Objective To explore an ideal screw insertion point and optimal trajectory for anterior axis pedicle screw (AAPS) so as to provide an anatomical basis for AAPS placement.Methods CT scan of the cervical spine was performed for 40 healthy Chinese adults.Then,the CT data were imported into the Mimics software to reconstruct the three-dimensional images of the axes.The data were divided into two groups according to the gender.The following data were measured:pedicle centerline minimal diameter on both left and right sides,pedicle axial length,the distance between entrance point and upper endplate,the distance between entrance point and median sagittal plane,the distance between entrance point and peak of crista lambdoidalis of C2 vertebral body,extraversion angle and sagittal angle.The screw fixation parameters for AAPS were measured using the Mimics software.Results There was no statistical difference between the left and right sides as well as between the genders (P ＞ 0.05).The entrance point for insertion of AAPS was recommended to be on (4.39 ± 0.67) mm from the upper endplate,and on (3.95 ± 0.44) mm from the median sagittal plane.The ideal pedicle axial length was (34.15 ± 2.93) mm,and the pedicle centerline minimal diameter was (7.04 ± 0.87) mm.The distance between the entrance point and the peak of crista lambdoidalis of C2 vertebral body was (1.45 ± 0.19) mm.The ideal extraversion angle was (30.80 ± 2.79) °,and the ideal sagittal angle was (36.35 ± 3.26) ° . Conclusion The ideal insertion pathway of AAPS placement can avoid spinal canal,foramen intervertebrale and other important anatomical structure,which is feasible in regard of anatomy.The insertion point can refer to the peak of crista lambdoidalis of C2 vertebral body.However,AAPS placement should be individualized in term of its anatomy variability.

Objective To investigate the clinical outcomes of pedicle screw fixation assisted with the 3D printing positioning guide template for treatment of unstable atlas fractures.Methods A retrospective case series review was made on 10 patients with unstable atlas fractures undergone direct posterior C1 pedicle screw fixation assisted with the 3D printing drill guide template from September 2012 to May 2015.There were 7 males and 3 females,with a mean age of 52.6 years (range,23-75 years).All patients complained of neck pain,stiffness and decreased range of motion without neurologic deficit.Preoperative skull traction was used routinely.After the three-dimension reconstruction of cervical vertebrae,ideal trajectory for C1 pedicle screws was designed with a complementary basal template for posterior surface of atlas corresponding anatomical structure.Then the drill guide template was materialized in a rapid prototyping machine and used during operation.Start point and direction of the ideal and actual trajectories were measured after matching the position of the pre-and post-operative patients' cervical spine.Safety of pedicle screw fixation was assessed in the transverse and sagittal planes of CT scan.Operation time and blood loss were recorded.Visual Analogue Scale (VAS) of neck pain was recorded before operation and 3 months after operation.Clinical efficacy,fracture reduction,stability and surgical complications were reviewed at the follow-up.Results A total of 20 screws were inserted safely.No significant differences existed in deviation of entry point and direction between ideal and actual trajectories (P ＞0.05).Operation time was 60-90 min (mean,75 min) and intraoperative blood loss was 110-300 ml (mean,160 ml).No spinal cord or vertebral artery injury was noted during operation.All patients were followed up for 12-36 months (mean,20.5 months).VAS was improved from preoperative 7.3 (6.3-9.5) points to 1.4 (0.3-2.5) points 3 months after operation (P ＜ 0.05).All patients had normal range of motion of the cervical spine 3 months after operation.Bony fusion was achieved 6 months after operation.At the follow-up,good cervical alignment was maintained with no instrument failure and C1.2 instability.Conclusion For treatment of unstable atlas fractures,direct posterior C1 pedicle screw fixation assisted with the 3D printing drill guide template can improve the precision of screw placement,reduce complications,and preserve the function of the occipital-atlantoaxial junction.

Objective To determine the treatment options for teardrop fracture of the axis and discuss the treatment efficacy.Methods Nineteen patients with teardrop fracture of the axis treated from March 2003 to June 2013 were retrospectively reviewed.Teardrop fracture of the axis accounted for 3.9％ of the cervical injuries and 11.4％ of the axis fractures over the same period.There were 15 males and 4 females,at age range of 21-56 years (mean,37.8 years).Injury was caused by traffic accidents in 12 patients,falls in 6,and hit from heavy objects in 1.Cervical imaging examinations (X-ray,CT and MRI) were performed on admission.Thirteen patients were immobilized for 3 to 6 months with the Halovest device,and six patients underwent anterior cervical surgery.No patients had neurologic deficit [American Spinal Injury Association (ASIA) grade E].Visual analogue scale (VAS),implant failure and bone fusion were recorded after operation.Results All patients were followed up for 12-18 months (mean,15.6 months).At the final follow-up,no implant loosening or breakage happened and 18 patients achieved bone union.Neck mobility returned to normal,which showed VAS improved from (7.5 ± 1.2) points to (3.1 ± 1.5) points.ASIA grade E remained in 18 patients,and one patient were progressed to grade D.Conclusions Teardrop fracture of the axis is rare cervical injury,and can be treated conservatively in most cases.However,surgery is often necessary when imaging findings suggest the existence of instability.

