In silico medical device testing of anatomically and mechanically conforming patient-specific spinal fusion cages designed by full-scale topology optimisation.

A full-scale topology optimisation formulation has been developed to automate the design of cages used in instrumented transforaminal lumbar interbody fusion. The method incorporates the mechanical response of the adjacent bone structures in the optimisation process, yielding patient-specific spinal fusion cages that both anatomically and mechanically conform to the patient, effectively mitigating subsidence risk compared to generic, off-the-shelf cages and patient-specific devices. In this study, in silico medical device testing on a cohort of seven patients was performed to investigate the effectiveness of the anatomically and mechanically conforming devices using titanium and PEEK implant materials. A median reduction in the subsidence risk by 89% for titanium and 94% for PEEK implant materials was demonstrated compared to an off-the-shelf implant. A median reduction of 75% was achieved for a PEEK implant material compared to an anatomically conforming implant. A credibility assessment of the computational model used to predict the subsidence risk was provided according to the ASME V&V40-2018 standard.

Anatomically and mechanically conforming patient-specific spinal fusion cages designed by full-scale topology optimization.

Cage subsidence after instrumented lumbar spinal fusion surgery remains a significant cause of treatment failure, specifically for posterior or transforaminal lumbar interbody fusion. Recent advancements in computational techniques and additive manufacturing, have enabled the development of patient-specific implants and implant optimization to specific functional targets. This study aimed to introduce a novel full-scale topology optimization formulation that takes the structural response of the adjacent bone structures into account in the optimization process. The formulation includes maximum and minimum principal strain constraints that lower strain concentrations in the adjacent vertebrae. This optimization approach resulted in anatomically and mechanically conforming spinal fusion cages. Subsidence risk was quantified in a commercial finite element solver for off-the-shelf, anatomically conforming and the optimized cages, in two representative patients. We demonstrated that the anatomically and mechanically conforming cages reduced subsidence risk by 91% compared to an off-the-shelf implant with the same footprint for a patient with normal bone quality and 54% for a patient with osteopenia. Prototypes of the optimized cage were additively manufactured and mechanically tested to evaluate the manufacturability and integrity of the design and to validate the finite element model.

Patient-reported outcome of lumbar decompression with instrumented fusion for low-grade spondylolisthesis: influence of pathology and baseline symptoms.

INTRODUCTION: Low-grade isthmic and degenerative spondylolisthesis (DS) of the lumbar spine are distinct pathologies but both can be treated with lumbar decompression with fusion. In a very large cohort, we compared patient-reported outcome in relation to the pathology and chief complaint at baseline. METHODS: This was a retrospective analysis using the EUROSPINE Spine Tango Registry. We included 582 patients (age 60 ± 15 years; 65% female), divided into four groups based on two variables: type of spondylolisthesis and chief pain complaint (leg pain (LP) versus back pain). Patients completed the COMI preoperatively and up to 5 years follow-up (FU), and rated global treatment outcome (GTO). Regression models were used to predict COMI-scores at FU. Pain scores and satisfaction ratings were analysed. RESULTS: All patients experienced pronounced reductions in COMI scores. Relative to the other groups, the DS-LP group showed between 5% and 11% greater COMI score reduction (p < 0.01 up to 2 years' FU). This group also performed best with respect to pain outcomes and satisfaction. Long-term GTO was 93% at the 5 year FU, compared with between 82% and 86% in the other groups. CONCLUSION: Regardless of the type of spondylolisthesis, all groups experienced an improvement in COMI score after surgery. Patients with DS and LP as their chief complaint appear to benefit more than other patients. These results are the first to show that the type of the spondylolisthesis and its chief complaint have an impact on surgical outcome. They will be informative for the consent process prior to surgery and can be used to build predictive models for individual outcome.

Estimating lumbar bone mineral density from conventional MRI and radiographs with deep learning in spine patients.

PURPOSE: This study aimed to develop machine learning methods to estimate bone mineral density and 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. METHODS: A database of 429 patients subjected to lumbar MRI, radiographs and dual-energy x-ray absorptiometry within 6 months was created from an institutional 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 bone mineral density; (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 of 0.15-0.16 g/cm2 for the direct estimation of bone mineral density, and areas under the receiver operating characteristic 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. CONCLUSIONS: The models showed good discriminative performances in detecting cases of low bone mineral density, 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.

