Establishing finite element model credibility of a pedicle screw system under compression-bending: An end-to-end example of the ASME V&V 40 standard.

Computational modeling and simulation (CM&S) is a key tool in medical device design, development, and regulatory approval. For example, finite element analysis (FEA) is widely used to understand the mechanical integrity and durability of orthopaedic implants. The ASME V&V 40 standard and supporting FDA guidance provide a framework for establishing model credibility, enabling deeper reliance on CM&S throughout the total product lifecycle. Examples of how to apply the principles outlined in the ASME V&V 40 standard are important to facilitating greater adoption by the medical device community, but few published examples are available that demonstrate best practices. Therefore, this paper outlines an end-to-end (E2E) example of the ASME V&V 40 standard applied to an orthopaedic implant. The objective of this study was to illustrate how to establish the credibility of a computational model intended for use as part of regulatory evaluation. In particular, this study focused on whether a design change to a spinal pedicle screw construct (specifically, the addition of a cannulation to an existing non-cannulated pedicle screw) would compromise the rod-screw construct mechanical performance. This question of interest (?OI) was addressed by establishing model credibility requirements according to the ASME V&V 40 standard. Experimental testing to support model validation was performed using spinal rods and non-cannulated pedicle screw constructs made with medical grade titanium (Ti-6Al-4V ELI). FEA replicating the experimental tests was performed by three independent modelers and validated through comparisons of common mechanical properties such as stiffness and yield force. The validated model was then used to simulate F1717 compression-bending testing on the new cannulated pedicle screw design to answer the ?OI, without performing any additional experimental testing. This E2E example provides a realistic scenario for the application of the ASME V&V 40 standard to orthopedic medical device applications.

Forearm bone mineral density predicts screw loosening after lumbar fusion similar to lumbar Hounsfield unit value in patients with lumbar spondylolisthesis.

Preoperative bone density assessment is necessary to predict screw loosening. The forearm BMD is a useful predictor of BMD-related complications after lumbar operation. Our results show that the forearm BMD is as effective a predictor of screw loosening as the lumbar average HU value. Measurement of the forearm BMD may be a useful adjunct in predicting screw loosening following lumbar fusion. PURPOSE: To determine the relationship between forearm bone mineral density (BMD) and the risk of pedicle screw loosening in patients with lumbar spondylolisthesis. METHODS: We retrospectively evaluated 270 patients who underwent posterior lumbar interbody fusion for lumbar spondylolisthesis. The patients were divided into two groups on the basis of the with or without loose screws: the loosening group and the non-loosening group. The patient's gender, age, BMI, smoking and diabetes histories, and the operative segment were recorded as the basic information. The Hounsfield unit (HU) value for the BMD of the L1-4 lumbar was measured using computed tomography. The patient's distal one-third of the length of the radius and ulna of the non-dominant forearm was chosen as the site for dual-energy X-ray (DXA) bone density testing. RESULTS: The rate of screw loosening was 13% at a minimum 12 months follow-up. Average forearm BMD (0.461 ± 0.1 vs 0.577 ± 0.1, p < 0.001) and mean HU value (L1-4) (121.1 ± 27.3 vs 155.6 ± 32.2, p < 0.001) were lower in the screw loosening group than those in the non-loosening group. In multivariate logistic regression analysis, the forearm BMD (OR 0.840; 95%CI 0.797-0.886) and HU value (L1-4) (OR 0.952; 95%CI 0.935-0.969) were independent risk factor for screw loosening. The area under the curve (AUC) for the forearm BMD and HU value for prediction of pedicle screw loosening was 0.802 and 0.811. The forearm BMD cut-off for predicting pedicle screw loosening was 0.543 (sensitivity, 0.800; specificity, 0.864). CONCLUSIONS: The forearm BMD was an independent risk factor for loosening of the lumbar pedicle screws. The forearm BMD was a valid predictor of pedicle screw loosening in patients undergoing lumbar fusion, as was the CT HU value.

Combined vertebroplasty and pedicle screw insertion for vertebral consolidation: feasibility and technical considerations.

