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ABSTRACT: PURPOSE: To present the technique of free-hand subaxial cervical pedicle screw (CPS) placement without using intra-operative navigating devices, and to investigate the crucial factors for safe placement and avoidance of lateral pedicle wall perforation, by measuring and classifying perforations with postoperative computed tomography (CT) scan. The placement of CPS has generally been considered as technically demanding and associated with considerable lateral wall perforation rate. For surgeons without access to navigation systems, experience of safe free-hand technique for subaxial CPS placement is especially valuable. MATERIALS AND METHODS: A total of 214 consecutive traumatic or degenerative patients with 1,024 CPS placement using the free-hand technique were enrolled. In the operative process, the lateral mass surface was decorticated. Then a small curette was used to identify the pedicle entrance by touching the cortical bone of the medial pedicle wall. It was crucial to keep the transverse angle and make appropriate adjustment with guidance of the resistance of the thick medial cortical bone. The hand drill should be redirected once soft tissue breach was palpated by a slim ball-tip prober. With proper trajectory, tapping, repeated palpation, the 26-30 mm screw could be placed. After the procedure, the transverse angle of CPS trajectory was measured, and perforation of the lateral wall was classified by CT scan: grade 1, perforation of pedicle wall by screw placement, with the external edge of screw deviating out of the lateral pedicle wall equal to or less than 2 mm and grade 2, critical perforation of pedicle wall by screw placement, large than 2 mm. RESULTS: A total of 129 screws (12.64 %) were demonstrated as lateral pedicle wall perforation, of which 101 screws (9.86 %) were classified as grade 1, whereas 28 screws (2.73 %) as grade 2. Among the segments involved, C3 showed an obviously higher perforating rate than other (P < 0.05). The difference between the anatomical pedicle transverse angle and the screw trajectory angle was higher in patients of grade 2 perforation than the others. In the 28 screws of grade 2 perforation verified by axial CT, 26 screws had been palpated as abnormal during operation. However, only 19 out of the 101 screws of grade 1 perforation had shown palpation alarming signs during operation. The average follow-up was 36.8 months (range 5-65 months). There was no symptom and sign of neurovascular injuries. Two screws (0.20 %) were broken, and one screw (0.10 %) loosen. CONCLUSION: Placement of screw through a correct trajectory may lead to grade 1 perforation, which suggests transversal expansion and breakage of the thinner lateral cortex, probably caused by mismatching of the diameter of 3.5 mm screws and the tiny cancellous bone cavity of pedicle. Grade 1 perforation is deemed as relatively safe to the vertebral artery. Grade 2 perforation means obvious deviation of the trajectory angle of hand drill, which directly penetrates into the transverse foramen, and the risk of vertebral artery injury (VAI) or development of thrombi caused by the irregular blood flow would be much greater compared to grade 1 perforation. Moreover, there are two crucial maneuvers for increasing accuracy of screw placement: identifying the precise entry point using a curette or hand drill to touch the true entrance of the canal after decortication, and guiding CPS trajectory on axial plane by the resistant of thick medial wall.
Archives of Orthopaedic and Trauma Surgery 04/2013; · 1.37 Impact Factor
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ABSTRACT: PURPOSE: To determine the risk factors of neurologic deficits during PVCR correction, so as to help improve safety during and after surgery. METHODS: A consecutive series of 76 patients with severe and rigid spinal deformities who were treated with PVCR at a single institution between October 2004 and July 2011 were included in our study. Of the 76 patients, 37 were male and 39 female, with an average age of 17.5 years (range 10-48 years). There were 52 adolescent patients (with an age <18 years) and 24 adult patients (with an age ≥18 years). Preoperatively, postoperatively and 6 months after surgery, we performed systemically neurologic function evaluations of each patients through meticulous physical examination. Any new abnormality or deterioration in evaluation of neurologic function than preoperative is reckoned postoperative neurologic deficits. Ten variables that might affect the safety of neurologic deficits during PVCR procedures, including imaging factors, clinical factors and operational factors, were analyzed using univariate analysis. Then the variables with statistical difference were analyzed by using multi-factor unconditional logistic regression analysis. RESULTS: No patient in this series had permanent paraplegia and nerve root injury due to operation. Change of neurologic status was found in six patients after surgery. Results of single-factor comparison demonstrated that the following seven variables were statistically different (P < 0.05): location of apex at main curve (X 3), Cobb angle at the main curve at the coronal plane (X 4), scoliosis associated with thoracic hyperkyphosis (X 5), level of vertebral column resected (X 6), number of segmental vessels ligated (X 7), preexisting neurologic dysfunction (X 8), and associated with intraspinal and brain stem anomalies (X 9). The multi-factor unconditional logistic regression analysis revealed that X 8 (OR = 49.322), X 9 (OR = 18.423), X 5 (OR = 11.883), and X 6 (OR = 8.769) were independent and positively correlated with the neurologic deficit. CONCLUSIONS: Preexisting neurologic dysfunction, associated with intraspinal and brain stem anomalies, scoliosis associated with thoracic hyperkyphosis and level of vertebral column resected are independent risk factors for neurologic deficits during PVCR procedure.
