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1. Utility of the Modified 5-Items Frailty Index to Predict Complications and Mortality After Elective Cervical, Thoracic and Lumbar Posterior Spine Fusion Surgery: Multicentric Analysis From ACS-NSQIP Database.

Author

Camino-Willhuber, Gaston, Choi, Jeffrey, Holc, Fernando, Oyadomari, Sarah, Guiroy, Alfredo, Bow, Hansen, Hashmi, Sohaib, Oh, Michael, Bhatia, Nitin, and Lee, Yu-Po

Subjects
complications, modified frailty index, readmission, spine surgery
Abstract

STUDY DESIGN: Retrospective review of multicentric data. OBJECTIVES: The modified 5-item frailty index is a relatively new tool to assess the post-operative complication risks. It has been recently shown a good predictive value after posterior lumbar fusion. We aimed to compare the predictive value of the modified 5-item frailty index in cervical, thoracic and lumbar surgery. METHODS: The American College of Surgeons - National Surgical Quality Improvement Program (ACS-NSQIP) Database 2015-2020 was used to identify patients who underwent elective posterior cervical, thoracic, or lumbar fusion surgeries for degenerative conditions. The mFI-5 score was calculated based on the presence of 5 co-morbidities: congestive heart failure within 30 days prior to surgery, insulin-dependent or noninsulin-dependent diabetes mellitus, chronic obstructive pulmonary disease or pneumonia, partially dependent or totally dependent functional health status at time of surgery, and hypertension requiring medication. Multivariate analysis was used to assess the independent impact of increasing mFI-5 score on the postoperative morbidity while controlling for baseline clinical characteristics. RESULTS: 53 252 patients were included with the mean age of 64.2 ± 7.2. 7946 suffered medical complications (14.9%), 1565 had surgical complications (2.9%), and 3385 were readmitted (6.3%), 363 died (.68%) within 30 days postoperative (6.3%). The mFI-5 items score was significantly associated with higher rates of complications, readmission, and mortality in cervical, thoracic, and lumbar posterior fusion surgery. CONCLUSION: The modified 5-item frailty score is a reliable tool to predict complications, readmission, and mortality in patients planned for elective posterior spinal fusion surgery.

Published
2024

2. Prevention of Surgical Site Infections in Spine Surgery: An International Survey of Clinical Practices Among Expert Spine Surgeons.

Author

Sekhon, Lali, Shaffrey, Christopher, Smith, Justin, Hart, Robert, Kim, Han, Wang, Jeffrey, Ha, Yoon, Kwan, Kenny, Hai, Yong, Valacco, Marcelo, Falavigna, Asdrubal, Taboada, Néstor, Guiroy, Alfredo, Emmerich, Juan, Meyer, Bernhard, Kandziora, Frank, Thomé, Claudius, Loibl, Markus, Peul, Wilco, Gasbarrini, Alessandro, Obeid, Ibrahim, Gehrchen, Martin, Trampuz, Andrej, Vajkoczy, Peter, Onken, Julia, Tkatschenko, Dimitri, Hansen, Sonja, Koch, Julia, Ames, Christopher, Fehlings, Michael, and Berven, Sigurd

Abstract

STUDY DESIGN: Questionnaire-based survey. OBJECTIVES: Surgical site infection (SSI) is a common complication in spine surgery but universal guidelines for SSI prevention are lacking. The objectives of this study are to depict a global status quo on implemented prevention strategies in spine surgery, common themes of practice and determine key areas for future research. METHODS: An 80-item survey was distributed among spine surgeons worldwide via email. The questionnaire was designed and approved by an International Consensus Group on spine SSI. Consensus was defined as more than 60% of participants agreeing to a specific prevention strategy. RESULTS: Four hundred seventy-two surgeons participated in the survey. Screening for Staphylococcus aureus (SA) is not common, whereas preoperative decolonization is performed in almost half of all hospitals. Body mass index (BMI) was not important for surgery planning. In contrast, elevated HbA1c level and hypoalbuminemia were often considered as reasons to postpone surgery. Cefazoline is the common drug for antimicrobial prophylaxis. Alcohol-based chlorhexidine is mainly used for skin disinfection. Double-gloving, wound irrigation, and tissue-conserving surgical techniques are routine in the operating room (OR). Local antibiotic administration is not common. Wound closure techniques and postoperative wound dressing routines vary greatly between the participating institutions. CONCLUSIONS: With this study we provide an international overview on the heterogeneity of SSI prevention strategies in spine surgery. We demonstrated a large heterogeneity for pre-, peri- and postoperative measures to prevent SSI. Our data illustrated the need for developing universal guidelines and for testing areas of controversy in prospective clinical trials.