Cyclic testing of standalone ALIF versus TLIF in lumbosacral spines of low bone mineral density: an ex vivo biomechanical study.

PURPOSE: Screwed anterior lumbar interbody fusion (SALIF) alleviates the need for supplemental posterior fixation leading to reduction of perioperative morbidity. Specifically, elderly and multimorbid patients would benefit from shorter operative time and faster recovery but tend to have low bone mineral density (BMD). The current study aimed to compare loosening, defined as increase of ROM and NZ, of SALIF versus transforaminal lumbar interbody fusion (TLIF) under cyclic loading in cadaveric spines with reduced BMD. METHODS: Twelve human spines (L4-S2; 6 male 6 female donors; age 70.6 ± 19.6; trabecular BMD of L5 84.2 ± 24.4 mgHA/cm3, range 51-119 mgHA/cm3) were assigned to two groups. SALIF or TLIF were instrumented at L5/S1. Range of motion (ROM) and neutral zone (NZ) were assessed before and after axial cyclic loading (0-1150 N, 2000 cycles, 0.5 Hz) in flexion-extension (Flex-Ext), lateral bending, (LB), axial rotation (AR). RESULTS: ROM of the SALIF specimens increased significantly in all loading directions (p ≤ 0.041), except for left AR (p = 0.053), whereas for TLIF it increased significantly in left LB (p = 0.033) and Flex (p = 0.015). NZ of SALIF showed increase in Flex-Ext and LB, whereas NZ of TLIF did not increase significantly in any motion direction. CONCLUSIONS: Axial compression loading caused loosening of SALIF in Flex-Ext and LB, but not TLIF at L5/S1 in low BMD specimens. Nevertheless, Post-cyclic ROM and NZ of SALIF is comparable to TLIF. This suggests that, neither construct is optimal for the use in patients with reduced BMD.

Are large language models valid tools for patient information on lumbar disc herniation? The spine surgeons' perspective.

Introduction: Generative AI is revolutionizing patient education in healthcare, particularly through chatbots that offer personalized, clear medical information. Reliability and accuracy are vital in AI-driven patient education. Research question: How effective are Large Language Models (LLM), such as ChatGPT and Google Bard, in delivering accurate and understandable patient education on lumbar disc herniation? Material and methods: Ten Frequently Asked Questions about lumbar disc herniation were selected from 133 questions and were submitted to three LLMs. Six experienced spine surgeons rated the responses on a scale from "excellent" to "unsatisfactory," and evaluated the answers for exhaustiveness, clarity, empathy, and length. Statistical analysis involved Fleiss Kappa, Chi-square, and Friedman tests. Results: Out of the responses, 27.2% were excellent, 43.9% satisfactory with minimal clarification, 18.3% satisfactory with moderate clarification, and 10.6% unsatisfactory. There were no significant differences in overall ratings among the LLMs (p = 0.90); however, inter-rater reliability was not achieved, and large differences among raters were detected in the distribution of answer frequencies. Overall, ratings varied among the 10 answers (p = 0.043). The average ratings for exhaustiveness, clarity, empathy, and length were above 3.5/5. Discussion and conclusion: LLMs show potential in patient education for lumbar spine surgery, with generally positive feedback from evaluators. The new EU AI Act, enforcing strict regulation on AI systems, highlights the need for rigorous oversight in medical contexts. In the current study, the variability in evaluations and occasional inaccuracies underline the need for continuous improvement. Future research should involve more advanced models to enhance patient-physician communication.

The use of the Core Yellow Flags Index for the assessment of psychosocial distress in patients undergoing surgery of the cervical spine.

