| Objective:1.To study the important blood vessels and nerve structures of the adult pelvis adjacent to the second sacral vertebra and the iliac bone by means of gross anatomy,and to provide anatomical basis for the screw placement technique of S2 AI.2.By the use of digital orthopedics technology,the digital anatomy of the pelvic structure,finding the ideal screw trajectory of S2 AI screw placement technology and measure the screw placement parameters,providing data reference and methods for the screw placement relying on assistive technology.3.By studying imaging anatomy of the pelvic fluoroscopy through the method of simulated X-ray fluoroscopy,and proposing the intraoperative fluoroscopy imaging judgment method of S2 AI screw placement,to provide a reference for the intraoperative fluoroscopy method of S2 AI screw.4.Designed and produced the 3D printed navigation template of S2 AI screw placement technology.Combined with the research results of cadaver,digital and image anatomy,to verify the feasibility of navigation template assisted screw placement through clinical application.Methods:1.The selection by formalin soaked by the arterial perfusion red latex pelvic corrosion specimens of 8 cases(male 4 cases,female 4 cases),on the perfusion specimens removed pelvic cavity viscera structure observation measurement,in order to facilitate along lines of neurovascular exposed in turn around the pelvis neurovascular structures,to find and confirm the 1st and 2nd sacral posterior foramen location.The zone where the midpoint of the connecting line of the 1st and 2nd sacral posterior foramen was used as the S2 AI screw entry zone,the vascular and neural structures around the S2 AI screw were observed and described,the structure was divided into regions and the anatomical relationship was described.The closest distance between the entry point of the S2 AI screw and the zone was measured according to the regions,and the results were statistically analyzed.2.CT data of 30 adults(15 males and 15 females)in the imaging department of the 920 nd Hospital of joint logistics Support Force of the Chinese people's liberation army were collected.All data were recorded into Mimics 19.0 in DICOM format for 3D reconstruction,and finally a full pelvis 3D model of 30 STL formats was obtained;Geomagic Studio 2017 will import 3d data to fill and repair the model for image processing.A set of cutting planes was created parallel to the coronal plane,with the plane spacing of 3mm.The whole pelvis was divided into several planes,starting from the dorsal sacral cortex and ending from the anterior superior iliac acanthosis.Respectively in the second sacral vertebra,sacroiliac joint part,and obtained the section outline of ilium(target zone),the maximum inscribed circle fitting,and mark the position of the center of a circle with one side of the sacral vertebral,sacroiliac joint part and the cutting of ilium arranged on the surface of the maximum inscribed circle in the coronal plane became a safe osseous channel,the channel that is safety zone of S2 AI screws.Using the linear fitting function built-in in Geomagic Studio,for all the plane inscribed circles in the channel,the line calculated by least square method with the center of the circle scattered in space is defined as the axis line of the safe channel,which is also the trajectory where the longest ideal trajectory is located in the safety zone.The center of the maximum inscribed circle cut off by the sacral vertebra,the sacroiliac joint and the iliac bone on the same side was fitted again within the length of 90 mm and 70 mm,respectively,to obtain 90 mm and 70 mm ideal screw trajectory.The intersection of the screw trajectory with the dorsal cortex of the second sacral vertebra was considered the ideal entry point for the screw trajectory within the length.The relationship between the enter piont of each ideal trajectory with the position of the 1st sacral foramen and the direction of the nailing path were measured.For fitting of 90 mm,70 mm ideal screw diameter to expand,until the cylinder just contact to the border of inscribed circle,record the largest cylinder diameter,through statistical analysis of the comparison of the different length of ideal screw trajectory into enter point,direction of change and fitting of the diameter of the biggest differences.3.30 cases of complete transparency,3D reconstruction of the pelvis model along the axis of the model is a gradually to obturator oblique view and outlet view every 5°rotation,until transparent pelvic present "tear drop" view;The Mimics19.0 software was used to simulate the X-ray imaging of the pelvis,and the correlation between the transparency of the zone and X-ray the imaging of the pelvis was validated.A screw with a length of 80 mm and a diameter of 8mm is virtually inserted along the ideal screw trajectory.Continue to rotate the pelvis in units of 5° until the zone of “tear drop” obtained during the simulation is the largest.The resulting image is called a standard view,and the rotation angle of the pelvis in different planes is recorded.The head direction of the 80 mm S2AI screw was adjusted until the surrounding cortical bone was just broken out.The