Published
2023

3. Pediatric Spine Trauma

Author

Cabrera Cousiño, Juan P., Guiroy, Alfredo, Carelli, Luis E., Slullitel, Pablo, editor, Rossi, Luciano, editor, and Camino-Willhuber, Gastón, editor

Published
2024
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4. Ankylosing Spondylitis

Author

Guiroy, Alfredo, Cabrera, Juan P., Asghar, Jahangir K., Slullitel, Pablo, editor, Rossi, Luciano, editor, and Camino-Willhuber, Gastón, editor

Published
2024
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6. Neuromuscular Scoliosis

Author

Guiroy, Alfredo, Pabian, Lauren, Asghar, Jahangir, Slullitel, Pablo, editor, Rossi, Luciano, editor, and Camino-Willhuber, Gastón, editor

Published
2024
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7. Improving Meta-Learning Generalization with Activation-Based Early-Stopping

Author

Guiroy, Simon, Pal, Christopher, Mordido, Gonçalo, and Chandar, Sarath

Subjects
Computer Science - Machine Learning, Computer Science - Artificial Intelligence, Statistics - Machine Learning
Abstract

Meta-Learning algorithms for few-shot learning aim to train neural networks capable of generalizing to novel tasks using only a few examples. Early-stopping is critical for performance, halting model training when it reaches optimal generalization to the new task distribution. Early-stopping mechanisms in Meta-Learning typically rely on measuring the model performance on labeled examples from a meta-validation set drawn from the training (source) dataset. This is problematic in few-shot transfer learning settings, where the meta-test set comes from a different target dataset (OOD) and can potentially have a large distributional shift with the meta-validation set. In this work, we propose Activation Based Early-stopping (ABE), an alternative to using validation-based early-stopping for meta-learning. Specifically, we analyze the evolution, during meta-training, of the neural activations at each hidden layer, on a small set of unlabelled support examples from a single task of the target tasks distribution, as this constitutes a minimal and justifiably accessible information from the target problem. Our experiments show that simple, label agnostic statistics on the activations offer an effective way to estimate how the target generalization evolves over time. At each hidden layer, we characterize the activation distributions, from their first and second order moments, then further summarized along the feature dimensions, resulting in a compact yet intuitive characterization in a four-dimensional space. Detecting when, throughout training time, and at which layer, the target activation trajectory diverges from the activation trajectory of the source data, allows us to perform early-stopping and improve generalization in a large array of few-shot transfer learning settings, across different algorithms, source and target datasets., Comment: Accepted at CoLLAs 2022. To be published in Proceedings of Machine Learning Research (PMLR)

Published
2022

8. Treatment of unilateral cervical facet fractures without evidence of dislocation or subluxation: a narrative review and proposed treatment algorithm

Author

Juan Ignacio Cirillo, Guillermo A Ricciardi, Facundo Lisandro Alvarez Lemos, Alfredo Guiroy, Ratko Yurac, and Klaus Schnake

Subjects
cervical facet fracture, isolated, non-displaced, trauma, spine, Orthopedic surgery, RD701-811
Abstract

Isolated cervical spine facet fractures are often overlooked. The primary imaging modality for diagnosing these injuries is a computed tomography scan. Treatment of unilateral cervical facet fractures without evidence of dislocation or subluxation remains controversial. The available evidence regarding treatment options for these fractures is of low quality. Risk factors associated with the failure of nonoperative treatment are: comminution of the articular mass or facet joint, acute radiculopathy, high body mass index, listhesis exceeding 2 mm, fragmental diastasis, acute disc injury, and bilateral fractures or fractures that adversely affect 40% of the intact lateral mass height or have an absolute height of 1 cm.

Published
2024
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9. Trends in primary percutaneous coronary intervention for the treatment of acute coronary ST-elevation myocardial infarction in Latin American countries: insights from the CECI consortium

Author

Alfredo Matías Rodriguez-Granillo, Leonardo Solórzano, Gilberto Vladimir Pérez-Omaña, Diego Ascarrunz, Hernán Pavlovsky, Reynaldo Gomez-Valerio, Ignacio Bertrán, Federico Flores, Julio Parra, Juan Guiroy, Juan Mieres, Francisco Carvajal, Carlos Fernández-Pereira, and Alfredo E. Rodriguez

Subjects
STEMI, primary PCI, gender differences, Latin America, Caribbean, elderly, Diseases of the circulatory (Cardiovascular) system, RC666-701
Abstract

