Type of Document	Master's Thesis
Author	Baia, Petrisor
Author's Email Address	pbaia@vetmed.lsu.edu
URN	etd-11082011-094452
Title	Mechanical Evaluation of Roughened Screws in Equine Third Metacarpal Bone
Degree	Master of Science (M.S.)
Department	Veterinary Clinical Sciences
Advisory Committee	Advisor Name Title Sod, G. Gary Committee Chair Burba, J.Daniel Committee Co-Chair Riggs, M. Laura Committee Member
Keywords	torque roughened screw bone equine
Date of Defense	2011-10-21
Availability	unrestricted
Abstract ABSTRACT Objectives – To compare the osseointegration of roughened and electropolished 5.5 mm cortical screws used to secure a 4.5 mm broad dynamic compression plate (DCP) in equine third metacarpal (MC3) bones. Study Design – In vivo study Animals – 5 Adult thoroughbred horses (2-7 years old). Methods – For each horse one MC3 was randomly assigned to secure a 4.5 mm broad DCP with 4aluminum oxide (Al2O3) roughened screws on the dorsal mid diaphysis. Four regular electropolished screws used to secure a similar plate on the contralateral limb served as control. They were removed at 12 weeks and the extraction torque was recorded. A paired t-test was used for comparison and statistical significance was set at p < 0.05. Results – At 12 weeks, the mean extraction torque for roughened screws was significantly greater (p < 0.0002) when compared to regular AO screws. The roughened screws had a mean extraction torque of 3.24± 0.56 N-m, which was twice the mean extraction torque of the AO screws (1.65 ± 0.34 N-m). Discussion/Conclusions – Bone tissue infiltrates the pores of the roughened screws increasing the contact surface and the mechanical anchorage. In our study the screw surface roughness is 2.14± 0.48 µm. This roughness has the lowest pore size that will interact with the surrounding bone without altering the screw dimensions. We found that Al2O3 roughened screws have a significantly greater removal torque when compared to the electropolished AO cortical screws when removed at 12 weeks post implantation. Clinical relevance - Information obtained from this study may help in improving the contact surface of implants and subsequent fixation and stability of bone-implant construct in equine fracture repair.
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