Usefulness of K-line in predicting prognosis of laminoplasty for cervical spondylotic myelopathy

Usefulness of K-line in predicting prognosis of laminoplasty for cervical spondylotic myelopathy | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research article Usefulness of K-line in predicting prognosis of laminoplasty for cervical spondylotic myelopathy Terumasa Ikeda, Hiroshi Miyamto, Masao Akagi This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-42579/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 11 Feb, 2023 Read the published version in BMC Musculoskeletal Disorders → Version 1 posted 7 You are reading this latest preprint version Abstract Background: K-line is widely recognized as a useful index to evaluate alignment and size of the cervical ossification of the posterior longitudinal ligament (OPLL) in one parameter. The purpose of this study was to investigate that K-line could be a tool to predict the prognosis of LP for cervical spondylotic myelopathy (CSM) as well. Methods: Sixty-eight patients who underwent LP were enrolled. C2-7 angle, local kyphosis angle, and K-line which is the straight line connecting the midpoints of the spinal canal at C2 and C7 was evaluated on T2- weighted sagittal magnetic resonance imaging (MRI). The JOA score and the recovery rate of the JOA score were evaluated at pre-operation and at follow-up. C2/C7 angle, local kyphosis angle, the JOA score, and the recovery rate were compared between K-line (-) and K-line (+) groups. Results: The recovery rate of K-line (+) group (50.6%) was significantly better than that of K-line (-) (19.4%). In K-line (-), the disc type in which the protruded disc was absorbed during the follow-up showed statistically better recovery rate (27.6%) at follow-up compared to other K-line (-) in which anterior cord compression due to the osteophyte or the kyphotic beak was not absorbed (osseous type, 5.0%). Conclusion: The present study has indicated that K-line can be a factor to predict the clinical outcome of LP for CSM. In K-line (-), the disc type showed somewhat better outcomes compared to the osseous type. However, the results were not sufficient. Orthopedics Orthopedic Surgery cervical spondylotic myelopathy K-line cervical spinal kyphosis Figures Figure 1 Figure 2 Figure 3 Background Laminoplasty (LP) is occasionally indicated for cervical myelopathy caused by a narrow spinal canal due to spondylosis and/or ossification of the posterior longitudinal ligament (OPLL). This procedure enables sufficient decompression in multi-segmental stenotic myelopathy. The effects of decompression with LP are attributed to two mechanisms, i.e., direct posterior decompression and posterior shifting of the spinal cord from anterior compressive lesions [ 1 – 3 ]. However, a large anterior bulge, as with a protruded disc or OPLL, often worsens the postoperative neurological recovery rate after LP [ 4 – 6 ]. Cervical kyphosis may also lead to poor surgical outcomes by interfering with posterior shifting of the spinal cord [ 3 , 8 ]. Iwasaki et al. [ 4 ] reported that the neurologic outcome of LP for cervical OPLL was poor or fair in patients with occupying ratio greater than 60%, hill-shaped ossification, and postoperative kyphotic change in cervical alignment. Fujiyoshi et al. [ 7 ] developed the K-line, a straight line connecting the midpoints of the spinal canal at C2 and C7 on plain lateral radiograph, as a new index to evaluate cervical alignment and OPLL size in one parameter, i.e., OPLL did not exceed the K-line in the K-line (+) group and did exceed the K-line in the K-line (-) group. With regard to cervical spondylotic myelopathy (CSM), Suda et al. [ 8 ] reported that the patients with local kyphosis ≧ 13 degrees exhibited poorer clinical outcomes than those without kyphosis due to the mechanisms described above. On the other hand, Chiba et al. [ 9 ] reported that several patients accompanying by cervical kyphosis obtained an acceptable clinical outcome after LP alone, probably because of the slackening of the spinal cord due to reduced multilevel disc height, which would not be compatible with cervical OPLL. Therefore, usefulness of K-line for CSM was uncertain. The purpose of the present study was to investigate whether K-line can provide a predictor of the clinical outcomes of LP for CSM. Methods Participants in the present study comprised Sixty-eight patients who underwent LP as decompression surgery for CSM were involved in the present study. Exclusion criteria were myelopathy caused by single-level disc herniation, OPLL, or a history of cervical spinal surgery, spinal tumor, trauma, and infection. As the ethics approval, the study protocol was approved by the Institutional Review Board of Kindai University Hospital ( Control Cohort Study, No.2020-025). We conducted this study under approval of the institutional review board and informed consent was obtained from all patients. The operative technique was previously described by Miyazaki and Kirita’s method (n = 64) and a modification of Kurokawa’s method (n = 4). The method of Miyazaki and Kirita was a procedure in which bilateral gutters were made and the laminae were split in the middle with a high-speed drill. The laminae were kept open with nylon sutures in the deep fascia bilaterally. The modification of Kurokawa’s method was the procedure in which mid-splitting of the spinous processes was performed using a T-saw [ 10 ]. After spreading the split spinous processes, hydroxyappatite spacers were sutured as necessary between the opened spinous process at each level. We were able to obtain follow-up results for all 68 patients (50 males and 18 females). Mean age at surgery was 60.3 years (range, 32–92 years). All patients were followed-up for 2 year or longer after surgery. Mean follow-up period was 74.2 months (Table 1 ). The spinal levels of decompression were from C3 to C7 in 47 patients, C4 to C7 in 4 patients, C3 to C6 in 8 patients, C3 to Th1 and C2 to C7 in 3 patients each, and C4 to C5, C3 to C5 and C4 to Th1 in 1 patient each. Table 1 Background characteristics of the participants Characteristic Age (years old) 60.3 ± 12.4 Sex (male/female) 50 / 18 Follow-up period (months) 74 ± 43.5 The JOA score at preoperation (points) 9.7 ± 2.9 The JOA score at follow-up (points) 13.0 ± 2.6 The RR (%) of the JOA score 45.5 ± 28.0 C2-7 angle at preoperation (degrees) 4.1 ± 12.5 C2-7 angle