BackgroundST-elevation myocardial infarction (STEMI) requires revascularization treatment, preferably via primary percutaneous coronary interventions (pPCI). There is a lack of data about contemporary management of STEMI in Latin America.MethodsThis was a multicenter, multinational, prospective, and dynamic registry of patients undergoing pPCI in Latin America for STEMI (STEMI/LATAMI Registry) that was carried out in nine centers from five countries (Argentina, Ecuador, Venezuela, Bolivia, and the Dominican Republic) between June 2021 and June 2023. All interventionalists involved in the study were originally trained at the same institution (Centro de Estudios en Cardiología Intervencionista, Buenos Aires, Argentina). The primary objective was to evaluate procedural and in-hospital outcomes of pPCI in STEMI and in-hospital outcome in the Latin America (LATAM) region; as secondary endpoints, we analyzed the following subgroups: differences between pPCI vs. pharmaco-invasive or late presenters, gender, elderly and very elderly patients, cardiogenic shock outcomes, and causes of STEMI.ResultsIn total, 744 STEMI patients who underwent PCI between June 2021 and June 2023 in five countries (nine centers) in our continent were included; 76.3% had a pPCI, 8.1% pharmaco-invasive PCI, and 15.6% had late STEMI PCI. There were no differences in region or center when we evaluated in-hospital and 30 days of death. The rate of procedural success was 96.2%, and the overall in-hospital mortality rate was 2.2%. In the subgroup of pPCI, mean symptom onset-to-balloon time was 295.3 ± 246 min, and mean door-to-balloon time was 55.8 ± 49.9 min. The femoral approach was chosen in 60.5%. In 3.0% of patients, the left main disease was the culprit artery, with 1.63 ± 1.00 stents per patient (564 drug-eluting stents and 652 bare metal stents), with 34 patients receiving only plain optimal balloon angioplasty. Definitive stent thrombosis was related to the infarct artery as the primary cause of STEMI in 7.5% of patients. The use of assistant mechanical devices was low, at 2.1% in the pPCI group. Women were older, with large numbers in very elderly age (≥90 years), greater mortality, and incidence of spontaneous coronary dissection as a cause of STEMI (p

Published
2024
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11. Orthopedic postoperative infection profile and antibiotic sensitivity of 2038 patients across 24 countries – Call for region and institution specific surgical antimicrobial prophylaxis

Author

Mengesha, Mengistu G., Rajasekaran, Shanmuganathan, Ramachandran, Karthik, Sengodan, Vetrivel Chezian, Yasin, Nor Faissal, Williams, Luke Michael, Laubscher, Maritz, Watanabe, Kota, Dastagir, O.Z.M., Akinmadr, Akinola, Fisseha, Hizkyas K., Aziz, Amer, Yurac, Ratko, Gebrehana, Ephrem, AlSaifi, Mohammed, Pathinathan, Kalaventhan, Sudhir, G., Shokri, Amran Ahmed, Chan Kim, Yong, Jonayed, Sharif Ahmed, Kido, Gonzalo R., Ignacio, Jose Manuel, Mohammed, Matiyas Seid, Abubakar, Kabir, Hakim, Jonaed, Duwal Shrestha, Sailendra Kumar, Al Mamun Choudhury, Abdullah, Diallo, Malick, Molina, Marcelo, Patwardhan, Sandeep, Hai, Yong, Ramat, Ali M., Kawai, Momotaro, Cho, Jae Hwan, Shah Kalawar, Rosan Prasad, Choi, Sung-Woo, Zarate-Kalfopulos, Baron, Guiroy, Alfredo, Astur, Nelson, Buunaaim, AlexisD.B., Human, Anton L., and Zaman, Atiq Uz

Published
2024
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13. The Surgical Algorithm for the AO Spine Sacral Injury Classification System

Author

Lee, Yunsoo, Lambrechts, Mark, Narayanan, Rajkishen, Bransford, Richard, Benneker, Lorin, Schnake, Klaus, Öner, Cumhur, Canseco, Jose A., Kepler, Christopher K., Schroeder, Gregory D., Vaccaro, Alexander R., Hockley, Aaron, Zubairi, Akbar J., Barcelos, Alecio, del Arco, Alex, Weening, Alexander, Guiroy, Alfredo, Guiroy, Alfredo, Wael, Alsammak, Bhandutia, Amit, Nishanth, Ampar, Joaquim, Andrei, Joaquim, Andrei, Persin, Andrew, Gupta, Anuj, El Naga, Ashraf, El Naga, Ashraf, Ullrich, Bernhard, Saciloto, Bruno, Cheng, Christina, Bernucci, Claudio, Kleweno, Conor, Cruz, Daniel, Dizon, Dave A., Aponso, Dihan, Patronis, Dimitrios, Martinez, Elias E.J., Pola, Enrico, Gercek, Erol, Lyons, Frank, Camino-Willhuber, Gaston, Tipper, Geoffrey, Okano, Ichiro, Bances, Ignacio F., Paredes, Igor, Parampalli, Janardhana A., Matta, Javier, Subbiah, Jayakumar, Kitzen, Joep, Alves, Jorge, Montoya, Juan E.M., Lourido, Juan, Scherer, Julian, Zhang, Jun, Nitin, Kimmatkar, Margetis, Konstantinos, Rakesh, Kumar, Vineet, Kumar, Lozano, Lady C, Badalassi, Leandro, Rodríguez, Luis M.D., Kollintzas, Lykourgos, Ito, Manabu, Ganau, Mario, Estefan, Martin, Holas, Martin, Federico, Martinelli, Duarte, Matias P., Pumberger, Matthias, Scholz, Matti, Diez-Ulloa, Maximo-Alberto, Triffaux, Michel, Khattab, Mohamed, El-Sharkawi, Mohammad, Abdelhafez, Mostafa, Sathish, Muthu, Khan, Nasser, Nicola, Nicassio, Brown, Nolan, Neves, Nuno, Morillo, Olga, Alarcon, Olger, Bazán, Pedro, Loughenbury, Peter, Bancel, Philippe, Cezar, Popescu E., Rabindra, Pradhan, Moraes, Psmar, Banerjee, Purnajyoti, Lakhey, Rajesh B., Alessamdro, Ramieri, Yurac, Ratko, Vieira, Rian, Bransford, Richard, Kanna, Rishi M., Alakkad, Salah, Samy, Samer, Bigdon, Sebastian, Zylbersztejn, Sergio, Lang, Siegmund, Hashmi, Sohaib, Darwish, Stacey, Corluka, Stipe, haribabu, Subramaniam M., Karimjee, Taha, Elhewala, Tarek, Martin, Tejeda, Benzakour, Thami, Moore, Tim, Adetunji, Toluse, Torres, Valencia H., Loya, Vijay K., Hamouda, Waeel, Söyüncü, Yetkin, Silk, Zacharia, Slavisa, Zagorac, and Klezl, Zdenek