BACKGROUND: Psychosocial distress (the presence of yellow flags) has been linked to poor outcomes in spine surgery. The Core Yellow Flags Index (CYFI), a short instrument assessing the 4 main yellow flags, was developed for use in patients undergoing lumbar spine surgery. This study evaluated its ability to predict outcome in patients undergoing cervical spine surgery. METHODS: Patients with degenerative spinal disorders (excluding myelopathy) operated in one centre, from 2015 to 2019, were asked to complete the CYFI at baseline and the Core Outcome Measures Index (COMI) at baseline and 3 and 12 months after surgery. The relationship between CYFI and COMI scores at baseline as well as the predictive ability of the CYFI on the COMI follow-up scores were tested using structural equation modelling. RESULTS: From 731 eligible patients, 547 (61.0 ± 12.5 years; 57.2% female) completed forms at all three timepoints. On a cross-sectional basis, preoperative CYFI and COMI scores were highly correlated (ß = 0.54, in men and 0.51 in women; each p < 0.001). CYFI added significantly and independently to the prediction of COMI at 3 months' FU in men (ß = 0.36) and 12 months' FU in men and women (both ß = 0.20) (all p < 0.001). CONCLUSION: The CYFI had a low to moderate but significant and independent association with cervical spine surgery outcomes. Implementing the CYFI in the preoperative workup of these patients could help refine outcome predictions and better manage patient expectations.

Comparing image normalization techniques in an end-to-end model for automated modic changes classification from MRI images.

Introduction: Modic Changes (MCs) are MRI alterations in spine vertebrae's signal intensity. This study introduces an end-to-end model to automatically detect and classify MCs in lumbar MRIs. The model's two-step process involves locating intervertebral regions and then categorizing MC types (MC0, MC1, MC2) using paired T1-and T2-weighted images. This approach offers a promising solution for efficient and standardized MC assessment. Research question: The aim is to investigate how different MRI normalization techniques affect MCs classification and how the model can be used in a clinical setting. Material and methods: A combination of Faster R-CNN and a 3D Convolutional Neural Network (CNN) is employed. The model first identifies intervertebral regions and then classifies MC types (MC0, MC1, MC2) using paired T1-and T2-weighted lumbar MRIs. Two datasets are used for model development and evaluation. Results: The detection model achieves high accuracy in identifying intervertebral areas, with Intersection over Union (IoU) values above 0.7, indicating strong localization alignment. Confidence scores above 0.9 demonstrate the model's accurate levels identification. In the classification task, standardization proves the best performances for MC type assessment, achieving mean sensitivities of 0.83 for MC0, 0.85 for MC1, and 0.78 for MC2, along with balanced accuracy of 0.80 and F1 score of 0.88. Discussion and conclusion: The study's end-to-end model shows promise in automating MC assessment, contributing to standardized diagnostics and treatment planning. Limitations include dataset size, class imbalance, and lack of external validation. Future research should focus on external validation, refining model generalization, and improving clinical applicability.

Evaluation of "appropriate use criteria" for surgical decision-making in lumbar degenerative spondylolisthesis. A controlled, multicentre, prospective observational study.

INTRODUCTION: Selecting patients with lumbar degenerative spondylolisthesis (LDS) for surgery is difficult. Appropriate use criteria (AUC) have been developed to clarify the indications for LDS surgery but have not been evaluated in controlled studies. METHODS: This prospective, controlled, multicentre study involved 908 patients (561 surgical and 347 non-surgical controls; 69.5 ± 9.7y; 69% female), treated as per normal clinical practice. Their appropriateness for surgery was afterwards determined using the AUC. They completed the Core Outcome Measures Index (COMI) at baseline and 12 months' follow-up. Multiple regression adjusting for confounders evaluated the influence of appropriateness designation and treatment received on the 12-month COMI and achievement of MCIC (≥ 2.2-point-reduction). RESULTS: As per convention, appropriate (A) and uncertain (U) groups were combined for comparison with the inappropriate (I) group. For the adjusted 12-month COMI, the benefit of surgery relative to non-surgical care was not significantly greater for the A/U than the I group (p = 0.189). There was, however, a greater treatment effect of surgery for those with higher baseline COMI (p = 0.035). The groups' adjusted probabilities of achieving MCIC were: 83% (A/U, receiving surgery), 71% (I, receiving surgery), 50% (A/U, receiving non-surgical care), and 32% (I, receiving non-surgical care). CONCLUSIONS: A/U patients receiving surgery had the highest chances of achieving MCIC, but the AUC were not able to identify which patients had a greater treatment effect of surgery relative to non-surgical care. The identification of other characteristics that predict a greater treatment effect of surgery, in addition to baseline COMI, is required to improve decision-making.

