Session 2: Spine

15. November
09:00 - 10:30
Lokale: Lokale 102-105
Chair: Søren O Nissen and Rikke Rousing

11. Cost-Effectiveness of Instrumented Versus Uninstrumented Fusion for Degenerative Spondylolisthesis
Andreas Kiilerich Andresen1,2, Mikkel Østerheden Andersen1,2, Leah Carreon1,2, Jan Sørensen3,4
1. Center for Spine Surgery and Research, Lillebaelt Hospital, Middelfart, Denmark; 2. Institute of Regional Health Research, University of Southern Denmark, Winsløwparken 19, 3, DK-5000, Odense C, Denmark. ; 3.RCSI Healthcare Outcome Research Centre, RCSI University of Medicine and Health Sciences, St. Stephen’s Green, Dublin, Ireland ; 4.Danish Centre for Health Economics, University of Southern Denmark, Winsløwparken, Odense, Denmark

Background: For patients with persistent symptoms due to degenerative spondylolisthesis surgical intervention may be recommended, typically decompression and fusion, either instrumented or uninstrumented. Instrumentation in the form of screw fixation, is considered standard of care outside of Scandinavia, however, fusion surgery in elderly patients is challenging due to osteoporotic bone stock, higher risk of complications and implant failure. With an aging population, cost-effectiveness studies are increasingly more important to guide surgeons and politicians decisions.
Aim: The aim of this study is to investigate whether instrumented posterolateral fusion is cost-effective compared to uninstrumented posterolateral fusion in elderly patients who undergo fusion surgery for one-level degenerative spondylolisthesis with spinal stenosis.
Materials and Methods: This cost-effectiveness analysis is based on a single-center, open label, randomized controlled trial, where patients with symptomatic degenerative spondylolisthesis were randomly assigned 1:1 to either instrumented posterolateral fusion or uninstrumented posterolateral fusion. Quality-Adjusted Life Years were obtained from EuroQoL-5D-3L. Use of health services were obtained from patient charts and accumulated until 2 years after index surgery.
Results: Of the 108 patients included in the study, 107 patients received the allocated intervention. There were no differences in preoperative demographics. Although the base price for instrumented posterolateral fusion was significantly higher than for uninstrumented posterolateral fusion, average cost of surgery was only €146 higher. The instrumented group has significantly less reoperations (2% vs 13%, p=0.03) outpatient visits (12 vs 38, p=0.015), MRIs performed (12.9% vs 35.0%, p=0.019). The base case incremental cost-effectiveness ratio was estimated at €1,536 per QALY.
Interpretation / Conclusion: Although the initial cost for implants are higher in the instrumented group, the cost is offset by increased use of health resources and reoperations in the uninstrumented group after surgery. The base case analysis suggested that the ICER for instrumented posterolateral fusion was well below usual levels of thresholds for cost effectiveness.

12. Outcomes and Complications after Two-Level Anterior Cervical Discectomy and Fusion (ACDF) with or without Anterior Plating: A Propensity Matched Cohort study.
Jenny Kornberg1, Kristian Høy1, Mikkel Østerheden Andersen2, Leah Carreon2
1. Department of Orthopaedics, Aarhus University Hospital 2. Center for Spine Surgery and Research, Lillebaelt Hospital

Background: Anterior cervical discectomy and fusion (ACDF) is the current standard of treatment for disc herniation and radiculopathy resistant to non- operative care. ACDF can be performed with or without plating, but the use of plate versus stand-alone cage is still a matter of debate.
Aim: The aim was to compare self-reported outcomes, subsidence, and revision rate in patients with two-level ACDF surgery with and without plate.
Materials and Methods: Prospective data from 96 patients with MRI verified cervical foraminal stenosis or disc herniation, eligible for two-level ACDF surgery, were identified and collected from The Danish National Spine Registry, DaneSpine. Demographics, patient reported outcomes, previous spine surgery and reoperations were all patient-reported using questionnaires pre- and minimum 1-year postoperative. The patients were divided into two groups, plated or not. To minimize baseline differences, propensity-score matching was applied based on age, gender, body mass index, smoking status, pre-op neck and arm pain, EQ-5D and NDI. One-year postoperative x-rays were examined to determine the amount of subsidence.
Results: A total of 86 (89,6%) patients undergoing two- level ACDF surgery had completed pre-op, surgical and one-year follow-up data. Thus, two matched cohorts consisting of 37 patients could be created. Interestingly plated patients reported significantly lower neck-pain (24.1 vs. 40.1 p=0.018) and higher EQ-5D (0.76 vs 0.62 p=0.038) scores one year after surgery compared to those without. At follow-up, there were no difference in subsidence (8 vs 9, p=1.000) or revision rates (1 vs 2, p=0.389) between the two groups.
Interpretation / Conclusion: Anterior plating in patients undergoing two-level ACDF leads to less neck pain compared to no plate but does not reduce cage subsidence or reoperation rate.

