title: Multicenter study investigating the postoperative progression of ossification of the posterior longitudinal ligament in the cervical spine: a new computer-assisted measurement.
abstract: OBJECTIVE
  Ossification of the posterior longitudinal ligament (OPLL) often progresses after surgery, and this may cause late-onset neurological deterioration. There have been few studies, however, to clarify any correlation between progression and clinical outcome, partly because of the lack of studies involving reliable and reproducible methods by which detection of progression is made possible. The authors conducted a multicenter study to investigate the occurrence of postoperative progression and to elucidate the possible risk factors in a large-scale patient population, and a novel computer-assisted measurement method was used to provide the basis for future clinical studies.
  
  
  METHODS
  The authors analyzed lateral plain radiographs obtained immediately and at 1 and 2 years after surgery in 131 patients who underwent posterior decompression at 13 institutions. The x-ray films were transformed via scanner into digital images; the length and thickness of ossifications were measured using a new computer-assisted measurement system, and the incidence of progression was determined. Odds ratios for progression according to age group and types of OPLL were determined and compared to elucidate significant risk factors of progression.
  
  
  CONCLUSIONS
  This is the first multicenter study to investigate the incidence of OPLL progression after posterior decompression by using a standardized measurement method. The rate of postoperative progression at 2 years was 56.5%, which was comparable with results reported in other studies. Progression occurred more frequently in younger-age rather than in older-age patient populations at both 1 and 2 years postoperatively. Mixed-type and continuous-type OPLL progressed more frequently than the segmental-type lesion at 2 years. The results of the present study could serve as basis for future studies to assess the efficacy of drug therapy to prevent OPLL progression.
authors.affiliation: Department of Orthopedic Surgery, School of Medicine, Keio University, Tokyo, Japan. kchiba@sc.itc.keio.ac.jp
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Chiba
authors.forename: Itsuo
authors.initials: I
authors.lastname: Yamamoto
authors.forename: Hisashi
authors.initials: H
authors.lastname: Hirabayashi
authors.forename: Motoki
authors.initials: M
authors.lastname: Iwasaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Goto
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yonenobu
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Toyama
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002574:Cervical Vertebrae / Q000601:surgery; D019299:Decompression, Surgical; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007796:Laminectomy; D008297:Male; D008875:Middle Aged; D017887:Ossification of Posterior Longitudinal Ligament / Q000000981:diagnostic imaging* / Q000209:etiology* / Q000601:surgery; D011183:Postoperative Complications; D011859:Radiography