Application study of three-dimensional printed navigation template between traditional and novel cortical bone trajectory on osteoporosis lumbar spine

To investigate the safety, accuracy and indications of traditional and novel cortical bone screws placement for osteoporosis lumbar spine, 4 lumbar vertebra specimens (2 males and 2 females) were used for this study. After the computed tomography scanning data of the above anatomical specimens were three-dimensional (3D) reconstructed, one side of each anatomical specimen was randomly chosen to place traditional cortical bone screws, and the other side received novel technical placement. The safety screw trajectory was designed, and a 3D navigation template complementary to the surface anatomical structure of lumbar isthmus lateral margin-vertebral plate-spinous process part was established. The designed supporting navigation template was substantialized, and the navigation template replicated different cortical bone screw trajectory at different sides of the same one lumbar vertebra. Forty cortical bone screws were firstly placed in 3D printed vertebra and then 40 were placed in real anatomical specimens. In 3D printed specimens, the success rates of screw placement with navigation template using traditional and novel techniques were both 100%. While in anatomical specimens, the success rate of screw placement using traditional and novel navigation template was 97.5% (one out of 40 went wrong). Therefore, it is safe, accurate and reliable to place traditional and novel cortical bone screws on osteoporosis lumbar spine using 3D printed navigation template. Traditional and novel screw placement methods should be flexibly applied or combined according to specific sequence and form of vertebra.     

Protection of the C1 posterior arch in atlantal lateral mass fixation: technical case report.

Screw fixation of the C1 lateral mass is a relatively new technique designed to allow for C1/C2 fixation in scenarios where transarticular screw fixation is not safe or possible. In order to place the screw at the base of the C1 arch, it has been recommended to drill at the junction of the C1 posterior arch and the lateral mass of C1, to accommodate the screw head. This may, however, weaken the C1 arch, making it prone to fracture. In this new technique, we describe a modification to the current technique to allow placement of this screw without compromising the C1 arch. A case of atlantoaxial instability secondary to os odontoideum is described. C1 lateral mass fixation is achieved by selecting a screw 10 mm longer than required and placing the screw 10 mm above the bony entry point, for easier placement of the rod and avoidance of drilling at the base of the C1 arch. Adequate and safe C1/C2 fixation was achieved. Sublaminar wiring was performed around the C1 arch with no weakening or fracture of the arch. We believe that in order to place reasonable C1 lateral mass screws, it is inadvisable to drill the base of the junction between the C1 posterior arch and lateral mass as this may lead to arch weakening and failure. Easier instrumentation can be performed and the integrity of the C1 arch maintained using this alternate technique.     

The Clinical Experience of Computed Tomographic-Guided Navigation System in C1-2 Spine Instrumentation Surgery

Objective

To identify the accuracy and efficiency of the computed tomographic (CT)-based navigation system on upper cervical instrumentation, particularly C1 lateral mass and C2 pedicle screw fixation compared to previous reports.

Methods

Between May 2005 and March 2014, 25 patients underwent upper cervical instrumentation via a CT-based navigation system. Seven patients were excluded, while 18 patients were involved. There were 13 males and five females; resulting in four degenerative cervical diseases and 14 trauma cases. A CT-based navigation system and lateral fluoroscopy were used during the screw instrumentation procedure. Among the 58 screws inserted as C1-2 screws fixation, their precise positions were evaluated by postoperative CT scans and classified into three categories : in-pedicle, non-critical breach, and critical breach.

Results

Postoperatively, the precise positions of the C1-2 screws fixation were 81.1% (47/58), and 8.6% (5/58) were of non-critical breach, while 10.3% (6/58) were of critical breach. Most (5/6, 83.3%) of the critical breaches and all of non-critical breaches were observed in the C2 pedicle screws and there was only one case of a critical breach among the C1 lateral mass screws. There were three complications (two vertebral artery occlusions and a deep wound infection), but no postoperative instrument-related neurological deteriorations were seen, even in the critical breach cases.

Conclusion

Although CT-based navigation systems can result in a more precise procedure, there are still some problems at the upper cervical spine levels, where the anatomy is highly variable. Even though there were no catastrophic complications, more experience are needed for safer procedure.     