13. Rate of unexpected malignancy in patients with vertebral compression fracture undergoing percutaneous vertebroplasty – six years after implementation of a new magnetic resonance imaging scanning protocol
Line Adsbøll Wickstrøm1,2, Mikkel Østerheden Andersen1,2, Søren Rafael Rafaelsen3, Andreas Andresen1,2, Signe Elmose1,2, Leah Carreon1,2
1. Centre for Spine Surgery and Research, Region of Southern Denmark, Middelfart 2. Department of Clinical Research and Institute of Regional Health Research, University of Southern Denmark, Odense 3. Department of Radiology, Clinical Cancer Centre, University Hospital of Southern Denmark, Hospital Lillebaelt, Vejle

Background: Discrimination between benign and malign vertebral compression fracture (VCF) can be difficult. However, early diagnosis of malignant VCF is crucial to further treatment and prognosis. An earlier study at an orthopeadic department reported a rate of unsuspected malignancy of 4.9% in patients with VCF who underwent percutaneous vertebroplasty (PVP) when biopsies were obtained during the procedure. MRI scanning protocol was changed in this period.
Aim: To investigate if the rate of unsuspected malignancy in biopsies in patients with VCF who underwent PVP at the same othopeadic department has changed after implementation of a new MRI scanning protocol.
Materials and Methods: Retrospective on 427 patients with vertebral compression fracture undergoing PVP from 28th of April 2017 to 28th of April 2022, identifying operated patients from the Danish national DaneSpine registry. Subsequently, individual clinical information was collected in journal records.
Results: The rate of unsuspected malignancy was 0.9% (4/427) and the overestimation of malignant VCF was 50% (16/32).
Interpretation / Conclusion: During the last 5 years, the rate of unsuspected malignancy in patients with VCF undergoing PVP has improved considerably from 4.9% to 0.9%. Furthermore, MRI is over-diagnosing malignancies. Thus, the new scanning procedure is effective in differentiating between benign and malign VCFs.

14. The magnetic field strength and the force distance dependency of the magnetically controlled growing rods used for early-onset scoliosis.
Lars Diekhöner1, Charlotte Sommer Meyer2, 3, Kresten Wendell Rickers 2,3, Søren Peter Eiskjær 2, 3
1. Aalborg University, Physics Group, Department of Materials and Production, Skjernvej 22, 9220 Aalborg Ø; 2. Department of Orthopedic Surgery, Aalborg University Hospital, Hobrovej 18- 22m 9000 Aalborg C; 3. Department of Clinical Medicine, Faculty of Medicine, Søndre Skovvej 15, 9000 Aalborg C.

Background: Untreated early-onset scoliosis (EOS) leads to respiratory insufficiency and reduced life expectancy. Magnetically controlled growing rods (MCGR’s) have revolutionized the treatment of EOS. It is now possible to do painless lengthening in the outpatient clinic without anesthesia. However, MCGR’s have inherent complications like non-functioning of the lengthening mechanism.
Aim: We aimed to specify one correct indication for MCGR use by measuring the lengthening forces at varying distances between the external remote controller (ECR) and the MCGR to quantify the role of implantation depth.
Materials and Methods: The magnetic field strength was measured on new and explanted rods, at different distances between the external remote controller and the MCGR and likewise in patients before and after distractions in the outpatient clinic. All rods were from the MAGEC system (Nuvasive Inc., US). Two new and 12 explanted MCGRs was used for the lab measurements of the elicited force using a forcemeter. At the outpatient clinic we measured on four patients, each with two implanted rods.
Results: At a distance of 25 mm, the force was reduced to approximately 40% (ca. 100 N) compared to zero distance (ca. 250 N), most so for explanted rods. The magnetic field strength of the internal actuator decayed fast with increasing distances and plateaued at 25–30 mm approximating zero.
Interpretation / Conclusion: Based on our findings, it is of outmost importance minimizing the implantation depth to ensure proper functionality of the rod lengthening. Therefore, we recommend a distance of 25 mm from skin to MCGR to be considered a relative contraindication to clinical use in EOS patients.

