External Validation of Predictive Models for Failed Medical Management of Spinal Epidural Abscess.

OBJECTIVE: There is limited consensus regarding management of spinal epidural abscesses (SEA), particularly in patients without neurologic deficits. Several models have been created to predict failure of medical management in patients with SEA. We evaluate the external validity of five predictive models in an independent cohort of patients with SEA. METHODS: 176 patients with SEA between 2010 and 2019 at our institution were identified, and variables relevant to each predictive model were collected. Published prediction models were used to assign probability of medical management failure to each patient. Predicted probabilities of medical failure and actual patient outcomes were used to create Receiver Operating Characteristic (ROC) curves, with the area under the ROC curve (AUROC) used to quantify a model's discriminative ability. Calibration curves were plotted using predicted probabilities and actual outcomes. The Spiegelhalter Z-test was used to determine adequate model calibration. RESULTS: One model (Kim et al.) demonstrated good discriminative ability and adequate model calibration in our cohort (ROC = 0.831, p-value = 0.83). Parameters included in the model were age >65, diabetes, MRSA infection, and neurologic impairment. Four additional models did not perform well for discrimination or calibration metrics (Patel et al., ROC=0.580, p=<0.0001; Shah et al., ROC=0.653, p=<0.0001; Baum et al., ROC=0.498, p=<0.0001; Page et al., ROC=0.534, p=<0.0001). CONCLUSION: Only one published predictive model demonstrated acceptable discrimination and calibration in our cohort, suggesting limited generalizability of the evaluated models. Multi-institutional data may facilitate the development of widely applicable models to predict medical management failure in patients with SEA.

Synthesis and evaluation of a novel vancomycin-infused, biomimetic bone graft using a rat model of spinal implant-associated infection.

Background: Postoperative infection is a complication of spinal fusion surgery resulting in increased patient morbidity. Strategies including intraoperative application of powdered vancomycin have been proposed to reduce the incidence of infection; however, such antimicrobial effects are short-lived. Methods: Instrumentation of the L4-L5 vertebrae was performed mimicking pedicle screw and rod fixation in 30 rats. Titanium instrumentation inoculated with either PBS or 1×105 CFU bioluminescent MRSA, along with biomimetic bone grafts infused with varying concentrations of vancomycin and 125 µg of rhBMP-2 (BioMim-rhBMP-2-VCM) were implanted prior to closure. Infection was quantified during the six-week postoperative period using bioluminescent imaging. Arthrodesis was evaluated using micro-CT. Results: Infected animals receiving a bone graft infused with low-dose (0.18 mg/g) or high-dose vancomycin (0.89 mg/g) both exhibited significantly lower bioluminescent signal over the six-week postoperative period than control animals inoculated with MRSA and implanted with bone grafts lacking vancomycin (p=.019 and p=.007, respectively). Both low and high-dose vancomycin-infused grafts also resulted in a statistically significant reduction in average bioluminescence when compared to control animals (p=.027 and p=.047, respectively), independent of time. MicroCT analysis of animals from each group revealed pseudoarthrosis only in the control group, suggesting a correlation between infection and pseudoarthrosis. MRSA-inoculated control animals also had significantly less bone volume formation on micro-CT than the PBS-inoculated control cohort (p<.001), the MRSA+low-dose vancomycin-infused bone graft cohort (p<.001), and the MRSA+high-dose vancomycin-infused bone graft cohort (p<.001). Conclusion: BioMim-rhBMP-2-VCM presents a novel tissue engineering approach to simultaneously promoting arthrodesis and antimicrobial prophylaxis in spinal fusion. Despite mixed evidence of potential osteotoxicity of vancomycin reported in literature, BioMim-rhBMP-2-VCM preserved arthrodesis and osteogenesis with increasing vancomycin loading doses due to the graft's osteoinductive composition.

Deformable registration of preoperative MR and intraoperative long-length tomosynthesis images for guidance of spine surgery via image synthesis.