Hybrid lateral mass screw sublaminar wire construct: A salvage technique for posterior cervical fixation in pediatric spine surgery

We present a novel salvage technique for pediatric subaxial cervical spine fusion in which lateral mass screw fixation was not possible due to anatomic constraints. The case presentation details a 4-year-old patient with C5–C6 flexion/distraction injury with bilateral jumped facets. Posterior cervical fixation was attempted; however, lateral mass fracture occurred during placement of screws. Using a wire-screw construct, an attempt was made to provide stable fixation. The patient was followed post-operatively for assessment of outcomes. After the patient had progressive kyphosis following initial closed reduction and external orthosis, internal reduction with fusion/fixation was performed. Lateral mass fracture occurred during placement of lateral mass screws. After placement of a sub-laminar wire-lateral mass screw construct, intra-operative evaluation determined stability. Post-operatively, the procedure resulted in stable fixation with evidence of bony fusion on follow-up. Pediatric subaxial cervical spine instrumentation provides rigid fixation however is technically difficult due to anatomic and instrumentation related constraints. In the presented patient, the wire-screw construct resulted in stable fixation and bony fusion on follow-up. A modified sublaminar wire-lateral mass screw construct is an example of a salvage technique that provides immediate stability in the event of instrumentation related lateral mass fracture.     

First clinical experiences with a new cervical fixation device - technical report

In a first clinical series of ten patients the new cervical fixation device StarLock trade mark (Synthes, Umkirch, Germany) was implanted.[nl]Characteristics of the device are deep threaded screws with higher pullout resistance and a high angular tolerance while inserting the rods thus simplifying the implantation.[nl]62 lateral mass screws in ten patients were inserted. In 2 cases placement of screws was insufficient (3.2 %) because of surgical difficulties not attributable to the system technique.[nl]In all other cases a radiologically proven stabilization was created. [nl]Due to the high angular tolerance of the screw clamps bending of rods is simplified, especially in cases of longer constructs, and shortens the operation time.[nl]The design of the StarLock trade mark system allows an easy application of computer-navigated placing of transpedicular screws.[nl]This new cervical fixation device is easy to handle and simplifies rod application especially in longer constructs.     

术中CT导航在上颈椎螺钉固定手术中的应用

目的 为降低椎动脉、神经损伤和螺钉位置偏差等风险,探索应用术中CT实时导航技术完成上颈椎螺钉置入.方法 应用术中CT实时导航技术完成螺钉置入,9例患者中7例颅颈交界区畸形,1例C1～2巨大神经鞘瘤,1例C1～3椎板巨大血管性病变行上颈段螺钉固定,共置钉42枚.结果 根据Madawi定义的合理螺钉位置,9例共置钉42枚,位置满意,其中1例颅颈交界畸形患者二侧高跨椎动脉,1例-侧高跨椎动脉,共3枚C2螺钉为以往螺钉技术的相对禁忌证.所有患者无椎动脉、脊髓或神经损伤,没有穿破骨皮质,复位满意,固定牢靠.结论 使用术中CT三维影像实时导航,可以安全、准确地完成上颈段螺钉固定.

Abstract：

Objective For improvement of safety, avoiding the risk of injury of vertebral artery and nerve tissue, intraoperative CT guided placement of screws in upper cervical spine were performed.Methods Brain LAB Vector Vision system in conjunction with iCT were used for image guidance.42 screws were placed at C1, C2 levels using this technique in 9 patients, including 7 cases of craniovertebral junction malformation, 1 case of C1～2 giant schwannoma, and 1 case of C1-3 giant lamina vascular lesion.Results According to Madawi's definition of rational placement of screw, all 42 screws were placed satisfactorily.For 3 C2 screws, including 1 case of both side and 1 case of one side of high riding vertebral arteries, the placement of them was relative contraindication for traditional techniques.There was no injury of vertebral artery, spinal cord or nerves resulted from the placement of screws.There was no bony breach.Conclusions Intraoperative navigation by 3 -dimensional CT image guidance is helpful for safe and accurate placement of screws in upper cervical spine.     