15. Patient-reported outcome after adult spinal deformity surgery – Are there differences between primary and revision surgery?
Amalie Schramm1, Lærke Ragborg1, Martin Heegaard1, Lars Valentin Hansen1, Benny Dahl1, Martin Gehrchen1, Søren Ohrt-Nissen1
1. Spine Unit, Department of Orthopedic Surgery, Rigshospitalet, Copenhagen, Denmark

Background: Surgical treatment of adult spinal deformity (ASD) can significantly impact health-related quality of life (HRQoL) but is associated with a high revision rate. Whether the same patient-reported outcome (PRO) can be expected after revision surgery compared to primary surgery is uncertain.
Aim: The aim of this study was to compare PRO between revision and primary ASD surgery. We hypothesized that revision surgery would result in poorer HRQoL and treatment satisfaction.
Materials and Methods: We conducted a retrospective study on ASD patients undergoing primary and revision surgery on = 5 levels. We included patients at a single centre = 18 years old having either primary or revision surgery from 2010 to 2020, who had completed = 2 years postoperative HRQoL-questionnaires. Patients were divided into two groups: 1) primary surgery or 2) revision surgery. HRQoL and treatment satisfaction were assessed with SRS-22r and EQ-5D-3L and compared between groups.
Results: One hundred and seventy-four patients completed the postoperative questionnaires (89 primary surgery and 85 revision surgery). Mean age was 60±16 years in the revision group and 52±20 in the primary group. 71% in the revision group and 56% in the primary group were female. Median [interquartile range] SRS-22r subscore was 3.1 [2.4-3.8] and 3.3 [2.4-4.0] in the revision and primary group, respectively (p=0.150). The satisfaction score was 4.0 [3.0-4.5] vs. 4.0 [3.5-4.5] (p=0.206) and the EQ-5D-3L index score was 0.374 [0.304-0.537] vs. 0.416 [0.304-0.641], (p=0.136). The function/activity score was 2.8 [2.2-3.4] in the revision group vs 3.2 [2.4-4.0] in the primary group (p=0.027).
Interpretation / Conclusion: We found no difference in overall patient-reported HRQoL and treatment satisfaction between revision and primary surgery. Although revision surgery is associated with a higher morbidity and risk of complications, patients can expect the same PRO compared to their primary surgery.

16. Spinal Decompression and Posterolateral Fusion Improves Walking Capacity and Balance and Reduces Residual Urine in Patients with Spinal Stenosis
Andreas Kiilerich Andresen1,2, Leah Carreon1,2, Mikkel Andersen1,,2,
1. Center for Spine Surgery and Research, Lillebaelt Hospital, Middelfart, Denmark ; 2. Institute of Regional Health Research, University of Southern Denmark, Winsløwparken 19, 3, DK-5000, Odense C, Denmark.

Background: Patients with lumbar spinal stenosis complain of leg pain, impaired walking capacity and loss of balance. This decrease in function and balance leads to considerable disability and difficulty with normal function in society. In addition, spinal stenosis has been suggested to cause urinary retention, but this has not been extensively studied.
Aim: The purpose of the study is to investigate whether decreased walking capacity, balance and residual urine volume will improve after decompression and fusion surgery.
Materials and Methods: Patients scheduled for decompression and fusion due to spinal stenosis with grade 1 degenerative spondylolisthesis were enrolled. Walking distance was measured and timed (maximum of 1000m). Tandem test was performed, at 10 second intervals patients were asking to stand side-by-side, in semi-tandem and in tandem position. Patient scores range from 0-30. A post voiding ultrasonic bladder scan was performed by a registered nurse. Patients were grouped based on post void bladder volume above or below 100ml.
Results: 101 patients were included in the study, mean age was 70.7 years, 77% were female, of these 90% had symptoms for more than 6 months prior to surgery. Preoperatively, patients had a mean walking distance of 123.9meters (86.5;161.2), which increased to 791.1m (722.6;859.7) at one-year follow up (p<0.001). The correlating walking speed was 0.91m/s (0.86;0.97) preoperatively, with an increase to 1.17m/s (1.12;1.22) at 1 year follow up (p=0.02). The tandem test had a mean preoperative score of 19.6 (17.7;21.24), an increase to 26.0 (24.7;27.4) was seen at 3 months follow up, and was sustained after 2 years 12 (11.9%) of patients had more than 100ml residual urine at preoperative, this was down to 2 patients at 3 months follow up, and at 24 months follow up zero patients had significant urine retention.
Interpretation / Conclusion: Patients who had decompression and fusion due to spinal stenosis with grade 1 spondylolisthesis had severe neurological impairment regarding walking capacity, balance, and urine retention which, regardless of chronicity, was significantly improved after decompression surgery.

