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Shao-Jie Zhang,1,2,&ast; Kun Li,2,3,&ast; Zhi-Jun Li,2,3 Xing Wang,2,3 Jia-Hui Dong,4 Jian Wang,2 Jie Chen,2 Xing-Yue Qu,2 Zi-Yu Li,2 Yu-Hang Liu2 1School of Traditional Chinese Medicine, Beijing University of Chinese Medicine, Beijing, People’s Republic of China; 2Department of Human Anatomy, Inner Mongolia Medical University, Hohhot, People’s Republic of China; 3Digital Medical Center, Inner Mongolia Medical University, Hohhot, People’s Republic of China; 4The First Clinical Medical College, Inner Mongolia Medical University, Hohhot, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Zhi-Jun LiDepartment of Human Anatomy, Inner Mongolia Medical University, Hohhot, People’s Republic of ChinaTel +86 471-6636945Email zjl06_master@126.comObjective: This study aimed to investigate the safety of clival screw placement in children aged 1– 6 years.Methods: The cranial computed tomography data of 92 children aged 1– 6 years were divided into three groups, according to age, for three-dimensional reconstruction. Three clival screw placement points were defined: (1) median point A at the middle and upper third of the tripartite distance from the spheno-occipital synchondrosis to the base of the skull; (2, 3) critical points B and C on the horizontal line with point A, where the screw placement passage was parallel to the sagittal plane. Parameters such as the passage length and angle were measured for horizontal, vertical facial, and extreme screw placement.Results: The length parameters of the clival screw placement increased with age, and the screw passage length was the shortest for the vertical facial type in each age group. There were significant differences in all three groups between the length of screw placement in the vertical bone surface, the length of screw placement in the horizontal direction, and the length of screw placement on the limit at points A, B, and C (P < 0.05); the length of screw placement on the vertical bone surface was the shortest. There was no significant difference between the horizontal screw length at point A and the extreme screw length (P > 0.05). The difference between the horizontal screw length and the extreme screw length in the groups aged 1– 2 years and 5– 6 years was statistically significant (P < 0.05), and the horizontal screw length was longer.Conclusion: The cranial slope of children aged 1– 6 years has the morphological basis for the placement of 3.5 mm screws, and each placement point has a safe angle range for screw placement.Keywords: children, craniocervical junction region, clivus, internal screw fixation, spiral computed tomography scan

Robotic-navigated screw placement has potential for higher precision and accuracy. Robotic assistance is well-described in the lumbar spine, however only few studies have evaluated its use in the cervical spine. Surgical treatment for hangman’s fractures after nonunion typically involves C2-3 anterior fusion or posterior occipito-cervical fusion. However, occipito-cervical fusion involves loss of mobility in the cervical spine with associated morbidity. We have previously described a minimally invasive approach using percutaneous screw fixation with X-ray navigation. Robotic assistance is ideally suited for cervical fusion given smaller bony anatomy and adjacent critical structures. We describe a young healthy patient who presented with a hangman’s fracture initially managed conservatively with immobilization. She presented with nonunion and persistent symptoms. Surgical options considered included anterior cervical discectomy and fusion, or posterior cervical fusion with or without extension to the occiput. These options would have involved some loss of flexion/extension and rotational motion with associated morbidity. We performed percutaneous screw fixation of the hangman’s fracture using MAZOR-X robotic navigation and achieved good radiographic fracture reduction with accurate screw placement. To our knowledge this is the first case of a robotic-assisted percutaneous screw fixation for a hangman’s fracture. Robotic-navigated screw placement can be used safely and accurately for cervical spine fractures.

Background The use of transacetabular screws aid greatly in attaining acetabular component stability during acetabular revision surgery. There are, however, definite risks involved when using this technique. Inserting screws in the posterior superior safe zone has been advocated as a way to do this safely, but recent studies have shown that this does not hold true in conditions where acetabular anatomy is distorted or where the hip centre of rotation has moved. A method to insert these screws more accurately and safely is proposed. Questions/Purposes (1) Can using the greater sciatic notch as reference point when inserting transacetabular screws for revision acetabular cups ensure accurate and safe placement of screws? (2) How does this proposed new method compare with the posterior superior safe zone method? Methods With the use of an observational anatomic study we have developed a new method for the insertion of long transacetabular screws. This method uses the greater sciatic notch as a reference point. Our method was tested on 16 cadaveric hips (reamed to simulate revision conditions) and compared to the safe zone method. Results Our method achieved placement of 1–3 screws in the target area in all hips without penetration into the pelvis or sciatic notch. With the use of the safe zone only as reference the pelvis was penetrated 7 times and the sciatic notch twice. Conclusion Using the greater sciatic notch as a reference guide enables the surgeon to engage a supportive bar of bone for one or more long home run screws whilst minimizing penetration of the pelvis and sciatic notch. In this study our method was superior to using the safe zone in isolation.

BACKGROUND: Numerous techniques of C1 lateral mass screw placement have been described. We sought to delineate the radiographic angle of safety medially and laterally and describe a novel surgical technique of C1 lateral mass screw placement. We sought to (I) determine the angle of safety medially and laterally of the C1 lateral mass; (II) assess the size available of the lateral mass in the AP and coronal planes; (III) describe novel technique of insertion of a C1 lateral mass screw utilizing navigation and a novel start point. METHODS: We retrospectively reviewed cervical computed tomography (CT) images of normal adults. Radiographic measurements were then obtained using these images including the angle (degrees) of safety medially and lateral of the C1 lateral mass bilaterally, as well as the length and width (mm) of the C1 lateral masses. A novel surgical technique was used by identifying the confluence of the medial aspect of the posterior arch and the lateral mass. This confluence is then marked out as the C1 screw start point. Under navigation guidance, lateral mass screws were placed with 0 degrees of medial-lateral angulation from posterior to anterior. RESULTS: Forty-five patients with a mean age of 52.6±25.6 years (33% female) were included. The mean medial and lateral angle of safety of the C1 lateral mass bilaterally was 23±3.8 degrees and 32±5 degrees, respectively. Average length and width of the lateral mass was 17.7 and 13.3 mm respectively. CONCLUSIONS: This study describes the radiographic window of safety medially and laterally for safe and reproducible placement of C1 lateral mass screws. Further, a novel technique using a medial start point and navigation guidance with 0 degrees of angulation in the coronal plane is described. Further research is required to assess outcomes of patients utilizing this method as well as biomechanical studies to assess this construct strength compared to others that are frequently used.

Background This study describes a modified iliac screw technique and compares it with the traditional iliac screw in regard to neurovascular structures at risk. Few studies have detailed the insertion point's surrounding anatomy and its relationship to vulnerable neurovascular structures when this modified technique is used. Therefore we describe our modified iliac screw entry and trajectory and detail the surrounding anatomy and neurovascular structures at risk with this technique in comparison with the “gold standard” trajectory. Methods The traditional iliac screw (TS) and modified iliac screw (MS) were placed into 12 fresh-frozen adult cadavers (3 female, 9 male). We measured the screw-to−supragluteal artery, vein, and nerve (SGANV) bundle and screw-to−sciatic notch distances. Further, we dissected the medial cortical border of the iliac screw to identify its final position with respect to the surrounding anatomy. Results No medial or lateral cortical breaches were visualized after screw placement. The MS was 18.31 mm from the greater sciatic foramen compared with 18.65 mm with the TS. The smallest distance from the MS to the greater sciatic foramen was 13.9 mm compared with 14.8 mm with the TS, an insignificant difference. The SGANV bundle−to-MS distance was 20.6 mm, and SGANV bundle−to-TS distance was 20.77 mm, again an insignificant difference. Conclusions Using the modified iliac screw technique does not change the intraosseous pathway (and thus bone purchase) with respect to the distance between the screw and neurovascular structures at risk.

