RESUMO
Objective:To investigate the accuracy of infra-acetabular screw implantation assisted by a 3D-printed personalized screw guide in vitro. Methods:The imaging data were collected of the 10 patients with acetabular fracture involving the anterior column who had been treated at Department of Orthopaedics, The Fourth Hospital of Wuhan from June 2015 to October 2021. There were 8 males and 2 females, with an average age of (42.6±2.1) years. According to the Letournel-Judet classification, there were 2 anterior column fractures, 4 anterior column + posterior semi-transverse fractures, 3 double column fractures, and 1 T-shaped fracture. The thin-slice CT scan data of the patients’ pelves were imported into the E3D software to generate digital 3D fracture models in which fracture reduction and post-reduction were simulated and personalized screw guides for infra-acetabular screw implantation were generated. After the above models were printed by a 3D printer, the fracture models were reduced in vitro and the infra-acetabular screws were implanted assisted by the personalized guide on the affected and healthy acetabulum models. After operation, the printed models were scanned by CT again, and the CT data were imported into the E3D software again to generate the postoperative digital 3D models. The position relationships were observed between the screws and the cortex around the corridor on the postoperative CT scan images. The consistency of the position parameters was compared between pre- and post-operation for each screw in the digital models. Results:Ten personalized screw guides were generalized respectively for the affected and healthy sides of the 10 patients in this group. Anatomical reduction was achieved in vitro in all the 3D printed fracture models. A total of 20 infra-acetabular screws were implanted with the assistance by the screw guide. According to the Andrew's CT grading for pedicle screw positions, 19 infra-acetabular screws were rated as grade Ⅰ and 1 was rated as grade Ⅱ. The linear distance from the midpoint of the pubic symphysis to the point of insertion, and the angles between the axis of the screw and the horizontal, sagittal and coronal planes on the health side before operation were respectively (60.65±5.55) mm, 23.96°±5.59°),2.88 °±1.25°, and 65.06°±5.48°, showing insignificant differences from the postoperative values [(60.91±5.73) mm, 24.00°±6.15°, 3.20°±1.13°, and 65.74°±5.57°] ( P>0.05); the above screw position parameters on the affected side before operation were respectively (60.76±4.41) mm, 24.77°±2.97°, 3.06° (2.66°, 3.68°), and 63.70° (62.70°, 65.60°), showing insignificant differences from the postoperative values [(60.71±4.56) mm, 24.67°±2.73°, 3.04° (2.64°, 3.51°), and 64.40°(63.20°, 65.90°)] ( P>0.05). Conclusion:In the models in vitro, implantation of infra-acetabular screws assisted by a 3D printed personalized screw guide can be highly accurate, owing to insignificant differences in all the position parameters between the simulated operations and the operations in vitro.
RESUMO
OBJECTIVE@#To measure the maximum corridor parameters of the infra acetabular screw and evaluate the feasibility of screw insertion through digital analysis of the acetabular structure.@*METHODS@#The pelvic CT data of 100 patients who received plain pelvic CT scan from April 2013 to June 2015 were retrospectively analyzed. There were 50 males, aged 20 to 84 years, with an average age of (48.42±17.48) years, and 50 females, aged 18 to 87 years, with an average age of (55.02±19.54) years. Patients with acetabular fractures, hip dysplasia, and metal implants in the acetabulum were excluded. Import CT data into Mimics software in DICOM format to generate a three-dimensional model, and find the axialprojection of the infra-acetabular corridor in the middle of the pubis ramus in the inlet view. A virtual screw was placed in the infra-acetabular space and measure the parameters including the diameter and the length of the maximum corridor, the distance from the insertion point to the pubic symphysis, to the anterosuperior iliac spine and to the medial edge of the pelvis. Then import the pelvic model into 3- matic software, establish the pelvic model anterior pelvic plane and median sagittal plane, and measure the angle between the screw axis and the two planes. A minimum corridor diameter of at least 5 mm was defined as a cutoff for placing a 3.5 mm screw, and calculate the screw insertion rate.@*RESULTS@#In 100 cases, 49% of patients had a infra acetabular corridor with a diameter ≥5 mm, and the rate of screw placement in men was significantly higher than that in women. The average diameter of the maximum corridor of infra-acetabular screw was (4.86±1.72) mm, the average length was (94.04±8.29) mm, the average distance from the insertion point to the pubic symphysis was (60.92±4.84) mm, to the anterosuperior iliac spine was (85.15± 6.85) mm, and to the medial edge of the pelvis was (6.12±3.32) mm. The mean angle between the axis of the screw and the median sagittal plane was (-1.38±4.74)°, and the mean angle between the axis of the screw and the anterior pelvic plane was (56.77±7.93)°. There are significant differences between male and female measured parameters, except for the angle between the screw axis and the anterior pelvic plane. There was no statistically significant difference in the maximum corridor parameters of infra-acetabular screw on both sides of the pelvis.@*CONCLUSION@#This study shows that the insertion rate of infra-acetabular screws is low in local patients, and the feasibility of screw insertion should be fully evaluated before surgery.