Pedicle Axis Research Articles

Congenital Absence of Posterior Elements of C2 Vertebra with Atlanto-Axial Dislocation and Basilar Invagination: A Case Report and Review of Literature.

Developmental anomalies of the axis are commonly encountered, especially anomalies involving the odontoid process. Anomalies of the posterior elements are uncommon. We describe a unique case of agenesis of posterior elements of C2 with basilar invagination and atlanto-axial dislocation. An obese 8-year-old boy presented with symptoms of cervical myelopathy. Radiological workup revealed a craniovertebral junction anomaly with occipitalised atlas, absent posterior elements of axis, and hypertrophied C3 spinous process. Atlanto-axial instability and basilar invagination was present. Magnetic resonance angiography revealed hypoplastic left vertebral artery. Traction with cervical tongs failed to improve the alignment and symptoms. Anterior trans-oral release, followed by posterior decompression and custom-made instrumentation, was done. The patient recovered completely and was asymptomatic at the end of two years. X-ray and computed tomography scan demonstrated reduction of basilar invagination and maintenance of alignment. This is the first case to be reported of agenesis of posterior elements of axis associated with basilar invagination. One should look for this condition in patients with hypertrophied spinous process of C3. Utilization of hypoplastic pedicle of axis serves as an additional fixation point to increase the stability of the construct.

The Ipsilateral Adjacent Laminae

A retrospective radiographic analysis and applied anatomical study. The aim of this study was to evaluate the relationships between the ipsilateral lamina/laminae and pedicle axis in the sagittal plane, and the feasibility of free hand pedicle screw placement in subaxial cervical spine without intraoperative fluoroscopic guidance. The morphology of subaxial cervical spine pedicle has been studied extensively. However, to our knowledge, no study has specifically evaluated the relationships between the ipsilateral lamina/laminae and pedicle axis in the sagittal plane on computed tomography (CT) reconstruction images. Axial CT images of 70 adult cases were obtained. Multi-directional pedicle axis reconstruction images of subaxial cervical spines were analyzed. Both the angle formed by the direction of ipsilateral lamina to the pedicle axis in the oblique sagittal plane (lamina-pedicle angle, LPA) and the angle formed by the tangential line passing the ipsilateral adjacent outer laminae cortex to the pedicle axis in the oblique sagittal plane (tangential line pedicle angle, TPA) were recorded. On the basis of the radiographic data, a "T"-shaped guiding tool was designed, and the accuracy of free hand subaxial pedicle screw placement using the guiding tool was evaluated in 12 cadavers. A total of 350 vertebrae were analyzed. Averaged LPA ranged from 72.2 degrees at C3 to 84.2 degrees at C6, averaged TPA ranged from 89.8 degrees at C3 to 90.7 degrees at C6. The TPA showed a high level of consistency close to a right angle. A total of 115 inserted subaxial cervical pedicle screws on 12 cadavers were evaluated. The rate of screw insertion without pedicle wall penetration was 98%, and the rate of pedicle wall penetration of more than 2 mm in the sagittal plane was 0%. The TPA serves to be a reliable guide in determining the direction of subaxial cervical pedicle axis in the sagittal plane. Free hand placement of subaxial pedicle screw is feasible under the guidance of the newly designed guiding tool based on TPA. 5.

Anterior pedicle screw and plate fixation for cervical facet dislocation: case series and technical note

Background ContextThe anterior-only surgical procedure is used as a recommended approach in the treatment of cervical facet dislocations, but an anterior cervical spine implant that offers higher three-column instabilities for stronger fixation is lacking. PurposeThis study aimed to report a new surgical technique of anterior pedicle screw (APS) fixation for cervical facet dislocations and the results of 12 patients with successful application and described safety. Study DesignThe study design includes case series and technical report. Patient SampleThe sample comprises 12 patients with cervical facet dislocations. Outcome MeasuresAnalyses of plain lateral neutral and oblique radiographs and computed tomography scans were conducted to assess reduction, fusion, and the accuracy of pedicle screw placement. Spinal cord compression and decompression was defined by a 1.5-Tesla magnetic resonance imaging. Neurologic status was evaluated according to classification of American Spinal Injury Association (ASIA). MethodsTwelve patients with cervical facet dislocations were surgically treated by the anterior cervical pedicle screw and plate fixation. In these 12 patients (9 male and 3 females), the distribution of spine level was from C3–C4 to C6–C7; the etiologic diagnosis included four unilateral and eight bilateral facet dislocations; the neurologic status comprised four patients with ASIA A, two with ASIA B, two with ASIA D, and four with ASIA E. After discectomy, reduction, and insertion of a peek cage containing autologous bone graft, the APS was inserted along the pedicle axis with the fluoroscope-assisted view imaging. ResultsPostoperatively, all patients had obtained successful reduction and satisfactory anatomic sagittal alignment. There was no complication or instrument failure owing to the use of this technique. Four ASIA A and one ASIA B patients showed no neurologic improvement; one ASIA B patient was improved neurologically to ASIA C; two patients with ASIA D were improved neurologically to ASIA E; no ASIA E patients showed neurologic deterioration. ConclusionsAnterior pedicle screw and plate fixation represents a safe and efficacious but technically challenging option for the treatment of cervical facet dislocations.