Objective To compare the incidence and risk factors of superior facet joint violation (FJV) during cortical bone trajectory screw placement in robot‐assisted approach versus conventional technique. Methods A retrospective study, including 69 patients having cortical bone trajectory (CBT) screw instrumentation for symptomatic degenerated diseases or trauma, was conducted between June 2015 to January 2019. All patients underwent CBT surgery performed by the same team of experienced surgeons. Patients were randomly divided into two groups: a conventional group (CG, 46 cases) and a robot group (RG, 23 cases). The surgical robotic system was used for screw instrumentation in the robot group and the traditional screw instrumentation with fluoroscopic guidance was used in the conventional group. Cortical screws followed a medio‐to‐lateral path in the transverse plane and a caudal‐to‐cephalad path in the sagittal plane. Preoperative and postoperative computed tomography (CT) scans were obtained to determine the degree and incidence of FJV. The violation status of facet joint was evaluated according to the modified classification: grade 0, no violation; grade 1, screw shaft, screw head or rod within 1 mm of or abutting the facet joint, but did not enter the articular facet joint; grade 2, screw shaft, screw head or rod clearly in the facet joint. The following factors that may contribute to the occurrence of FJV were analyzed: age, sex, body mass index (BMI), proximal fusion level, fusion length, the side of screw, preoperative vertebral slip, superior facet angle, and degenerative scoliosis. The chi‐squared test and Student's t‐test were used for analysis of the variables for significance (P

Objectives To map the proximal ulnar articular margins and ensure safe extraarticular placement of implants. Methods Ten fresh frozen adult elbow cadaver specimens were obtained. Radiopaque wire was applied to the articular margin of the articular facets and the central trochlear ridge of the proximal ulna. Fluoroscopic images were obtained demonstrating the articular facet margins. Radiographic measurements were performed and used to identify relative safe screw zones. Results All specimens demonstrated marked extension of the ulnar and radial facets dorsal to the central trochlear ridge. The dorsal extent of the ulnar facets from the central trochlear ridge averaged 9.7 mm (range, 7.9-13 mm; SD, 1.5 mm) and 6.2 mm (range, 3.4-9.4 mm; SD, 1.9 mm), respectively. The average footprint of the posterior ulnar facet occupied 44% (±4.9%) of the total ulnar height from the dorsal cortex to the trochlear ridge. Conclusions The articular margins of the anterior and posterior facets of the proximal ulna are challenging to identify radiographically. A surgical "at-risk zone" exists within 9.7 mm from the radiographic margin of the central trochlear ridge. Implants placed within this zone have the potential to violate the articular surface.

Spine surgery has evolved from the advent of imaging and navigation guidance, particularly with the rise of robotic surgical assistance. Navigation guidance has demonstrated potential for increased accuracy of transpedicular screw placement and resecting primary and metastatic spinal tumors. Robotic surgery is widely accepted in other surgical fields because laparoscopic techniques applied to robots can increase operator dexterity and improve visualization. Robotic assistance with spinal tumors has enjoyed rising interest owing to the potential for safe and minimally traumatic resection. We discuss available robots used for navigation-guided transpedicular screw placement and state-of-the-art robotic techniques for spinal or paraspinal tumor resection.

Study design Prospective observational study. Objective To assess staff and patient radiation exposure during augmented reality surgical navigation in spine surgery. Summary of background data Surgical navigation in combination with intraoperative three-dimensional imaging has been shown to significantly increase the clinical accuracy of pedicle screw placement. Although this technique may increase the total radiation exposure compared with fluoroscopy, the occupational exposure can be minimized, as navigation is radiation free and staff can be positioned behind protective shielding during three-dimensional imaging. The patient radiation exposure during treatment and verification of pedicle screw positions can also be reduced. Methods Twenty patients undergoing spine surgery with pedicle screw placement were included in the study. The staff radiation exposure was measured using real-time active personnel dosimeters and was further compared with measurements using a reference dosimeter attached to the C-arm (i.e., a worst-case staff exposure situation). The patient radiation exposures were recorded, and effective doses (ED) were determined. Results The average staff exposure per procedure was 0.21 ± 0.06 μSv. The average staff-to-reference dose ratio per procedure was 0.05% and decreased to less than 0.01% after a few procedures had been performed. The average patient ED was 15.8 ± 1.8 mSv which mainly correlated with the number of vertebrae treated and the number of cone-beam computed tomography acquisitions performed. A low-dose protocol used for the final 10 procedures yielded a 32% ED reduction per spinal level treated. Conclusion This study demonstrated significantly lower occupational doses compared with values reported in the literature. Real-time active personnel dosimeters contributed to a fast optimization and adoption of protective measures throughout the study. Even though our data include both cone-beam computed tomography for navigation planning and intraoperative screw placement verification, we find low patient radiation exposure levels compared with published data. Level of evidence 3.

Objective: The objective of this study is to compare the clinical efficacy of O-arm navigation and microscope-assisted minimally invasive transforaminal lumbar interbody fusion (modified MIS-TLIF) versus conventional TLIF in the lumbar isthmic spondylolisthesis. Materials and methods: Forty patients with 1-level lumbar isthmic spondylolisthesis were enrolled in the study. Perioperative indexes including operation time, intraoperative bleeding, bed rest time, time of hospitalisation stay and the accuracy rate of screw placement were analysed. Preoperative and postoperative visual analogue scale (VAS) and Oswestry disability index (ODI) were assessed. Results: The operation time in the modified MIS-TLIF group was longer than the conventional TLIF group (p ​ ​0.05). Conclusion: Navigation and microscope-assisted MIS-TLIF is safe and reliable for treatment of lumbar isthmic spondylolisthesis (Meyerding degree I or II) with potential advantages including less injury, less blood loss, higher screw accuracy and faster recovery after operation. The translational potential of this article: Compared with conventional transforaminal lumbar interbody fusion, O-arm navigation and microscope-assisted minimally invasive transforaminal lumbar interbody fusion has a huge advantage in surgery treatment of lumbar isthmic spondylolisthesis. Hence, this article provided a better surgery method to deal with lumbar isthmic spondylolisthesis, and robot-assisted minimally invasive transforaminal lumbar interbody fusion will be adopted in the future. Keywords: Microscope, O-arm, Transforaminal lumbar interbody fusion, Navigation, Minimally invasive transforaminal lumbar interbody fusion, Lumbar isthmic spondylolisthesis

strongBACKGROUND/strongSince C2 is adjacent to important nerves and blood vessels, the implantation risk of C2 internal fixation in this area is high and requires high accuracy. This study mainly discussed the application value of 3-dimensional (3D)-printed navigation template in C2 screw placement.strongMATERIAL AND METHODS/strongA retrospective study compared 3D-printed navigation template-assisted screw placement (group A, n=32) and the C-arm based navigation-assisted screw placement group (group B, n=32). Group A was divided into 2 subgroups: A1 (C2 pedicle screw placement) and A2 (C2 pars screw placement); group B was divided into B1 (C2 pedicle screw placement) and B2 (C2 pars screw placement). The accuracy and safety of screw placement and clinical outcomes were evaluated.strongRESULTS/strongThere were 64 C2 screws placed in group A, and 95.31% achieved a grade A accuracy rating, including 52 screws in group A1 (96.15% grade A) and 12 screws in group A2 (91.67% grade A). A total of 64 C2 screws were placed in group B, and 84.38% achieved a grade A accuracy rating, including 50 screws in group B1 (84.00% grade A) and 14 screws in group B2 (85.71% grade A). The accuracy of screw placement differed significantly between groups A and B (iP/i=0.041) and between groups A1 and B1 (iP/i=0.039) but not between groups A2 and B2 (iP/i=0.636). The postoperative efficacy of the 2 groups was satisfactory. And there were no complications of blood vessels or nerves related to screw placement in either group.strongCONCLUSIONS/strongAlthough 3D-printed navigation template-assisted and C-arm based navigation-assisted C2 pedicle and pars screw placement provided similar safety and clinical efficacy, 3D-printed navigation template technology achieved more accurate C2 pedicle screw placement.

