Quantitative motor unit action potential analysis of paraspinal muscles, diagnostic imaging and necropsy findings in 36 horses suspected of cervical impairment.

INTRODUCTION Aims: To determine the relation between quantitative electromyography (QEMG) of the cervical ventral serratus muscle, radiographic findings and post-mortem gross and histopathological examination in order to calculate the ability of QEMG to localize the region of cervical compressive neuropathy and myelopathy in horses. Methods: In this clinical, non-randomised, partially blinded study (QEMG and histology), 36 warmblood horses with clinical suspicion of cervical spine disease were examined with QEMG in different segments of the ventral serratus muscle. Results were compared to normative data. Diagnostic imaging was performed in 28 cases. All horses were euthanized because of poor clinical prognoses and/or recurrent clinical neurological signs despite treatment and underwent necropsy with emphasis on the cervical nervous tissue and vertebrae. Clinical and diagnostic imaging findings, QEMG results and post mortem findings were compared with each other. Results: Overall mean values of duration (9.54 ms), polyphasia, number of phases (3.6) and size index (0.67) in horses with cervical lesions were significantly (P

Quantification of surface EMG signals to monitor the effect of a Botox treatment in six healthy ponies and two horses with stringhalt: preliminary study

Reasons for performing the study: Therapeutic options for stringhalt in horses are limited, whereas medical experiences with botulinum toxin type A (Botox) have been positive. To evaluate its effectiveness in horses, surface electromyography (sEMG) signals before and after injection need to be quantified. Hypothesis: Treatment of healthy ponies and cases with Botox should reduce muscle activity in injected muscles and reduce spastic movements without adverse side effects. Methods: Unilaterally, the extensor digitorum longus, extensor digitorum lateralis and lateral vastus muscles of 6 healthy mature Shetland ponies and 2 talented Dutch Warmblood dressage horses with stringhalt were injected (maximum of 400 iu per pony and 700 in per case; 100 in in 5 ml NaCl divided into 5 injections) with Botox under needle EMG guidance. Surface EMG data were evaluated using customised software, and in the individuals gait was analysed using Proreflex. Statistical analysis was performed using mixed models and independent sample t test (P<0.05). Results: Surface EMG signals were quantified using customised software. The area under the curve (integrated EMG) in time was used as variable. It became significantly reduced in injected muscles after injection of Botox in normal ponies (P<0.05). This effect was present from Day 1 until Day 84 after injection. In the 2 cases, after injection of 3 muscles, the integrated EMG in time became significantly reduced in all 3 muscles. Kinematic measurements confirmed reduction of frequency and amplitude of hyperflexing or hyperabducting strides of the affected hindlimbs. The duration of effect was also seen in the cases until around 12 weeks after injection. Conclusions and potential relevance: After EMG guided injections of Botox, sEMG signals recorded from injected muscle were reduced, which proves this to be a useful tool in statistically evaluating a treatment effect. The positive results of this pilot study encourage further research with a larger group of clinical cases

The use of electromyography interference pattern analysis to determine muscle force of the deep digital flexor muscle in healthy and laminitic horses

Background: In equine laminitis, the deep digital flexor muscle (DDFM) appears to have increased muscle force, but evidence-based confirmation is lacking. Objectives: The purpose of this study was to test if the DDFM of laminitic equines has an increased muscle force detectable by needle electromyography interference pattern analysis (IPA). Animals and Methods: The control group included six Royal Dutch Sport horses, three Shetland ponies and one Welsh pony [10 healthy, sound adults weighing 411 217 kg (mean SD) and aged 10 +/- 5 years]. The laminitic group included three Royal Dutch Sport horses, one Friesian, one Haflinger, one Icelandic horse, one Welsh pony, one miniature Appaloosa and six Shetland ponies (14 adults, weight 310 +/- 178 kg, aged 13 +/- 6 years) with acute/chronic laminitis. The electromyography IPA measurements included firing rate, turns/second (T), amplitude/turn (M) and M/T ratio. Statistical analysis used a general linear model with outcomes transformed to geometric means. Results: The firing rate of the total laminitic group was higher than the total control group. This difference was smaller for the ponies compared to the horses; in the horses, the geometric mean difference of the laminitic group was 1.73 [geometric 95% confidence interval (CI) 1.29-2.32], and in the ponies this value was 1.09 (geometric 95% CI 0.82-1.45). Conclusion and clinical relevance: In human medicine, an increased firing rate is characteristic of increased muscle force. Thus, the increased firing rate of the DDFM in the context of laminitis suggests an elevated muscle force. However, this seems to be only a partial effect as in this study, the unchanged turns/second and amplitude/turn failed to prove the recruitment of larger motor units with larger amplitude motor unit potentials in laminitic equids

A pilot study on objective quantification and anatomical modelling of in vivo head and neck positions commonly applied in training and competition of sport horses

Reasons for performing study: Head and neck positions (HNP) in sport horses are under debate in the equine community, as they could interfere with equine welfare. HNPs have not been quantified objectively and no information is available on their head and neck loading. Objectives: To quantify in vivo HNPs in sport horses and develop o a model to estimate loading on the cervical vertebrae in these positions. Methods: Videos were taken of 7 Warmbloods at walk on a straight line in 5 positions, representing all HNPs during Warmblood training and competition. Markers were glued at 5 anatomical landmarks. Two-dimensional angles and distances were determined from video frames for the 5 HNPs and statistically compared (P < 0.05). A new simulation model was developed to estimate nuchal ligament cervical loading at these HNPs. Results: The mean angles were significantly different between the 5 HNPs for the line between C1 and T6 with the horizontal and for the line connecting the facial crest (CF) and C1 with the vertical, while the vertical distance from CF to the lateral styloid process of the radius (PS) was significantly different between all 5 positions (P < 0.05). The estimated nuchal ligament loading appeared to be largest at the origin of C2 for all HNPs, except for the 'hyperextended' HNP5; the 'hyperflexed' HNP4 showed the largest loading values on the nuchal ligament origins at all locations. Conclusions: HNPs can be accurately quantified in the sagittal plane from angles and distances based on standard anatomical landmarks and home-video captured images. Nuchal ligament loading showed the largest estimated values at its origin on C2 in hyperflexion (HNP4). Potential relevance: Modelling opens further perspectives to eventually estimate loading for individual horses and thus ergonomically optimise their HNP, which may improve the welfare of the sport horse during training and competition