Introduction
There is a troubling lack of effective pain treatments after major surgery. Opioids remain dominant despite their many drawbacks, resulting in worse outcomes and higher costs. Locoregional anesthetics are increasingly employed, but their added value remains limited.
BR-003 is an implantable anesthetic designed for spine fixation surgery. It consists of a ring-shaped biodegradable hydrogel that is easily co-implanted with pedicle screws. Unlike injections, BR-003 stays in place and delivers bupivacaine to the surgical site for three days.
By reducing pain and opioid-related side-effects, BR-003 may help patients leave the hospital sooner and in better shape. Now, it is tested in humans for the first time.

Methods
Ongoing open-label Phase Ib study on BR-003 safety and pharmacokinetics. Two cohorts of 6 patients undergo posterior degenerative spine fixation in 2 hospitals. Per cohort, 3 patients undergo minimally invasive surgery (MIS) in a Dutch hospital, and 3 undergo open surgery in a Swiss hospital. Cohort 1 receives 4 pedicle screws with 4 BR-003 rings. Cohort 2 receives 6 screws with 6 rings.
The primary endpoint is bupivacaine Cmax. Secondary endpoints include pharmacokinetics, safety, and exploratory efficacy up to 6 weeks. Safety monitoring includes AEs, ECGs, X-rays, and blood tests. Efficacy is explored by comparing back pain in rest (AUC-NRS) and opioid use (MMEs) in the first 3 days to a recent observational cohort in the same hospitals. In MIS cohort 1, pre-emptive analgesia was restricted to assess the early effects of BR-003.

Results
Nine patients were included so far: full cohort 1 and 3 MIS patients in cohort 2. Bupivacaine Cmax remained 10x below the known toxic threshold. No serious adverse events were attributed to BR-003 to date. After MIS with BR-003, the average AUC-NRS in the first 3 days was 1.2 points lower (3.7 vs 4.9) despite restricted pre-emptive analgesia. After open surgery, the AUC-NRS was 1.6 points lower (1.4 vs 3.0). Total opioid use was 39% lower with BR-003 (MMEs 150 vs 247). Opioid use on day 2 and 3 was low, providing opportunities for earlier discharge.

Conclusion
This first-in-human study revealed no safety concerns to date. A substantial reduction was found in pain and opioid use compared to a recent observational cohort in the same hospitals. A large randomized controlled trial is planned to substantiate the impact of BR-003 on pain, opioid use, and enhanced recovery after spine fixation surgery.

Background
Screw loosening is a common cause for revision following spinal instrumentation using pedicle screws. The current gold standard to detect loosening of pedicle screws is radiation-emitting computed tomography imaging. However, solely based on medical imaging, clinicians are not able to reliably identify loose implants in a substantial amount of cases. Intraoperative extractional torque measurement disrupts the potentially intact bone-implant interface. To overcome these issues, we propose a new methodology for the radiation-free, non-destructive, and easy-to-integrate detection of screw loosening based on vibroacoustic sensing.

Methods
For the detection of a loose implant, we excite the vertebra of interest with a sine sweep vibration at the spinous process and use a custom highly-sensitive piezo vibration sensor attached directly at the screw head to capture the propagated vibration characteristics which are analyzed using a deep learning-based detection pipeline. To validate the proposed approach, we developed a biomechanically controlled simulation setup for pedicle screw loosening using custom 3D printed drill guides. We conducted experiments using four human cadaveric lumbar spine specimens and evaluated our algorithm in a leave-one-specimen-out cross-validation experiment.

Results
Vibroacoustic sensing reaches a sensitivity of 91.50 ± 6.58% and a specificity of 91.10 ± 2.27% for pedicle screw loosening detection.

Conclusion
The tested system could be used for the reliable intraoperative detection of loose pedicle screws as an alternative for the measurement of the extractional torque. Furthermore, we believe that the proposed work could serve as a strong proof-of-concept for the development of smart implants in spinal fusion surgery.

Introduction
Anterior lumbar interbody fusion (ALIF) surgery can damage nerve fibers and has been linked to sexual dysfunction in men. In women, sexual and urinary dysfunction following ALIF is barely investigated.

Research question
The aim of this study was to investigate the frequency of postoperative changes in sexual function and of incontinence in women following ALIF.

Material and Methods
We asked 173 female patients aged 18-60 years who had undergone a primary ALIF surgery in 2015-2022 in a large Swiss spine center to retrospectively answer a questionnaire about sexual function and incontinence pre- and postoperatively as well as their satisfaction with the surgery. We used exact McNemar test to compare paired data.

