A mouse model for the study of transplanted bone marrow mesenchymal stem cell survival and proliferation in lumbar spinal fusion.

PURPOSE: Bone marrow aspirate has been successfully used alongside a variety of grafting materials to clinically augment spinal fusion. However, little is known about the fate of these transplanted cells. Herein, we develop a novel murine model for the in vivo monitoring of implanted bone marrow cells (BMCs) following spinal fusion. METHODS: A clinical-grade scaffold was implanted into immune-intact mice undergoing spinal fusion with or without freshly isolated BMCs from either transgenic mice which constitutively express the firefly luciferase gene or syngeneic controls. The in vivo survival, distribution and proliferation of these luciferase-expressing cells was monitored via bioluminescence imaging over a period of 8 weeks and confirmed via immunohistochemistry. MicroCT imaging was performed 8 weeks to assess fusion. RESULTS: Bioluminescence imaging indicated transplanted cell survival and proliferation over the first 2 weeks, followed by a decrease in cell numbers, with transplanted cell survival still evident at the end of the study. New bone formation and increased fusion mass volume were observed in mice implanted with cell-seeded scaffolds. CONCLUSIONS: By enabling the tracking of transplanted bone marrow-derived cells during spinal fusion in vivo, this mouse model will be integral to developing a deeper understanding of the biological processes underlying spinal fusion in future studies. These slides can be retrieved under Electronic Supplementary Material.

Bone graft options for spinal fusion following resection of spinal column tumors: systematic review and meta-analysis.

OBJECTIVE With the advent of new adjunctive therapy, the overall survival of patients harboring spinal column tumors has improved. However, there is limited knowledge regarding the optimal bone graft options following resection of spinal column tumors, due to their relative rarity and because fusion outcomes in this cohort are affected by various factors, such as radiation therapy (RT) and chemotherapy. Furthermore, bone graft options are often limited following tumor resection because the use of local bone grafts and bone morphogenetic proteins (BMPs) are usually avoided in light of microscopic infiltration of tumors into local bone and potential carcinogenicity of BMP. The objective of this study was to review and meta-analyze the relevant clinical literature to provide further clinical insight regarding bone graft options. METHODS A web-based MEDLINE search was conducted in accordance with preferred reporting items for systematic review and meta-analysis (PRISMA) guidelines, which yielded 27 articles with 383 patients. Information on baseline characteristics, tumor histology, adjunctive treatments, reconstruction methods, bone graft options, fusion rates, and time to fusion were collected. Pooled fusion rates (PFRs) and I2 values were calculated in meta-analysis. Meta-regression analyses were also performed if each variable appeared to affect fusion outcomes. Furthermore, data on 272 individual patients were available, which were additionally reviewed and statistically analyzed. RESULTS Overall, fusion rates varied widely from 36.0% to 100.0% due to both inter- and intrastudy heterogeneity, with a PFR of 85.7% (I2 = 36.4). The studies in which cages were filled with morselized iliac crest autogenic bone graft (ICABG) and/or other bone graft options were used for anterior fusion showed a significantly higher PFR of 92.8, compared with the other studies (83.3%, p = 0.04). In per-patient analysis, anterior plus posterior fusion resulted in a higher fusion rate than anterior fusion only (98.8% vs 86.4%, p < 0.001). Although unmodifiable, RT (90.3% vs 98.6%, p = 0.03) and lumbosacral tumors (74.6% vs 97.9%, p < 0.001) were associated with lower fusion rates in univariate analysis. The mean time to fusion was 5.4 ± 1.4 months (range 3-9 months), whereas 16 of 272 patients died before the confirmation of solid fusion with a mean survival of 3.1 ± 2.1 months (range 0.5-6 months). The average time to fusion of patients who received RT and chemotherapy were significantly longer than those who did not receive these adjunctive treatments (RT: 6.1 months vs 4.3 months, p < 0.001; chemotherapy: 6.0 months vs 4.3 months, p = 0.02). CONCLUSIONS Due to inter- and intrastudy heterogeneity in patient, disease, fusion criteria, and treatment characteristics, the optimal surgical techniques and factors predictive of fusion remain unclear. Clearly, future prospective, randomized studies will be necessary to better understand the issues surrounding bone graft selection following resection of spinal column tumors.

Low Back Pain and Spondylosis.