PURPOSE: To assess the feasibility and technical accuracy of performing pedicular screw placement combined with vertebroplasty in the radiological setting. METHODS: Patients who underwent combined vertebroplasty and pedicle screw insertion under combined computed tomography and fluoroscopic guidance in 4 interventional radiology centers from 2018 to 2023 were retrospectively assessed. Patient demographics, vertebral lesion type, and procedural data were analyzed. Strict intra-pedicular screw positioning was considered as technical success. Pain score was assessed according to the Visual Analogue Scale before the procedure and in the 1-month follow-up consultation. RESULTS: Fifty-seven patients (38 men and 19 women) with a mean age of 72.8 (SD = 11.4) years underwent a vertebroplasty associated with pedicular screw insertion for the treatment of traumatic fractures (29 patients) and neoplastic disease (28 patients). Screw placement accuracy assessed by post-procedure CT scan was 95.7% (89/93 inserted screws). A total of 93 pedicle screw placements (36 bi-pedicular and 21 unipedicular) in 32 lumbar, 22 thoracic, and 3 cervical levels were analyzed. Mean reported procedure time was 48.8 (SD = 14.7) min and average injected cement volume was 4.4 (SD = 0.9) mL. A mean VAS score decrease of 5 points was observed at 1-month follow-up (7.7, SD = 1.3 versus 2.7, SD = 1.7), p < .001. CONCLUSION: Combining a vertebroplasty and pedicle screw insertion is technically viable in the radiological setting, with a high screw positioning accuracy of 95.7%.

Individualized Design Application of 3-Dimensional Printing Navigational Template for Pedicle Screw Installation: A Training Case Report.

BACKGROUND The proper installation for pedicle screws by the traditional method of surgeons dependent on experience is not guaranteed, and educational solutions have progressed from chalkboards to electronic teaching platforms. We designed a case of 3-dimensional printing drill guide template as a surgical application, which can accurately navigate implantation of pedicle screws, and assessed its effect for simulative training. MATERIAL AND METHODS We randomly selected a set of computed tomography data for spondylolisthesis. A navigational template of pedicles and screws was designed by software Mimics and Pro-E, where trajectories of directions and angles guiding the nail way were manipulated for screwing based on anatomy, and its solid model was fabricated by a BT600 3D printer. The screws were integrated and installed to observe their stability. RESULTS The navigational model and custom spine implants were examined to be compatibly immobilized, because they are tolerant to radiation and stable against hydrolysis. The screw size and template were fit accurately to the vertebrae intraosseously, because the pilot holes were drilled and the trajectories were guided by cannulas with visible routes. During the surgical workflow, the patient reported appreciation and showed substantial compliance, while having few complications with this approach. Compared with fluoroscopy-assisted or free-hand techniques, the effect of simulative training during processing was excellent. CONCLUSIONS The surgical biomodel is practical for the procedural accuracy of surgical guides or as an educational drill. This fostering a style of "practice substituting for teaching" sets a paragon of keeping up with time and is worthy of recommendation.

Percutaneous versus traditional open approaches for the treatment of thoracolumbar fractures in patients without neurologic deficits: a meta-analysis of 35 cohort studies.

At present, percutaneous surgery is widely used to treat thoracolumbar fractures. However, the actual safety, feasibility, and effectiveness of percutaneous surgery are not clear. Through systematic review and meta-analysis, we compared the efficacies of percutaneous pedicle screw fixation and open pedicle screw fixation in the treatment of thoracolumbar fractures without nerve root symptoms. We systematically searched the PubMed, Embase, and Cochrane libraries for articles published on or before June 2023. All results were evaluated by standard methods recommended for meta-analysis, continuous data were expressed by standard mean differences (SMDs), and binary variables were analyzed by odds ratios (ORs) and 95% confidence intervals (95% CIs). We also explored the main sources of heterogeneity and the stability of the results through sensitivity analysis, Begg's funnel plots, and Egger's test. Thirty-five cohort studies with a total of 3039 patients were included. The study found that patients who undergo percutaneous approaches have less intraoperative blood loss (IBL), shorter length of hospital stay (LOS), shorter operation time, and shorter incision. Moreover, percutaneous approaches had more advantages in terms of visual analog scale (VAS) scores, Oswestry Disability Index (ODI) scores, and infection rates. However, there was no significant difference in anterior vertebral body height (AVB), Cobb angle (CA), or screw errors between the two groups. In the long run, the clinical and surgical results of the percutaneous approach are better than those of the open approach, but the radiological results of both operations do not seem to show an advantage for any specific approach. Because of publication bias and heterogeneity, our findings must be interpreted with caution. However, this paper will provide some support for clinicians to choose suitable surgical methods for the treatment of thoracolumbar fractures.

