经皮植入椎弓根螺钉的CT扫描钉道分析和临床评价

目的：通过应用经皮穿刺植入椎弓根螺钉的后路固定系统治疗胸腰段骨折患者，以探究该微创技术的准确性和可行性。方法：应用菲力浦X线荧屏透视，经皮穿刺植入导针引导的空心椎弓根螺钉136枚，后路固定系统治疗胸腰段骨折34例。术后CT扫描观察钉道与椎弓根内侧壁、外侧壁的关系，钉尖与椎体前缘的距离、TSA角、SSA角，以及进行术后的初步临床疗效观察。结果：其中椎弓根内侧壁破裂4枚，椎弓根外侧壁破裂3枚，经皮椎弓根螺钉方向过于向头端偏斜2枚，过于向尾端偏斜1枚，经皮椎弓根螺钉钉尖稍穿透椎体前缘5枚，本组经皮椎弓根螺钉植钉失误率7．25％。结论：该技术具有一定的准确性和可行性，并发症发生率相对可以接受，但有较高操作要求，需要有经验的脊柱外科医生进行。本组病例在X线荧屏透视下完成，受辐射量大，后来植钉时透视次数明显减少，患者和医师受辐射量下降而且手术时间缩短，如结合导航技术将在微创脊柱外科领域中发挥相当作用。     

Anatomic evaluation of two different techniques for the percutaneous insertion of pedicle screws in the lumbar spine.

STUDY DESIGN: An in vitro study in which a human cadaver model was used to examine the accuracy of two different techniques of percutaneous pedicle screw insertion in the lumbar spine. OBJECTIVES: To investigate the in vitro misplacement rate of pedicle screw insertion for two different percutaneous techniques: 1) the well established Magerl technique, and 2) a new modified technique. SUMMARY OF BACKGROUND DATA: Numerous anatomic and biomechanical studies have been conducted to analyze the in vitro and in vivo characteristics of pedicle screw insertion in the lumbar spine via an open approach, whereas there is a lack of experimental data concerning the more sophisticated percutaneous procedure. METHODS: Thirty human specimens from L1 to S1 were separated into two groups (A and B). In group A, the screws were placed in accordance with the technique described by Magerl; in group B, a new modified technique developed by the authors' research group was used. After screw placement, the specimens were dissected, and pedicle violations were noted with respect to the degree and direction of the screw misplacement. RESULTS: The dissection of the specimens showed that of 360 pedicle screws, 37 were misplaced. This finding translates into an overall misplacement rate of 10%. With the Magerl technique, 23 pedicle violations (misplacement rate, 13%) were found; with the modified technique, only 14 dislocated pedicle screws (misplacement rate, 8%) were detected. This difference was not statistically significant (P = 0.118). In both groups, there were significantly more medical pedicle violations than lateral (32 medial and 5 lateral screw dislocations). The degree of the screw misplacements varied between 1.0 and 5.0 mm. The majority of pedicle violations (30 of 37) were minor, i.e., less than 3.0 mm. CONCLUSIONS: This in vitro study showed that the percutaneous technique of pedicle screw insertion in the lumbar spine is a safe and reliable procedure. Compared with the well-established Magerl technique, the new modified technique did not decrease the misplacement rate significantly, although less pedicle violations were found in the upper lumbar spine.     

Computer tomography assessment of pedicle screw insertion in percutaneous posterior transpedicular stabilization

