Comparison of angled versus AP view radiography for post-operative evaluation of lumbosacral spondylolisthesis: a cadaveric study

Background  The objective of this study was to investigate if angled radiographic views of the L5-S1 junction result in quantitatively better images in patients with lumbosacral spondylolisthesis compared to conventional AP view. Methods  Grade I lumbosacral spondylolisthesis was simulated in cadaveric specimens and repaired using pedicle screws and posterolateral bone grafting. Angled view AP radiographs were taken at different angles and analyzed at both grade I spondylolisthesis and complete reduction (to normal). Results  The results indicated that angled view radiographs provide better visualization of intervertebral disc height, area, and posterolateral bone graft area compared with true AP views. The optimal view was at 40° for grade I spondylolisthesis, and at 25°–35° for complete reduction. Conclusion  In addition to the dynamic radiographs currently used for evaluation of patients post-spondylolisthesis repair, an additional angled view radiograph (at 40° or 25–35°) is recommended to evaluate intervertebral disc height, intervertebral area, bone graft area, and pedicle screw position.