title: [Changes of sagittal balance of cervical spine after open-door expansive laminoplasty].
abstract: OBJECTIVE
  To explore the changes of sagittal balance of cervical spine after open-door expansive laminoplasty.
  
  
  METHODS
  The clinical and radiological data were analyzed retrospectively for 90 patients undergoing open-door expansive laminoplasty due to cervical spondylotic myelopathy. The Japanese Orthopedic Association (JOA) score and 3 cervical sagittal parameters including C2-C7 SVA, C0-2 Cobb angle and T1-Slope on lateral view radiographs were recorded before operation and at the final follow-up.
  
  
  RESULTS
  The average follow-up period was 16.7 (3-40) months. The post-operative JOA score rose to 14.6 ± 0.2 from pre-operative 12.2 ± 0.3 with 43.5% ± 4.2% recovery rate. The post-operative values of C2-C7 SVA, C0-2 Cobb angle and T1-Slope were significantly different from pre-operative ones (P = 0.022, P < 0.001, P = 0.002) . C2-C7 SVA increased to (23.0 ± 1.2) mm from pre-operative (20.7 ± 1.1) mm. C0-2 Cobb angle increased (23.1 ± 0.8) ° from pre-operative (19.9 ± 0.8)°; T1-Slope increased to (26.2 ± 0.7)° from pre-operative (25.1 ± 0.7)°. The changes of C0-2 Cobb angle and T1-Slope were correlated with that of C2-C7 SVA respectively (Pearson = 0.469, P < 0.001) (Pearson = 0.303, P = 0.004) . Patients with higher preoperative T1-Slope had less JOA improvement (31.5% vs 53.7%, P = 0.019) than those with lower preoperative T1-Slope after laminoplasty.
  
  
  CONCLUSIONS
  The sagittal balance of cervical spine significantly changes after open-door expansive laminoplasty with forward tilting of cervical vertebra. And compensation occurs by excessive high-strength contraction of posterior muscles to maintain lordosis in upper cervical spine. A higher pre-OP T1-Slope affects the outcomes of open-door expansive laminoplasty.
authors.affiliation: Department of Orthopedics, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Shengrong
authors.initials: S
authors.lastname: Lin
authors.affiliation: Department of Orthopedics, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Feifei
authors.initials: F
authors.lastname: Zhou
authors.affiliation: Department of Orthopedics, Peking University Third Hospital, Beijing 100191, China. Email: sunyuor@vip.sina.com.
authors.forename: Yu
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Department of Orthopedics, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Zhongqiang
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Department of Orthopedics, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Fengshan
authors.initials: F
authors.lastname: Zhang
authors.affiliation: Department of Orthopedics, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Shengfa
authors.initials: S
authors.lastname: Pan
mesh_terms: D044466:Asian People; D002574:Cervical Vertebrae; D006801:Humans; D065406:Laminoplasty; D009333:Neck; D011184:Postoperative Period; D012189:Retrospective Studies; D013118:Spinal Cord Diseases