ABSTRACT
<p><b>OBJECTIVE</b>To investigate the skill and evaluate the accuracy for application of guide combined with probing the internal wall of pedicle screw trajectory for subaxial cervical pedicle screw placement.</p><p><b>METHODS</b>Subaxial cervical pedicle screw was inserted in 11 patients by the guide combined with probing the internal wall of pedicle screw trajectory from January 2014 to October 2016, including 7 males and 4 females with an average age of 48.1 years(ranged 32 to 63 years). There were 4 cases with cervical spondylotic myelopathy, 4 with fracture and dislocation of cervical vertebrae, 1 with cervical cord injury without fracture and dislocation, and 2 with atlantoaxialfracture and dislocation. The target pedicle's diameter, optimal entry point, sagittal angle and cross-sectional angle were measured by CT before operation. During operation, the pedicle screw inserted angle was controlled by a guide with a self-designed protractor and probed the internal wall of pedicle screw trajectory as medial safety margin of insertion screw. The accuracy of cervical pedicle screw was evaluated by CT with classification of four grades and assessed whether there was injury of spine cord or vertebral artery postoperatively.</p><p><b>RESULTS</b>Seventy-one cervical pedicle screws were placed among 11 patients, and no one had been found with clinical manifestations of injury of spine cord (or nerve root) or vertebral artery after operation. According to postoperative CT scan for evaluating the grade of screw position, 52 screws were in grade 0, 13 in grade 1, 4 in grade 2, 2 in grade 3, and 91% (65/71) located in good position. In total, 6 screws were incorreted in placement, and 4 cases of them broke medial wall and 2 cases broke lateral wall.</p><p><b>CONCLUSIONS</b>The method of probing the internal wall of pedicle screw trajectory for subaxial cervical pedicle screw placement is safe and reliable, but the studying curve is long. Probing the internal wall of pedicle screw trajectory and controlling the insertion angle by guide with a protractor are key points of this technology.</p>
ABSTRACT
Objective To evaluate the clinical value of multislice spiral CT(MSCT) reconstruction in designing the pedicle screw trajectory before operation in atlantoaxial lesions.Methods 37 patients with upper cervical abnormality treated by surgery for atlantoaxial or occipitoaxial interfixation and/or fusion were undergone MSCT scan,and the 3D anatomical data(including the length,width and height of each pedicle,the angle between the pedicle and sagittal plane,and the thickness of internal occipital crest) were measured on volume reconstruction(VR) and multi-plane reconstruction(MPR) images and used for surgeon to select advisable pedicle screws(including the proper length and diameter) and to ensure the comfortable point,depth and direction for screw position at preoperation.The patients were followed up by atlantoaxial X-ray image and/or MSCT reconstruction to estimate the veracity of the screw position.Results All the patients were operated successfully,of them,5 patients were treated by simply atlantoaxial fixation,15 by atlantoaxial fixation and fusion,4 by simply occipitoaxial fixation,11 by occipitoaxial fixation and fusion,2 by atlantoaxial fixation and occipitoaxial fusion.X-ray images and/or MSCT reconstruction revealed that atlantoaxis were reposition entirely and all the screws were at predesigned trajectory.All the patients were followed up and no screw was broken or loosen and no atlantoaxial redislocation was found.Conclusion MSCT reconstruction for designing pedicle screw trajectory in atlantoaxial lesions before operation is satisfactory and valuable for clinical application.