Low back pain is highly prevalent, affecting a vast majority of the adult population at some point in their lifetime. Thorough history and physical examination is critically important in evaluating these patients and screening for potentially serious conditions. Imaging should be guided by the history and physical examination, particularly when there is concern for serious conditions and/or a focal neurological deficit present. Adequate treatment of patients with low back pain often requires a multidisciplinary approach, involving several medical specialties. Patients with acute axial low back pain typically have a favorable prognosis with resolution over 4 weeks, regardless of treatment. However, patients with chronic low back pain should be transitioned to pain management strategies with multidisciplinary care, in order to maximize function and limit disability. Referral to a spine surgeon is indicated urgently for a severe, progressive neurological deficit, particularly new motor weakness or cauda equina syndrome, and can be done electively for patients with degenerative disorders without a focal deficit.

A systematic review of the use of expandable cages in the cervical spine.

Expandable vertebral body replacement cages (VBRs) have been widely used for reconstruction of the thoracolumbar spine following corpectomy. However, their use in the cervical spine is less common, and currently, no expandable cages on the market are cleared or approved by the US Food and Drug Administration for use in the cervical spine. The objective of this study was to perform a systematic review on the use of expandable cages in the treatment of cervical spine pathology with a focus on fusion rates, deformity correction, complications, and indications. A comprehensive Medline search was performed, and 24 applicable articles were identified and included in this review. The advantages of expandable cages include greater ease of implantation with less risk of damage to the end plate, less intraoperative manipulation of the device, and potentially greater control over lordosis. They may be particularly advantageous in cases with poor bone quality, such as patients with osteoporosis or metastatic tumors that have been radiated. However, there is a potential risk of overdistraction, which is increased in the cervical spine, their minimum height limits their use in cases with collapsed vertebra, and the amount of hardware in the expansion mechanism may limit the surface area available for fusion. The use of expandable VBRs are a valuable tool in the armamentarium for reconstruction of the anterior column of the cervical spine with an acceptable safety profile. Although expandable cervical cages are clearly beneficial in certain clinical situations, widespread use following all corpectomies is not justified due to their significantly greater cost compared to structural bone grafts or non-expandable VBRs, which can be utilized to achieve similar clinical outcomes.

Total en bloc spondylectomy for locally aggressive and primary malignant tumors of the lumbar spine.

PURPOSE: To report outcomes after total en bloc spondylectomy (TES) for primary aggressive/malignant tumors of the lumbar spine. METHODS: We performed a retrospective review of 23 neurosurgical patients operated between 2004 and 2014. Outcomes included perioperative complication rates and reoperation rates for instrumentation failure. The relationship between patient/operative parameters and complication development/instrumentation failure was investigated. RESULTS: There were 15 men (65.2 %) and eight women (24.8 %), with a median of 47 years. The most common tumor was chordoma in 11 patients (47.8 %), followed by sarcoma in four (17.4 %), and giant cell tumor in three (13.0 %). All patients but one underwent a two-staged operation; median total estimated blood loss was 3200 mL and median total operative time was 18.5 h. Fifteen patients developed at least one perioperative complication (65.2 %), with the most common being wound infection and ileus (26.1 % each). There was one case of intraoperative iliac vein injury (4.4 %). Instrumentation failure occurred in 9 patients (39.1 %) at a median time of 23 months after index spondylectomy. Following logistic regression, there were no factors associated with complication development. On the other hand, postoperative radiation was significantly associated with instrumentation failure (OR 7.49; 95 % CI, 1.02-54.9). Local recurrence and 5-year survival was 8.7 and 84.4 %, respectively. Median follow-up time was 50 months. CONCLUSIONS: Although favorable oncological outcomes after en bloc resection of spinal tumors may be achieved in terms of recurrence and survival, TES in the lumbar spine remains a challenging procedure. Future investigation into complication avoidance and reconstruction techniques is encouraged.

Factors associated with improved survival following surgery for renal cell carcinoma spinal metastases.

