Correction of adolescent idiopathic scoliosis using thoracic pedicle screw fixation versus hook constructs

This retrospective study was undertaken to determine the effectiveness and cost of thoracic pedicle screws versus laminar and pedicle hooks in patients undergoing surgical correction of adolescent idiopathic scoliosis (AIS). Immediate preoperative and 6-week postoperative radiographs were examined in 25 consecutive cases of children with AIS who were divided into two groups, those with thoracic pedicle screw constructs and those with thoracic hook constructs. Endpoints collected included radiographic measures, complications, surgical time, implant cost, and quality-of-life measures. Ten children underwent spinal fusion using thoracic pedicle screw fixation and 15 underwent thoracic constructs composed of hooks. Similar sex and age distribution were noted in both groups, and among the 20 girls and 5 boys the average age was 14.5. The mean preoperative Cobb angle was 53.5 degrees for the screw group and 52.5 degrees for the hook group. Correction averaged 70.2% for the screw group and 68.1% for the hook group. There were no significant differences between the two patient groups in terms of percentage of or absolute curve change after surgery. The apical vertebral translation, end vertebral tilt angle, and coronal balance did not differ significantly between the two patient groups. Comparison of operative time and quality of life revealed no significant differences. Screw constructs were significantly more expensive than hook constructs. The correction obtained from thoracic pedicle screw fixation is comparable to traditional hook constructs in AIS. Surgery using either construct effectively corrects AIS.     

Comparison of intraoperative supine and postoperative standing radiographs after posterior instrumentation for adolescent idiopathic scoliosis

The utility of intraoperative radiographs after posterior spinal segmental instrumentation for adolescent idiopathic scoliosis (AIS) is debatable. A retrospective review of 74 patients with moderately severe AIS revealed the main thoracic Cobb measurements of 57° preoperatively, 17° intraoperatively, 18° on initial postoperative, and 20° on final postoperative radiographs. On the basis of the extent and type of instrumentation (pedicle screws vs. hybrid construct), there was no clinically significant difference in curve magnitude between intraoperative and postoperative radiographs. After posterior segmental instrumentation for moderate AIS, frontal plane correction measured on intraoperative supine radiographs are comparable with similar measurements made on full-length postoperative standing radiographs.     

Computer-assisted thoracic pedicle screw placement: an in vitro feasibility study

STUDY DESIGN: In this cadaveric study, a computer-assisted image guidance system was tested for accuracy of thoracic pedicle screw placement. OBJECTIVES: Evaluate the system's accuracy for thoracic pedicle screw placement in vitro. SUMMARY OF BACKGROUND DATA: The effective use and reliability of pedicle screw instrumentation in providing short-segment stabilization and correction of deformity is well known in the lumbar spine. Pedicle screw placement in the thoracic spine is difficult because of the small dimensions of the thoracic pedicles and risk to the adjacent spinal cord and neurovascular structures. Investigators have shown the improved accuracy of computer-assisted lumbar pedicle screw placement; but the accuracy of computer-assisted thoracic pedicle screw placement, which is becoming more widely used, has not been shown. METHODS: In five human cadavers, 120 thoracic pedicle screws were placed with computer-assisted image guidance. The largest clinically feasible screw was used based on the cross-sectional dimensions of each pedicle. The accuracy was assessed by postoperative computed tomography and visual inspection. RESULTS: The overall pedicle cortex violation was 23 of 120 pedicles (19.2%). Nine violations (7.5%) were graded as major and 14 (11.7%) as minor. A marked and progressive learning curve was evident with the perforation rates that decreased from 37.5% in the first cadaver to 4.2% in the last two cadavers. CONCLUSIONS: Accurate thoracic pedicle screw placement is feasible with computer-assisted surgery. However, as with any other new surgical technology, the learning curve must be recognized and incorporated into the necessary fundamental knowledge and experience for these procedures.     

