Pedicle screw fixation is the standard for posterior stabilization of patients with spinal fractures, spinal instability, or degenerative disk disease as well as correction of pathologic deformities. The success of these spinal fixation surgeries depends upon screw-to-bone purchase and screw-to-rod interconnection strength. The literature is replete with biomechanical studies examining pedicle screw purchase within bone [1,2]. Unfortunately, few studies exist which detail the strength of the interconnection of pedicle screws with rods [3,4]. Spinal fixation and deformity correction often involve the need to adjust screw-to-rod position, bend a rod, or rotate a rod to gain proper spinal alignment. These rod manipulation activities are classically performed with the rods in situ in the pedicle screws necessitating a loosening of the closure top and retightening. The effects of closure top loosening and retightening on the resultant grip strength between...

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