European Spine Journal 04/2013; · 1.97 Impact Factor
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ABSTRACT: Object Phase contrast-cine MRI (PC-cine MRI) studies in patients with syringomyelia and Chiari malformation Type I (CM-I) have demonstrated abnormal CSF flow across the foramen magnum, which can revert to normal after craniocervical decompression with syrinx shrinkage. In order to investigate the mechanisms leading to postoperative syringomyelia shrinkage, the authors studied the hydrodynamic changes of CSF flow in the craniocervical junction and spinal canal in patients with scoliosis associated with syringomyelia after one-stage deformity correction by posterior vertebral column resection. Methods Preoperative and postoperative CSF flow dynamics at the levels of the foramen magnum, C-7, T-7 (or apex), and L-1 were assessed by electrocardiogram-synchronized cardiac-gated PC-cine MRI in 8 adolescent patients suffering from severe scoliosis with syringomyelia and CM-I (scoliosis group) and undergoing posterior vertebral column resection. An additional 8 patients with syringomyelia and CM-I without spinal deformity (syrinx group) and 8 healthy volunteers (control group) were also enrolled. Mean values were obtained for the following parameters: the duration of a CSF cycle, the duration of caudad CSF flow (CSF downflow [DF]) and cephalad CSF flow (CSF upflow [UF]), the ratio of DF duration to CSF cycle duration (DF%), and the ratio of UF duration to CSF cycle duration (UF%). The ratio of the stationary phase (SP) duration to CSF cycle duration was calculated (SP%). The maximum downflow velocities (VDmax) and maximum upflow velocities (VUmax) were measured. SPSS (version 14.0) was used for all statistical analysis. Results Patients in the scoliosis group underwent one-stage posterior vertebral column resection for deformity correction without suboccipital decompression. The mean preoperative coronal Cobb angle was 102.4° (range 76°-138°). The mean postoperative Cobb angle was 41.7° (range 12°-75°), with an average correction rate of 59.3%. During the follow-up, 1 patient with hypermyotonia experienced a significant decrease of muscle tension and 1 patient with reduced anal sphincter tone manifested recovery. A total of 5 patients demonstrated a significant decrease (> 30%) in syrinx size. With respect to changes in CSF flow dynamics, the syrinx group was characterized by slower and shorter downflow than the control group, and the difference was more significant at the foramen magnum and C-7 levels. In patients with scoliosis, CSF downflow at the foramen magnum level was significantly restricted, and a prolonged stationary phase indicated increased obstruction of CSF flow. After posterior vertebral column resection, the peak velocity of CSF flow at the foramen magnum increased, and the downflow phase duration was markedly prolonged. The parameters showed a return to almost normal CSF dynamics at the craniocervical region, and this improvement was maintained for 6-12 months of follow-up. Conclusions There were distinct abnormalities of CSF flow at the craniocervical junction in patients with syringomyelia. Abnormal dynamics of downflow could be aggravated by associated severe spinal deformity and improved by correction via posterior vertebral column resection.
Journal of neurosurgery. Spine 03/2013; · 1.61 Impact Factor
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ABSTRACT: PURPOSE: Severe spinal deformity is a complex morphological deformation that occurs and develops in three-dimensional space combined with abnormal development and morphology of anatomical structures, which presents great difficulties in the process of transpedicular screw placement. This study tried to explore the methods of transpedicular screw placement in surgical correction of severe spinal deformities. METHODS: Surgical corrections through posterior approach were performed in all the 76 cases (mean age 20.4 years). The averaging preoperative Cobb's angle of scoliosis was 108.2° ± 33.6° (range 100°-170°). Among these patients, 34 cases were combined with kyphosis; the average Cobb's angle of kyphosis was 77.3° (range 63°-160°). During operation, the screw tract was first established with the regular free-hand pedicle screw placement method. When this failed, in order to adjust the screw trajectory, a five-step remedial method was performed in the following order: (1) the"funnel" method; (2) exploring the pedicle exterior edge through the costotransverse joint; (3) exploring the superior and inferior edges of pedicle through the nerve root canal; (4) the vertebral plate fenestration; and (5) hemilaminectomy. RESULTS: Among all 1,472 screws planned to be placed for the patients, 1,210 (82.2 %) were successfully placed after using the regular method, and 262 (17.8 %) failed in this stage. After applying the five-step remedial method, 256 of the failed 262 screws were successfully placed. Among them, 176 screws (68.8 %) were successfully placed after Step 1, 44 (17.2 %) after Step 2, 21 (8.2 %) after Step 3, 12 (4.7 %) after Step 4, and 3 (1.2 %) after Step 5. In only six, pedicles screws could not be placed eventually. No nerve or blood vessel damages occurred in all cases. All final screw positions were validated by CT. CONCLUSION: The five-step remedial method proved to be an effective supplementary method for transpedicular screw placement to treat patients with severe spinal deformities. The key points include a detailed preoperative plan, a meticulous hand drilling sensation, and an experienced probing technique for screw tract.