Published
2024
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14. The Surgical Algorithm for the AO Spine Sacral Injury Classification System

Author

Lee, Yunsoo, Lambrechts, Mark, Narayanan, Rajkishen, Bransford, Richard, Benneker, Lorin, Schnake, Klaus, Öner, Cumhur, Canseco, Jose A., Kepler, Christopher K., Schroeder, Gregory D., Vaccaro, Alexander R., Hockley, Aaron, Zubairi, Akbar Jaleel, Barcelos, Alecio, del Arco, Alex, Weening, Alexander, Guiroy, Alfredo, Guiroy, Alfredo, Wael, Alsammak, Bhandutia, Amit, Nishanth, Ampar, Joaquim, Andrei, Joaquim, Andrei, Persin, Andrew, Gupta, Anuj, El Naga, Ashraf, El Naga, Ashraf, Ullrich, Bernhard, Saciloto, Bruno, Cheng, Christina, Bernucci, Claudio, Kleweno, Conor, Cruz, Daniel, Dizon, Dave Anthony, Aponso, Dihan, Patronis, Dimitrios, Martinez, Elias Enmanuel Javier, Pola, Enrico, Gercek, Erol, Lyons, Frank, Camino-Willhuber, Gaston, Tipper, Geoffrey, Okano, Ichiro, Bances, Ignacio Fernández, Paredes, Igor, Parampalli, Janardhana Aithala, Matta, Javier, Subbiah, Jayakumar, Kitzen, Joep, Alves, Jorge, Montoya, Juan Esteban Muñoz, Lourido, Juan, Scherer, Julian, Zhang, Jun, Nitin, Kimmatkar, Margetis, Konstantinos, Rakesh, Kumar, Vineet, Kumar, Lozano, Lady C, Badalassi, Leandro, Rodríguez, Luis Miguel Duchén, Kollintzas, Lykourgos, Ito, Manabu, Ganau, Mario, Estefan, Martin, Holas, Martin, Federico, Martinelli, Duarte, Matias Pereira, Pumberger, Matthias, Scholz, Matti, Diez-Ulloa, Maximo-Alberto, Triffaux, Michel, Khattab, Mohamed, El-Sharkawi, Mohammad, Abdelhafez, Mostafa, Sathish, Muthu, Khan, Nasser, Nicola, Nicassio, Brown, Nolan, Neves, Nuno, Morillo, Olga, Alarcon, Olger, Bazán, Pedro, Loughenbury, Peter, Bancel, Philippe, Cezar, Popescu Eugen, Rabindra, Pradhan, Moraes, Psmar, Banerjee, Purnajyoti, Lakhey, Rajesh Bahadur, Alessamdro, Ramieri, Yurac, Ratko, Vieira, Rian, Bransford, Richard, Kanna, Rishi M, Alakkad, Salah, Samy, Samer, Bigdon, Sebastian, Zylbersztejn, Sergio, Lang, Siegmund, Hashmi, Sohaib, Darwish, Stacey, Corluka, Stipe, haribabu, Subramaniam Macherla, Karimjee, Taha, Elhewala, Tarek, Martin, Tejeda, Benzakour, Thami, Moore, Tim, Adetunji, Toluse, Torres, Valencia Heiller, Loya, Vijay Kumar, Hamouda, Waeel, Söyüncü, Yetkin, Silk, Zacharia, Slavisa, Zagorac, and Klezl, Zdenek

Published
2023
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15. Scaling Laws for the Few-Shot Adaptation of Pre-trained Image Classifiers

Author

Prato, Gabriele, Guiroy, Simon, Caballero, Ethan, Rish, Irina, and Chandar, Sarath

