Turkish Neurosurgery 2015 , Vol 25 , Num 4
The Comparison of Pullout Strengths of Various Pedicle Screw Designs on Synthetic Foams and Ovine Vertebrae
Onur YAMAN1, Teyfik DEMIR2, Arslan Kagan ARSLAN3, Mehmet Akif IYIDIKER2, Tolga TOLUNAY3, Necip CAMUSCU2, Murat ULUTAS4
1Tepecik Education and Training Hospital, Clinic of Neurosurgery, Izmir, Turkey
2TOBB University of Economics and Technology, Department of Mechanical Engineering, Ankara, Turkey
3Yenimahalle State Hospital, Department of Orthopedics, Ankara, Turkey
4Konukoglu Hospital, Department of Neurosurgery, Gaziantep, Turkey
DOI : 10.5137/1019-5149.JTN.8907-13.1 Aim: One of the most common problems with transpedicular screws is screw pullout. This study was conducted to measure the pullout strengths of newly designed transpedicular screws.

Material and Methods: The design of the three group screws were conical cored standard pedicle screw (Type A), dual threaded pedicle screw (Type B), dual core and dual threaded pedicle screw (Type C), respectively. Polyurethane (PU) blocks in 25 mm and 50 mm thickness were used to investigate the effect of just the pedicle on pullout strength and both distal (vertebral body) and proximal (pedicle) parts of the screw. The screws were also tested in ovine lumbar vertebrae.

Results: Type C screw exhibited 5.9% and 12.9% higher pullout strength than Type A and Type B, and 15.4% and 8.6% higher pullout strength than Type A and Type B, respectively on 25 mm and 50 mm thick PU foam block. Type C also exhibited 74.5% and 22.5% higher pullout strength than Type A and Type B, respectively on the ovine vertebrae.

ConclusIon: Transpedicular screws redesigned with modified helical angles exhibit higher pullout strength compared to the classical transpedicular screws and can be inserted more rapidly with the same number of screwing rounds result with doubled insertion depth. Keywords : Pedicle screw, Dual lead, Dual thread

Corresponding author : Onur Yaman, dronuryaman@yahoo.com