OBJECTIVE Renal cell carcinoma (RCC) frequently metastasizes to the spine, causing pain or neurological dysfunction, and is often resistant to standard therapies. Spinal surgery is frequently required, but may result in high morbidity rates. The authors sought to identify prognostic factors and determine clinical outcomes in patients undergoing surgery for RCC spinal metastases. METHODS The authors searched the records of patients who had undergone spinal surgery for metastatic disease at a single institution during a 12-year period and retrieved data for 30 patients with metastatic RCC. The records were retrospectively reviewed for data on preoperative conditions, treatment, and survival. Statistical analyses (i.e., Kaplan-Meier survival analysis and log-rank test in univariate analysis) were performed with R version 2.15.2. RESULTS The 30 patients (23 men and 7 women with a mean age of 57.6 years [range 29-79 years]) had in total 40 spinal surgeries for metastatic RCC. The indications for surgery included pain (70%) and weakness (30%). Fourteen patients (47%) had a Spinal Instability Neoplastic Score (SINS) indicating indeterminate or impending instability, and 6 patients (20%) had a SINS denoting instability. The median length of postoperative survival estimated with Kaplan-Meier analysis was 11.4 months. Younger age (p = 0.001) and disease control at the primary site (p = 0.005), were both significantly associated with improved survival. In contrast, visceral (p = 0.002) and osseous (p = 0.009) metastases, nonambulatory status (p = 0.001), and major comorbidities (p = 0.015) were all significantly associated with decreased survival. Postoperative Frankel grades were the same or had improved in 78% of patients. Major complications occurred in 9 patients, and there were 3 deaths (10%) during the 30-day in-hospital period. Three en bloc resections were performed. CONCLUSIONS Resection and fixation may provide pain relief and neurological stabilization in patients with spinal metastases arising from RCC, but surgical morbidity rates remain high. Younger patients with solitary spinal metastases, good neurological function, and limited major comorbidities may have longer survival and may benefit from aggressive intervention.

Clinical, surgical, and molecular prognostic factors for survival after spinal sarcoma resection.

OBJECTIVE The goal of this study was to investigate the local recurrence rate and long-term survival after resection of spinal sarcomas. METHODS A retrospective review of patients who underwent resection of primary or metastatic spinal sarcomas between 1997 and 2015 was performed. Tumors were classified according to the Enneking classification, and resection was categorized as Enneking appropriate (EA) if the specimen margins matched the Enneking recommendation, and as Enneking inappropriate (EI) if they did not match the recommendation. The primary outcome measure for all tumors was overall survival; local recurrence was also an outcome measure for primary sarcomas. The association between clinical, surgical, and molecular (tumor biomarker) factors and outcomes was also investigated. RESULTS A total of 60 patients with spinal sarcoma were included in this study (28 men and 32 women; median age 38 years). There were 52 primary (86.7%) and 8 metastatic sarcomas (13.3%). Thirty-nine tumors (65.0%) were classified as high-grade, and resection was considered EA in 61.7% of all cases (n = 37). The local recurrence rate was 10 of 52 (19.2%) for primary sarcomas; 36.8% for EI resection and 9.1% for EA resection (p = 0.010). Twenty-eight patients (46.7%) died during the follow-up period, and median survival was 26 months. Overall median survival was longer for patients with EA resection (undefined) compared with EI resection (13 months, p < 0.001). After multivariate analysis, EA resection significantly decreased the hazard of local recurrence (HR 0.24, 95% CI 0.06-0.93; p = 0.039). Age 40 years or older (HR 4.23, 95% CI 1.73-10.31; p = 0.002), previous radiation (HR 3.44, 95% CI 1.37-8.63; p = 0.008), and high-grade sarcomas (HR 3.17, 95% CI 1.09-9.23; p = 0.034) were associated with a significantly increased hazard of death, whereas EA resection was associated with a significantly decreased hazard of death (HR 0.22, 95% CI 0.09-0.52; p = 0.001). CONCLUSIONS The findings in the present study suggest that EA resection may be the strongest independent prognostic factor for improved survival in patients with spinal sarcoma. Additionally, patients who underwent EA resection had lower local recurrence rates. Patients 40 years or older, those with a history of previous radiation, and those with high-grade tumors had an increased hazard of mortality in this study.

Analgesic therapy for major spine surgery.

Pain following spine surgery is often difficult to control and can persist. Reduction of this pain requires a multidisciplinary approach that depends on contributions of both surgeons and anesthesiologists. The spine surgeon's role involves limiting manipulation of structures contributing to pain sensation in the spine, which requires an in-depth understanding of the specific anatomic etiologies of pain originating along the spinal axis. Anesthesiologists, on the other hand, must focus on preemptive, multimodal analgesic treatment regimens. In this review, we first discuss anatomic sources of pain within the spine, before delving into a specific literature-supported pain management protocol intended for use with spinal surgery.

Five-level cervical corpectomy for neurofibromatosis-associated spinal deformity: case report.

