The present study aims to the design of a finite-element model simulating accurately the pullout behaviour of cylindrical pedicle screws and predicting their pullout force. Three commercial pedicle screws, subjected to pure pullout from synthetic bone, were studied experimentally. The results were used for the design, calibration and validation of a finite-element model. Special attention was p...

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. P...

INTRODUCTION Biomechanical properties of four different commercially available small fragment cannulated screws (Twin fix (Stryker, Freiburg, Germany), Herbert, (Zimmer, Warsaw, USA), Omnitech (Unimedical, Torino, Italy), Barouk (Depuy, Warsaw, USA)), with variable pitch, used for fracture fixation were compared. MATERIALS AND METHODS Polyurethane foam blocks of three different densities with...

While the biomechanical properties of pedicle screws have proven to be superior in the lumbar spine, little is known concerning pullout strength of pedicle screws in comparison to hooks in the thoracic spine. In vitro biomechanical pullout testing was performed to evaluate the axial pullout strength of pedicle screws versus pedicle and laminar hooks in the thoracic spine with regard to surgical...

Pullout failure is one of the primary failure modes of API round thread casing connections. Make-up torque and thread tolerances are the two most important factors that can affect the pullout strength. In this paper, the pull-out failure process and mechanism are studied using the finite element analysis (FEA) method. In addition, the effects of make-up torque and thread tolerances on the pullo...

BACKGROUND Pedicle screws with PMMA cement augmentation have been shown to significantly improve the fixation strength in a severely osteoporotic spine. However, the efficacy of screw fixation for different cement augmentation techniques, namely solid screws with retrograde cement pre-filling versus cannulated screws with cement injection through perforation, remains unknown. This study aimed t...

OBJECTIVE Pedicle screw fixation for spine arthrodesis is a useful procedure for the treatment of spinal disorders. However, instrument failure often occurs, and pedicle screw loosening is the initial step of a range of complications. The authors recently used a modified transpedicular polymethylmethacrylate (PMMA) screw augmentation technique to overcome pedicle screw loosening. Here, they rep...