title: Effect of the decompressive extent on the magnitude of the spinal cord shift after expansive open-door laminoplasty.
abstract: METHODS
  A retrospective study to analyze the effect of decompressive extent on the posterior shift of spinal cord after expansive open-door laminoplasty (ELAP).
  
  
  OBJECTIVE
  To investigate the effect of decompressive extent on cord shift distance after ELAP, and determine the morphologic limitations of posterior approach when the cervical alignment is lordotic or straight.
  
  
  BACKGROUND
  It is still controversial on the effect of space available for spinal cord at the level cephalad to the decompression with cord shift. Moreover, there is less understanding regarding the significance of decompressive extent of laminoplasty in relation to spinal cord shift and clinical outcome.
  
  
  METHODS
  Preoperative and postoperative MRIs of 76 patients with a straight or lordotic cervical spine who had undergone cervical laminoplasty were reviewed and evaluated retrospectively. Radiographic parameters including cervical sagittal alignment, space available at the level cephalad, the thickness of compressive mass, and the average anterior subarachnoid space were measured. Laminoplasty was performed from C1 to C7 in 11 cases (CI group), C2 to C7 in 30 cases (CII group), and C3 to C7 in 35 cases (CIII group). According to whether the anterior indirect decompression was adequate or not, CII and CIII groups were further divided into two subgroups, the noncontact group in which the spinal cord was completely separated from the anterior compressive mass after laminoplasty, and the contact group in which there was residual cord compression after laminoplasty. The recovery rate that based on the Japanese Orthopedic Association score was calculated for each patient.
  
  
  RESULTS
  There were statistically significant differences in the average anterior subarachnoid space among CI, CII, and CIII groups (P < 0.05);the average anterior subarachnoid space was the largest in CI group, and the smallest in CIII group. The space available at the level cephalad had strong sigmoidal correlation with cord postoperative shift in CIII group (R = 0.91). A higher neurologic recovery rate (69% ± 20% vs. 29% ± 11%; P < 0.05) in the noncontact group after surgery than in the contact group, with a similar follow-up period.
  
  
  CONCLUSIONS
  The posterior decompression extent is a main factor affecting cord shift distance after laminoplasty in the context of a straightened or lordotic cervical curvature. The space available at the levels cephalad is a key factor to predict cord shift distance in laminoplasty from C3 to C7. Neurologic recovery rate after ELAP is affected by whether the anterior indirect decompression was adequate or not.
authors.affiliation: Department of Orthopaedic Surgery, West China Hospital, West China Medical School, Sichuan University, Chengdu, China.
authors.forename: Qingquan
authors.initials: Q
authors.lastname: Kong
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.forename: Limin
authors.initials: L
authors.lastname: Liu
authors.forename: Tao
authors.initials: T
authors.lastname: Li
authors.forename: Quan
authors.initials: Q
authors.lastname: Gong
authors.forename: Jiancheng
authors.initials: J
authors.lastname: Zeng
authors.forename: Yueming
authors.initials: Y
authors.lastname: Song
authors.forename: Hao
authors.initials: H
authors.lastname: Liu
authors.forename: Shaobo
authors.initials: S
authors.lastname: Wang
authors.forename: Yu
authors.initials: Y
authors.lastname: Sun
authors.forename: Fengshan
authors.initials: F
authors.lastname: Zhang
authors.forename: Mai
authors.initials: M
authors.lastname: Li
authors.forename: Zhongqiang
authors.initials: Z
authors.lastname: Chen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D002574:Cervical Vertebrae / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D002681:China; D019299:Decompression, Surgical / Q000009:adverse effects / Q000379:methods*; D005260:Female; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D016014:Linear Models; D008141:Lordosis / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009460:Neurologic Examination; D017711:Nonlinear Dynamics; D019637:Orthopedic Procedures / Q000009:adverse effects; D017887:Ossification of Posterior Longitudinal Ligament / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D020127:Recovery of Function; D012189:Retrospective Studies; D013116:Spinal Cord / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D055009:Spondylosis / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D013346:Subarachnoid Space / Q000473:pathology; D013997:Time Factors; D016896:Treatment Outcome