cortical bone of the inner wall of the iliac crest,the outer wall of the iliac crest and the position of the sciatic notch were simulated respectively.The cortical violation of the screw on the standard view was observed.The value of "tear drop" view for S2 AI screw safety placement was determined by observing the simulation results,and the difference in rotation Angle between sexes was compared and statistically described.4.A retrospective analysis was performed on the 17 patients with S2 AI screw placement in our department,according to the patients by placing S2 AI screw operation method,divided the patients into two groups: the navigation template group 5 cases,freehand group of 12 cases,and the navigation template to 3D reconstruction group of preoperative pelvic CT data,through the effects of different individual ideal preoperative planning design navigation template and use 3D printing production into an object,and used in intraoperative navigation template auxiliary S2 AI screw placement;In the freehand screw placement group,S2 AI screws were inserted through the freehand technique used in this study.Intraoperative based on standard standard "tear drop" view as to verify its clinical application value,compared two groups of patients who unilateral of screw one-time success rate of placement,single screw placement time,intraoperative blood loss.Postoperative patients with pelvic CT,review of the Mimics reconstruction after observing the image relationship between screw and the sacrum and ilium bone cortex,the navigation template group of preoperative simulation and postoperative of enter point and direction measurement,statistical analysis comparing the difference between the preoperative postoperative position and direction.Result:1.According to the anatomical relationship between the pelvic neurovascular structures and the screw entry point of S2 AI,it can be divided into four zones: the anterior sacral zone,the inner wall zone of the iliac crest,the greater sciatic notch zone,and the outer wall zone of the iliac crest.The anterior sacral zone mainly includes the sacral plexus nerve,the middle sacral arteriovenous and the lateral sacral arteriovenous.Iliac inner wall zone mainly includes internal iliac artery and vein,external iliac artery and vein,iliac waist artery and vein,obturator artery and vein,deep circumflex iliac artery and vein,obturator nerve,reproductive femoral nerve,etc.The greater sciatic notch includes superior gluteal artery and vein,inferior gluteal artery and vein,part of sacral plexus,sciatic nerve,superior gluteal nerve and inferior gluteal nerve.The outer wall of the iliac crest mainly consists of the superior gluteal artery and vein and the superior gluteal nerve.The closest distance between the screw entry point and each region was 22.69±2.54 mm.The inner wall zone of the iliac crest was 49.15±3.84 mm.The greater sciatic notch was 45.79±2.65 mm.The outer parietal region of the iliac crest was 50.55±2.73 mm.The anterior sacral region was 24.17±2.32 mm in males and 21.22±1.94 mm in females.Male iliac crest inner wall region was 51.09±3.32 mm,female was 47.21±3.68 mm.The greater sciatic notch was 46.73 ±2.97 mm in male and 44.84±2.22 mm in female.Male iliac crest outer wall zone was 51.82 ±2.12 mm,female 49.29±2.19 mm.There was no statistical difference between the sexes.2.The maximal inscribed circle of the intersecting plane of the sacral vertebra,the sacroiliac joint and the iliac bone on the same side forms an irregular bony passage,which is the S2 AI safety zone for screw placement.The axis line of the safety zone is obtained by fitting the center of the maximum inscribed circle of all planes,that is,the longest ideal screw trajectory.The ideal screw trajectory of 90 mm and 70 mm was obtained by fitting the center of the circle in the range of 90 mm and 70 mm respectively.In the safety zone,the average length of the longest screw trajectory was 111.79±9.48 mm,and the point of intersection with the first dorsal sacral cortex was 4.16±1.97 mm for the a value and 3.85±1.49 mm for the b value.The 90 mm ideal screw trajectory of a value is 0.73±2.57 mm,the b value is 3.78±1.42 mm,the 70 mm ideal screw trajectory of a value is-3.14±2.58 mm,and the b value is 3.87±1.51 mm.There was a significant statistical difference in the horizontal a value between the three groups.With the reduction of the length of the screw trajectory,the position of the entry point was gradually close to the middle crest of sacrum from the sacral foramen.However,there was no significant statistical difference in the vertical distance b,and the change of the screw trajectory length did not affect the change of the ideal entry point in the vertical direction.Ideal longest screw trajectory the ? value is 34.81 ±3.70 °,? is 38.96 ±3.73 °,90 mm ideal screw trajectory the ? value is 31.16 ± 3.33 °,? is 42.20 ±3.66 °,70 mm ideal screw trajectory the ? value is 25.96± 3.63 °,? is 47.55 ±4.55 °.There were statistically significant differences between the three groups.As the length of ideal screw trajectory decreased,the average value of ? decreased gradually,and the value of ? increased gradually.With the change of fitting length,the location