Postoperative lumbar spine: modified radiographic projections for detection of bone defects in cadavers.

PURPOSE Special radiographic projections were evaluated in two cadaveric specimens for depicting postoperative changes after five different lower lumbar surgical procedures. Available literature concerning special radiographic projections of the lumbar spine is limited. The objective of this study was to establish a special radiographic projection that is useful for depicting postoperative changes after lumbar surgical procedures. MATERIALS AND METHODS Five different procedures were performed on two cadaveric lumbar spines: laminotomy, total laminectomy, foraminotomy, surgical creation of pars interarticularis defect, and partial facetectomy. A series of radiographs, including routine views and combinations of various obliquity and cephalad angulation, were obtained preoperatively and after each operation. Film analysis was done using a four-point rating system to document the degree of visualization of the postsurgical bone defect at each stage of surgery at each lumbar segment. The best projections were determined by summation of the rating scores of the three lumbar segments. The scores of each projection in different procedures were also summed to determine the best view for clinical use. RESULTS The laminotomy defects were more obvious on the shallow-obliquity and low-angulation radiographs. The postoperative changes of total laminectomy were almost equally identified on the AP and lateral views and most of the compound views. The bone changes of foraminotomy were best identified on the 45 degrees routine view. The 30 degrees-15 degrees and 45 degrees-15 degrees compound views were best for depicting a postoperative pars defect. None of the projections delineated the bone changes of partial facetectomy. The 30 degrees-15 degrees compound view had the highest summation of rating scores of the five surgical procedures. CONCLUSION The results of this study suggest that the 30 degrees-15 degrees compound view could be useful for the assessment of the postoperative lumbar spine. Further verification of its value requires a large clinical study.