Subjects
Computer Science - Machine Learning, Computer Science - Artificial Intelligence, Computer Science - Computer Vision and Pattern Recognition
Abstract

Empirical science of neural scaling laws is a rapidly growing area of significant importance to the future of machine learning, particularly in the light of recent breakthroughs achieved by large-scale pre-trained models such as GPT-3, CLIP and DALL-e. Accurately predicting the neural network performance with increasing resources such as data, compute and model size provides a more comprehensive evaluation of different approaches across multiple scales, as opposed to traditional point-wise comparisons of fixed-size models on fixed-size benchmarks, and, most importantly, allows for focus on the best-scaling, and thus most promising in the future, approaches. In this work, we consider a challenging problem of few-shot learning in image classification, especially when the target data distribution in the few-shot phase is different from the source, training, data distribution, in a sense that it includes new image classes not encountered during training. Our current main goal is to investigate how the amount of pre-training data affects the few-shot generalization performance of standard image classifiers. Our key observations are that (1) such performance improvements are well-approximated by power laws (linear log-log plots) as the training set size increases, (2) this applies to both cases of target data coming from either the same or from a different domain (i.e., new classes) as the training data, and (3) few-shot performance on new classes converges at a faster rate than the standard classification performance on previously seen classes. Our findings shed new light on the relationship between scale and generalization.

Published
2021

20. Educational Status of Minimally Invasive Spine Surgery

Author

Bernardo de Andrada Pereira, Kanwaljeet Garg, James Mamaril-Davis, Bipin Chaurasia, Alfredo Guiroy, Jahangir Asghar, Jay D. Turner, and R. John Hurlbert

Subjects
MISS, spine surgery, minimally invasive surgery, cadaver-laboratory, online education, COVID-19, cirurgia de coluna minimamente invasiva, treinamento online, pandemia, cadáver, Medicine, Surgery, RD1-811
Abstract

Introduction The objective of this study was to understand how spine surgeons learn minimally invasive spine surgery (MISS) and how the COVID-19 pandemic impacted the educational experience of MISS. Potential solutions for increasing the spine surgeon's access to MISS educational resources were also discussed.

Published
2024
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21. The impact of stratified hypoalbuminemia and dialysis on morbidity/mortality after posterior spinal fusion surgery: An ACS-NSQIP study

Author

Camino-Willhuber, Gaston, Oyadomari, Sarah, Ochoa, Jonathan, Holc, Fernando, Guiroy, Alfredo, Bow, Hansen, Hashmi, Sohaib, Oh, Michael, Bhatia, Nitin, and Lee, Yu-po

Subjects
Biomedical and Clinical Sciences, Clinical Sciences, Clinical Research, Patient Safety, Good Health and Well Being, Adverse events, Complications, Dialysis, Fusion surgery, Hypoalbuminemia, Mortality, Readmission, Severe hypoalbuminemia, Neurosciences, Clinical sciences, Biological psychology
Abstract

BackgroundPreoperative optimization in patients undergoing posterior spinal fusion is essential to limit the number and severity of postoperative complications. Here, we, additionally, evaluated the impact of hypoalbuminemia on morbidity and mortality after posterior spinal fusion surgery.MethodsThis retrospective analysis was performed using data from a prospective multicentric database (ACSNSQIP:2015-2020) regarding patients undergoing posterior spinal fusions. Factors studied included; baseline demographics and 30-day postoperative complications (i.e., reoperations, readmissions, and mortality rates).ResultsThere were 6805 patients who met the inclusion criteria. They averaged 62 years of age and had an average BMI of 30.2. Within the 30-day postoperative period, 634 (9.3%) sustained complications; 467 (6.9%) were readmitted, 263 (3.9%) required reoperations, and 37 (0.5%) expired. Although multiple preoperative risk factors were analyzed, hypoalbuminemia, severe hypoalbuminemia, and dialysis were the strongest independent risk factors associated with complications (i.e., reoperations, readmissions, and mortality).ConclusionHypoalbuminemia, severe hypoalbuminemia, and dialysis were significant predictors for morbidity and mortality after posterior spinal fusion surgery.

Published
2022

26. Comparison of complication rates between anterior versus posterior approaches for treating unstable Hangman's fracture. A systematic review and meta-analysis

Author

Matias Pereira-Duarte, Martin Gagliardi, Charles André Carazzo, Gaston Camino-Willhuber, Alberto Gotfryd, Michael Rogers, and Alfredo Guiroy

Subjects
Hangman's fracture, Systematic review, Anterior approach, Posterior approach, Complications, C2 traumatic spondylolisthesis, Surgery, RD1-811, Neurology. Diseases of the nervous system, RC346-429
Abstract