A decade of experience in over 300 surgically treated spine patients with long-term oral anticoagulation: a propensity score matched cohort study.

PURPOSE: The aim of this study was to investigate the risks and outcomes of patients with long-term oral anticoagulation (OAC) undergoing spine surgery. METHODS: All patients on long-term OAC who underwent spine surgery between 01/2005 and 06/2015 were included. Data were prospectively collected within our in-house Spine Surgery registry and retrospectively supplemented with patient chart and administrative database information. A 1:1 propensity score-matched group of patients without OAC from the same time interval served as control. Primary outcomes were post-operative bleeding, wound complications and thromboembolic events up to 90 days post-surgery. Secondary outcomes included intraoperative blood loss, length of hospital stay, death and 3-month post-operative patient-rated outcomes. RESULTS: In comparison with the control group, patients with OAC (n = 332) had a 3.4-fold (95%CI 1.3-9.0) higher risk for post-operative bleeding, whereas the risks for wound complications and thromboembolic events were comparable between groups. The higher bleeding risk was driven by a higher rate of extraspinal haematomas (3.3% vs. 0.6%; p = 0.001), while there was no difference in epidural haematomas and haematoma evacuations. Risk factors for adverse events among patients with OAC were mechanical heart valves, posterior neck surgery, blood loss > 1000 mL, age, female sex, BMI > 30 kg/m2 and post-operative PTT levels. At 3-month follow-up, most patients reported favourable outcomes with no difference between groups. CONCLUSION: Although OAC patients have a higher risk for complications after spine surgery, the risk for major events is low and patients benefit similarly from surgery.

Patient-reported outcomes 1 and 2 years after transforaminal thoracic interbody fusion (TTIF).

STUDY DESIGN: Retrospective Cohort Study with prospectively collected data. PURPOSE: Transforaminal interbody fusion was initially designed for the lumbar spine. A similar approach was later introduced for the thoracic spine (TTIF). Here we report the surgical technique and the Core Outcome Measures Index (COMI) at 1-year and 2-year follow-ups, as well as the sagittal radiographic kyphosis correction of TTIF, achieved at 1 year and the latest follow-up. METHODS: All TTIF procedures from 2012 to 2020 were included. COMI scores were collected preoperatively and at 1- and 2-year follow-ups. The sagittal angle between the upper and lower endplates at the segment where TTIF was performed was measured on preoperative, 1-year postoperative, and last available radiographs. RESULTS: Seventy-nine TTIF procedures were performed for 64 patients (36% males; mean age 67.5 (SD 15.3) years). COMI score reduced from a mean value of 8.1 (SD 1.4) preoperatively to 4.7 (SD 2.7) at 1-year follow-up and 4.7 (SD 2.7) at 2-year follow-up. The mean correction of segmental kyphosis was 10.8 (SD 7.3, p < 0.0001) degrees at 1-year follow-up and 9.3 (SD 7.0, p < 0.0001) degrees at the final follow-up 3.4 (SD 1.4) years after the operation. Kaplan-Meier analysis for reoperations showed a 5-year survival of 91% (95% CI 0.795-1) for primary TTIF operations and survival of 77% (95% CI 0.651-0.899) for TTIFs performed after earlier fusion operations. CONCLUSIONS: TTIF is a feasible procedure in the thoracic spine. Kyphosis correction of approximately 10° was maintained at 1-year and final follow-up. Over 69% at 1-year and 61% at 2-year follow-up achieved MCID for COMI.

Far Lateral Lumbar Decompression Using the Far-Lateral Approach: Patient Reported Outcome is Associated with the Involved Vertebral Level and Coronal Segmental Angle.

