title: Pathogenesis of myelopathy in patients with ossification of the posterior longitudinal ligament.
abstract: OBJECTIVE
  The goal of this study was to clarify the pathogenesis of myelopathy in patients with ossification of the posterior longitudinal ligament (OPLL) based on the relationship between static compression factors and dynamic factors.
  
  
  METHODS
  There was a total of 247 patients, including 167 patients who were conservatively followed for a mean of 11 years and 2 months and 80 patients who had myelopathy at initial consultation and underwent surgery. The changes in clinical symptoms associated with OPLL in the cervical spine were examined periodically. During the natural course of OPLL in the cervical spine, 37 (22%) of 167 patients developed or suffered aggravated spinal symptoms. All of the patients with a space available for the spinal cord (SAC) less than 6 mm suffered myelopathy, whereas the patients with an SAC diameter of 14 mm or greater did not. No correlation was found between the presence or absence of myelopathy in patients whose SAC diameter ranged from 6 mm to less than 14 mm. In patients with myelopathy whose minimal SAC diameter ranged from 6 mm to less than 14 mm, the range of motion of the cervical spine was significantly greater.
  
  
  CONCLUSIONS
  These results indicate that pathological compression by the ossified ligament above a certain critical point may be the most significant factor in inducing myelopathy, whereas below that point dynamic factors may be largely involved in inducing myelopathy.
authors.affiliation: Department of Orthopaedic Surgery, Faculty of Medicine, Kagoshima University, Japan. shunji@m.kufm.kagoshima-u.ac.jp
authors.forename: Shunji
authors.initials: S
authors.lastname: Matsunaga
authors.forename: Makoto
authors.initials: M
authors.lastname: Kukita
authors.forename: Kyoji
authors.initials: K
authors.lastname: Hayashi
authors.forename: Reiko
authors.initials: R
authors.lastname: Shinkura
authors.forename: Chihaya
authors.initials: C
authors.lastname: Koriyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Sakou
authors.forename: Setsuro
authors.initials: S
authors.lastname: Komiya
mesh_terms: D000368:Aged; D002574:Cervical Vertebrae / Q000503:physiopathology; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures; D017887:Ossification of Posterior Longitudinal Ligament / Q000150:complications* / Q000628:therapy; D011446:Prospective Studies; D016059:Range of Motion, Articular; D013118:Spinal Cord Diseases / Q000209:etiology* / Q000503:physiopathology