17. Revision surgery in Adult Spinal Deformity (ASD): A 2-year comparison between Lumbar Pedicle Subtraction Osteotomy (PSO) and supplemental Posterior Lumbar Interbody Fusion (PLIF)
Lærke Ragborg1, Niklas Tøndevold1, Ture Karbo1, Casper Dragsted1, Robert Svardal-Stelmer1, Lars Valentin Hansen1, Benny Dahl1, Martin Gehrchen1
Spine Unit, Dept. Of Orthopedic Surgery, Rigshospitalet, Copenhagen, Denmark

Background: High revision rates remain a concern when treating patients with ASD. PSO is the golden standard when treating rigid deformities; however, it can be associated with high postoperative complications, including mechanical failure. The PLIF technique is thought to facilitate the restoration of the lordosis and subsequently sagittal alignment and improve intercorporal bony fusion.
Aim: The main purpose of this study was to compare revision rates and sagittal correction in patients with ASD treated with either PSO or PLIF without PSO.
Materials and Methods: In 2016, PLIF was introduced at our institution as an alternative method to creating lordosis, as opposed to only having been using PSO during the previous years. We, therefore, analyzed two cohorts of patients with ASD undergoing either: PSO in 2010- 2015 or PLIF in 2016-2020, retrospectively. None of the patients received both treatments during the period. ASD was defined as posterior fusion of =5 levels including sacrum. The rate of mechanical failure was obtained and analyzed using competing risk analysis. Full-spine radiographs were analyzed and compared between cohorts.
Results: We included 119 patients (89 PSO and 30 PLIF) with a mean age of 64.1±10 years. Baseline demographics and radiographic parameters were comparable between cohorts except for SVA; 115±28 mm vs 87±46 mm (p-value<0.05) and segmental lordosis; 5.0±17° vs 14±3° (p- value<0.05) for PSO and PLIF, respectively. Competing risk analysis showed a cumulative incidence of revision surgery of 38.2% (95% CI 28.1-48.3) vs 16.7 (95% CI 3.3-30.0) (p-value <0.05) for PSO and PLIF at 2-year follow-up. We found an increased odds ratio for revision surgery when treated with PSO of 2.77 (95% CI 1.10-6.69) (p-value <0.05) after adjusting for preoperative SVA and segmental lordosis. A comparable sagittal alignment was obtained for both groups postoperatively.
Interpretation / Conclusion: A substantially lower revision rate was seen for patients undergoing PLIF compared with PSO at a 2-year follow-up. Moreover, an increased odds ratio for revision was found for PSO patients. A satisfactory sagittal correction was obtained for both groups regardless of the procedure. Thus PLIF should be considered when technically possible.

18. The effect of night-time bracing on the sagittal profile in adolescent idiopathic scoliosis
Martin Heegaard1, Niklas Tøndevold1, Benny Dahl1, Thomas B Andersen, 1, Martin Gehrchen1, Søren Ohrt-nissen1
1. Spine Unit, Department of Orthopedic Surgery, Rigshospitalet, Copenhagen University Hospital, Inge Lehmanns Vej 6, 2100 Copenhagen, Denmark

Background: Adolescent idiopathic scoliosis (AIS) characterized by a coronal scoliosis and often a sagittal hypokyphosis. The effect of bracing on the sagittal profile is not well understood.
Aim: The aim of this study is to assess the effect of night- time bracing on the sagittal profile in patients with AIS.
Materials and Methods: We retrospectively included AIS patients with a main curve of 25-45° treated with a night-time brace in our institution between 2005 and 2018. Patients with an estimated growth potential irrespective of Risser stage and menarchal status were included. Coronal and sagittal radiographic parameters were recorded at brace initiation and post bracing using the classification described by Abelin-Genevois for sagittal parameters and Lenke for the coronal deformity. Patients were followed until surgery or one year after brace termination.
Results: One hundred forty-six patients were included. Maximum thoracic kyphosis (TK) increased by a mean of 2.5° (±9.7) (p=0.003). Twenty-seven percent (n=36) of the patients were hypokyphotic (T4/T12 <20°) at brace initiation compared with 19% (n=26) at brace termination (p=0.134). All other sagittal parameters remained the same at follow-up. We found no association between progression in the coronal plan and change in sagittal parameters.
Interpretation / Conclusion: This is the first study to indicate that night-time bracing of AIS does not induce hypokyphosis. We found a small increase in TK during bracing but 20% still remained hypokyphotic. The coronal curve progression was not coupled to change in TK.

