Does a Radiolucent Zone Surrounding the Pedicle Screws mean Nonunion? / 대한정형외과학회잡지

ABSTRACT

PURPOSE: We wanted to retrospectively evaluate the clinical significance of radiolucent zones surrounding the pedicle screws after spinal fusion. MATERIALS AND METHODS: Spinal surgery was performed between May 2003 and December 2005 on elective patients with degenerative lumbar disorders and they underwent transpedicular screw fixation and posterolateral fusion and these patients were the subjects of the study. There were 124 cases with more than 2 years of follow up. Determination of the radiolucent zones around pedicle screws was done using simple x-rays and the cases were divided in to 4 different groups: segmental fixation with short (2 or less segments) or, long (3 or more segments) segmental fixation and those cases with or without sacral fixation. Comparative analysis was done according to osteoporosis, the location of the pedicle screws, the degree of bony-union and fixation of the anterior cortex of the sacrum. RESULTS: Among the 124 cases and 846 pedicle screws, 189 pedicle screws (22%) had radiolucent zones; 151 of the 189 pedicle screws with a radiolucent zone (27%) were in the sacral fixed group, while 38 of the 189 pedicle screws with a radiolucent zone (13%) were in the non-sacral fixed group, and the difference was significant (p=0.001). In the case of anterior cortical fixation in the sacral fixed group and the complete bony-union, the radiolucent zones had a significantly lower incidence, while the group of patients with osteoporosis (a T score lower than -2.5) had a higher incidence of radiolucent zones. CONCLUSION: The radiolucent zones surrounding the pedicle screws after spinal fusion were closely related to spinal fusion with sacral fixation and pseudarthrosis, and these radiolucent zones mostly occurred before complete bony-union. The existence of osteoporosis and the techniques of sacral fixation and many different contributing factors must be considered, and careful monitoring is needed even if the radiolucent zone progressive after complete bony-union.