at follow-up (degrees) 6.6 ± 14.3 Data are presented as means ± SD. JOA: Japanese Orthopaedic Association RR: recovery rate Clinical Findings The Japanese Orthopaedic Association (JOA) scoring system was used to evaluate the severity of cervical myelopathy preoperativly and at the final follow-up. The recovery rate (RR) of the JOA score was calculated using the method of Hirabayashi et al. to compare preoperatively and at final follow-up JOA scores. As defined by Hirabayashi et al., RR (%) was calculated as (postoperative JOA score – preoperative JOA score) / (17- preoperative JOA score) × 100. Radiological Evaluation C2-7 angle was measured on T2-weighted sagittal images of magnetic resonance imaging (MRI) preoperatively and at the final follow-up. In CSM patients, although C2-7 angle was positive, local kyphosis existed due to the alignment (e.g., sigmoid, reverse sigmoid, and kyphosis) in several patients. In those cases, local kyphosis angle was also measured on T2-weighted sagittal images of MRI at preoperatively and at the follow-up. The K-line was defined as the straight line connecting the midpoints of the spinal canal at C2 and C7 on midsagittal T2-weighted MRI in the present study. The patients were divided into two groups; K-line (-) and K-line (+). In the K-line (-) group, the anterior structural factors (e.,g., disc herniation, osteophyte, or kyphotic beak of the vertebra) crossed the K-line with no space between the K-line and the anterior wall of the canal. On the other hand, in the K-line (+) group, the anterior structural factors did not exceed K-line and stayed within the ventral area of K-line. Clinical parameters such as gender, age, preoperative JOA score, the JOA score at the follow-up, the RR of the JOA score, and radiological parameters such as preoperative C2-7 angle, C2-7 angle at the follow-up, preoperative local kyphosis angle, and the local kyphosis angle at the follow-up were compared between K-line(-) and K-line (+). Statistical analysis was performed using Student t-test and Mann-Whitney U test, with P < 0.05 considered statistically significant. Statistical analyses of data were performed with Stat Flex Ver.6 (Artech Co., Ltd., Osaka, Japan). Results were presented as means ± SD. Results The mean JOA score was 9.7 points (range, 1–14 points) before surgery and 13.1 points (range, 1–17 points) at final follow-up. The Mean RR of the JOA score was 45.5%. The C2-7 angles at preoperatively and at follow-up were 4.1 ± 12.5 and 6.6 ± 14.3 degrees respectively (Table 1 ). K-line (-) were 11 patients (8 male, 3 females; mean of 57.2 years old), and K-line (+) were 57 patients (42 male, 15 females; mean of 60.9 years old). The JOA score at preoperatively and at follow-up were 10.1 ± 4.1 and 11.6 ± 4.1 in K-line (-) and 9.7 ± 2.6 and 13.3 ± 2.2 in K-line (+). The mean RR of JOA score were 19.4% in K-line (-) and 50.6% in K-line (+) group, representing a significant difference. With respect to radiological findings, preoperative C2-7 angle was significantly smaller in the K-line (-) group (-10.1 ± 9.0 degrees) than in the K-line (+) group (6.8 ± 11.2 degrees). The C2-7 angle at follow-up was significantly smaller in the K-line (-) group (-11.8 ± 10.4 degrees) than in the K-line (+) group (10.2 ± 12.1 degrees). Preoperative local kyphosis angle was significantly larger in the K-line (-) group (16.6 ± 10.0 degrees) than in the K-line (+) group (1.6 ± 3.1 degrees). Local kyphosis angle at follow-up was significantly larger in the K-line (-) group (14.7 ± 7.6 degrees) than in the K-line (+) group (1.3 ± 3.1 degrees) (Table 2 ). Table 2 Comparison between K-line (-) and K-line (+) K-line(-) K-line(+) p Numbers of the patients 11 57 Age (years old) 57.2 ± 17.5 60.9 ± 11.0 NS The JOA score at preoperation (points) 10.1 ± 4.3 9.7 ± 2.6 NS The JOA score at follow-up (points) 11.6 ± 4.1 13.3 ± 2.2 < 0.01 The RR of the JOA score (%) 19.4 ± 25.2 50.6 ± 25.8 < 0.01 C2-7angle at preoperation (degrees) -10.1 ± 9.0 6.8 ± 11.2 < 0.01 C2-7angle at follow-up (degrees) -11.8 ± 10.4 10.2 ± 12.1 < 0.01 Local kyphosis angle at preoperation (degree) 16.6 ± 10.0 1.6 ± 3.1 < 0.01 Local kyphosis angle at follow-up (degree) 14.7 ± 7.6 1.3 ± 3.1 < 0.01 Data are presented as means ± SD. JOA: Japanese Orthopaedic Association RR: recovery rate With follow-up, we found that 7 cases of preoperative K-line (-) changed to K-line (+) because of absorption of the protruded disc (disc type; Fig. 1 ). On the other hand, 4 cases of preoperative K-line (-) due to the osteophyte or the beak of local kyphosis still stayed as K-line (-) at follow-up (osseous type; Fig. 2 ). We compared the clinical data between disc type (Fig. 3 ) and osseous type as shown in Table 3 . Mean RR in the K-line (-) group classified as disc type was 27.6% at follow-up (Fig. 3 ). On the other hand, mean RR in the K-line (-) group classified as osseous type was only 5.0% (Fig. 2 ). This difference was statistically significant. Table 3 Characteristics of K-line (-) patients by types Disc type Osseous type p Number 7 4 Age (yr) 57.4 ± 15.1 56.8 ± 23.9 NS Pre-JOA (points) 11.1 ± 3.1 8.1 ± 5.8 NS FU-JOA (points) 13.4 ± 1.6 8.6 ± 5.8 NS RR of JOA (%) 27.6 ± 28.1 5.0 ± 10.0 < 0.05 Pre-MRI C2-7angle (degrees) -6.0 ± 7.4 -17.3 ± 7.1 < 0.05 Fu-MRI C2-7angle (degrees) -6.7 ± 4.5 -20.8 ± 12.3 < 0.05 Data are presented as means ± SD. JOA: Japanese Orthopaedic Association RR: recovery rate Discussion Surgical outcomes for CSM accompanying local kyphosis have generally been reported as less than acceptable. Baba et al. [ 11 ] reported that patients with preoperative kyphosis (mean angle of 11.7°) show significantly poorer neurological improvement. Suda et al. [ 8 ] also reported that outcomes of LP for CSM accompanying local kyphosis with an angle exceeding 13 degrees (when coexisted with myelomalacia) and 5 degrees (without myelomalacia) were poorer than those for CSM without local kyphosis in their multivariate logistic regression analysis. In contrast, Kaptain et al. [ 12 ] and Uchida et al. [ 13 ] have shown that surgical outcomes were not correlated with preoperative cervical kyphosis. We speculated that their conclusion might have been due to the kyphosis in their patients being mild. Kasai and Uchida reported that the presence or absence of anterior or posterior subarachnoid space of the spinal cord in postoperative MRI correlated significantly with clinical outcome of LP [ 14 ]. The present study has indicated that K-line can be a factor to predict the clinical outcome of LP for CSM. That is, cases preoperatively defined as K-line (-) displayed poorer clinical outcome after LP compared to those defined K-line (+). In particular, this is the first report to show that the disc type for preoperative K-line (-), in which disc was absorbed during the follow-up and the classification changed into K-line (+) at follow-up, achieved better clinical outcomes compared to patients showing the osseous type. However, outcome for disc type were worse than those of K-line (+). Moreover, predicting whether the bulging disc will be resorbed after surgery in not currently possible. Miyamoto et al. [ 15 ] reported that posterior correction surgery for patients with CSM accompanied by local kyphosis resulted in a better clinical outcome than LP alone. Therefore, posterior correction surgery combined with LP should thus be considered for CSM in K-line (-) patients. Conclusion The present study has indicated that K-line can be a factor to predict the clinical outcome of LP for CSM. In K-line (-), the disc type showed somewhat better outcomes compared to the osseous type. However, the results were not sufficient. Therefore, posterior correction surgery combined with LP should be considered for CSM with K-line(-). Abbreviations LP: Laminoplasty; OPLL: posterior longitudinal ligament; CSM: cervical spondylotic myelopathy; JOA: The Japanese Orthopaedic Association; RR: recovery rate Declarations Availability of data and materials The study was analyzed using data obtained from patients who provided informed consent. Ethics approval and consent to participate The study protocol was approved by the Institutional Review Board of Kindai University Hospital ( Control Cohort Study, No.2020-025). We conducted this study under approval of the institutional review board and informed consent was obtained from all patients. This study does not include patients under 18 years of age. Consent for publication Not applicable Competing interests The Authors declare that they have no competing interests. Funding The authoers declealre no potential conflict interest concerning this study. Authors’ contributions TI collected the datas and interpreted, and wrote the manuscript. HM,MA contributed to design of the work and revised the manuscript critically for important content. All authors read and approved the final manuscript. Acknowledgments The authors would like to thank Dr. Koichiro Maeno for his help in collecting clinical data. References Hirabayashi K, Satomi K. Operative procedure and result of expansive open-door laminoplasty. Spine. 1988;13(7):870–6. Hirabayashi K, Watanabe K, Wakano N, Suzuki N, Satomi K, Ishii Y. Expansive open-door laminoplasty for cervical spinal stenotic myelopathy. Spine. 1983;8(7):693–9. Sodeyama T, Goto S, Mochizuki M, Takahashi J, Moriya H. Effect of decompression enlargement laminoplasty for posterior shifting of the spinal cord. Spine (Phila pa 1976). 1999;24(15):1527–31. Iwasaki M, Okuda S, Miyauchi A, Sakaura H, Mukai Y, Yonenobu K, Yoshikawa H. Surgical strategy for cervical myelopathy due to ossification of the posterior longitudinal ligament: Part 1: Clinical results and limitations of laminoplasty. Spine. 2007;32(6):647–53. Yamazaki A, Homma T, Uchiyama S, Katsumi Y, Okumura H. Morphologic limitations of posterior decompression by midsagittal splitting method for myelopathy caused by ossification of the posterior longitudinal ligament in the cervical spine. Spine. 1999;24(1):32–4. Baba H, Uchida K, Maezawa Y, Furusawa N, Azuchi M, Imura S. Lordotic alignment and posterior migration of the spinal cord following en bloc open-door laminoplasty for cervical myelopathy: a magnetic resonance imaging study. J Neurol. 1996;243(9):626–32. Fujiyoshi T, Yamazaki M, Kawabe J, Endou T, Furuya T, Koda M, Okawa A, Takahashi K, Konishi H. A new concept for making decisions regarding the surgical approach for cervical ossification of the posterior longitudinal ligament: the K-line. Spine. 2008;33(26):E990–3. Suda K, Abumi K, Ito M, Shono Y, Kaneda K, Fujiya M. Local kyphosis reduces surgical outcomes of expansive open-door laminoplasty for cervical spondylotic myelopathy. Spine. 2003;28(12):1258–62. Chiba K, Toyama Y, Watanabe M, Maruiwa H, Matsumoto M, Hirabayashi K. Impact of longitudinal distance of the cervical spine on the results of expansive open-door laminoplasty. Spine. 2000;25(22):2893–8. Tomita K, Kawahara N, Toribatake Y, Heller JG. (1998) Expansive midline T-saw laminoplasty (modified spinous process-splitting) for the management of cervical myelopathy. Spine Jan 1;23(1):32–37. Baba H, Maezawa Y, Furusawa N, imura S, Tomita K. Flexibility and alignment of the cervical spine after laminoplasty for spondylotic myelopathy. A radiographic study. Int orthop. 1995;19(2):116–21. Kaptain GJ, Simmons NE, Replogle RE, Pobereskin L. Incidence and outcome of kyphotic deformity following laminectomy for cervical spondylotic myelopathy. J Neurosurg. 2000;93(2 suppl):199–204. Uchida K, Nakajima H, Sato R, Yayama T, Mwaka ES, Kobayashi S, Baba H. Cervical spondylotic myelopathy associated with kyphosis or sagittal sigmoid aliment: outocome after anterior or posterior decompression. J neurosug Spine. 2009;11(5):521–8. Kasai Y, Uchida A. New evaluation method using preoperative magnetic resonance imaging for cervical spondylotic myelopathy. Arch Orthop Trauma Surg. 2001;Oct(9):508–10. 