of the ideal screw trajectory deviates from the enter point and the direction of the axis line in the safety zone.The shorter the ideal nail path,the greater the deviation.The diameter of the maximum fitting cylinder in the 90 mm screw trajectory was 13.22±1.81 mm,while the diameter of the 70 mm screw trajectory was 16.95±1.57 mm.There was a significant statistical difference between the two value.The shorter S2 AI screw could fit the larger cylinder.3.Through the X-ray simulation function of Mimics,it can be observed that the triangular area enclosed by the inner wall,outer wall and sciatic notch of the iliac crest after the pelvis became transparent is consistent with the "tear drop" view.On the standard view,a 80 mm virtual cylinder with a diameter of 8mm and a length of 80 mm was placed in the ideal screw trajectory.The head end of the cylinder,witch is the screw head position,was projected onto the triangle area of "tear drop".The measured angle ? of rotation along the human coronal axis is 24.58±4.15°,and the angle ? of rotation along the vertical axis of the human body is 27.75±3.95°,wherein the male ? is 23.67±4.10°,the female is 25.50±3.91°,and the male ? is 26.83±3.83°,female was 28.67±3.99°;independent sample rank sum test was performed between genders.All the results were p>0.05 between male and female,no statistical difference.In the case of cortical violation of the simulated screw,when the inner wall of the iliac crest,the outer wall of the iliac crest and the sciatic notch punctured,it can be observed that the screw head overlaps or penetrates with the edge of the triangle of the tear drop,that is,the projection of the screw head is no longer located in the inner part of the "tear drop" triangle.From the perspective of clinical practical value,the standard image is helpful to judge the placement of S2 AI screws.4.Navigation template group: a total of 5 patients designed 10 S2 AI screw individualized assisted navigation template,all cases of sacral 2 iliac screws are the use of individual navigation templates for screws placement,intraoperative fluoroscopy record one-time successful 10 screws placement,success rate of 100%,the average time needed for unilateral of screw implantation was 184.90 ± 68.79 s,intraoperative blood loss 1064.0 ±383.70 ml,postoperative,according to the CT 10 screws through the sacroiliac joint and located in ilium,the iliac crest bone cortex is complete without break,is consistent with the results of intraoperative fluoroscopy;Preoperative simulation set into the Angle SA(32.22 ±5.57°)and TA(42.59 ±4.55°),HD(5.04 ±0.40 mm),VD(19.58 ±1.49 mm),and postoperative CT after review of the measurement of SA(31.95±5.78 °)and TA(42.21±5.29°),HD(5.00 ±0.41 mm),VD(19.54 ±1.12 mm)for statistical analysis of paired sample mean compared,there were no statistically significant difference.Freehand group: a total of 12 patients in the 22 pieces of screw(including 2 cases of unilateral),intraoperative fluoroscopy record one-time successful 19 screws placement,success rate 86%,the average time needed for unilateral of transpedicular screw was 246.50 ±86.82 s,intraoperative blood loss 1030.0 ± 284.0 ml.There was a statistically significant difference in the time required to insert a single screw between the free hand group and the navigation template group,but no statistically significant difference in the success rate of one-time screw placement and intraoperative blood loss.Conclusion:1.According to the anatomical relationship between the pelvic neurovascular structures and the screw entry point of S2 AI,it can be divided into four zones: the anterior sacral zone,the inner wall zone of the iliac crest,the greater sciatic notch zone,and the outer wall zone of the iliac crest.The incorrect placement of the traditional length of the S2 AI screw may cause damage to the vascular nerve structure in each zone.By partitioning,the relationship between the screw and the cortical bone may be associated with the corresponding surrounding anatomy.A reference is made to the selection of the appropriate screw length and the risk of possible breakage.2.It is a feasible method to obtain the safety screw placement zone of S2 AI screws through the digital design of the pelvic model and calculate and fit the ideal screw trajectory S2 AI.The optimal screw placement method is obtained by matching the screw length with the corresponding screw setting parameters due to the different screw entry points and angles.3.It is a feasible method to simulate intraoperative fluoroscopy by using the software.The triangular area enclosed by the inner and outer wall of the ilium and sciatic notch observed on the transparent pelvic model is consistent with the "teardrop" view formed by the pelvic X-ray.Standard "tear drop" view of the pelvis can be used to assess the accuracy of S2 AI screw placement during surgery.4.In adult pelvic fixation,the individualized navigation template assisted by S2 AI screw placement technique is a feasible placement technique,and the calculation of the ideal screw trajectory can provide a method reference for the design of the trajectory of the navigation template. |
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