Objective. To perform comparative analysis of safety and accuracy of pedicle screw placement in the cervical and thoracic vertebrae using custom-made 3D-printed navigation templates of various designs. Material and Methods . The study was performed on three cadaver preparations. A total of 60 pedicle screws were placed in C2–T4 using navigation templates of different designs. Three types of templates were used to install 20 screws in each group: monolateral templates in group A, bilateral templates in group B, and bilateral three-point templates supported by the spinous process in group C. The safety and accuracy of screw placement were evaluated by CT with following comparative evaluation. Results. Three-point templates (group C) demonstrated the highest implantation safety, only one screw (5 %) perforated pedicle’s wall with grade 1, 19 screws (95 %) were completely surrounded by bone tissue. In group A, three screws (15%) were placed with grade 1, two screws (10 %) with grade 2, and one screw (5 %) with grade 3. In group B, two screws (10 %) were placed with grade 1, and one screw (5 %) – with grade 2.The average deviation at the screw entry point was 5.0 ± 0.5 mm in group A, 1.7 ± 0.3 mm in group B, and 0.35 ± 0.05 mm in group C. The average deviation at the end point was 5.1 ± 0.7 mm in group A, 3.5 ± 0.6 mm in group B, and 0.53 ± 0.05 mm in group C. Differences between groups in terms of implantation safety and accuracy are statistically significant (p < 0.05). Conclusion. Bilateral three-point navigation templates supported by spinous process are recommended for pedicle screw placement in the cervical and thoracic spine.

Background: Cortical bone trajectory (CBT) screws have been recently described as a method of lumbosacral fixation. These screws are typically inserted under fluoroscopic guidance with a medial-to-lateral trajectory in the axial plane and a caudal-to-cephalad trajectory in the sagittal plane. In an effort to reduce surgeon radiation exposure and improve accuracy, CBT screws may be inserted under navigation with intraoperative cone beam computed tomography (CT). However, the accuracy of CBT screw placement under intraoperative navigation has yet to be assessed in the literature. The purpose of the study was to evaluate the accuracy of CBT screw placement using intraoperative cone beam CT navigation. Methods: One hundred and thirty-four consecutive patients who underwent CBT fixation with 618 screws under intraoperative navigation were analyzed from May 2016 through May 2018. Screws were placed by one of three senior spine surgeons using the Medtronic O-Arm Stealth Navigation. Screw position and accuracy were assessed on intraoperative and postoperative CT scans using 2D and 3D reconstructions with VitreaCore software. Results: The majority of surgeries were primary cases (73.1%). The mean age at the time of surgery was 61.5±10.0 years and the majority of patients were female (61.2%). Most patients underwent surgery for a diagnosis of degenerative spondylolisthesis (47.8%) followed by mechanical collapse with foraminal stenosis (22.4%). Ten violations of the vertebral cortex were noted with an average breach distance of 1.0±0.7 mm. Three breaches were lateral (0.5%) and seven were medial (1.1%). The overall navigated screw accuracy rate was 98.3%. The accuracy to within 1 mm of error was 99.2%. There were no intra-operative neurologic, vascular, or visceral complications related to the placement of the CBT screws. Conclusions: CBT screw fixation under an intraoperative cone beam CT navigated insertion technique is safe and reliable. Despite five breaches greater than 1mm, there were no complications related to the placement of the CBT screws in this series.

Background Exact knowledge of the sacral anatomy is crucial for the percutaneous insertion of iliosacral screws. However, dysplastic anatomical patterns are common. In addition to a preoperative computed tomography (CT) analysis, conventional radiographic measures may help to identify upper sacral dysplasia and to avoid damage to surrounding structures. Aiming to further increase safety in percutaneous iliosacral screw placement in the presence of sacral dysmorphism, this study examined the prevalence of previously established radiographic signs and, in addition, defined the “critical SI angle” as a new radiographic criterion. Methods Pelvic CT scans of 98 consecutive trauma patients were analysed. Next to assessment of established signs indicating upper sacral dysplasia, the critical sacroiliac (SI) angle was defined in standardized pelvic outlet views. Results The critical SI angle significantly correlates with the presence of mammillary bodies and an intraarticular vacuum phenomenon. With a cut-off value of − 14.2°, the critical SI angle detects the feasibility of a safe iliosacral screw insertion in pelvic outlet views with a sensitivity of 85.9% and a specificity of 85.7%. Conclusions The critical SI angle can support the decision-making when planning iliosacral screw fixation. The clinical value of the established signs of upper sacral dysplasia remains uncertain.

Percutaneous pedicle screws have been used in the treatment of thoracolumbar fractures for decades, and conventional fluoroscopy is commonly used to confirm the positions of the Jamshidi needles during the procedure. In this article, a modified method is reported for the placement of Jamshidi needles. The attending surgeons did not receive any radiation during the procedure and the fluoroscopy time for the patients was little. In our method, all six Jamshidi needles were placed on the pedicles and hammered 2 mm into each entry site. When the verification images were acquired, the medical personnel went behind a lead-lined wall. The positions of the needles were first reviewed and adjusted as needed based on the anterior-posterior (AP) image. Then, the C-arm was rotated and lateral images were obtained to further verify the needle placement. The rest of the screw placement procedure remained the same. The proposed technique was applied in 45 patients with thoracolumbar fractures. It took an average (range) of 5 (4–7) single-shot images to ensure all the needles were positioned at the ideal entry site and 12 (10–17) minutes to complete this step. No neurological symptoms were reported by the patients. Using the proposed technique, the radiation exposure for the surgeons is zero, and the patients are well-protected from excessive radiation exposure. This modified method of embedding all the Jamshidi needles at the entry sites before fluoroscopy is an improved technique compared with the conventional method.

Transpedicular screw fixation is the most established means to stabilize the spine. Present study evaluates personalized navigation templates application for vertebral pedicle passage. Navigation templates were used for inserting 35 transpedicular screws in 5 patients with spinal deformity (age 2–16). Each patient underwent computed tomography preoperatively. Acquired data was processed into a virtual 3d-model of target zone. Life size virtual pedicular probes were placed onto transpedicular trajectories determined on multiplanar cross-sections of the model. Navigation template was created by modification and union of geometric primitives. Target zone model and navigation template were made with PLA by 3D-printer. In surgery the template was placed on skeletonized posterior surface of appropriate vertebrae. After confirmation of template stability trajectories were passed to a depth of 20 mm through guiding tubes by pedicular probe. Resulting channels were controlled with ball tip feeler, and the full depth trajectories were made by free hand technique. Postoperatively screws placement accuracy was assessed by plain X-rays in each patient. Two patients (16 screws) also underwent computed tomography. In these patients screw placement accuracy was assessed by system based on 2 mm breach increments. 15 screws (93. 7%) were fully contained within the pedicle (grade 0), 1 screw breached external cortex of the pedicle by 0. 8 mm (grade 1). Efficacy and safety of navigation template for transpedicular screws insertion was demonstrated.

Computer-aided navigation and robotic guidance systems have become widespread in their utilization for spine surgery. A recent innovation combines these two advances, which theoretically provides accuracy in spinal screw placement. This study describes the cortical and pedicle screw accuracy for the first 54 cases where navigated robotic assistance was used in a surgical setting. This is a retrospective chart review of the initial 54 patients undergoing spine surgery with pedicle and cortical screws using robotic guidance with navigation. A computed tomography (CT)-based Gertzbein and Robbins System (GRS) was used to classify pedicle screw accuracy. Screw tip, tail, and angulation offsets were measured using image overlay analysis. Screw malposition, reposition, and return to operating room rates were collected. 1 of the first 54 cases was a revision surgery and was excluded from the study. Ten screws were placed without the robot due to surgeon discretion and were excluded for the data analysis of 292 screws. Only 0.68% (2/292) of the robot-assisted screws was repositioned based on surgeon discretion. Based on the GRS CT-based grading, 98.3% (287/292) were graded A or B, 1.0% (3/292) screws were graded C, and only 0.7% (2/292) screws was graded D. The average offset from preoperative plan to actual final placement was 1.9 mm from the tip, 2.3 mm from the tail, and 2.8° of angulation. In the first 53 cases, 292 screws placed with navigated robotic assistance resulted in a high level of accuracy (98.3%), adequate screw offsets from planned trajectory, and zero complications.