Posterior thoracic segmental pedicle screw instrumentation: evolving methods of safe and effective placement

The use of pedicle screw instrumentation in the spine has evolved over the last two decades. The initial use of pedicle screws began in the lumbar spine. As surgeons have become more comfortable with the complex anatomy required for accurate screw placement, the use of pedicle instrumentation has evolved to include their use in the thoracolumbar and thoracic spine. The impetus behind their increased use is a result of the many advantages that pedicle screw anchorage offers over traditional hook and rod constructs. Improved deformity correction and overall construct rigidity are two important advantages of pedicle screw instrumentation due its three-column control over the spinal elements. First, pedicle screw instrumentation obviates the need to place instrumentation within the spinal canal with its inherent risk of neurologic injury. Second, the placement of pedicle screws is independent of facet or laminar integrity and thus has been extremely useful in traumatic, neoplastic, and degenerative conditions. The benefits of pedicle screws in the thoracic spine has been tempered by the potential for catastrophic neurological or soft tissue injuries due to the close proximity of these structures. The narrow and inconsistent shape of the thoracic pedicles, especially in spinal deformity, makes their placement technically challenging. As a result, surgeons have employed a number of techniques to ensure the safe and efficacious placement of thoracic pedicle screws. Detailed anatomic landmarks used to determine pedicle location, intraoperative imaging including navigation, and neurophysiological monitoring are some of the techniques currently used by surgeons. The implementation of these techniques and a thorough understanding of the complex three-dimensional anatomy have allowed surgeons to successfully place thoracic and thoracolumbar pedicle screws.     

CT navigated lateral interbody fusion

Lateral interbody fusion techniques are heavily reliant on fluoroscopy for retractor docking and graft placement, which expose both the patient and surgeon to high doses of radiation. Use of image-guided technologies with CT-based images, however, can eliminate this radiation exposure for the surgeon. We describe the surgical technique of performing lateral lumbar interbody fusion using CT navigation.     

Use of O-arm for spinal surgery in academic institution in India: experience from JPN apex trauma centre

There is a relatively high incidence of screw misplacement during spinal instrumentation due to distortion of normal anatomy following spinal trauma. The O-arm? is the next-generation spinal navigation tool that provides intraoperative 3-D imaging for complex spine surgeries. In this prospective study over 1-month period, 25 patients (mean age 29.16 years (range 7-58 years), 22 (88%) males) with spinal injury who underwent spinal instrumentation under O-arm? guidance were included. Fall from height (64%) was the most common etiology seen in 16 patients. The majority (68%) had dorsolumbar fractures. Spinal canal compromise was seen in 21 patients (84%). Ten patients (40%) had American Spinal Injury Association (ASIA) grade A injuries, two patients (8%) had grade B, five patients (20%) had grade C, four patients (16%) each had grade D, and grade E injuries. A total of 140 screws were inserted under O-arm guidance. Of these, 113 (81%) were dorsolumbar pedicle screws, 2 were odontoid screws, 12 were anterior cervical screws, and 12 screws (48%) were lateral mass screws. Mean duration of surgery was 4.5 h with a mean blood loss of 674 mL. The mean postoperative stay was 6.3 days. None of the patients had screw malplacement ort canal breach. No patient deteriorated in ASIA grade postoperatively. The system was rated as excellent for ease of use by all faculty using the system. Accurate screw placement provides better patient safety and reduces the in hospital stay thereby leading early patient mobilization and may reduce the cost incurred in patient management.     

Routine spinal navigation for thoraco–lumbar pedicle screw insertion using the O-arm three-dimensional imaging system improves placement accuracy

Modern image-guided spinal navigation employs high-quality intra-operative three dimensional (3D) images to improve the accuracy of spinal surgery. This study aimed to assess the accuracy of thoraco-lumbar pedicle screw insertion using the O-arm (Breakaway Imaging, LLC, Littleton, MA, USA) 3D imaging system. Ninety-two patients underwent insertion of thoraco–lumbar pedicle screws guided by O-arm navigation over a 27 month period. Intra-operative scans were retrospectively reviewed for pedicle breach. The operative time of patients where O-arm navigation was used was compared to a matched control group where fluoroscopy was used. A total of 467 pedicle screws were inserted. Four hundred and forty-five screws (95.3%) were placed within the pedicle without any breach (Gertzbein classification grade 0). Sixteen screws (3.4%) had a pedicle breach of less than 2 mm (Gertzbein classification grade 1), and six screws (1.3%) had a pedicle breach between 2 mm and 4 mm (Gertzbein classification grade 2). The grade 2 screws were revised intra-operatively. There was no incidence of neurovascular injury in this series of patients. The mean operative time for O-arm patients was 5.25 hours. In a matched control group of fluoroscopy patients, the mean operative time was 4.75 hours. The difference in the mean operative time between the two groups was not statistically significant (p = 0.15, paired t-test). Stereotactic navigation based on intra-operative O-arm 3D imaging resulted in high accuracy in thoraco–lumbar pedicle screw insertion.     

颅颈交界区后路螺钉内固定

目的 报告C2椎弓根螺钉结合C1侧块或枕骨螺钉用于颅颈交界区后路内固定的解剖研究及临床应用结果.方法 福尔马林固定的头颈标本4个,根据解剖标志分别植入C2椎弓根及C1侧块螺钉,然后行CT扫描及重建,观察螺钉位置.2004年5月至2007年1月,利用C2椎弓根一C1侧块/枕骨螺钉内同定9例病人,男4例,女5例,年龄12～68岁,平均38岁;各种原因引起的C1～C2半脱位6例,因颅底凹陷经口腔齿状突切除后1例,斜坡脊索瘤经口腔切除手术前2例;采用C2椎弓根-C1侧块螺钉技术4例,C2椎弓根一枕骨螺钉技术5例,手术后均行CT扫描观察螺钉位置.结果 手术中直接显露C2椎弓根内上缘,并以此确立进钉方向,在椎弓根峡部后缘确定进钉点,可保证C2椎弓根螺钉的安全植入;直接显露C1侧块后正中确立进钉点,可避免螺钉植入过程中的椎动脉损伤.9例病人中,手术后CT复查有2例病人两颗螺钉穿破骨皮质,但末造成血管及神经的压迫,其余螺钉位置均较好;随访4-32个月,1例临床症状较术前无变化,其余8例均改善.结论 C2椎弓根-C1侧块/枕骨螺钉技术可安全有效地用于颅颈交界区内固定.     

神经导航技术在脊柱固定手术中的应用(附16例报告)

目的探索使用神经导航技术进行脊柱内固定。方法在神经导航辅助下,对16例患者置入70根椎弓根(侧块)螺钉。通过术后X线摄片核实椎弓根螺钉置入的准确性。结果置入的70根椎弓根(侧块)螺钉长度和直径选择合适,其中68根(97·1%)固定位置及方向准确;早期曾有1根穿出至椎体前方(<1mm),未作处理;1根穿出至椎间盘,经翻修后固定情况良好。无神经和血管损伤症状。结论使用神经导航技术,可以前瞻性地判断置入椎弓根(侧块)钉的大小、位置,实时监测置入过程,提高置入的准确性和安全性。术中脊柱影像三维重建及注册配准对神经导航的准确性有较大影响。     

计算机导航辅助椎弓根螺钉固定的临床研究

目的椎弓根螺钉固定是脊柱病变切除后稳定性重建的标准方法。常规术中透视监测行颈胸节段椎弓根螺钉固定具有相当挑战性,本文旨在就计算机导航辅助椎弓根螺钉固定技术进行初步分析。方法2005年1月至2006年3月在计算机导航系统辅助下,对21例患者（年龄17～63岁,平均43．4岁）共行102枚椎弓根螺钉固定。术前采用0．75mm薄层螺旋CT数据扫描并导入计算机工作站进行脊柱三维重建;术中进行工具注册和匹配后对椎弓根螺钉固定进行实时显示。术后所有病例均采用CT和X线平片随访监测效果。结果手术顺利,螺钉大小选择合适,102枚椎弓根螺钉中100枚螺钉（98%）固定位置及方向准确,2枚椎弓根螺钉突破椎弓根外壁距离小于2mm。所有操作均未发生血管和神经损伤并发症。术中透视次数及手术室人员所受X线辐射量明显减少。结论计算机导航辅助椎弓根螺钉固定是一项安全的手术,且手术精度高。     

New generation intraoperative three-dimensional imaging (O-arm) in 100 spine surgeries: Does it change the surgical procedure?

The O-arm (Medtronic Sofamor Danek, Inc., Memphis, TN, USA), an intraoperative CT scan imaging system, may provide high-quality imaging information to the surgeon. To our knowledge, its impact on spine surgery has not been studied. We reviewed 100 consecutive spine surgical procedures which utilized the new generation mobile intraoperative CT imaging system (O-arm). The most common diagnoses were degenerative conditions (disk disease, spondylolisthesis, stenosis and acquired kyphosis), seen in 49 patients. The most common indication for imaging was spinal instrumentation in 81 patients (74 utilized pedicle screws). In 52 (70%) of these, the O-arm was used to assess screw position after placement; in 22 (30%), it was coupled with Stealth navigation (Medtronic Sofamor Danek, Inc.) to guide screw placement. Another indication was to assess adequacy of spinal decompression in 38 patients; in 19 (50%) of these, intrathecal contrast material was used to obtain an intraoperative CT myelogram. In 20 patients O-arm findings led to direct surgeon intervention in the form of screw removal/repositioning (n = 13), further decompression (n = 6), interbody spacer repositioning (n = 1), and removal of kyphoplasty trocar (n = 1). In 20% of spine surgeries, the procedure was changed based on O-arm imaging findings. We found the O-arm to be useful for assessment of instrumentation position, adequacy of spinal decompression, and confirmation of balloon containment and cement filling in kyphoplasty. When used with navigation for image-guided surgery, it obviated the need for registration.     