Results
Of all respondents (n = 84), 23 (27%) reported a worsening of sexual function following ALIF surgery, and these changes were persistent in 83%. Among individual symptoms of sexual dysfunction, the highest increase was observed for prevalence of vaginal dryness, which increased from 12% pre-operatively to 32% (p < 0.001), followed by dyspareunia, which increased from 8% to 21% (p = 0.001). Urinary incontinence increased from 25% to 41% (p < 0.001) and prevalence of faecal incontinence remained unchanged. Patient age, level of surgery and fusion material were not associated with worsening of sexual function. However, worsening of sexual function was associated with a lower level of satisfaction with the surgery outcome and a lower proportion of patients who would have the
surgery again.

Discussion and Conclusion
Female patients should receive preoperative information about potential changes in sexual function after ALIF.

Study Design Retrospective analysis of consecutively enrolled skeletally mature patients who underwent ALIF and/or LLIF interbody fusion for degenerative or deformity pathologies utilizing 3DPTi cages between 2020 and 2022 from a single surgeon spine registry.
Objective To determine the fusion rate in patients undergoing anterior lumbar interbody fusion (ALIF) and/or lateral lumbar interbody fusion (LLIF) with titanium cages.
Summary of Background Data Interbody composition is a key factor in the success of spinal fusion surgery. While the use of three-dimensional printed titanium (3DPTi) has been well established in other orthopaedic applications, the reports of titanium cages in anterior- or lateral-based spinal fusion are scarce.
Methods Fusion rate at 1-year follow-up was assessed by computed tomography (CT) scans and graded by Lenke-Bridwell classification. Flexion-extension lateral radiographs were assessed at 1-year postoperatively and fusion confirmed if less than 5 degrees range of motion was detected through the fused segment. Perioperative metrics including bone graft type, operative time, estimated blood loss, revisions within the first postoperative year, and clinical outcome assessed by the Oswestry Disability Index (ODI) were analyzed.
Results Seventy-three patients, with 130 fusion levels with 3DPTi cages were identified. 71.2% of patients were treated for degenerative pathologies, 24.7% for deformity pathologies and 4.1% for pseudoarthrosis. 5.5% of patients underwent a revision procedure with 3DPTi cages. Overall, 99.2% of interbody levels were fused on CT at 1-year postoperatively. On flexion-extension radiographs, all levels were deemed to be fused. Five patients (6.8%) required an additional surgery within the first two years. No revisions were required for cage subsidence/migration, or pseudoarthrosis. Median ODI significantly improved at 1-year postoperatively compared to baseline (median baseline ODI: 46; 1-year ODI: 22, p = 0.001).
Conclusion 3D-printed titanium cages for ALIF and LLIF result in excellent fusion rates at one year postoperatively without the need for rhBMP-2.

Introduction: Cervical disc arthroplasty (CDA) was established as a motion-sparing alternative to anterior cervical discectomy and fusion (ACDF) for degenerative cervical disease, achieving comparable patient-reported and clinical outcomes. Many unique CDA device designs are available, with distinct outcomes and complications identified. Despite these differences in device design and performance, there is a paucity of data on different modes of failure of CDA implants. To date, literature on complications associated with revision surgery for CDA is limited, mainly comparing CDA to fusion instead of comparing different CDA models. This study aimed to analyze revision cases due to complications related to CDA reported to the FDA Drug Administration’s Manufacturer and User Facility Device Experience (MAUDE) database.

Methods: The MAUDE database was queried for data from January 2005 to September 2023. All the reported complication entries for the nine FDA-approved CDA devices were analyzed. The full-text entries of all complications were individually analyzed, reported, and grouped depending on the revision surgery performed. For each revision case, the device used, the associated complication, the time until revision, and the type of revision surgery were collected.

Results: In summary, 1,347 entries were analyzed from the MAUDE database, with the highest number of reports made to the database in 2018 (218). A total of 678 cases reported revision surgery for nine different CDA models: Mobi-C (239), M6 (167), Prodisc-C (88), Prestige (60), PCM (44), Bryan (35), Secure (23), Simplify (21) and Discover (1). The top three complications associated with CDA revision were implant migration (23.5%), neck pain (15.5%), and heterotopic ossification (6.6%). The top complication per device was migration for Mobi-C (26.4%), Prodisc-C (21.3%), Prestige (24.6%), PCM (84.1%), Bryan (48.6%), Secure (30.4%) and Discover (100%). For M6 the most common complications associated with revision surgery were osteolysis (18.6%) and neck pain (18.6%). Neck pain (23.8%) was the most common for the Simplify device.

Conclusion:
The MAUDE database highlights complications related to revision cases for CDA, which may not receive sufficient emphasis in existing published studies and can vary depending on the device. Nevertheless, the primary complications linked to CDA revision consistently include implant migration, neck pain, and heterotopic ossification.

