STUDY DESIGN: The pullout strength of unicortical and bicortical screws in thoracic and lumbar vertebral bodies was measured as a function of bone mineral density. OBJECTIVES: To determine the influence of bone mineral density and screw insertion technique on the stability of anterior thoracolumbar spine screw fixation. SUMMARY OF BACKGROUND DATA: No previous study has addressed the specific technique of screw insertion or stability of screw fixation in the anterior spine. METHODS: Fifty-one human thoracic vertebral bodies were tested in pullout with 6.55-mm cancellous screws inserted using unicortical and bicortical techniques. RESULTS: Pullout force increased exponentially with increasing bone mineral density for unicortical and bicortical screws. Bicortical screws were significantly stronger in resisting pullout than unicortical screws. CONCLUSION: Advancing an anterior vertebral body screw to engage the second cortex increases resistance to pullout by 25-44%, depending on vertebral bone mineral density. The difference in resistance between unicortical and bicortical techniques was smaller in specimens with low mineral densities.
STUDY DESIGN: The pullout strength of unicortical and bicortical screws in thoracic and lumbar vertebral bodies was measured as a function of bone mineral density. OBJECTIVES: To determine the influence of bone mineral density and screw insertion technique on the stability of anterior thoracolumbar spine screw fixation. SUMMARY OF BACKGROUND DATA: No previous study has addressed the specific technique of screw insertion or stability of screw fixation in the anterior spine. METHODS: Fifty-one human thoracic vertebral bodies were tested in pullout with 6.55-mm cancellous screws inserted using unicortical and bicortical techniques. RESULTS: Pullout force increased exponentially with increasing bone mineral density for unicortical and bicortical screws. Bicortical screws were significantly stronger in resisting pullout than unicortical screws. CONCLUSION: Advancing an anterior vertebral body screw to engage the second cortex increases resistance to pullout by 25-44%, depending on vertebral bone mineral density. The difference in resistance between unicortical and bicortical techniques was smaller in specimens with low mineral densities.
Authors: Meena M Sran; Karim M Khan; Kathy Keiver; Jason B Chew; Heather A McKay; Thomas R Oxland Journal: Eur Spine J Date: 2004-12-23 Impact factor: 3.134
Authors: Thomas M Shea; James J Doulgeris; Sabrina A Gonzalez-Blohm; William E Lee; Kamran Aghayev; Frank D Vrionis Journal: Biomed Res Int Date: 2015-02-01 Impact factor: 3.411
Authors: Thomas M Shea; Jake Laun; Sabrina A Gonzalez-Blohm; James J Doulgeris; William E Lee; Kamran Aghayev; Frank D Vrionis Journal: Biomed Res Int Date: 2014-03-03 Impact factor: 3.411