Prospective, Self-controlled, Comparative Study of Transposterior Arch Lateral Mass Screw Fixation and Lateral Mass Screw Fixation of the Atlas in the Treatment of Atlantoaxial Instability

A prospective self-controlled study. The aim of the present study was to compare the application and clinical outcomes of transposterior arch lateral mass screw and lateral mass screw fixation of the atlas in the treatment of atlantoaxial instability. Atlas posterior screw fixation techniques comprise transposterior arch lateral mass screw fixation and lateral mass screw fixation. Previous studies have focused mainly on the feasibility of the anatomy and the biomechanics of the methods. From June 2006 to February 2011, 66 patients with atlantoaxial instability were randomly assigned for treatment with transposterior arch lateral mass screw or lateral mass screw fixation of the atlas, combined with axis pedicle screw fixation. Patients were followed up regularly. The operation time, blood loss, intraoperative complications, Japan Department of Orthopedics Association Score, visual analog scale score, and bone fusion rates were recorded. The operation was successful in all 66 cases, with all patients showing improvement in clinical symptoms. There were significant differences in operation time and blood loss between the 2 groups (P<0.001). The mean follow-up time was 49 months. At the final follow-up, the Japan Department of Orthopedics Association score was significantly better than the preoperative score (mean, 13.5; P<0.05). The mean postoperative improvement rate was 88.2% and the mean visual analog scale score was 1.9; both results were significant as compared with preoperative results (P<0.05). Bone fusion was achieved within 6 months after operation. No screw loosening, shifting, breakage, or atlantoaxial instability was observed. Six patients with atlas lateral mass screw placement had burst bleeding of C1-C2 venous plexus during surgery. Five patients had immediate pain and numbness at the occipitocervical region. Atlas transposterior arch lateral mass screw fixation is less invasive, simple, has fewer complications, and offers good fixation results for atlantoaxial instability as compared with lateral mass screw fixation.

The Application of "Renal Pedicle Rotation" Method in Retroperitoneal Laparoscopic Partial Nephrectomy for Renal Ventral Tumors.

To present preliminary experience of "renal pedicle rotation" method in retroperitoneal laparoscopic partial nephrectomy (RLPN) for renal ventral tumors. A retrospective analysis of renal surgery database about patients undergoing RLPN was conducted. We identified 14 consecutive cases of all the surgeries from December 2013 to October 2014 with renal ventral tumors. The 14 surgeries were all in the application of renal pedicle rotation method, an intraoperative skill in which surgeons rotates the kidney on renal pedicle axis after separating renal artery and vein for a better tumor exposure. A total of 14 patients underwent RLPN. All surgeries were successful without conversion to radical nephrectomy or open partial nephrectomy. The mean operative time was 171.1±47.2 min (range 83-246), the mean warm ischemia time was 15.9±9.8 min (range 7-35) and the mean estimated blood loss was 89.3±102.2 mL (range 10-300). Mean postoperative hospital stay was 6.2±1.9 days (range 4-10) and mean retroperitoneal drainage was 4.2±1.4 days (range 2-8). No intraoperative complications occurred. Postoperative complications developed in four patients. All patients had negative margins and pathological examination revealed 10 (71.4%) clear cell carcinomas, two (14.2%) epithelial renal angiomyolipoma, one (7.1%) papillary carcinoma and one (7.1%) nephrotuberculosis. The review of the early oncologic outcomes revealed no local recurrence and distant metastasis. The renal pedicle rotation method might be a feasible and safe procedure to get a better tumor exposure for incision and suture in renal ventral tumors RLPN surgeries with acceptable postoperative outcomes.

