03)mm ?(29.79±4.18)mm respectively.In male group the length of the screw AC was(143.64±6.37)mm,the angle between the screw AC and the sagittal plane as well as the coronal plane was(20.46±3.28)°,(17.26±3.96)° respectively.The distance between the point C and the ASIS?PSIS as well as the ending point of the arcuate line was(58.37±4.46)mm?(68.38±4.69)mm?(53.51±4.31)mm respectively.In female group the length of the screw AC was(124.77±5.97)mm,the angle between the screw AC and the sagittal plane as well as the coronal plane was(14.36±3.19)°,(14.74±4.07)° respectively.The distance between the point C and the ASIS?PSIS as well as the ending point of the arcuate line was(57.93±4.27)mm?(57.36±4.34)mm?(49.45±4.97)mm respectively.Screw AB is the shortest screw in the safe osseous tunnel,screw AC is the longest in the safe osseous tunnel.With sagittal plane Angle of screw AC > screw AD > screw AB,with coronal plane angle of screw AB > screw AD >screw AC,The was angle adjustment on the sagittal plane and coronal plane when insert the antegrade lag screw.The length of the screw AB,the angle between screw AB and sagittal plane and coronal plane was significant different between male and female.The distance between point B and ASIS?PSIS and the ending point of arcuate line was no significant different between male and female.The length of the screw AD,the angle between the screw AD and the sagittal plane,the distance between ASIS and PSIS was significant different between male and female.The angle between the screw AD and the coronal plane,the distance between point D and the ending point of the arcuate line was no significant different between male and female.The length of the screw AC,the angle between screw AC and sagittal plane as well as coronal plane,the distance between point C and PSIS as well as the ending point of the arcuate line was significant different between male and female.The distance between point C and ASIS was no significant between male and female.Conclusion: 1.The diameter of 6.5mm screw can be retrograde inserted into the posterior column of acetabulum with the sciatic tuberosity and the lesser sciatic notch as entry point 2.The entry point of the antegrade lag screw which was in the safe zone formed an approximate "triangle"(?BCD)area in iliac plate,the security osseous channel of the lag screw formen an approximation "tetrahedron"(A-BCD).3.All the parameters have individual differences,individualized treatment plan for the patient according to the results of preoperative CT scan can formulate.4.Using mimics software helps the anatomical study of the acetabular posterior column,is helpful for the clinical application of the technology. |
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