The Experimental And Clinical Studies On Cervical Pedicle Placement Technique

PartⅠStudy on Anatomic Relation Between the Cervical Pedicle and the Adjacent Neural StructuresObjectives: To determine quantitatively the anatomic relation of the cervical pedicles to the adjacent nerve roots and dural sac and avoid and minimize the complication in performing the technique.Methods: 12 cadavers were used for dissection to observe the relations of the cervical pedicles to the adjacent dural sac and nerve roots. After removal of whole posterior bony elements including the spinous processes, laminas, and lateral masses, the isthmus of the pedicles, the dural sac, and the nerve roots of C3-C7 were exposed. Direct measurements included the distance from the pedicle to the superior and inferior nerve roots and the dura(PDSD,PSRD,PIRD). Also, the pedicle height(PH) and width(PW) were measured at its isthmus.Results: In 12 cadavers, PH Male: 6.23-7.21mm, Female: 5.41-6.93mm. PW Male: 5.33-6.56mm, Female: 4.22-6.07mm. IPD Male: 22.69mm-24.14mm, Female: 22.60- 23.98mm. PDSD Male:0-2.83mm, Female:0-3.19mm. PSRD Male:0-1.67mm, Female: 0-1.60mm. PIRD Male: 1.06-2.69mm, Female: 1.32-2.80mm. REA Male: 75.30- 80.90mm, Female: 74.40-82.30mm.Conclusions: This study suggests that there are some difference in the distance between the cervical pedicle and the adjacent neural structure more frequently. Screw penetrating to the pedicle may be not caused complications. In addition, transpedicular screw placement at C3 must be caution for our female populationPartⅡClinical anatomic study of lower cervical pedicle in a Chinese Population by multiplanar reformations of spiral CTObjective: To evaluate lower Cervical pedicle (C3-C7) dimensions in a Chinese population by multiplanar reformations (MPR) of computed tomography for surgical application of transpedicular screw placement and enhance the accuracy. Methods: The dimensions of the pedicles (C3–C7) were determined in 60 patients with cervical spinal lesions from CT images. Measurements of pedicle height, width, pedicle axis length, effective length, and two angles of the pedicles, the distances from the projection point of the pedicle axis to the lateral edge of the lateral mass and the inferior edge of the superior facet were measured.Results: The outer pedicle width was smaller than the height in most of the pedicles.This measurement was significantly different between male and female patients in outer pedicle width of pedicle (P<0.05; independent samples t test) at C3 and C4. The mean values were ranging from 5.4 to 6.7 mm in male , 4.4 to 6.3 mm in female for outer pedicle width. The distances from the projection point to inferior edge of the superior facet did not show uniform pattern of change from C3 to C7, whereas the distances from the projection point to the lateral edge of the lateral mass consistently increased from cephalad to caudad. There were significant correlations (P<0.01; Kendall's Test) between the vertebral level and both of pedicle angle (pedicle transverse angle and pedicle sagittal angle). The smallest pedicle transverse angle was at C7 in male and female.Conclusions: Transpedicular screw placement for the cervical pedicle of C3, C4 must be cautious in the Chinese female population before the exact pedicle transverse diameters are known. Most of cervical pedicle (C5-C7) in a Chinese Population was suited for pedicle fixation of 3.5mm screw. Taking into consideration some variations between individuals, this data combined with evaluation of results of preoperative computed axial tomography is must before operation.PartⅢThe study of accuracy of screw placement in lower cervical pedicle1. Accuracy of CT-based navitation of pedicle screws implantation in the cervical spine compared with multiplanar reformations (MPR) of CT assisted techniqueObjective: To evaluate the feasibility and accuracy of cervical spine pedicle screw fixation assisted by CT-based navitation system and multiplanar reformations (MPR) of CT.Method: 12 human cadaveric cervical spines were utilized and 3.5mm screws were placed into the C3-C7 pedicles following two kinds of techniques: assisted by multiplanar reformations (MPR) of CT (group 1), assisted by assisted by CT-based navitation system (group 2). Thereafter, cortical integrity of every sample was examined by imaging. Screw position of the pedicle screws was divided into 3 grades: grades 1, correct screw placement