Patient outcomes following implementation of an enhanced recovery after surgery pathway for patients with metastatic spine tumors.

BACKGROUND: Metastatic spine tumor surgery consists of palliative operations performed on frail patients with multiple medical comorbidities. Enhanced recovery after surgery (ERAS) programs involve an evidence-based, multidisciplinary approach to improve perioperative outcomes. This study presents clinical outcomes of a metastatic spine tumor ERAS pathway implemented at a tertiary cancer center. METHODS: The metastatic spine tumor ERAS program launched in April 2019, and data from January 2018 to May 2020 were reviewed. Measured outcomes included the following: hospital length of stay (LOS), time to ambulation, urinary catheter duration, time to resumption of diet, intraoperative fluid intake, estimated blood loss (EBL), and intraoperative and postoperative day 0-5 cumulative opioid use (morphine milligram equivalent [MME]). RESULTS: A total of 390 patients were included in the final analysis: 177 consecutive patients undergoing metastatic spine tumor surgery enrolled in the ERAS program and 213 consecutive pre-ERAS patients. Although the mean case durations were similar in the ERAS and pre-ERAS cohorts (265 vs. 274 min; p = .22), the ERAS cohort had decreased EBL (157 vs. 215 ml; p = .003), decreased postoperative day 0-5 cumulative mean opioid use (178 vs. 396 MME; p < .0001), earlier ambulation (mean, 34 vs. 57 h; p = .0001), earlier discontinuation of urinary catheters (mean, 36 vs. 56 h; p < .001), and shorter LOS (5.4 vs. 7.5 days; p < .0001). CONCLUSIONS: The implementation of a multidisciplinary ERAS program designed for metastatic spine tumor surgery led to improved clinical quality metrics, including shorter hospitalizations and significant reductions in opioid consumption.

Factors associated with adjacent-level tumor progression in patients receiving surgery followed by radiosurgery for metastatic epidural spinal cord compression.

OBJECTIVE: Separation surgery followed by spine stereotactic radiosurgery (SSRS) has been shown to achieve favorable rates of local tumor control and patient-reported outcomes in patients with metastatic epidural spinal cord compression (MESCC). However, rates and factors associated with adjacent-level tumor progression (ALTP) in this population have not yet been characterized. The present study aimed to identify factors associated with ALTP and examine its association with overall survival (OS) in patients receiving surgery followed by radiosurgery for MESCC. METHODS: Thirty-nine patients who underwent separation surgery followed by SSRS for MESCC were identified using a prospectively collected database and were retrospectively reviewed. Radiological measurements were collected from preoperative, postoperative, and post-SSRS MRI. Statistical analysis was conducted using the Kaplan-Meier product-limit method and Cox proportional hazards test. Subgroup analysis was conducted for patients who experienced ALTP into the epidural space (ALTP-E). RESULTS: The authors' cohort included 39 patients with a median OS of 14.7 months (range 2.07-96.3 months). ALTP was observed in 16 patients (41.0%) at a mean of 6.1 ± 5.4 months postradiosurgery, of whom 4 patients (10.3%) experienced ALTP-E. Patients with ALTP had shorter OS (13.0 vs 17.1 months, p = 0.047) compared with those without ALTP. Factors associated with an increased likelihood of ALTP included the amount of bone marrow infiltrated by tumor at the index level, amount of residual epidural disease following separation surgery, and prior receipt of radiotherapy at the index level (p < 0.05). Subgroup analysis revealed that primary tumor type, amount of preoperative epidural disease, time elapsed between surgery and radiosurgery, and prior receipt of radiotherapy at the index level were significantly associated with ALTP-E (p < 0.05). CONCLUSIONS: To the authors' knowledge, this study is the first to identify possible risk factors for ALTP, and they suggest that it may be associated with shorter OS in patients receiving surgery followed by radiosurgery for MESCC. Future studies with higher power should be conducted to further characterize factors associated with ALTP in this population.

Development and implementation of a comprehensive spine surgery enhanced recovery after surgery protocol: the Cleveland Clinic experience.

Enhanced recovery after surgery (ERAS) protocols have been shown to be effective at reducing perioperative morbidity and costs while improving outcomes. To date, spine surgery protocols have been limited in scope, focusing only on specific types of procedures or specific parts of the surgical episode. The authors describe the creation and implementation of one of the first comprehensive ERAS protocols for spine surgery. The protocol is unique in that it has a comprehensive perioperative paradigm encompassing the entire surgical period that is tailored based on the complexity of each individual spine patient.

