title: The severity of operative invasion to the posterior muscular-ligament complex influences cervical sagittal balance after open-door laminoplasty.
abstract: OBJECTIVE
  The aim of this study was to investigate how the severity of operative invasion to the posterior muscular-ligament complex impacts postoperative cervical sagittal balance.
  
  
  METHODS
  Ninety cases of open-door expansive laminoplasty due to cervical spondylotic myelopathy were reviewed. Fifty-three patients underwent laminoplasty with unilateral preservation of the muscular-ligament complex (unilateral elevation group). Thirty-seven patients underwent traditional open-door laminoplasty (bilateral elevation group). Preoperative and postoperative cervical sagittal parameters, including C2-C7 sagittal vertical axis (SVA), C0-2 Cobb angle and T1 slope, were compared. The cervical curvature, range of motion (ROM) and JOA score were also compared.
  
  
  RESULTS
  The average follow-up time was 16.7 months (range 3-40 months). C2-C7 SVA significantly increased in the bilateral elevation group (+4.9 mm, P = 0.005) but remained unchanged in the unilateral elevation group (-0.2 mm, P = 0.414). The C0-2 Cobb angle increased in both groups (+4.1°, P < 0.001; +2.5°, P = 0.002). The T1 slope also increased in both groups (+1.1°, P = 0.015; +0.7°, P = 0.042). The postoperative C3-C7 curvature significantly decreased in the bilateral elevation group (-4.1°, P < 0.001). The C3-C7 ROM decreased in both groups (-17.9°, P < 0.001; -15.1°, P < 0.001). C2-C7 SVA was positively correlated with the T1 slope (Pearson = 0.468, P < 0.001) and negatively correlated with the C3-C7 curvature (Pearson = -0.322, P = 0.001). The C0-2 Cobb angle was positively correlated with C2-C7 SVA (Pearson = 0.303, P = 0.004) and negatively correlated with the C3-C7 curvature (Pearson = -0.362, P < 0.001). There was no significant between-group difference in the JOA improvement rate.
  
  
  CONCLUSIONS
  Open-door laminoplasty significantly affected postoperative cervical sagittal balance, with the cervical vertebra appearing to tilt forward. As the severity of surgical invasion to the posterior muscular-ligament complex increased, the loss of cervical sagittal balance also increased.
authors.affiliation: Orthopaedic Department, Peking University Third Hospital, 49 North Garden Street, Haidian District, Beijing, 100191, China.
authors.forename: Shengrong
authors.initials: S
authors.lastname: Lin
authors.forename: Feifei
authors.initials: F
authors.lastname: Zhou
authors.forename: Yu
authors.initials: Y
authors.lastname: Sun
authors.forename: Zhongqiang
authors.initials: Z
authors.lastname: Chen
authors.forename: Fengshan
authors.initials: F
authors.lastname: Zhang
authors.forename: Shengfa
authors.initials: S
authors.lastname: Pan
mesh_terms: D000328:Adult; D000368:Aged; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D065406:Laminoplasty / Q000379:methods*; D008022:Ligaments / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D064170:Paraspinal Muscles / Q000601:surgery*; D011859:Radiography; D055009:Spondylosis / Q000000981:diagnostic imaging / Q000601:surgery*