Effectiveness and safety of robot-assisted versus fluoroscopy-assisted pedicle screw implantation in scoliosis surgery: a systematic review and meta-analysis.

This study aimed to assess the effectiveness and safety of robot-assisted versus fluoroscopy-assisted pedicle screw implantation in scoliosis surgery. The study was registered in the PROSPERO (CRD42023471837). Two independent researchers searched PubMed, Web of Science, Cochrane Library, and China National Knowledge Infrastructure. The outcomes included operation time, pedicle screw implantation time, blood loss, number of fluoroscopic, accuracy of pedicle screw position, hospital stays, postoperative hospital stays, Visual Analog Scale (VAS), Japanese Orthopaedic Association (JOA) score, Scoliosis Research Society-22(SRS-22), cobb angle, cobb angle correction rate, sagittal vertical axis (SVA), and complications. Eight papers involving 473 patients met all the criteria. There was no significant difference between the two groups regarding the reduction in operation time. The effect of reducing the pedicle screw implantation time in the RA group was significant (WMD = -1.28; 95% CI: -1.76 to -0.80; P < 0.00001). The effect of reducing the blood loss in the RA group was significant (WMD=-105.57; 95% CI: -206.84 to -4.31; P = 0.04). The effect of reducing the number of fluoroscopic in the RA group was significant (WMD=-5.93; 95% CI: -8.24 to -3.62; P < ). The pedicle screw position of Grade A was significantly more in the RA group according to both the Gertzbein-Robbins scale and the Rampersaud scale. Compared with the FA group, the difference in the hospital stays in the RA group was not statistically significant, but the effect of reducing the postoperative hospital stays in the RA group was significant (WMD = -2.88; 95% CI: -4.13 to -1.63; P < 0.00001). The difference in the VAS, JOA, SRS-22, Cobb angle and Cobb angle correction rate, SVA, and complications between the two groups was not statistically significant. The robot-assisted technique achieved statistically significant results in terms of pedicle screw placement time, blood loss, number of fluoroscopies, accuracy of pedicle screw position, and postoperative hospital stay.

A screw algorithm for congenital C2-3 fusion with high-riding vertebral arteries: feasibilities and clinical outcomes of five different fixation techniques.

OBJECTIVE: To propose a screw algorithm and investigate the anatomical feasibilities and clinical outcomes of five distinct fixation methods for C2-3 fused vertebra with high-ridding vertebral arteries (VA) (HRVA) when the C2 pedicle screw placement is unfeasible. METHODS: Thirty surgical patients with congenital C2-3 fusion, HRVA, and atlantoaxial dislocation (AAD) were included. We designed a algorithm for alternative screw implantation into C2-3 fused vertebrae, including C2 pedicle screw with in-out-in (passing VA groove) technique (in-out-in screw), subfacetal screw, translaminar screw, lateral mass screw, C3 pedicle screw. VA diameter and position, C2 and C3 pedicles, superior facets, fused lamina, and fused lateral mass dimensions were evaluated for screw implantation indication. Implant failure, reduction loss, implant placement accuracy were investigated by computed tomography. RESULTS: A total of 5 VAs were identified as distant VAs; a total of 2 VAs were categorized as occlusive VAs. Sufficient dimension of lateral mass and lamina provided the broadest indications for screw implantation, while the distant or occlusive VA provided the most limited indications for in-out-in screw. The indications of five alternative methods ranged from narrowest to widest as follows: in-out-in screw, C3 pedicle screw, subfacetal screw, translaminar screw, lateral mass screw. The translaminar screws and the lateral mass screws increased the probability of implant failure. All patients who received in-out-in screws, C3 pedicle screws, and subfacetal screws achieved fusion. The accuracy ranged from lowest to highest as follows: C3 pedicle screw, lateral mass screw, in-out-in screw, subfacetal screw, translaminar screw. No translaminar screws deviated. CONCLUSIONS: The algorithm proved to be a valuable tool for screw selection in cases of C2-3 fused vertebrae with HRVAs. The subfacetal screw, boasting broad indications, a high fusion rate, and exceptional accuracy, stood as the primary preferred alternative.