MIS technique for separation surgery in lumbar spine metastatic disease.

Around 40% of cancer patients present with spinal metastases (SM), the lumbar spine being the second most involved site (15%-30%) after the thoracic (60%-80%). Since the development of separation surgery, minimally invasive surgery (MIS) has increasingly been applied to approach SM, mirroring benefits yielded in the degenerative realm. Moreover, preoperative embolization potentially enhances local control for certain radioresistant histologies. Carbon fiber-reinforced PEEK hardware reduces image artifact, facilitating more accurate follow-up and radiotherapeutic planning. Additionally, short-segment cement-augmented constructs may be beneficial to decrease surgical morbidity and operative risk in this population. The authors present a lumbar spinal metastasis treated with MIS techniques. The video can be found here: https://stream.cadmore.media/r10.3171/2024.1.FOCVID23222.

Thoracic root-related intradural extramedullary cavernoma presenting with subarachnoid hemorrhage: illustrative case.

BACKGROUND: Just 5% of all cavernomas are located in the spine. Thoracic root-related subtypes are the rarest, with a total of 14 cases reported in the literature to date. Among them, only 4 presented with subarachnoid hemorrhage (SAH). OBSERVATIONS: A 65-year-old female presented after an ictus of headache with no neurological deficits. Computed tomography (CT) demonstrated sulcal SAH, with the remainder of the workup nondiagnostic for etiology. Three weeks later, she re-presented with acute thoracic back pain and thoracic myelopathy. CT and magnetic resonance imaging suggested dubiously a T9-10 disc herniation with spinal cord compression. Surgical decompression and resection were then planned. Intraoperative ultrasound (IUS) demonstrated an intradural extramedullary lesion, confirmed to be cavernoma. Complete resection was achieved, and the patient was discharged a few days postoperatively to inpatient rehabilitation. LESSONS: Although spine imaging is deemed to be low yield in the evaluation of cryptogenic SAH, algorithms can be revisited even in the absence of spine-related symptoms. Surgeons can be prepared to change the initial surgical plan, especially when preoperative imaging is unclear. IUS is a powerful tool to assess the thecal sac after its exposure and to help guide this decision, as in this rare entity.

Machine Learning in Spine Oncology: A Narrative Review.

STUDY DESIGN: Narrative Review. OBJECTIVE: Machine learning (ML) is one of the latest advancements in artificial intelligence used in medicine and surgery with the potential to significantly impact the way physicians diagnose, prognose, and treat spine tumors. In the realm of spine oncology, ML is utilized to analyze and interpret medical imaging and classify tumors with incredible accuracy. The authors present a narrative review that specifically addresses the use of machine learning in spine oncology. METHODS: This study was conducted in accordance with the Preferred Reporting Items of Systematic Reviews and Meta-Analysis (PRISMA) methodology. A systematic review of the literature in the PubMed, EMBASE, Web of Science, Scopus, and Cochrane Library databases since inception was performed to present all clinical studies with the search terms '[[Machine Learning] OR [Artificial Intelligence]] AND [[Spine Oncology] OR [Spine Cancer]]'. Data included studies that were extracted and included algorithms, training and test size, outcomes reported. Studies were separated based on the type of tumor investigated using the machine learning algorithms into primary, metastatic, both, and intradural. A minimum of 2 independent reviewers conducted the study appraisal, data abstraction, and quality assessments of the studies. RESULTS: Forty-five studies met inclusion criteria out of 480 references screened from the initial search results. Studies were grouped by metastatic, primary, and intradural tumors. The majority of ML studies relevant to spine oncology focused on utilizing a mixture of clinical and imaging features to risk stratify mortality and frailty. Overall, these studies showed that ML is a helpful tool in tumor detection, differentiation, segmentation, predicting survival, predicting readmission rates of patients with either primary, metastatic, or intradural spine tumors. CONCLUSION: Specialized neural networks and deep learning algorithms have shown to be highly effective at predicting malignant probability and aid in diagnosis. ML algorithms can predict the risk of tumor recurrence or progression based on imaging and clinical features. Additionally, ML can optimize treatment planning, such as predicting radiotherapy dose distribution to the tumor and surrounding normal tissue or in surgical resection planning. It has the potential to significantly enhance the accuracy and efficiency of health care delivery, leading to improved patient outcomes.