Percutaneous insertion of cannulated pedicle screws has been recently developed as a minimally invasive alternative to the open technique during instrumented fusion procedures. Given the reported rate of screw misplacement using open techniques (up to 40%), we considered it important to analyze possible side effects of this new technique. Placement of 60 pedicle screws in 15 consecutive patients undergoing lumbar or lumbosacral fusion, mainly for spondylolisthesis, were analyzed. Axial, coronal, and sagittal reformatted computer tomography images were examined by three observers. Individual and consensus interpretation was obtained for each screw position. Along with frank penetration, we also looked at cortical encroachment of the pedicular wall by the screw. Thirteen percent of the patients (2/15) had severe frank penetration from the screws, while 80% of them (12/15) had some perforation. On axial images the incidence of severe frank pedicle penetration was 3.3% while the overall rate of screw perforation was 23%. In coronal images the overall screw perforation rate rose to 30% while the rate of severe frank pedicle penetration remained unchanged. One patient (6.6%) suffered S1 root symptoms due to a frankly medially misplaced screw, requiring re-operation. This study has shown that percutaneous insertion of cannulated pedicle screws in the lumbar spine is an acceptable procedure. The overall rate of perforation in axial images is below the higher rates reported in the literature but does remain important. Frank penetration of the pedicle was nevertheless low. It remains a demanding technique and has to be performed with extreme care to detail.     

C臂机导航下经皮椎弓根钉内固定联合对侧微创TLIF治疗腰椎管狭窄症

目的 探讨导航辅助下经皮椎弓根钉内固定,联合对侧微创经椎间孔椎体间融合术(Transforaminal Lumbar Interbody Fusion,TLIF),治疗腰椎管狭窄症的临床应用.方法 2010年6月至2012年6月,对47例腰椎管狭窄症患者行导航下经皮椎弓根钉内固定,联合对侧微创TLIF术治疗,观察手术时间、出血量以及手术前后的VAS和ODI评分,并将经皮钉侧和开放置钉侧进行配伍对照比较.结果 平均出血量为(420±45) mL;术前VAS评分为(6.85±1.03),术后1月VAS评分为(1.88±0.79);术前ODI评分为(31.6±3.05),术后1月ODI评分为(43.1±3.23).配伍对照研究结果显示,经皮钉组A级101枚、B级9枚、C级2枚,开放置钉组A级86枚、B级21枚、C级4枚、D级1枚.经皮钉组平均置钉时间为(11.25±4.33) min,透视次数为(2.73±0.42)次,开放置钉组平均置钉时间为(15.43±5.65) min,透视次数为(4.12±0.85)次.差异均有统计学意义.结论 导航辅助下经皮椎弓根钉内固定,联合对侧微创TLIF治疗腰椎管狭窄症疗,效果显著,导航辅助下经皮钉组置钉术的准确度优于开放置钉组,透视次数和置钉时间均少于开放组.     

Inserting pedicle screws in the upper thoracic spine without the use of fluoroscopy or image guidance. Is it safe?

Several studies have looked at accuracy of thoracic pedicle screw placement using fluoroscopy, image guidance, and anatomical landmarks. To our knowledge the upper thoracic spine (T1–T6) has not been specifically studied in the context of screw insertion and placement accuracy without the use of either image guidance or fluoroscopy. Our objective was to study the accuracy of upper thoracic screw placement without the use of fluoroscopy or image guidance, and report on implant related complications. A single surgeon inserted 60 screws in 13 consecutive non-scoliotic spine patients. These were the first 60 screws placed in the high thoracic spine in our institution. The most common diagnosis in our patient population was trauma. All screws were inserted using a modified Roy-Camille technique. Post-operative axial computed tomography (CT) images were obtained for each patient and analyzed by an independent senior radiologist for placement accuracy. Implant related complications were prospectively noted. No pedicle screw misplacement was found in 61.5% of the patients. In the remaining 38.5% of patients some misplacements were noted. Fifty-three screws out of the total 60 implanted were placed correctly within all the pedicle margins. The overall pedicle screw placement accuracy was 88.3% using our modified Roy-Camille technique. Five medial and two lateral violations were noted in the seven misplaced screws. One of the seven misplaced screws was considered to be questionable in terms of pedicle perforation. No implant related complications were noted. We found that inserting pedicle screws in the upper thoracic spine based solely on anatomical landmarks was safe with an accuracy comparable to that of published studies using image-guided navigation at the thoracic level.     