Comparative analysis of pedicle screw and hook instrumentation in posterior correction and fusion of idiopathic thoracic scoliosis

Posterior correction and fusion with segmental hook instrumentation represent the gold standard in the surgical treatment of progressive idiopathic thoracic scoliosis. However, there is a debate over whether pedicle screws are safe in scoliosis surgery and whether their usage might enable a better curve correction and a shorter fusion length. The details of curve correction, fusion length and complication rate of 99 patients with idiopathic thoracic scoliosis treated with either hook or pedicle screw instrumentation were analyzed. Forty-nine patients had been operated with the Cotrel-Dubousset system using hooks exclusively ("hook group"). Fifty patients had been operated with either a combination of pedicle screws in the lumbar and lower thoracic and hooks in the upper thoracic spine or exclusive pedicle screw instrumentation using the Münster Posterior Double Rod System ("screw group"). The preoperative Cobb angle averaged 61.3 degrees (range 40 degrees-84 degrees ) in the hook group and 62.5 degrees (range 43 degrees-94 degrees ) in the screw group. Average primary curve correction was 51.7% in the hook group and 55.8% in the screw group ( P>0.05). However, at follow-up (2-12 years later) primary curve correction was significantly greater ( P=0.001) in the screw group (at 50.1%) compared to the hook group (at 41.1%). Secondary lumbar curve correction was significantly greater ( P=0.04) in the screw group (54.9%) compared to the hook group (46.9%). Correction of the apical vertebral rotation according to Perdriolle was minimal in both groups. Apical vertebral translation was corrected by 42.0% in the hook group and 55.6% in the screw group ( P=0.008). Correction of the tilt of the lowest instrumented vertebra averaged 48.1% in the hook group and 66.2% in the screw group ( P=0.0004). There were no differences concerning correction of the sagittal plane deformity between the two groups. Fusion length was, on average, 0.6 segments shorter in the screw group compared to the hook group ( P=0.03). With pedicle screws, the lowest instrumented vertebra was usually one below the lower end vertebra, whereas in the hook group it was between one and two vertebrae below the lower end vertebra. Both operative time and intraoperative blood loss were significantly higher in the hook group ( P<0.0001). One pedicle screw at T5 was exchanged due to the direct proximity to the aorta. There were no neurologic complications related to pedicle screw instrumentation. Pedicle screw instrumentation alone or in combination with proximal hook instrumentation offers a significantly better primary and secondary curve correction in idiopathic thoracic scoliosis and enables a significantly shorter fusion length.     

Pedicle morphology in thoracic adolescent idiopathic scoliosis: is pedicle fixation an anatomically viable technique?

STUDY DESIGN: A radiographic study of thoracic pedicle anatomy in a group of adolescent idiopathic scoliosis (AIS) patients. OBJECTIVE: To investigate the anatomic constraints of the thoracic pedicles and determine whether the local anatomy would routinely allow pedicle screw insertion at every level. SUMMARY OF BACKGROUND DATA: In spite of the clinical successes reported with limited thoracic pedicle screw-rod constructs for thoracic AIS, controversy exists as to the safety of this technique. MATERIAL AND METHODS: Twenty-nine patients with right thoracic AIS underwent preoperative thoracic CT scans and plain radiographs. Anatomic parameters were measured from T1 to T12. RESULTS: Information on 512 pedicles was obtained. The transverse width of the pedicles from T1 through T12 ranged from 4.6-8.25 mm. The medial pedicle to lateral rib wall transverse width from T1 through T2 ranged from 12.6 to 17.9 mm. Measured dimensions from the CT scans showed the actual pedicle width to be 1-2 mm larger than would have been predicted from the plain radiographs. Age, Risser grade, curve magnitude, and the amount of segmental axial rotation did not correlate with the morphology or size of the thoracic pedicles investigated. In no case would pedicle morphology have precluded the passage of a pedicle screw. CONCLUSION: Based on the data identified in this group of adolescent patients, it is reasonable to consider pedicle screw insertion at most levels and pedicle-rib fixation at all levels of the thoracic spine during the treatment of thoracic AIS.     

Transfacet screw placement for posterior fixation of C-7

OBJECT: Lateral mass screws are traditionally used to fixate the subaxial cervical spine, while pedicle screws are used in the thoracic spine. Lateral mass fixation at C-7 is challenging due to thin facets, and placing pedicle screws is difficult due to the narrow pedicles. The authors describe their clinical experience with a novel technique for transfacet screw placement for fixation at C-7. METHODS: A retrospective chart review was undertaken in all patients who underwent transfacet screw placement at C-7. The technique of screw insertion was the same for each patient. Polyaxial screws between 8- and 10-mm-long were used in each case and placed through the facet from a perpendicular orientation. Postoperative radiography and clinical follow-up were analyzed for aberrant screw placement or construct failure. RESULTS: Ten patients underwent C-7 transfacet screw placement between June 2006 and March 2007. In all but 1 patient screws were placed bilaterally, and the construct lengths ranged from C-3 to T-5. One patient with a unilateral screw had a prior facet fracture that precluded bilateral screw placement. There were no intraoperative complications or screw failures in these patients. After an average of 6 months of follow-up there were no hardware failures, and all patients showed excellent alignment. CONCLUSIONS: The authors present the first clinical demonstration of a novel technique of posterior transfacet screw placement at C-7. These results provide evidence that this technique is safe to perform and adds stability to cervicothoracic fixation.     

