Three-dimensional CT imaging in postsurgical "failed back" syndrome.

One hundred consecutive patients with postsurgical "failed back" syndrome (PSFBS) without fusion and 100 patients with PSFBS with fusion were evaluated with direct CT, two-dimensional (2D) multiplanar, and three-dimensional (3D) imaging. In the patients with and without fusion, 3D images were found to best display the following: the surgical procedure and its extent, lateral neural foraminal narrowing, and fractures of the posterior elements. The 3D images enabled optimal demonstration of fusion: solidity, pseudarthrosis, incorporation of transverse processes and facet joints, and transitional syndrome. In the patients without fusion, 3D images provided improved appraisal of surgical results in 31%; it showed additional fracture(s) in 9%, better displayed lateral neural foraminal narrowing in 42%, and showed additional posterior element fractures in 11% as compared to axial and 2D multiplanar reconstructed (MPR) scans. Three-dimensional imaging uncovered incomplete fusion in 17%, transitional syndrome in 13%, and pseudarthrosis in 6%. Thus, the 3D imaging provided additional information over the direct axial and MPR images (2D images) in 56 of 100 patients without fusion and 76 of 100 patients with fusion. At our institution, this imaging modality is now routinely performed in this patient population.