Primary stability of pedicle screws depends on the screw positioning and alignment

Background contextThere is no universal consensus regarding the biomechanical aspects and relevance on the primary stability of misplaced pedicle screws.PurposeThe study is aimed to the determination of the correlation between axial pullout forces of pedicle screws with the possible screw misplacement, including mild and severe cortical violations.MethodsEighty-eight monoaxial pedicle screws were implanted into 44 porcine lumbar vertebral bodies, paying attention on trying to obtain a wide range of placement accuracy. After screw implantation, all specimens underwent a spiral computed tomography scan, and the screw placements were graded following the scales of Laine et al. and Abul Kasim et al. Axial pullout tests were then performed on a servohydraulic material testing system.ResultsDecreasing pullout forces were determined for screws implanted with increasing cortical violation. A smaller influence of cortical violations in the medial direction with respect to the lateral direction was observed. Screws implanted with a large cortical violation and misplacement in the craniocaudal direction were found to be significantly less stable than screws having comparable cortical violation but in a centered sagittal position.ConclusionsThese results provide adjunctive criteria to evaluate more accurately the fate of a spine instrumentation. Particular care should be placed in the screw evaluation regarding the craniocaudal positioning and alignment.     

Accuracy of pedicle screw placement for upper and middle thoracic pathologies without coronal plane spinal deformity using conventional methods

There is a growing interest in the implantation of pedicle screws into the middle and upper thoracic spine. However, usage of the technique is still under debate for these levels because the pedicles in these regions are small and exhibit a high degree of inter- and intraspecimen variability. Twenty-four consecutive patients treated for upper and middle thoracic pathologies by pedicle screw instrumentation under biplanar or uniplanar fluoroscopy were evaluated retrospectively. The rate of screw misplacement on postoperative computerized tomography and complications caused by misplaced screws were determined. In 24 cases, a total of 113 upper-middle thoracic pedicle screws were inserted. Fifty-one of them were inserted between T2 and T5 with guidance of biplanar fluoroscopy, and 62 were inserted between T6 and T8 with uniplanar fluoroscopy. The rate of misplacement was 20.3% for 113 screws (27.4% for T2 to T5 screws, and 14.5% for 62 T6 to T8 screws). Four screws were incorrectly inserted which could have clinical significance (3.5%), and 1 of them required revision. The difference between the upper and middle thoracic screws was not statistically significant (P=0.089). Screw insertion with laminectomy did not cause significant difference in both upper and middle thoracic regions. Only 2 complications were seen because of screw insertion. Pedicle screw insertion with guidance of fluoroscopy may be a reliable and safe method for upper and middle thoracic pathologies.     

Open versus endoscopic lumbar pedicle screw fixation and posterolateral fusion in a sheep model: a feasibility study.

BACKGROUND CONTEXT: Conventional open procedures for lumbar pedicle screw instrumentation are often associated with significant morbidity resulting in longer postoperative recovery and hence have led to the advent of less invasive techniques of spinal instrumentation and fusion. PURPOSE: This study compares lumbar pedicle screw fixation and posterolateral fusion using endoscopic and open techniques in a sheep model. STUDY DESIGN: Endoscopic and open techniques of lumbar pedicle screw instrumentation and posterolateral fusion are compared in a sheep model (12 sheep in each group). The safety and fusion outcome are assessed by postoperative computed tomography (CT) scans performed at 6 months. METHODS: Twelve sheep underwent bilateral L4-L5 pedicle screw fixation and posterolateral fusion by means of endoscopic instrumentation and another 12 sheep by means of conventional open technique. For posterolateral fusions, an autologous iliac crest bone or bone graft substitute (Healos/MP52; Orquest, Mountain View, CA) was used on either the animal's left or right side. The animals were euthanized 6 months after surgery and the lumbar spines were harvested. Pedicle dimensions and screw insertion angles were measured and the two techniques were compared using CT and image analysis software. Pedicle screw misplacement was detected by means of direct inspection and CT scan, and fusions were evaluated by CT scans. RESULTS: The endoscopic group's screw insertion angle was more convergent, corresponded more closely to the human pedicle angle and was less variable than in the open technique. Three of the endoscopic group's 48 screws were misplaced medially, whereas in the open technique, 5 screws were misplaced laterally. Posterolateral bone fusion masses were palpable 6 months after surgery for both the autologous bone grafts and graft substitutes. There were no complications. The ratio of screw to pedicle diameter was approximately 0.6, greater than in human studies. CONCLUSIONS: Despite differences between pedicle dimensions and screw angles, most screws could be inserted into the sheep pedicle using endoscopic or open techniques. Bone fusion was successful in both groups. Thus, minimally invasive, endoscopic transpedicular screw-plate fixation and posterolateral fusion is feasible, and as effective as the conventional open technique.     