Spatial relation study between the compressed spinal cord and the cervical pedicle

To study the relationship between cervical pedicle and compressed spinal cord. One hundred and five patients (53 male,52 female,age from 29 to 80 years) with cervical spondylotic myelopathy who needed surgery were included from December 2011 to January 2013 in Shengjing Hospital. Plain MRI scan was used for cross section of C4 - C7 vertebral bodies parallel to the axis of bilateral pedicle, and the images were sent to the workstation. PACS system was applied to measure the anatomical parameters related to the security of cervical pedicle screw, including the shortest distance from medial left/right cervical pedicle to the cervical spinal cord (LH/RH), and the smallest angle between the longitudinal axis of left/right cervical pedicle and the screw which was assumed to just touch the cervical spinal cord (LSA/RSA). All these data in each segment were classified according to compression or not:with compression and without compression. Twelve cases were selected and measured by MRI and 3D cervical CT for spinal canal width D, namely the straight-line distance between the medial margins of cervical pedicle. And the results of two methods were compared to see whether there were statistical differences. At C4, LH was (7.2±1.3) mm, RH was (6.7±1.4) mm, and the average was (6.9±1.4) mm; at C5, LH was (7.7±1.4) mm, RH was (6.7±1.4) mm, and the average was (7.2±1.5) mm; at C6, LH was (8.2±1.5) mm, RH was (6.9±1.3) mm, and the average was (7.5±1.5) mm; at C7, LH was (8.2±1.4) mm, RH was (7.3±2.1) mm, and the average was (7.7±1.8) mm. At C4, LSA was 34.4°±4.2°, RSA was 34.4°±5.2° and the average angle was 34.4°±4.7°; at C5, LSA was 35.9°±5.2°, RSA was 34.6°±5.4° and the average angle was 35.3°±5.3°; at C6, LSA was 37.4°±4.8°, RSA was 34.8°±4.8° and the average angle was 36.1°±5.0°; at C7, LSA was 39.2°±5.8°, RSA was 37.1°±5.2° and the average angle was 38.1°±5.6°; There were no statistically significant differences between segments with and without compression in H, SA and D (all P>0.05). There is security space between the medial vertebral pedicle and compressed spinal cord. There is individual variation in security space. It is very necessary to identify security space before surgery by MRI, emphasize individual procedure and avoid spinal cord injury.

Lumbosacral pedicle screw placement using a fluoroscopic pedicle axis view and a cannulated tapping device.

BackgroundPedicle screw insertions are commonly used for posterior fixation to treat various spine disorders. However, the misplacement of pedicle screws can lead to disastrous complications. Inaccurate pedicle screw placement is relatively common even when placement is performed under fluoroscopic control. In order to improve the accuracy of the screw placement, we applied a technique using guide wires and a cannulated tapping device with the assistance of a fluoroscopic pedicle axis view.MethodsFrom 2006 to 2011, 854 pedicle screws were placed in 176 patients in lumbosacral spinal fusion surgeries. The accuracy of screw placement was evaluated using postoperative reconstructed computed tomography images. Screw misplacement was classified as minor (cortical perforation <3 mm), moderate (cortical perforation 3–6 mm), or severe (cortical perforation >6 mm). Using logistic regression analysis, we also investigated the potential risk factors associated with screw misplacement.ResultsPedicle screw misplacement was observed in 37 screws (4.3 %) in 34 patients. In the sub-classification analysis, 28 screws (3.3 %) were determined to be minor perforations, 7 screws (0.8 %) were considered to be moderate perforations, and 2 screws (0.2 %) was judged to be a severe perforation (cortical perforation >6 mm). None of the 28 screws that were considered to be minor perforations were associated with any significant symptoms in the patients. However, 2 of the 9 screws that were determined to be moderate or severe perforations caused neurological symptoms (1 of which required revision). No significant differences were observed in the incidence of screw misplacement among the vertebral levels. Significant risk factors for screw misplacement were obesity and degenerative scoliosis. The odds ratios of these significant risk factors were 3.593 (95 % confidence interval (CI), 1.061–12.175) for obesity and 8.893 for degenerative scoliosis (95 % CI, 1.200–76.220).ConclusionsA modified fluoroscopic technique using a pedicle axis view and a cannulated tapping instrument can achieve safe and accurate pedicle screw placement. In addition, obesity and degenerative scoliosis were identified as significant risk factors for screw misplacement.