121(. Miyamoto H, Maeno K, Uno K, Kakutani K, Nishida K, Sumi M. Outcomes of surgical intervention for cervical spondylotic myelopathy accompanying local kyphosis (comparison between laminoplasty alone and posterior reconstruction surgery using the screw-rod system). Eur Spine J. 2014;23(2):341–34. Cite Share Download PDF Status: Published Journal Publication published 11 Feb, 2023 Read the published version in BMC Musculoskeletal Disorders → Version 1 posted Reviewers agreed at journal 21 Jul, 2022 Editorial decision: Reject after review 08 Oct, 2020 Reviewers invited by journal 24 Aug, 2020 Editor assigned by journal 17 Jul, 2020 First submitted to journal 16 Jul, 2020 Submission checks completed at journal 16 Jul, 2020 Editor invited by journal 16 Jul, 2020 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-42579","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research article","associatedPublications":[],"authors":[{"id":934040,"identity":"249999ec-f535-4068-af2a-15d84bc089eb","order_by":0,"name":"Terumasa Ikeda","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAElEQVRIiWNgGAWjYDACZjYGBh4GGyArgZkhgYGZgQ0szINbBw9ESxopWhjAWg5DtAAtJewue3a2xAdvas5H87MnMBs83GEtz8fA/PADg8wdfA47bDjn2O3cmT0PmBMSz6QbtjGwGUsw8DzDo4W9TZqH7XbuhhsJzAcS2w4ztjEwmAHFD+PT0v6b59+53P1QLfZtDOzfCGhhO8bM23Ygd4NEAtBhbYcT2xh4CNhymC1Zcm5fcu6MMw+bDRLb0pPbmHmKJRLw+IW9/5jhhzff7HL725MPS/5ss7ad396+8cPHHtwhhgQYGyA0KGoSew4QowUF/CBdyygYBaNgFAxbAAC4ZE7q5i5kOAAAAABJRU5ErkJggg==","orcid":"","institution":"Kindai university faculty of medicine","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Terumasa","middleName":"","lastName":"Ikeda","suffix":""},{"id":934041,"identity":"443e39e0-5d9b-43ef-ae7e-e0abfd094b16","order_by":1,"name":"Hiroshi Miyamto","email":"","orcid":"","institution":"Kindai University Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Hiroshi","middleName":"","lastName":"Miyamto","suffix":""},{"id":934042,"identity":"65680e94-4917-49bb-af68-cd301cd881b0","order_by":2,"name":"Masao Akagi","email":"","orcid":"","institution":"Kindai University Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Masao","middleName":"","lastName":"Akagi","suffix":""}],"badges":[],"createdAt":"2020-07-13 19:44:55","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-42579/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-42579/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12891-023-06214-2","type":"published","date":"2023-02-11T18:43:22+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":1661839,"identity":"1ff7c4fd-770c-463a-8c5d-4cb52c56d2fb","added_by":"auto","created_at":"2020-07-23 15:12:05","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":46566,"visible":true,"origin":"","legend":"69-year-old male with K-line (+). Laminoplasty was performed from C3 to C7. C2/C7 angle was 29° at preoperation (A) and 28° at follow-up (B). The JOA score improved from 13 points to 15.5 points. The recovery rate of the JOA score was 62.5%.","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-42579/v1/1.jpg"},{"id":1661840,"identity":"e3724095-07cb-461b-9362-89311f7776e7","added_by":"auto","created_at":"2020-07-23 15:12:05","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":42404,"visible":true,"origin":"","legend":"44-year-old male with K-line (-). Laminoplasty was performed from C3 to C7. C2/C7 angle was -39°at preoperation (A) and -39° at follow-up (B). The JOA score improved from 7 points to 9 points. The recovery rate of the JOA was 20%.","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-42579/v1/2.jpg"},{"id":1661841,"identity":"0f04e164-4b34-419d-8d19-51007314eab9","added_by":"auto","created_at":"2020-07-23 15:12:06","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":40129,"visible":true,"origin":"","legend":"50-year-old female with K-line (-). Laminoplasty was performed from C3 to C7. C2/C7 angle was -1° at preoperation (A) and -16° at follow-up (B). The JOA improved from 11 points to 13.5 points. The recovery rate of the JOA score was 41.7%. The protruded disc at C5/6 had a contact with K-line at preoperation (A). However, at the follow-up (B), the disc was absorbed, and the classification was changed to K-line (+).","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-42579/v1/3.jpg"},{"id":44719042,"identity":"e96d7801-0b6e-45c0-bae6-f84451dbff67","added_by":"auto","created_at":"2023-10-16 18:52:38","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":312267,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-42579/v1/f1e77687-62cd-4a2c-ae74-d0b3063f5e52.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eUsefulness of K-line in predicting prognosis of laminoplasty for cervical spondylotic myelopathy\u003c/p\u003e","fulltext":[{"header":"Background","content":" \u003cp\u003eLaminoplasty (LP) is occasionally indicated for cervical myelopathy caused by a narrow spinal canal due to spondylosis and/or ossification of the posterior longitudinal ligament (OPLL). This procedure enables sufficient decompression in multi-segmental stenotic myelopathy. The effects of decompression with LP are attributed to two mechanisms, i.e., direct posterior decompression and posterior shifting of the spinal cord from anterior compressive lesions [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. However, a large anterior bulge, as with a protruded disc or OPLL, often worsens the postoperative neurological recovery rate after LP [\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Cervical kyphosis may also lead to poor surgical outcomes by interfering with posterior shifting of the spinal cord [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Iwasaki et al. [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] reported that the neurologic outcome of LP for cervical OPLL was poor or fair in patients with occupying ratio greater than 60%, hill-shaped ossification, and postoperative kyphotic change in cervical alignment.\u003c/p\u003e \u003cp\u003eFujiyoshi et al. [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] developed the K-line, a straight line connecting the midpoints of the spinal canal at C2 and C7 on plain lateral radiograph, as a new index to evaluate cervical alignment and OPLL size in one parameter, i.e., OPLL did not exceed the K-line in the K-line (+) group and did exceed the K-line in the K-line (-) group.\u003c/p\u003e \u003cp\u003eWith regard to cervical spondylotic myelopathy (CSM), Suda et al. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] reported that the patients with local kyphosis\u0026thinsp;≧\u0026thinsp;13 degrees exhibited poorer clinical outcomes than those without kyphosis due to the mechanisms described above. On the other hand, Chiba et al. [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] reported that several patients accompanying by cervical kyphosis obtained an acceptable clinical outcome after LP alone, probably because of the slackening of the spinal cord due to reduced multilevel disc height, which would not be compatible with cervical OPLL. Therefore, usefulness of K-line for CSM was uncertain. The purpose of the present study was to investigate whether K-line can provide a predictor of the clinical outcomes of LP for CSM.