STUDY DESIGN: Single centre retrospective study of prospectively collected data. OBJECTIVE: Analyse factors associated with patient reported outcome after far lateral decompression surgery (FLDS) for lumbar nerve root compression using the far-lateral approach. SUMMARY OF BACKGROUND DATA: To date, no studies have investigated the influence of vertebral level, coronal segmental Cobb angle, and the nature of the compressive tissue (hard/soft) on patient reported outcome following FLDS. METHODS: Patients who had undergone FLDS between 2005 and 2020 were included. Coronal segmental angle (CSCA) was measured on preoperative, posteroanterior radiographs. Primary outcome measure was the Core Outcome Measures Index (COMI) score at 2 years' follow-up (2Y-FU). Patients who had undergone microsurgical decompression using a midline approach (MID) served as a comparator group. RESULTS: There were 148 FLDS and 463 MID patients. In both groups there was a significant improvement in COMI score from preoperative to 2Y-FU (P<0.0001), with greater improvement in patients treated at higher vertebral levels than in those treated at L5/S1 (P=0.014). Baseline COMI, ASA grade, BMI, and low back pain as the "chief complaint" all had a significant association with the 2-year COMI score. The nature of compressive tissue showed no association with COMI score at 2Y-FU. In the FLDS group, there was a statistically significant correlation between the preoperative CSCA and change in COMI score preoperatively to 2Y-FU (P<0.001). The association was retained in multiple regression analysis controlling for confounders. A one-degree increase in CSCA was associated with a 0.35-point worse COMI score at 2Y-FU (P=0.003). CONCLUSION: Treatment of far lateral nerve root compression showed overall good patient reported outcome, but with less improvement with advanced coronal segmental angulation. Modified approaches and techniques might be preferable for the level L5/S1.

Automatic Calculation of Cervical Spine Parameters Using Deep Learning: Development and Validation on an External Dataset.

STUDY DESIGN: Retrospective data analysis. OBJECTIVES: This study aims to develop a deep learning model for the automatic calculation of some important spine parameters from lateral cervical radiographs. METHODS: We collected two datasets from two different institutions. The first dataset of 1498 images was used to train and optimize the model to find the best hyperparameters while the second dataset of 79 images was used as an external validation set to evaluate the robustness and generalizability of our model. The performance of the model was assessed by calculating the median absolute errors between the model prediction and the ground truth for the following parameters: T1 slope, C7 slope, C2-C7 angle, C2-C6 angle, Sagittal Vertical Axis (SVA), C0-C2, Redlund-Johnell distance (RJD), the cranial tilting (CT) and the craniocervical angle (CCA). RESULTS: Regarding the angles, we found median errors of 1.66° (SD 2.46°), 1.56° (1.95°), 2.46° (SD 2.55), 1.85° (SD 3.93°), 1.25° (SD 1.83°), .29° (SD .31°) and .67° (SD .77°) for T1 slope, C7 slope, C2-C7, C2-C6, C0-C2, CT, and CCA respectively. As concerns the distances, we found median errors of .55 mm (SD .47 mm) and .47 mm (.62 mm) for SVA and RJD respectively. CONCLUSIONS: In this work, we developed a model that was able to accurately predict cervical spine parameters from lateral cervical radiographs. In particular, the performances on the external validation set demonstrate the robustness and the high degree of generalizability of our model on images acquired in a different institution.

Does loss to follow-up lead to an overestimation of treatment success? Findings from a spine surgery registry of over 15,000 patients.

PURPOSE: Patient-reported outcome measures (PROMs) are integral to the assessment of treatment success, but loss to follow-up (attrition) may lead to bias in the results reported. We sought to evaluate the extent, nature and implications of attrition in a long-established, single-centre spine registry. METHODS: The registry contained the data of 15,264 consecutive spine surgery patients. PROMs included the Core Outcome Measures Index (COMI) and a rating of the Global Treatment Outcome (GTO) and Satisfaction with Care. Baseline characteristics associated with returning a 12-month PROM (= "responder") were analysed (logistic regression). The 3-month outcomes of 12-month responders versus 12-month non-responders were compared (ANOVA and Chi-square). RESULTS: In total, 14,758/15,264 (97%) patients (60 ± 17y; 46% men) had consented to the use of their registry data for research. Preoperative, 3-month post-operative and 12-month post-operative PROMs were returned by 91, 90 and 86%, respectively. Factors associated with being a 12-month responder included: greater age, born in the country of the study, no private/semi-private insurance, better baseline status (lower COMI score), fewer previous surgeries, less comorbidity and no perioperative medical complications. 12-month non-responders had shown significantly worse outcomes in their 3-month PROMs than had 12-month responders (respectively, 66% vs 80% good GTO ("treatment helped/helped a lot"); 77% vs 88% satisfied/very satisfied; and 49% vs 63% achieved MCIC on COMI). CONCLUSION: Although attrition in this cohort was relatively low, 12-month non-responders displayed distinctive characteristics and their early outcomes were significantly worse than those of 12-month responders. If loss to follow-up is not addressed, treatment success will likely be overestimated, with erroneously optimistic results being reported.