European Spine Journal 10/2012; · 1.97 Impact Factor
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ABSTRACT: Object The surgical treatment of severe and rigid spinal deformities poses difficulties and dangers. In this article, the authors summarize their surgical techniques and evaluate patient outcomes after performing posterior vertebral column resection (PVCR) for the correction of spinal deformities with curves greater than 100°, and investigate the crucial points to ensure neurological safety during this challenging procedure. Methods The authors retrospectively reviewed their experience with 28 patients with extremely severe (Cobb angles in the coronal or sagittal plane > 100°) and rigid thoracic or thoracolumbar spine deformities who underwent PVCR. The average patient age was 20.2 years and all patients underwent a minimum follow-up of 24 months (range 24-60 months). Patients were divided into groups according to their morphological classification as follows: kyphosis alone (Group A, 6 patients with a mean Cobb angle of 109.0° [range 105°-120°]); kyphoscoliosis with coronal plane curves notably greater than sagittal plane curves (Group B, 14 patients with mean scoliotic curves of 116.6° [range 102°-170°] and kyphotic curves of 77.7° [range 42°-160°]); and kyphoscoliosis with sagittal curves notably greater than coronal plane curves (Group C, 8 patients with a mean coronal curve of 85.4° [range 65°-110°] and a mean sagittal curve of 117.6° [range 102°-155°]). Results A total of 36 vertebrae were removed in 28 patients who had a severe rigid spinal deformity, and the mean fusion extent was 13.3 vertebrae (range 7-17 vertebrae). The mean operating time was 620 minutes (range 320-920 minutes) with an average operative blood loss of 6,680 ml (range 3,000-24,000 ml). The overall final correction rate of scoliosis was 59.0%, and average postoperative kyphotic Cobb angles ranged from 30.4° to 95.9°. In Group A the mean preoperative sagittal angle of 109.0° was corrected to a mean postoperative angle of 32.0°. In the Group B kyphoscoliotic patients, the correction rate in the coronal plane was 58.6%; the Cobb angle in the sagittal plane was corrected from a mean of 77.7° preoperatively to 25.1° postoperatively; in Group C, the correction rate in the coronal plane was 58.5%, and the mean sagittal angle was reduced from a mean of 117.6° preoperatively to 39.0°. Of the 28 patients who underwent PVCR, 46 complications were observed in 18 patients intra- and postoperatively. There were 5 neurological complications including 1 case of late-onset paralysis and 4 cases of thoracic nerve root pain, all of which resolved during the early follow-up period. Nonneurological complications occurred more often in kyphoscoliotic patients (41 complications). The mean follow-up of all patients was 33.7 months (range 24-60 months). Conclusions Posterior vertebral column resection was effective in correcting severe rigid spinal deformity, although the procedure was technically demanding, exhaustingly lengthy, and was associated with a variety of complications. The PVCR technique created a space for spinal correction and spinal cord tension adjustment and the correction could be performed under direct inspection and by palpation of the tension in the spinal cord through the space. Therefore, in terms of the spinal cord, the deformity correction process involved in the PVCR procedure is relatively safe.
Journal of neurosurgery. Spine 10/2012; · 1.61 Impact Factor
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ABSTRACT: To investigate the clinical significances of the thoracic pedicle classification determined by inner cortical width of pedicle in posterior vertebral column resection (PVCR) with free hand technique for the treatment of rigid and severe spinal deformities.
Between October 2004 and July 2010, 56 patients with rigid and severe spinal deformities underwent PVCR. A total of 1098 screws were inserted into thoracic pedicles at T(2-12). The inner cortical width of the thoracic pedicle was measured and divided into 4 groups: group 1 (0-1.0 mm), group 2 (1.1-2.0 mm), group 3 (2.1-3.0 mm), and group 4 (> 3.1 mm). The success rate of screw-insertion into the thoracic pedicles was analyzed statistically. A new 3 groups was divided according to the statistical results and the success rate of screw-insertion into the thoracic pedicles was analyzed statistically again. And statistical analysis was performed between different types of thoracic pedicles classification for pedicle morphological method by Lenke.
