{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,30]],"date-time":"2026-10-30T22:08:12Z","timestamp":1793398092463,"version":"4.5.0"},"reference-count":25,"publisher":"Asian Spine Journal (ASJ)","issue":"5","license":[{"start":{"date-parts":[[2020,12,28]],"date-time":"2020-12-28T00:00:00Z","timestamp":1609113600000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"content-domain":{"domain":["asianspinejournal.org"],"crossmark-restriction":true},"short-container-title":["Asian Spine J"],"published-print":{"date-parts":[[2021,10,31]]},"abstract":"<jats:p>Study Design: Biomechanical study.Purpose: To quantitatively investigate the effect of screw size on screw fixation in osteoporotic vertebrae with finite element analysis (FEA)Overview of Literature: Osteoporosis poses a challenge in spinal instrumentation; however, the selection of screw size is directly related to fixation and is closely dependent on each surgeon\u2019s experience and preference.Methods: Total 1,200 nonlinear FEA with various screw diameters (4.5\u20137.5 mm) and lengths (30\u201350 mm) were performed on 25 patients (seven men and 18 women; mean age, 75.2\u00b110.8 years) with osteoporosis. The axial pullout strength, and the vertebral fixation strength of a paired-screw construct against flexion, extension, lateral bending, and axial rotation were examined. Thereafter, we calculated the equivalent stress of the bone-screw interface during nondestructive loading. Then, using diameter parameters (screw diameter or screw fitness in the pedicle [%fill]), and length parameters (screw length or screw depth in the vertebral body [%length]), multiple regression analyses were performed in order to evaluate the factors affecting various fixations.Results: Larger diameter and longer screws significantly increased the pullout strength and vertebral fixation strength; further, they decreased the equivalent stress around the screws. Multiple regression analyses showed that the actual screw diameter and %length were factors that had a stronger effect on the fixation strength than %fill and the actual screw length. Screw diameter had a greater effect on the resistance to screw pullout and flexion and extension loading (\u03b2 =0.38\u20130.43, p &lt;0.01); while the %length had a greater effect on resistance to lateral bending and axial rotation loading (\u03b2 =0.25\u20130.36, p &lt;0.01) as well as mechanical stress of the bone-screw interface (\u03b2 =\u22120.42, p &lt;0.01).Conclusions: The screw size should be determined based on the biomechanical behavior of the screws, type of mechanical force applied on the corresponding vertebra, and anatomical limitations.<\/jats:p>","DOI":"10.31616\/asj.2020.0353","type":"journal-article","created":{"date-parts":[[2020,12,24]],"date-time":"2020-12-24T07:03:21Z","timestamp":1608793401000},"page":"566-574","update-policy":"https:\/\/doi.org\/10.31616\/crossmark_policy","source":"Crossref","is-referenced-by-count":85,"title":["Impact of Screw Diameter and Length on Pedicle Screw Fixation Strength in Osteoporotic Vertebrae: A Finite Element 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