| ObjectiveOpen reduction and internal Wxation has been the gold standard for displaced fracture involving weightbearing dome and fractures with intra-articular fragments.However,extensile exposure can lead to complications,for example, posttraumatic arthrosis,blood loss,heterotopic ossification,neurologic and angiologic injury,infection,ea tl.Recently,percutaneous fixation were proposed the fracture of acetabular without displacement or with mild displacement,with the help of imaging navigation,and the outcomes were very well.Domestic and foreign scholars studied the lag screws for fixation of posterior column of acetabulum, including specimen and three-dimensional reconstruction models,and the the maximum diameter of screw and the insert point and angel were measured,but the results had a big difference.More importantly,the results were hard to applied to clinical practice.The appearance of digital orthopaedic has created a new era for the basic application research of orthopaedic and traumatology.Compared with the traditional cadaveric reseach,it has the lots of advantages,like high accuracy,good consistency,repeatability strong and saving medical resources.Our study the bony markers on the pelvis to study the percutaneous retrograde screw fixation for posterior column fractures of acetabulum on the pelvis' three dimensional reconstruction and to exeplore the feasibility of targeting device for percutaneous retrograde screw fixation for posterior column fractures of acetabulum,finaly to provide the applied anatomical basis for development of the targeting device.1.Using the bony markers on the pelvis,to simulate percutaneous retrograde lag screw fixation of posterior column of the acetabulum on the pelvis'three dimensional reconstruction,and to provide a new method for studying applied basic evidence for percutaneous retrograde lag screw fixation of posterior column of the acetabulum2.To provide the applied anatomical basis for the feasibility of the targeting device for percutaneous retrograde lag screw fixation of posterior column Of the acetabulum.3.To provide empirical method and evidence for the personal preoperative prepare of percutanous retrograde screws fixation of acetabular.Methods1.Collection of imagesObtained 29 adult patien randomly,who took complete CT scan of pelvis in our hospital between April 2006 and December 2007 without any bony and anatomy abnormality.13 males,16 females,age ranged 18～79 years,58 cadaveric hemipelves were collected.Scan condition:tube tension 120kV,tube current 200～300mA,slice increment 1.25 mm,matrix 512×512.All the images were saved as DICOM format and imported to the personal computer.2.Reconstruct the 3-dimensional model of pelvisAll the sequent tomoscan images of pelvis were imported into the Materialise's Interactive Medical Image Control System(Mimics) in personal computer as DICOM format.The 3-dimensonal models were reconstructed by the same calculated parameter. 3.Observation of three-dimensional reconstruction model of the pelvisObervation of three-dimensional reconstruction model of the pelvis,detemining the location of the relationship among anterior superior iliac spine and posterior superior iliac spine and ischial tuberosity of the three-dimensional space.We could find that three highlights on the anterior superior iliac spine and posterior superior iliac spine bone and the ischial tuberosity respectively that we could form an approximation to anterior superior iliac spine and posterior superior iliac spine to connect to the bottom edge of the isosceles triangle.So we could use the bony markers of the pelvis,including anterior superior iliac spine and posterior superior iliac spine bone and the ischial tuberosity,to simulate percutaneous retrograde lag screw fixation of posterior fractures of acetabulum.4.Simulated the screws fixation of anterior and posterior column of acetabularFind the most prominent bony points on the anterior superior iliac spine(ASIS) and posterior superior iliac spine(PSIS)and respectively marked as(A) and(B).And then draw a plane(α) that was perpendicular to the section AB and through the midpoint(M) of section AB.3D reconstruction model of pelvis was rotated to homonymy by 45 degrees(Iliac oblique view),Virtual cylindrical implants were placed intraosseously into the posterior column of acetabulum.The diameter of the virtual cylindrical implant was progressively increased,and back and obturator oblique views of pelvis were obtained to make sure that the virtual cylindrical implant did not penetrate the cortical margin of posterior column or into the acetabulum.Review the 2-dimensional images of the transverse plane;coronal plane and sagittal plane to avoid the virtual cylindrical implant penetrate the cortical margin of posterior column or into the acetabulum.The maximum diameter of the virtual implant was defined as the largest diameter that did not penetrate the cortex of the column regardless of its orientation.The maximum diameter of the virtual cylindrical implant and the distance between the insertion point(C) and distal ischiadic tuberosity(D) were measured.5.Measured the insert point and length of the screwsThe distance between the insert point and out point of virtual cylindrical implant were measured directly by the tool of 3D measurement.Then the length of screws were defined.The distant between the insert point of virtual cylindrical implants(C) and the distal of the ischiadic tuberosity(D) was measured.6.The experimental data was analyzed by the software of SPSS 13.0. Independent-samples t test and pair-sample t test were used,and an associated probability of 5%(P≦0.05) was considered significant.Results58(tewnty six males,thirty two females) hemipelves models were obtained,of which virtual cylindrical implants couldn't placed into the posterior column in one male and six female hemi-pelvic models.The main success rate was 51/56,and 25/26 in male and 26/32 in female.The mean maximum diameter of virtual cylindrical implant was(11.44±3.20)mm, range(4.5～16.9)mm,and(13.32±2.39)mm and(9.63±2.85) in male and female respectively,with a very significant difference(t=4.993,P＜0.0001).The distance CD was no significant difference between the males and females(t=0.236,P=0.815).The digital models that cylindrical implants(d=6.0mm) could be placed in accounted 82.76%of all models and 94.12% of the models that cylindrical implant could be placed in.The distance between points C and D was 19.10±5.10 mm.Virtual three-dimensional cylinder of maximum diameter(t=-0.661,P=0.515) and maximum length(t=-0.836,P=0.412),distance of CD(t=0.332,P=0.743) between the left and right pelvis was no significant difference.Conclusions1.Lag screws can be placed along the perpendicular bisector of the ASIS and PSIS for acetabular fractures,especially for males.And it provids the evidence of applied anatomy for the development of targeting device.2.The digital model of pelvis can not only provide a new method for the study of application basis research of percutaneous retrograde screws fixation of anterior and posterior column fracture,but also offer an ideal preoperative prepare for the the use of the technique. |
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