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In Vitro Evaluation of Screws and Suture Anchors in Metaphyseal Bone of the Canine Tibia

Authors


  • Supported by grants from IMEX Inc., Longview, TX and The Comparative Orthopaedic Laboratory, University of Missouri-Columbia, Columbia, MO.

Address reprint requests to James L. Cook, DVM, PhD, Diplomate ACVS, Comparative Orthopaedic Laboratory, University of Missouri-Columbia, 379 East Campus Drive, Columbia, MO 65211. E-mail: cookjl@missouri.edu.

Abstract

Objective— To compare ease of insertion, load to failure, and mode of failure of cortical and cancellous screws, BoneBiter, IMEX, and TwinFix suture anchors in canine metaphyseal tibial bone.

Study Design— Experimental biomechanical study.

Animals— Canine cadaveric tibias.

Methods— One investigator inserted all anchors and subjectively evaluated ease of placement. Anchor systems were loaded to failure along axis of insertion with audio–video recording to determine failure mode.

Results— BoneBiter was the most difficult anchor to insert successfully. Mean±SD loads to failure were cancellous screw (711±193 N), IMEX 4.7 mm 18 g wire (661±163 N), IMEX 4.0 mm 18 g wire (661±165 N), cortical screw (635±184 N), BoneBiter#5 Kevlar suture (393± 109 N), and TwinFix 5.0 mm #2 polyester (267±73 N). No significant differences were noted among the cortical screw, cancellous screw, IMEX 4.7 and 4.0 mm, all of which were significantly (P<.001) greater than BoneBiter and TwinFix. Failure modes were pullout of bone, suture–wire breakage, eyelet breakage, or no failure to 1000 N: screws (18,0,0,2), IMEX (18,1,1,0), BoneBiter (2,8,0,0), and TwinFix (0,10,0,0).

Conclusions— Fixation devices were user friendly, with the exception of BoneBiter. Mode of failure is dependent on suture material and anchor design. Cortical and cancellous screws, and IMEX anchors with 18 g wire have significantly greater load to failure compared with BoneBiter and TwinFix suture anchors.

Clinical Relevance— Based on load to failure, ease of use, design characteristics, and cost, IMEX anchors may have advantages over other comparable soft tissue fixation devices.

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