Objective To compare the clinical efficacy and fusion rate of unilateral and bilateral C1 and C2 pedicle screw fixation of unstable Jefferson fractures.Methods This retrospective casecontrol study enrolled 22 patients with unstable Jefferson fractures admitted between April 2012 and May 2015.There were 18 males and four females,with the mean age of 52.9 years (range,35-67 years).Mean preoperative visual analogue scale (VAS) was 6.09 points (range,4-8 points).According to the American spinal injury association (ASIA) classification,two patients were rated grade D and one patient grade C.Mean Japanese orthopedic association (JOA) score was 12.3 points.Bilateral C1 and C2 pedicle screw fixation was performed for 15 patients (bilateral group).Advantage side unilateral C1 and C2 pedicle screw fixation was performed for seven patients with extremely unstable fracture or narrow pedicle (unilateral group).Operation time,blood loss and surgical complications were recorded.VAS was used to evaluate the improvement of neck pain after operation.ASIA classification and JOA score were used to assess nerve function recovery.Atlanto-dental interval (ADI),srew position and bone fusion were evaluated after operation.Results All patients successfully completed the operation.Operation time was (119.5 ±21.2)min,and blood loss was (280.1 ±83.1)ml.A total of 74 screws were placed and CT scan showed satisfactory position of the screws.No complications were noted either during the operation or after surgery.All patients were followed up for mean 20.7 months (range,13-33 months).VAS was improved in both groups after operation (P ＜ 0.01),and there was no significant difference between the two groups (P ＞ 0.05).Two patients with ASIA grade D in bilateral group were improved to ASIA grade E after operation.One patient with ASIA grade C in unilateral group was improved to ASIA grade D after operation.JOA score increased to mean 15.7 points at last follow-up.ADI were decreased in both groups after operation(P ＜0.05),but there was no significant difference between the two groups (P ＞ 0.05).All patients had bony fusion 6 months after operation,with similar fusion rate between the two groups (P ＞ 0.05).Conclusion Advantage side unilateral screw fixation can be used for the patients with bilateral C1 and C2 pedicle screw fixation failure,for the technique can improve cervical pain and provide relatively high stability and fusion rate.

Objective To compare the clinical effects of posterior pedicle screw fixation combined with anterior monosegmental or bisegmental fusion reconstruction in patients with unstable Denis type B thoracolumbar burst fractures.Methods A retrospective case-control analysis was made on 62 cases of Denis type B thoracolumbar burst fractures treated from June 2010 to June 2014.There were 51 males and 11 females,aged 19-55 years (mean,35.1 years).The injury causes included fall from height in 32 cases,traffic accidents in 24,hit by heavy objects in 6.Fifty cases were with monosegmental burst fractures,and 12 with monosegmental burst fractures combined with other vertebral compressive fractures.The burst fracture levels were at T~in 8 cases,T12in 20,L1 in 24,L2 in 6,and L3 in 4.According to the different surgical methods,the patients were divided into two groups:Group A (n =30,treated with posterior pedicle screw fixation combined with anterior monosegmental fusion reconstruction) and Group B (n =30,treated with posterior pedicle screw fixation combined with anterior bisegmental fusion construction).The operation time and intraoperative blood loss were compared between the two groups.Visual analogue scale (VAS),Oswestry disability index (ODI),and Frankel scale of neurologic function were compared at last follow-up.The changes of anterior height of fracture vertebrae and Cobb angle of the two groups were also compared preoperatively,postoperatively and at last follow-up.Implant looseness and breakage,titanium mesh tilt,and bone fusion were recorded postoperatively.Results All patients were followed up for 18-24 months (mean,20.8 months).The operation time and blood loss in Group A was (208.2 ± 15.6) min and (598.3 ± 55.3) ml,respectively.The operative time and blood loss in Group B was (260.1 ± 17.4)min and (662.2± 58.3)ml,respectively.There were significantly statistical differences between two groups in operation time and blood loss (P ＜0.05).There were no statistical differences between two groups in terms of Cobb angle restoration and fracture height restoration rate after surgery,Cobb angle loss and fracture vertebral body front height loss rate at final follow-up (P ＞ 0.05).At the final follow-up,VAS in Group A was (2.5 ± 0.8) points,less than (3.2 ± 1.1) points in Group B (P ＜ 0.05);ODI in Group A was (20.3 ± 5.8) points,less than (28.2 ± 5.1) points in Group B (P ＜ 0.05).Frankel scale was improved to some degree after operation (P ＜ 0.05).One case did not achieve bone fusion in Group A versus three cases in Group B (P＜0.05).No implant Loosening,titanium mesh tilt or settlement was found in Group A,while there were eight cases of titanium mesh tilt or settlement in Group B (P ＜0.05).Conclusions For unstable Denis type B thoracolumbar burst fractures,posterior pedicular fixation combined with anterior monosegmental fusion or bisegmental fusion can achieve equal clinical effects.However,posterior pedicular fixation combined with anterior monosegmental fusion can have less injury,higher bone fusion rate,better function restoration,and less incidence of complication.

