Mechanical Evaluation of Roughened Screws in Equine Third Metacarpal Bone

• Main Author: Baia, Petrisor
• Other Authors: Riggs, M. Laura
• Format: Others
• Language: en
• Published: LSU 2011
• Subjects: Veterinary Clinical Sciences
• Online Access: http://etd.lsu.edu/docs/available/etd-11082011-094452/

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.