Application Of 3D Printing Navigation Template In The Second Sacral Ala-Ilia Screw Placement

Objective:To investigate the the clinical feasibility of applicating a 3D printing navigation template for the second sacral ala-ilia(S2AI)screw placement and analyze the accuraev and safety of the screw insertion.Methods:From September 201 6 to May 201 8.the clinical and imagine data of patients undergoing the second sacral ala-ilia(S2AI)screw placement assisted by a 3D printing navigation template in our hospital were selected.There were 15 patients.including 12 males and 3 females.aged 23-68 years old.The pathogenesis included postoperative revisions of lumbar spine in 2 cases,severe lumbar spondylolisthesis in 3 cases,lumbar disc herniation in 3 cases,degenerative scoliosis in 7 cases.All patients had undergone pelvic CT scanning before operation.The interval of pelvic CT scanning was 1mm.The dates was saved in form of Dicom and transformed into pelvic three-dimensional model by computer reconstruction software.it used a cylinder of a certain diameter to replace the screw to simulate the the second sacral ala-ilia(S2AI)screw placement in the target vertebral body model.We adjusted the nail carefully and repeatedly in order to find the best position and design the ideal nail path of the screw.According to the reverse engineering principle,the computer hed made a navigational template which was consistent with the shape of the bone surface structure.Based on the preset axis line of the cylinder,the benchmark was reconstructed.According to the Boolean Operation.the benchmark was moved parallelly 8?10mm towards the position of the screw insertion hole.the two parts had been combined to form a navigation template with a direction pole and then the designed navigation template is printed out through a 3D printer for disinfection.During the operation,the 3D printed navigation template is placed in the target area behind the S2 lamina and closely adhered to the bony structure.The surgeon established the nail path according to the direction of the guide pole of the navigation template and combined with intraoperative X-ra,,.The CT was performed after operation and the screw parameters of the pre-scheduled nail and the actual nail were compared to analyze the accuracy of the screw.We had heen used the CT scanning coronal position to observe the relationship between the actual screw position and the pelvic cortical bone to evaluate the safety of screw placement;Results:All patients had underwent operation successfully with the average operation time of(114.2±47.6)min and the average blood loss of(356.2±172.6)mL.A total of 30 the second sacral ala-ilia screws were placed.All the screw were implanted through the sacroiliac joint without piercing the iliac bone cortex.Using computer software to measure the actual the second sacral ala-ilia screw parameters:the Sagittal angle(SA),the Transverse angle(TA),the horizontal distance(HD)and the vertical distance(VD).The results are SA(preoperative):31.70°±1.03??TA(preoperative):36.47°±2.60°?HD(preoperative):13.53± 1.50 mm?VD(preoperative):5.24±0.15 mm;SA(postoperative)31.65°± 1.03°?TA(postoperative):36.53°±-2.77°?HD(postoperative):13.57± 1.47 mm?VD(Postoperative):5.23±0.19 mm.There was no significant difference between the preoperative design and postoperative measurements in terms of the second sacral ala-ilia screw parameters(P>0.05):Conclusion:The accuracv and safetv of the second sacral ala-ilia(S2AI)screw placement assisted by 3D printing navigation template can be effectively improved.It also can reduce the deviation of nail placement and decrease the injury to nerve and vessel.The 3D printing navigation template has simple production process and low material price,so it can have good clinical application prospects.