title: Radiologic evaluation after posterior instrumented surgery for thoracic ossification of the posterior longitudinal ligament: union between rostral and caudal ossifications.
abstract: METHODS
  Retrospective clinical study.
  
  
  OBJECTIVE
  To investigate, using multislice CT images, how thoracic ossification of the posterior longitudinal ligament (OPLL) changes with time after thoracic posterior fusion surgery.
  
  
  BACKGROUND
  Few studies have evaluated thoracic OPLL preoperatively and post using computed tomography (CT).
  
  
  METHODS
  The subjects included 19 patients (7 men and 12 women) with an average age at surgery of 52 years (38-66 y) who underwent indirect posterior decompression with corrective fusion and instrumentation at our institute. Minimum follow-up period was 1 year, and averaged 3 years 10 months (12-120 mo). Using CT images, we investigated fusion range, preoperative and postoperative Cobb angles of thoracic fusion levels, intraoperative and postoperative blood loss, operative time, hyperintense areas on preoperative MRI of thoracic spine and thickness of the OPLL on the reconstructed sagittal, multislice CT images taken before the operation and at 3 months, 6 months and 1 year after surgery. The basic fusion area was 3 vertebrae above and below the OPLL lesion.
  
  
  RESULTS
  The mean operative time was 7 hours and 48 min (4 h 39 min-10 h 28 min), and blood loss was 1631 mL (160-11,731 mL). Intramedullary signal intensity change on magnetic resonance images was observed at the most severe ossification area in 18 patients. Interestingly, the rostral and caudal ossification regions of the OPLLs, as seen on sagittal CT images, were discontinuous across the disk space in all patients. Postoperatively, the discontinuous segments connected in all patients without progression of OPLL thickness by 5.1 months on average.
  
  
  CONCLUSIONS
  All patients needing surgery had discontinuity across the disk space between the rostral and caudal ossified lesions as seen on CT. This discontinuity was considered to be the main reason for the myelopathy because a high-intensity area on magnetic resonance imaging was seen in 18 of 19 patients at the same level. Rigid fixation with instrumentation may allow the discontinuous segments to connect in patients without a concomitant thickening of the OPLL.
authors.affiliation: From the Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Ando
authors.forename: Shiro
authors.initials: S
authors.lastname: Imagama
authors.forename: Zenya
authors.initials: Z
authors.lastname: Ito
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Junichi
authors.initials: J
authors.lastname: Ukai
authors.forename: Akio
authors.initials: A
authors.lastname: Muramoto
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Shinjo
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nakashima
authors.forename: Naoki
authors.initials: N
authors.lastname: Ishiguro
mesh_terms: D000328:Adult; D000368:Aged; D003710:Demography; D005260:Female; D006801:Humans; D017846:Longitudinal Ligaments / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D017887:Ossification of Posterior Longitudinal Ligament / Q000000981:diagnostic imaging* / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery*; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome