Eighteen patients underwent upper cervical pedicle screws placement and internal fixation in our hospital, were enrolled in this retrospective study from May 2010 to May 2019. These patients were divided into guide plate assisted screw implantation group (Group A, N=10) and traditional operation group (Group B, N=8). In group A, there are 6 males and 4 females, with an average age of 47.3 (30 to 65) years. All patients had spinal cord compression with neurological symptoms, 2 cases of atlantoaxial subluxation, 3 cases of atlantoaxial joint dislocation, 5 patients have symptoms of incomplete paralysis. In group B, there are 3 males and 4 females, with an average age of 40.4 (25 to 45) years. All patients have significant neurological symptoms, 4 cases with atlantoaxial dislocation, and 4 cases of incomplete paralysis. All included patients have complete follow-up data. The operation method has been approved by the ethics committee of our hospital, and all patients have signed the operation consent form.
Selection criteria
Inclusion criteria: (1) diagnosis of upper cervical spine deformity is clear, accompanied by obvious neurological symptoms; (2) the patient is older than 18 years old.
Exclusion criteria: (1) old fractures cause acquired deformities; (2) the degree of pedicle variability is too large to be fixed with pedicle screws; (3) the underlying disease cannot tolerate surgery; (4) follow-up information is incomplete.
Orientation template design
The patients in group A underwent spiral CT scan (Siemens, Germany) before the operation. The CT data of the upper cervical spine after the scan was converted into DICOM format for storage, and the stored data was transferred to Mimics 17.0 (Materialise, Belgium) to build a model. Select the target vertebral body in the Mimics virtual software, extract the anatomical structure of the atlantoaxial pedicle on the back of the deformed vertebral body, generate a virtual pedicle screw, and fit the best pedicle screw entry point, screw channel, and the length of screw to ensure that none of the virtual screws penetrate the four walls of the pedicle. In the software, design a guide tube with an inner diameter of 0.4cm, an outer diameter of 0.8cm, and a length of about 1.5 to 2.0cm. Combined with the anatomical shape of the back of the atlantoaxial vertebral body, a reverse 3D guide plate matching its anatomical characteristics is designed behind the vertebral body, and the final individualized atlantoaxial pedicle screw placement is fitted through the "Boolean calculation" in the software orientation template (shown in Figure 1).
Model, guide plate printing
Import the saved STL data into ideaMaker (China, Jiangsu) to verify the integrity of the model printing. Save the completed model in .gcode format and import it into a 3D printer (raise 3d N2 plus, Shanghai Maiditu Company). Use PLA as the printing material to print the upper cervical spine model at a ratio of 1:1. The printing parameters are: single layer Height: 0.25mm, filling rate 10.0%, printing speed 70.0mm/s, print out the model base, internal and external support and upper cervical spine model. In addition, print out 40 guide templates, 10 upper cervical spine models, and perform simulated surgery. The surgeon uses a 0.2cm Kirschner wire to drill holes under the protection of the sleeve. When the Kirschner wire drills into the same length as the length of the screw generated in the preoperative software. Observe the trajectory of the Kirschner wires in the pedicle of the model. If the Kirschner wires are in the pedicle, it is confirmed that the guide template is usable. Record the depth of the Kirschner wires into the pedicle at this time, which is the choice of intraoperative screws (shown in Figure 2).
Surgical approach
Group A
After the patient's general anesthesia was completed, the patient was routinely indwelled with urinary catheterization. First, the patient was placed in a supine position, the neck was hyper-extensive, and the treatment weight was 3KG. Then use the prone position, take a median longitudinal incision on the back of the neck, cut the skin and other subcutaneous tissues in turn to expose the C1 posterior arch and C2 lamina, and use the periosteal device to peel off the suboccipital muscles and the posterior atlantoaxial muscles for periosteal dissection. The lamina and spinous processes are fully exposed with the assistance of the laminar spreader, and the intervertebral and paravertebral soft tissues are fully cleaned. Attach the sterilized 3D guide template to the back of the atlas, and when the matching degree is confirmed and stable, the assistant will help to fix the guide plate, and put a protective sleeve in the guide pin sleeve of the guide plate. The surgeon uses a diameter of 2.0mm. The needle is drilled under the protection of the sleeve, and the depth of drilling refers to the length recorded before and after the simulation operation. After removing the guide plate, the probe looks at the four walls of the pedicle to ensure that the nail path is completely in the pedicle cortex. Then the tap is slowly tapped, Re-measure the depth and select the appropriate length of screw to slowly screw in, and the nail is completed after the position is good under the perspective. The same method is used to insert the screw in the axis. The occipital plate is drilled and fixed, the pedicle screw is fixed with the shaped titanium rod, and the transverse connection is inserted. The ultrasonic bone knife sharpening head is used to polish and implant to treat the completed ilium. After washing, suture layer by layer incision (shown in Figure 3).
Group B
The surgical procedure is basically similar to that of group A, except that during the process of screw implantation, the surgeon performs the screw implantation based on the imaging examination and experience.
Postoperative treatment
(1) underwent cervical collar after fixation, cervical neutral position as far as possible, to avoid over extending through flexion; (2) dexamethasone and intravenous omeprazole in 2-3 days , prevention of surgery Spinal cord edema and stress ulcers caused by the operation, conventional anti-infection, nutritional nerve, analgesic drugs and other supportive treatment; (3) anterior surgery to strengthen oral care, surgical incisions are regularly cleaned and changed dressing, beware of oropharynx and Infection of the incision at the back of the neck; (4) Drainage is routinely placed, and the drainage volume is less than 50ml within 24 hours to remove, to avoid prolonged placement to increase the risk of infection.
Outcome evaluation index
All patients underwent cervical three-dimensional CT after operation, and based on the results of postoperative CT imaging Kawaguch method evaluates the accuracy of screw placement [7]. Grade 0 screws are defined as those without piercing the pedicle, grade 1 screws are defined as piercing the pedicle wall less than 2 mm without complications, and grade 2 screws are defined as piercing the pedicle wall more than 2 mm without complications occurrence, grade 3 screws are defined as the occurrence of related complications. This study classified grade 0 and 1 screws as high-quality screws. JOA (Japanese Orthopaedic Association Scores) score, ASIA score and VAS (Visual Analogue Scale) are commonly used evaluation indicators for evaluating patients after cervical spine surgery.
Statistical analysis
SPSS 20.0 statistical software was used to process the data. T test was used for measurement data, chi square test was used for counting data, P < 0.05 was considered to have statistical difference.