ABSTRACT
PURPOSE: To evaluate the reliance of standard AP radiograph and Ferguson radiograph in assessment of instrumented lumbosacral fusion mass with interobserver and intraobserver reproducibilities. MATERIALS AND METHODS: Postoperative standard AP radiograph and Ferguson radiograph were used to evaluate the fusion mass at the lumbosacral region of 44 consecutive patients who underwent posterolateral L4-S1 or L5-S1 instrumented fusion with pedicle screws & autogenous iliac bone graft. Ferguson radiograph was performed with the x-ray beam oriented toward the cranial portion at 40degree relative to the x-ray table. All observations were performed independently by three observers, blinded to the history, diagnosis, and patient identity. The fusion mass was graded as solid, pseudarthrosis or questionable. A second review was repeated at 2 weeks after index review. Interobserver and intraobserver reproducibilities were analyzed with Fleiss'method. RESULTS: Ferguson radiographs were more reliable than standard AP radiographs in detecting the fusion mass. Kappa values with the interobserver reproducibility were higher in Ferguson radiographs than in the standard AP radiographs. Kappa values with the intraobserver reproducibility of all three observers were higher in Ferguson radiographs than in the standard AP radiographs. The questionable fusion masses in the standard AP radiographs were revealed solid or pseudarthrosis in Ferguson radiographs in 67%. CONCLUSIONS: Ferguson radiograph is a more reliable method than standard AP radiograph in evaluating instrumented posterolateral fusion mass in lumbosacral region.