\u003c/p\u003e "},{"header":"Methods","content":" \u003cp\u003eParticipants in the present study comprised Sixty-eight patients who underwent LP as decompression surgery for CSM were involved in the present study. Exclusion criteria were myelopathy caused by single-level disc herniation, OPLL, or a history of cervical spinal surgery, spinal tumor, trauma, and infection.\u003c/p\u003e \u003cp\u003eAs the ethics approval, the study protocol was approved by the Institutional Review Board of Kindai University Hospital ( Control Cohort Study, No.2020-025). We conducted this study under approval of the institutional review board and informed consent was obtained from all patients.\u003c/p\u003e \u003cp\u003eThe operative technique was previously described by Miyazaki and Kirita\u0026rsquo;s method (n\u0026thinsp;=\u0026thinsp;64) and a modification of Kurokawa\u0026rsquo;s method (n\u0026thinsp;=\u0026thinsp;4). The method of Miyazaki and Kirita was a procedure in which bilateral gutters were made and the laminae were split in the middle with a high-speed drill. The laminae were kept open with nylon sutures in the deep fascia bilaterally. The modification of Kurokawa\u0026rsquo;s method was the procedure in which mid-splitting of the spinous processes was performed using a T-saw [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. After spreading the split spinous processes, hydroxyappatite spacers were sutured as necessary between the opened spinous process at each level.\u003c/p\u003e \u003cp\u003eWe were able to obtain follow-up results for all 68 patients (50 males and 18 females). Mean age at surgery was 60.3\u0026nbsp;years (range, 32\u0026ndash;92\u0026nbsp;years). All patients were followed-up for 2\u0026nbsp;year or longer after surgery. Mean follow-up period was 74.2\u0026nbsp;months (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The spinal levels of decompression were from C3 to C7 in 47 patients, C4 to C7 in 4 patients, C3 to C6 in 8 patients, C3 to Th1 and C2 to C7 in 3 patients each, and C4 to C5, C3 to C5 and C4 to Th1 in 1 patient each.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBackground characteristics of the participants\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCharacteristic\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge (years old)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e60.3\u0026thinsp;\u0026plusmn;\u0026thinsp;12.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex (male/female)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e50 / 18\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFollow-up period (months)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e74\u0026thinsp;\u0026plusmn;\u0026thinsp;43.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe JOA score at preoperation (points)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe JOA score at follow-up (points)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe RR (%) of the JOA score\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e45.5\u0026thinsp;\u0026plusmn;\u0026thinsp;28.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC2-7 angle at preoperation (degrees)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.1\u0026thinsp;\u0026plusmn;\u0026thinsp;12.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC2-7 angle at follow-up (degrees)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.6\u0026thinsp;\u0026plusmn;\u0026thinsp;14.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"2\"\u003eData are presented as means\u0026thinsp;\u0026plusmn;\u0026thinsp;SD.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"2\"\u003eJOA: Japanese Orthopaedic Association\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"2\"\u003eRR: recovery rate\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \n\u003ch2\u003eClinical Findings\u003c/h2\u003e\n \u003cp\u003eThe Japanese Orthopaedic Association (JOA) scoring system was used to evaluate the severity of cervical myelopathy preoperativly and at the final follow-up. The recovery rate (RR) of the JOA score was calculated using the method of Hirabayashi et al. to compare preoperatively and at final follow-up JOA scores. As defined by Hirabayashi et al., RR (%) was calculated as (postoperative JOA score \u0026ndash; preoperative JOA score) / (17- preoperative JOA score)\u0026thinsp;\u0026times;\u0026thinsp;100.\u003c/p\u003e \n\u003ch2\u003eRadiological Evaluation\u003c/h2\u003e\n \u003cp\u003eC2-7 angle was measured on T2-weighted sagittal images of magnetic resonance imaging (MRI) preoperatively and at the final follow-up. In CSM patients, although C2-7 angle was positive, local kyphosis existed due to the alignment (e.g., sigmoid, reverse sigmoid, and kyphosis) in several patients. In those cases, local kyphosis angle was also measured on T2-weighted sagittal images of MRI at preoperatively and at the follow-up. The K-line was defined as the straight line connecting the midpoints of the spinal canal at C2 and C7 on midsagittal T2-weighted MRI in the present study. The patients were divided into two groups; K-line (-) and K-line (+). In the K-line (-) group, the anterior structural factors (e.,g., disc herniation, osteophyte, or kyphotic beak of the vertebra) crossed the K-line with no space between the K-line and the anterior wall of the canal. On the other hand, in the K-line (+) group, the anterior structural factors did not exceed K-line and stayed within the ventral area of K-line.\u003c/p\u003e \u003cp\u003eClinical parameters such as gender, age, preoperative JOA score, the JOA score at the follow-up, the RR of the JOA score, and radiological parameters such as preoperative C2-7 angle, C2-7 angle at the follow-up, preoperative local kyphosis angle, and the local kyphosis angle at the follow-up were compared between K-line(-) and K-line (+).\u003c/p\u003e \u003cp\u003eStatistical analysis was performed using Student t-test and Mann-Whitney U test, with \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05 considered statistically significant. Statistical analyses of data were performed with Stat Flex Ver.6 (Artech Co., Ltd., Osaka, Japan). Results were presented as means\u0026thinsp;\u0026plusmn;\u0026thinsp;SD.