Disease Control and Toxicity Outcomes after Stereotactic Ablative Radiation Therapy for Recurrent and/or Metastatic Cancers in Young-Adult and Pediatric Patients.

BACKGROUND: Pediatric patients with metastatic and/or recurrent solid tumors have poor survival outcomes despite standard-of-care systemic therapy. Stereotactic ablative radiation therapy (SABR) may improve tumor control. We report the outcomes with the use of SABR in our pediatric solid tumor population. METHODS: This was a single-institutional study in patients < 30 years treated with SABR. The primary endpoint was local control (LC), while the secondary endpoints were progression-free survival (PFS), overall survival (OS), and toxicity. The survival analysis was performed using Kaplan-Meier estimates in R v4.2.3. RESULTS: In total, 48 patients receiving 135 SABR courses were included. The median age was 15.6 years (interquartile range, IQR 14-23 y) and the median follow-up was 18.1 months (IQR: 7.7-29.1). The median SABR dose was 30 Gy (IQR 25-35 Gy). The most common primary histologies were Ewing sarcoma (25%), rhabdomyosarcoma (17%), osteosarcoma (13%), and central nervous system (CNS) gliomas (13%). Furthermore, 57% of patients had oligometastatic disease (≤5 lesions) at the time of SABR. The one-year LC, PFS, and OS rates were 94%, 22%, and 70%, respectively. No grade 4 or higher toxicities were observed, while the rates of any grade 1, 2, and 3 toxicities were 11.8%, 3.7%, and 4.4%, respectively. Patients with oligometastatic disease, lung, or brain metastases and those who underwent surgery for a metastatic site had a significantly longer PFS. LC at 1-year was significantly higher for patients with a sarcoma histology (95.7% vs. 86.5%, p = 0.01) and for those who received a biological equivalent dose (BED10) > 48 Gy (100% vs. 91.2%, p = 0.001). CONCLUSIONS: SABR is well tolerated in pediatric patients with 1-year local failure and OS rates of <10% and 70%, respectively. Future studies evaluating SABR in combination with systemic therapy are needed to address progression outside of the irradiated field.

Resection of intradural intramedullary subependymoma of the cervicothoracic spine: 2-dimensional operative video.

This video presents the case of a 44-year-old male with a 2-year history of pain in the left upper extremity that had worsened over the course of the last 6 months with associated weakened grip strength and had extended into his right arm. T2-weighted sagittal and axial MRI demonstrated an expansive nonenhancing solid intramedullary lesion extending from C5 to T1. The patient underwent a C5-T1 laminectomy and laminoplasty with near-complete resection of the intradural intramedullary subependymoma. At 3 months' follow-up, he reported doing well and had experienced significant improvement in motor strength with ongoing therapies.

Cervicothoracic junction instrumentation strategies following separation surgery for spinal metastases.

OBJECTIVE: The cervicothoracic junction (CTJ) is a challenging region to stabilize after tumor resection for metastatic spine disease. The objective of this study was to describe the outcomes of patients who underwent posterolateral decompression and instrumented fusion (i.e., separation surgery across the CTJ for instability due to metastatic disease). METHODS: The authors performed a single-institution retrospective study of a prospectively collected cohort of patients who underwent single-approach posterior decompression and instrumented fusion across the CTJ for metastatic spine disease between 2011 and 2018. Adult patients (≥ 18 years old) who presented with mechanical instability, myelopathy, and radiculopathy secondary to metastatic epidural spinal cord compression (MESCC) of the CTJ (C7-T1) from 2011 to 2018 were included. RESULTS: Seventy-nine patients were included, with a mean age of 62.1 years. The most common primary malignancies were non-small cell lung (n = 17), renal cell (11), and prostate (8) carcinoma. The median number of levels decompressed and construct length were 3 and 7, respectively. The average operative time, blood loss, and length of stay were 179.2 minutes, 600.5 ml, and 7.7 days, respectively. Overall, 58 patients received adjuvant radiation, and median dose, fractions, and time from surgery were 27 Gy, 3 fractions, and 20 days, respectively. All patients underwent lateral mass and pedicle screw instrumentation. Forty-nine patients had tapered rods (4.0/5.5 mm or 3.5/5.5 mm), 29 had fixed-diameter rods (3.5 mm or 4.0 mm), and 1 had both. Ten patients required anterior reconstruction with poly-methyl-methacrylate. The overall complication rate was 18.8% (6 patients with wound-related complications, 7 with hardware-related complications, 1 with both, and 1 with other). For the 8 patients (10%) with hardware failure, 7 had tapered rods, all 8 had cervical screw pullout, and 1 patient also experienced rod/screw fracture. The average time to hardware failure was 146.8 days. The 2-year cumulative incidence rate of hardware failure was 11.1% (95% CI 3.7%-18.5%). There were 55 deceased patients, and the median (95% CI) overall survival period was 7.97 (5.79-12.60) months. For survivors, the median (range) follow-up was 12.94 (1.94-71.80) months. CONCLUSIONS: Instrumented fusion across the CTJ demonstrated an 18.8% rate of postoperative complications and an 11% overall 2-year rate of hardware failure in patients who underwent metastatic epidural tumor decompression and stabilization.