Modification of Goel–Harms Technique in the Surgical Treatment of Atlantoaxial Subluxation after Grisel Syndrome

Introduction Many etiologies can lead to atlantoaxial subluxation. In Grisel syndrome, this subluxation occurs spontaneously after inflammatory processes of the head and neck. Nonsurgical treatment most often resolves the symptoms; however, in some cases, surgical treatment is necessary to repair the subluxation. Various surgical techniques and instrumentation systems have been used to treat atlantoaxial subluxation, although there is no consensus regarding the best treatment method for the pediatric population. We aim to describe a modified surgical technique for the treatment of atlantoaxial subluxation in a child with Grisel syndrome. Patient and Methods: Our case study involves a 5-year-old female patient with a 6-month history of unresolved Fielding type II atlantoaxial subluxation because of the Grisel syndrome. Despite conservative treatment, the patient's symptoms continued to progress. After two failed closed reduction attempts, open reduction and C1–C2 fusion with a modified Goel–Harms technique was performed with atlas laminar hook and axis pedicle polyaxial screws. A literature review of the surgical treatment of the Grisel syndrome was also performed. Results After surgery, the patient exhibited full clinical and functional recoveries with complete resolution of symptoms. At the 24-month follow-up examination, there was continual evidence of satisfactory reduction and fusion. No complications were observed. On completion of the literature review, seven Grisel syndrome cases were found to have been treated surgically with the minimum patient age being 9 years. Conclusion Conservative management of Grisel syndrome is the most common and effective treatment; however, a few surgical cases have been reported in the literature with good results. We exhibit a safe, new surgical construct for pediatric patients in the treatment of atlantoaxial subluxation and instability, with satisfactory clinical results and solid fusion at 24 months postsurgery.

Anterior transpedicular screw fixation of cervical spine: Is it safe? Morphological feasibility, technical properties, and accuracy of manual insertion.

OBJECT Due to lack of construct stability of the current anterior cervical approaches, supplemental posterior cervical approaches are frequently employed. The use of an anterior-only approach with anterior transpedicular screws (ATPSs) has been proposed as a means of providing 3-column fixation. This study was designed to investigate the feasibility of anterior transpedicular screw (ATPS) fixation of cervical spine, to obtain the morphological measurements for technical prerequisites, and to evaluate the accuracy of the ATPS using fluoroscopy. METHODS The study included both radiological and anatomical investigations. The radiological investigations were based on data from cervical spine CT scans performed in 65 patients. Technical prerequisites of ATPS were calculated using OsiriX for Mac OS. In the anatomical part of the study, 30 pedicles (C3-7) from 6 formalin-preserved cadavers were manually instrumented. Measurements obtained included pedicle width (PW), pedicle height (PH), pedicle transverse angle (PTA), distance of the entry point from the midline (DEPM), and distance of the entry point from the superior endplate (DEPSEP). The authors also analyzed screw position in the manually instrumented vertebrae. RESULTS The mean PW and PH values showed a tendency to increase from C-3 to C-7 in both males and females. The means were significantly larger for both PW and PH in males than in females at all levels (p = 0.001). The overall mean PTA value was significantly lower at C-7 (p < 0.0001). The mean value for the distance of entry point from the midline (DEPM) represented a point at the contralateral side of the pedicle for every level except C-7. The mean DEPSEP values showed significant differences between all levels (p < 0.0001). Seven of the 30 screws were identified as breaching the pedicle (23.3%); these screw malplacements were seen at C-3 (3 screws), C-4 (2 screws), and C-5 (2 screws). CONCLUSIONS The morphological measurements of this study demonstrated that ATPS fixation is feasible in selected cases. They indicate that ATPS insertion using a fluoroscopy-assisted pedicle axis view is safe at the C-6 and C-7 levels, but the results at the other levels did not prove the safety of this technique.

Aneurysmal Bone Cyst of C2, C3 Cervical Spine: A Rare Case Report and Review of Literature

Aneurysmal bone cysts (ABCs) are benign lesions occurring predominantly in metaphysis of long bones. Lesions involving the cervical spine comprise 1% of all spinal ABCs. We report a rare case of C2, C3 ABC in a 39-year-old male patient, who presented with progressive weakness of all four limbs since 8 months. Magnetic resonance imaging (MRI) of spine showed an expansile osteolytic mixed intensity lesion with fluid level involving the body of axis and left pedicle causing significant compression on thecal sac posteriorly suggestive of ABC. Decompression of the cyst along with occipitocervical stabilization with iliac crest bone grafting by combined anterior and posterior approach was done. Histopathological examination revealed trabeculated, dilated vascular beds consistent with the diagnosis of ABC. The patient's neurological status improved immediately after surgery and he continues to do well 6 months postoperatively. Conclusion: Aneurysmal bone cyst of the cervical spine is very rare. It requires thorough neural decompression and 360° fusion for better stability and outcome.