Introduction: Traumatic thoracolumbar burst fractures are the most common spinal injuries and the proper treatment is controversial. In central Europe in particular, these fractures are often treated with minimally invasive anterior-posterior reduction and fusion, whereas a conservative approach is preferred in the USA. Independent of the treatment strategy, no data exists regarding the outcome related to return to activity level/sport. The aim of this study was to evaluate the return to sports and activity levels after 360° fusion in patients with thoracolumbar burst fractures without neurological deficits.
Methods: Between January 2013 and December 2022, 46 patients aged 18 to 40 years underwent partial or complete vertebral body replacement in the thoracolumbar region due to traumatic burst fractures without neurologic deficit as an isolated injury. Patients were contacted retrospectively by phone calls to assess their activities using a modified version of the Tegner activity scale at different time points: Before trauma, 3, 6, and 12 months post-surgery.
Results: After applying exclusion criteria, data collection was complete for 28 patients. The median modified Tegner activity scale was 5.4 before sustaining the fracture, declined to 2.9 at three months post-trauma, improved to 4.2 at six months, and reached 5.0 at 12 months. The majority (83%) of patients achieved their pre-accident activity level within 12 months. No significant differences were observed between patients with partial or complete corpectomy.
Conclusion: This is the first study assessing return to sports/physical activity based on the modified Tegner scale in young patients undergoing 360° fusion for spinal burst fractures. The majority of patients (83%) return to the pre-injury activity level within 12 months after surgery.

Introduction:
Carbon fiber-reinforced poly-ether-ether-ketone (CFR-PEEK) vertebral body replacements (VBR) promise low subsidence, reduced image artifacts, and improved radiation planning while maintaining fusion capabilities. This study evaluates the safety and efficacy of the novel Kong® modular, titanium-coated CFR-PEEK VBR for restoring sagittal alignment via anterior column reconstruction (ACR) of the thoracolumbar spine following high-energy trauma, osteoporotic fractures, or tumors.

Methods:
We retrospectively analyzed all patients undergoing ACR with the Kong® VBR from 2020 to 2021. Exclusion criteria were incomplete records. The primary outcome was the bi-segmental kyphotic angle (BKA) correction measured by the Cobb method. Secondary outcomes included craniocaudal subsidence, the cage height coefficient for evaluating the cage expansion locking mechanism, sagittal tilt, pedicle screw loosening, and spinal fusion status assessed by Bridwell's criteria on plain radiographs and CT scans. Clinical outcomes were evaluated using Odom's criteria (all patients), the Karnofsky Performance Status (tumors), and the AOSpine PROST-Score (trauma group). Complications were documented.

Results:
The cohort comprised 28 patients (15 high-energy and 7 osteoporotic fractures, 6 tumors; age: 61 ± 19 years; 33% female; follow-up: 17.7 ± 7.7 months). Postoperative BKA correction was significant at 14.4° (± 23.8°, p = 0.01). At last follow-up, a correction loss of 2.7° (± 25.2°, p = 0.60) was observed, with correction from baseline maintained at 15.3° (± 30.3°, p = 0.03). At last follow-up, subsidence was 0.5 ± 0.71 mm (range 0-2 mm; p = 0.05), and no changes in cage height coefficient (0.02 ± 0.10, range 0.0-0.5; p = 0.11) or sagittal tilt (0.8 ± 4.4°, range 0-22°; p = 0.38) were observed. No screw loosening occurred. Fusion (Bridwell Grade I or II) was achieved in 95% (CT) and 93% (radiographs) of cases. Neurological function improved in 88% of patients with initial deficits. At last follow-up, Karnofsky Performance Status improved by 17.9 points (p = 0.01), AOSpine PROST-Score was 56.9, and 92% of patients were rated as "excellent" or "good” according to Odom’s criteria. One (4%) early deep infection occurred, treated with debridement.

Conclusion:
Preliminary data suggest that the Kong® modular, expandable, titanium-coated CFR-PEEK VBR is a viable and effective option for ACR of the thoracolumbar spine for high-energy and osteoporotic fractures, and spinal tumors.

Introduction: Adjacent segment disease (ASD) is a frequent reason for revision surgery following primary spine fusion. A harmonic sagittal spinopelvic alignment (SPA) correlates with patient reported outcome measures (PROMs) in spinal deformity correction. However, the importance of SPA in short-segment lumbosacral fusion surgery for long-term outcome and prevention of ASD is largely unknown. This study aimed to explore how SPA affects revision surgery for ASD and postoperative PROMs after short-segment lumbosacral fusion.

Methods: This is a retrospective single-centre study in a tertiary academic institution. Patients who underwent a primary L4-S1 spinal fusion between 2003 and 2015 were followed-up by phone-call after a minimum of 5 years postoperative and the following PROMs were assessed: Oswestry Disability Index (ODI) and the 5-level EQ5D (EQ5D5L). Patients who underwent revision surgery for ASD (= ASD group) were compared to patients who did not (= controls). Various SPA parameters were measured on preoperative and initial postoperative standing radiographs.