Long-Term Clinical Outcomes of Patients with Colorectal Cancer with Metastatic Epidural Spinal Cord Compression Treated with Hybrid Therapy (Surgery Followed by Stereotactic Body Radiation Therapy).

BACKGROUND: Hybrid therapy, consisting of separation surgery followed by stereotactic body radiation therapy, has become the mainstay treatment for radioresistant spinal metastases. Histology-specific outcomes for hybrid therapy are scarce. In clinical practice, colorectal cancer (CRC) is particularly thought to have poor outcomes regarding spinal metastases. The goal of this study was to evaluate clinical outcomes for patients treated with hybrid therapy for spinal metastases from CRC. METHODS: This retrospective study was performed at a tertiary cancer center. Adult patients with CRC spinal metastasis who were treated with hybrid therapy for high-grade epidural spinal cord or nerve root compression from 2005 to 2020 were included. Outcome variables evaluated included patient demographics, overall survival and progression-free survival, surgical and radiation complications, and clinical-genomic correlations. RESULTS: Inclusion criteria were met by 50 patients. Progression of disease occurred in 7 (14%) patients at the index level, requiring reoperation and/or reirradiation at a mean of 400 days after surgery. Postoperative complications occurred in 16% of patients, with 3 (6%) requiring intervention. APC exon 14 and 16 mutations were found in 15 of 17 patients tested and in all 3 of 7 local failures tested. Twenty patients (40%) underwent further radiation due to disease progression at other spinal levels. CONCLUSIONS: Hybrid therapy in patients with CRC resulted in 86.7% local control at 2 years after surgery, with limited complications. APC mutations are commonly present in CRC patients with spine metastases and may suggest worse prognosis. Patients with CRC spinal metastases commonly progress outside the index treatment level.

Real-time ultrasound guidance in the endoscopic endonasal resection of a retro-odontoid pannus: Technical note and case illustration.

Background and Objectives: Odontoidectomy is a surgical procedure indicated in the setting of various pathologies, with the main goal of decompressing the ventral brain stem and spinal cord as a result of irreducible compression at the craniovertebral junction. The endoscopic endonasal approach has been increasingly used as an alternative to the transoral approach as it provides a straightforward, panoramic, and direct approach to the odontoid process. In addition, intraoperative ultrasound (US) guidance is a technique that can optimize safety and surgical outcomes in this context. It is used as an adjunct to neuronavigation and provides intraoperative confirmation of decompression of craniovertebral junction structures in real time. The authors aim to present the use and safe application of real-time intraoperative US guidance during endonasal endoscopic resection of a retro-odontoid pannus. Methods: A retrospective chart review of a single case was performed and presented herein as a case report and narrated operative video. Results: A minimally invasive US transducer was used intraoperatively to guide the resection of a retro-odontoid pannus and confirm spinal cord decompression in real time. Postoperative examination of the patient revealed immediate neurological improvement. Conclusions: Intraoperative ultrasonography is a well described and useful modality in neurosurgery. However, the use of intraoperative US guidance during endonasal endoscopic approaches to the craniovertebral junction has not been previously described. As demonstrated in this technical note, the authors show that this imaging modality can be added to the ever-evolving armamentarium of neurosurgeons to safely guide the decompression of neural structures within the craniocervical junction with good surgical outcomes.