Most minimally displaced scaphoid fractures and all displaced scaphoid fractures in elite athletes are treated with early fixation to maximally expedite the return to full function. Computed tomographic (CT) scans are recommended in all scaphoid fractures to facilitate a complete understanding of fracture anatomy and to allow for optimal screw placement. Screw placement is important to maximize healing capacity of the fracture and allow for return to sport. Postoperative CT scans can be helpful to evaluate the extent of healing and may allow patients to return to play sooner.

In the emerging field of robot-assisted spine surgery, the radiographic evaluation of pedicle screw accuracy in clinical application is an area of high interest. This study describes the pedicle screw accuracy of the first 56 consecutive cases in which navigated robotic assistance was used in a private practice clinical setting. A retrospective, Institutional Review Board-exempt review of the first 56 navigated robot-assisted spine surgery cases was performed. Pedicle screw malposition, reposition, and return to operating room (OR) rates were collected. A CT-based Gertzbein and Robbins system (GRS) was used to classify pedicle screw accuracy. In the first 56 robotic cases, 356 total pedicle screws were placed. Eight screws were placed without the robot due to surgeon discretion. Of the 348 pedicle screws inserted by navigated robotic guidance, only 2.6% (9/348) were repositioned, resulting in a 97.4% (339/348) successful screw placement rate. The average age was 64, and 48% were female. Average body mass index was 31 kg/m2. Based on the GRS CT-based grading, 97.7% (340/348) were graded A or B, 1.7% (6/348) screws were graded C, and only 0.6% (2/348) of screws were graded D. Two complications, explantation of interbody and vacuum-assisted wound closure, were reported as requiring a return to the OR, but these were not related to robotic guidance or pedicle screws. This study demonstrated a high level of accuracy (97.7%) in the first 56 cases using navigated, robot-assisted surgery based on the GRS. There were two non-screw-related complications requiring return to the operating room.

OBJECTIVEAugmented reality (AR) is a novel technology that has the potential to increase the technical feasibility, accuracy, and safety of conventional manual and robotic computer-navigated pedicle insertion methods. Visual data are directly projected to the operator’s retina and overlaid onto the surgical field, thereby removing the requirement to shift attention to a remote display. The objective of this study was to assess the comparative accuracy of AR-assisted pedicle screw insertion in comparison to conventional pedicle screw insertion methods.METHODSFive cadaveric male torsos were instrumented bilaterally from T6 to L5 for a total of 120 inserted pedicle screws. Postprocedural CT scans were obtained, and screw insertion accuracy was graded by 2 independent neuroradiologists using both the Gertzbein scale (GS) and a combination of that scale and the Heary classification, referred to in this paper as the Heary-Gertzbein scale (HGS). Non-inferiority analysis was performed, comparing the accuracy to freehand, manual computer-navigated, and robotics-assisted computer-navigated insertion accuracy rates reported in the literature. User experience analysis was conducted via a user experience questionnaire filled out by operators after the procedures.RESULTSThe overall screw placement accuracy achieved with the AR system was 96.7% based on the HGS and 94.6% based on the GS. Insertion accuracy was non-inferior to accuracy reported for manual computer-navigated pedicle insertion based on both the GS and the HGS scores. When compared to accuracy reported for robotics-assisted computer-navigated insertion, accuracy achieved with the AR system was found to be non-inferior when assessed with the GS, but superior when assessed with the HGS. Last, accuracy results achieved with the AR system were found to be superior to results obtained with freehand insertion based on both the HGS and the GS scores. Accuracy results were not found to be inferior in any comparison. User experience analysis yielded “excellent” usability classification.CONCLUSIONSAR-assisted pedicle screw insertion is a technically feasible and accurate insertion method.

Objectives The aim of this study was to describe the use of locking compression plates (LCP) in Y-T humeral condyle fractures and to evaluate their clinical outcome. Methods This study involved a retrospective review, including clinical, radiographical and canine brief pain inventory outcome evaluation. Results Eighteen consecutive dogs met the inclusion criteria, and 15/18 were considered to have humeral intracondylar fissure. Twelve of 18 dogs had simple fractures, and the remaining six had comminuted fractures. Postoperative radiographs revealed accurate intracondylar reconstruction (articular step defect [ASD] Clinical significance Repair of Y-T humeral fractures with LCP allowed for hybrid fixation and monocortical screw placement in distal fracture fragments. There was no significant ASD at the intracondylar fracture line in most cases. ASD using combined medial and lateral approaches depends upon the accuracy of supracondylar reduction, particularly on the side that is reduced and stabilized first, and the use of locking screws may have been influential in minimizing primary loss of reduction, potentially maintaining the initial fragment reduction.

Objective To predict the bone formation stimulus of a transcondylar screw across an equine subchondral bone cyst (SBC) in an equine medial femoral condyle (MFC). Study design Finite element modeling (FEM) of an equine MFC with a 2 cm3 SBC under several transcondylar screw conditions. Sample population The right stifle of a yearling thoroughbred without stifle disease that had been euthanized for reasons unrelated to this study and donated to the University. Methods The FEM was derived from computed tomography of a yearling thoroughbred and analyzed in ABAQUS v6.14. The transcondylar screw was modeled as a 4.5-mm stainless steel cylinder. The region of interest was the centrodistal MFC, and bone stimulus was calculated. The stimulus threshold for bone formation (BFT) was >60 MPa and is presented as the percentage of total bone surface area (BFA) and frontal plane maps. Principal compressive stress vectors were also determined. Tested variables were daily cycles, load, and screw compression and position. Results At 750 cycles and 900-N load, BFT occurred proportionally with load, screw compression, and daily cycles (steps). Compressive stress was oriented vertically on the SBC surface without a screw but aligned with the long axis of well-placed lag screws. Screw placement through the void also increased the number and magnitude of compressive vectors. Conclusion This model predicted that a transcondylar lag screw across an MFC SBC increased surface BFA stimulation and reoriented the compression vector. Increasing screw compression, load, and steps per day increased the bone formation stimulus. Clinical significance This study provides evidence that supports the use of a lag screw thorough an MFC SBC to promote bone formation.

The aim of this study is to highlight the complications of instrumentation in the setting of syndromic craniovertebral junction (CVJ) anomalies. The records of patients with syndromic CVJ anomalies treated by this author during the period of 2012–2017 were retrospectively reviewed. Patients in whom intraoperative difficulties and complications were encountered were culled out from the database. Complications were divided into (1) technique related, (2) neural injury, (3) vascular injury, (4) instrumentation pull out/breakage, (5) inaccurate screw placement and, (6) where postoperatively, the surgeon felt an alternate surgical technique could have yielded better results. Four patients with either unexpected intraoperative difficulties or complications or in whom the technique could have been refined were identified. There were 2 patients with proatlas segmentation anomalies and 2 with Morquio’s-Brailsford disease. The first patient had cage migration which necessitated a second procedure during craniovertebral realignment, the second had partial penetration of the screw into the transverse foramen, the third with bipartite atlas underwent a C1–2 fixation without a horizontal cross-connector and, the fourth had screw pull outs from the subaxial cervical spine intraoperatively during an attempted occipitocervical fusion. In children with syndromic CVJ anomalies, the surgeon should be aware of the high risk of intraoperative difficulties and complications. Potential pitfalls and the ways to avoid these complications are discussed.