Computer-assisted pedicle screw placement for thoracolumbar spine fracture with separate spinal reference clamp placement and registration

BACKGROUND: The objective of the study was to improve the accuracy of computer-assisted pedicle screw installation in the spine. This study evaluates the accuracy of computer-assisted pedicle screw placement with separate spinal reference clamp placement and registration on each instrumented vertebra for thoracolumbar spine fractures. METHODS: Postoperative radiographs and CT scans assessed the accuracy of pedicle screw placement in 21 adult patients on each instrumented vertebra. Screw placements were graded as good if the screws were placed in the central core of the pedicle and the cancellous portion of the body. Screw placements were graded as fair if the screws were placed slightly eccentrically, causing erosion of the pedicular cortex, and with less than a 2-mm perforation of the pedicular cortex. Screw placements were graded as poor if screws were placed eccentrically with a large portion of the screw extending outside the cortical margin of the pedicle and with more than a 2-mm perforation of the pedicular cortex. RESULTS: A total of 140 image-guided pedicle screws were placed in 21 patients: 78 in the thoracic and 62 in the lumbar spine. Of the 140 pedicle screw placements, 96.4% (135/140) were categorized as good; 3.6% (5/140), fair; and 0% were poor. All 5 fair placement screws were placed in the thoracic spine without any mobility. CONCLUSION: Separate registration increases accuracy of screw placement in thoracolumbar pedicle instrumentation. Separate spinal reference clamp placement in the instrumented vertebra provides real-time virtual imaging that decreases the possibility of downward displacement during manual installation of the screw.     

Thoracic pedicle screw instrumentation using the "Funnel Technique": part 2. Clinical experience

This study is a retrospective review of the clinical results of patients treated with thoracic pedicle screws using the "funnel technique." The objective is to report the clinical results of patients treated with thoracic pedicle screws using the funnel technique for screw placement. A total of 115 patients treated with the use of at least one thoracic pedicle screw were retrospectively identified. All patients were treated at a single medical center, under the senior author's supervision. Twenty-five different residents were responsible for placing 50-60% of these screws, and five different fellows and the senior author placed the remainder. The accuracy of screw placement and the complications related to the use of thoracic pedicle screws were analyzed by assessing intraoperative and postoperative charts and radiographs. There were 115 patients (age range 9-82 years) with the average follow-up period of 17 months. The total number of screws used was 348; the screw diameter ranged from 4.0 to 7.75 mm. There were no vascular or pulmonary complications. There was no iatrogenic neurologic injury, except for one patient who developed a transient anterior thigh numbness from intraoperative positioning. In fracture patients, 35% (10 of 28) had documented neurologic improvement postoperatively. There were no obviously misplaced pedicle screws on detailed review of intraoperative and postoperative radiographs. No screws had to be electively removed for complications related to misplacement. There were four broken screws, one broken rod, two loose screws, and three connector disengagements. Two patients had deep infections and four patients had pseudarthrosis requiring additional surgery. The clinical results proved that thoracic pedicle screws can be safely placed with the funnel technique.     

Prospective evaluation of thoracic pedicle screw placement using fluoroscopic imaging

