title: MRI measurement of neuroforaminal dimension at the index and supradjacent levels after anterior lumbar interbody fusion: a prospective study.
abstract: BACKGROUND
  Anterior interbody fusion has previously been demonstrated to increase neuroforaminal height in a cadaveric model using cages. No prior study has prospectively assessed the relative change in magnetic resonance imaging (MRI) demonstrated neuroforaminal dimensions at the index and supradjacent levels, after anterior interbody fusion with a corticocancellous allograft in a series of patients without posterior decompression. The objective of this study was to determine how much foraminal dimension can be increased with indirect foraminal decompression alone via anterior interbody fusion, and to determine the effect of anterior lumbar interbody fusion on the dimensions of the supradjacent neuroforamina.
  
  
  METHODS
  A prospective study comparing pre- and postoperative neuroforaminal dimensions on MRI scan among 26 consecutive patients undergoing anterior lumbar interbody fusion without posterior decompression was performed. We studies 26 consecutive patients (50 index levels) that had undergone anterior interbody fusion followed by posterior pedicle screw fixation without distraction or foraminotomy. We used preoperative and postoperative MRI imaging to assess the foraminal dimensions at each operated level on which the lumbar spine had been operated. The relative indirect foraminal decompression achieved was calculated. The foraminal dimension of the 26 supradjacent untreated levels was measured pre- and postoperatively to serve as a control and to determine any effects after anterior interbody fusion.
  
  
  RESULTS
  In this study, 8 patients underwent 1 level fusion (L5-S1), 12 patients had 2 levels (L4-S1) and 6 patients had 3 levels (L3-S1). The average increase in foraminal dimension was 43.3% (p < 0.05)-19.2% for L3-4, 57.1% for L4-5, and 40.1% for L5-S1. Mean pre- and postoperative supradjacent neuroforaminal dimension measurements were 125.84 mm(2) and 124.89 mm(2), respectively. No significant difference was noted (p > 0.05).
  
  
  CONCLUSIONS
  Anterior interbody fusion with a coriticocancellous allograft can significantly increase neuroforaminal dimension even in the absence of formal posterior distraction or foraminotomy; anterior interbody fusion with a coriticocancellous allograft has little effect on supradjacent neuroforaminal dimensions.
authors: Twin Cities Spine Center, 913 East 26th Street, Minneapolis, MN 55404, USA. woojinchomd@aol.com
authors: Woojin
authors: W
authors: Cho
authors: Mark J
authors: MJ
authors: Sokolowski
authors: Amir A
authors: AA
authors: Mehbod
authors: Francis
authors: F
authors: Denis
authors: Timothy A
authors: TA
authors: Garvey
authors: John
authors: J
authors: Perl
authors: Ensor E
authors: EE
authors: Transfeldt
mesh_terms: D005260:Female; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000175:diagnosis* / Q000601:surgery; D008159:Lumbar Vertebrae; D008279:Magnetic Resonance Imaging; D008297:Male; D011446:Prospective Studies; D013123:Spinal Fusion
keywords: Anterior interbody fusion; Index level; Magnetic resonance imaging; Prospective studies; Supradjacent level