Clinical outcomes of short rod technique in posterior lumbar interbody fusion surgery: a minimum of 2-year follow-up.

PURPOSE: We present for the first time a novel entry point of pedicle screws (Short Rod Technique, SRT), which can avoid superior facet violation and has been verified as a safe screw placement method. The purpose of this study is to determine the clinical outcomes of SRT in posterior lumbar interbody fusion (PLIF) surgery. METHODS: We retrospectively analyzed the clinical outcomes of 89 patients who received SRT and 109 patients who received PLIF surgery with regular entry points of pedicle screws with a minimum of 2 years of follow-ups. Patients were divided into three groups according to the number of fusion segments, and the clinical outcomes of the three groups were compared. RESULTS: The length of the wound and the length of rods were significantly shorter in the each SRT group. Less intraoperative blood loss was observed in the SRT group in patients with a single segment and two segments fusions, but not in three segments fusions. Fewer degenerations of the upper adjacent segment were observed in the SRT group in patients with a single segment and three segments fusions. In addition, less postoperative wound pain related to PLIF surgery was observed in the SRT group in patients with two and three segments fusions. CONCLUSION: SRT has been validated as an effective technique with good clinical outcomes, especially for reducing the occurrence of upper ASD in PLIF surgery with a single segment and three segments. The present study provides spinal surgeons with a novel method for performing PLIF surgery.

Analysis of duration of different stages of surgery in posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS) patients: comparison between severe versus non-severe AIS.

PURPOSE: Prolonged surgical duration in severe adolescent idiopathic scoliosis (AIS) patients is associated with increased blood loss and perioperative complications. The aim of this study was to compare the duration of each stage of posterior spinal fusion (PSF) in severe AIS (Cobb angle ≥ 90°) with non-severe AIS patients. This analysis will identify the most time-consuming stage of PSF and help surgeons formulate strategies to shorten operative time. METHODS: Retrospective study whereby 90 AIS patients (Lenke type 2, 3, 4, and 6) who underwent PSF from 2019 to 2023 were recruited. Twenty-five severe AIS patients were categorized in Gp1 and 65 non-severe AIS patients in Gp2. Propensity score matching (PSM) with one-to-one with nearest neighbor matching (match tolerance 0.05) was performed. Outcomes measured via operation duration of each stage of surgery, blood loss, number of screws, fusion levels and screw density. RESULTS: Twenty-five patients from each group were matched. Total operative time was significantly higher in Gp1 (168.2 ± 30.8 vs. 133.3 ± 24.0 min, p < 0.001). The lengthiest stage was screw insertion which took 58.5 ± 13.4 min in Gp1 and 44.7 ± 13.7 min in Gp2 (p = 0.001). Screw insertion contributed 39.5% of the overall increased surgical duration in Gp1. Intraoperative blood loss (1022.2 ± 412.5 vs. 714.2 ± 206.7 mL, p = 0.002), number of screws (17.1 ± 1.5 vs. 15.5 ± 1.1, p < 0.001) and fusion level (13.1 ± 0.9 vs. 12.5 ± 1.0, p = 0.026) were significantly higher in Gp1. CONCLUSION: Screw insertion was the most time-consuming stage of PSF and was significantly longer in severe AIS. Adjunct technologies such as CT-guided navigation and robotic-assisted navigation should be considered to reduce screw insertion time in severe AIS.

Accuracy of augmented reality-assisted pedicle screw placement: a systematic review.

OBJECTIVE: Conventional freehand methods of pedicle screw placement are associated with significant complications due to close proximity to neural and vascular structures. Recent advances in augmented reality surgical navigation (ARSN) have led to its adoption into spine surgery. However, little is known regarding its overall accuracy. The purpose of this study is to delineate the overall accuracy of ARSN pedicle screw placement across various models. METHODS: A systematic review was conducted of Medline/PubMed, Cochrane and Embase Library databases according to the PRISMA guidelines. Relevant data extracted included reports of pedicle screw placement accuracy and breaches, as defined by the Gertzbein-Robbins classification, in addition to deviation from pre-planned trajectory and entry point. Accuracy was defined as the summation of grade 0 and grade 1 events per the Gertzbein-Robbins classification. RESULTS: Twenty studies reported clinically accurate placed screws. The range of clinically accurate placed screws was 26.3-100%, with 2095 screws (93.1%) being deemed clinically accurate. Furthermore, 5.4% (112/2088) of screws were reported as grade two breaches, 1.6% (33/2088) grade 3 breaches, 3.1% (29/926) medial breaches and 2.3% (21/926) lateral breaches. Mean linear deviation ranged from 1.3 to 5.99 mm, while mean angular/trajectory deviation ranged 1.6°-5.88°. CONCLUSION: The results of this study highlight the overall accuracy of ARSN pedicle screw placement. However, further robust prospective studies are needed to accurately compare to conventional methods of pedicle screw placement.