OBJECTIVEOccipitocervical fusions in the pediatric population are rare but can be challenging because of the smaller anatomy. The procedure is even more exacting in patients with prior suboccipital craniectomy. A proposed method for occipitocervical fusion in such patients is the use of occipital condyle screws. There is very limited literature evaluating the pediatric occipital condyle for screw placement. The authors examined the occipital condyle in pediatric patients to determine if there was an age cutoff at which condylar screw placement is contraindicated.METHODSThe authors performed a retrospective morphometric analysis of the occipital condyle in 518 pediatric patients aged 1 week–9 years old. Patients in their first decade of life whose occipital condyle was demonstrated on CT imaging in the period from 2009 to 2013 at the Augusta University Medical Center and Children’s Hospital of Georgia were eligible for inclusion in this study. Exclusion criteria were an age older than 10 years; traumatic, inflammatory, congenital, or neoplastic lesions of the occipital condyles; and any previous surgery of the occipitocervical junction. Descriptive statistical analysis was performed including calculation of the mean, standard deviation, and confidence intervals for all measurements. Probability values were calculated using the Student t-test with statistical significance determined by p < 0.05.RESULTSOverall, male patients had statistically significantly larger occipital condyles than the female patients, but this difference was not clinically significant. There was no significant difference in left versus right occipital condyles. There were statistically significant differences between age groups with a general trend toward older children having larger occipital condyles. Overall, 20.65% of all patients evaluated had at least one measurement that would prevent occipital condyle screw placement including at least one patient in every age group.CONCLUSIONSOccipital condyle screw fixation is feasible in pediatric patients younger than 10 years. More importantly, all pediatric patients should undergo critical evaluation of the occipital condyle in the axial, sagittal, and coronal planes preoperatively to determine individual suitability for occipital condyle screw placement.

Back Ground: Fractures of Distal Femur are common due to increased Road traffic accidents and fall from height because of increased construction activities. These fractures are quite disabling. So these fractures necessitate early stabilization. Internal fixation with VA-LCP has shown to give one of the best results in terms of fixation, recovery, fracture union and clinical outcome. Materials and Methods: 23 cases of Distal femur fractures treated with VA-LCP from August 2016 to August 2018 were selected for this study. They were admitted and examined according to protocol clinically and radiologically. All patients were followed up for a minimum of 6 months and outcome assessed with Neer’s score. Results: All fractures healed with an average duration of 23 weeks which is comparable with other studies. We had excellent outcome in 6 (26%) patient, satisfactory outcome in 13 (57%) patient and 4 had an unsatisfactory (17%) result. Average Neer’s Knee score was 81 which is comparable with other studies. Conclusion: The VA-LCP is the treatment of choice in the management of comminuted distal femoral fractures especially Type C fractures, where type C1 we have found higher Neer’s scores. VA-LCP also prevents compression of periosteal vessels. VA- LCP is the implant of choice especially in type C3 fractures as we can get purchase of multiple fracture fragments avoiding intra articular screw penetration because of screw insertion angle upto 150 compared to fixed orthogonal screw placement. Although in our series poor result were found in type C3 fractures we attribute this to long learning curve in treatment of type C3 fractures.

This literature review examines the relative placement of the interbody cage with respect to the unilateral screw construct to address the need for bilateral screw placement versus unilateral screw placement. Transforaminal lumbar interbody fusion (TLIF) has become a widely used technique for correcting lumbar intervertebral pathologies. This review addresses the necessity for further study on the effects of the relative position of intervertebral cage placement on the outcome of lumbar spine surgery after TLIF with unilateral pedicle screw fixation. Previous studies have addressed various factors, including posterior screw fixation, cage size, cage shape, and number of levels fused, that impact the biomechanics of the lumbar spine following TLIF. A simple survey of the literature was conducted. A search of the English literature was conducted using the keywords ‘TLIF,’ ‘transforaminal lumbar interbody fusion,’ ‘graft placement,’ ‘graft position,’ ‘cage position,’ ‘cage placement,’ ‘unilateral pedicle screw,’ ‘unilateral TLIF cage placement,’ ‘lumbar biomechanics,’ ‘lumbar stability,’ ‘lumbar fusion,’ and ‘lumbar intervertebral cage’ with various combinations of the operators ‘AND’ and ‘OR’ and no date restrictions. Seventeen articles in the English literature that were most relevant to this research question were identified. To the best of our knowledge, there are no published data addressing the effects of cage placement relative to the unilateral screw on lumbar stability in TLIF with unilateral pedicle screw fixation. Investigation of the effects of cage placement is, thus, warranted to achieve optimal clinical outcomes in patients undergoing TLIF with unilateral pedicle screw fixation.

Background Volar plating for distal radius fractures exposes the risk of extensor tendon rupture, mechanical problems, and osteoarthritis due to protruding screws. Purposes The purpose of this review was to identify the best intraoperative diagnostic imaging modality to identify dorsal and intra-articular protruding screws in volar plating for distal radius fractures. Methods The Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines were followed for this review. In vitro and in vivo studies that analyzed the reliability, efficacy, and/or accuracy of intraoperatively available imaging modalities for the detection of dorsal or intra-articular screw protrusion after volar plating for distal radius fractures were included. Results Described additional imaging modalities are additional fluoroscopic views (pronated views, dorsal tangential view [DTV], radial groove view [RGV], and carpal shoot through [CST] view), three-dimensional (3D) and rotational fluoroscopies, and ultrasound (US). For detection of dorsal screw penetration, additional fluoroscopic views show better results than conventional views. Based on small (pilot) studies, US seems to be promising. For intra-articular screw placement, 3D or 360 degrees fluoroscopy shows better result than conventional views. Conclusion Based on this systematic review, the authors recommend the use of at least one of the following additional imaging modalities to prevent dorsal protruding screws: CST view, DTV, or RGV. Tilt views are recommended for intra-articular assessment. Of all additional fluoroscopic views, the DTV is most studied and proves to be practical and time efficient, with higher efficacy, accuracy, and reliability compared with conventional views. Level of Evidence The level of evidence is Level III.

Objectives Nonsurgical management of unstable pelvic ring injuries is associated with poor outcomes. Posterior pelvic ring injuries include sacroiliac joint disruption and sacral fractures or a combination of the two. Morbidity is high in non-operatively managed patients. Screw fixation is being increasingly used to manage unstable posterior pelvic injuries. Limitations include a steep learning curve and potential for neurovascular injury. This is the first study in Indian population to describe the safe corridor for screw placement and check the feasibility of screw in both upper and lower sacral segments. Methods This study involved retrospective analysis of 105 pelvic CT scans of patients admitted to the emergency department of a Level 1 trauma centre. Vertical height at the level of constriction (vestibule) of S1 and S2 was measured in coronal sections and anteroposterior width of constrictions was measured in axial sections. We created a trajectory for 7.3 mm cylinder keeping additional 2 mm free bony corridor around it and confirmed that bony limits were not breached in axial, coronal and sagittal sections. Whenever there was breach in bony limit we checked applicability of 6.5 mm screw. Results The vertical height and anteroposterior width of vestibule/constriction of S1 was significantly higher in males, whereas S2 vestibule height and width were similar in males and females. Both male and female pelves were amenable to S1 Trans-sacral and S1 Iliosacral screw fixation with a 7.3 mm screw when a safe corridor of 2 mm was kept on all sides. However, when S2 segment was analysed, only 42.9% of male pelves and 25.7% of female pelves were amenable to insertion of trans-sacral 7.3 mm screw. Conclusion An individualized approach is necessary and each patient’s CT must be carefully studied before embarking on sacroiliac screw fixation in Indian population.