PURPOSE: Improved integration and use of preoperative imaging during surgery hold significant potential for enhancing treatment planning and instrument guidance through surgical navigation. Despite its prevalent use in diagnostic settings, MR imaging is rarely used for navigation in spine surgery. This study aims to leverage MR imaging for intraoperative visualization of spine anatomy, particularly in cases where CT imaging is unavailable or when minimizing radiation exposure is essential, such as in pediatric surgery. METHODS: This work presents a method for deformable 3D-2D registration of preoperative MR images with a novel intraoperative long-length tomosynthesis imaging modality (viz., Long-Film [LF]). A conditional generative adversarial network is used to translate MR images to an intermediate bone image suitable for registration, followed by a model-based 3D-2D registration algorithm to deformably map the synthesized images to LF images. The algorithm's performance was evaluated on cadaveric specimens with implanted markers and controlled deformation, and in clinical images of patients undergoing spine surgery as part of a large-scale clinical study on LF imaging. RESULTS: The proposed method yielded a median 2D projection distance error of 2.0 mm (interquartile range [IQR]: 1.1-3.3 mm) and a 3D target registration error of 1.5 mm (IQR: 0.8-2.1 mm) in cadaver studies. Notably, the multi-scale approach exhibited significantly higher accuracy compared to rigid solutions and effectively managed the challenges posed by piecewise rigid spine deformation. The robustness and consistency of the method were evaluated on clinical images, yielding no outliers on vertebrae without surgical instrumentation and 3% outliers on vertebrae with instrumentation. CONCLUSIONS: This work constitutes the first reported approach for deformable MR to LF registration based on deep image synthesis. The proposed framework provides access to the preoperative annotations and planning information during surgery and enables surgical navigation within the context of MR images and/or dual-plane LF images.

Augmented Reality and Virtual Reality in Spine Surgery: A Comprehensive Review.

Augmented reality (AR) and virtual reality (VR) are powerful technologies with proven utility and tremendous potential. Spine surgery, in particular, may benefit from these developing technologies for resident training, preoperative education for patients, surgical planning and execution, and patient rehabilitation. In this review, the history, current applications, challenges, and future of AR/VR in spine surgery are examined.

Concomitant Traumatic Brain Injury Delays Surgery in Patients With Traumatic Spinal Cord Injury.

BACKGROUND AND OBJECTIVES: Growing evidence supports prompt surgical decompression for patients with traumatic spinal cord injury (tSCI). Rates of concomitant tSCI and traumatic brain injury (TBI) range from 10% to 30%. Concomitant TBI may delay tSCI diagnosis and surgical intervention. Little is known about real-world management of this common injury constellation that carries significant clinical consequences. This study aimed to quantify the impact of concomitant TBI on surgical timing in a national cohort of patients with tSCI. METHODS: Patient data were obtained from the National Trauma Data Bank (2007-2016). Patients admitted for tSCI and who received surgical intervention were included. Delayed surgical intervention was defined as surgery after 24 hours of admission. Multivariable hierarchical regression models were constructed to measure the risk-adjusted association between concomitant TBI and delayed surgical intervention. Secondary outcome included favorable discharge status. RESULTS: We identified 14 964 patients with surgically managed tSCI across 377 North American trauma centers, of whom 2444 (16.3%) had concomitant TBI and 4610 (30.8%) had central cord syndrome (CCS). The median time to surgery was 20.0 hours for patients without concomitant TBI and 24.8 hours for patients with concomitant TBI. Hierarchical regression modeling revealed that concomitant TBI was independently associated with delayed surgery in patients with tSCI (odds ratio [OR], 1.3; 95% CI, 1.1-1.6). Although CCS was associated with delayed surgery (OR, 1.5; 95% CI, 1.4-1.7), we did not observe a significant interaction between concomitant TBI and CCS. In the subset of patients with concomitant tSCI and TBI, patients with severe TBI were significantly more likely to experience a surgical delay than patients with mild TBI (OR, 1.4; 95% CI, 1.0-1.9). CONCLUSION: Concomitant TBI delays surgical management for patients with tSCI. This effect is largest for patients with tSCI with severe TBI. These findings should serve to increase awareness of concomitant TBI and tSCI and the likelihood that this may delay time-sensitive surgery.

Augmented reality in spine surgery - past, present, and future.