Assessing the utility of MRI-based vertebral bone quality (VBQ) for predicting lumbar pedicle screw loosening.

STUDY DESIGN: Retrospective cohort. OBJECTIVE: The purpose of this study is to assess the potential of utilizing the MRI-based vertebral bone quality (VBQ) score as a predictive tool for pedicle screw loosening (PSL) in patients who have undergone pedicle screw fixation and to identify risk factors associated with VBQ scores. METHODS: One hundred and sixteen patients who had undergone pedicle screw fixation between December 2019 and January 2021 and had more than a year of follow-up were divided into two groups of PSL and non-PSL. The radiological and clinical parameters investigated were age, gender, body mass index, the VBQ score, length of fusion and the DXA T-score. RESULTS: Of the 116 patients included in the study, 22 patients developed pedicle screw loosening after surgery (18.97%). VBQ score of PSL group was higher than the non-PSL group (3.61 ± 0.63 vs. 2. 86 ± 0.43, p < 0.001). According to logistic regression, PSL was independently linked with a higher VBQ score (OR = 3.555, 95% confidence interval [1.620-7.802], p < 0.005). The AUC of predicting screw loosening was 0.774 (p < 0.001) for VBQ score, and the best threshold was 3.055 (sensitivity, 81.8%; specificity, 71.3%). High VBQ score was associated with age (r (114) = 0.29, p = 0.002), while it was not negatively correlated with T-scores of each part. CONCLUSION: VBQ score is an independent predictor of pedicle screw loosening, with higher scores indicating a greater risk. Our results showed that older patients and women had higher VBQ scores.

Comparison of the clinical and radiographic outcomes of cortical bone trajectory and traditional trajectory pedicle screw fixation in transforaminal lumbar interbody fusion: a randomized controlled trial.

PURPOSE: To compare the clinical outcomes and radiographic outcomes of cortical bone trajectory (CBT) and traditional trajectory (TT) pedicle screw fixation in patients treated with single-level transforaminal lumbar interbody fusion (TLIF). METHODS: This trial included a total of 224 patients with lumbar spine disease who required single-level TLIF surgery. Patients were randomly assigned to the CBT and TT groups at a 1:1 ratio. Demographics and clinical and radiographic data were collected to evaluate the efficacy and safety of CBT and TT screw fixation in TLIF. RESULTS: The baseline characteristic data were similar between the CBT and TT groups. Back and leg pain for both the CBT and TT groups improved significantly from baseline to 24 months postoperatively. The CBT group experienced less pain than the TT group at one week postoperatively. The postoperative radiographic results showed that the accuracy of screw placement was significantly increased in the CBT group compared with the TT group (P < 0.05). The CBT group had a significantly lower rate of FJV than the TT group (P < 0.05). In addition, the rate of fusion and the rate of screw loosening were similar between the CBT and TT groups according to screw loosening criteria. CONCLUSION: This prospective, randomized controlled analysis suggests that clinical outcomes and radiographic characteristics, including fusion rates and caudal screw loosening rates, were comparable between CBT and TT screw fixation. Compared with the TT group, the CBT group showed advantages in the accuracy of screw placement and the FJV rate. CLINICAL TRIALS REGISTRATION: This trial has been registered at the US National Institutes of Health Clinical Trials Registry: NCT03105167.

Effect of L5 spinal canal type on pedicle screw placement based on CT imaging: a retrospective clinical study.