BACKGROUND: In this prospective 18-month study, 29 patients underwent posterior thoracic instrumentation with placement of 209 transpedicular screws guided by intraoperative fluoroscopic imaging and anatomic landmarks. We assessed the safety, accuracy, complications, and early stability of this technique. METHODS: Pedicle and pedicle-rib units were measured, and screw cortical penetrations were graded on anatomy and depth of penetration. All 29 patients underwent preoperative computed tomographic (CT) imaging, and 28 underwent postoperative CT imaging (199/209 screws). RESULTS: From T2 to T12, screw diameters were >or=5 mm with mean medial screw angulation measuring 20-25 degree. Of the 209 screws placed from T1 to T12, 111 had diameters greater than or equal to the pedicle width. From T3 to T9, the mean diameter of the pedicle screws exceeded the mean pedicle width. Lateral pedicle wall penetration occurred significantly more often than superior, inferior, and medial pedicle wall penetrations and anterolateral vertebral body penetration. Five of six high-risk screw penetrations occurred in one patient when intraoperative technique was compromised. We observed no new postoperative neurologic deficits, visceral injuries, or pedicle screw instrumentation failures. The three high-risk anterolateral vertebral body penetrations at T1 and T2 were associated with a significantly decreased mean screw transverse angle; the three high-risk medial pedicle wall penetrations occurring from T3 to T9 were associated with a significantly increased mean screw transverse angle. Among all 26 patients available at postoperative follow-up (mean 11.9 months), the mean loss of kyphosis correction was 2.0 degree. CONCLUSIONS: Guided by intraoperative fluoroscopic imaging and anatomic landmarks, thoracic pedicle screws can be placed safely. Early clinical follow-up reveals excellent results with minimal loss of kyphosis correction.     

应用椎板开窗法置入胸椎椎弓根螺钉的精确性和安全性评估

目的 分析应用椎板开窗法行胸椎椎弓根螺钉置入治疗重度脊柱侧后凸患者的精确性和安全性. 方法 1996年6月至2007年12月,应用椎板开窗法行胸椎椎弓根螺钉置入治疗23例重度脊柱侧后凸患者(A组),其中男性9例,女性14例;年龄13～23岁,平均17.8岁;术前主胸弯冠状面Cobb角平均97.3°,平均后凸角67.4°.作为对照,同期应用非开放法置钉治疗重度脊柱侧后凸患者22例(B组),其中男性7例,女性15例;年龄14～21岁,平均17.2岁;术前主胸弯冠状面Cobb角平均为96.6°,平均后凸角62.1°.两组患者术后均行CT扫描,统计螺钉置入并发症,对螺钉穿透椎弓根皮质骨的CT扫描图像进行联机测量并统计分析.结果 A组和B组各置入胸椎椎弓根螺钉209和201枚,术中发生椎弓根骨折5例和16例,发生硬膜撕裂4例和7例,螺钉错置18枚和45枚.B组螺钉错置率高于A组,差异具有统计学意义(P<0.05).A组上、中胸椎与下胸椎之间、凸侧与凹侧之间,螺钉错置率差异均具有统计学意义(P<0.05).两组均无脊髓及大血管损伤. A和B组经平均3.2年、3.4年随访,术后冠状面和矢状面平均矫正度未见明显丢失.结论 重度脊柱侧后凸胸椎椎弓根螺钉置入技术难度较高,应用椎板开窗法可有效增加螺钉置入精确性和安全性.     

Accuracy and safety of thoracic pedicle screw placement in spinal deformities

OBJECTIVES: To determine the safety of pedicle screw fixation in thoracic spine deformity correction. METHODS: One hundred twelve pedicle screws were surgically placed in 25 patients with degenerative, posttraumatic, and Scheuermann kyphosis and idiopathic and neuromuscular scoliosis. Screw position was evaluated using intraoperative and postoperative radiographs and thin-slice computed tomography. RESULTS: Of the total 112 thoracic pedicle screws that were inserted, 98 screws (87.5%) were fully contained within the cortical boundaries of the pedicle. When comparing proximal screws (T1-T8) with distal screws (T9-T12) and convex placed screws with concave ones, a statistically significant difference in screw placement was evident (P < 0.05). More misplaced screws were seen proximally and on the concave side. Of the 14 malpositioned screws, 2 (1.8%) demonstrated aortic abutment. There were no neurologic deficits, vascular injuries, or mechanical failures recorded. CONCLUSIONS: Placement of thoracic pedicle screws is both feasible and safe.     

漏斗技术结合探针技术置入胸椎椎弓根螺钉在脊椎畸形矫形术中的应用

目的 探讨应用漏斗技术结合探针技术置入胸椎椎弓根螺钉在脊椎畸形矫形术中的实用性和安全性。方法 12例脊椎畸形患者接受了后路矫形固定术,在手术矫形过程中,胸椎椎弓根螺钉的置入均采用“漏斗技术结合探针技术”,记录术中和术后并发症;术后常规复查X线片和CT,记录穿出骨皮质螺钉数目及距离。结果 采用“漏斗技术结合探针技术”共置入胸椎椎弓根螺钉129枚,术后复查CT见129枚螺钉中2枚穿透椎弓根内侧壁,3枚螺钉穿破外侧壁;1枚螺钉穿透椎体前壁。Heary分级,其置钉准确性达96.12%。结论 在脊椎畸形矫形术中,应用“漏斗技术结合探针技术”置入胸椎椎弓根螺钉的方法是实用的、安全的。     

Evaluation of pedicle screw position in thoracic and lumbar spine fixation using plain radiographs and computed tomography. A prospective study of 35 patients.