Techniques in the treatment of craniovertebral instability

The techniques of craniovertebral region stabilization introduced and used by the senior author over the last 20 years are summarized. The lateral masses of atlas and axis are strong and largely cancellous in nature and can be used for direct implantation of screws. Opening up of the joint and placement of bone graft within the joint stabilizes the region and provides a large area for bone fusion. Distraction of the facets provides an opportunity to treat a range of congenital craniovertebral anomalies. The technique of exposure of the lateral mass of the atlas and axis and the atlantoaxial joint is technically relatively complex and needs precise understanding of anatomy of the vertebral artery and training with cadavers.     

Screw fixation of craniocervical junction

In recent years an increase has been observed of the use of screw techniques for the fixation of the craniocervical junction. For clinical use two techniques have been introduced: (1) transarticular screw fixation, and (2) transpedicular screw fixation. In the former the screw is inserted through the C2 lateral mass, the fissure of the C1-C2 joint, and the C1 lateral mass. (2) in the latter the screw is inserted into the C2 pedicle and anchored in C2 vertebral body. Transarticular or pedicle screws can be easily connected to longitudinal elements such as rods or plates, and combined with lateral mass screws of the remaining cervical vertebrae or occipital screws. In comparison to sublaminar wiring or interlaminar clamping the screw techniques: (a) strengthen the stiffness of the construct and speed up fusion, (b) allow fixation in the absence or deficiency of laminae as a result of trauma or laminectomy, and (c) can selectively include only the affected segments. Increased construct stiffness is due to deep anchorage of the screw in bone providing thus a solid grip on the vertebra. Both techniques require preoperative assessment of the course of the vertebral artery using imaging methods. In about 18% of cases abnormal course of the artery precludes screw use. Pedicle screw insertion requires direct control of the medial and superior walls of C2 pedicle with dissector introduced into the vertebral canal, which requires removal of the atlantoaxial ligament. Additional control can be achieved with lateral fluoroscopy. The entry point for transarticular screw is on the lateral mass of the odontoid 2-3 mm laterally to the medial margin of C2 facet and 2-3 mm above the C1/C2 articular fissure. The screw trajectory is 0-10 degrees in horizontal plane and towards the anterior C1 tuberculum in sagittal plane.     

Accuracy of Pedicle Screw Insertion Using Fluoroscopy-Based Navigation-Assisted Surgery : Computed Tomography Postoperative Assessment in 96 Consecutive Patients

Objective

Two-dimensional fluoroscopy-based computerized navigation for the placement of pedicle screws offers the advantage of using stored patient-specific imaging data in providing real-time guidance during screw placement. The study aimed to describe the accuracy and reliability of a fluoroscopy-based navigation system for pedicle screw insertion.

Methods

A total of 477 pedicle screws were inserted in the lower back of 96 consecutive patients between October 2007 and June 2012 using fluoroscopy-based computer-assisted surgery. The accuracy of screw placement was evaluated using a sophisticated computed tomography protocol.

Results

Of the 477 pedicle screws, 461 (96.7%) were judged to be inserted correctly. Frank screw misplacement [16 screws (3.3%)] was observed in 15 patients. Of these, 8 were classified as minimally misplaced (≤2 mm); 3, as moderately misplaced (2.1-4 mm); and 5, as severely misplaced (>4 mm). No complications, including nerve root injury, cerebrospinal fluid leakage, or internal organ injury, were observed in any of the patients.

Conclusion

The accuracy of pedicle screw placement using a fluoroscopy-based computer navigation system was observed to be superior to that obtained with conventional techniques.     