PURPOSE: The objective of this study was to investigate the optimal entry point and pedicle camber angle for L5 pedicle screws of different canal types. METHODS: CT imaging data were processed by Mimics for simulated pedicle screw placement, and PD (Pedicle diameter), PCA (Pedicle camber angle), LD (Longitudinal distance), TD (Transverse distance), and PBG (Pedicle screw breach grade) were measured. Then they were divided into the Round group and Trefoil group according to the type of spinal canal. When comparing PD, PCA, LD, TD, and PBG, the two sides of the pedicle were compared separately, so they were first divided into the round-type pedicle group and the trefoil-type pedicle group. RESULTS: In the round-type pedicle group (n = 134) and the trefoil-type pedicle group (n = 264), there was no significant difference in PD and LD, but there was a significant difference in PCA between the two groups (t = - 4.072, P < 0.05). A statistically significant difference in the distance of the Magerl point relative to the optimal entry point (t = - 3.792, P < 0.05), and the distance of the Magerl point relative to the optimal entry point was greater in the trefoil-type pedicle group than in the round-type pedicle group. CONCLUSION: The optimal entry point for L5 is more outward than the Magerl point, and the Trefoil spinal canal L5 is more outwardly oriented than the Round spinal canal L5, with a greater angle of abduction during pedicle screw placement.

Evaluating a cutting-edge augmented reality-supported navigation system for spinal instrumentation.

OBJECTIVE: Dorsal instrumentation using pedicle screws is a standard treatment for multiple spinal pathologies, such as trauma, infection, or degenerative indications. Intraoperative three-dimensional (3D) imaging and navigated pedicle screw placement are used at multiple centers. For the present study, we evaluated a new navigation system enabling augmented reality (AR)-supported pedicle screw placement while integrating navigation cameras into the reference array and drill guide. The present study aimed to evaluate its clinical application regarding safety, efficacy, and accuracy. METHODS: A total of 20 patients were operated on between 06/2021 and 01/2022 using the new technique for intraoperative navigation. Intraoperative data with a focus on accuracy and patient safety, including patient outcome, were analyzed. The accuracy of pedicle screw placement was evaluated by intraoperative CT imaging. RESULTS: A median of 8 (4-18) pedicle screws were placed in each case. Percutaneous instrumentation was performed in 14 patients (70%). The duration of pedicle screw placement (duration scan-scan) was 56 ± 26 (30-107) min. Intraoperative screw revision was necessary for 3 of 180 pedicle screws (1.7%). Intraoperatively, no major complications occurred-one case of delay due to software issues and one case of difficult screw placement were reported. CONCLUSION: The current study's results could confirm the use of the present AR-supported system for navigated pedicle screw placement for dorsal instrumentation in clinical routine. It provides a reliable and safe tool for 3D imaging-based pedicle screw placement, only requires a minimal intraoperative setup, and provides new opportunities by integrating AR.

Learning curve of junior surgeons in robot-assisted pedicle screw placement: a comparative cohort study.

OBJECTIVE: Robot-assisted technology has been gradually applied to pedicle screw placement in spinal surgery. This study was designed to detailedly evaluate the learning curve of junior surgeons in robot-assisted spine surgery. METHODS: From December 2020 to February 2022, 199 patients requiring surgical treatment with posterior pedicle screw fixation were prospectively recruited into the study. The patients were randomized to the robot-assisted group (the RA group) or the conventional freehand group (the CF group). Under the senior specialist's supervision, pedicle screws were placed by two junior fellows without prior experience. Cumulative summation (CUSUM) analysis was performed on the learning curve of pedicle screw placement for performing quantitative assessment based on the time of screw insertion. RESULTS: In total, 769 and 788 pedicle screws were placed in the RA and CF groups. Compared with the CF group, the learning duration in the RA group was shorter in the upper thoracic region (57 vs. 70 screws), but longer in the lower thoracic (62 vs. 58 screws) and the lumbosacral region (56 vs. 48 screws). The slope of learning curve was lower in the RA group than in the CF group. The screw accuracy in the RA group was superior to that in the CF group, especially in upper thoracic region (89.4% vs. 76.7%, P < 0.001). This disparity of accuracy became wider in deformity cases. In the upper thoracic region, the mean placement time was 5.34 ± 1.96 min in the RA group and 5.52 ± 2.43 min in the CF groups, while in the lower thoracic and lumbosacral regions, the CF group's mean placement times were statistically shorter. Three screw-related neural complications occurred in the CF group. CONCLUSION: Robot-assisted technique has its advantages in the upper thoracic region and deformity cases, which is easier and safer to insert pedicle screws. The robot-assisted technique allowed a short learning curve for junior surgeons and exhibited consistently excellent results even in the early application period.

