Bone Resorption Around Pedicle Screws After Pedicle Screw Plate Fixation

ABSTRACT

PURPOSE: To determine the frequency, level, distribution, onset, and pattern of progression of bone resorption that occurring around pedicle screws after pedicle screw plate fixation. MATERIALS AND METHODS: Bone resorption around 902 pedicle screws was analyzed in post-operative, and follow-up radiographs obtained from 156 patients who underwent pedicle screw plate fixation. To determine the resorption degree, categorized arbitrarily as grade 1 (less than 1 mm), grade 2 (1 mm or more, but less than 2 mm), or grade 3 (2 mm or more), the width of radiolucent zones was measured. In 39 patients in whom resorption was graded 1, 2, or 3, the pattern of progression of 78 screws was evaluated. RESUTLS Resorption occurred around 78 (8.6%) screws in 39 (25%) patients, 26 of whom had more than one lesion. For 99% of screws, there was evidance of resorption within 12 weeks of pedicle screw plate fixation. During follow-up, 61.5% of screws (48/78) remained stable, while 38.5% (30 screws) showed progression to higher grades. The possibility of progression to a higher grade is less when the initial grade is lower. CONCLUSION: An understanding of the radiographic patterns of bone resorption is useful for monitoring a patient after pedicle screw plate fixation.