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An In Vitro Biomechanical Comparison of Hydroxyapatite Coated and Uncoated AO Cortical Bone Screws for a Limited Contact: Dynamic Compression Plate Fixation of Osteotomized Equine 3rd Metacarpal Bones
Author(s) -
Durham Myra E.,
Sod Gary A.,
Riggs Laura M.,
Mitchell Colin F.
Publication year - 2015
Publication title -
veterinary surgery
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 79
eISSN - 1532-950X
pISSN - 0161-3499
DOI - 10.1111/j.1532-950x.2014.12259.x
Subject(s) - medicine , cadaveric spasm , dynamic compression plate , fixation (population genetics) , cortical bone , biomechanics , metacarpal bones , orthodontics , dorsum , population , anatomy , biomedical engineering , internal fixation , environmental health
Objectives To compare the monotonic biomechanical properties of a broad 4.5 mm limited contact‐dynamic compression plate (LC‐DCP) fixation secured with hydroxyapatite (HA) coated cortical bone screws (HA‐LC‐DCP) versus uncoated cortical bone screws (AO‐LC‐DCP) to repair osteotomized equine 3rd metacarpal (MC3) bones. Study Design Experimental. Sample Population Adult equine cadaveric MC3 bones (n = 12 pair). Methods Twelve pairs of equine MC3 were divided into 3 test groups (4 pairs each) for: (1) 4 point bending single cycle to failure testing; (2) 4 point bending cyclic fatigue testing; and (3) torsional single cycle to failure testing. For the HA‐LC‐DCP‐MC3 construct, an 8‐hole broad LC‐DCP (Synthes Ltd, Paoli, PA) was secured on the dorsal surface of each randomly selected MC3 bone with a combination of four 5.5 mm and four 4.5 mm HA‐coated cortical screws. For the AO‐LC‐DCP‐MC3 construct, an 8‐hole 4.5 mm broad LC‐DCP was secured on the dorsal surface of the contralateral MC3 bone with a combination of four 5.5 mm and four 4.5 mm uncoated cortical screws. All MC3 bones had mid‐diaphyseal osteotomies. Mean test variable values for each method were compared using a paired t ‐test within each group. Significance was set at P < .05. Results Mean yield load, yield bending moment, composite rigidity, failure load, and failure bending moment, under 4 point bending, single cycle to failure, of the HA‐LC‐DCP fixation were significantly greater than those of the AO‐LC‐DCP fixation. Mean ± SD values for the HA‐LC‐DCP and the AO‐LC‐DCP fixation techniques, respectively, in single cycle to failure under 4 point bending were: yield load, 26.7 ± 2.15 and 16.3 ± 1.38 kN; yield bending moment, 527.4 ± 42.4 and 322.9 ± 27.2 N‐m; composite rigidity, 5306 ± 399 and 3003 ± 300 N‐m/rad; failure load, 40.6 ± 3.94 and 26.5 ± 2.52 kN; and failure bending moment, 801.9 ± 77.9 and 522.9 ± 52.2 N‐m. Mean cycles to failure in 4 point bending of the HA‐LC‐DCP fixation (116,274 ± 13,211) was significantly greater than that of the AO‐LC‐DCP fixation 47,619 ± 6580. Mean yield load, mean composite rigidity, and mean failure load under torsional testing, single cycle to failure was significantly greater for the broad HA‐LC‐DCP fixation compared with the AO‐LC‐DCP fixation. In single cycle to failure under torsion, mean ± SD values for the HA‐LC‐DCP and the AO‐LC‐DCP fixation techniques, respectively, were: yield load, 101.3 ± 14.68 and 70.54 ± 10.20 N‐m; composite rigidity, 437.9 ± 32.9 and 220.7 ± 17.6 N‐m/rad; and failure load: 105.7 ± 15.5 and 75.28 ± 10.1 N‐m. Conclusion HA‐LC‐DCP was superior to AO‐LC‐DCP in resisting the static overload forces (palmarodorsal 4 point bending and torsional) and in resisting cyclic fatigue under palmarodorsal 4 point bending.