Impact of intraoperative imaging on decision-making during spine surgery: a survey among spine surgeons using simulated intraoperative images.

PURPOSE: To assess whether the intention to intraoperatively reposition pedicle screws differs when spine surgeons evaluate the same screws with 2D imaging or 3D imaging. METHODS: In this online survey study, 21 spine surgeons evaluated eight pedicle screws from patients who had undergone posterior spinal fixation. In a simulated intraoperative setting, surgeons had to decide if they would reposition a marked pedicle screw based on its position in the provided radiologic imaging. The eight assessed pedicle screws varied in radiologic position, including two screws positioned within the pedicle, two breaching the pedicle cortex < 2 mm, two breaching the pedicle cortex 2-4 mm, and two positioned completely outside the pedicle. Surgeons assessed each pedicle screw twice without knowing and in random order: once with a scrollable three-dimensional (3D) image and once with two oblique fluoroscopic two-dimensional (2D) images. RESULTS: Almost all surgeons (19/21) intended to reposition more pedicle screws based on 3D imaging than on 2D imaging, with a mean number of pedicle screws to be repositioned of, respectively, 4.1 (± 1.3) and 2.0 (± 1.3; p < 0.001). Surgeons intended to reposition two screws placed completely outside the pedicle, one breaching 2-4mm, and one breaching < 2 mm more often based on 3D imaging. CONCLUSION: When provided with 3D imaging, spine surgeons not only intend to intraoperatively reposition pedicle screws at risk of causing postoperative complications more often but also screws with acceptable positions. This study highlights the potential of intraoperative 3D imaging as well as the need for consensus on how to act on intraoperative 3D information.

Posterior-only approach cervical hemivertebrectomy and short fusion with pedicle screws in young children with cervical scoliosis: case report and technical note.

PURPOSE: Cervical hemivertebrae (C3-6) causing significant osseous torticollis, head tilt and facial asymmetry are rare and complicated. Cervical hemivertebrectomy (CHVE) by a posterior-only approach was never reported because it is highly risky and its efficacy remains controversial. This study is to evaluate the feasibility and preliminary clinical outcomes of posterior-only approach for CHVE and torticollis correction in young children. METHODS: Four young children aged 5-9 years old with significant torticollis caused by cervical hemivertebrae underwent deformity correction consisting of cervical pedicle screw (CPS) placement with O-arm-based intraoperative navigation, CHVE using ultrasonic bone scalpel and short-segmental posterior instrumentation and fusion. Details of this novel technique were presented. The preliminary short-term clinical and radiographic outcomes were assessed. RESULTS: On average, the operative time was 312.5 ± 49.9 min, and the surgical blood loss was 375.0 ± 150.0 ml. The structural cervical scoliosis was corrected from 31.5 ± 7.3° to 11.0 ± 4.1°, and the average correction rate was 64.9%. Head tilt was favorably corrected from 11.0 ± 4.2° to 3.5 ± 2.6°. The shoulder balance improved from 6.3 ± 1.3° to 1.5 ± 1.9°. One case with C6 CHVE had convex side radiating nerve root pain but no sign of muscle power weakness. Full recovery was achieved one month after surgery. No other complication occurred. CONCLUSIONS: CHVE by a posterior-only approach was a feasible alternative option for the treatment of congenital cervical scoliosis. It could resect the CHV effectively and achieve satisfactory torticollis correction without additional anterior access surgery. Successful CPS placement in this child population was essentially important to enable reliable osteotomy closure and firm posterior instrumentation.

Myelopathy resulting from degenerative atlantoaxial subluxation.