The Impact of Targetable Mutations on Clinical Outcomes of Metastatic Epidural Spinal Cord Compression in Patients With Non-Small-Cell Lung Cancer Treated With Hybrid Therapy (Surgery Followed by Stereotactic Body Radiation Therapy).

BACKGROUND: In treatment of metastatic epidural spinal cord compression (MESCC), hybrid therapy, consisting of separation surgery, followed by stereotactic body radiation therapy, has become the mainstay of treatment for radioresistant pathologies, such as non-small-cell lung cancer (NSCLC). OBJECTIVE: To evaluate clinical outcomes of MESCC secondary to NSCLC treated with hybrid therapy and to identify clinical and molecular prognostic predictors. METHODS: This is a single-center, retrospective study. Adult patients (≥18 years old) with pathologically confirmed NSCLC and spinal metastasis who were treated with hybrid therapy for high-grade MESCC or nerve root compression from 2012 to 2019 are included. Outcome variables evaluated included overall survival (OS) and progression-free survival, local tumor control in the competing risks setting, surgical and radiation complications, and clinical-genomic correlations. RESULTS: One hundred and three patients met inclusion criteria. The median OS for this cohort was 6.5 months, with progression of disease noted in 5 (5%) patients at the index tumor level requiring reoperation and/or reirradiation at a mean of 802 days after postoperative stereotactic body radiation therapy. The 2-year local control rate was 94.6% (95% CI: 89.8-99.3). Epidermal growth factor receptor (EGFR) treatment-naïve patients who initiated EGFR-targeted therapy after hybrid therapy had significantly longer OS (hazard ratio 0.47, 95% CI 0.23-0.95, P = .04) even after adjusting for smoking status. The presence of EGFR exon 21 mutation was predictive of improved progression-free survival. CONCLUSION: Hybrid therapy in NSCLC resulted in 95% local control at 2 years after surgery. EGFR treatment-naïve patients initiating therapy after hybrid therapy had significantly improved survival advantage. EGFR-targeted therapy initiated before hybrid therapy did not confer survival benefit.

Novel Intrafraction Motion Tracking During Postoperative Spine Stereotactic Irradiation for a Patient With Carbon Fiber Fixation Hardware.

Carbon-fiber reinforced (CFR) polyetheretherketone hardware is an alternative to traditional metal hardware used for spinal fixation surgeries before postoperative radiation therapy for patients with spinal metastases. CFR hardware's radiolucency decreases metal artifact, improving visualization and accuracy of treatment planning. We present the first clinical use and proof of principle of CFR spinal hardware with tantalum markers used for successful tracking of intrafraction motion (IM) using Varian TrueBeam IMR (Intrafraction Motion Review) software module during postoperative spine stereotactic radiation. A 63-year-old woman with history of endometrial cancer presented with acute back pain. Imaging demonstrated pathologic T12 vertebral fracture with cord compression. She underwent T12 vertebrectomy with circumferential decompression and posterior instrumented T10-L2 fusion at our facility using CFR-polyetheretherketone hardware with tantalum screw markers followed by postoperative stereotactic body radiation therapy to 3000 cGy in 5 fractions delivered to T11-T12. Tantalum screw markers were used for IMR tracking. During irradiation, 260 kV images were acquired, and IMR software was able to identify and track markers. During the entire treatment, the IM motions were less than 3 mm. This is the first presented case of CFR spinal hardware with tantalum markers used for successful IMR tracking of IM during daily spine stereotactic treatment. Future work will be needed to improve workflow and create a spine-specific IMR protocol.

The role of neoadjuvant denosumab in the treatment of aneurysmal bone cysts: a case series and review of the literature.

OBJECTIVE: Aneurysmal bone cysts (ABCs) are benign cystic lesions most commonly occurring in the long bones of pediatric patients. Spinal ABCs may be difficult to resect given their invasive, locally destructive nature, proximity to critical structures such as the spinal cord, and their intrinsic hypervascularity, for which complete embolization is often constrained by radiculomedullary segmental feeders. Denosumab, a monoclonal antibody that binds the receptor activator of nuclear factor kappa B (NF-κB) ligand, has been utilized in the treatment of ABCs most often as a rescue therapy for recurrent disease. Here, the authors present 3 cases of neoadjuvant denosumab use in surgically unresectable tumors to calcify and devascularize the lesions, allowing for safer, more complete resection. METHODS: This is a single-center, retrospective case series treated at a tertiary care cancer center. The authors present 3 cases of spinal ABC treated with neoadjuvant denosumab. RESULTS: All 3 patients experienced calcification, size reduction, and a significant decrease in the vascularity of their ABCs on denosumab therapy. None of the patients developed new neurological deficits while on denosumab. Subsequently, all underwent resection. One patient continued denosumab during the immediate postoperative period because a subtotal resection had been performed, with stabilization of the residual disease. No complications were associated with denosumab administration. CONCLUSIONS: The use of denosumab in unresectable ABCs can cause calcification and devascularization, making safe resection more likely.