Pedicle axis view combined by sacral mapping can decrease fluoroscopic shot count in percutaneous iliosacral screw placement

BackgroundPercutaneous iliosacral screw fixation of the posterior pelvic ring is a demanding procedure with high exposure to radiation. The conventional technique includes the use of three classical projections with the C-arm: inlet, outlet, and true lateral views. A projection in the axis of the upper sacral alar pedicles with a 30° cephalad and 30° ventral oblique view would help in obtaining a more accurate visualization of the safe corridor. Two subcutaneously placed K-wires, one placed horizontally and one vertically, may facilitate the starting point and aim changes by offering the surgeon an option for exactly matching the position of the sacrum with the image. The purpose of this study was to detect if the radiation application could be decreased by our new methodology. MethodsSeventeen patients with pelvic posterior ring disruptions, in which percutaneous iliosacral screw placement was indicated, were included in the study. Group 1 comprised 7 patients in whom conventional projections and technique were used. Group 2 comprised 10 patients in whom 30°–30° projection and sacral mapping technique via two subcutaneous K-wires were applied. Radiation exposure time, total fluoroscopic shot count, fluoroscopic shot count needed for only guide wire and screw placement, radiation dose, and complications were compared between the two groups. ResultsThe median number of fluoroscopic images for guide and screw placement was 132 (56–220) and 29.5 (19–83) in Groups 1 and 2, respectively, and the difference was statistically significant (p<0.001). The median total fluoroscopic radiation time was 138 (68–234) and 52 (28–77)s in Groups 1 and 2, respectively, and the difference was significant (p<0.001). Group 1 had a significantly higher median radiation dose than Group 2 [3020 (1502–6032) vs. 1192 (426–2359); (p=0.001)]. ConclusionsIliosacral screw placement with the help of sacral mapping and a fourth view, “30°–30°”, helps the surgeon to markedly reduce the fluoroscopic shots, radiation time and dose during guide wire and screw placement. Level of evidenceTherapeutic, Level II.

Anatomic research on atlantoaxial reduction and plate fixation via transoral approach in children

Objective To investigate the feasibility of using transoral anterior reduction plate (TARP) for the atlantoaxial reduction and fixation in pediatric patients.Methods 30 complete sets of cervical CT scan images were obtained from the pediatric patients who had been treated in our department from January 2010 to December 2012.They were 15 boys and 15 girls,with an age range of 5 to 15 years (mean,8.9 ±3.6 years).The children were divided into group A (15 cases,from 5 years old to 9 years old) and group B (15 cases,from 10 years old to 15 years old).The following parameters were measured using tools in the PACS software:transverse and longitudinal diameters,inner and outer heights and width of atlas lateral mass,length of virtual atlas screw path,outward angle of atlas screw,length of axis screw,length of reverse axis pedicle screw,and outward angle of axis reverse pedicle screw.Results The size of lateral mass in both groups could accommodate a 3.5 mm screw.The length of screw path in group A (13.9 ±2.8 mm) was significantly shorter than that in group B (15.9 ± 2.8 mm) (t =2.487,P =0.033).The outward angle of atlas screw in group A (12.4° ± 2.9°) was not significantly different from that in group B (12.0° ± 3.9°) (t =1.546,P =0.136).Group A exhibited a significantly smaller proportion of pedicle width ＞ 3.5 mm [46.7 ％ (7 / 15)],a significantly shorter length of pedicle screw (10.8 ± 2.5 mm) and a significantly shorter length of reverse axis pedicle screw (17.0 ± 2.0 mm) than group B [73.3％ (11/15),11.9 ± 2.7 mm and 20.9 ± 2.3 mm,respectively] (P ＜ 0.05).Conclusions It is basically feasible to use TARP for atlantoaxial reduction and fixation in pediatric patients from 5 to 15 years old,but older children allow for a longer screw path than younger ones.An individualized screw placement is advised when placing screws via transoral approach in pediatric patients. Key words: Children; Anatomy; Atlanto-axial joint; Internal fixators

