title: Bone union and remodelling of the non-ossified segment in thoracic ossification of the posterior longitudinal ligament after posterior decompression and fusion surgery.
abstract: OBJECTIVE
  The motion at the non-ossified segment of the ossification of the posterior longitudinal ligament (OPLL) is thought to be highly correlated to aggravation of symptoms of myelopathy. The rationale for posterior decompression with instrumented fusion (PDF) surgery is to limit the motion of the non-ossified segment of OPLL by stabilization. The purpose of the present study was to elucidate the course of bone union and remodelling of the non-ossified segment of thoracic OPLL (T-OPLL) after PDF surgery.
  
  
  METHODS
  A total of 29 patients who underwent PDF surgery for T-OPLL were included in this study. We measured the thickness of the OPLLs by determining the thickest part of the OPLL in the sagittal multi-planer reconstruction CT images pre- and post-operatively. Five experienced spine surgeons independently performed CT measurements of OPLL thickness twice. Japanese Orthopaedic Association score for thoracic myelopathy was measured as clinical outcome measure.
  
  
  RESULTS
  Non-ossified segment of OPLLs fused in 24 out of 29 (82.8 %) patients. The average thickness of the OPLL at its thickest segment was 8.0 mm and decreased to 7.3 mm at final follow-up. The decrease in ossification thickness was significantly larger in the patients who showed fusion of non-ossified segments of OPLL compared with that in the patients did not show fusion. There was no significant correlation between the clinical outcome and the decrease in thickness of the OPLLs.
  
  
  CONCLUSIONS
  The results of this study showed that remodelling of the OPLLs, following fusion of non-ossified segment of OPLLs, resulted in a decreased OPLL thickness, with potential for a reduction of spinal cord compression.
authors: Department of Orthopaedic Surgery, Chiba University Graduate School of Medicine, 1-8-1, Inohana, Chuo-Ku, Chiba, 260-8670, Japan. masaokod@gmail.com.
authors: Masao
authors: M
authors: Koda
authors: Department of Orthopaedic Surgery, Chiba University Graduate School of Medicine, 1-8-1, Inohana, Chuo-Ku, Chiba, 260-8670, Japan.
authors: Takeo
authors: T
authors: Furuya
authors: Department of Orthopaedic Surgery, Chiba University Graduate School of Medicine, 1-8-1, Inohana, Chuo-Ku, Chiba, 260-8670, Japan.
authors: Akihiko
authors: A
authors: Okawa
authors: Department of Orthopaedic Surgery, Chiba University Graduate School of Medicine, 1-8-1, Inohana, Chuo-Ku, Chiba, 260-8670, Japan.
authors: Masaaki
authors: M
authors: Aramomi
authors: Department of Orthopaedic Surgery, Chiba University Graduate School of Medicine, 1-8-1, Inohana, Chuo-Ku, Chiba, 260-8670, Japan.
authors: Taigo
authors: T
authors: Inada
authors: Department of Orthopaedic Surgery, Chiba University Graduate School of Medicine, 1-8-1, Inohana, Chuo-Ku, Chiba, 260-8670, Japan.
authors: Koshiro
authors: K
authors: Kamiya
authors: Department of Orthopaedic Surgery, Chiba University Graduate School of Medicine, 1-8-1, Inohana, Chuo-Ku, Chiba, 260-8670, Japan.
authors: Mitsutoshi
authors: M
authors: Ota
authors: Department of Orthopaedic Surgery, Chiba University Graduate School of Medicine, 1-8-1, Inohana, Chuo-Ku, Chiba, 260-8670, Japan.
authors: Satoshi
authors: S
authors: Maki
authors: Department of Orthopaedic Surgery, Chiba University Graduate School of Medicine, 1-8-1, Inohana, Chuo-Ku, Chiba, 260-8670, Japan.
authors: Osamu
authors: O
authors: Ikeda
authors: Department of Orthopaedic Surgery, Chiba University Graduate School of Medicine, 1-8-1, Inohana, Chuo-Ku, Chiba, 260-8670, Japan.
authors: Kazuhisa
authors: K
authors: Takahashi
authors: Department of Orthopaedic Surgery, Chiba Aoba Municipal Hospital, Chiba, Japan.
authors: Chikato
authors: C
authors: Mannoji
authors: Department of Orthopaedic Surgery, University of Tsukuba, Tsukuba, Japan.
authors: Masashi
authors: M
authors: Yamazaki
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D019299:Decompression, Surgical / Q000379:methods*; D005260:Female; D006801:Humans; D017846:Longitudinal Ligaments / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D017887:Ossification of Posterior Longitudinal Ligament / Q000150:complications / Q000601:surgery*; D065289:Pedicle Screws; D012189:Retrospective Studies; D013117:Spinal Cord Compression / Q000209:etiology / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D055815:Young Adult
keywords: Bone union; Fusion surgery; OPLL; Remodelling