BACKGROUND CONTEXT: Augmented reality (AR) is increasingly recognized as a valuable tool in spine surgery. Here we provides an overview of the key developments and technological milestones that have laid the foundation for AR applications in this field. We also assess the quality of existing studies on AR systems in spine surgery and explore potential future applications. PURPOSE: The purpose of this narrative review is to examine the role of AR in spine surgery. It aims to highlight the evolution of AR technology in this context, evaluate the existing body of research, and outline potential future directions for integrating AR into spine surgery. STUDY DESIGN: Narrative review. METHODS: We conducted a thorough literature search to identify studies and developments related to AR in spine surgery. Relevant articles, reports, and technological advancements were analyzed to establish the historical context and current state of AR in this field. RESULTS: The review identifies significant milestones in the development of AR technology for spine surgery. It discusses the growing body of research and highlights the strengths and weaknesses of existing investigations. Additionally, it presents insights into the potential for AR to enhance spine surgical education and speculates on future applications. CONCLUSIONS: Augmented reality has emerged as a promising adjunct in spine surgery, with notable advancements and research efforts. The integration of AR into the spine surgery operating room holds promise, as does its potential to revolutionize surgical education. Future applications of AR in spine surgery may include real-time navigation, enhanced visualization, and improved patient outcomes. Continued development and evaluation of AR technology are essential for its successful implementation in this specialized surgical field.

Assessing the Accuracy of Spinal Instrumentation Using Augmented Reality (AR): A Systematic Review of the Literature and Meta-Analysis.

Technological advancements, particularly in the realm of augmented reality (AR), may facilitate more accurate and precise pedicle screw placement. AR integrates virtual data into the operator's real-world view, allowing for the visualization of patient-specific anatomy and navigated trajectories. We aimed to conduct a meta-analysis of the accuracy of pedicle screw placement using AR-based systems. A systematic review of the literature and meta-analysis was performed using the PubMed/MEDLINE database, including studies reporting the accuracy of pedicle screw placement using AR. In total, 8 studies with 163 patients and 1259 screws were included in the analysis. XVision (XVS) was the most commonly used AR system (595 screws) followed by the Allura AR surgical navigation system (ARSN) (462 screws). The overall accuracy was calculated as 97.2% (95% CI 96.2-98.1% p < 0.001). Subgroup analysis revealed that there was no statistically significant difference in the accuracy rates achieved by XVS and Allura ARSN (p = 0.092). AR enables reliable, accurate placement of spinal instrumentation. Future research efforts should focus on comparative studies, cost effectiveness, operative time, and radiation exposure.

Reduction of cervicothoracic spondyloptosis in an ambulatory patient: when traction fails.

INTRODUCTION: Cervical spondyloptosis is a rare complication of high-energy trauma which often results in significant patient morbidity and mortality. The authors present a case of spondyloptosis of C7 over T1 with minimal radicular symptoms and otherwise complete spinal cord sparing. This case highlights the surgical challenges faced with cervical spondyloptosis and the techniques used when traction fails. CASE PRESENTATION: A 21-year-old man with no significant past medical history presented after a high-speed motor vehicle collision with cervicothoracic pain and mild hand grip weakness in addition to numbness of the fourth and fifth digits bilaterally (American Spinal Injury Association Impairment Scale Grade D). Computed tomography imaging revealed spondyloptosis of C7 over T1, a fracture of the C2 vertebral body, and a burst fracture of C3. To relieve spinal cord compression and restore sagittal realignment, closed reduction was attempted, however this resulted in perching of the bilateral C7-T1 facets, leading to an open posterior approach. The patient underwent C7 laminectomy, bilateral C7-T1 facetectomy, and manual reduction using a Mayfield skull clamp followed by C2-T3 fixation. Postoperatively, pain was diminished, sensory disturbances were resolved and the patient was otherwise neurologically stable. DISCUSSION: There is a role for closed traction for reduction of cervical spondyloptosis, however, its role is debated especially when the patient is predominately neurologically intact. In this setting, the spine surgeon may be required to change traction and operative strategies in order to minimize potentially harmful manipulation while restoring sagittal realignment and stabilizing the spine for preservation of neurological function.

Interventional approaches to symptomatic Tarlov cysts: a 15-year institutional experience.