Contains fulltext : 239354.pdf (Publisher’s version ) (Open Access) Due to the complex anatomical shape of the pelvis, screw placement can be challenging in acetabular fracture surgery. This study aims to assess the accuracy of screw placement using patient-specific surgical drilling guides applied to pre-contoured conventional implants in acetabular fracture surgery. CT scans were made of four human cadavers to create 3D models of each (unfractured) pelvis. Implants were pre-contoured on 3D printed pelvic models and optically scanned. Following virtual preoperative planning, surgical drilling guides were designed to fit on top of the implant and were 3D printed. The differences between the pre-planned and actual screw directions (degrees) and screw entry points (mm) were assessed from the pre- and postoperative CT-scans. The median difference between the planned and actual screw direction was 5.9° (IQR: 4-8°) for the in-plate screws and 7.6° (IQR: 6-10°) for the infra-acetabular and column screws. The median entry point differences were 3.6 (IQR: 2-5) mm for the in-plate screws and 2.6 (IQR: 2-3) mm for the infra-acetabular and column screws. No screws penetrated into the hip joint or caused soft tissue injuries. Three-dimensional preoperative planning in combination with surgical guides that envelope pre-contoured conventional implants result in accurate screw placement during acetabular fracture surgery.

Background: The most appropriate treatment and management of posterior malleolar fractures (PMFs) lacks consensus. Indirect reduction and fixation with posterior to anterior (PA) screw shows promise by avoiding the risks associated with direct reduction or indirect anterior to posterior approaches. Some authors have raised concerns about potential risk to nearby structures with the PA technique, including hardware prominence into the syndesmosis. This study highlights use of the posteromedial vertical syndesmotic line (PVSL) as a fluoroscopic landmark, helping surgeons avoid intrasyndesmotic placement. Study aims are to evaluate PVSL correspondence with posterior border of the incisura tibialis and to define a safe zone between this line and flexor hallucis longus tendon. Methods: Indirect PA screw placement was completed on 10 cadaveric specimens, followed by fluoroscopy in mortise and lateral views. Dissection was performed to assess screw placement relative to the posteromedial border of the syndesmosis. The posterior border of the syndesmosis was marked with a radiopaque wire. Repeat imaging was completed to validate the fluoroscopic PVSL is representative of the posteromedial border of the tibial incisura. Results: On dissection, 9 out of 10 cadavers had accurate screw placement with no penetration into the syndesmosis. Corresponding imaging showed the screw head to be medial to the marker on mortise view. For the specimen with penetration into the syndesmosis, imaging confirmed that the screw head was lateral to the marker on mortise views. The radiopaque marker correlated with the PVSL for all specimens when comparing anatomic to radiographic findings. A radiographic safe zone is defined for the PA screw 12 mm medial to the PVSL to ensure no iatrogenic injury to the flexor hallucis longus tendon. Conclusion: This study demonstrated that a posterior incisura tibialis fluoroscopic landmark is unambiguous in localizing the posterior syndesmotic border and that screws medial to this line are safely out of the syndesmosis, while screws placed lateral are either in or at risk of intrasyndesmotic placement. A safe zone is defined for screw placement. Clinical Relevance: This article describes a radiographic and clinical safe zone for fixation and hardware placement during open reduction internal fixation (ORIF) of PMFs. This information will assist surgeons in avoiding intrasyndesmotic hardware placement as well as injury to deep soft tissue structures.

Background The infra-acetabular corridor is quite narrow, which makes a challenge for the orthopedists to insert the screw. This study aimed to explore the relationship between the infra-acetabular corridor diameter (IACD) and the minimum thickness of medial acetabular wall (MTMAW), and to clarify the way of screw placement. Methods The Computed tomography (CT) data of 100 normal adult pelvises (50 males and 50 females respectively) were collected and pelvis three-dimensional (3D) reconstruction was performed by using Mimics software and the 3D model was imported into Geomagic Studio software. The perspective of acetabulum was carried out orienting from iliopubic eminence to ischial tuberosity and the IACD was measured by placing virtual screws which was vertical to the corridor transverse section of “teardrop”. The relationship between IACD and MTMAW was analyzed. When IACD was ≥5 mm, 3.5 mm all-in screws were placed. When IACD was Results The IACD of males and females were (6.15 ± 1.24) mm and (5.42 ± 1.01) mm and the MTMAW in males and females were (4.40 ± 1.23) mm and (3.60 ± 0.81) mm respectively. The IACD and MTMAW in males were significantly wider than those of females (P r = 0.859), the regression equation was IACD = 2.111 + 0.917 MTMAW. In the all-in screw group, 38 cases (76%) were males and 33 cases (66%) were females respectively. The entry point was located at posteromedial of the apex of iliopubic eminence, and the posterior distance and medial distance were (8.03 ± 2.01) mm and (8.49 ± 2.68) mm respectively in males. As for females, those were (8.68 ± 2.35) mm and (8.87 ± 2.79) mm respectively. In the in-out-in screw group, 12 cases (24%) were males and 17 cases (34%) were females, respectively. The posterior distance and medial distance between the entry point and the apex of iliopubic eminence were (10.49 ± 2.58) mm and (6.17 ± 1.84) mm respectively in males. As for females, those were (10.10 ± 2.63) mm and (6.63 ± 1.49) mm respectively. The angle between the infra-acetabular screw and the sagittal plane was medial inclination (0.42 ± 6.49) °in males, lateral inclination (8.09 ± 6.33) °in females, and the angle between the infra-acetabular screw and the coronal plane was posterior inclination (54.06 ± 7.37) °. Conclusions The placement mode of the infra-acetabular screw (IAS) can be determined preoperatively by measuring the MTMAW in the CT axial layers. Compared with all-in screw, the in-out-in screw entry point was around 2 mm outwards and backwards, and closer to true pelvic rim.

Background Whether the accuracy of robot-assisted spinal screw placement is significantly higher than that of freehand and the source of robotic deviation remain unclear. Methods Clinical data of 105 patients who underwent robot-assisted spinal surgery was collected and screw accuracy was evaluated by computed tomography according to the modified Gertzbein-Robbins classification. Patients were grouped by percutaneous and open surgery. Intergroup comparisons of clinical and screw accuracy parameters were performed. Reasons for deviation were determined. Thirty-one patients with lumbar spondylolisthesis undergoing open robot-assisted surgery and the same number of patients treated by open freehand surgery were compared for screw accuracy. Results Screw accuracy was not significantly different between the percutaneous and open groups in both intra- and postoperative evaluations. Tool skiving was identified as the main cause of deviation. The proportion of malpositioned screws (grade B+C+D) was significantly higher in the freehand group than in the robot-assisted group. However, remarkably malpositioned (grade C+D) screws showed no significant differences between the groups. No revision surgery was necessary. Conclusions Robot-assisted spinal instrumentation manifests high accuracy and low incidence of nerve injury. Tool skiving is a major cause of implant deviation. This article is protected by copyright. All rights reserved.

Background: Spinal instrumentation in children with congenital spine deformity poses challenges to the surgeon, given the small patient size and the anomalous anatomy often encountered. Purpose: We aimed to investigate the accuracy of screw placement when robotics coupled with real-time navigation was used for surgical treatment of pediatric congenital spine deformity at 1 institution. Methods: We conducted a retrospective search of our institution’s database for all patients younger than 18 years of age with congenital spine deformity who were treated with the robotics surgical platform coupled with navigation between June 2019 and December 2020. We recorded data on demographics, location and type of anomaly, procedure performed, and intraoperative variables related to robotics and navigation. We reviewed the images of patients who had intraoperative 3-dimensional imaging or postoperative computed tomographic scans to determine the accuracy of screw placement using the Gertzbein-Robbins scale. Results: In 14 patients identified, a total of 95 screws were attempted, with 94 successfully placed using robotics coupled with navigation. There were no noted screw-related complications (neurologic or visceral) and no return to the operating room for screw malposition. Conclusion: Patients with congenital spine deformity present potentially unique challenges due to variant anatomy. This retrospective series suggests that robotics coupled with navigation for congenital spine deformity correction in the pediatric population may aid in accurate screw placement and reduce complication rates. More rigorous study is warranted.

