title: Progression of ossification of the posterior longitudinal ligament following en bloc cervical laminoplasty.
abstract: BACKGROUND
  Ossification of the posterior longitudinal ligament often causes compressive myelopathy. Ossification is a progressive disease, and it has been reported that the area of ossification increases after decompressive surgery. However, it is uncertain how the progression of ossification affects the long-term outcome after cervical laminoplasty. This study was performed to clarify the relationship between the progression of ossification of the posterior longitudinal ligament and the clinical results following en bloc cervical laminoplasty.
  
  
  METHODS
  Forty-five patients who were followed for more than ten years after laminoplasty participated in this study. Radiographs and tomograms of the cervical spine of each patient were made before and after the operation and at the time of the latest follow-up. The extent of ossification in the longitudinal and sagittal axes was evaluated. Neurological function was graded with use of the Japanese Orthopaedic Association scoring system. The relationship between the progression of ossification and the score-based rate of recovery was analyzed.
  
  
  RESULTS
  Thirty-three (73%) of the patients had progression of ossification of the posterior longitudinal ligament after laminoplasty. Progression was frequent in patients with the mixed type of ossification and in those with the continuous type, whereas it was rare in patients with the segmental type. The patients with progression of the ossification were significantly younger than those without progression (p = 0.018). The Japanese Orthopaedic Association score improved rapidly within one year and continued to improve up to five years after surgery. The score tended to decrease thereafter. For thirteen patients, the score had worsened at the time of the latest follow-up. Three patients had neurological deterioration following an increase in the thickness of the ossification.
  
  
  CONCLUSIONS
  Progression of ossification of the posterior longitudinal ligament was often observed during the long-term follow-up period after laminoplasty. Young patients with mixed and continuous types of ossification had the greatest risk for progression. Preventive measures, such as the use of a wider laminar opening during the laminoplasty, should be considered for patients who are at risk for progression of ossification.
authors.affiliation: Department of Orthopaedic Surgery, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan. zenji@ms.toyama-mpu.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Kawaguchi
authors.forename: M
authors.initials: M
authors.lastname: Kanamori
authors.forename: H
authors.initials: H
authors.lastname: Ishihara
authors.forename: H
authors.initials: H
authors.lastname: Nakamura
authors.forename: K
authors.initials: K
authors.lastname: Sugimori
authors.forename: H
authors.initials: H
authors.lastname: Tsuji
authors.forename: T
authors.initials: T
authors.lastname: Kimura
mesh_terms: D000328:Adult; D002574:Cervical Vertebrae / Q000601:surgery*; D018450:Disease Progression; D005500:Follow-Up Studies; D006801:Humans; D017846:Longitudinal Ligaments / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009999:Ossification, Heterotopic / Q000473:pathology*; D011183:Postoperative Complications / Q000473:pathology*; D012307:Risk Factors; D013117:Spinal Cord Compression / Q000150:complications / Q000601:surgery*; D018709:Statistics, Nonparametric