Late-week surgery and discharge to specialty care associated with higher costs and longer lengths of stay after elective lumbar laminectomy.

OBJECTIVE: In a healthcare landscape in which costs increasingly matter, the authors sought to distinguish among the clinical and nonclinical drivers of patient length of stay (LOS) in the hospital following elective lumbar laminectomy-a common spinal surgery that may be reimbursed using bundled payments-and to understand their relationships with patient outcomes and costs. METHODS: Patients ≥ 18 years of age undergoing laminectomy surgery for degenerative lumbar spinal stenosis within the Cleveland Clinic health system between March 1, 2016, and February 1, 2019, were included in this analysis. Generalized linear modeling was used to assess the relationships between the day of surgery, patient discharge disposition, and hospital LOS, while adjusting for underlying patient health risks and other nonclinical factors, including the hospital surgery site and health insurance. RESULTS: A total of 1359 eligible patients were included in the authors' analysis. The mean LOS ranged between 2.01 and 2.47 days for Monday and Friday cases, respectively. The LOS was also notably longer for patients who were ultimately discharged to a skilled nursing facility (SNF) or rehabilitation center. A prolonged LOS occurring later in the week was not associated with greater underlying health risks, yet it nevertheless resulted in greater costs of care: the average total surgical costs for lumbar laminectomy were 20% greater for Friday cases than for Monday cases, and 24% greater for late-week cases than for early-week cases ultimately transferred to SNFs or rehabilitation centers. A Poisson generalized linear model fit the data best and showed that the comorbidity burden, surgery at a tertiary care center versus a community hospital, and the incidence of any postoperative complication were associated with significantly longer hospital stays. Discharge to home healthcare, SNFs, or rehabilitation centers, and late-week surgery were significant nonclinical predictors of LOS prolongation, even after adjusting for underlying patient health risks and insurance, with LOSs that were, for instance, 1.55 and 1.61 times longer for patients undergoing their procedure on Thursday and Friday compared to Monday, respectively. CONCLUSIONS: Late-week surgeries are associated with a prolonged LOS, particularly when discharge is to an SNF or rehabilitation center. These findings point to opportunities to lower costs and improve outcomes associated with elective surgical care. Interventions to optimize surgical scheduling and perioperative care coordination could help reduce prolonged LOSs, lower costs, and, ultimately, give service line management personnel greater flexibility over how to use existing resources as they remain ahead of healthcare reforms.

Neuro-Oncology Practice resources for optimizing care and practice in spinal oncology.

As the diagnosis and treatment of systemic cancers continues to improve, increased patient survival has resulted in a rise in the number of patients who develop spinal metastases (SM). Within many areas of oncology, utilization of multidisciplinary care models in the management and decision making of SM patients has proven effective for optimizing care and improving patient safety. Three main goals of an effective clinical pathway include improving outcomes and quality, improving the patient experience, and lowering cost. This paper outlines the strategies employed to optimally establish such a collaborative program for the management of patients with SM, as well as direct providers in and out of the field, patients and caregivers, and practice managers to the appropriate resources.

Development of a novel in vitro cadaveric model for analysis of biomechanics and surgical treatment of Bertolotti syndrome.