Image-guided pedicle screws using intraoperative cone-beam CT and navigation. A cost-effectiveness study

Image-guided surgery using intraoperative cone-beam CT and navigation improves screw placement accuracy rates. However, this technology is associated with high acquisition costs. The aim of this study is to evaluate the costs of revision surgery from symptomatic pedicle screw malposition to justify whether the costs of acquiring intraoperative navigation justify the expected benefits. This is a retrospective cost-effectiveness analysis of consecutive patients who had pedicle screw instrumentation using intraoperative cone-beam CT and navigation compared with patients who underwent freehand pedicle screw instrumentation at our institution over 4 years. The costs associated with revision surgery for symptomatic pedicle screw malposition (excess length of stay, intensive care, theatre time, implants and additional outpatient appointments) were calculated. A total of 19 patients had symptomatic screw malpositioning requiring revision surgery. None of these patients had screws inserted under navigation. Revision surgery accounted for an extra 304 bed days and an additional 97 h theatre time. The total extra spent over 4 years was £464,038. When compared to the costs of revision surgery for screw malpositioning, it was cost neutral to acquire and maintain this technology. Intraoperative image-guided surgery reduces reoperation rates for symptomatic screw malposition and is cost-effective in high volume centers with improved patients outcomes. High acquisition and maintenance cost of such technologies is economically justifiable.     

True accuracy of percutaneous pedicle screw placement in thoracic and lumbar spinal fixation with a CT-based navigation system: Intraoperative and postoperative assessment of 763 percutaneous pedicle screws

PurposeTo investigate intraoperative reinsertion of percutaneous pedicle screw (PPS) with intraoperative CT-based navigation and to evaluate the rate of deviation of PPS at postoperative radiographic examination.MethodsSeven hundred sixty-three screws were inserted in 138 patients. We investigated the rate of occurrence of intraoperative PPS reinsertion after the diagnosis of screw deviation by fluoroscopy and the causes of each screw deviation. The subsequent distribution of PPS deviation was evaluated by postoperative CT. We also assess the difference in variance between the group judged to be PPS misplaced intra-/postoperatively (IOD group/POD group) and appropriate PPS placement (ND group).ResultsAmong all the screws inserted, 10 (1.3%) were diagnosed as being deviated by fluoroscopy during surgery, and 74 (9.7%) screws were found to be deviated at postoperative CT evaluation. We found more pedicle screw mismatch in the POD group than in the ND group (52.7 vs 11.0%, P < 0.001). The distance between the screw and the reference was greater in the IOD group than that in the ND group (1.4 ± 1.2 vs 2.4 ± 1.1 vertebral levels, P = 0.016). In one patient in the IOD group, a motor function deficit was observed postoperatively.ConclusionPPS fixation under intraoperative CT-based navigation did not prevent screw deviation completely. It is necessary to consider errors that occur during surgery and to confirm placement with real-time assistance such as fluoroscopy even in a surgery performed under CT navigation assistance.     

Accuracy and safety of cortical bone trajectory screw placement by an inexperienced surgeon using 3D patient-specific guides for transforaminal lumbar interbody fusion

Cortical bone trajectory (CBT) is an alternative method for pedicle screw insertion. However, identification of the optimal entry point and the direction of the CBT can be challenging for less-experienced surgeons. The purpose of this study was to evaluate the accuracy of the CBT screw placement by an inexperienced surgeon using a three-dimensional (3D) patient-specific guide for transforaminal lumbar interbody fusion (TLIF). Retrospective analysis of the data pertaining to 30 patients (128 screws) who underwent TLIF with CBT by an inexperienced surgeon using a 3D patient-specific guide (MySpine MC, Medacta) at a single center was performed. The accuracy of the CBT screw was graded into four groups (no perforation; Grade A, 0–2 mm; Grade B, 2–4 mm; and Grade C, > 4 mm). The accuracy of the CBT screw placement was 91% (116/128). Out of the 12 misplaced screws, Grade A was observed in 7 screws (5%), Grade B was observed in 3 screws (2%), and Grade C was observed in 2 screws (2%). There were no cases of medial pedicle wall perforation. The mean screw size was 5.95 ± 0.34 mm in diameter and 40.15 ± 2.83 mm in length. Note that, the accuracy of the CBT screws increased to 97% (83/86) over the first10 cases. Preoperative planning and 3D patient-specific guide enabled the use of longer and thicker screws and an optimal entry point. These results suggest the possibility of efficacy and safety in using 3D patient-specific guides for CBT screw placement by an inexperienced surgeon.