title: Cage migration after transforaminal lumbar interbody fusion and factors related to it.
abstract: OBJECTIVE
  To review and analyze cage migration and related risk factors in patients who have undergone transforaminal lumbar interbody fusion (TLIF).
  
  
  METHODS
  A retrospective study was conducted to review the complications of cage migration in 512 patients who had undergone a TLIF procedure from January 2010 to June 2011 in five spinal centers. In all, 263 men and 249 women with a mean age of 54.7 years were included. All patients were followed up at 3, 6 and 12 months after the procedure. The clinical outcomes were evaluated by visual analogue scores, the Oswestry disability index, plain radiography and three-dimensional CT scanning to analyze the incidence of, and risk factors related to, cage migration.
  
  
  RESULTS
  Cage migration was found in 6 of the 512 patients (1.17%). Significant differences were found between all pairs of centers. Different shapes and sizes of cages had different incidences of migration. Analysis showed that rectangular-shaped cages had a significantly greater incidence of cage migration (3.11%, 5/161) than did kidney-shaped cages (0.28%, 1/351; P < 0.05). Small cages had a tendency to more frequent post-operative cage migration (5.13%, 4/78) than did large cages (0.46%, 2/434; P < 0.05). Double segment TLIF cages migrated more frequently (5.75%, 5/87) than did mono-segment cages (0.24%, 1/425; P < 0.05)). Furthermore, when the adjacent endplates were of linear type, the cages migrated much more frequently (3.50%) than when they were of concave-concave type (0.27%; P < 0.05).
  
  
  CONCLUSIONS
  Cage size, shape, number of fused segments and adjacent endplate shape might be risk factors for cage migration in addition to surgical technique, disc height and bone mineral density.
authors.affiliation: Department of Orthopaedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China. zhaodong6811@yahoo.com.cn
authors.forename: Feng-dong
authors.initials: FD
authors.lastname: Zhao
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
authors.forename: Zhi
authors.initials: Z
authors.lastname: Shan
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.forename: Hai-xiao
authors.initials: HX
authors.lastname: Chen
authors.forename: Zheng-hua
authors.initials: ZH
authors.lastname: Hong
authors.forename: Yu
authors.initials: Y
authors.lastname: Qian
authors.forename: Deng-wei
authors.initials: DW
authors.lastname: He
authors.forename: Shun-wu
authors.initials: SW
authors.lastname: Fan
mesh_terms: D004867:Equipment Design; D005260:Female; D005548:Foreign-Body Migration / Q000209:etiology*; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009984:Orthopedic Fixation Devices / Q000009:adverse effects*; D012187:Retroperitoneal Space; D012189:Retrospective Studies; D012307:Risk Factors; D013115:Spinal Canal; D013123:Spinal Fusion / Q000009:adverse effects / Q000295:instrumentation*; D013130:Spinal Stenosis / Q000601:surgery*; D013168:Spondylolisthesis / Q000601:surgery*