title: A comparative study on screw loosening in osteoporotic lumbar spine fusion between expandable and conventional pedicle screws.
abstract: BACKGROUND
  The aim of this study is to compare the rate of screw loosening and clinical outcomes of expandable pedicle screws (EPS) with those of conventional pedicle screws (CPS) in patients treated for spinal stenosis (SS) combined with osteoporosis.
  
  
  METHODS
  One hundred and fifty-seven consecutive patients with SS received either EPS fixation (n = 80) or CPS fixation (n = 77) to obtain lumbosacral stabilization. Patients were observed for a minimum of 24 months. Outcome measures included screw loosening, fusion rate, Japanese Orthopaedic Association (JOA) scores and Oswestry disability index (ODI) scoring system, and complications.
  
  
  RESULTS
  In the EPS group, 20 screws became loose (4.1%) in 6 patients (7.5%), and two screws (0.4%) had broken. In the CPS group, 48 screws became loose (12.9%) in 15 patients (19.5%), but no screws were broken. The fusion rate in the EPS group (92.5%) was significantly higher than that of the CPS group (80.5%). The rate of screw loosening in the EPS group (4.1%) was significantly lower than that of the CPS group (12.9%). Six EPS (1.8%) screws were removed. In the EPS group, two screws had broken but without neural complications. Twelve months after surgeries, JOA and ODI scores in the EPS group were significantly improved. There were four cases of dural tears, which healed after corresponding treatment.
  
  
  CONCLUSIONS
  EPS can decrease the risk of screw loosening and achieve better fixation strength and clinical results in osteoporotic lumbar spine fusion.
authors.affiliation: Institute of Orthopedics, Xijing Hospital, The Fourth Military Medical University, Xi'an, Shaanxi Province, People's Republic of China. wuzixiang@fmmu.edu.cn
authors.forename: Zi-xiang
authors.initials: ZX
authors.lastname: Wu
authors.forename: Fu-tai
authors.initials: FT
authors.lastname: Gong
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.forename: Zhen-sheng
authors.initials: ZS
authors.lastname: Ma
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xiong
authors.initials: X
authors.lastname: Zhao
authors.forename: Min
authors.initials: M
authors.lastname: Yang
authors.forename: Wei
authors.initials: W
authors.lastname: Lei
authors.forename: Hong-xun
authors.initials: HX
authors.lastname: Sang
mesh_terms: D000368:Aged; D001863:Bone Screws; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008159:Lumbar Vertebrae / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000150:complications*; D011183:Postoperative Complications; D011475:Prosthesis Failure; D013123:Spinal Fusion / Q000295:instrumentation*; D013130:Spinal Stenosis / Q000150:complications / Q000601:surgery*; D016896:Treatment Outcome