title: Radiological comparison of instrumented posterior lumbar interbody fusion with one or two closed-box plasmapore coated titanium cages: follow-up study over more than seven years.
abstract: METHODS
  A retrospective clinical study with a follow-up of more than 7 years was conducted.
  
  
  OBJECTIVE
  To compare interbody fusion, segmental lordosis and changes in disc and foramen height in patients who had received instrumented posterior lumbar interbody fusion (PLIF) with 1 or 2 closed-box titanium cages.
  
  
  BACKGROUND
  PLIF using 2 cages is a popular surgical method for treating degenerative lumbar spinal diseases. Implantation of a single cage in instrumented PLIF is still controversial.
  
  
  METHODS
  From 1994 to 1997, 46 patients with degenerative lumbar spinal disease underwent single-level instrumented PLIF surgery using 1 (n = 22) or 2 (n = 24) interbody rectangular-shaped titanium blocks coated with Plasmapore (Prospace, B. Braun Aesculap AG, Tuttlingen). Mean follow-up was 8 years, ranging from 7 to 10 years. Anteroposterior and lateral radiographs of the patients were taken immediately after surgery and at the last follow-up examination. Segmental stability, change in segmental height, foramen height, and segmental lordosis were evaluated in both groups.
  
  
  RESULTS
  Eight years after surgery, segmental stability (1-cage: 95.5%; 2 cages: 95.8%; P > 0.05), change in segmental height (1-cage: -1.9% +/- 3.7%; 2-cage: -2.4% +/- 3.6%; P > 0.05), foramen height (1-cage: -3.7% +/- 9.9%; 2-cage: -6.6% +/- 6.5%; P > 0.05) and segmental lordosis (1-cage: -2.4 degrees +/- 4.8; 2-cage -1.0 degrees +/- 4.0; P > 0.05) did not differ significantly between the 2 groups. Due to adjacent segment syndrome, 3 patients with a previous 2-cage PLIF received additional fusion surgery.
  
  
  CONCLUSIONS
  In the long-term, instrumented PLIF with a single closed-box titanium cage shows similar radiologic results compared to fusion with 2 titanium cages. Implantation of a single titanium closed-box cage in an instrumented PLIF seems to be adequate in case of degenerative lumbar spinal disease.
authors.affiliation: Universitätsklinikum Charité-Campus Virchow-Klinikum, Augustenburger Platz, Berlin, Germany. stefan.kroppenstedt@charite.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Kroppenstedt
authors.forename: Martin
authors.initials: M
authors.lastname: Gulde
authors.forename: Robert
authors.initials: R
authors.lastname: Schönmayr