Purpose To evaluate the accuracy of screw placement and fusion rate after the minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) technique under O-arm navigation. Methods In 475 consecutive patients at a single-center, the accuracy of screw placement was evaluated on intraoperative O-arm imaging. Misplaced screws were investigated to identify the direction of deviation and associated clinical outcomes. The fusion rate was evaluated on postoperative computed tomography scan at 1 and 2 year(s). The assessment of screw placement and fusion level was analyzed for inter-rater reliability and reported as a kappa value. Accuracy of screw placement (Gertzbein-Robbins Classification), extent of fusion (Bridwell Interbody Fusion Grading System), and complications were considered as outcome measures. Results A retrospective data analysis from 2,098 pedicle screws in 475 patients. The mean age of participants was 56.61 ± 12.30 years, and 45.26% were female. Their ethnicities were as follows: Asian (58.74%), Caucasian (20.21%), Middle-eastern (14.32%), and African (6.74%). The final fusion levels were single (80.63%), two (18.11%), three (1.05%), and four (0.21%). There were L4/L5 as the most prevalent placement (55.35%), followed by L5/S1 (36.29%), L3/L4 (5.22%), L2/L3 (2.35%), L1/L2 (0.52%), and S1/S2 (0.26%). Seven out of 2,098 screws were breaches. None of screw needed immediate revision. In total, 99.66% of the screws were grade A (no breach), 0.19% were grade B (breach

Background: Three-dimensional (3-D) printed templates are increasingly applied in spinal surgery, but are rarely used in the treatment of congenital scoliosis. This study aimed to evaluate the accuracy and safety of 3D printed template-assisted screw placement in the treatment of congenital scoliosis.Methods: A total of 67 patients with congenital scoliosis treated in our hospital between January 2017 to January 2019 were retrospectively included (mean age= 4.13±2.66 years, range: 2-15) and divided into the template-assistant group (n=34) and the freehand group (n=33) according to the screw placement method. The accuracy rate of pedicle screw placement, surgical outcomes, and incidence of complications were compared between groups.Results: Although the good accuracy (grade 0+ grade 1) rate of pedicle screw placement was comparable between the two groups, the excellent accuracy (grade 0) rate was significantly higher in the template-assistant group than in the freehand group (96.10% vs. 88.64%, P=0.007). The main curve Cobb's angle and Kyphosis' angle significantly decreased after surgery in both groups but without a significant intergroup difference. The template-assistant group had a significantly lower postoperative complication rate than the freehand group (0% vs. 18.18%; P=0.009). The 4 patients with postoperative complications in the freehand group all received revision surgery.Conclusion: The 3D printed templates can improve the excellent accuracy rate of screw placement and reduce postoperative complications in the treatment of congenital scoliosis, thereby improving the therapeutic efficacy.

Background This study aims to compare the clinical results of patients with upper thoracic vertebral fractures treated with pedicle screw and posterior spinal fusion with preoperative surgical planning and 3-dimensional (3D) modeling and patients treated with freehand screws. Methods Fifty patients who underwent pedicle screw placement with a diagnosis of upper thoracic fracture between June 2018 and October 2020 were included in our study. Pedicle screws were used in 25 patients (group 1) after the planning was completed with the help of 3D preoperative printing and modeling. Pedicle screws were applied in 25 patients in the control group (group 2) using the freehand technique. Intraoperative bleeding amount, operation time, and correct screw placement data in both groups were recorded. Results The operation time was 134 ± 22 minutes for group 1 and 152 ± 38 minutes for group 2. The difference in operation times was found to be statistically significant (p < 0.05). Based on axial and sagittal reconstruction images, the accuracy rate of pedicle screw placement (grades 0 and 1) in group I was 96.6% compared to 83.6% in group II. The minor perforation rate (grade 1, 4 mm) was 2.3% in group II; however, misplaced screws were not associated with neurological deficits. The difference in overall accuracy rates between the two groups was significant (p < 0.05). Conclusions For 3D models of upper thoracic pedicle screw insertion, guide plates can be produced inexpensively and individually. It provides a new method for the accurate placement of upper thoracic pedicle screws with high accuracy and secure use in screw insertion.

Background: Acromial fractures are rare and there is no consensus on fixation, but more and more studies have reported using two screws to fix Ogawa type I acromial fractures. The objective of this study was to obtain the ideal length, diameter, insertion point and angle of the screw using a novel 3D technology. Methods: Scapula CT data of 100 human subjects were obtained to reconstruct 3D models. The transparency of 3D models was then downgraded along the axial perspective (the view perpendicular to the cross section of the acromial axial) to find the maximum translucent area. Two virtual screws were placed from the anterior edge of the acromial until they penetrated the posterior cortical bone. The largest diameters and lengths of the screw were measured, and the direction and insertion point of the screw were observed.Results: The mean maximum lengths of medial and lateral screws were 43.33±6.17mm and 39.23±6.01mm, respectively. The mean maximum diameters of medial and lateral screws were 4.71±1.23 mm and4.97±1.07mm, respectively. The study found differences in screw length, diameter and insertion point between males and females. The differences sexes in screw angle were not statistical significance.Conclusions: Using the 3D model, we demonstrated that the distal acromial can be safely placed with two screws and provide valuable guidance for screw fixation of Ogawa type I acromial fractures.

OBJECTIVE To determine the accuracy of transcondylar screws placed from medial-to-lateral using preoperative planning on computed tomography (CT) and an aiming device in elbows with humeral intracondylar fissures (HIFs). STUDY DESIGN Retrospective case series. ANIMALS Twenty-five client-owned dogs with HIF. METHODS A 4.5-mm transcondylar screw was placed in 34 elbows with HIF. humeral condylar diameter (HCD) was measured at the humeral condylar isthmus on CT. Entry and exit points were planned at 0.3 × HCD cranial and 0.2 × HCD distal to the medial epicondyle and 0.3 × HCD cranial and 0.3 × HCD distal to the lateral epicondyle. An aiming device was used to guide drilling from the medial entry point to the lateral exit point. The difference between planned and actual screw entry and exit points, and the angular deviation of the actual screw axis from the planned screw axis, was assessed on the postoperative CT scans. RESULTS Thirty-three out of 34 screws were completely within the humeral condyle. Thirteen out of 34 screws were placed less than 2 mm from planned entry and exit points in both the transverse and the frontal plane. The axis of the screw deviated by a mean of 3.2° (transverse plane) and 3.5° (frontal plane) from the planned axis. CONCLUSION Humeral transcondylar screws placed with the technique tested here were entirely within the humeral condyle in 33 out of 34 elbows. CLINICAL SIGNIFICANCE Use of CT planning and an aiming device allows accurate placement of transcondylar screws from medial-to-lateral in dogs with HIF.

BackgroundAcromial fractures are rare and there is no consensus on fixation, but an increasing number of studies have reported using two screws to fix Ogawa type I acromial fractures. The objective of this study was to obtain the ideal length, diameter, insertion point, and angle of the screw using a novel 3D simulation.MethodsThe scapular CT data of 100 individuals were obtained to reconstruct 3D models. The transparency of the 3D model was then downgraded along the axial perspective (the view perpendicular to the cross section of the acromion axis) to find the maximum translucent area. Two virtual screws were placed at the anterior edge of the acromion until they penetrated the posterior cortical bon. The largest diameters and lengths of the screw were measured, and the direction and insertion point of the screw were observed.ResultsThe mean maximum lengths of the medial and lateral screws were 43.33 ± 6.17 mm and 39.23 ± 6.01 mm, respectively. The mean maximum diameters of the medial and lateral screws were 4.71 ± 1.23 mm and 4.97 ± 1.07 mm, respectively. Differences in screw length, diameter, and insertion point between males and females were found. The differences in screw angle between sexes were not statistically significant.ConclusionsBased on a 3D model test, we recommend the size, entry points, and angles of screws for Ogawa type I acromial fractures, providing valuable guidance for clinical work. More accurate screw parameters can be obtained preoperatively by establishing an individualized 3D model.