STUDY DESIGN: This was a prospective study of 35 consecutive patients in whom pedicle screw position was assessed after surgery, using lateral radiographs and computed tomography. OBJECTIVE: To evaluate the accuracy of plain radiographs and computed tomography in assessment of pedicle screw position. SUMMARY OF BACKGROUND DATA: Imaging techniques, such as postoperative anteroposterior and lateral plain radiographs and computed tomography, are currently the primary means of assessing pedicle screw placement. METHODS: Postoperative radiographs and computed tomographic scans were used to evaluate the position of 220 pedicle screws inserted in the spines of 35 consecutive patients who underwent thoracic and lumbar spine fusion and instrumentation. No recognized neurologic complication resulted from pedicle screw placement. Screw position was graded as in, out, or questionable. All observations were performed independently by three observers. The authors also analyzed the position of the screws according to the underlying spinal disease. RESULTS: More misplaced screws were clearly seen on computed tomographic scans than on plain radiographs; however, this difference was not statistically significant. Interobserver differences were not statistically significant. Intraobserver differences approached statistical significance when the results of the two test were compared. CONCLUSIONS: Although the accuracy of computed tomographic imaging is better than that of plain radiographs, the difference does not reach statistical significance. Postoperative use of plain radiographs remains a reliable method for evaluation of pedicle screw insertion in the absence of neurologic deficit.     

颈椎椎弓根螺钉徒手植入技术的临床研究

目的 评价颈椎椎弓根螺钉徒手植入技术（无须术中影像技术引导）的安全性和可靠性。方法应用Axis内固定系统（美国枢法模公司）对36例颈椎疾病患者进行颈后路经椎弓根内固定术,共植入螺钉144枚,方法如下：①术中清晰地显露颈椎侧块和突间关节,用直径3,0mm高速球形磨钻去除侧块外上象限处骨皮质,然后用2．0mm的自制手锥沿椎弓根事先确定的方向轻轻钻入,若遇阻力则需略改变方向,使其自然置入,深约2～2,5cm。确定无误后,则安置Axis钛板和置入长度合适的椎弓根螺钉。②安装完毕后,即用C型臂X线机作双斜位透视,无误后关闭切口。结果从G～G,共植入根弓根螺钉144枚,其中10枚（6．8％）钉初次置入后感觉松动,经校正后二次置入成功,11枚（3．5％）钉道钻孔后出血较多,但及时处理后出血停止并无不良结果。术后X线斜位片及CT片显示,16枚（11．1％）螺钉穿破椎弓根,其中10枚螺钉（6．9％）穿破椎弓根外侧皮质,4枚（2．8％）穿破椎弓根上侧皮质,2枚（1．3％）穿破椎弓根下侧皮质。随访未发现与螺钉置入穿破椎弓根皮质有关的神经血管损伤问题。结论本研究提示,在事先充分的对每个患者颈椎椎弓根X线及CT解剖结构了解的情况下,徒手置入椎弓根螺钉行颈椎后路内固定安全可行。     

A free‐hand technique for pedicle screw placement in the lower cervical spine

Objective: To describe a free‐hand method for pedicle screw placement in the lower cervical spine with no intraoperative imaging monitors, and to evaluate the safety of this technique. Methods: A study of the free‐hand technique of cervical pedicle screw placement was conducted by postoperative radiological review and follow‐up. Thirty‐six patients who had had cervical reconstruction with posterior plate utilizing pedicle screw fixation, and been followed for a minimum of 2 years, were studied. The position of the pedicle screw was evaluated by postoperative oblique radiographs and axial computed tomograms. Clinical outcomes were measured by Odem's criteria. Results: A total of 144 screws of diameter 3.5 or 4.0 mm were inserted into the cervical pedicles in 36 patients. Postoperative images showed that 16 (11.1%) of the screws had penetrated the pedicle walls. Among them, 10 (6.9%) screws had penetrated the lateral, 4 (2.8%) the superior and 2 (1.3%) the inferior walls. However, there were no neurological or vascular complications related to the malpositioned screws during a minimum of 2 years follow‐up. In addition, Odem's scores were applied postoperatively in all patients except one with complete neurological deficit. Conclusion: Based on 144 screw placements, cervical pedicle screw insertion utilizing a free‐hand technique without intraoperative imaging guidance seems to be safe and reliable. However, solid knowledge of the anatomy of the cervical pedicle and adjacent neurovascular bundles, and careful preoperative review of cervical images, are imperative for successful screw placement in the cervical spine.     