Objective To investigate the clinical efficacy of posterior lumbar interbody fusion and internal fixation for the treatment of lumbar spinal stenosis with redundant nerve roots (RNRs).Methods A retrospective case series study was performed on the clinical data of 23 cases of lumbar spinal stenosis with RNRs from January 2009 to December 2014.This study involved 10 males and 13 females,with an average age of 48.4 years(range,38-58 years).The course of disease averaged 28.1 months(range,2 months-7 years).There were seven patients with single segment of stenosis,12 patients with two segments of stenosis,and four patients with three segments of stenosis.RNRs diagnostic criteria:in the sagittal section of the MRIT2 image of lumbar spine,the cauda equina nerve root in the dural sac was circular,tortuous and twining.MRI information was collected and analyzed by three double-blind radiologists,respectively.RNRs were determined based on the unanimous consent of all the three doctors.All patients underwent posterior discectomy,spinal canal decompression,interbody fusion,and internal fixation after admission.The operation time,intraoperative blood loss,and postoperative complications were recorded.The visual analogue scale (VAS),Oswestry disability index (ODI),and Japanese Orthopedic Association (JOA) score were used to evaluate the back pain and leg pain before operation and 3 months after operation.Fischgrund standard was used for the overall efficacy evaluation.Results All patients were followed up for 12-30 months (mean,23.3 months).The operation time was (130.0 ± 23.2) minutes,and the intraoperative blood loss was (513.0 ± 165.0) ml.MRI was reviewed 1 week after operation,and the result showed that redundancy of cauda equina disappeared.Preoperatively,the scores of back pain VAS,leg pain VAS,ODI and JOA were (6.3± 0.8) points,(6.8 ±0.9)points,(46.7±2.5)points and (10.3 ±2.8)points,respectively.At 3 months postoperatively,the scores were (1.4 ± 0.5) points,(1.8 ± 0.7) points,(11.9 ± 2.1) points,and (25.3 ± 1.8) points,respectively (P ＜ 0.05).In terms of the efficacy,17 cases were excellent,four good,and two fair,with an excellent and good rate of 91％.At 12 months after operation,the CT scan showed no screw rupture or cage dislocation,with bony union seen between the vertebrae.Conclusion Posterior lumbar interbody fusion and internal fixation can help relieve the back and leg pain and eliminate redundant nerve roots in patients with lumbar spinal stenosis with RNRs.

