title: Polymethylmethacrylate augmentation of pedicle screws increases the initial fixation in osteoporotic spine patients.
abstract: METHODS
  A retrospective comparative study.
  
  
  OBJECTIVE
  To investigate the clinical efficacy of polymethylmethacrylate (PMMA) augmentation in vertebral pseudarthrosis after osteoporotic vertebral fractures.
  
  
  BACKGROUND
  Despite being the most rigid form of posterior instrumentation, pedicle screws sometimes achieve poor initial fixation primarily in patients with osteoporosis. One method for improving pedicle screw fixation in osteoporotic spines is pedicle augmentation using bone cement such as PMMA. Although various biomechanical studies of osteoporotic spines have shown improved pullout strength of pedicle screws augmented with bone cement, there have been few studies that have examined the clinical significance of PMMA augmentation.
  
  
  METHODS
  Thirty-eight patients with posterior fusion using pedicle screws for vertebral pseudarthrosis after osteoporotic vertebral fracture were included in the study. The level of fracture ranged from T7 to L5. The mean follow-up period was 31 months. Patients were divided into 2 groups: those with posterior instrumentation using pedicle screws augmented with PMMA (group C, N=17) and those without PMMA augmentation (group NC, N=21). Clinical and radiographic results for the 2 groups were compared.
  
  
  RESULTS
  With the exception of osteoporotic status, there were no significant differences in the baseline data of the 2 groups. The incidence of clear zones around the pedicle screws was significantly suppressed in group C compared with group NC (29.4% vs. 71.4%). Correction loss was significantly decreased (3 degrees vs. 7.2 degrees) and fusion rate was significantly higher in group C (94.1% vs. 76.1%). Back pain improved in 64.7% of the group C patients. There were no perioperative complications related to the PMMA cement in group C.
  
  
  CONCLUSIONS
  Reinforcement of pedicle screws using PMMA augmentation may be a feasible surgical technique for osteoporotic spines.
authors.affiliation: Department of Orthopaedic Surgery, Niigata City General Hospital, Niigata, Japan.
authors.forename: Kimihiko
authors.initials: K
authors.lastname: Sawakami
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Yamazaki
authors.forename: Seiichi
authors.initials: S
authors.lastname: Ishikawa
authors.forename: Takui
authors.initials: T
authors.lastname: Ito
authors.forename: Kei
authors.initials: K
authors.lastname: Watanabe
authors.forename: Naoto
authors.initials: N
authors.lastname: Endo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001843:Bone Cements; D001863:Bone Screws; D005260:Female; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000601:surgery; D058866:Osteoporotic Fractures / Q000601:surgery*; D019904:Polymethyl Methacrylate; D011542:Pseudarthrosis / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D013131:Spine / Q000601:surgery*; D016896:Treatment Outcome
chemical_list: D001843:Bone Cements; D019904:Polymethyl Methacrylate