without pedicle perforation or with pedicle perforation <1.0 mm (depth of the thread); grades 2, pedicle perforation >1.0 mm without the need for screw revision; and grades 3, pedicle perforation >1.0 mm with the need for screw revision because of irritation or injury of roots or the spinal cord, or because of reduced biomechanical stability.Result: All together, there were 120 pedicles involved. Group 1, 60 pedicles, the average operation time per sample was 152 minutes.90% of the screws were placed entirely within the pedicle, 10% showed non- critical breaches, and no showed critical breaches. Group 2, 60 pedicles, the average operation time was 272 minutes.85% were placed entirely within the pedicle, 11.7% showed non-critical breaches, and 3.3% showed critical breaches. There were statistically significant difference between the two groups with respect to the average operation time(P<0.05). There were no statistically significant difference between the two groups with respect to the accuracy of screw placement(P>0.05).Conclusion: The assisted by CT-based navitation system and multiplanar reformations (MPR) of CT definitely enhance saccuracy. But the assisted by multiplanar reformations (MPR) of CT technique has a shorter operation time than CT-based navitation system. It is an extensive and easy method for pedicle screws implantation in the cervical spine2.The study of evaluation postoperative transpedicular screw of cervical pedicle by multiplanar reformations (MPR) of CTObjective: To evaluate the feasibility and accuracy of postoperative transpedicular screw of cervical assisted by multiplanar reformations (MPR) of CT.Method: 120 postoperative transpedicular screw of cervical spine were evaluated by multiplanar reformations (MPR) of CT and anatomic dissection. Screw position of the pedicle screws was divided into 3 grades. grades 1, correct screw placement without pedicle perforation; grades 2, pedicle perforation≤radius of screw; grades 3, pedicle perforation≤radius of screw.Result: All together, 120 cervical pedicle screws were evaluated. Evaluated by multiplanar reformations (MPR) of CT, 82.5% of the screws were placed entirely within the pedicle, 15.8% showed breaches of expansion, and 1.7% showed critical breaches; Evaluated by anatomic dissection, 80% of the screws were placed entirely within the pedicle, 18.3% showed breaches of expansion, and 1.7% showed critical breaches. There were no statistically significant difference between the two methods of evaluation with respect to the breaches of direction and segment(p=0.058,p=0.208).Conclusion: Postoperative transpedicular screw of cervical spine were evaluated by multiplanar reformations (MPR) of CT is accurate and easy.PartⅣThe application of cervical pedicle screw fixation in clinicalObjective: To evaluate the effects of transpedicular internal fixation system.Method: From December 2004 to December 2007, transpedicular internal fixation system was performed in 23 patients (10 male, 13 female, mean age 46years). Out of them , there were 10 fracture and dislocation of cervical spine ,11 with cervical tumor, 2 with cervical congenital malformation The clinical outcomes were investigated by clinical observations, radiologic studies and statistical analysis. According to American Spinal Injury Association grades: 6 cases were in A grade, 2 cases in B grade,1 cases in C grade,1 cases in D grade. Preoperation the JOA scores of neurofunction in 13 nontraumatic lesions of the cervical spine is 12.9.Result: Cervical pedicle screws were inserted successfully on all cases without complication.The patients were followed up for 4 to 30 months with an average of 11 months. The result of imaging showed that bony fusion was successful in 23 patients at 4-6months. 4 cases with incomplete spinal cord lesions improved on average 1-2 ASIA grade postoperation, 6 cases with complete spinal injury couldn't recover postoperation, but the symptoms of nerve root such as pain, anesthesia relieved in a certain degree. Postoperation the JOA scores of neurofunction in 13 nontraumatic lesions of the cervical spine is 15.2, the excellent and good rate was 56.1%Conclusion: Transpedicular internal fixation system has multiaxial screw of three-column fixation and plastic rods, which offer strong fixtion and good fusion. It can also benefit the maintenance of cervical curve. It is an effective and reliable method for reconstruction of upper cervical stability.