Document Type

Thesis

Degree

M.S.B.E.

Degree Granting Department

Chemical Engineering

Major Professor

William E. Lee

Keywords

failure, fracture, polymethylmethacrylate, pullout, toughness

Abstract

When a patient is diagnosed with various spinal injuries, deformities, or advanced degeneration, it is commonly suggested that he/she undergoes surgery for spinal fusion. Most current procedures in spinal fusion restrict mobility in one or multiple levels of the spine so that, over time, new bone will grow between the levels creating a single motionless unit of bone. The bilateral pedicle screw system (BPSS) has long been considered to be the "gold standard" in spinal fusion. However, for patients with osteoporosis, adequate fixation within the bone-screw interface has continuously been difficult to achieve or has come with high risk of other forms of catastrophic damage. Reflecting this, a new pedicle screw design was developed and evaluated against current standard pedicle screws commonly used in spinal surgery. All screw designs were also tested with a common cement augmentation technique surrounding the circumference of the screw. All tests measured pullout strength, stiffness, energy to failure, toughness, and the amount of destruction to the surrounding synthetic bone. While the newly designed pedicle screw failed to produce significantly stronger pullout forces in comparison to the standard screws, it did show evidence of a longer lasting residual axial resistance and a safer mode of failure than the standard screw, hinting that the design may benefit individuals who experience screw pullout and are awaiting reinstrumentation.

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