Correlation of routine radiographs with a second surgical look at lumbar fusions

Controversy centers on the determination of surgical fusion in lumbar spinal patients. Whet method best determines the nature af surgical arthrodesis remains unanswared. Numerous atudieshavc investigated the accuracy of different radio logic? tests. Although the host method has not beDn determined., plain radiography is certainly the most widely used in many csn'tors and reported in scientific articles. In moat of the liieraturo a poor agreement between radiographic interpretation and surgical findings was observed. The main reasons seemed to be the lack of an acsorate method to assess the radiographs. The authors rely on a radiolegist or spi n a I surg eon to esti mate the success of bony fusion by reviewing a two-dimensionaI radiograph. The p u rpoae of th Is study was to datormino the eccu racy of plain radiographs to predict the presence of a surgical fusion. Forty-nine patients underwent fusion site exploration In the course of hardware removal. Ad patients had a one- or two-lavol posterolateral fusion and posterior lumbar interbody fusion with pedicle straw/link rod Instrumentation. Immediate prenpgrative ameroposteriorand lateral radiographs were taken before hardware removal that included both visual assessment and a kocher mechanical test, Two spinal surgeons and two musculoskeletal radiologists blindly Judged the preoperative radiographs as to the absolute presence or absence of successful arthrodesis. A second review was repeated at 3 months. The overall agreement between radiographic assessment and actual surgical findings was 69%. The range among observers was 57-77%. Ttie overall false positive rate was 4-2% (0-75%), while the false-negative rate was 29%(20-51%). Success of observed surgical arthrodesis at the time of thB second look was 90% and this number was used as the standard in the agreement procoss, In comparing the radiographic observations with the surgical findings it is suggested that in one oF five cases the plain radiographs underesllmatethe degreoof fusion. This finding agmes wilhthe authors' knowledge of osteoid and mlneralfied bone. The premineraliiedosteoid may be functionally fused, but appear radiolucent on radiographic film. Onco solid trabecular bony bridging occurs radiographic identification of fusion is easier Lo determine.