Objective:To evaluate the medium and long-term clinical efficacy of the treatment of lumbar degenerative diseases in Dynesys dynamic internal fixation combined with decompression.Methods:From March 2008 to March 2015, 145 patients (84 males and 61 females, mean age 55.9±7.1 years old) with symptoms of lumbar degenerative diseases (69 lumbar disc herniation, 53 lumbar spinal stenosis and 23 I grade lumbar degenerative spondylolisthesis) were treated by the lumbar discectomy using Dynesys dynamic internal fixation combined with decompression. The clinical symptoms before and after surgery were assessed by visual analogue scale (VAS), Japanese Orthopaedic Association (JOA) and Oswestry disability index (ODI). Lumbar lateral radiographs were used to measure the height of intervertebral space between the surgical segment and the adjacent segment. The range of motion (ROM) between the surgical segment and the adjacent segment was measured by lumbar dynamic position X-ray. Surgical and adjacent segments degenerative were classified according to the Pfirrmann grade classification.Results:The VAS score, ODI and JOA score of lower back and lower limbs in patients with lumbar disc herniation were improved from 6.6±1.7, 7.1±1.4, 63.1%±10.2%, 12.5±2.4 preoperatively to 2.6±1.0, 2.8±0.9, 30.9%±9.8%, 22.4±2.1 at the latest follow-up. The differences were statistically significant. The VAS score, ODI score and JOA score of lower back and lower limbs in patients with lumbar spinal stenosis were improved from 6.3±2.2, 6.9±1.3, 63.4%±8.5%, 12.8±2.7 preoperatively to 2.4±1.2, 2.8±1.0, 35.1%±12.0%, 22.2±2.2 at the latest follow-up. The differences were statistically significant. The VAS score, ODI score and JOA score of lower back and lower limbs in patients with I degree lumbar degenerative spondylolisthesis were improved from 5.7±2.3, 6.7±0.9, 65.7%±10.0%, 12.5±2.7 preoperatively to 2.2±1.2, 2.7±1.1, 37.0%±11.8%, 22.4±2.6 at the latest follow-up. The differences were statistically significant. Comparing to preoperational value, the height of the operative segment and caudal intervertebral space were decreased at the 1 year postoperatively and last follow-up. But the difference was not significant. As for cranial adjacent segment, the height of intervertebral space preoperatively was decreased from 12.1±1.9 mm preoperatively to 11.7±1.6 mm at 1 year postoperatively, and to 11.3±1.8 mm at the latest follow-up. The difference between them was statistically significant ( F=6.46, P=0.001). The ROM of surgical segments was decreased from 7.6°±2.2° preoperatively to 5.5°±1.6° at 1 year postoperatively, and to 2.9°±1.4° at the latest follow-up. The difference between them was statistically significant ( F=267.9, P<0.001). Conversely, the ROM of cranial and caudal segments was increased from 8.2°±2.4°, 6.5°±1.6° preoperatively to 9.1°±2.1°, 7.1°±1.9° at 1 year postoperatively, and to 10.6°±2.5°, 7.2°±1.8° at the latest follow-up. The difference between them was statistically significant ( F=38.66, 3.81, P<0.001, 0.023). At the latest follow-up, 120 (51.9%) adjacent segments were to be defined adjacent segment degeneration which includes 103 radiological adjacent segment degeneration and 17 symptomatic adjacent segment degenerations. Conclusion:Dynesys dynamic internal fixation combined with decompression could achieve satisfying mid- and long-term therapeutic effect in the treatment of lumbar degenerative diseases. The ROM of surgical segments decreased with time, although part of the ROM was still retained at the latest follow-up. However, it does not seem to avoid the degeneration of adjacent segment.

Objective:To evaluate the feasibility of C 2 laminar screw fixation with double holes, and to explore a new method to judge the safe position of screws during operation. Methods:There were 22 axial specimens, 11 males and 11 females, aged from 26-69 years (mean 47.2 years). The Dicom format of Cervical spine specimens were obtained by CT scanning. It was transferred into the Mimics software for reconstructing the three-dimensional cervical spine model. The central horizontal plane of the axial lamina was cut off as the measuring plane by using the segmentation function. The cortical bone of the start and end lamina was removed naming hole 1 and 2. The distances of D1 and D2 are measured at the trajectory positions of maximum safe ventral inclination, parallel, or maximum safe dorsal inclination, with each entry point (A, M, P). A paired comparison was performed for each group.Results:Forty-four groups of parallel, introversion and extroversion screw path parameters were obtained from 22 axial specimens, and there was no significant difference between the left D1 and D2 groups in each group A, M, P [group A: 3.72±0.95 mm, 3.37±1.24 mm; group M: 2.29±0.72 mm, 1.94±0.58 mm; group P: 1.17±0.44 mm, 0.86±0.69 mm] ( t=1.051, 1.776, 1.777; P>0.05), while the right D1 and D2 had statistical significance[group A: 4.44±1.20 mm, 3.36±1.37 mm; group M: 3.01±0.76 mm, 1.97±0.90 mm; group P: 2.06±0.73 mm, 1.00±0.87 mm]( t=2.781, 4.141, 4.378; P<0.05). In introversion, there was no significant difference in left D1 and D2 in group M [3.11±0.92 mm, 3.79±1.36 mm] ( t=1.942, P=0.058), and was no significant difference in right D1 and D2 in group M [3.79±1.20 mm, 3.69±1.55 mm] ( t=0.239, P=0.812). In group P, the left D1 and D2 were compared, and the results had statistically differences [2.67±0.77 mm, 4.25±1.39 mm] ( t=4.644, P=0.000). In group P, the right D1 and D2 were compared, and the results were statistically different [2.57±1.14 mm, 3.94±1.53 mm] ( t=3.368, P=0.001). In extroversion, the left D1 and D2 in group A and M were compared, and the results had statistically differences [group A: 3.44±1.05 mm, 1.22±0.71 mm; group M: 2.26±0.73 mm, 0.90±0.75 mm] ( t=8.215, 6.095; P<0.05); the results of group A and group M were statistically different between groups of D1 and D2 on the right side[group A: 4.56±1.51 mm, 1.48±0.97 mm; group M: 2.96±1.12 mm, 1.06±0.75 mm] ( t=8.049, 6.611; P<0.05). Conclusion:The double hole screw technique of the C 2 lamina can judge the safe position of the screw in the operation without additional fluoroscopy.