Document Detail

Assessment of pedicle screw pullout strength based on various screw designs and bone densities-an ex vivo biomechanical study.
MedLine Citation:
PMID:  22336467     Owner:  NLM     Status:  Publisher    
BACKGROUND CONTEXT: The pedicle screw fixation system has been used for various spinal disorders. Many studies have been conducted on the fixation ability of the pedicle screw, but variable results have been reported based on bone qualities, pedicle screw properties, insertion techniques, and experimental methods. STUDY DESIGN: An experimental and biomechanical study. PURPOSE: To evaluate the geometric factors of screws affecting fixation ability after assessing pullout strength based on various pedicle screw designs and different bone densities. METHODS: Nine types of pedicle screws were prepared according to the outer diameter shape (cylindrical or conical), the inner diameter shape (cylindrical or conical), and thread shape (V shape, buttress shape, and square shape). The pedicle screws were inserted into standardized polyurethane foams of Grades 5, 15, and 20. The pullout strength of each pedicle screw was determined using an MTS 858 machine (Material Testing System Corp., Minneapolis, MN, USA), and the results were analyzed statistically. RESULTS: Pullout strength based on the shape of thread was the highest in the V shape and lowest in the square shape for all foam grades (p<.05). The outer cylindrical and inner conical shape of pedicle screw showed the highest pullout strength in Grades 5 and 15 foam (p<.05). An outer cylindrical and inner conical shape with a V-shaped thread showed the highest pullout strength in all foam grades (p<.05). CONCLUSIONS: Pedicle screw with an outer cylindrical and inner conical configuration with a V-shaped thread may have maximum pullout strength, regardless of bone density.
Young-Yul Kim; Woo-Sung Choi; Kee-Won Rhyu
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-2-13
Journal Detail:
Title:  The spine journal : official journal of the North American Spine Society     Volume:  -     ISSN:  1878-1632     ISO Abbreviation:  -     Publication Date:  2012 Feb 
Date Detail:
Created Date:  2012-2-16     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101130732     Medline TA:  Spine J     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012 Elsevier Inc. All rights reserved.
Department of Orthopedic Surgery, Daejeon St. Mary's Hospital, The Catholic University of Korea, 64 Daeheung-ro, Daejeon, 301-723, Korea.
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