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The objective was to test the inter- and intra-rater reliability of an MRI-based classification for RNR.<\/jats:p>\n<\/jats:sec><jats:sec>\n<jats:title>Methods<\/jats:title>\n<jats:p>This is a retrospective reliability study. A neuroradiologist, an orthopedic surgeon, a neurosurgeon, and three orthopedic surgeons in-training classified RNR on 126 preoperative MRIs of patients with LSS admitted for microsurgical decompression. On sagittal and axial T2-weighted images, the following four categories were classified: allocation (A) of the key stenotic level, shape (S), extension (E), and direction (D) of the RNR. A second read with cases ordered differently was performed 4\u00a0weeks later. Fleiss and Cohen\u2019s kappa procedures were used to determine reliability.<\/jats:p>\n<\/jats:sec><jats:sec>\n<jats:title>Results<\/jats:title>\n<jats:p>The allocation, shape, extension, and direction (ASED) classification showed moderate to almost perfect inter-rater reliability, with kappa values (95% CI) of 0.86 (0.83, 0.90), 0.62 (0.57, 0.66), 0.56 (0.51, 0.60), and 0.66 (0.63, 0.70) for allocation, shape, extension, and direction, respectively. Intra-rater reliability was almost perfect, with kappa values of 0.90 (0.88, 0.92), 0.86 (0.84, 0.88), and 0.84 (0.81, 0.87) for shape, extension, and direction, respectively. Intra-rater kappa values were similar for junior and senior raters. Kappa values for inter-rater reliability were similar between the first and second reads (<jats:italic>p<\/jats:italic>\u00a0=\u20090.06) among junior raters and improved among senior raters (<jats:italic>p<\/jats:italic>\u00a0=\u20090.008).<\/jats:p>\n<\/jats:sec><jats:sec>\n<jats:title>Conclusions<\/jats:title>\n<jats:p>The MRI-based classification of RNR showed moderate-to-almost perfect inter-rater and almost perfect intra-rater reliability.<\/jats:p>\n<\/jats:sec>","DOI":"10.1007\/s00234-019-02337-3","type":"journal-article","created":{"date-parts":[[2019,12,14]],"date-time":"2019-12-14T11:17:16Z","timestamp":1576322236000},"page":"223-230","update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":14,"title":["Redundant nerve roots in lumbar spinal stenosis: inter- and intra-rater reliability of an MRI-based classification"],"prefix":"10.1007","volume":"62","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3664-8736","authenticated-orcid":false,"given":"Luca","family":"Papavero","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3216-6382","authenticated-orcid":false,"given":"Carlos J.","family":"Marques","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jens","family":"Lohmann","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thies","family":"Fitting","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kathrin","family":"Schawjinski","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nawar","family":"Ali","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9900-0072","authenticated-orcid":false,"given":"Hauke","family":"Hillebrand","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rainer","family":"Maas","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2019,12,14]]},"reference":[{"issue":"7","key":"2337_CR1","doi-asserted-by":"publisher","first-page":"625","DOI":"10.1016\/j.spinee.2010.05.006","volume":"10","author":"RA Deyo","year":"2010","unstructured":"Deyo RA (2010) Treatment of lumbar spinal stenosis: a balancing act. 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