{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,31]],"date-time":"2026-07-31T05:53:59Z","timestamp":1785477239655,"version":"3.56.0"},"reference-count":63,"publisher":"SAGE Publications","issue":"8","license":[{"start":{"date-parts":[[2021,12,27]],"date-time":"2021-12-27T00:00:00Z","timestamp":1640563200000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"content-domain":{"domain":["journals.sagepub.com"],"crossmark-restriction":true},"short-container-title":["Global Spine Journal"],"published-print":{"date-parts":[[2022,10]]},"abstract":"<jats:sec>\n                    <jats:title>Study Design<\/jats:title>\n                    <jats:p>Literature review.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>To describe whether practice variation studies on surgery in patients with lumbar degenerative disc disease used adequate study methodology to identify unwarranted variation, and to inform quality improvement in clinical practice. Secondary aim was to describe whether variation changed over time.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      Literature databases were searched up to May 4\n                      <jats:sup>th<\/jats:sup>\n                      , 2021. To define whether study design was appropriate to identify unwarranted variation, we extracted data on level of aggregation, study population, and case-mix correction. To define whether studies were appropriate to achieve quality improvement, data were extracted on outcomes, explanatory variables, description of scientific basis, and given recommendations. Spearman\u2019s rho was used to determine the association between the Extreme Quotient (EQ) and year of publication.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>We identified 34 articles published between 1990 and 2020. Twenty-six articles (76%) defined the diagnosis. Prior surgery cases were excluded or adjusted for in 5 articles (15%). Twenty-three articles (68%) adjusted for case-mix. Variation in outcomes was analyzed in 7 articles (21%). Fourteen articles (41%) identified explanatory variables. Twenty-six articles (76%) described the evidence on effectiveness. Recommendations for clinical practice were given in 9 articles (26%). Extreme Quotients ranged between 1-fold and 15-fold variation and did not show a significant change over time (rho= \u2212.33, P= .09).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Practice variation research on surgery in patients with degenerative disc disease showed important limitations to identify unwarranted variation and to achieve quality improvement by public reporting. Despite the availability of new evidence, we could not observe a significant decrease in variation over time.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1177\/21925682211064855","type":"journal-article","created":{"date-parts":[[2021,12,27]],"date-time":"2021-12-27T03:58:02Z","timestamp":1640577482000},"page":"1841-1851","update-policy":"https:\/\/doi.org\/10.1177\/sage-journals-update-policy","source":"Crossref","is-referenced-by-count":3,"title":["Practice Variation Research in Degenerative Lumbar Disc Surgery: A Literature Review on Design Characteristics and Outcomes"],"prefix":"10.1177","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1670-1800","authenticated-orcid":false,"given":"Juli\u00ebtte J. C. M.","family":"Van Munster","sequence":"first","affiliation":[{"name":"Leiden University Medical Center (LUMC), Leiden, Netherlands"},{"name":"University Neurosurgical Center Holland, Leiden University Medical Center, the Hague Medical Center, and Haga Teaching Hospitals, Leiden and the Hague, the Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Vera","family":"de Weerdt","sequence":"additional","affiliation":[{"name":"Talma Institution, Vrije Universiteit Amsterdam, the Netherlands & Amsterdam University Medical Centers, Amsterdam, the Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ilan J. Y.","family":"Halperin","sequence":"additional","affiliation":[{"name":"Leiden University Medical Center (LUMC), Leiden, Netherlands"},{"name":"University Neurosurgical Center Holland, Leiden University Medical Center, the Hague Medical Center, and Haga Teaching Hospitals, Leiden and the Hague, the Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Amir H.","family":"Zamanipoor Najafabadi","sequence":"additional","affiliation":[{"name":"University Neurosurgical Center Holland, Leiden University Medical Center, the Hague Medical Center, and Haga Teaching Hospitals, Leiden and the Hague, the Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Peter Paul G.","family":"van Benthem","sequence":"additional","affiliation":[{"name":"Leiden University Medical Center (LUMC), Leiden, Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Guus G.","family":"Schoonman","sequence":"additional","affiliation":[{"name":"Elisabeth-TweeSteden Hospital, Tilburg, the Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wouter A.","family":"Moojen","sequence":"additional","affiliation":[{"name":"University Neurosurgical Center Holland, Leiden University Medical Center, the Hague Medical Center, and Haga Teaching Hospitals, Leiden and the Hague, the Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wilbert B.","family":"van den Hout","sequence":"additional","affiliation":[{"name":"Leiden University Medical Center, the Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Femke","family":"Atsma","sequence":"additional","affiliation":[{"name":"Radboud University Medical Center\/Radboud Institute for Health Sciences\/Scientific Center for Quality of Healthcare (IQ healthcare), Nijmegen, the Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wilco C.","family":"Peul","sequence":"additional","affiliation":[{"name":"University Neurosurgical Center Holland, Leiden University Medical Center, the Hague Medical Center, and Haga Teaching Hospitals, Leiden and the Hague, the Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"179","published-online":{"date-parts":[[2021,12,27]]},"reference":[{"key":"bibr1-21925682211064855","doi-asserted-by":"publisher","DOI":"10.1097\/BRS.0b013e3181e70488"},{"key":"bibr2-21925682211064855","volume-title":"Healthcare Cost and Utilization Project (HCUP) Statistical Briefs","author":"Torio CM","year":"2006"},{"key":"bibr3-21925682211064855","doi-asserted-by":"publisher","DOI":"10.1136\/bmj.39223.428495"},{"key":"bibr4-21925682211064855","doi-asserted-by":"publisher","DOI":"10.1056\/nejm193408022110506"},{"key":"bibr5-21925682211064855","first-page":"1118","volume":"2011","author":"Jordan 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