BACKGROUND: Tarlov cysts are perineural collections of cerebrospinal fluid most often affecting sacral nerve roots, which may cause back pain, extremity paresthesias and weakness, bladder/bowel dysfunction, and/or sexual dysfunction. The most effective treatment of symptomatic Tarlov cysts, with options including non-surgical management, cyst aspiration and injection of fibrin glue, cyst fenestration, and nerve root imbrication, is debated. METHODS: Retrospective chart review was conducted for 220 patients with Tarlov cysts seen at our institution between 2006 and 2021. Logistic regression analysis was conducted to determine the association between treatment modality, patient characteristics, and clinical outcome. RESULTS: Seventy-two (43.1%) patients with symptomatic Tarlov cysts were managed non-surgically. Of the 95 patients managed interventionally, 71 (74.7%) underwent CT-guided aspiration of the cyst with injection of fibrin glue; 17 (17.9%) underwent cyst aspiration alone; 5 (5.3%) underwent blood patching; and 2 (2.1%) underwent more than one of the aforementioned procedures. Sixty-six percent of treated patients saw improvement in one or more symptoms, with the most improvement in patients after aspiration of cyst with injection of fibrin glue; however, this association was not statistically significant on logistic regression analysis. CONCLUSION: Although the subtype of percutaneous treatment was not significantly associated with optimal or suboptimal patient outcomes, cyst aspiration both with and without injection of fibrin glue may serve as a useful diagnostic tool to (1) determine symptom etiology and (2) identify patients who might have achieved temporary improvement between the time of cyst aspiration and refill with cerebrospinal fluid as potential candidates for neurosurgical intervention of cyst fenestration and nerve root imbrication.

Contemporary Trends in Minimally Invasive Sacroiliac Joint Fusion Utilization in the Medicare Population by Specialty.

BACKGROUND AND OBJECTIVES: Sacroiliac (SI) joint dysfunction constitutes a leading cause of pain and disability. Although surgical arthrodesis is traditionally performed under open approaches, the past decade has seen a rise in minimally invasive surgical (MIS) techniques and new federally approved devices for MIS approaches. In addition to neurosurgeons and orthopedic surgeons, proceduralists from nonsurgical specialties are performing MIS procedures for SI pathology. Here, we analyze trends in SI joint fusions performed by different provider groups, along with trends in the charges billed and reimbursement provided by Medicare. METHODS: We review yearly Physician/Supplier Procedure Summary data from 2015 to 2020 from the Centers for Medicare and Medicaid Services for all SI joint fusions. Patients were stratified as undergoing MIS or open procedures. Utilization was adjusted per million Medicare beneficiaries and weighted averages for charges and reimbursements were calculated, controlling for inflation. Reimbursement-to-charge (RCR) ratios were calculated, reflecting the proportion of provider billed amounts reimbursed by Medicare. RESULTS: A total of 12 978 SI joint fusion procedures were performed, with the majority (76.5%) being MIS procedures. Most MIS procedures were performed by nonsurgical specialists (52.1%) while most open fusions were performed by spine surgeons (71%). Rapid growth in MIS procedures was noted for all specialty categories, along with an increased number of procedures offered in the outpatient setting and ambulatory surgical centers. The overall RCR increased over time and was ultimately similar between spine surgeons (RCR = 0.26) and nonsurgeon specialists (RCR = 0.27) performing MIS procedures. CONCLUSION: Substantial growth in MIS procedures for SI pathology has occurred in recent years in the Medicare population. This growth can largely be attributed to adoption by nonsurgical specialists, whose reimbursement and RCR increased for MIS procedures. Future studies are warranted to better understand the impact of these trends on patient outcomes and costs.

Patient Optimization for the Prevention of Proximal Junctional Kyphosis.

Proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) are well-recognized challenges of surgery for adult spinal deformity (ASD). Multiple risk factors have been identified for PJK/PJF, including osteoporosis, frailty, neurodegenerative disease, obesity, and smoking. Several surgical techniques to mitigate risk of PJK/PJF have been identified; however, patient optimization is also critical. This review summarizes the data behind these 5 risk factors (osteoporosis, frailty, neurodegenerative disease, obesity, and smoking) and details the related recommendations for patients undergoing surgery for ASD.

A novel rodent model of chronic spinal implant-associated infection.

BACKGROUND CONTEXT: Bacterial infection of spinal instrumentation is a significant challenge in spinal fusion surgery. Although the intraoperative local application of powdered vancomycin is common practice for mitigating infection, the antimicrobial effects of this route of administration are short-lived. Therefore, novel antibiotic-loaded bone grafts as well as a reliable animal model to permit the testing of such therapies are needed to improve the efficacy of infection reduction practices in spinal fusion surgery. PURPOSE: This study aims to establish a clinically relevant rat model of spinal implant-associated infection to permit the evaluation of antimicrobial bone graft materials used in spinal fusion. STUDY DESIGN: Rodent study of chronic spinal implant-associated infection. METHODS: Instrumentation anchored in and spanning the vertebral bodies of L4 and L5 was inoculated with bioluminescent methicillin-resistant Staphylococcus aureus bacteria (MRSA). Infection was monitored using an in vivo imaging system (IVIS) for 8 weeks. Spines were harvested and evaluated histologically, and colony-forming units (CFUs) were quantified in harvested implants and spinal tissue. RESULTS: Postsurgical analysis of bacterial infection in vivo demonstrated stratification between MRSA and phosphate-buffered saline (PBS) control groups during the first 4 weeks of the 8-week infection period, indicating the successful establishment of acute infection. Over the 8-week chronic infection period, groups inoculated with 1 × 105 MRSA CFU and 1 × 106 MRSA CFU demonstrated significantly higher bioluminescence than groups inoculated with PBS control (p = 0.009 and p = 0.041 respectively). Histological examination at 8 weeks postimplantation revealed the presence of abscesses localized to implant placement in all MRSA inoculation groups, with the most pervasive abscess formation in samples inoculated with 1 × 105 MRSA CFU and 1 × 106 MRSA CFU. Quantification of CFU plated from harvested spinal tissue at 8 weeks post-implantation revealed the 1 × 105 MRSA CFU inoculation group as the only group with a significantly greater average CFU count compared to PBS control (p = 0.017). Further, CFU quantification from harvested spinal tissue was greater than CFU quantification from harvested implants across all inoculation groups. CONCLUSION: Our model demonstrated that the inoculation dosage of 1 × 105 MRSA CFU exhibited the most robust chronic infection within instrumented vertebral bodies. This dosage had the greatest difference in bioluminescence signal from control (p < 0.01), the lowest mortality (0% compared to 50% for samples inoculated with 1 × 106 MRSA CFU), and a significantly higher amount of CFUs from harvested spine samples than CFUs from control harvested spine samples. Further, histological analysis confirmed the reliability of this novel rodent model of implanted-associated infection to establish infection and biofilm formation of MRSA for all inoculation groups. CLINICAL SIGNIFICANCE: This model is intended to simulate the infection of instrumentation used in spinal fusion surgeries concerning implant locality and material. This model may evaluate potential antimicrobial and osteogenic biomaterials and investigate the relationship between implant-associated infection and failed fusion.

In-Human Report of S2 Alar-Iliac Screw Placement Using Augmented Reality Assistance.

BACKGROUND: S2 alar-iliac (S2AI) screws provide spinopelvic fixation with the advantages of minimized dissection, easier rod contouring, and decreased symptomatic screw-head prominence. However, placement of S2AI screws may be challenging because of the anatomy of the lumbosacral junction. Augmented reality is a nascent technology that may enhance placement of S2AI screws. OBJECTIVE: To report the first in-human placement of augmented reality (AR)-assisted S2 alar-iliac screws and evaluate the accuracy of screw placement. METHODS: A retrospective review was performed of patients who underwent AR-assisted S2AI screw placement. All surgeries were performed by 2 neurosurgeons using an AR head-mounted display (Xvision, Augmedics). Screw accuracy was analyzed in a blinded fashion by an independent neuroradiologist using the cortical breach grading scale. RESULTS: Twelve patients underwent AR-assisted S2AI screw placement for a total of 23 screws. Indications for surgery included deformity, degenerative disease, and tumor. Twenty-two screws (95.6%) were accurate-defined as grade 0 or grade 1. Twenty-one screws (91.3%) were classified as grade 0, 1 screw (4.3%) was grade 1, and 1 screw (4.3%) was grade 3. All breaches were asymptomatic. CONCLUSION: AR-assisted S2AI screw placement had an overall accuracy rate of 95.6% (grade 0 and grade 1 screws) in a cohort of 12 patients and 23 screws. This compares favorably with freehand and robotic placement. 1,2 AR enables spine surgeons to both better visualize anatomy and accurately place spinal instrumentation. Future studies are warranted to research the learning curve and cost analysis of AR-assisted spine surgery.

