An Analysis of the Relationship between Orthopedic Drill Bit and Screw Diameter on Drilling Energy and Axial Loading Strength
Baskerville, Scott J. J.
MetadataShow full item record
The number of orthopedic procedures performed per year in the United States is expected to grow to 6.6 million by 2020 (1). Most of these surgeries involve some degree of bone drilling and screw fixation, putting many patients at risk of the adverse effects of the heat-induced osteonecrosis which can limit the holding strength of bone screws and the efficacy of the screw-dependent fixtures. Excessive heat-induced osteonecrosis can occur when surgeons prolong the drilling procedure to avoid drill plunge, which can cause damage to soft neurovascular tissues local to the drilling site (2). The SMARTdrill system used in this study maintains constant drill bit RPM, linear feed rate, and real-time torque measurements which can be used to prevent drill plunge and shorten drilling times, thus reducing thermal osteonecrosis and the morbidities that can result from it (3). SawBones artificial bone were used in this study. Pilot holes of various sizes were drilled using comparably-sized drill bits from multiple manufacturers. Standard orthopedic bone screws were inserted into the previously drilled pilot hole using the same drill, and the screw insertion energies were derived using the resulting torque-angle curves. An Instron-compatible apparatus was developed according to the ASTM 543-17 for testing orthopedic screw pull-out strength. The data from the samples produced using each drill bit class were compared amongst each other to evaluate relative effectiveness. Multiple methods were used to model the experimentally-collected data, and each model was compared using statistical techniques to evaluate efficacy. The exponential law, the power law, linear regression, and the law of homography were all examined in this study. The data collected was able to be modeled effectively using one or more of the mathematical representations derived in each case.