Stereotactic navigation for placement of pedicle screws in the thoracic spine

OBJECTIVE: Pedicle screw fixation in the lumbar spine has become the standard of care for various causes of spinal instability. However, because of the smaller size and more complex morphology of the thoracic pedicle, screw placement in the thoracic spine can be extremely challenging. In several published series, cortical violations have been reported in up to 50% of screws placed with standard fluoroscopic techniques. The goal of this study is to evaluate the accuracy of thoracic pedicle screw placement by use of image-guided techniques. METHODS: During the past 4 years, 266 image-guided thoracic pedicle screws were placed in 65 patients at the University of Michigan Medical Center. Postoperative thin-cut computed tomographic scans were obtained in 52 of these patients who were available to enroll in the study. An impartial neuroradiologist evaluated 224 screws by use of a standardized grading scheme. All levels of the thoracic spine were included in the study. RESULTS: Chart review revealed no incidence of neurological, cardiovascular, or pulmonary injury. Of the 224 screws reviewed, there were 19 cortical violations (8.5%). Eleven (4.9%) were Grade II (< or =2 mm), and eight (3.6%) were Grade III (>2 mm) violations. Only five screws (2.2%), however, were thought to exhibit unintentional, structurally significant violations. Statistical analysis revealed a significantly higher rate of cortical perforation in the midthoracic spine (T4-T8, 16.7%; T1-T4, 8.8%; and T9-T12, 5.6%). CONCLUSION: The low rate of cortical perforations (8.5%) and structurally significant violations (2.2%) in this retrospective series compares favorably with previously published results that used anatomic landmarks and intraoperative fluoroscopy. This study provides further evidence that stereotactic placement of pedicle screws can be performed safely and effectively at all levels of the thoracic spine.     

Pedicle and transverse process screws of the upper thoracic spine. Biomechanical comparison of loads to failure

STUDY DESIGN: An In vitro biomechanical load-to-failure test. OBJECTIVES: To determine the comparative axial pullout strengths of pedicle screw versus transverse process screws in the upper thoracic spine (T1-T4), and to compare their failure loads with bone density as seen on computed tomography. SUMMARY OF THE BACKGROUND DATA: The morphology of the upper thoracic spine presents technical challenges for rigid segmental fixation. Though data are available for failure characteristics of cervical-lateral mass screws, analogous data are wanting in regard to screw fixation of the upper thoracic spine. METHODS: Ten fresh-frozen human spines (T1-T4) were quantitatively scanned using computed tomography to determine trabecular bone density at each level. The vertebrae were drilled and tapped for the insertion of a 3.5-mill meter-diameter cortical bone screw in either the pedicle or the transverse process position. A uniaxial load to failure was applied. RESULTS: The mean ultimate load to failure for the pedicle screws (658 N) was statistically greater than that of the transverse process screws (361 N; P < 0.001). The T1 pedicle screw sustained the highest load to failure (775 N). No significant difference was found between load to failure for the pedicle and transverse process screws at T1. A trend toward decreasing load to failure was seen for both screw positions with descending thoracic level. Neither pedicle dimensions nor screw working length correlated with load to failure. CONCLUSIONS: Upper thoracic pedicle screws have superior axial loading characteristics compared with bicortical transverse process screws, except at T1. Load behavior of either of these screws was not predictable based on anatomic parameters.     