Comparative Accuracy of Cervical Pedicle Screws Placement using Funnel Technique and Topographic Landmarks Surgical Technique

Introduction The aim of the study is to evaluate accuracy of cervical pedicle screws placement using funnel technique and topographic landmarks surgical technique. Materials and Methods Ten fresh frozen cervical spines (C3-C7) were used (100 pedicles, 20 pedicles per level). The average specimen age was 62.5 years (range, 51-75 years); pedicle width, sagittal angle, and transverse angle were measured on preoperative axial computed tomography (1 mm slices) for every pedicle. All the specimens were randomly divided into two groups. The pedicles (C3-C7) of experimental group were instrumented with 3.5 mm screws with the funnel technique and the control group with the topographic landmarks surgical technique. No intraoperative φλuoroscopy or radiographic control was used during any part of the entire procedure. Critical perforations (documented contact of a screw with, or an injury to, a spinal cord, nerve root, or vertebral artery) and noncritical perforations (a perforation with no critical contact) were recorded. Results In five pedicles (5%), the procedure was aborted because of a small or nonexistent pedicle medullary canal. In Group I (funnel technique), 82% of screws were placed in the pedicle correctly, seven pedicles (18%) had noncritical breaches, and two pedicles (4%) had critical perforations. In Group II (topographic landmarks surgical technique), 62.2% of screws were placed in the pedicle correctly, whereas 11 pedicles (24.4%) had noncritical perforations and 6 pedicles (13.3%) had critical perforations. Statistically significant differences were demonstrated between the two groups ( p&lt;0.05). Conclusion Funnel technique can enhance accuracy and further improving the safety of transpedicular screw placement comparing with topographic landmarks surgical technique. Disclosure of Interest None declared References Abumi K, Itoh H, Taneichi H, Kaneda K. Transpedicular screw fixation for traumatic lesions of the middle and lower cervical spine: description of the techniques and preliminary report. J Spinal Disord 1994;7(1):19–28 Yingsakmonkol W, Karaikovic E, Gaines RW. The accuracy of pedicle screw placement in the thoracic spine using the “Funnel Technique”: part 1. A cadaveric study. J Spinal Disord Tech 2002;15(6):445–449 Abumi K, Shono Y, Ito M, Taneichi H, Kotani Y, Kaneda K. Complications of pedicle screw fixation in reconstructive surgery of the cervical spine. Spine 2000;25(8):962–969 Yukawa Y, Kato F, Ito K, et al. Placement and complications of cervical pedicle screws in 144 cervical trauma patients using pedicle axis view techniques by fluoroscope. Eur Spine J 2009;18(9):1293–1299 Karaikovic EE, Yingsakmongkol W, Gaines RW Jr. Accuracy of cervical pedicle screw placement using the funnel technique. Spine 2001;26(22):2456–2462 Chan CY, Kwan MK, Saw LB. Safety of thoracic pedicle screw application using the funnel technique in Asians: a cadaveric evaluation. Eur Spine J 2010;19(1):78–84 Ludwig SC, Kowalski JM, Edwards CC II, Heller JG. Cervical pedicle screws: comparative accuracy of two insertion techniques. Spine 2000;25(20):2675–2681

Morphological study of subaxial cervical pedicles by using three-dimensional computed tomography reconstruction image.

Malpositioning of cervical screws risks neurovascular injury. A cervical screw fixation system can provide proper rigidity, alignment correction, and high rates of fusion afforded by high pullout biomechanical strength. The objective is to assess the dimensions and axis of the C3–C7 cervical pedicles. A 1-mm slice thickness computed tomography (CT) scan of the cervical spine of 30 patients (15 males, 15 females) were analyzed and reconstructed in three-dimensions using Mimics® 10.01 software. We measured pedicle axis length (PAL), pedicle and lateral mass length (PL-LM), pedicle length (PL), outer pedicle width (OPW), and pedicle transverse angle (PTA) from the axial image and outer pedicle height (OPH) and pedicle sagittal angle (PSA) from the sagittal image. The OPH and OPW at all subaxial cervical spines were suitable for insertion of 3.5 mm cervical pedicle screws. PSA was directed cranially at C3 to C5 (13.84, 7.09, and 2.71) and directed caudally at C6 and C7 (–4.55, –6.94). PTA was greatest at C5 and smallest at C7. The respective difference between the left and right side for nearly all parameters was not statistically significant (except for C6 PL and C7 OPH). Females had a significantly smaller OPH and OPW than males at nearly all levels. The PTA was not significantly different between the sexes. Cervical pedicle screw fixation in the Thai population can be safely performed and guidelines for insertion at each vertebra documented. Appropriate preoperative planning is necessary to achieve safe and accurate placement of the screws.