19. Usability and performance expectancy determines the use of a clinical decision support system in spine surgery
Søren Eiskjær1, Casper Friis Pedersen2, Simon Toftgaard Skov3, Mikkel Østerheden Andersen2
1. Dept. of Orthopedic Surgery, Aalborg University Hospital; 2. Lillebaelt Hospital, Middelfart, Denmark; 3. Elective Surgery Center, Silkeborg Regional Hospital

Background: We are of the opinion that predictive modeling of the outcome of spinal surgery using AI or ML can support the right treatment decision for the patient with a spinal disorder. For that purpose, we have constructed a clinical decision support system (CDSS) named PROPOSE. Based on patient reported outcome measures (PROM) a real time prediction is made for the outcome after surgery – quality of life (EQ-5D, ODI) back and leg pain, walking distance, return to work and risk of complications. However, a CDSS will only be used in the clinical setting if the clinicians can accept using the CDSS.
Aim: The aim of the current study was to develop a model for the factors that drive or impede the use of an AI clinical decision support system (CDSS) PROPOSE supporting the shared decision making on the choice of treatment of ordinary spinal disorders.
Materials and Methods: Sixty-two spine surgeons were asked to answer a questionnaire regarding behavioral intention to use the CDSS after being presented for PROPOSE. The model behind the questionnaire was the unified theory of acceptance and use of technology (UTAUT). Data were analyzed using PLS-SEM.
Results: Results: The most important and significant factors were the degree of ease of use associated with the new technology – effort expectancy/usability followed by performance expectancy - the degree to which an individual believes that using a new technology will help him or her to attain gains in job performance. Social influence and trust in the CDSS were other factors in the path model. r2 for the model was 0.63 – indicating that almost two thirds of the variance in the model was explained. The only significant effect in the multigroup analyses of path differences between two subgroups was for PROPOSE use and social influence (p = 0.01)
Interpretation / Conclusion: Shared decision making is essential to meet patient expectations in spine surgery. A trustworthy CDSS with ease of use and satisfactory predictive ability and promoted by the leadership will stand the best chance of acceptation and bridging the communication gap between surgeon and patient.

20. Evaluation of an Artificial Intelligence (AI) Based Scoliosis Measurement Program
Miao Wang1, Ming Sun2, Haisheng Li2, Yukang Yang3, Peter Helmig2, Kestutis Valancius2, Cody Bunger2, Tianyu Liu3, Yu Wang4, Ebbe Hansen2
1. Department of Orthopaedics, Regions Hospital Horsens, Denmark 2. Department of Orthopaedics, Aarhus University Hospital, Denmark 3. Department of Automation, Tsinghua University, China 4. Department of Orthopaedics,Beijing University Hospital, China

Background: Scoliosis refers to the three-dimensional deformity of the spine with one or several segments of the spine bent laterally with vertebral rotation. Reliable measurement of spinal curve is crucial for determining therapeutic decision for scoliosis patients. Cobb Angle is the gold standard, but it is an objective measurement with variant from surgeon to surgeon. A solid and reliable measurement tool is needed. Artificial Intelligence has showed great potential in image measurement.
Aim: To compare the performance of an AI based scoliosis measurement tool with senior scoliosis surgeons in Denmark
Materials and Methods: Trained the AI algorithm with 650 scoliosis X-ray images by using Convolutional Neural Network (CNN). Another 100 scoliosis X-ray have been assigned into two groups randomly. Each group has been measured by AI and two surgeons. All four surgeons measured Cobb angles twice with minimal 3 weeks interval. Intraclass correlation coefficients (ICC) were used to determine the interobserver and intraobserver reliabilities. (ICC can range from 0 to 1, where 0 means no reliability and 1 means perfect reliability, ICC between 0.9 to 1 means excellent reliability). The correlation of scoliosis curve angle measurements between AI program and senior surgeons have been tested with Pearson correlation coefficient and the mean absolute error.
Results: ICC is 0.96 in group 1 and 0.90 in group 2, which means excellent reliability. Pearson Correlation coefficient was 0.956 in group 1 and 0.930 in group 2. Spearman rank-order correlation was 0.960 (p < 0.001) in group 1 and 0.900 (p < 0.001) in group 2. The absolute error between AI and surgeons are 3.5°±3.1°in group 1 and 5.0°±3.8° in group 2. In total the absolute error is 4.2°±3.3°. In 67% of all cases, there were only 0-5° different between AI program and spine surgeons.
Interpretation / Conclusion: There is statistic correlation of Cobb angle measurement between our new developed AI program and senior spine surgeons. The reliability is statistic excellent in both patients’ groups. Our new AI program can provide reliable Cobb angle measurement as good as senior spine surgeons.