title: Laminar closure after classic Hirabayashi open-door laminoplasty.
abstract: METHODS
  Prospective analysis of preoperative and postoperative radiological data.
  
  
  OBJECTIVE
  To assess the incidence and extent of laminar closure after Hirabayashi open-door laminoplasty, as determined by multi-detector computed tomography (CT), and to investigate the influence of this phenomenon on spinal cord compression, as shown by magnetic resonance imaging (MRI).
  
  
  BACKGROUND
  Although laminar closure occurs after laminoplasty, little is known about its progression or its effect on restenosis of the spinal canal.
  
  
  METHODS
  Thirty-five patients (132 laminae) underwent classic Hirabayashi laminoplasty and were followed for at least 12 months. Multi-detector CT was performed preoperatively, at 1 week, or less, and 6 months after surgery. At each level, the anteroposterior (AP) diameter of the spinal canal and the angle of the opened lamina were measured. MRI was performed preoperatively and 1 year after surgery to evaluate the severity of cord compression based on a six-grade classification system.
  
  
  RESULTS
  The mean AP diameter and the mean opening angle increased immediately after surgery (P <0.05 each) and decreased 6 months after surgery (P < 0.0001 each), with the AP diameter and opening angle decreasing by 9.4% and 10.2%, respectively. CT at 6 months showed fusion of the hinge in 91% of opened laminae. Segments with high-grade cord compression (grade ≥3) at 1 year showed greater decreases in AP diameter and opening angle (P < 0.05).
  
  
  CONCLUSIONS
  After classic Hirabayashi open-door laminoplasty, opened laminae showed reclosure at 6 months, with approximately 10% decrease in AP diameter and opening angle. Postoperative lamina closure was associated with recurrent spinal cord compression, suggesting the need for other augmenting techniques that keep the laminae opened.
authors.affiliation: Department of Orthopaedic Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Dong-Ho
authors.initials: DH
authors.lastname: Lee
authors.forename: Soo-An
authors.initials: SA
authors.lastname: Park
authors.forename: Nam Heun
authors.initials: NH
authors.lastname: Kim
authors.forename: Chang Ju
authors.initials: CJ
authors.lastname: Hwang
authors.forename: Yung-Tae
authors.initials: YT
authors.lastname: Kim
authors.forename: Choon Sung
authors.initials: CS
authors.lastname: Lee
authors.forename: K Daniel
authors.initials: KD
authors.lastname: Riew
mesh_terms: D000368:Aged; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007796:Laminectomy / Q000009:adverse effects / Q000379:methods*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000209:etiology; D011446:Prospective Studies; D011843:Radiculopathy / Q000000981:diagnostic imaging / Q000601:surgery*; D013115:Spinal Canal / Q000000981:diagnostic imaging / Q000601:surgery; D013117:Spinal Cord Compression / Q000000981:diagnostic imaging / Q000209:etiology; D013118:Spinal Cord Diseases / Q000000981:diagnostic imaging / Q000601:surgery*; D013997:Time Factors; D014057:Tomography, X-Ray Computed