Factors associated with an increased risk of developing postoperative symptomatic lumbar spondylolisthesis after decompression surgery: an explorative two-centre international cohort study.

PURPOSE: Symptomatic lumbar spinal stenosis can be treated with decompression surgery. A recent review reported that, after decompression surgery, 1.6-32.0% of patients develop postoperative symptomatic spondylolisthesis and may therefore be indicated for lumbar fusion surgery. The latter can be more challenging due to the altered anatomy and scar tissue. It remains unclear why some patients get recurrent neurological complaints due to postoperative symptomatic spondylolisthesis, though some associations have been suggested. This study explores the association between key demographic, biological and radiological factors and postoperative symptomatic spondylolisthesis after lumbar decompression. METHODS: This retrospective cohort study included patients who had undergone lumbar spinal decompression surgery between January 2014 and December 2016 at one of two Spine Centres in the Netherlands or Switzerland and had a follow-up of two years. Patient characteristics, details of the surgical procedure and recurrent neurological complaints were retrieved from patient files. Preoperative MRI scans and conventional radiograms (CRs) of the lumbar spine were evaluated for multiple morphological characteristics. Postoperative spondylolisthesis was evaluated on postoperative MRI scans. For variables assessed on a whole patient basis, patients with and without postoperative symptomatic spondylolisthesis were compared. For variables assessed on the basis of the operated segment(s), surgical levels that did or did not develop postoperative spondylolisthesis were compared. Univariable and multivariable logistic regression analyses were used to identify associations with postoperative symptomatic spondylolisthesis. RESULTS: Seven hundred and sixteen patients with 1094 surgical levels were included in the analyses. (In total, 300 patients had undergone multilevel surgery.) ICCs for intraobserver and interobserver reliability of CR and MRI variables ranged between 0.81 and 0.99 and 0.67 and 0.97, respectively. In total, 66 of 716 included patients suffered from postoperative symptomatic spondylolisthesis (9.2%). Multivariable regression analyses of patient-basis variables showed that being female [odds ratio (OR) 1.2, 95%CI 1.07-3.09] was associated with postoperative symptomatic spondylolisthesis. Higher BMI (OR 0.93, 95%CI 0.88-0.99) was associated with a lower probability of having postoperative symptomatic spondylolisthesis. Multivariable regression analyses of surgical level-basis variables showed that levels with preoperative spondylolisthesis (OR 17.30, 95%CI 10.27-29.07) and the level of surgery, most importantly level L4L5 compared with levels L1L3 (OR 2.80, 95%CI 0.78-10.08), were associated with postoperative symptomatic spondylolisthesis; greater facet joint angles (i.e. less sagittal-oriented facets) were associated with a lower probability of postoperative symptomatic spondylolisthesis (OR 0.97, 95%CI 0.95-0.99). CONCLUSION: Being female was associated with a higher probability of having postoperative symptomatic spondylolisthesis, while having a higher BMI was associated with a lower probability. When looking at factors related to postoperative symptomatic spondylolisthesis at the surgical level, preoperative spondylolisthesis, more sagittal orientated facet angles and surgical level (most significantly level L4L5 compared to levels L1L3) showed significant associations. These associations could be used as a basis for devising patient selection criteria, stratifying patients or performing subgroup analyses in future studies regarding decompression surgery with or without fusion.

Association between sagittal alignment and loads at the adjacent segment in the fused spine: a combined clinical and musculoskeletal modeling study of 205 patients with adult spinal deformity.