Cervical spine pedicle screws: a biomechanical comparison of two insertion techniques

STUDY DESIGN: Biomechanical testing of the pullout strengths of pedicle screws placed by two different techniques in adult human cadaveric cervical spines. OBJECTIVES: To determine whether there is a significant difference in screw purchase of two commonly proposed methods of cervical pedicle screw insertion. SUMMARY OF BACKGROUND DATA: Wiring techniques remain the gold standard for posterior cervical fixation. However, absent or deficient posterior elements may dictate the use of alternative fixation techniques. Cervical pedicle screws have been shown to have significantly higher pullout strength than lateral mass screws. METHODS: Fifty fresh disarticulated human vertebrae (C3-C7) were evaluated with computed tomography for anatomic disease and pedicle morphometry. The right and left pedicles were randomly assigned to either a standard method or the Abumi insertion method. In the latter technique the cortex and cancellous bone of lateral mass are removed with a high-speed burr, which provides a direct view of the pedicle introitus. The pedicle is then probed and tapped and a 3.5-mm cortical screw inserted. Each screw was subjected to a uniaxial load to failure. RESULTS: There was no significant difference in the mean pullout resistance between the Abumi (696 N) and standard (636.5 N) insertion techniques (P = 0.41). There was no difference in pullout resistance between vertebral levels or within vertebral levels. Two (4%) minor pedicle wall violations were observed. CONCLUSION: In selected circumstances pedicle screw instrumentation of the cervical spine may be used to manage complex deformities and patterns of instability. Surgeons need not be concerned about reduced screw purchase when deciding between the Abumi method and its alternatives.     

Frequency of neurological complications connected with transpedicular spine fixation]

To asses a frequency of neurological complications concerned with transpedicular spine fixation 1127 inserted transpedicular screws were reviewed. Penetration of pedicle was found in 5.5% of inserted screws. Radicular symptoms accompanied 0.8% of screw insertions. Complications were concerned only to medial or subpedicular penetrations. Highest number of potentially hazardous medial wall penetrations was found in lower lumbar spine. Treatment consisted of removal and repositioning of screws but with direct visualisation in cases with self tapping screws systems. The results shows that rate of neurological complications during transpedicular fixation is small and procedure is relatively safe.     

Complications of pedicle screw fixation in reconstructive surgery of the cervical spine

STUDY DESIGN: Retrospective evaluation of complications in 180 consecutive patients with cervical disorders who had been treated by using pedicle screw fixation systems. OBJECTIVES: To determine the risks associated with pedicle screw fixation in the cervical spine and to emphasize the importance of preoperative planning and surgical techniques in reducing the risks of this procedure. SUMMARY OF BACKGROUND DATA: Generally, pedicle screw fixation in the cervical spine has been considered too risky for the neurovascular structures. There have been several reports describing the complications of lateral mass screw-plate fixation. However, no studies have examined in detail the complications associated with cervical pedicle screw fixation. METHODS: One hundred eighty patients who underwent cervical reconstructive surgery using cervical pedicle screw fixation were reviewed to clarify the complications associated with the pedicle screw fixation procedure. Cervical disorders were spinal injuries in 70 patients and nontraumatic lesions in 110 patients. Seven hundred twelve screws were inserted into the cervical pedicles, and the locations of 669 screws were radiologically evaluated. RESULTS: Injury of the vertebral artery occurred in one patient. The bleeding was stopped by bone wax, and no neurologic complication developed after surgery. On computed tomographic (CT) scan, 45 screws (6.7%) were found to penetrate the pedicle, and 2 of 45 screws caused radiculopathy. Besides these three neurovascular complications directly attributed to screw insertion, radiculopathy caused by iatrogenic foraminal stenosis from excessive reduction of the translational deformity was observed in one patient. CONCLUSIONS: The incidence of the clinically significant complications caused by pedicle screw insertion was low. Complications associated with cervical pedicle screw fixation can be minimized by sufficient preoperative imaging studies of the pedicles and strict control of screw insertion. Pedicle screw fixation is a useful procedure for reconstruction of the cervical spine in various kinds of disorders and can be performed safely.     