Study design: Systematic Review and Meta-analysis. Objective: To compare the complication rates associated with anterior and posterior approaches for the surgical treatment of unstable hangman's fractures. Methods: A systematic review and meta-analysis were performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines in PubMed, Web of Science, and Scopus databases to identify comparative studies reporting complications of anterior versus posterior approaches for the treatment of unstable hangman's fractures. Results: The search yielded 1163 papers from which 5 studies were fully included. One hundred fifteen (115) patients were operated on using an anterior approach versus 65 through a posterior approach. The average complication rates for the anterior and posterior approaches were 26.1 % and 13.8 %, respectively. No complications following the anterior approach required pharmacological or surgical intervention (Clavien-Dindo, Grade 1), while 88.9 % of complications following the posterior approach did (Clavien-Dindo, Grade 2). Conclusion: No significant differences in the complication rates were found when comparing anterior versus posterior surgery for treating a C2 traumatic spondylolisthesis. However, most of the complications presented in the posterior surgery group were more severe.

Published
2024
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28. Towards Understanding Generalization in Gradient-Based Meta-Learning

Author

Guiroy, Simon, Verma, Vikas, and Pal, Christopher

Subjects
Computer Science - Machine Learning, Computer Science - Computer Vision and Pattern Recognition, Statistics - Machine Learning
Abstract

In this work we study generalization of neural networks in gradient-based meta-learning by analyzing various properties of the objective landscapes. We experimentally demonstrate that as meta-training progresses, the meta-test solutions, obtained after adapting the meta-train solution of the model, to new tasks via few steps of gradient-based fine-tuning, become flatter, lower in loss, and further away from the meta-train solution. We also show that those meta-test solutions become flatter even as generalization starts to degrade, thus providing an experimental evidence against the correlation between generalization and flat minima in the paradigm of gradient-based meta-leaning. Furthermore, we provide empirical evidence that generalization to new tasks is correlated with the coherence between their adaptation trajectories in parameter space, measured by the average cosine similarity between task-specific trajectory directions, starting from a same meta-train solution. We also show that coherence of meta-test gradients, measured by the average inner product between the task-specific gradient vectors evaluated at meta-train solution, is also correlated with generalization. Based on these observations, we propose a novel regularizer for MAML and provide experimental evidence for its effectiveness.

Published
2019

31. Correlation Between Cage Positioning and Lumbar Lordosis in Transforaminal Lumbar Interbody Fusion (TLIF)

Author

Emiliano Neves Vialle, Guilherme Zandavalli Ramos, Fabian Lopez Hinojosa, Alfredo Guiroy, Luiz Gustavo Dal'Oglio da Rocha, and André de Oliveira Arruda

Subjects
spondylolisthesis, lordosis, spinal fusion, lumbosacral region, Medicine, Orthopedic surgery, RD701-811
Abstract

Abstract Objective The present study evaluates radiographic outcomes and the lumbar lordosis achieved with a transforaminal lumbar interbody fusion (TLIF) arthrodesis technique according to the positioning of an interbody device (cage) in the disc space. Methods This is a retrospective radiographic analysis of single-level surgical patients with degenerative lumbar disease submitted to a TLIF procedure and posterior pedicle instrumentation. We divided patients into two groups according to cage positioning. For the TLIF-A group, the cages were anterior to the disc space; for the TLIF-P group, cages were posterior to the disc space. Considering the superior vertebral plateau of the lower vertebra included in the instrumentation, cages occupying a surface equal to the anterior 50% of the midline were placed in the TLIF-A group, and those in a posterior position were placed in the TLIF-P group. We assessed pre- and postoperative orthostatic lateral radiographs to obtain the following measures: lumbar lordosis (LL) (angle L1–S1), segmental lordosis (LS) (L4–S1), and segmental lordosis of the cage (SLC). Results The present study included 100 patients from 2011 to 2018; 44 were males, and 46 were females. Their mean age was 50.5 years old (range, 27 to 76 years old). In total, 43 cages were “anterior” (TLIF-A) and 57 were “posterior” (TLIF-P). After surgery, the mean findings for the TLIF-A group were the following: LL, 50.7°, SL 34.9°, and SLC 21.6°; in comparison, the findings for the TLIF-P group were the following: LL, 42.3° (p< 0.01), SL 30.7° (p< 0.05), and SLC 18.8° (p> 0.05). Conclusion Cage positioning anterior to the disc space improved lumbar and segmental lordosis on radiographs compared with a posterior placement.

