An in vitro biomechanical comparison of a 5.5 mm limited-contact dynamic compression plate fixation with a 4.5 mm limited-contact dynamic compression plate fixation of osteotomized equine third metacarpal bones.
Authors: Sod Gary A, Mitchell Colin F, Hubert Jeremy D, Martin George S, Gill Marjorie S
Journal: Veterinary surgery : VS
Summary
# Editorial Summary Selecting the optimal plate size for equine metacarpal fracture repair requires understanding how different fixation systems perform under various loading conditions, prompting researchers to directly compare the biomechanical properties of 5.5 mm and 4.5 mm broad limited-contact dynamic compression plates (LC-DCP) applied to cadaveric equine third metacarpal bones with mid-diaphyseal osteotomies. Using paired bone specimens tested in single-cycle bending to failure, cyclic fatigue loading, and torsional loading, the 5.5 mm plate demonstrated significantly superior resistance to static overload in palmarodorsal bending, achieving higher yield and failure loads (P<.024), whilst the 4.5 mm plate exhibited a marked fatigue advantage, sustaining 80% more loading cycles before failure (P<.05)—a counterintuitive finding suggesting that broader plate rigidity may promote stress concentration at critical points during repetitive loading. Torsional resistance showed no significant difference between the two systems, indicating that plate selection for metacarpal fracture repair should be guided by anticipated loading patterns rather than assumed superiority of larger implants. These results suggest that the 5.5 mm LC-DCP may be preferable for horses with injury patterns or athletic demands likely to generate acute, high-magnitude overload, whereas the 4.5 mm LC-DCP could offer advantages for high-motion disciplines where cyclic fatigue represents the dominant failure mechanism, though clinical validation of these biomechanical findings remains essential before modifying current fixation protocols.
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Practical Takeaways
- •For acute, high-impact fracture repair in horses, 5.5-LC-DCP offers superior resistance to single overload events; however, consider patient activity level and fracture chronicity when selecting plate size
- •In high-demand horses or cases requiring long-term stability under repetitive loading, 4.5-LC-DCP may provide better fatigue resistance despite lower single-load strength
- •Plate selection should account for loading direction: 5.5-LC-DCP is preferable for palmar-dorsal bending loads, but both plates perform similarly against torsional forces
Key Findings
- •5.5-LC-DCP fixation demonstrated significantly greater yield load, failure load, and bending moment than 4.5-LC-DCP under single-cycle 4-point bending (P<0.024)
- •4.5-LC-DCP fixation showed significantly greater cycles to failure in cyclic fatigue testing compared to 5.5-LC-DCP (P<0.05)
- •5.5-LC-DCP provided only 80% of the fatigue stability of 4.5-LC-DCP under cyclic loading
- •No significant difference between plate types in torsional resistance or composite rigidity under torsional loading (P>0.05)