Delays in Presentation After Traumatic Spinal Cord Injury-A Systematic Review.

BACKGROUND: Prompt surgical decompression after traumatic spinal cord injury (TSCI) may be associated with improved sensorimotor outcomes. Delays in presentation may prevent timely decompression after TSCI. OBJECTIVE: To systematically review existing studies investigating delays in presentation after TSCI in low- and middle-income countries (LMICs) and high-income countries (HICs). METHODS: A systematic review was conducted and studies featuring quantitative or qualitative data on prehospital delays in TSCI presentation were included. Studies lacking quantitative or qualitative data on prehospital delays in TSCI presentation, case reports or series with <5 patients, review articles, or animal studies were excluded from our analysis. RESULTS: After exclusion criteria were applied, 24 studies were retained, most of which were retrospective. Eleven studies were from LMICs and 13 were from HICs. Patients with TSCI in LMICs were younger than those in HICs, and most patients were male in both groups. A greater proportion of patients with TSCI in studies from LMICs presented >24 hours after injury (HIC average proportion, 12.0%; LMIC average proportion, 49.9%; P = 0.01). Financial barriers, lack of patient awareness and education, and prehospital transportation barriers were more often cited as reasons for delays in LMICs than in HICs, with prehospital transportation barriers cited as a reason for delay by every LMIC study included in this review. CONCLUSIONS: Disparities in prehospital infrastructure between HICs and LMICs subject more patients in LMICs to increased delays in presentation to care.

Recruitment of women in neurosurgery: a 7-year quantitative analysis.

OBJECTIVE: The authors aimed to characterize which US medical schools have the most female neurosurgery residents and to identify potential associations between medical school characteristics and successful recruitment of women pursuing a neurosurgery career. METHODS: The authors evaluated a total of 1572 residents in US neurosurgery programs accredited by the Accreditation Council for Graduate Medical Education as of February 2021, representing match cohorts from 2014 to 2020. The authors extracted US medical school characteristics and ranked schools based on the percentages of women graduates entering neurosurgery. They additionally studied yearly trends of the percentage of women constituting incoming neurosurgery resident cohorts as well as associations between female recruitment percentage and medical school characteristics using univariable and stepwise multivariable linear regression (including significant univariable factors). RESULTS: The cohort consisted of 1255 male and 317 (20%) female residents. Yearly trends indicated a significant drop in incoming female residents in 2016, followed by significant increases in 2017 and 2019. On multivariable analysis, the following factors were associated with a higher average percentage of female graduates entering neurosurgery: total affiliated neurosurgery clinical faculty (ß = 0.006, 95% CI 0.001-0.011, p = 0.01), allopathic versus osteopathic schools (ß = 0.231, 95% CI 0.053-0.409, p = 0.01), and top 10 U.S. News & World Report ranking (ß = 0.380, 95% CI 0.129-0.589, p < 0.01). When the number of female clinical faculty was added to the model, the variable was not statistically significant. Multivariable bibliometric analyses indicated a higher mean preresidency H-index for men, with an even greater gender difference identified in the 2021 H-index. CONCLUSIONS: This study characterizes which medical schools are most successful at recruiting female students who constituted the total neurosurgery resident workforce of the 2020-2021 academic year. The overall number of clinical neurosurgery faculty rather than faculty gender was independently associated with female recruitment. Gender differences in research productivity persisted with control for confounders and increased between preresidency and 2021 time points. Such understanding of factors that influence the recruitment of women can help improve female representation in neurosurgery residency training moving forward.

Management of traumatic sacral spondyloptosis: illustrative case.