PURPOSE: Sagittal malalignment is a risk factor for mechanical complications after surgery for adult spinal deformity (ASD). Spinal loads, modulated by sagittal alignment, may explain this relationship. The aims of this study were to investigate the relationships between: (1) postoperative changes in loads at the proximal segment and realignment, and (2) absolute postoperative loads and postoperative alignment measures. METHODS: A previously validated musculoskeletal model of the whole spine was applied to study a clinical sample of 205 patients with ASD. Based on clinical and radiographic data, pre-and postoperative patient-specific alignments were simulated to predict loads at the proximal segment adjacent to the spinal fusion. RESULTS: Weak-to-moderate associations were found between pre-to-postop changes in lumbar lordosis, LL (r = - 0.23, r = - 0.43; p < 0.001), global tilt, GT (r = 0.26, r = 0.38; p < 0.001) and the Global Alignment and Proportion score, GAP (r = 0.26, r = 0.37; p < 0.001), and changes in compressive and shear forces at the proximal segment. GAP score parameters, thoracic kyphosis measurements and the slope of upper instrumented vertebra were associated with changes in shear. In patients with T10-pelvis fusion, moderate-to-strong associations were found between postoperative sagittal alignment measures and compressive and shear loads, with GT showing the strongest correlations (r = 0.75, r = 0.73, p < 0.001). CONCLUSIONS: Spinal loads were estimated for patient-specific full spinal alignment profiles in a large cohort of patients with ASD pre-and postoperatively. Loads on the proximal segments were greater in association with sagittal malalignment and malorientation of proximal vertebra. Future work should explore whether they provide a causative mechanism explaining the associated risk of proximal junction complications.

Management and outcome of spinal implant-associated surgical site infections in patients with posterior instrumentation: analysis of 176 cases.

PURPOSE: The management of implant-associated surgical site infections (SSI) in patients with posterior instrumentation is challenging. Evidence regarding the most appropriate treatment and the need for removal of implants is equivocal. We sought to evaluate the management and outcome of such patients at our institution. METHODS: We searched our prospectively documented databases for eligible patients with posterior spinal instrumentation, excluding the cervical spine (January 2008-June 2018). Patient files were reviewed, demographic data and treatment details were recorded. Patient-reported outcome (PRO) was assessed with the Core Outcome Measures Index (COMI) preoperatively and postoperatively at 3 and 12 months. RESULTS: A total of 170 patients underwent 210 revisions for 176 SSIs. Two-thirds presented within four weeks (105/176, 59.7%, median 22.5d, 7d-11.1y). The most common pathogens were Staphylococcus aureus (n = 79/210, 37.6%) and Staphylococcus epidermidis (n = 56/210, 26.7%). Debridement and implant retention was performed in 135/210 (64.3%) revisions and partial replacement in 62/210 (29.5%). In 28/176 SSI (15.9%), persistent infection required multiple revisions (≤ 4). Surgery was followed by intravenous and oral antimicrobial treatment (10-12w). In 139/176 SSIs (79%) with ≥ 1y follow-up, infection was cured in 115/139 (82.7%); relapse occurred in 9 (relapse rate: 5.1%). Two patients (1.4%) died. COMI decreased significantly (8.2 ± 1.5 vs. 4.8 ± 2.9, p < 0.0001) over 12 months. 72.7% of patients were (very) satisfied with their care. CONCLUSION: Patients with SSI after posterior (thoraco-)lumbo(-sacral) instrumentation can be successfully treated in most cases with surgical and specific antibiotic treatment. An interdisciplinary approach is recommended. Loose implants should be replaced. In some cases, multiple revisions may be necessary. Patient outcomes were satisfactory.

Revision surgery for incomplete resection or recurrence of cervical spine chordoma: a consecutive case series of 24 patients.

