Flat Feet Research Today is a free monthly online journal that collates and summarizes the latest research about Flat Feet, including details on flatfoot, fallen arches, children, treatment, arthrodesis. | ||||||||
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Clinical course and significance of the clear zone around the pedicle screws in the lumbar degenerative disease.Tokuhashi Y, Matsuzaki H, Oda H, Uei H Department of Orthopaedic Surgery, Nihon University School of Medicine, Itabashi-ku, Tokyo, Japan. ytoku@med.nihon-u.ac.jp STUDY DESIGN: A retrospective study. OBJECTIVE: To report the clinical course and significance of postoperative radiolucent zones around pedicle screws. SUMMARY OF BACKGROUND DATA: Radiolucent zones around pedicle screws have been considered to indicate loss of fixation, delayed union, or pseudarthrosis. Few reports have described the course and significance of them. METHODS: Plain radiographs were evaluated from 190 patients with pedicle screw fixation. When 1 mm or greater circumferential lucency was confirmed around a screw on plain radiographs from 2 or more directions, the patient was judged as clear-zone positive. The course of clear-zone positivity was investigated and the relationships between clear-zone positivity and the following items were investigated: (1) number of levels fused, (2) bone union, (3) posterolateral lumbar fusion versus posterior lumbar interbody fusion, (4) clinical results, (5) bone mineral density, and (6) screw types. RESULTS: Although clear zones were observed in 78 patients 6 months after surgery, the clear zone-positive rate decreased over time and the progression of bone union and the number of patients decreased to 28 at the final follow-up 3 years or more after surgery. Interobserver and intraobserver coefficient of variability in clear-zone judgment was over 0.86, and agreement was over 96%. At final follow-up, pseudarthrosis was found in 15 patients. Although the predictive value of the positive test for the presence of clear zones for pseudarthrosis at final follow-up was 0.50, sensitivity was 0.93 and specificity was 0.92. There were significant differences in the clear zone-positive rate in the number of levels fused and bone mineral density among the investigated items. CONCLUSION: As approximately two thirds of the clear zones disappeared over time, the presence of clear zones did not necessarily mean pseudarthrosis. However, clear zones persisting for 2 years or longer after surgery are a great risk of pseudarthrosis. Therefore, careful observation of clear zones around pedicle screws is of great significance as an evaluation of bone union. Published 11 April 2008 in Spine, 33(8): 903-8.
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