PURPOSE: To describe a successful five-level cervical corpectomy and circumferential reconstruction in a patient with a plexiform neurofibroma causing a severe kyphotic deformity. METHODS: Case report. RESULTS: 43-year-old man with history of Neurofibromatosis presented with signs and symptoms of myelopathy with spastic lower extremities and gait difficulties. Imaging studies demonstrated a severe kyphotic deformity of the cervical spine with associated cord compression secondary to an anteriorly positioned plexiform neurofibroma. Two-stage surgical procedure was designed to treat this lesion. Stage I consisted of tracheostomy placement, transmandibular, circumglossal approach to the anterior cervical spine, C2-C6 corpectomies, and C1-C7 reconstruction with a custom titanium cage/plate. Stage II consisted of suboccipital craniectomy, C1-C2 laminectomies, and occipital-cervical thoracic instrumented fusion (O-T8). There were no operative complications, but the patient did develop a small pulmonary embolism post-operatively treated with anticoagulation. Patient required two-weeks of inpatient rehabilitation following surgery. Gastrostomy tube and tracheostomy were successfully discontinued with preserved swallowing and respiratory function. Patient-reported outcome measurements revealed significant and sustained improvement post-operatively. CONCLUSIONS: Five-level cervical corpectomy including C2 can be safely and successfully performed via a transmandibular, circumglossal approach. Circumferential reconstruction utilizing a custom anterior titanium cage and plate system manufactured from a pre-operative CT scan was utilized in this case. Long segment occipital-cervical-thoracic reconstruction is recommended in such a case. Using such a technique, improvement in myelopathy, correction of deformity, and improved quality of life can be achieved.

Intercostal aneurysm causing spinal cord compression in an NF1 patient.

PURPOSE: The authors illustrate a case where an intercostal aneurysm was observed in a patient with type 1 neurofibromatosis. METHODS: A 32-year-old man with NF1 presented with thoracic back pain. The patient's symptoms progressed to include myelopathic symptoms, including difficulty urinating, numbness in the lower extremities, and increased weakness. Imaging revealed what appeared to be a neurofibroma at the T4-T5 level and a plan to resect the mass was formulated. Upon initial limited hemilaminotomy, significant arterial blood was encountered. The patient was then taken to the interventional suite and angiography was performed, revealing a left T4 intercostal aneurysm. The aneurysm was coil-embolized with no residual filling. RESULTS: By 6 months post-surgery, the patient had regained full strength and sensation in his lower extremities and no longer had difficulty urinating. There has been no recurrence of symptoms 3 years postoperatively. CONCLUSIONS: Intercostal artery lesions must be considered as a possible diagnosis in NF1.

Tokuhashi score is predictive of survival in a cohort of patients undergoing surgery for renal cell carcinoma spinal metastases.

PURPOSE: Renal cell carcinoma (RCC) is an aggressive disease that metastasizes to the spine often requiring surgery. However, selecting the appropriate surgical intervention can be challenging. The Tokuhashi scoring system can be used to predict survival and inform the surgical strategy. We set out to determine the Tokuhashi score for patients with RCC spine metastases and compare expected and observed survival. METHODS: Records were reviewed for all patients who underwent surgery for spinal metastases at a single institution from January 2000 to December 2011 to determine the Tokuhashi score and survival. Kaplan-Meier estimates and log-rank test for univariate analysis were performed with R version 2.15.12 (R Foundation, 2012). RESULTS: Thirty patients underwent 40 spinal operations for metastatic RCC. Median survival was 11.4 months. Preoperative Tokuhashi scores were: 12-15, 15 patients; 9-11, seven patients; 0-8, eight patients. Median survival was 32.9, 11.7, and 5.4 months, respectively. Bone (p=0.01) and visceral metastases (p=0.005), and KPS (p=0.002) significantly affected survival. Tokuhashi score predicted survival (p=0.016); survival differed between the high and low score groups (p=0.006). CONCLUSIONS: RCC is an aggressive disease with short life expectancy when metastatic to the spine. However, patients with low systemic disease burden and solitary spinal metastases can have long survival and benefit from excisional surgery. Tokuhashi score can be useful in selecting surgical intervention in patients with RCC spinal metastases, and may be more relevant than in other cancers with spinal metastases.

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.

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.

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

OBJECTIVE: There is limited consensus regarding management of spinal epidural abscesses (SEAs), 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 5 predictive models in an independent cohort of patients with SEA. METHODS: One hundred seventy-six 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 receiver operating characteristic curve 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, methicillin-resistant Staphylococcus aureus 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). CONCLUSIONS: Only 1 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.

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.

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.

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.