title: Posterior migration of fusion cages in degenerative lumbar disease treated with transforaminal lumbar interbody fusion: a report of three patients.
abstract: METHODS
  A case report of 3 patients with posterior migration of bullet-shaped fusion cages after transforaminal lumbar interbody fusion (TLIF). One patient required emergency revision surgery; the other 2 patients are being observed during conservative treatment.
  
  
  OBJECTIVE
  To review cases of posterior migration of fusion cages and report ensuing clinical courses.
  
  
  BACKGROUND
  TLIF is a commonly used procedure; however, there are few reports describing cage migration after the procedure. In most cases, when posterior cage migration follows posterior lumbar interbody fusion, emergency revision surgery is required. One recent study reported a case of posterior cage migration after TLIF, which was treated conservatively.
  
  
  METHODS
  Posterior migration of the bullet-shaped fusion cages occurred 1 to 2 months after TLIF in 3 patients. One of the 3 patients had isthmic spondylolisthesis treated by TLIF with bilateral pedicle screw fixation. The other 2 patients had degenerative scoliosis and were treated by TLIF with unilateral pedicle screw fixation.
  
  
  RESULTS
  The patient with isthmic spondylolisthesis required revision surgery because the migrated cage caused nerve root irritation. The migrated cage was removed and a large-sized cage was employed to achieve stability. The other 2 patients had no pathologic symptoms after the posterior migration of the cage and were treated conservatively and observed.
  
  
  CONCLUSIONS
  Revision surgery after TLIF appears relatively safe because the migrated cage tends to locate more laterally than in patients with cage migration after posterior lumbar interbody fusion. Cage migration subsequent to TLIF may not cause compression of neural tissues, so conservative treatment may suffice for these patients. Unilateral pedicle screw fixation may not provide sufficient stability to prevent cage migration in patients with degenerative scoliosis. Further study is needed to clarify surgical indications for unilateral pedicle screw fixation in TLIF.
authors.affiliation: Department of Orthopedic Surgery, Chiba Rosai Hospital, 2-16 Tatsumidai-higashi, Ichihara, Chiba, Japan. yasuaoki@h6.dion.ne.jp
authors.forename: Yasuchika
authors.initials: Y
authors.lastname: Aoki
authors.forename: Masatsune
authors.initials: M
authors.lastname: Yamagata
authors.forename: Fumitake
authors.initials: F
authors.lastname: Nakajima
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Ikeda
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D000368:Aged; D001863:Bone Screws; D005548:Foreign-Body Migration / Q000175:diagnosis* / Q000601:surgery; D006801:Humans; D016268:Internal Fixators; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D011859:Radiography; D012086:Reoperation; D012600:Scoliosis / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D013168:Spondylolisthesis / Q000601:surgery*