| Home | E-Submission | Sitemap | Editorial Office |  
Journal of Korean Neurosurgical Society 2001;30(2): 131-136.
The Effect of Repetitive Insertion and Pullout of Spinal Screws on Pullout Resistance: A Biomechanical Study.
Koang Hum Bak, Lisa Ferrara, Kwang Jin Kim, Jae Min Kim, Choong Hyun Kim, Edward C Benzel
1Department of Neurosurgery, School of Medicine, Hanyang University, Seoul, Korea.
2Department of Neurological Surgery, The Cleveland Clinic Foundation, Cleveland, Ohio, USA.
3Department of Mechanical Engineering, University of New Mexico, Albuquerque, New Mexico, USA.
The clinical uses of screws are increasing with broader applications in spinal disorders. When screws are inserted repeatedly to achieve optimal position, tips of screw pitch may become damaged during insertion even though there are significant differences in the moduli of elasticity between bone and titanium. The effect of repeated screw insertion on pullout resistance was investigated.
Three different titanium screws(cortical lateral mass screw, cancellous lateral mass screw and cervical vertebral body screw) were inserted into the synthetic cancellous material and then extracted axially at a rate of 2.4mm/min using Instron(Model TT-D, Canton, MA). Each set of screws was inserted and pulled out three times. There were six screws in each group. The insertional torque was measured with a torque wrench during insertion. Pullout strength was recorded with a digital oscilloscope.
The mean pullout force measurements for the cortical lateral mass screws(185.66N+/-42.60, 167.10N+/-27.01 and 162.52 N+/-23.83 for first, second and third pullout respectively: p=0.03) and the cervical vertebral body screws(386.0N+/-24.1, 360.2N+/-17.5 and 330.9N+/-16.7: p=0.0024) showed consecutive decrease in pullout resistance after each pullout, whereas the cancellous lateral mass screws did not(194.00N+/-36.47, 219.24N+/-26.58 and 199.49N(36.63: p=0.24). The SEM after insertion and pullout three times showed a blunting in the tip of the screw pitch and a smearing of the screw surface.
Repetitive screw insertion and pullout resulted in the decrease of pullout resistance in certain screws possibly caused by blunting the screw tip. This means screw tips suffer deformations during either repeated insertion or pullout. Thus, the screws that have been inserted should not be used for the final construct.
Key Words: Biomechanical; Pullout; Repetitive; Screw
Full text via DOI  Full text via DOI
Download Citation  Download Citation
Related articles
The Effect of Perioperative Radiation Therapy on Spinal Bone Fusion Following Spine Tumor Surgery  2016 November;59(6)
Review of Constant Infusion Method of Cerebrospinal Fluid Outflow Resistance Study.  1992 April;21(4)
Editorial Office
1F, 18, Heolleung-ro 569-gil, Gangnam-gu, Seoul, Republic of Korea
TEL: +82-2-525-7552   FAX: +82-2-525-7554   E-mail: office@jkns.or.kr
About |  Browse Articles |  Current Issue |  For Authors and Reviewers
Copyright © Korean Neurosurgical Society.                 Developed in M2PI
Close layer