title: The Effect of Lumbar Lordosis on Screw Loosening in Dynesys Dynamic Stabilization: Four-Year Follow-Up with Computed Tomography.
abstract: BACKGROUND
  This study aimed to evaluate the effects of Dynesys dynamic stabilization (DDS) on clinical and radiographic outcomes, including spinal pelvic alignment.
  
  
  METHODS
  Consecutive patients who underwent 1- or 2-level DDS for lumbar spondylosis, mild degenerative spondylolisthesis, or degenerative disc disease were included. Clinical outcomes were evaluated by Visual Analogue Scale for back and leg pain, Oswestry Disability Index, and the Japanese Orthopedic Association scores. Radiographic outcomes were assessed by radiographs and computed tomography. Pelvic incidence and lumbar lordosis (LL) were also compared.
  
  
  RESULTS
  In 206 patients with an average follow-up of 51.1 ± 20.8 months, there were 87 screws (8.2%) in 42 patients (20.4%) that were loose. All clinical outcomes improved at each time point after operation. Patients with loosened screws were 45 years older. Furthermore, there was a higher risk of screw loosening in DDS involving S1, and these patients were more likely to have loosened screws if the LL failed to increase after the operation.
  
  
  CONCLUSIONS
  The DDS screw loosening rate was overall 8.2% per screw and 20.4% per patient at more than 4 years of follow-up. Older patients, S1 involvement, and those patients who failed to gain LL postoperatively were at higher risk of screw loosening.
authors.affiliation: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, 17F, No. 201, Shih-Pai Road, Sec. 2, Beitou, Taipei 11217, Taiwan; School of Medicine, National Yang-Ming University, Taiwan.
authors.forename: Chao-Hung
authors.initials: CH
authors.lastname: Kuo
authors.affiliation: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, 17F, No. 201, Shih-Pai Road, Sec. 2, Beitou, Taipei 11217, Taiwan; School of Medicine, National Yang-Ming University, Taiwan.
authors.forename: Peng-Yuan
authors.initials: PY
authors.lastname: Chang
authors.affiliation: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, 17F, No. 201, Shih-Pai Road, Sec. 2, Beitou, Taipei 11217, Taiwan; School of Medicine, National Yang-Ming University, Taiwan; Molecular Medicine Program, Taiwan International Graduate Program (TIGP), Academia Sinica, Taipei, Taiwan.
authors.forename: Tsung-Hsi
authors.initials: TH
authors.lastname: Tu
authors.affiliation: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, 17F, No. 201, Shih-Pai Road, Sec. 2, Beitou, Taipei 11217, Taiwan; School of Medicine, National Yang-Ming University, Taiwan.
authors.forename: Li-Yu
authors.initials: LY
authors.lastname: Fay
authors.affiliation: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, 17F, No. 201, Shih-Pai Road, Sec. 2, Beitou, Taipei 11217, Taiwan; School of Medicine, National Yang-Ming University, Taiwan.
authors.forename: Hsuan-Kan
authors.initials: HK
authors.lastname: Chang
authors.affiliation: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, 17F, No. 201, Shih-Pai Road, Sec. 2, Beitou, Taipei 11217, Taiwan; School of Medicine, National Yang-Ming University, Taiwan.
authors.forename: Jau-Ching
authors.initials: JC
authors.lastname: Wu
authors.affiliation: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, 17F, No. 201, Shih-Pai Road, Sec. 2, Beitou, Taipei 11217, Taiwan; School of Medicine, National Yang-Ming University, Taiwan.
authors.forename: Wen-Cheng
authors.initials: WC
authors.lastname: Huang
authors.affiliation: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, 17F, No. 201, Shih-Pai Road, Sec. 2, Beitou, Taipei 11217, Taiwan; School of Medicine, National Yang-Ming University, Taiwan; Institute of Pharmacology, National Yang-Ming University, Taiwan.
authors.forename: Henrich
authors.initials: H
authors.lastname: Cheng
mesh_terms: D000328:Adult; D001863:Bone Screws; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000503:physiopathology / Q000601:surgery*; D008141:Lordosis / Q000473:pathology / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D013116:Spinal Cord / Q000473:pathology / Q000601:surgery*