BACKGROUND: Grade V spondylolisthesis, or spondyloptosis, is a complication of high-energy trauma that is most commonly reported at the lumbosacral junction. Sacral intersegmental spondyloptosis is extremely rare. The authors present a case of spondyloptosis of S1 on S2 with a comminuted fracture of S2 and complex fractures of the L4 and L5 transverse processes, resulting in severe stenosis of the lumbosacral nerve roots. OBSERVATIONS: The patient was a 70-year-old woman with a history of a fall 3 weeks prior and progressive L5 and S1 radiculopathy. Instrumentation and fusion were undertaken, extending from L3 to the pelvis because degenerative stenosis at L3-4 and L4-5 was also found. Reduction was achieved, leading to diminished pain and partial resolution of weakness. LESSONS: Traumatic sacral spondyloptosis adds a degree of difficulty to reduction, fixation, and fusion. The technique presented herein achieved sagittal realignment via a distraction maneuver of S1-2 in which rods were attached to bilateral dual S2 alar-iliac screws with reduction screws placed at S1, ultimately pulling L5 and S1 up to the rod for fixation.

Deformable 3D-2D image registration and analysis of global spinal alignment in long-length intraoperative spine imaging.

BACKGROUND: Spinal deformation during surgical intervention (caused by patient positioning and/or the correction of malalignment) confounds conventional navigation due to the assumptions of rigid transformation. Moreover, the ability to accurately quantify spinal alignment in the operating room would provide an assessment of the surgical product via metrics that correlate with clinical outcomes. PURPOSE: A method for deformable 3D-2D registration of preoperative CT to intraoperative long-length tomosynthesis images is reported for an accurate 3D evaluation of device placement in the presence of spinal deformation and automated evaluation of global spinal alignment (GSA). METHODS: Long-length tomosynthesis ("Long Film," LF) images were acquired using an O-arm imaging system (Medtronic, Minneapolis USA). A deformable 3D-2D patient registration was developed using multi-scale masking (proceeding from the full-length image to local subvolumes about each vertebra) to transform vertebral labels and planning information from preoperative CT to the LF images. Automatic measurement of GSA (main thoracic kyphosis [MThK] and lumbar lordosis [LL]) was obtained using a spline fit to registered labels. The "Known-Component Registration" method for device registration was adapted to the multi-scale process for 3D device localization from orthogonal LF images. The multi-scale framework was evaluated using a deformable spine phantom in which pedicle screws were inserted, and deformations were induced over a range in LL ∼25°-80°. Further validation was carried out in a cadaver study with implanted pedicle screws and a similar range of spinal deformation. The accuracy of patient and device registration was evaluated in terms of 3D translational error and target registration error, respectively, and the accuracies of automatic GSA measurements were compared to manual annotation. RESULTS: Phantom studies demonstrated accurate registration via the multi-scale framework for all vertebral levels in both the neutral and deformed spine: median (interquartile range, IQR) patient registration error was 1.1 mm (0.7-1.9 mm IQR). Automatic measures of MThK and LL agreed with manual delineation within -1.1° ± 2.2° and 0.7° ± 2.0° (mean and standard deviation), respectively. Device registration error was 0.7 mm (0.4-1.0 mm IQR) at the screw tip and 0.9° (1.0°-1.5°) about the screw trajectory. Deformable 3D-2D registration significantly outperformed conventional rigid registration (p < 0.05), which exhibited device registration errors of 2.1 mm (0.8-4.1 mm) and 4.1° (1.2°-9.5°). Cadaver studies verified performance under realistic conditions, demonstrating patient registration error of 1.6 mm (0.9-2.1 mm); MThK within -4.2° ± 6.8° and LL within 1.7° ± 3.5°; and device registration error of 0.8 mm (0.5-1.9 mm) and 0.7° (0.4°-1.2°) for the multi-scale deformable method, compared to 2.5 mm (1.0-7.9 mm) and 2.3° (1.6°-8.1°) for rigid registration (p < 0.05). CONCLUSION: The deformable 3D-2D registration framework leverages long-length intraoperative imaging to achieve accurate patient and device registration over the extended lengths of the spine (up to 64 cm) even with strong anatomical deformation. The method offers a new means for the quantitative validation of spinal correction (intraoperative GSA measurement) and the 3D verification of device placement in comparison to preoperative images and planning data.

A biodegradable 3D woven magnesium-based scaffold for orthopedic implants.

Porous Magnesium (Mg) is a promising biodegradable scaffold for treating critical-size bone defects, and as an essential element for human metabolism, Mg has shown sufficient biocompatibility. Its elastic moduli and yield strengths are closer to those of cortical bone than common, inert metallic implants, effectively reducing stress concentrations around host tissue as well as stress shielding. More importantly, Mg can degrade and be absorbed in the human body in a safe and controlled manner, thereby reducing the need for second surgeries to remove implants. The development of porous Mg scaffolds via conventional selective laser melting techniques has been limited due to Mg's low boiling point, high vapor pressures, high reactivity, and non-ideal microstructures in additively manufactured parts. Here we present an exciting alternative to conventional additive techniques: 3D weaving with Mg wires that have controlled chemistries and microstructures. The weaving process offers high throughput manufacturing as well as porous architectures that can be optimized for stiffness and porosity with topology optimization. Once woven, we dip-coat the weaves with polylactic acid to enhance their strength and corrosion resistance. Following fabrication, we characterize their mechanical properties, corrosion behavior, and cell compatibilityin vitro, and we use an intramuscular implantation model to evaluate theirin vivocorrosion behavior and tissue response.

Adoption of awake spine surgery - trends from a national registry over 14 years.

BACKGROUND CONTEXT: Awake spine surgery is growing in popularity, and may facilitate earlier postoperative recovery, reduced cost, and fewer complications than spine surgery conducted under general anesthesia (GA). However, trends in the adoption of awake (ie, non-GA) spine surgery have not been previously studied. PURPOSE: To investigate temporal trends in non-GA spine surgery utilization and outcomes in the United States. STUDY DESIGN/SETTING: A retrospective observational study. PATIENT SAMPLE: Patients undergoing cervical or lumbar decompression or/and fusion from the American College of Surgeons National Surgical Quality Improvement Program database records dated 2005-2019. OUTCOME MEASURES: The primary outcome was the adoption trends of awake cervical and lumbar spine operations from 2005 to 2019. The secondary outcomes included the outcomes trends of 30-day complications, readmission rates, and length of stay in cervical and lumbar spine operations from 2005 to 2019. METHODS: Patients were stratified into two groups: GA and non-GA (regional, epidural, spinal, monitored anesthesia care/intravenous sedation). Pearson chi-square or Fisher exact test and independent-sample t test were used to compare demographics between groups. Jonckheere-Terpstra test was used to determine whether trends and outcomes of non-GA operations from 2005 to 2019 were statistically significant. No non-GA spine operations were reported in the database from 2005 to 2006. RESULTS: We included 301,521 patients who underwent cervical or lumbar spine operations from 2005 to 2019. GA was used in 294,903 (97.8%) operations; 6,618 (2.2%) operations were non-GA. Patients in the non-GA cohort were more likely to be younger (50.1 vs 57.2 years; p<.001), less likely to have American Society of Anesthesiologists classification ≥3 (39.7% vs 48.3%; p<.001), and to have lower BMI (27.8 vs 31.5 kg/m2; p<.001), outpatient admission status (10.8% vs 4.0%; p<.001), and fewer bleeding disorders (0.0% vs 1.2%; p<.001). The proportion of non-GA spine operations increased from nearly 0% in 2005 to 2.1% in 2019. The increase in non-GA operations was statistically significant in cervical (0.0%-1.1%) and lumbar (0.0%-2.9%) operations. For non-GA lumbar operations performed 2007-2019, 30-day complication rates, readmission rates, and mean length of stay all decreased (19.1%-5.4%, p<.05; 5.9%-2.8%, p<.05; 30.9 hours-24.9 hours, p<.05, respectively). Similarly, for non-GA cervical operations performed 2007-2019, 30-day complication rates, readmission rates, and mean length of stay all decreased (20.1%-6.1%, p<.05; 6.7%-3.7%, p<.05; 27.0-20.0 hours p<.05, respectively). CONCLUSIONS: Our trends analysis revealed increasing utilization and improved outcomes of non-GA spine surgery from 2005 to 2019; however, the proportion of non-GA spine operations remains small. Future research should investigate the barriers to adoption of non-GA spine surgery.