\u003c/p\u003e "},{"header":"Results","content":" \u003cp\u003eThe mean JOA score was 9.7 points (range, 1\u0026ndash;14 points) before surgery and 13.1 points (range, 1\u0026ndash;17 points) at final follow-up. The Mean RR of the JOA score was 45.5%. The C2-7 angles at preoperatively and at follow-up were 4.1\u0026thinsp;\u0026plusmn;\u0026thinsp;12.5 and 6.6\u0026thinsp;\u0026plusmn;\u0026thinsp;14.3 degrees respectively (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). K-line (-) were 11 patients (8 male, 3 females; mean of 57.2\u0026nbsp;years old), and K-line (+) were 57 patients (42 male, 15 females; mean of 60.9\u0026nbsp;years old). The JOA score at preoperatively and at follow-up were 10.1\u0026thinsp;\u0026plusmn;\u0026thinsp;4.1 and 11.6\u0026thinsp;\u0026plusmn;\u0026thinsp;4.1 in K-line (-) and 9.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6 and 13.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.2 in K-line (+). The mean RR of JOA score were 19.4% in K-line (-) and 50.6% in K-line (+) group, representing a significant difference. With respect to radiological findings, preoperative C2-7 angle was significantly smaller in the K-line (-) group (-10.1\u0026thinsp;\u0026plusmn;\u0026thinsp;9.0 degrees) than in the K-line (+) group (6.8\u0026thinsp;\u0026plusmn;\u0026thinsp;11.2 degrees). The C2-7 angle at follow-up was significantly smaller in the K-line (-) group (-11.8\u0026thinsp;\u0026plusmn;\u0026thinsp;10.4 degrees) than in the K-line (+) group (10.2\u0026thinsp;\u0026plusmn;\u0026thinsp;12.1 degrees). Preoperative local kyphosis angle was significantly larger in the K-line (-) group (16.6\u0026thinsp;\u0026plusmn;\u0026thinsp;10.0 degrees) than in the K-line (+) group (1.6\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1 degrees). Local kyphosis angle at follow-up was significantly larger in the K-line (-) group (14.7\u0026thinsp;\u0026plusmn;\u0026thinsp;7.6 degrees) than in the K-line (+) group (1.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1 degrees) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison between K-line (-) and K-line (+)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eK-line(-)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eK-line(+)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNumbers of the patients\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge (years old)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e57.2\u0026thinsp;\u0026plusmn;\u0026thinsp;17.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e60.9\u0026thinsp;\u0026plusmn;\u0026thinsp;11.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe JOA score at preoperation (points)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.1\u0026thinsp;\u0026plusmn;\u0026thinsp;4.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe JOA score at follow-up (points)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11.6\u0026thinsp;\u0026plusmn;\u0026thinsp;4.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e13.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe RR of the JOA score (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19.4\u0026thinsp;\u0026plusmn;\u0026thinsp;25.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50.6\u0026thinsp;\u0026plusmn;\u0026thinsp;25.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC2-7angle at preoperation\u003c/p\u003e \u003cp\u003e(degrees)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-10.1\u0026thinsp;\u0026plusmn;\u0026thinsp;9.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.8\u0026thinsp;\u0026plusmn;\u0026thinsp;11.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC2-7angle at follow-up (degrees)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-11.8\u0026thinsp;\u0026plusmn;\u0026thinsp;10.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.2\u0026thinsp;\u0026plusmn;\u0026thinsp;12.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLocal kyphosis angle\u003c/p\u003e \u003cp\u003eat preoperation (degree)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16.6\u0026thinsp;\u0026plusmn;\u0026thinsp;10.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.6\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLocal kyphosis angle at follow-up (degree)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14.7\u0026thinsp;\u0026plusmn;\u0026thinsp;7.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eData are presented as means\u0026thinsp;\u0026plusmn;\u0026thinsp;SD.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eJOA: Japanese Orthopaedic Association\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eRR: recovery rate\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eWith follow-up, we found that 7 cases of preoperative K-line (-) changed to K-line (+) because of absorption of the protruded disc (disc type; Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). On the other hand, 4 cases of preoperative K-line (-) due to the osteophyte or the beak of local kyphosis still stayed as K-line (-) at follow-up (osseous type; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). We compared the clinical data between disc type (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) and osseous type as shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Mean RR in the K-line (-) group classified as disc type was 27.6% at follow-up (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). On the other hand, mean RR in the K-line (-) group classified as osseous type was only 5.0% (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). This difference was statistically significant.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCharacteristics of K-line (-) patients by types\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDisc type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eOsseous type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNumber\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge (yr)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e57.4\u0026thinsp;\u0026plusmn;\u0026thinsp;15.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e56.8\u0026thinsp;\u0026plusmn;\u0026thinsp;23.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePre-JOA (points)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11.1\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.1\u0026thinsp;\u0026plusmn;\u0026thinsp;5.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFU-JOA (points)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.6\u0026thinsp;\u0026plusmn;\u0026thinsp;5.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRR of JOA (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e27.6\u0026thinsp;\u0026plusmn;\u0026thinsp;28.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.0\u0026thinsp;\u0026plusmn;\u0026thinsp;10.