{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,17]],"date-time":"2026-10-17T06:49:21Z","timestamp":1792219761895,"version":"4.4.0"},"reference-count":41,"publisher":"SAGE Publications","issue":"4","license":[{"start":{"date-parts":[[2024,2,11]],"date-time":"2024-02-11T00:00:00Z","timestamp":1707609600000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.sagepub.com\/page\/policies\/text-and-data-mining-license"}],"content-domain":{"domain":["journals.sagepub.com"],"crossmark-restriction":true},"short-container-title":["Am J Sports Med"],"published-print":{"date-parts":[[2024,3]]},"abstract":"<jats:sec>\n                    <jats:title>Background:<\/jats:title>\n                    <jats:p>Most clinical machine learning applications use a supervised learning approach using labeled variables. In contrast, unsupervised learning enables pattern detection without a prespecified outcome.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Purpose\/Hypothesis:<\/jats:title>\n                    <jats:p>The purpose of this study was to apply unsupervised learning to the combined Danish and Norwegian knee ligament register (KLR) with the goal of detecting distinct subgroups. It was hypothesized that resulting groups would have differing rates of subsequent anterior cruciate ligament reconstruction (ACLR) revision.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Study Design:<\/jats:title>\n                    <jats:p>Cohort study; Level of evidence, 3.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods:<\/jats:title>\n                    <jats:p>K-prototypes clustering was performed on the complete case KLR data. After performing the unsupervised learning analysis, the authors defined clinically relevant characteristics of each cluster using variable summaries, surgeons\u2019 domain knowledge, and Shapley Additive exPlanations analysis.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results:<\/jats:title>\n                    <jats:p>Five clusters were identified. Cluster 1 (revision rate, 9.9%) patients were young (mean age, 22 years; SD, 6 years), received hamstring tendon (HT) autograft (91%), and had lower baseline Knee injury and Osteoarthritis Outcome Score (KOOS) Sport and Recreation (Sports) scores (mean, 25.0; SD, 15.6). Cluster 2 (revision rate, 6.9%) patients received HT autograft (89%) and had higher baseline KOOS Sports scores (mean, 67.2; SD, 16.5). Cluster 3 (revision rate, 4.7%) patients received bone\u2013patellar tendon\u2013bone (BPTB) or quadriceps tendon (QT) autograft (94%) and had higher baseline KOOS Sports scores (mean, 65.8; SD, 16.4). Cluster 4 (revision rate, 4.1%) patients received BPTB or QT autograft (88%) and had low baseline KOOS Sports scores (mean, 20.5; SD, 14.0). Cluster 5 (revision rate, 3.1%) patients were older (mean age, 42 years; SD, 7 years), received HT autograft (89%), and had low baseline KOOS Sports scores (mean, 23.4; SD, 17.6).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion:<\/jats:title>\n                    <jats:p>Unsupervised learning identified 5 distinct KLR patient subgroups and each grouping was associated with a unique ACLR revision rate. Patients can be approximately classified into 1 of the 5 clusters based on only 3 variables: age, graft choice (HT, BPTB, or QT autograft), and preoperative KOOS Sports subscale score. If externally validated, the resulting groupings may enable quick risk stratification for future patients undergoing ACLR in the clinical setting. Patients in cluster 1 are considered high risk (9.9%), cluster 2 patients medium risk (6.9%), and patients in clusters 3 to 5 low risk (3.1%-4.7%) for revision ACLR.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1177\/03635465231225215","type":"journal-article","created":{"date-parts":[[2024,2,12]],"date-time":"2024-02-12T02:36:16Z","timestamp":1707705376000},"page":"881-891","update-policy":"https:\/\/doi.org\/10.1177\/sage-journals-update-policy","source":"Crossref","is-referenced-by-count":12,"title":["Unsupervised Machine Learning of the Combined Danish and Norwegian Knee Ligament Registers: Identification of 5 Distinct Patient Groups With Differing ACL Revision Rates"],"prefix":"10.1177","volume":"52","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9918-0264","authenticated-orcid":false,"given":"R. Kyle","family":"Martin","sequence":"first","affiliation":[{"name":"Department of Orthopedic Surgery, University of Minnesota, Minneapolis, Minnesota, USA"},{"name":"Department of Orthopedic Surgery, CentraCare, Saint Cloud, Minnesota, USA"},{"name":"Oslo Sport Trauma Research Center, Norwegian School of Sports Science, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Solvejg","family":"Wastvedt","sequence":"additional","affiliation":[{"name":"Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, Minnesota, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ayoosh","family":"Pareek","sequence":"additional","affiliation":[{"name":"Department of Orthopedic Surgery, Hospital for Special Surgery, New York, New York, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andreas","family":"Persson","sequence":"additional","affiliation":[{"name":"Oslo Sport Trauma Research Center, Norwegian School of Sports Science, Oslo, Norway"},{"name":"Orthopaedic Clinic, Oslo University Hospital Ullev\u00e5l, Oslo, Norway"},{"name":"Norwegian Knee Ligament Register, Haukeland University Hospital, Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"H\u00e5vard","family":"Visnes","sequence":"additional","affiliation":[{"name":"Oslo Sport Trauma Research Center, Norwegian School of Sports Science, Oslo, Norway"},{"name":"Norwegian Knee Ligament Register, Haukeland University Hospital, Bergen, Norway"},{"name":"Department of Orthopedics, Sorlandet Hospital, Kristiansand, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anne Marie","family":"Fenstad","sequence":"additional","affiliation":[{"name":"Norwegian Knee Ligament Register, Haukeland University Hospital, Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gilbert","family":"Moatshe","sequence":"additional","affiliation":[{"name":"Oslo Sport Trauma Research Center, Norwegian School of Sports Science, Oslo, Norway"},{"name":"Orthopaedic Clinic, Oslo University Hospital Ullev\u00e5l, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Julian","family":"Wolfson","sequence":"additional","affiliation":[{"name":"Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, Minnesota, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Martin","family":"Lind","sequence":"additional","affiliation":[{"name":"Aarhus University Hospital, Aarhus, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2294-921X","authenticated-orcid":false,"given":"Lars","family":"Engebretsen","sequence":"additional","affiliation":[{"name":"Oslo Sport Trauma Research Center, Norwegian School of Sports Science, Oslo, Norway"},{"name":"Orthopaedic Clinic, Oslo University Hospital Ullev\u00e5l, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"179","published-online":{"date-parts":[[2024,2,11]]},"reference":[{"key":"e_1_3_2_2_2","doi-asserted-by":"publisher","DOI":"10.1177\/0363546514552788"},{"key":"e_1_3_2_3_2","doi-asserted-by":"publisher","DOI":"10.1136\/annrheumdis-2021-221763"},{"key":"e_1_3_2_4_2","doi-asserted-by":"publisher","DOI":"10.1007\/s00167-019-05798-4"},{"key":"e_1_3_2_5_2","first-page":"785","volume-title":"Proceedings of the 22nd ACM SIGKDD International Conference on Knowledge Discovery and Data Mining","volume":"2016","author":"Chen T","unstructured":"Chen T, Guestrin C. 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