In vitro biomechanical comparison of a modified 5.5 mm locking compression plate fixation with a 5.5 mm locking compression plate fixation of osteotomized equine third metacarpal bones.
Authors: Sod Gary A, Riggs Laura M, Mitchell Colin F, Martin George S, Gill Marjorie S
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: Modified Locking Compression Plate Design for Equine Third Metacarpal Fractures Fracture fixation in the equine third metacarpal bone remains a significant clinical challenge, particularly when managing osteotomies that require reliable mechanical stability during the healing phase. Researchers conducted an in vitro biomechanical study comparing two fixation designs by applying either a standard 5.5 mm broad locking compression plate (5.5-LCP) or a modified version (M5.5-LCP, engineered with 1.0 mm less thickness on the bone contact surface) to paired cadaveric third metacarpal bones with mid-diaphyseal osteotomies, then subjecting both constructs to repetitive palmarodorsal four-point bending to simulate functional loading until failure occurred. The modified plate demonstrated significantly superior fatigue resistance, withstanding an average of 188,641 cycles to failure compared to 166,497 cycles for the standard plate—a clinically meaningful 13% improvement in durability. These findings challenge the widespread adoption of biologic plating principles (which prioritise callus formation through relative motion) for this particular bone and anatomical location, suggesting that plate designs optimised for mechanical rigidity may better support MC3 osteotomy healing in horses and warrant consideration for high-demand athletes where prolonged recovery is costly.
Read the full abstract on PubMed
Practical Takeaways
- •Modified locking compression plate designs show measurably better resistance to cyclic loading in experimental conditions, though clinical relevance requires in vivo validation
- •Standard biological fixation (cortical screws) may be less suitable than locking screw constructs for high-load third metacarpal repairs in performance horses
- •Plate geometry optimization (reduced thickness) can enhance biomechanical performance without apparent loss of mechanical advantage
Key Findings
- •Modified 5.5 mm locking compression plate (M5.5-LCP) achieved 188,641 cycles to failure versus 166,497 cycles for standard 5.5-LCP (13.3% improvement, P<0.05)
- •Reducing plate thickness by 1.0 mm on the bone contact surface significantly improved cyclic fatigue resistance in palmarodorsal bending
- •Biological plate fixation (cortical screws) was inferior to locking screw constructs for equine MC3 osteotomy repair