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePre-MRI C2-7angle (degrees)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-6.0\u0026thinsp;\u0026plusmn;\u0026thinsp;7.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-17.3\u0026thinsp;\u0026plusmn;\u0026thinsp;7.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFu-MRI C2-7angle (degrees)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-6.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-20.8\u0026thinsp;\u0026plusmn;\u0026thinsp;12.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eData are presented as means\u0026thinsp;\u0026plusmn;\u0026thinsp;SD.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eJOA: Japanese Orthopaedic Association\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eRR: recovery rate\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e "},{"header":"Discussion","content":" \u003cp\u003eSurgical outcomes for CSM accompanying local kyphosis have generally been reported as less than acceptable. Baba et al. [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] reported that patients with preoperative kyphosis (mean angle of 11.7\u0026deg;) show significantly poorer neurological improvement.\u003c/p\u003e \u003cp\u003eSuda et al. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] also reported that outcomes of LP for CSM accompanying local kyphosis with an angle exceeding 13 degrees (when coexisted with myelomalacia) and 5 degrees (without myelomalacia) were poorer than those for CSM without local kyphosis in their multivariate logistic regression analysis. In contrast, Kaptain et al. [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] and Uchida et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] have shown that surgical outcomes were not correlated with preoperative cervical kyphosis. We speculated that their conclusion might have been due to the kyphosis in their patients being mild. Kasai and Uchida reported that the presence or absence of anterior or posterior subarachnoid space of the spinal cord in postoperative MRI correlated significantly with clinical outcome of LP [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The present study has indicated that K-line can be a factor to predict the clinical outcome of LP for CSM. That is, cases preoperatively defined as K-line (-) displayed poorer clinical outcome after LP compared to those defined K-line (+). In particular, this is the first report to show that the disc type for preoperative K-line (-), in which disc was absorbed during the follow-up and the classification changed into K-line (+) at follow-up, achieved better clinical outcomes compared to patients showing the osseous type. However, outcome for disc type were worse than those of K-line (+). Moreover, predicting whether the bulging disc will be resorbed after surgery in not currently possible. Miyamoto et al. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] reported that posterior correction surgery for patients with CSM accompanied by local kyphosis resulted in a better clinical outcome than LP alone. Therefore, posterior correction surgery combined with LP should thus be considered for CSM in K-line (-) patients.\u003c/p\u003e "},{"header":"Conclusion","content":" \u003cp\u003eThe present study has indicated that K-line can be a factor to predict the clinical outcome of LP for CSM. In K-line (-), the disc type showed somewhat better outcomes compared to the osseous type. However, the results were not sufficient. Therefore, posterior correction surgery combined with LP should be considered for CSM with K-line(-).\u003c/p\u003e "},{"header":"Abbreviations","content":"\u003cp\u003eLP: Laminoplasty; OPLL: posterior longitudinal ligament; CSM: cervical spondylotic myelopathy; JOA: The Japanese Orthopaedic Association; RR: recovery rate\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was analyzed using data obtained from patients who provided informed consent.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study protocol was approved by the Institutional Review Board of Kindai University Hospital ( Control Cohort Study, No.2020-025). We conducted this study under approval of the institutional review board and informed consent was obtained from all patients. This study does not include patients under 18\u0026nbsp;years of age.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authoers declealre no potential conflict interest concerning this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTI collected the datas and interpreted, and wrote the manuscript. HM,MA contributed to design of the work and revised the manuscript critically for important content. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank Dr. Koichiro Maeno for his help in collecting clinical data.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e \u003cspan\u003eHirabayashi K, Satomi K. Operative procedure and result of expansive open-door laminoplasty. Spine. 1988;13(7):870\u0026ndash;6.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eHirabayashi K, Watanabe K, Wakano N, Suzuki N, Satomi K, Ishii Y. Expansive open-door laminoplasty for cervical spinal stenotic myelopathy. Spine. 1983;8(7):693\u0026ndash;9.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eSodeyama T, Goto S, Mochizuki M, Takahashi J, Moriya H. Effect of decompression enlargement laminoplasty for posterior shifting of the spinal cord. Spine (Phila pa 1976). 1999;24(15):1527\u0026ndash;31.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eIwasaki M, Okuda S, Miyauchi A, Sakaura H, Mukai Y, Yonenobu K, Yoshikawa H. Surgical strategy for cervical myelopathy due to ossification of the posterior longitudinal ligament: Part 1: Clinical results and limitations of laminoplasty. Spine. 2007;32(6):647\u0026ndash;53.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eYamazaki A, Homma T, Uchiyama S, Katsumi Y, Okumura H. Morphologic limitations of posterior decompression by midsagittal splitting method for myelopathy caused by ossification of the posterior longitudinal ligament in the cervical spine. Spine. 1999;24(1):32\u0026ndash;4.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eBaba H, Uchida K, Maezawa Y, Furusawa N, Azuchi M, Imura S. Lordotic alignment and posterior migration of the spinal cord following en bloc open-door laminoplasty for cervical myelopathy: a magnetic resonance imaging study. J Neurol. 