Results: Among 86 patients with a mean follow-up of 12 ± 4 years, 32.6% (n = 28) underwent ASD revision surgery within 73 ± 59 months, accounting for 85% of all revisions. Age (53 ± 17 years), sex (57% female), BMI (26.6 ± 6.0) and follow-up time did not differ between the ASD group and controls. No significant difference in pre- and postoperative sagittal alignment parameters were found. However, preoperative pelvic incidence (53.7° vs. 59.6°), sacral slope (34.9° vs. 40.3°), and lumbar pelvic angle (8.8° vs. 12.1°) trended to be lower in the ASD group than the controls, although not reaching statistical significance. Post-surgery, the L3-L4 angle decreased significantly in the ASD group (7.3°, p = 0.013), but not in controls. Patients who underwent ASD revision exhibited higher ultimate ODI scores 24 (IQR = 13-39) vs. controls 11 (IQR = 2-28; p = 0.03) and lower EQ5D5L scores 70 (IQR = 55-85) vs. controls 85 (IQR = 70-90; p = 0.04).

Conclusion: SPA was not associated with ASD revision surgery in short-segment lumbo-sacral fusions > 5-year follow-up. This suggests that other factors, beyond radiographic parameters and SPA may exert greater influence on achieving favourable long-term-outcomes and averting ASD. Patients who underwent ASD revision surgery had worse scores in postoperative PROMs, which underlines the importance of ASD prevention and risk reduction.

Background Context Academic orthopaedic journals and specialty societies emphasize the importance of two-year follow-up for patient-reported outcome measures (PROMS) after spine surgery, but there are limited data evaluating the appropriate length of follow-up.
Purpose To determine whether PROMs, as measured by the Oswestry Disability Index (ODI), would change significantly after 2-months postoperatively after lumbar decompression surgery for disc herniation or spinal stenosis.
Study design Retrospective analysis of prospectively and consecutively enrolled patients undergoing lumbar decompression surgery.
Patient sample One hundred sixty-nine patients
Outcome Measures ODI, achievement of minimum clinically important difference (MCID), revisions.
Methods Patients without a preoperative baseline score were excluded. Completion of the ODI questionnaire was assessed at the follow-up points. The median ODI was compared at time baseline, 2-month, 1-year and 2-year follow-up. Risk of reoperation was assessed with receiver operating characteristic (ROC) analysis to identify at-risk ODI thresholds of requiring reoperation.
Results Median ODI significantly improved at all time points compared to baseline (median baseline ODI: 40; 2-month ODI: 16, p=0.001; 1-year ODI: 11.1, p=0.001; 2-year ODI: 8, p=0.001). Post-hoc analysis demonstrated no difference between 2-months, 1-year and 2-year postoperative ODI (p=0.9, p=0.468, p=0.606). The MCID was met in 87.9% of patients at two months, 80.7% at one year, and 87.3% at two years postoperatively. Twelve patients (7.7%) underwent revision surgery between 2 months and 2 years after the index surgery (median time to revision: 5.6 months). ROC curve analysis demonstrated that an ODI score ≥24 points at 2-months yielded a sensitivity of 85.7% and a specificity of 71.8% for predicting revision after lumbar decompression (AUC=0.758; 95% CI: 0.613-0.903). The Youden optimal threshold value of ≥24 points at 2-month postop ODI yielded an odd’s ratio (OR) for revision of 15.3 (CI: 1.8-131.8; p = 0.004). The positive predictive value and negative predictive value were 15.4% and 98.8%, respectively.
Conclusion Two-year clinical follow-up may not be necessary for future peer-reviewed lumbar decompression surgery studies given that ODI plateaus at 8 weeks. Patients with a score ≥ 24 points at 2-months postoperatively have a higher risk of requiring a second surgery within the first two years and warrant continued follow-up.

Introduction
Computerized navigation is currently widespreading around the world in spine surgery, allowing more accurate procedures especially to insert pedicle screws, becoming a gold standard in many facilities. Robotic guidance aims to stabilize a robotic arm after surgical planning of screw trajectory. The Mazor X Stealth is a recent device which combines robotic guidance and navigation. The purpose of the study was to compare operative and radiologic results and also radiation exposure between the Mazor X Stealth and the O-arm navigation for pedicle screw insertion.

Methods
All patients who required pedicle screw insertion for posterior lumbar fusion were prospectively included and divided into two groups : RG when operated on with the Mazor X Stealth, and NV when operated on with the O-arm and navigation as a control group. Age, number of levels operated, number of screws inserted, operative time in minutes (min), estimated blood loss (EBL in milliliters, ml), time to insert screws (in min) were collected. Satisfaction of screw positioning was assessed with the Gertzbein classification. Dosimetric data of the imaging devices were recorded for effective dose E calculation (in millisievert, mSv) using conversion factors. The absolute risk of cancer (AR, in %) equivalent to a whole-body acquisition was also calculated. Intraoperative and postoperative complications were recorded.