Accuracy of upper thoracic pedicle screw placement using three-dimensional image guidance

Background contextPedicle screw malposition rates using conventional techniques have been reported to occur with a frequency of 6% to 41%. The upper thoracic spine (T1–T3) is a challenging area for pedicle screw placement secondary to the small size of the pedicles, the inability to visualize this area with lateral fluoroscopy, and significant consequences for malpositioned screws. We describe our experience placing 150 pedicle screws in the T1–T3 levels using three-dimensional (3D) image guidance.PurposeThe aim of this study was to assess the accuracy of 3D image guidance for placing pedicle screws in the first three thoracic vertebrae.Study designThe accuracy of pedicle screw placement in the first three thoracic vertebrae was evaluated using postoperative thin-section computed tomography (CT) scans of the cervicothoracic region.Patient sampleThirty-four patients who underwent cervicothoracic fusion were included.Outcome measuresRadiological investigation with CT scans was performed during the postoperative period.MethodsThirty-four consecutive patients underwent cervicothoracic instrumentation and fusion for a total of 150 pedicle screws placed in the first three thoracic vertebrae. All screws were placed using 3D image guidance. Medical records and postoperative imaging of the cervicothoracic junction for each patient were retrospectively reviewed. An independent radiologist reviewed the placement of the pedicle screws and assessed for pedicle breach. All cortical violations were reported as Grade 1, 0 to 2 mm; Grade 2, 2 to 4 mm; and Grade 3, greater than 4 mm.ResultsOverall, 140 (93.3%) out of 150 screws were contained solely in the desired pedicle. All 10 pedicle violations were Grade 1. The direction of pedicle violation included three medial, four inferior, two superior, and one minor anterolateral vertebral body. No complication occurred as a result of screw placement or the use of image guidance.ConclusionsUpper thoracic pedicle screw placement is technically demanding as a result of variable pedicle anatomy and difficulty with two-dimensional visualization. This study demonstrates the accuracy and reliability of 3D image guidance when placing pedicle screws in this region. Advantages of this technology in our practice include safe and accurate placement of spinal instrumentation with little to no radiation exposure to the surgeon and operating room staff.     

A new paradigm for staging pedicle screw-based spinal procedures: rationale, feasibility, safety, and efficacy

OBJECT: The aims of this study were to present the rationale for and the evolution of a staged, two-procedure paradigm for spinal surgery requiring pedicle screw instrumentation, and to evaluate the feasibility, safety, and efficacy of the technique. METHODS: The rationale for the new algorithm is presented for consideration in the form of unproven hypotheses subject to verification by subsequent studies. The first stage of the two-staged algorithm, performed in an interventional radiology (IR) setting, involves percutaneous placement of either headless pedicle screws or K-wire fragment placeholders of the trajectory for pedicle screws. The second stage, performed days or weeks later, involves open surgical completion of instrumentation placement and other surgical objectives. The techniques for IR percutaneous K-wire fragment and percutaneous screw placement evolved over the duration of the study. Instrumentation was placed in 126 pedicles in 25 patients. Efficacy was equated to the accuracy of screw placement, which was evaluated using computed tomography (CT). Algorithms incorporating correction for metal artifact were developed to determine deviation of the screws and K-wire fragments from proper position. Over 1500 measurements were made to evaluate K-wire fragment and screw position in the 116 instrumented pedicles for which CT data were available. RESULTS: Accuracy of placement (relative to both cortical and pedicle breaches or to only pedicle breaches) was 98 to 100% for K-wire fragments, 96 to 98% for screws following K-wire fragments, and 100% for percutaneous screws. The only adverse consequence of pedicle screw placement by this method was one infection that occurred 8 months postoperatively. CONCLUSIONS: The staged, two-procedure paradigm for pedicle screw placement proved, within the limits of this study, to be feasible, safe, and effective; therefore, the unproven rationale behind the new paradigm merits further evaluation in a larger cohort of patients with randomized, matched controls.     

