Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015.
Authors: Hardeman L C, van der Meij B R, Back W, van der Kolk J H, Wijnberg I D
Journal: Equine veterinary journal
Summary
# Editorial Summary Laminitis is widely suspected to involve increased contractile force in the deep digital flexor muscle (DDFM), yet robust evidence for this mechanism has remained elusive. Hardeman and colleagues employed needle electromyography with interference pattern analysis to compare DDFM electrical activity in 16 laminitic horses and ponies against 10 healthy controls, measuring firing frequency and three morphological parameters (turns per second, amplitude per turn, and their ratio) to detect differences in muscle force generation. The laminitic group demonstrated a significantly elevated mean firing frequency of 72 Hz compared to 53 Hz in controls (P = 0.02)—a 36% increase that mirrors findings in human medicine where heightened firing frequency characterises increased muscle contractility. However, the other electromyographic parameters showed no statistically significant differences between groups, and notably high variance across all measurements tempered the strength of these conclusions. This evidence lends credence to the theory that DDFM hypertonicity contributes to laminitis pathophysiology, with potential implications for therapeutic approaches targeting muscular tension—such as strategic farriery, physiotherapy protocols, and pharmacological muscle relaxants. The authors appropriately acknowledge that their relatively small sample size and considerable data variability warrant larger-scale investigation before firm clinical recommendations can be established.
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Practical Takeaways
- •Needle-EMG analysis may objectively demonstrate increased deep digital flexor muscle force in laminitic horses, supporting the theoretical basis for interventions targeting muscle contracture
- •Current evidence is preliminary with small sample sizes; findings should inform future targeted therapies but do not yet provide conclusive clinical guidance for laminitis management
- •The high variance in measurements suggests individual variation is substantial—future larger studies may help identify which laminitic cases benefit most from DDFM-directed treatments
Key Findings
- •Laminitic horses showed significantly higher deep digital flexor muscle firing frequency (72±21 Hz) compared to healthy controls (53±11 Hz, P=0.02)
- •Increased firing frequency in laminitic group suggests elevated muscle force in the deep digital flexor muscle
- •Other EMG parameters (Turns/Second, Amplitude/Turn, Ratio M/T) showed no significant differences between groups despite high variance
- •Results support the hypothesis of increased deep digital flexor muscle contracture in laminitis but larger studies recommended