Results
100 patients were included, 50 in each group. Mean age was similar: 72 versus 69 in RG and NV respectively, p = 0.21. 227 vertebrae were operated: 106 in RG and 121 in NV. A total of 438 screws were inserted, 205 in RG and 233 in NV. Operative time was similar with 161 versus 151 minutes in RG and NV respectively (p = 0.37), as well as EBL (350 versus 454 ml, p = 0.13). Mean time to insert screws was significantly lower in RG, with 13 minutes versus 18 minutes in NV, p = 0.03; but time per screw was similar: 3.4 versus 3.8 respectively, p = 0.11. 97% screws were satisfactory in RG versus 99% in NV. Overall E was significantly higher in RG, with 7.24 and 5.77 mSv in NV, p < 0.01, as well as AR, with 3.6x10E-4% in RG and 2.9x10E-4% in NV (p < 0.01). Overall complication rate was 26% in RG and 36% in NV.

Conclusion
The Mazor X Stealth showed promising results especially in accuracy of pedicle screw insertion, operative parameters and also complications, but was inferior to the O-arm navigation in terms of radiation exposure.

Introduction
The gold standard for the assessment of bone mineral density (BMD) is dual-energy x-ray absorptiometry (DEXA). In principle, conventional magnetic resonance imaging (MRI) and radiography could also be used for estimating BMD, with the advantage of not requiring any ionizing radiation (for MRI) and potentially allowing for opportunistic examination and retrospective analysis of existing imaging databases. This study aimed at developing machine learning methods to estimate BMD and to detect osteopenia/osteoporosis from conventional lumbar MRI (T1-weighted and T2-weighted images) and planar radiography in combination with clinical data and imaging parameters of the acquisition protocol.

Materials and methods
A database of 429 patients subjected to lumbar MRI, planar radiographs and DEXA within 6 months was created from an institutional imaging database. Several machine learning models were trained and tested (373 patients for training, 86 for testing) with the following objectives: (1) direct estimation of the vertebral BMD; (2) classification of T-score lower than -1 or (3) lower than -2.5. The models took as inputs either the images or radiomics features derived from them, alone or in combination with metadata (age, sex, body size, vertebral level, parameters of the imaging protocol).

Results
The best-performing models achieved mean absolute errors (MAEs) of 0.15-0.16 g/cm2 for the direct estimation of BMD for the cases in the test set, and of 1.0-1.07 for the estimation of the T-score.
Regarding the classification of cases of low BMD, areas under the receiver operating characteristic (ROC) curve of 0.82 (MRIs) - 0.80 (radiographs) for the classification of T-scores lower than -1, and 0.80 (MRIs) - 0.65 (radiographs) for T-scores lower than -2.5 were obtained.

Conclusions
The models showed good discriminative performances in detecting cases of low BMD, and more limited capabilities for the direct estimation of its value. Being based on routine imaging and readily available data, such models are promising tools to retrospectively analyse existing datasets as well as for the opportunistic investigation of bone disorders.

Acknowledgements
The project has been partially funded by the ISSLS Clinical Research Grant 2023.

The incidence of H-/U-type fragility fractures of the sacrum among geriatric patients is increasing, but evidence on the best surgical stabilisation method is lacking. In this retrospective bi-centric comparative cohort study, we aimed to compare the outcomes and complications of transiliac-transsacral screw fixation (TIS) and lumbopelvic fixation (LPF), the two most common fixation methods for nondisplaced H-/U- type fragility fractures among geriatric patients.

Medical records of patients treated with TIS or LPF for nondisplaced H-/U-type fragility fractures of the sacrum at two level A trauma centres between 2012 and 2022 were analysed. Postoperative pain and mobility levels were assessed as primary outcomes before discharge and at six weeks and six months postoperatively. Surgery time, blood loss, and surgical complication rates were assessed as secondary outcomes. Statistical analyses consisted of Fisher’s exact tests for frequency distributions and Mann-Whitney-U tests and t-tests for group comparisons.

52 patients undergoing TIS (mean age: 78 ± 9 years) and 41 patients undergoing LPF (75 ± 10 years) with no discrepancy in demographic parameters were identified. There were no differences in pain levels between the two groups before discharge, at six weeks postoperatively, and at six months postoperatively (p > 0.05). There were no differences in mobility levels before surgery, before discharge, at six weeks postoperatively, and at six months postoperatively (p > 0.05). Duration of surgery was shorter after TIS (53 ± 48 min) compared to LPF (116 ± 36 min) (p < 0.0001). Intraoperative blood loss was lower for TIS (median 0ml) compared to LPF (median 200ml) (p < 0.0001). Postoperative radiculopathy was less frequent after TIS (n=1) compared to LPF (n=5) (p < 0.05). Median length of stay was shorter after TIS (11 days) compared to LPF (14 days) (p < 0.05). Rates of reoperations directly related to the index surgery rates were lower after TIS (n=2) compared to LPF (n=12) (p < 0.001). Implant failures were observed only after LPF (n=2).