There were significant differences in the success rate of screw-insertion between the other groups (P < 0.008) except between group 3 and group 4 (chi2 = 2.540, P = 0.111). The success rates of screw-insertion were 35.05% in group 1, 65.34% in group 2, and 88.32% in group 3, showing significant differences among 3 groups (P < 0.017). According to Lenke classification, the success rates of screw-insertion were 82.31% in type A, 83.40% in type B, 80.00% in type C, and 30.28% in type D, showing no significant differences (P > 0.008) among types A, B, and C except between type D and other 3 types (P < 0.008). In the present study, regarding the distribution of different types of thoracic pedicles, types I, II a, and II b thoracic pedicles accounted for 17.67%, 16.03%, and 66.30% of the total thoracic pedicles, respectively. The type I, II a, and II b thoracic pedicles at the concave side accounted for 24.59%, 21.13%, and 54.28%, and at the convex side accounted for 10.75%, 10.93%, and 78.32%, respectively.
A quantification classification standard of thoracic pedicles is presented according to the inner cortical width of the pedicle on CT imaging: type I thoracic pedicle, an absent channel with an inner cortical width of 0-1.0 mm; type II thoracic pedicle, a channel, including type IIa thoracic pedicle with an inner cortical width of 1.1-2.0 mm, and type IIb thoracic pedicle with an inner cortical width more than 2.1 mm. The thoracic pedicle classification method has high prediction accuracy of screw-insertion when PVCR is performed.
Zhongguo xiu fu chong jian wai ke za zhi = Zhongguo xiufu chongjian waike zazhi = Chinese journal of reparative and reconstructive surgery 03/2012; 26(3):257-60.
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ABSTRACT: Posterior vertebral column resection (PVCR) is an effective technique for treating severe rigid spinal deformities, and no other osteotomy is capable for such an excellent corrective effects. The purpose of this study was to discuss the correction mechanisms of PVCR.
Forty-six patients with severe rigid spinal deformities undergoing PVCR were retrospectively analyzed. According to a routine posteroanterior supine entire spine radiograph performed before and after surgery, the major curve at coronal plane was divided into three segments factitiously: upper segment (from the superior endplate of the upper vertebra of the major curve to the inferior endplate of the upper vertebra adjacent to the resected vertebra), middle segment (from the inferior endplate of the upper vertebra adjacent to the resected vertebra to the superior endplate of the lower vertebra of the resected vertebra), and lower segment (from the superior endplate of the lower vertebra of the resected vertebra to the inferior endplate of the lower end vertebra of the major curve). Cobb method was used to measure the curvature of the major curve and each segment. We analyzed the changes of the Cobb angle in the major curve and each segment. We also analyzed the correlation between the placement of pedicle screws and deformity correction.
The Cobb angle of the major curve decreased from 110.1 ± 18.1° to 51.0 ± 17.3° (p < 0.05) after surgery (decreased by 59.1 ± 16.4°), the mean correction rate was 54.1 ± 12.2% (p < 0.05). The Cobb angle of the middle segment decreased by 28.1 ± 14.7° (p < 0.05), the contribution rate was 49.1 ± 27.3%. The upper and lower segments decreased by 15.7 ± 13.1° and 15.3 ± 12.4°, respectively (p < 0.05). There were no significant differences in the contribution rate between upper and lower segments (25.2 ± 16.6% vs. 26.3 ± 22.6%) (p > 0.05). 22 patients were instrumented with at least one pedicle screw in the adjacent upper and lower vertebras of the resected vertebra and gained a better corrective effect in comparison with the others (p < 0.05). The data also indicated that deformity correction was closely related to the numbers of the pedicle screws (r = 0.82, p < 0.05).
In conclusion, the middle segment offered the highest contribution rate to the deformity correction of the major curve, but at the same time the spinal cord was angulated in this segment. So, it is dangerous to gain too much deformity correction in the middle segment. Because spine would shorten and the tension in spinal cord would decrease after vertebral column resection, a better correction effect could be gained in upper and lower segments at a low risk of spinal cord injury. But it was actually too hard for such rigid spinal deformity. It could gain a better corrective effect and stability by placing more pedicle screws at major curve, especially at the upper and lower vertebras adjacent to the resected vertebra, but sometimes it was difficult to place enough pedicle screws in severe rigid spinal deformities.
European Spine Journal 09/2011; 21(4):705-10. · 1.97 Impact Factor