新型可膨胀椎弓根螺钉在骨质疏松性腰椎融合与固定手术中的初步应用

目的 评价新型可膨胀椎弓根螺钉(Thunder钉)在骨质疏松性腰椎椎体中固定的可靠性及其临床疗效.方法 随访2006年8月至2007年12月,应用Thunder钉治疗合并骨质疏松症的各种腰椎疾患42例(236枚螺钉),其中腰椎退行性疾病24例,腰椎结核二期后路融合手术8例,腰椎骨质疏松性压缩骨折6例,腰椎翻修手术4例.所有病例术前均行骨密度检查,患者腰椎骨密度平均下降2.6个标准差.术后处理与其他腰椎内固定术后患者相同.术后1周、3个月、半年、1年及2年随访患者,摄X线片并进行CT扫描三维重建,了解椎弓根螺钉稳定性及脊柱融合情况.结果42例患者均获平均16(12～24)个月的随访.术后3、6、12及24个月的影像学检查显示,所有Thunder钉位置良好,无螺钉松动、断裂迹象,评分平均值分别为3.0、3.0、2.9和2.9.脊柱骨融合于术后随时间延长趋于完善,骨融合评分平均值分别为2.3、2.5、3.0、3.0.所有患者临床症状缓解,疗效满意.结论 Thunder钉具有良好的钉-骨界面结合,能够提高螺钉在骨质疏松椎体中的固定强度,为脊柱融合提供良好的基础,临床疗效满意.     

Biomechanical comparison of a novel multilevel hex-head pedicle screw design with a conventional head design.

The objective of the study was to determine the biomechanical effect during insertion of multilevel hex-head design pedicle screws compared to a conventional screw-head design. Eighteen lumbar vertebrae and thoracic vertebrae from human cadavers were instrumented with a novel, multilevel hexagonal head pedicle screw on one side and a conventional head pedicle screw on the contralateral side. Screws were inserted at a constant rate and insertion and removal torques were recorded. A further 14 lumbar and thoracic vertebrae were used to test alterability of screw direction and operational effort required. Electromagnetic sensors recorded the change in angular direction for both screw and screwdriver. The force applied through the insertion screwdriver required to produce the directional change was also recorded. No significant differences were found between the two screw types for insertion or removal torque in either lumbar or thoracic vertebrae. Multilevel hex-head screws had significantly greater directional alterability than conventional head screws in both lumbar and thoracic specimens. Multilevel hex-head screws also required less force applied through the screwdriver than conventional screws to alter direction of screw insertion in both lumbar and thoracic specimens. The multilevel hex-head design did not affect the insertion or removal torque in comparison to a conventional head design.     

Early complications of spinal pedicle screw

The complications of 648 consecutively inserted Universal AO pedicle screws (140 in the thoracic spine and 508 in the lumbar spine) performed by one surgical team to treat 91 patients with spinal problems, were reviewed. The spinal pathology consisted of: scoliosis (34 patients), degenerative lower lumbar spinal disease (25 patients), neoplastic spinal disease (11 patients), thoracic kyphosis (8 patients), spinal fractures (7 patients), lumbo-sacral spondylolisthesis (3 patients), and osteomyelitis (3 patients). Intraoperative complications were: screw misplacement (n = 3), nerve root impingement (n = 1), cerebrospinal fluid leak (n = 2) and pedicle fracture (n = 2). Postoperative complications were; deep wound infection (n = 4), screw loosening (n = 2) and rod-screw disconnection (n = 1). The conclusion was that pedicle screw fixation has an acceptable complication rate and neurological injury during this procedure is unlikely.     