Geriatric patients with nondisplaced H-/U- type fragility fractures of the sacrum may preferably be treated using TIS, as it is equivalent to LPF in terms of pain reduction and restoration of mobility, but allows for shorter operative time, less blood loss and lower complication rates. Prospective randomized studies should be conducted to substantiate our findings and develop distinct treatment recommendations.

Introduction
De novo spinal infections (DNSI) are a concerning and rising healthcare problem. The treatment decision in DNSI regarding conservative or surgical therapy is established on a case-to-case basis in the absence of clear guidelines. The recently proposed Spinal Infection Treatment Evaluation (SITE) score combines clinical and radiological variables to support decision-making, but it has not been validated among non-spine surgeons. We aimed to validate this novel score in a real-life setting among surgeons from different clinical specialties.
Methods:
A single-center study was conducted at our institution from 1/10/2023 until 31/12/2023. We collected clinical and radiological data of DNSI patients, previously treated at our institution and created fifteen representative case vignettes, which included all spinal locations and SITE scores. An online survey was designed to distribute the case vignettes among physicians from the departments that agreed to participate. Participants were asked to score each case and to evaluate the applicability (0-100 points) of the SITE score. We calculated intra-class correlation coefficients (ICC3) for the score reliability and ANOVA to compare the collected applicability scores, using R for statistical analysis.
Results:
Forty-eight survey forms were analyzed, of which seven and 41 were completed by spine surgeons, or colleagues from other specialties (internal medicine (n=20), orthopedic surgery not involved in spine surgery (n=10), infectiology (n=5), and other surgical disciplines (n=6)), respectively. Spine surgeons demonstrated good interobserver reliability (ICC3 = 0.78). Non-spine surgeons showed poor interobserver reliability to the overall SITE score (ICC3 = 0.48). Subgroup analysis by specialty revealed overall low reliability scores (< 0.6 for each subgroup). Participants with more frequent exposure to DNSI cases (> 10 per year; n=9) showed higher reliability, achieving similar scores to spine surgeons (ICC3=0.7). The applicability scores showed similar values for all spine locations and SITE score severities.
Conclusions:
We found acceptably high interobserver values for the SITE score only for spine surgeons and non-spine surgeons with frequent exposure to DNSI. The reliability of the score was much lower when applied by physicians from other specialties with lesser experience of DNSI, who would particularly benefit from such a score for decision-making in clinical practice.

Intro
Since first being described by Yasargil and Caspar in 1977, the microscopic interlaminar approach remains the surgical gold standard for surgical treatment of lumbar disc herniations. The first endoscopic technique to be developed was the monoportal endoscopic technique (UESS), but it remained largely unused due to its steep learning curve. The development of biportal endoscopy (BESS/UBE) has reawakened interest in endoscopic surgery due to its shorter learning curve while retaining the advantages of UESS. The goal of this study is to evaluate the learning of UBE in a single center by a single surgeon for the treatments of mono-segmental degenerative spinal pathologies.

Met
The surgeon followed a novel step by step online UBE course during the COVID pandemic. 54 patients were followed between November 2021 and October 2023 and were separated into 3 cohorts: lumbar disc hernia (LDH), lumbar spinal stenosis (LSS) and lumbar disc hernia + lumbar spinal stenosis (LDH-S). 48 were treated with UBE. EQ-5D-5L, ODI, VAS and SF-12 scores were analysed preoperatively, 6 w, 3 m and 6 months postoperatively, using ANOVA for 36 patients. The type and rate of complications were also reported. An operation length curve was constructed using a selected homogenous cohort from the LDH group.

Res
In the LDH cohort 37 patients were treated by UBE and 5 converted to open, 7 were treated by UBE in the LSS cohort with 1 conversion and all 4 patients were treated by UBE in the LDH-S cohort. The mean OR time was 76±19 minutes in the LDH cohort, 156±30 minutes for the LSS cohort and 109±27 minutes for the LDH-S cohort. EQ-5D-5L, ODI, SF-12 significantly improved for all cohorts between the preoperative and 6-week postoperative period (p < 0.001). Noted intraoperative complications were 2 dural tears, 2 facet joint lesions (needing fusion) and a transient cauda equina syndrome. Postoperative complications were 3 early recurrences of hernia (≤ 1 month), 2 epidural hematomas, an infection and a pulmonary embolism. The operation length curve showed that OR time and complication rates decreased with the progression of cases.

Con
UBE is a safe alternative to traditional microscopic surgery with low complication rates, especially when the initial learning curve of 24 cases is overcome. It is also possible to learn the technique successfully and efficiently through online mentoring, making the technique considerably more accessible to surgeons who cannot attend in-person training.

