Gait pattern of the ataxic horse compared to sedated and nonsedated horses

Outcomes after cervical vertebral interbody fusion using an interbody fusion device and polyaxial pedicle screw and rod construct in 10 horses (2015-2019)

BACKGROUND

Further development of surgical techniques for equine cervical stabilisation is necessary to make the procedure less technically demanding, reduce complications and improve outcomes.

OBJECTIVE

To describe clinical outcomes and owner reports in horses undergoing placement of an interbody fusion device and polyaxial pedicle screw and rod construct for cervical vertebral fusion in horses with cervical vertebral compressive myelopathy.

STUDY DESIGN

Retrospective case series.

METHODS

Data were retrieved from medical records of 10 horses undergoing cervical vertebral fusion (2015-2019). Records were evaluated for signalment, duration of clinical signs, number and location of compression sites, grade of ataxia, duration of hospitalisation and complications. Long-term follow-up was obtained through clinical re-evaluation, postoperative radiographs and owner contact.

RESULTS

Breeds were mixed. Median age was 24 (range 12-168) months. There were 2/10 mares, 4/10 geldings and 4/10 stallions. Preoperative grade of ataxia ranged from 1-3/5. Fusion was performed at one (n = 3) or two (n = 7) sites. Two horses were euthanised within the first year. In 6 of 8 horses with ≥1-year follow-up, ataxia improved by 1-3 grades, with an average improvement of 1.25 grades. In four horses, ataxia improved to grade 0-1. In two horses the gait was unaffected, but neck comfort improved. Complications included seroma formation (n = 9), pain (n = 5), fever (n = 4), upper respiratory tract obstruction (n = 2), azotemia (n = 2), screw breakage (n = 2), progression of neurological signs (n = 1), Horner's Syndrome (n = 1), dysphagia (n = 1), hives (n = 1), implant infection (n = 1) and nondisplaced fracture (n = 1).

MAIN LIMITATIONS

Small case series, heterogeneous patient population.

CONCLUSIONS

This technique resulted in ≥1 grade gait improvement in 6/10 cases operated and 6/8 cases for which ≥1-year follow-up was available, similar to other methods. Fatal complications related to implant placement did not occur. This technique may represent a safer alternative to current techniques of ventral interbody fusion with similar outcomes.

Kinematic Patterns in Horses Sedated With Low Doses of Detomidine: An Accelerometric Evaluation

Alpha-2-adrenergic drugs, such as detomidine, are commonly used to sedate lame horses during examination. However, the use of these drugs should be minimized, as they have numerous side-effects, like ataxia. Therefore, we wanted to test the effects, on the locomotor pattern, of low doses of detomidine (0.003 mg/kg). Six horses were sedated with 0.003 mg/kg of detomidine and compared with the same horses administered a saline solution. Using a triaxial accelerometer, data of kinetic, coordination and energetic locomotor parameters and the degree of sedation were collected. The effects were monitored for 60 minutes after treatment administration. No effects on coordination parameters were observed, but some kinetic and energetic parameters were significantly altered after detomidine administration compared to the saline group. These results show that administering low doses of detomidine to lame horses can be a useful sedative solution, ensuring a safe examination with lower side-effects.

Subjective and objective evaluations of horses for fit-to-compete or unfit-to-compete judgement

At Fédération Equestre Internationale (FEI) competitions, horses undergo veterinary inspection for judgement of 'fit-to-compete'. However, FEI Veterinary Delegates (VDs) often differ in opinion. The aim of the present study was to evaluate intra- and inter-observer agreements of fit-to-compete judgement and compare these with objective gait analysis measurements. Twelve horses were evaluated by three experienced VDs and one veterinary specialist and video-recorded for re-evaluation later. Simultaneously, quantitative gait analysis measurements were acquired. Inter-observer agreement during live evaluations was fair (κ = 0.395, 58% agreement). Intra-observer agreement between live observations and videos at one and 12 months was 71% and 73% respectively. Sensitivity and specificity of motion symmetry measured with quantitative gait analysis system were 83.3% and 66.7% respectively, against the consensus of all observers as a reference. These findings might suggest that more VDs should be used to adequately judge fit-to-compete. Quantitative-gait-analysis may be useful to support decision making during fit-to-compete judgement.

Effects of acepromazine and xylazine on subjective and objective assessments of forelimb lameness

BACKGROUND

To facilitate lameness evaluation, sedatives such as xylazine and acepromazine are regularly used in the clinical setting, despite concerns that they may confound lameness assessment.