PURPOSE: Chordomas are rare tumors with an annual incidence of approximately one per million. Chordomas rarely metastasize but show a high local recurrence rate. Therefore, these patients present a major clinical challenge, and there is a paucity of the literature regarding the outcome after revision surgery of cervical spine chordomas. Available studies suggest a significantly worse outcome in revision scenarios. The purpose of this study is to analyze the survival rate, and complications of patients that underwent revision surgery for local recurrence or incomplete resection of chordoma at the craniocervical junction or at the cervical spine. METHODS: 24 consecutive patients that underwent revision surgery for cervical spine chordoma remnants or recurrence at a single center were reviewed retrospectively. We analyzed patient-specific surgical treatment strategies, complications, and outcome. Kaplan-Meier estimator was used to analyze five-year overall survival. RESULTS: Gross total resection was achieved in 17 cases. Seven patients developed dehiscence of the pharyngeal wall, being the most common long-term complication. No instability was observed. Postoperatively, four patients received proton beam radiotherapy and 12 patients had combined photon and proton beam radiotherapy. The five-year overall survival rate was 72.6%. CONCLUSION: With thorough preoperative planning, appropriate surgical techniques, and the addition of adjuvant radiotherapy, results similar to those in primary surgery can be achieved.

Development of a model to predict the probability of incurring a complication during spine surgery.

PURPOSE: Predictive models in spine surgery are of use in shared decision-making. This study sought to develop multivariable models to predict the probability of general and surgical perioperative complications of spinal surgery for lumbar degenerative diseases. METHODS: Data came from EUROSPINE's Spine Tango Registry (1.2012-12.2017). Separate prediction models were built for surgical and general complications. Potential predictors included age, gender, previous spine surgery, additional pathology, BMI, smoking status, morbidity, prophylaxis, technology used, and the modified Mirza invasiveness index score. Complete case multiple logistic regression was used. Discrimination was assessed using area under the receiver operating characteristic curve (AUC) with 95% confidence intervals (CI). Plots were used to assess the calibration of the models. RESULTS: Overall, 23'714/68'111 patients (54.6%) were available for complete case analysis: 763 (3.2%) had a general complication, with ASA score being strongly predictive (ASA-2 OR 1.6, 95% CI 1.20-2.12; ASA-3 OR 2.98, 95% CI 2.19-4.07; ASA-4 OR 5.62, 95% CI 3.04-10.41), while 2534 (10.7%) had a surgical complication, with previous surgery at the same level being an important predictor (OR 1.9, 95%CI 1.71-2.12). Respectively, model AUCs were 0.74 (95% CI, 0.72-0.76) and 0.64 (95% CI, 0.62-0.65), and calibration was good up to predicted probabilities of 0.30 and 0.25, respectively. CONCLUSION: We developed two models to predict complications associated with spinal surgery. Surgical complications were predicted with less discriminative ability than general complications. Reoperation at the same level was strongly predictive of surgical complications and a higher ASA score, of general complications. A web-based prediction tool was developed at https://sst.webauthor.com/go/fx/run.cfm?fx=SSTCalculator .

Validation of a surgical invasiveness index in patients with lumbar spinal disorders registered in the Spine Tango registry.

INTRODUCTION: Being able to quantify the invasiveness of a surgical procedure is important to weigh up its associated risks, since invasiveness governs the blood loss, operative time and likelihood of complications. Mirza et al. (Spine (Phila Pa 1976) 33:2651-2661, 2008) published an invasiveness index for spinal surgery. We evaluated the validity of a modified version of the Mirza invasiveness index (mMII), adapted for use with registry data. METHODS: A cross-sectional analysis was performed with data acquired from the Spine Tango registry including 21,634 patients. The mMII was calculated as the sum of six possible interventions on each vertebral level: decompression, fusion and stabilization either on anterior or posterior structures. The association between the mMII and blood loss, operative time and complications was evaluated using multiple regression, adjusting for possible confounders. RESULTS: The mean (± SD) mMII was 3.9 ± 5.0 (range 0-40). A 1-point increase in the mMII was associated with an additional blood loss of 12.8% (95% CI 12.6-13.0; p < 0.001) and an increase of operative time of 10.4 min (95% CI 10.20-10.53; p < 0.001). The R2 for the blood loss model was of 43% and for operative time, 47%. The mean mMII was significantly (p < 0.001) higher in patients with surgical complications (4.5 ± 5.6) and general medical complications (6.5 ± 7.0) compared to those without (3.8 ± 4.9). Our results were comparable to those reported in the original publication of Mirza et al. CONCLUSION: The mMII appeared to be a valid measure of surgical invasiveness in our study population. It can be used in predictor models and to adjust for surgical case-mix when comparing outcomes in different studies or different hospitals/surgeons in a registry.