BACKGROUND CONTEXT: Bertolotti syndrome (BS) is caused by pseudoarticulation between an aberrant L5 transverse process and the sacral ala, termed a lumbosacral transitional vertebra (LSTV). BS is thought to cause low back pain and is treated with resection or fusion, both of which have shown success. Acquiring cadavers with BS is challenging. Thus, we combined 3D printing, based on BS patient CT scans, with normal cadaveric spines to create a BS model. We then performed biomechanical testing to determine altered kinematics from LSTV with surgical interventions. Force sensing within the pseudojoint modeled nociception for different trajectories of motion and surgical conditions. PURPOSE: This study examines alterations in spinal biomechanics with LSTVs and with various surgical treatments for BS in order to learn more about pain and degeneration in this condition, in order to help optimize surgical decision-making. In addition, this study evaluates BS histology in order to better understand the pathology and to help define pain generators-if, indeed, they actually exist. STUDY DESIGN/SETTING: Model Development: A retrospective patient review of 25 patients was performed to determine the imaging criteria that defines the classical BS patient. Surgical tissue was extracted from four BS patients for 3D-printing material selection. Biomechanical Analysis. This was a prospective cadaveric biomechanical study of seven spines evaluating spinal motions, and loads, over various surgical conditions (intact, LSTV, and LSTV with various fusions). Additionally, forces at the LSTV joint were measured for the LSTV and LSTV with fusion condition. Histological Analysis: Histologic analysis was performed prospectively on the four surgical specimens from patients undergoing pseudoarthrectomy for BS at our institution to learn more about potential pain generators. PATIENT SAMPLE: The cadaveric portion of the study involved seven cadaveric spines. Four patients were prospectively recruited to have their surgical specimens assessed histologically and biomechanically for this study. Patients under the age of 18 were excluded. OUTCOME MEASURES: Physiological measures recorded in this study were broken down into histologic analysis, tissue biomechanical analysis, and joint biomechanical analysis. Histologic analysis included pathologist interpretation of Hematoxylin and Eosin staining, as well as S-100 staining. Tissue biomechanical analysis included stiffness measurements. Joint biomechanical analysis included range of motion, resultant torques, relative axis angles, and LSTV joint forces. METHODS: This study received funding from the American Academy of Neurology Medical Student Research Scholarship. Three authors hold intellectual property rights in the simVITRO robotic testing system. No other authors had relevant conflicts of interest for this study. CT images were segmented for a representative BS patient and cadaver spines. Customized cutting and drilling guides for LSTV attachment were created for individual cadavers. 3D-printed bone and cartilage structural properties were based on surgical specimen stiffness, and specimens underwent histologic analysis via Hematoxylin and Eosin, as well as S-100 staining. Joint biomechanical testing was performed on the robotic testing system for seven specimens. Force sensors detected forces in the LSTV joint. Kruskal-Wallis tests and Dunnett's tests were used for statistical analysis with significance bounded to p<.05. RESULTS: LSTV significantly reduces motion at the L5-S1 level, particularly in lateral bending and axial rotation. Meanwhile, the LSTV increases adjacent segment motion significantly at the L2-L3 level, whereas other levels have nonsignificant trends toward increased motion with LSTV alone. Fusion involving L4-S1 (L4-L5 and L5-S1) to treat adjacent level degeneration associated with an LSTV is associated with a significant increase in adjacent segment motion at all levels other than L5-S1 compared to LSTV alone. Fusion of L5-S1 alone with LSTV significantly increases L3-L4 adjacent segment motion compared to LSTV alone. Last, ipsilateral lateral bending with or without ipsilateral axial rotation produces the greatest force on the LSTV, and these forces are significantly reduced with L5-S1 fusion. CONCLUSIONS: BS significantly decreases L5-S1 mobility, and increases some adjacent segment motion, potentially causing patient activity restriction and discomfort. Ipsilateral lateral bending with or without ipsilateral axial rotation may cause the greatest discomfort overall in these patients, and fusion of the L5-S1 or L4-S1 levels may reduce pain associated with these motions. However, due to increased adjacent segment motion with fusions compared to LSTV alone, resection of the joint may be the better treatment option if the superior levels are not unstable preoperatively. CLINICAL SIGNIFICANCE: This study's results indicate that patients with BS have significantly altered spinal biomechanics and may develop pain due to increased loading forces at the LSTV joint with ipsilateral lateral bending and axial rotation. In addition, increased motion at superior levels when an LSTV is present may lead to degeneration over time. Based upon results of LSTV joint force testing, these patients' pain may be effectively treated surgically with LSTV resection or fusion involving the LSTV level if conservative management fails. Further studies are being pursued to evaluate the relationship between in vivo motion of BS patients, spinal and LSTV positioning, and pain generation to gain a better understanding of the exact source of pain in these patients. The methodologies utilized in this study can be extrapolated to recreate other spinal conditions that are poorly understood, and for which few native cadaveric specimens exist.