Accuracy of single-time, multilevel registration in image-guided spinal surgery.

BACKGROUND CONTEXT: Computerized frameless stereotactic image-guidance has been used in recent years to improve the accuracy and safety of pedicle screw placement during spine surgery. Because the possibility of intervertebral motion exists, and because the patient is usually in a different position when preoperative imaging is performed compared with the operative position, it has been suggested that the imaging model of the complete lumbar spine and the surgically exposed lumbar spine may be significantly discordant. Consequently, current protocols suggest registering each spinal level (single-level registration) separately before pedicle screw placement at that level, a time-consuming process. PURPOSE: To assess the accuracy of single-time multilevel registration for multilevel pedicle screw placement during image-guided, computer-assisted spine surgery, in the setting of degenerative disorders of the lumbar spine. STUDY DESIGN/SETTING: This is a prospective clinical and radiological study of 45 patients with degenerative disorders of the lumbar spine who underwent instrumented fusion with the use of single-time multilevel registration computer-assisted, image-guided tomography. The accuracy of the pedicle screws placement was confirmed on the basis of a protocol that included intraoperative spontaneous electromyographic (EMG) recordings, direct pedicle visualization, and computer tomography (CT) scans when clinically indicated during the follow-up period. PATIENT SAMPLE: Forty-five consecutive patients who fulfilled the criteria of computer-assisted, image-guided tomography pedicle screw placement for degenerative lumbar spine disease without overt instability. OUTCOME MEASURES: The principal outcome measure was the accuracy of pedicle screw placement with single-time multilevel registration for multilevel pedicle screw placement during image-guided, computer-assisted spine surgery; postoperative CT performed for clinical indications during the follow-up course was used for the assessment of pedicle screw placement. METHODS: Patients were assessed clinically before and after the operation. Data from 45 consecutive cases of image-guided, computer-assisted lumbar spinal fusion were statistically analyzed to determine the relationship between the number of levels registered during single-time registry and the mean registration error (MRE). Intraoperative spontaneous EMG, direct visualization, and postoperative CT scans were used to assess the accuracy of pedicle screw insertion. RESULTS: None of the patients involved in this study experienced clinical sequelae of improper pedicle screw placement. MREs after surface mapping and after point merge were small (less than 1.00 mm and less than 3.00 mm, respectively). During the intraoperative assessment of the pedicle screws placement, no significant spontaneous EMG activity was recorded and the pedicular walls were found intact in direct visualization. The postoperative CT scans showed in 10 patients accurate placement in 55 of the 57 pedicle screws with expansion of the medial wall in two screws. CONCLUSIONS: Single-time, multilevel registration may decrease operative time relative to repeated, single-level registrations, without compromising the increased accuracy of pedicle screw placement afforded by this technique in the setting of degenerative disorders of the lumbar spine. Despite the advantages in computer-guided image surgery, cautious application in the individual patient is recommended until more comprehensive data can be gathered in specific degenerative pathology with overt instability; thus the knowledge of the anatomy remains crucial.     