Morphological character of cervical spine for anterior transpedicular screw fixation

Background:Anterior cervical interbody grafts/cages combined with a plate were frequently used in multilevel discectomies/corpectomies. In order to avoid additional posterior stabilization in patients who undergo anterior reconstructive surgery, an anterior cervical transpedicular screw fixation, which offers higher stability is desirable. We investigated in this study the anatomical (morphologic) characters for cervical anterior transpedicular screw fixation.Materials and Methods:Left pedicle parameters were measured on computed tomography (CT) images based on 36 cervical spine CT scans from healthy subjects. The parameters included outer pedicle width (Distance from lateral to medial pedicle surface in the coronal plane), outer pedicle height (OPH) (Distance from upper to lower pedicle surface in the sagittal plane), maximal pedicle axis length (MPAL), distance transverse insertion point (DIP), distance of the insertion point to the upper end plate (DIUP), pedicle sagittal transverse angle (PSTA) and pedicle transverse angle (PTA) at C3 to C7.Results:The values of outer pedicle width and MPAL in males were larger than in females from C3 to C7. The OPH in males was larger than in females at C3 to C6, but there was no difference at C7. The DIP and PTA were significantly greater in males than in females at C3, but there was no difference in the angle at C4-7. The PSTA was not statistically different between genders at C3, 4, 7, but this value in males was larger than females at C5, 6. The DIUP was significantly greater in males at C3, 4, 6, 7 but was non significant at C5.Conclusions:The placement of cervical anterior transpedicular screws should be individualized for each patient and based on a detailed preoperative planning.

Anterior Transpedicular Screw Technique for Failed Anterior Cervical Internal Fixation in Revision Surgery: a Case Report

Anterior Transpedicular Screw Technique for Failed Anterior Cervical Internal Fixation in Revision Surgery: a Case Report

Feasibility of atlantoaxial pedicle screws’ placement in children 6–8 years of age

The aims of this study were to evaluate the linear and angular dimensions of children's atlantoaxial pedicle using cadavers combined with axial computed tomography (CT) and to examine the feasibility of placing atlantoaxial pedicle screws (3.5 mm diameter) on the vertebrae of children 6-8 years of age. Fourteen cadaveric specimens, ranging in age from 6 to 8 years, were dissected to obtain their atlantoaxial vertebrae. We manually measured 12 linear anatomic parameters related to the atlantoaxial pedicle, its lateral mass, and the posterior arch under the vertebral artery groove. CT axial scanning of the atlantoaxial region was performed on 32 healthy children ranging in age from 6 to 8 years. The length of the atlantoaxial pedicles and the angle between the pedicle axis and the midline of the vertebral body were measured on the atlantoaxial transverse CT imaging. It is feasible to place a 3.5 mm screw in the atlantoaxial pedicle of children ranging in age from 6 to 8 years when the appropriate entry point and trajectory of the screw are chosen.

Morphometric Measurement of Cortical Bone Trajectory for Lumbar Pedicle Screw Insertion Using Computed Tomography

A morphometric measurement of cortical bone trajectory (CBT) for the lumbar pedicle screw insertion using computed tomography (CT). The aim of this study was to conduct a detailed morphometric measurement of the CBT. The CBT is a novel lumbar pedicle screw trajectory, which follows a caudocephalad path sagittally and a laterally directed path in the transverse plane. The advantage associated with this modified technique is increased cortical bone contact, providing an enhanced screw purchase. However, little is known about the possible screw size or detailed direction of the trajectory. The CT scans of 100 adults who underwent examination for spinal problems were studied. A total of 470 lumbar vertebrae excluding spondylosis, malformation, and tumor were observed. In this trajectory, the starting point was supposed to be the junction of the center of the superior articular process and 1 mm inferior to the inferior border of the transverse process. The CT images were analyzed using 3-dimensional reconstruction software. The diameter, length, lateral angle to the vertebral sagittal plane, and cephalad angle to the vertebral horizontal plane of the trajectory were measured. The mean diameter gradually increased from L1 to L5 (from 6.2 mm at L1 to 8.4 mm at L5). The mean length from L1 to L5 were 36.8, 38.2, 39.3, 39.8, and 38.3 mm, respectively. The lateral angle from L1 to L5 were 8.6, 8.5, 9.1, 9.1, and 8.8 degrees, respectively. The cephalad angle from L1 to L5 were 26.2, 25.5, 26.2, 26.0, and 25.8 degrees, respectively. The morphology of the pedicle, such as shape and pedicle axis angle, differed over the lumbar levels, our measurements demonstrated similar data excluding the diameter of the trajectory. There were no significant differences between each level of the lateral and cephalad angles.