Introduction
Accurate landmark detection is essential for precise analysis of anatomical structures, supporting diagnosis, treatment planning, and monitoring in patients with spinal deformities. Conventional methods rely on laborious landmark identification by medical experts, which motivates automation. The proposed deep learning pipeline processes bi-planar radiographs to determine spinopelvic parameters and Cobb angles without manual supervision.

Methods
The whole dataset used for training and evaluation comprised 555 bi-planar radiographs from uninstrumented patients, manually annotated by a medical professional. In a pre-processing step, the pipeline determined the regions of interest (cervical spine, thoracolumbar spine, sacrum & pelvis). A segmentation network was trained for each ROI to identify vertebral bodies and pelvic landmarks. The network used a refined UNet architecture and was trained on 455 bi-planar radiographs using a Dice loss. To improve segmentation performance, the training data was augmented with artificially generated samples. The post-processing algorithm derived spinal alignment and angular parameters based on the segmentation output. The pipeline was evaluated on a test set of 100 previously unseen bi-planar radiographs. The performance metric utilized was the mean absolute difference between annotated and predicted landmarks. Additionally, the spinopelvic parameter predictions of the pipeline were compared to the measurements of two experienced medical professionals using the intraclass correlation coefficient.

Results
The pipeline was able to successfully predict the Cobb angles in 61% of all test cases and achieved mean absolute differences of 3.3° (3.6°) and averaged ICC of 0.88. For thoracic kyphosis, lumbar lordosis, sagittal vertical axis, sacral slope, pelvic tilt, and pelvic incidence the pipeline produced reasonable outputs in 69%, 58%, 86%, 85%, 84%, 84% of the cases. The MAD was 5.6° (7.8°), 4.7° (4.3°), 2.8mm (3.0mm), 4.5° (7.2°), 1.8° (1.8°) and 5.3° (7.7°), while the ICC was measured at 0.69, 0.82, 0.99, 0.61, 0.96 and 0.70, respectively.

Conclusion
Despite limitations in patients with severe pathologies and high BMI, the pipeline automatically predicted coronal and sagittal spinopelvic parameters, which has the potential to simplify clinical routines and large-scale retrospective data analysis.

Acknowledgments
The authors thank the Promedica Stiftung, Chur, for financial support.

Introduction:
In spinal deformity surgery, full navigation with intraoperative CT often requires multiple scans for extensive corrections. We introduced a workflow combining Brainlab Airo® navigation with the freehand (FH) technique in lower levels, requiring only one scan, reducing time and radiation exposure. Here, we assess the FH screw accuracy and safety of combined navigated/FH instrumentation.

Methods:
We retrospectively analyzed all patients undergoing neuromonitored open posterior instrumentation for adult idiopathic (AIS) or neuromuscular (NM) scoliosis from 2018 to 2023. Our workflow began with FH instrumentation below the deformity's apex, verified with a CT scan. Subsequent screws were navigated based on this scan. The accuracy of all screws was confirmed with C-arm fluoroscopy. Exclusions: Altered workflows or incomplete data. The primary outcome was FH screw accuracy on CT (Gertzbein-Robbins scale). Secondary outcomes were screw adjustments, scan time, dose-length product (DLP), screw loosening, curve correction (Cobb angles), and the SRS-22 questionnaire. We noted neurological and other complications.

Results:
In 31 patients (24 AIS, 7 NM; age: 16.5±4.7 years; BMI: 20.3±4.1; follow-up: 19.8±9.9 months), 560 screws were placed in 413 levels (278 FH in 206 levels; 282 navigated in 226 levels; 19 levels both techniques). FH accuracy reached Grade A in 254 screws (91.4%), Grade B in 10 (3.6%), Grade C in 2 (0.7%), Grade D in 1 (0.4%), with 11 outer breaches (4.0%). Four FH screws (1.4%) and one navigated screw (0.4%) were replaced. All screws were correct on final X-rays. Significant corrections were attained in the main (49.8±11.4°, p < 0.0001) and secondary curves (30.6±12.1°, p < 0.0001). Significant changes were found in clavicular height, pelvic and T1 tilt, while thoracic kyphosis, lumbar lordosis, C7 plumb line, and coronal balance did not change. Mean DLP was 91.1±30.4 mGy·cm and mean scan duration 18,479±4,037 ms. No screw loosening, neurological or screw-related complications occurred. Mean SRS-22 was 4.3±0.9 out of 5 across all items.

Conclusion:
In our approach, FH accuracy on CT matched the rates of up to 96% reported in purely navigated pedicle screws for pediatric deformity, without screw complications. Adding FH screws enabled accurate full-length navigation with a single scan. Despite lacking a control group, the data suggests that complementing navigation with FH screws is a viable option in pediatric deformity corrections.