OBJECTIVES

The objective of this study was to determine the effect of low doses of acepromazine and xylazine on subjective and objective lameness assessment.

STUDY DESIGN

Randomised, blinded, crossover study.

METHODS

Six horses with experimentally induced solar pain were evaluated over a 1-hour period after treatment with intravenous xylazine (0.1 or 0.2 mg/kg), intravenous acepromazine (0.02 or 0.04 mg/kg), intravenous saline (1 mL) or local analgesia (4 mL 2% mepivacaine administered subcutaneously). Lameness was assessed objectively with inertial sensors and subjectively on a scale from 0 to 5. Lameness assessments were compared with logistic regression analysis to account for the repeated measures and cross-over study design (P < .05).

RESULTS

Xylazine (0.1 and 0.2 mg/kg) or acepromazine (0.02 and 0.04 mg/kg) did not result in significant differences in objective lameness assessment (vector sum) or average subjective lameness grade. Local analgesia was associated with a decrease in subjective lameness grade (OR 0.32 [0.11-0.92], P = .03). Objective measures of lameness (vector sum) were significantly decreased 45 minutes (vector sum 41.8, P = .04) and 60 minutes (vector sum 47.3, P = .03) following local analgesia administration compared with baseline (vector sum 121.4).

MAIN LIMITATIONS

Extrapolation of the experimental model of moderate lameness used in this study to broad range of clinical lameness situations should be performed carefully.

CONCLUSIONS

These results support the use of low doses of xylazine or acepromazine to facilitate forelimb lameness evaluation up to 1 hour in duration.

Three-Dimensional Kinematic Motion Analysis of Shivers in Horses: A Pilot Study

Our aim was to assess three-dimensional kinematic motion analysis as an objective diagnostic tool for the characterization of the movement disorder of Shivers in horses. Kinematic parameters were measured in three horses with Shivers and were compared with a control group of four normal horses. Multiple parameter differences were found in the horses with Shivers at the walk, during backing, and when asked to pick up their hindlimbs. Most significant changes were a wider hindlimb stance of 0.39 ± 0.15 m and increased abduction angle of 48.7 ± 7.52° and hoof elevation (0.77 ± 0.08 m left and 0.94 ± 0.11 m right) when the horses were asked to pick up their hindlimbs. Control horses could back easily in a straight line and with symmetrical hoof separation and could maintain their center of weight when picking up their hindlimbs. In contrast, the horses with Shivers had difficulty backing straight, were slower, with a shorter stride and asymmetric hoof separation. They could not maintain their center of balance when picking up their hindlimbs. The findings of this pilot study advance the understanding of the movement disorder of Shivers and could be used as outcome measures to evaluate treatment modalities.

Kinetic and kinematic follow-up gait analysis in Doberman Pinschers with cervical spondylomyelopathy treated medically and surgically

Background

The efficacy of treatment of dogs with cervical spondylomyelopathy (CSM) is commonly based on the owner's and clinician's perception of the gait, which is highly subjective and suffers from observer bias.

Hypothesis/Objectives

To compare selected kinetic and kinematic parameters before and after treatments and to correlate the findings of gait analysis to clinical outcome.

Animals

Eight Doberman Pinschers with CSM confirmed by magnetic resonsance imaging.

Methods

Patients were prospectively studied and treated with either medical management (n = 5) or surgery (n = 3). Force plate analysis and 3‐D kinematic motion capture were performed at initial presentation and approximately 8 weeks later. Force plate parameters evaluated included peak vertical force (PVF). Kinematic parameters measured included number of pelvic limb strides, stifle flexion and extension, maximum and minimum thoracic limb distance, truncal sway, and thoracic limb stride duration.

Results

Kinematic analysis showed that deviation of the spine to the right (truncal sway) was significantly smaller (P < .001) and the degree of right stifle flexion was significantly larger (P = .029) after treatment. Force plate analysis indicated that PVF was significantly different after treatment (P = .049) and the difference of the PVF also was significantly larger (P = .027). However, no correlation was found with either method of gait analysis and clinical recovery.

Conclusions and Clinical Importance

Kinetic and kinematic gait analysis were able to detect differences in dogs with CSM before and after treatment. A correlation of gait analysis to clinical improvement could not be determined.

Rater agreement on gait assessment during neurologic examination of horses

Background

Reproducible and accurate recognition of presence and severity of ataxia in horses with neurologic disease is important when establishing a diagnosis, assessing response to treatment, and making recommendations that might influence rider safety or a decision for euthanasia.