Application of reverse axis pedicle screws in the transoral anterior reduction to treat atlas-axis dislocation

Objective To investigate the clinical value of reverse axis pedicle screws in the transoral anterior reduction to treat atlas-axis dislocation.Methods From March 2009 to October 2011,25 patients with atlas-axis dislocation were treated in our department.They were 11 men and 14 women,17 to 65 years of age(mean,39 years).There were 17 traumatic atlas-axis dislocations and 8 atlantoaxial dislocations associated with ossification dens.They underwent transoral release,reduction and instrumentation with transoral atlantoaxial reduction plate (TARP).The atlas was fixated with lateral mass screws and the axis with reverse pedicle screws.After operation,all patients got CT scanning to evaluate screw path,outside tilt angle,downside angle and length of pedicle screw.The Japanese Orthopaedic Association (JOA) scoring system was used for evaluation of spinal function improvement.The atlantodens intervals (ADI) were measured pre-and post-operation to evaluate improvement of dislocation.Results Altogether 50 reverse axis pedicle screws were implanted in the 25 patients.The mean operation time ranged from 125 to 155 minutes and the mean blood loss was 94 mL.CT scan showed 47 screws were in a good trajectory in the axis pedicle.One screw violated into the spinal canal without nerve symptoms due to a too small outside tilt,and 2 screws violated into the vertebral artery foramen which gave rise to occlusion of the cerebellum in one patient who died in the end.The outside tilt angles averaged 20°,the downside angles 15° and the screw lengths 28 mm.The JOA scores increased significantly from 8.9 ± 1.7 pre-operation to 15.7 ± 1.1 (P ＜ 0.05) 3 months after operation.The ADI improved significantly from 8.7 ± 1.5 mm pre-operation to 0.8 ± 0.9 mm post-operation (t =2.937,P ＜ 0.05).Conclusions It is feasible to implant a reverse axis pedicle screw via the transoral approach,but this new technique has a potential risk that should be guarded against so that it should be used carefully in qualified hospitals. Key words: Atlas; Axis; Joint instability; Bone nail

Cervical Pedicle Screw Placement Using the “Key Slot Technique”

A retrospective study. To present the accuracy and safety of a novel "key slot (KS)" technique for cervical pedicle screw (CPS) placement with the learning curve. Safety and learning curve are the issues preventing wide acceptance of CPS. On the basis of the local anatomy of the pedicle, the authors modified the conventional technique to increase the accuracy and comfortableness of CPS placement with minimal bone loss. A total of 277 subaxial CPS in 50 patients had been inserted using author's technique were reviewed. The KS-shaped entry was created on the medial half of the lateral mass with a 3 mm cutting burr. The shape of entry was a right-angled triangle on the axial plane. The apex of triangle was the virtual pedicle inlet and the oblique side was same as pedicle axis. After making entry, the pedicle was probed with a curved awl along the medial wall. On the postoperative vascular-enhanced computed tomography scan, we analyzed the direction and grade of pedicle perforation (grade 0: no perforation, 1:< 25%, 2: 20% to 50%, 3: > 50% of screw diameter) on the chronological group of consecutive 10 cases. Grade 2 and 3 were considered as incorrect position. The correct position was found in 250 screws (90.3%); grade 0 - 215 screws, 1 - 35 screws and the incorrect position in 27 screws (9.7%); grade 2 - 21 screws, grade 3 - 6 screws. The incidence of incorrect screw position was 18% in the initial 20 cases and 2.7% after that. There was no neurovascular complication related with CPS. We performed CPS placement using the KS technique and with 90% correct position without clinical complications. After the learning curve, the incidence was 2.7%. This technique could be considered relatively concrete and safe modification of conventional technique with minimal bone loss.