Introduction:
Clinical studies have repeatedly highlighted the benefits of endoscopic transpedicular decompression for down-migrated lumbar disc herniations. However, the biomechanical effects on pedicle stability have not been studied up to now. The goal of this study was to analyze the effects of an endoscopic transpedicular approach with different drill diameters (6 and 8 mm) to compare them with the intact native side. In addition, the influence of bone quality on the resistance of the pedicle after transpedicular approach was investigated.

Methods:
Twenty-four vertebras originating from four fresh-frozen cadavers were tested under uniaxial compression load in a ramp-to-failure test: (1) the tunneled pedicle on one side, and (2) the native pedicle on the other side. Of the 24 lumbar vertebrae, 12 were assigned to a drill diameter of 6 mm and the other 12 to a diameter of 8 mm.

Results:
The median ratio of sustained force for the operated side compared to the intact contralateral side is equal to 74% (63 – 88) for both drill diameters combined. A transpedicular approach with 8 mm resulted in a decrease of the axial resistance force by 60 – 88% compared to the intact contralateral side (p = 0.002). A 6 mm drill hole resulted in a decrease of the axial resistance force by 66 – 84% compared to the intact opposite side (p = 0.01). No significant difference between the two different drill diameters was recorded (p=1). For all 3 subgroups (intact, 8 mm drilled, 6 mm drilled) the HU values and the absolute resistance force showed significant correlations (intact: ρ=0.859; p < 0.001 ; 8 mm drilled: ρ=0.902; p < 0.001; 6 mm drilled: ρ=0.835; p < 0.001).

Conclusion:
Transpedicular approach significantly reduces the axial resistance force of the pedicle, which may lead to pedicle fracture. Bone quality correlated positively with the absolute resistance force of the pedicle, whereas the influence of the drill hole diameter plays only a limited role.

Purpose To analyze the effect of endplate weakness prior to PLIF or TLIF cage implantation and compare it to the other intact endplate of the same vertebral body. In addition, the influence of bone quality on endplate resistance was investigated.
Methods Twenty-two lumbar vertebrae were tested in a ramp-to-failure test. One endplate of each vertebral body was tested intact and the other after weakening with a shaver (over an area of 200mm2). Either a TLIF or PLIF cage was then placed and the compression load was applied across the cage until failure of the endplate. Failure was defined as the first local maximum of the force measurement. Bone quality was assessed by determining the Hounsfield units (HU) on CT images.
Results With an intact endplate and a TLIF cage, the median force to failure was 1276.3N (693.1-1980.6N). Endplate weakening reduced axial endplate resistance to failure by 15% (0-23%). With an intact endplate and a PLIF cage, the median force to failure was 1057.2N (701.2-1735.5N). Endplate weakening reduced axial endplate resistance to failure by 36.6% (7-47.9%). Bone quality correlated linearly with the force at which endplate failure occurred. Both intact and weakened endplates showed a strong positive correlation with bone quality of  = 0.939 (p = 9.3E-11) and  = 0.840 (p = 1E-06), respectively.
Conclusion Weakening of the endplate during cage bed preparation significantly reduces the axial resistance of the endplate to failure: endplate load capacity is reduced by 15% with TLIF and 37% with PLIF. Bone quality correlates with the force at which endplate failure occurs.

Introduction
The addition of fusion to decompression surgery for lumbar degenerative spondylolisthesis and spinal canal stenosis remains disputable. Hence, the aim of this study was to assess the comparative effectiveness and selected healthcare resource utilization of patients undergoing decompression with or without fusion surgery at 3 years follow-up.

Methods
Using observational data from the multicenter prospective Lumbar Stenosis Outcome Study (LSOS) and a target trial emulation with index trial benchmarking approach, we assessed the comparative effectiveness of the two main surgical interventions for lumbar degenerative spondylolisthesis and spinal canal stenosis - fusion and decompression surgery alone. The outcome parameters were the change in EuroQol Health Related Quality of Life 5-Dimension 3-Level questionnaire, in back/leg pain intensity (Numeric Rating Scale), in satisfaction (Spinal Stenosis Measure satisfaction subscale) and healthcare resource utilization outcomes as physical therapy and oral analgesic use.

Results
153 patients underwent decompression alone and 62 had decompression plus fusion. After inverse probability weighting, 137 patients were included in the decompression alone group (mean age, 73.9 [7.5] years; 77 female [56%]) and 36 in the decompression plus fusion group (mean age, 70.1 [6.7] years; 18 female [50%]). We found no statistically significant standardized mean differences in EuroQol Health Related Quality of Life summary index change score at 3 years (EQ-5D-3L: 0.07 [95% confidence interval (CI), -0.25 to 0.39]). No between-group differences in change in back/leg pain intensity or satisfaction were found. Decompression plus fusion was associated with greater physical therapy utilization at 3 years follow-up.

Conclusions
Decompression alone should be considered the primary option for patients with lumbar degenerative spondylolisthesis and spinal stenosis.