Pedicle screw placement in the thoracic spine: a randomized comparison study of computer-assisted navigation and conventional techniques

Objective： To evaluate the accuracy of computer-assisted pedicle screw installation and its clinical benefit as compared with conventional pedicle screw installation techniques.
Methods： Total 176 thoracic pedicle screws placed in 42 thoracic fracture patients were involved in the study randomly, 20 patients under conventional fluoroscopic control （84 screws） and 22 patients had screw insertion under three dimensional （3D） computer-assisted navigation （92 screws）. The 2 groups were compared for accuracy of screw placement, time for screw insertion by postoperative thincut CT scans and statistical analysis by χ^2 test. The cortical perforations were then graded by 2-mm increments： Grade Ⅰ （good, no cortical perforation）, Grade Ⅱ （screw outside the pedicle 〈2 mm）, Grade Ⅲ （screw outside the pedicle 〉2 mm）.
Results： In computer assisted group, 88 （95.65%） were Grade Ⅰ （good）, 4 （4.35%） were Grade Ⅱ （〈2mm）, no Grade Ⅲ （〉2 mm） violations. In conventional group, there were 14 cortical violations （16.67%）, 70 （83.33%） were Grade Ⅰ （good）, Ⅱ （13.1%） were Grade Ⅱ （〈2 mm）, and 3 （3,57%） were Grade Ⅲ （〉2 mm） violations （P〈0.001）. The number （19.57%） of upper thoracic pedicle screws （ T1-T4 ） inserted under 3D computer-assisted navigation was significantly higher than that （3.57%） by conventional fluoroscopic control （P〈0.001）. Average screw insertion time in conventional group was （4.56 ±1.03） min and （2.54 ± 0.63） min in computer assisted group （P〈0.001）. In the conventional group, one patient had pleura injury and one had a minor dura violation.
Conclusions： This study provides further evidence that 3D computer-assisted navigation placement ofpedicle screws can increase accuracy, reduce surgical time, and be performed safely and effectively at all levels of the thoracic spine, particularly upper thoracic spine.     

Placement of pedicle screws using different navigation systems. A laboratory trial with 12 spinal preparations

A well-known problem occurring with thoracolumbar spondylodesis is the perforation of pedicle screws through the pedicle wall. It occurs in up to 40% of the implanted screws. To reduce this problem, computed tomography (CT)-based navigation systems have been introduced, which allow the surgeon multidimensional control of the screw position in virtual reality and real time during insertion. In the recent past, fluoroscopy-based navigation systems have also been built. We inserted 77 pedicle screws in human lumbar cadaveric spine specimens either without navigation, with CT-based navigation, or with fluoroscopy-based navigation. In the critical sizes of pedicles between 6.5 and 9 mm, we found the best results with CT-based navigation, but there was no significant difference between the three methods. The minimal pedicle and the screw diameters should be reported in every study on pedicle screw misplacement and spine navigation since they represent the most important factor in pedicle wall perforations.     

Accuracy of percutaneous pedicle screws for thoracic and lumbar spine fractures: a prospective trial

Purpose

The percutaneous insertion technique requires surgical skill and experience. However, there have been few clinical reports evaluating the accuracy of minimally invasive pedicle screw placement using the conventional fluoroscopy method. The purpose of this study was to evaluate the accuracy of percutaneous pedicle screw placement in the treatment of thoracic and lumbar spine fractures using two-plane conventional fluoroscopy.

Methods

A prospective clinical trial was performed. A total of 502 percutaneous pedicle screws in 111 patients, all inserted with the assistance of conventional fluoroscopy, were evaluated. The safety and accuracy of pedicle screw placement were based on the evaluation of postoperative axial 3-mm slice computed tomography scans using the scoring system described by Zdichavsky et al. [Eur J Trauma 30:234–240, 2004; Eur J Trauma 30:241–247, 2004].

Results

427/502 pedicle screws (85 %) were classified as good and excellent concerning the best possible screw length and 494/502 (98 %) were found to have good or excellent position. One screw had to be revised due to medial position with a neurological deficit.

Conclusions

This study demonstrates the feasibility of placing percutaneous posterior thoracolumbar pedicle screws with the assistance of conventional fluoroscopy. Minimally invasive transpedicular instrumentation is an accurate, reliable and safe method to treat a variety of spinal disorders, including thoracic and lumbar spine fractures.