The aim of this study was to compare the interfragmentary compression generated across a simulated femoral fracture model by a conventional 4.5 mm AO/ASIF cortical lag screw with a differentially pitched cortical compression screw. A 45-degree osteotomy was made in a whole bone composite femoral shaft, this was internally fixed with either a conventional 4.5 mm AO/ASIF cortical lag screw or the...

BACKGROUND Efforts to select the appropriate number of implants in adolescent idiopathic scoliosis (AIS) instrumentation are hampered by a lack of biomechanical studies. The objective was to biomechanically evaluate screw density at different regions in the curve for AIS correction to test the hypothesis that alternative screw patterns do not compromise anticipated correction in AIS when using ...

there have been a number of developments in screw design and implantation techniques over recent years, including proposal of an alternative trajectory entitled as cortical bone trajectory (cbt). cortical bone trajectory has been investigated in recent medical treatments as an alternative for screw fixation aimed at increasing purchase of pedicle screws in higher density bone. cbt screw inserti...

STATEMENT OF PROBLEM Clinicians must know if a new screw can predictably increase reverse torque after multiple screw insertion cycles. PURPOSE The purpose of this study was (1) to compare the effect of multiple implant prosthetic screw insertion and removal cycles on reverse torque, (2) to determine whether a new screw, after multiple screw insertion cycles, affects reverse torque, and (3) t...

This paper studies the vectors of cofactors in a screw matrix assembled by n screws and investigates the properties and different arrangements of cofactors. An augmentation screw which is linearly independent of n screws in the screw matrix is proposed and is used to relate the vector of cofactors to a reciprocal screw and subsequently to the reciprocal screw system. The paper proposes a new al...

STUDY DESIGN The loosening rates of two monocortical pedicle screw designs (hollow and solid) were compared in a cadaveric sacrum model subjected to cyclic loading. OBJECTIVE To determine if a hollow screw would be more resistant to loosening than a solid pedicle screw when placed into the pedicles of S1 and tested under stair-cased cyclic loading. SUMMARY OF BACKGROUND DATA Screw loosening...

STUDY DESIGN Biomechanical study. PURPOSE To determine the effect of density, insertion angle and reinsertion on pull-out strength of pedicle screw in single and two screw-rod configurations. OVERVIEW OF LITERATURE Pedicle screw pull-out studies have involved single screw construct, whereas two screws and rod constructs are always used in spine fusions. Extrapolation of results using the si...