Published
2022
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32. Risk Factors for Postoperative Complications After Surgical Treatment of Type B and C Injuries of the Thoracolumbar Spine

Author

Zanardi, Carlos, Picard, Nelson, Donato, Maximiliano, Gorgas, Alberto, Peña, Efrén, González, Óscar, Mandiola, Sergio, Remondino, Rodrigo, Ortiz, Pablo Nicolas, Jiménez, José, Jesus Gonzalez, Jose de, Martinez, Oscar, Reyes, Pedro, Jara, Juan, Burgos, Julio, Gagliardi, Martin, Ciancio, Alejandro Morales, Uruchi, Daniel, Martínez, Ricardo, Mireles, Nicolás, Meira, Paulo Henrique, Astur, Nelson, Meves, Robert, Vieira, Rian, Borges, Renan, Chaves, Jennyfer, Guimaraes, Ricardo, Balen, Matheus, Zamorano, Juan J., Zanini, Guilherme Rocha, Senna, Germano, Cabrera, Paulo Roberto, Ordoñez, Fausto, Vásquez, FranlyArismendy, Daniel, Jefferson, Veiga, Jose Carlos, Santoro, Pedro Del, Sebben, Andre Luis, Orso, Vinicius, Penteado, Ricardo, Jr., Pino, Christian, Velarde, Esther, Jacob, Charbel, Jr., Dias, Wanderson, Ujhelly, Jose Ignacio, Estay, Ayelen, Noleto, Gustavo, Sousa, Icaro de, Amorim, Robson, Carneiro, Marlon, Montoya, Fabián, Flórez, David, Corrêa, Raphael Augusto, Santiago, Bastianon, Gonzalez, Alvaro Silva, Cabrera, Juan P., Carazzo, Charles A., Guiroy, Alfredo, White, Kevin P., Guasque, Joana, Sfreddo, Ericson, Joaquim, Andrei F., and Yurac, Ratko

Published
2023
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36. Time to surgery for adolescent idiopathic scoliosis: How long does it take? A multicenter study

Author

Alfredo Guiroy, Charles Carazzo, Gastón Camino-Willhuber, Alejandro Morales Ciancio, Rodrigo Remondino, Fernando Nin, Fernando Alvarado-Gomez, Juan Reviriego, Baron Zarate Kalfopulos, Murilo Daher, Andre Luis Fernandes Andújar, Jahangir Asghar, Fabio Ferri-de-Barros, and Robert Meves

Subjects
Idiopathic scoliosis, Scoliosis surgery, Spinal deformity, Adolescent scoliosis, Idiopathic scoliosis surgery, Scoliosis treatment, Surgery, RD1-811, Neurology. Diseases of the nervous system, RC346-429
Abstract

Study design: Retrospective review of multicentric data. Objectives: To estimate the time from initial visit to surgery in adolescent idiopathic scoliosis (AIS) patients and the main reasons for the time to surgery in a multicenter study. Methods: This retrospective study evaluated 509 patients with AIS from 16 hospitals across six Latin American countries. From each hospital's deformity registry, the following patient data were extracted: demographics, main curve Cobb angle, Lenke Classification at the initial visit and time of surgery, time from indication-for-surgery to surgery, curve progression, Risser skeletal-maturity score and causes for surgical cancelation or delay. Surgeons were asked if they needed to change the original surgical plan due to curve progression. Data also were collected on each hospital's waiting list numbers and mean delay to AIS surgery. Results: 66.8% of the patients waited over six months and 33.9% over a year. Waiting time was not impacted by the patient's age when surgery first became indicated (p = 0.22) but waiting time did differ between countries (p

Published
2023
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41. Why are frailty indices not used systematically during preoperative spine consultations?

Author

Matias Pereira Duarte, Gaston Camino Willhuber, Marcelo Valacco, Asdrubal Falavigna, Jahangir Asghar, and Alfredo Guiroy

Subjects
frailty, spine, latin america, postoperative complications, Medicine, Medicine (General), R5-920
Abstract

Introduction: Frailty indices are highly predictive of major medical and mechanical complications, lengths of hospital stay, and mortality rates after spine procedures. However, several barriers limit the extent to which spine surgeons employ these indices. The main purposes of the current study were to assess the use of frailty indices by Latin-American spine surgeons and identify the main barriers perceived to restrict their clinical application. Methods: For this cross-sectional survey, a questionnaire evaluating the demographic characteristics of participating surgeons and their utilization of frailty indices were created in Google form and sent by e-mail to every registered member of AO Spine Latin America between October and November 2020. Results: Of the 1047 surgeons sent the survey, 293 responded (response rate=28%). Half of the surgeons (51.7%) said they were unfamiliar with the terms ¨frailty´ and ¨frailty index”, while 70.3% claimed not to use any frailty scale during their pre-operative assessments. The most frequently utilized index was the modified Frailty Index (mFI) (18%). The most important perceived barrier was the excessive amount of time required to calculate each patient’s frailty score. Ninety-two percent of the spine surgeons felt sure that these scores could influence their therapeutic decisions, while 91% desired an easier-to-use risk-prevention scale. Conclusion: The main perceived barriers restricting the use of frailty indices were the time required to complete them, lack of index validation, and need for specific instruments to calculate the index score.