Purpose: Proper placement of infra-acetabular screws is technically demanding; there is a limited safe zone for screw fixation because of the complexity of the bone anatomy around the hip joint and the vulnerability of the major neurovascular bundles in the pelvic cavity. We aimed to present the obturator hook technique as a surgical technique for infra-acetabular screw placement in acetabular and pelvic fractures and report its radiological outcomes. Methods: Patients treated with infra-acetabular screw placement using the obturator hook technique between January 2015 and August 2020 were enrolled in this study. We collected data on demographics, surgical approach, reduction status, complications, and outcomes. The radiological outcomes of infra-acetabular screw placement based on computed tomography findings were evaluated as follows: success, articular penetration, or out of the bone. Results: Thirty-five patients underwent infra-acetabular screw placement (26 men, 9 women; mean age, 55 years; range, 27–90 years). One patient underwent bilateral infra-acetabular screw placement; therefore, 36 infra-acetabular screws were inserted in all patients. An ideal placement was achieved with 27 infra-acetabular screws (27/36, 75%). Seven infra-acetabular screws (7/36, 19%) showed articular penetration, and two infra-acetabular screws (2/36, 6%) were placed outside the bone. One patient with articular penetration and mechanical symptoms of the hip joint required screw replacement. No other complications, including obturator nerve and vascular injuries, were observed. Conclusion: The obturator hook technique could be a favorable and individualized method for infra-acetabular screw placement in patients with acetabular and pelvic fractures. Level of Evidence: IV, retrospective descriptive study.

Study Design: A retrospective study.Objective: To investigate a machine learning algorithm to explore the influence of pedicle morphological parameters and pedicle screw size on safe screw placement in the treatment of idiopathic scoliosis with freehand. And a model was built to guide the selection of screwMethods: We analyzed 52 patients with idiopathic scoliosis who underwent correction surgery in our hospital from June 2012 to December 2019, including 17 males and 35 females aged 10-20 years. All pedicle screws were placed by freehand. Preoperative and postoperative X-ray and CT scans of whole spine were performed to measure Cobb Angle and pedicle morphological parameters, including transverse diameter of the pedicle, sagittal diameter of the pedicle, length of the pedicle channel, rotation angle of vertebrae, angle of the sagittal plane of pedicle and angle of the horizontal plane of pedicle. Screw penetration grading was also evaluated. Random forest were used to build a machine learning model to help the decision making of choosing an appropriate screw based on pedicle parameters and screw size.Results: A total of 888 screws and pedicles were included. The satisfactory rate of screw placement was 88.5%. The pedicle screw size was analyzed and predicted based on screw penetration and pedicle morphological parameters. The AUROC of random forest classification model achieved 0.712. The goodness of fit(R2) was 0.546.Conclusion: Our model could provide guidance for the doctor to choose the length of the screw before surgery, and the classification model could also give a preliminary prediction of whether there would be anterior screw penetration based on the pedicle parameters.

OBJECTIVES The iliac cortical density (ICD) is a critical fluoroscopic landmark for pelvic percutaneous screw placement. Our purpose was to evaluate the ICD as a landmark in pediatrics and quantify the diameter of osseous pathways for 3 screw trajectories: iliosacral (IS) at S1 and transiliac-transsacral (TSTI) at S1 and S2. METHODS Two hundred sixty-seven consecutive pelvic CT scans in children 0-16 years of age were analyzed. ICD and S1 vertebral heights were measured at multiple regions along S1. Their height and corresponding ratios, as well as osseous screw corridor dimensions were compared between age groups and by the dysmorphic status. RESULTS In the nondysmorphic pelvises, S1 height, ICD height, and the ICD to S1 height ratio increased across age groups for all locations (P < 0.001). All 3 screw pathway diameters increased with age (P < 0.001). In the dysmorphic group, there was no increase in ICD to S1 height ratio with age. Except for the age 0-2 group, the ICD to S1 height ratios were significantly larger in the nondysmorphic group. In the dysmorphic group, S1 TSTI pathway remained narrow with age, whereas IS at S1 and TSTI at S2 had a significant increased diameter with age (P < 0.001). CONCLUSION The ICD is a useful fluoroscopic landmark for percutaneous screw placement in the pediatric pelvis. For nondysmorphic pelvises, the ICD to S1 height ratio, as well as osseous corridors for IS, TSTI at S1, and TSTI at S2 screw trajectories increase significantly with age. The margin for safe screw placement in S1 is smaller for younger and dysmorphic pelvises.

Study Design: Prospective case series. Objective: SSPSS (single step pedicle screw system) was developed for minimally invasive spine surgery. We performed this study to report on safety, workflow, and our initial clinical experience with this novel technique. Methods: The prospective study was conducted on patients who underwent pedicle screw fixation between October 2017 and April 2018 using a novel single step 3D navigated pedicle screw system for MIS. Outcome measurements were obtained from intraoperative computerized tomography. The images were evaluated to determine pedicle wall penetration. We used a grading system to assess the severity of the pedicle wall penetration. Breaches were classified as grade 1 ( 1 and as cranial, caudal, medial, and lateral. Results: Our study includes 135 screws in 24 patients. SSPSS eliminated K-wires and multiple steps traditionally necessary for MIS pedicle screw insertion. The median time per screw was 2.45 minutes. 3 screws were corrected intraoperatively. Pedicle wall penetration occurred in 14 screws (10%). Grade 1 breaches occurred in 4 screws (3%) and grade 2 breaches occurred in 10 screws (7%). Lateral breaches were observed more often than medial breaches. The accuracy rate in our study was 90% (Grade 0 breach). No revision surgeries were needed and no complications occurred. Conclusions: Our study suggests that SSPSS could be a safe, accurate, and efficient tool. Our accuracy rate is comparable to that found in the literature.

Background Knowledge of free-hand screw technique remains critical to adequately train neurosurgical residents. The purpose of this study was to evaluate the accuracy of screw placement via the free-hand technique in lumbar, thoracic, and cervical spine by neurosurgical residents completing an enfolded spine fellowship. Methods Medical records of all patients who underwent free-hand screw placement at all spinal levels over a 6-month period by senior neurosurgical residents enrolled in an in-folded spine fellowship were retrospectively reviewed. Postoperative CT images were assessed for presence and direction of cortical breach. Results Twenty-six patients underwent 162 free-hand screw placements. The most commonly placed screws were cervical lateral mass screws (n = 69), thoracic (n = 41), and lumbar pedicle screws (n = 41). The most common indication for surgery was deformity (n = 22), followed by infection (n = 2) and trauma (n = 2). Fifty-five breaches were identified in 44 (27 %) screws placed in 21 patients (81 %). Anterior breach was identified in 22 cases (40.0 %), lateral in 12 (23.6 %), superior in 7 (12.7 %), and inferior in 7 (12.7 %), and medial in 6 (10.9 %). The most common level of breach was observed in cervical lateral mass screws (n = 19, 43 %) and least common in C2 pars screws (n = 1, 2%). With an average length of follow up of 12.1 ± 7.7 months of follow-up, no clinical sequalae of screw breach was observed. Conclusions Despite the high prevalence of screw breach using the free-hand technique by neurosurgical residents, the absence of clinical sequelae implies safety and emphasizes the importance of early exposure to this technique during neurosurgical residency training.

AIM To demonstrate the possibility of revision screw placement to the atlas, as well as define the safety zones and orientation angles. MATERIAL AND METHODS This retrospective study analysed the records of four patients who were operated for AAI earlier. Because they needed revision of Atlas screws, they were re-operated after obtaining the measurements mentioned in this study. In addition, measurements of 50 healthy subjects were included in the study as the control group. Maximum screw lengths were also measured. RESULTS Safe zone in the ideal sagittal direction were wider. As the screw projection becomes more cephalic direction in the sagittal plane, the safe zone for the screw becomes narrower. With the sagittal angle moving forwards cranially, the screw length becomes longer. CONCLUSION Atlas lateral mass screws could be safely revised whenever needed. The fact that needs to be considered is that the angular range becomes narrower, and the screw length becomes longer when the screw is directed more cranially.