PURPOSE: To present the clinical features and treatment strategy of degenerative atlantoaxial subluxation (DAAS). METHODS: Patients with DAAS treated in our institution from 2003 to 2020 were retrospectively reviewed. We utilized the Japanese Orthopedic Association (JOA) scale to evaluate the neurologic status and distance of Ranawat et al. (DOR) to measure vertical migration. RESULTS: We recruited 40 patients with > 2 years of follow-up and an average age of 62.3 ± 7.7 years. All the patients had myelopathy; only one patient had moderate trauma before exacerbation of symptoms, and the duration of symptoms was 34 ± 36 months. The most frequent radiological features were vertical migration of C1 (100%), sclerosis (100%), and narrowing of the atlantoaxial lateral mass articulations (100%). Two patients underwent transoral release combined with posterior reduction and fusion, and 38 patients underwent posterior reduction and fusion with C1 lateral mass screws-C2 pedicle screws and plate systems only. Forty cases (100%) achieved a solid atlantoaxial fusion, and 38 cases (95%) achieved anatomic atlantoaxial reduction. The JOA score increased from 9.3 ± 2.6 to 14.8 ± 2.1 (P < 0.01). DOR increased from 14.5 ± 2.5 to 17.8 ± 2.2 mm at the final follow-up (P < 0.01). Loosening of the locking caps was detected in one case, bony fusion was achieved, and harvest-site pain was reported in five patients. CONCLUSION: DAAS differs from other types of AAS and presents with anterior subluxation combined with vertical subluxation arising from degenerative changes in the atlantoaxial joints. We recommend anatomic reduction as an optimal strategy for DAAS.

Minimally invasive transforaminal lumbar interbody fusion with unilateral pedicle screw fixation (UNILF): outcomes at 7 years.

PURPOSE: To assess clinical, functional and radiographical results of one-level minimally invasive transforaminal interbody fusion with unilateral pedicle screw fixation (UNILIF) in the treatment of stable lumbar degenerative diseases with a minimum of 5 years of follow-up. MATERIAL AND METHOD: From January 2012 to December 2016, clinical and radiological data of patients with degenerative lumbar disease managed by UNILIF were prospectively collected. Patients with a follow-up that ended before 5 years were excluded. SF-12, Oswestry disability index (ODI) and visual analog scale (VAS) were collected preoperatively, at 2 years and at the last follow-up. A full-spine standing radiograph was performed at each follow-up appointment. RESULTS: Mean operative time was 74.7 (± 19) minutes, mean blood loss was 131.1 (± 207) ml and mean follow-up was 7.5 (± 1.7) years. All functional scores and VAS were significantly improved between the preoperative and the 2 years postoperative. Between the 2 years postoperative and the last follow-up ODI and VAS continued to significantly improved. Fusion rate was 98.6% on radiographic analysis at follow-up. CONCLUSION: UNILIF method is a safe and effective surgical strategy. It provides a durable improvement in functional score over 7 years of follow-up with a stable radiological correction over time.

The effect of C2 screw type on perioperative outcomes and long-term stability after C2-T2 posterior cervical decompression and fusion.

PURPOSE: To determine if C2 pedicle versus pars screw type predicts change in fusion status, C2 screw loosening, cervical alignment, and patient-reported outcomes measures (PROMs) after C2-T2 posterior cervical decompression and fusion (PDCF). METHODS: All adult patients who underwent C2-T2 PCDF for myelopathy or myeloradiculopathy between 2013-2020 were retrospectively identified. Patients were dichotomized by C2 screw type into bilateral C2 pedicle and bilateral C2 pars screw groups. Preoperative and short- and long-term postoperative radiographic outcomes and PROMs were collected. Univariate and multivariate analysis compared patient factors, fusion status, radiographic measures, and PROMs across groups. RESULTS: A total of 159 patients met the inclusion/exclusion criteria (76 bilateral pedicle screws, 83 bilateral pars screws). Patients in the C2 pars relative to C2 pedicle screw group were on average more likely to have bone morphogenic protein (p = 0.001) and four-millimeter diameter rods utilized intraoperatively (p = 0.033). There were no significant differences in total construct and C2-3 fusion rate, C2 screw loosening, or complication and revision rates between C2 screw groups in univariate and regression analysis. Changes in C2 tilt, C2-3 segmental lordosis, C0-2 Cobb angle, proximal junctional kyphosis, atlanto-dens interval, C1 lamina-occiput distance, C2 sagittal vertical axis, C2-7 lordosis, and PROMs at all follow-up intervals did not vary significantly by C2 screw type. CONCLUSION: There were no significant differences in fusion status, hardware complications, and radiographic and clinical outcomes based on C2 screw type following C2-T2 PCDF. Accordingly, intraoperative usage criteria can be flexible based on patient vertebral artery positioning and surgeon comfort level.