1996;243(9):626\u0026ndash;32.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eFujiyoshi T, Yamazaki M, Kawabe J, Endou T, Furuya T, Koda M, Okawa A, Takahashi K, Konishi H. A new concept for making decisions regarding the surgical approach for cervical ossification of the posterior longitudinal ligament: the K-line. Spine. 2008;33(26):E990\u0026ndash;3.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eSuda K, Abumi K, Ito M, Shono Y, Kaneda K, Fujiya M. Local kyphosis reduces surgical outcomes of expansive open-door laminoplasty for cervical spondylotic myelopathy. Spine. 2003;28(12):1258\u0026ndash;62.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eChiba K, Toyama Y, Watanabe M, Maruiwa H, Matsumoto M, Hirabayashi K. Impact of longitudinal distance of the cervical spine on the results of expansive open-door laminoplasty. Spine. 2000;25(22):2893\u0026ndash;8.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eTomita K, Kawahara N, Toribatake Y, Heller JG. (1998) Expansive midline T-saw laminoplasty (modified spinous process-splitting) for the management of cervical myelopathy. Spine Jan 1;23(1):32\u0026ndash;37.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eBaba H, Maezawa Y, Furusawa N, imura S, Tomita K. Flexibility and alignment of the cervical spine after laminoplasty for spondylotic myelopathy. A radiographic study. Int orthop. 1995;19(2):116\u0026ndash;21.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eKaptain GJ, Simmons NE, Replogle RE, Pobereskin L. Incidence and outcome of kyphotic deformity following laminectomy for cervical spondylotic myelopathy. J Neurosurg. 2000;93(2 suppl):199\u0026ndash;204.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eUchida K, Nakajima H, Sato R, Yayama T, Mwaka ES, Kobayashi S, Baba H. Cervical spondylotic myelopathy associated with kyphosis or sagittal sigmoid aliment: outocome after anterior or posterior decompression. J neurosug Spine. 2009;11(5):521\u0026ndash;8.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eKasai Y, Uchida A. New evaluation method using preoperative magnetic resonance imaging for cervical spondylotic myelopathy. Arch Orthop Trauma Surg. 2001;Oct(9):508\u0026ndash;10. 121(.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eMiyamoto H, Maeno K, Uno K, Kakutani K, Nishida K, Sumi M. Outcomes of surgical intervention for cervical spondylotic myelopathy accompanying local kyphosis (comparison between laminoplasty alone and posterior reconstruction surgery using the screw-rod system). Eur Spine J. 2014;23(2):341\u0026ndash;34.\u003c/span\u003e \u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"cervical spondylotic myelopathy, K-line, cervical spinal kyphosis","lastPublishedDoi":"10.21203/rs.3.rs-42579/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-42579/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground: \u003c/strong\u003eK-line is widely recognized as a useful index to evaluate alignment and size of the cervical ossification of the posterior longitudinal ligament (OPLL) in one parameter. The purpose of this study was to investigate that K-line could be a tool to predict the prognosis of LP for cervical spondylotic myelopathy (CSM) as well. \u003c/p\u003e\u003cp\u003e\u003cstrong\u003eMethods: \u003c/strong\u003eSixty-eight patients who underwent LP were enrolled. C2-7 angle, local kyphosis angle, and K-line which is the straight line connecting the midpoints of the spinal canal at C2 and C7 was evaluated on T2- weighted sagittal magnetic resonance imaging (MRI). The JOA score and the recovery rate of the JOA score were evaluated at pre-operation and at follow-up. C2/C7 angle, local kyphosis angle, the JOA score, and the recovery rate were compared between K-line (-) and K-line (+) groups.\u0026nbsp;\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eThe recovery rate of K-line (+) group (50.6%) was significantly better than that of K-line (-) (19.4%). In K-line (-), the disc type in which the protruded disc was absorbed during the follow-up showed statistically better recovery rate (27.6%) at follow-up compared to other K-line (-) in which anterior cord compression due to the osteophyte or the kyphotic beak was not absorbed (osseous type, 5.0%).\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConclusion: \u003c/strong\u003eThe present study has indicated that K-line can be a factor to predict the clinical outcome of LP for CSM. In K-line (-), the disc type showed somewhat better outcomes compared to the osseous type. However, the results were not sufficient.\u0026nbsp;\u003c/p\u003e","manuscriptTitle":"Usefulness of K-line in predicting prognosis of laminoplasty for cervical spondylotic myelopathy","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2020-07-23 15:12:05","doi":"10.21203/rs.3.rs-42579/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2022-07-22T00:04:50+00:00","index":0,"fulltext":""},{"type":"decision","content":"Reject after review","date":"2020-10-08T12:00:00+00:00","index":"","fulltext":""},{"type":"reviewersInvited","content":"","date":"2020-08-24T12:00:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2020-07-17T12:00:00+00:00","index":"","fulltext":""},{"type":"submitted","content":"","date":"2020-07-16T12:00:00+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2020-07-16T12:00:00+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2020-07-16T12:00:00+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a7ea9e6c-6fde-4ad2-bf6d-8891bf22eb3f","owner":[],"postedDate":"July 23rd, 2020","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":193916,"name":"Orthopedics"},{"id":193917,"name":"Orthopedic Surgery"}],"tags":[],"updatedAt":"2023-10-16T18:50:06+00:00","versionOfRecord":{"articleIdentity":"rs-42579","link":"https://doi.org/10.1186/s12891-023-06214-2","journal":{"identity":"bmc-musculoskeletal-disorders","isVorOnly":false,"title":"BMC Musculoskeletal Disorders"},"publishedOn":"2023-02-11 18:43:22","publishedOnDateReadable":"February 11th, 2023"},"versionCreatedAt":"2020-07-23 15:12:05","video":"","vorDoi":"10.1186/s12891-023-06214-2","vorDoiUrl":"https://doi.org/10.1186/s12891-023-06214-2","workflowStages":[]},"version":"v1","identity":"rs-42579","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-42579","identity":"rs-42579","version":["v1"]},"buildId":"rHA-KDH7Qsr4HCuvH75dn","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}