Published
2022
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45. Standard dose raltegravir or efavirenz-based antiretroviral treatment for patients co-infected with HIV and tuberculosis (ANRS 12 300 Reflate TB 2): an open-label, non-inferiority, randomised, phase 3 trial

Author

Irmine, Ahyi, Kakou, Aka, Ana cláudia, Alves, Jacqueline, Amani, Bonzou, Amoakon, Xavier, Anglaret, Amani, Anzian, Khalide, Azam, Débora Faber, Barreto, Rui, Bastos dos Santos, Aurélie, Beuscart, Nilesh, Bhatt, Antoine, Bi, Maryline, Bonnet, Kim Nhung, Bui thi, Luiz, Camacho, Tung khanh, Cao, Corine, Chazallon, Lara, Coelho, Mai Luong, Cong thi, Robson Pierre, Da SILVA, Minh Há, Dang thi, Lehi Florence, Dano, Nathalie, De castro, Marie, De Solère, Constance, Delaugerre, Alpha, Diallo, Thanh, Dinh phuong, Donald, Diomandé, Giang, Do cha, Trang, Do ha thanh, Anaïs, Domergue, Trang Quynh Nhu, Dong bui vu hoang, Fulgence, Eboumou, Serge, Eholie, Frederick, Ello, Arlette, Emieme, Rodrigo, Escada, Etienne, Etilé, Salimata, Fanny, Ana cristina, Ferreira, Robert, Gbey, Joachim, Gnokoro, Tatiane, Gomes, Maura lassance, Gonzales, Beatriz, Grinsztejn, Frederique, Guiroy, Thanh Trang Do, Ha, Brenda, Hoagland, Anh Phuong, Huynh, Khanh thu, Huynh hoang, Marcelin, Irié, Jean-claude, Kacou, Samuel, Kan, Sophie, Karcher, Mc, Kassy, Celso, Khosa, Lambert, Konan, Romuald, Konan, Fatoumata, Koné, Suzanne, Kouadio, Martin, Kouamé, Tânia, Krsitic, Georgette, Labibi, Didier, Laureillard, Jérôme, Le Carrou, Khanh, Le Guoc, Ngoc bich, Le Thi, Flávia, Lessa, Van Duong, Long, Anh Que, Luong, Huyen Thi Thu, Mai, Thu Huyen Nguyet, Mai, Emelva, Manhiça, Olivier, Marcy, Luana, Marins, Lectícia, Matsinhe, Hervé, Menan, Eugène, Messou, Jean-michel, Molina, Alice, Montoyo, Ronaldo ismerio, Moreira, Jean-baptiste, N'takpé, Sandro, Nazer, Cao van thi, Nguyen, Nuoi THI, Nguyen, Bang, Nguyen duc, Lân, Nguyen huu, Lan, Nguyen ngoc, Viet, Nguyen nhu, Hong, Nguyen thi, Dilário, Nhumaio, Hang THU, Pham, Anh THI QUYNH, Pham, Diane, Ponscarme, Miresta, Previllon, Cyprien, Rabe, Delphine, Rapoud, Daniel, Rebelo, Claire, Rekacewicz, Valéria rita, Ribeiro, Jorge, Ribeiro, Lucimar, Salgado, Soraia, Santana de MOURA, Desiree, Santos, Yamissa, Siloue, Bertine, Siloue, Nádia, Sitoe, Anne-marie, Taburet, Isabel cristina, Tavares, Ezio, Tavora dos Santos Filho, Cecile, Tchehy, Isabel, Timana, Thomas-d'aquin, Toni, Thiago, Torres, Thao PHAM PHUONG, Tran, Loc HUU, Tran, Quy Thi Kim, Tran, Tien Thi Thuy, Tran, Ton, Tran, Thi Hieu Nhi, Tran, Thi-Hai Ly, Tran, Valdilea, Veloso, Arlindo, Vilanculo, Xuan Thinh, Vu, Adolfo, Vubil, Sandra, Wagner, Alcina, Zitha, Astrid, De Castro, Nathalie, Marcy, Olivier, Chazallon, Corine, Messou, Eugène, Eholié, Serge, N'takpe, Jean-Baptiste, Bhatt, Nilesh, Khosa, Celso, Timana Massango, Isabel, Laureillard, Didier, Chau, Giang Do, Domergue, Anaïs, Veloso, Valdilea, Escada, Rodrigo, Wagner Cardoso, Sandra, Delaugerre, Constance, Anglaret, Xavier, Molina, Jean-Michel, and Grinsztejn, Beatriz

Published
2021
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48. Trends in primary percutaneous coronary intervention for the treatment of acute coronary ST-elevation myocardial infarction in Latin American countries: insights from the CECI consortium.

Author

Matías Rodriguez-Granillo, Alfredo, Solórzano, Leonardo, Vladimir Pérez-Omaña, Gilberto, Ascarrunz, Diego, Pavlovsky, Hernán, Gomez-Valerio, Reynaldo, Bertrán, Ignacio, Flores, Federico, Parra, Julio, Guiroy, Juan, Mieres, Juan, Carvajal, Francisco, Fernández-Pereira, Carlos, RodriguezMieres, Alfredo E., and Rodriguez, Alfredo E.

Published
2024
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