Comparison of insertion time and pullout strength between self-tapping and non-self-tapping AO 4.5-mm cortical bone screws in adult equine third metacarpal bone.
OBJECTIVE
To compare screw insertion characteristics and pullout mechanical properties between self-tapping (ST) and non-self-tapping (NST) AO 4.5-mm cortical bone screws in adult equine third metacarpal bone (MC3).


METHODS
In vitro biomechanical experiment.


METHODS
Seven pairs of adult equine MC3.


METHODS
Bicortical holes were drilled transversely in proximal metaphyseal, diaphyseal, and distal metaphyseal locations of paired MC3. NST screws were inserted in pre-tapped holes in 3 sites of one bone pair, and ST screws were inserted in non-tapped holes of contralateral MC3. Tapping and screw insertion times and maximum torques were measured. Screw pullout mechanical properties were determined.


RESULTS
Screw insertion time was longer for ST screws. Total time for tapping and insertion (total insertion time) was over twice as long for NST screws. Statistically significant differences were not observed between screws for any pullout mechanical property. From pullout tests, diaphyseal locations had significantly stiffer and stronger structure than metaphyseal locations. Pullout failure more commonly occurred because of screw breakage than bone failure. Bone failure and bone comminution were more commonly associated with ST screws. Bone failure sites had pullout failure loads that were 90% of screw failure sites.


CONCLUSIONS
NST and ST 4.5-mm-diameter cortical bone screws have similar pullout mechanical properties from adult equine MC3. ST screws require less than half the total insertion time of NST screws.


CONCLUSIONS
Use of ST 4.5-mm-diameter cortical bone screws should be considered for repair of adult equine MC3 fractures; however, bone failures at screw sites should be monitored.
Andrea
C Renee
CR
J.D. Wheat Veterinary Orthopedic Research Laboratory, Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, One Shields Avenue, Davis, CA 95616, USA.
Stover
Susan M
SM
Galuppo
Larry D
LD
Taylor
Ken T
KT
Rakestraw
Peter C
PC
D000818:Animals; D001696:Biomechanical Phenomena; D001863:Bone Screws / Q000662:veterinary*; D005593:Fracture Fixation, Internal / Q000379:methods / Q000662:veterinary*; D006736:Horses / Q000601:surgery*; D008663:Metacarpus / Q000601:surgery*; D011897:Random Allocation; D013314:Stress, Mechanical; D013997:Time Factors