Accuracy and safety of free-hand pedicle screw fixation in age less than 10 years

Background:

Pedicle screws are being used commonly in the treatment of various spinal disorders. However, use of pedicle screws in the pediatric population is not routinely recommended because of the risk of complications. The present study was to evaluate the safety of pedicle screws placed in children aged less than 10 years with spinal deformities and to determine the accuracy and complication (early and late) of pedicle screw placement using the postoperative computed tomography (CT) scans.

Materials and Methods:

Thirty one patients (11 males and 20 females) who underwent 261 pedicle screw fixations (177 in thoracic vertebrae and 84 in lumbar vertebrae) for a variety of pediatric spinal deformities at a single institution were included in the study. The average age of patients was 7 years and 10 months. These patients underwent postoperative CT scan which was assessed by two independent observers (spine surgeons) not involved in the treatment.

Results:

Breach rate was 5.4% (14/261 screws) for all pedicles. Of the 177 screws placed in the thoracic spine, 13 (7.3%) had breached the pedicle, that is 92.7% of the screws were accurately placed within pedicles. Seven screws (4%) had breached the medial pedicle wall, 4 screws (2.3%) had breached the lateral pedicle wall and 2 screws (1.1%) had breached the superior or inferior pedicle wall respectively. Of the 84 screws placed in the lumbar spine, 83 (98.8%) screws were accurately placed within the pedicle. Only 1 screw (1.2%) was found to be laterally displaced. In addition, the breach rate was found to be 4.2% (11/261 screws) with respect to the vertebral bodies. No neurological, vascular or visceral complications were encountered.

Conclusions:

The accuracy of pedicle screw placement in pedicles and vertebral bodies were 94.6% and 95.8% respectively and there was no complication related to screw placement noted until the last followup. These results suggest that free-hand pedicle screw fixation can be safely used in patients younger than 10 years to treat a variety of spinal disorders.     

The accuracy of pedicle screw placement in the thoracic spine using the "Funnel Technique": part 1. A cadaveric study

A cadaveric study using the "funnel technique" to probe thoracic pedicles was conducted. The results (location, level, and perforation rate) of three spine surgeons of varying experience were compared. The objectives were to evaluate the reliability and accuracy of the funnel technique for the placement of thoracic pedicle screws and to describe the technique. Nine fresh cadavers (216 thoracic pedicles) were used for pedicle screw placement using the funnel technique. The study was conducted by three spine surgeons with a significantly different level of experience in thoracic pedicle screw placement (72 thoracic pedicles each). Critical and noncritical perforations were recorded. The perforation rate was 6% (13 of 216 pedicles). Of this, only 0.4% (1 of 216) was a critical perforation (a contact with T8 nerve root). The junior spine surgeon who had no previous experience with thoracic pedicle screw placement had a 12.5% (9 of 72) perforation rate, the surgeon very familiar with the technique had a 5.5% (4 of 72) perforation rate, and the senior author who originated this technique had a 1.4% (1 of 70) perforation rate. All perforations made by the junior spine surgeon occurred in his first 24 pedicles; none occurred in his last 48 pedicles. The reliability of the funnel technique in placement of thoracic pedicle screws was proven in our cadaveric study. It provided even an entry-level surgeon with a safe way to identify and place thoracic pedicle screws. The funnel technique is a simple, safe, and cost-effective alternative to any other currently recommended techniques for pedicle screw placement.     

Dorsale operative Korrektur der idiopathischen Skoliose

Posterior correction and fusion of scoliosis with multisegmental instrumentation systems was developed by Cotrel-Dubousset in the 1980s. Initially correction and instrumentation was performed using hooks only. Later pedicle screws were implemented first for the lumbar and then for the thoracic spine. Nowadays instrumentation based on pedicle screws only is well established for posterior scoliosis surgery. Biomechanical studies demonstrated higher pull-out forces for pedicle than for hook constructs. In clinical studies several authors reported better Cobb angle correction of the primary and the secondary curves and less loss of correction in pedicle screw versus hook instrumentations. Furthermore, pedicle screw instrumentation allows fewer segments to be fused, especially caudally, and thus saving mobile segments. In most of these publications there were no differences in operation time, blood loss and complication rates. In summary, there is better curve correction without an increased risk using multisegmental pedicle screw instrumentation in modern posterior scoliosis surgery.