Objectives

To determine the reproducibility and validity of the gait assessment component in the neurologic examination of horses.

Animals

Twenty‐five horses referred to the Royal Veterinary College Equine Referral Hospital for neurological assessment (n = 15), purchased (without a history of gait abnormalities) for an unrelated study (n = 5), or donated because of perceived ataxia (n = 5).

Methods

Utilizing a prospective study design; a group of board‐certified medicine (n = 2) and surgery (n = 2) clinicians and residents (n = 2) assessed components of the equine neurologic examination (live and video recorded) and assigned individual and overall neurologic gait deficit grades (0–4). Inter‐rater agreement and assessment‐reassessment reliability were quantified using intraclass correlation coefficients (ICC).

Results

The ICCs of the selected components of the neurologic examination ranged from 0 to 0.69. “Backing up” and “recognition of mistakes over obstacle” were the only components with an ICC > 0.6. Assessment‐reassessment agreement was poor to fair. The agreement on gait grading was good overall (ICC = 0.74), but poor for grades ≤ 1 (ICC = 0.08) and fair for ataxia grades ≥ 2 (ICC = 0.43). Clinicians with prior knowledge of a possible gait abnormality were more likely to assign a grade higher than the median grade.

Conclusion and Clinical Importance

Clinicians should be aware of poor agreement even between skilled observers of equine gait abnormalities, especially when the clinical signs are subtle.

Accuracy and precision of equine gait event detection during walking with limb and trunk mounted inertial sensors

The increased variations of temporal gait events when pathology is present are good candidate features for objective diagnostic tests. We hypothesised that the gait events hoof-on/off and stance can be detected accurately and precisely using features from trunk and distal limb-mounted Inertial Measurement Units (IMUs). Four IMUs were mounted on the distal limb and five IMUs were attached to the skin over the dorsal spinous processes at the withers, fourth lumbar vertebrae and sacrum as well as left and right tuber coxae. IMU data were synchronised to a force plate array and a motion capture system. Accuracy (bias) and precision (SD of bias) was calculated to compare force plate and IMU timings for gait events. Data were collected from seven horses. One hundred and twenty three (123) front limb steps were analysed; hoof-on was detected with a bias (SD) of -7 (23) ms, hoof-off with 0.7 (37) ms and front limb stance with -0.02 (37) ms. A total of 119 hind limb steps were analysed; hoof-on was found with a bias (SD) of -4 (25) ms, hoof-off with 6 (21) ms and hind limb stance with 0.2 (28) ms. IMUs mounted on the distal limbs and sacrum can detect gait events accurately and precisely.

Gait analysis using 3D accelerometry in horses sedated with xylazine

The aim of the present study was to verify the efficacy and sensitivity of an accelerometric device in detecting and quantifying the degree of movement alteration produced in horses sedated with xylazine. Horses (n=6) were randomly administered either xylazine or a control by intravenous injection, with at least 1 week between each treatment. A triaxial accelerometric device was used for the accelerometric gait assessment 15 min before (baseline) and 5, 15, 30, 45, 60, 75, 90, 105 and 120 min after each treatment. Eight different accelerometric parameters were calculated, including speed, stride frequency, stride length, regularity, dorsoventral power, propulsion power, mediolateral power and total power, with the force of acceleration and the dorsoventral, mediolateral and craniocaudal (propulsive) parts of the power then calculated. Administration of xylazine decreased many of the parameters investigated, with significant differences for speed, stride frequency, dorsoventral power, propulsion power and total power at 5, 15, 30 and 45 min after injection. There were no significant differences in stride length values at any time point. Decreases in regularity values were evident with significant differences at every time point from 5 to 120 min following xylazine injection. Force values were also significantly reduced from 5 to 30 min after treatment and a redistribution of the total power was observed 5 min after injection as the mediolateral power increased significantly, while the dorsoventral power decreased. Accelerometry offers a practical, accurate, easy to use, portable and low cost method of objectively monitoring gait abnormalities at the walk in horses after sedation with xylazine.

The difference in kinematics of horses walking, trotting and cantering on a flat and banked 10 m circle

REASONS FOR PERFORMING STUDY

Locomotion adaptation mechanisms have been observed in horses, but little information is available in relation to banked and nonbanked curve locomotion, which might be important to optimise training environments.

OBJECTIVES

To determine if adaptation mechanisms in horses existed when moving on a banked compared to a flat curve and whether adaptation was similar in different gaits.

METHODS

Eight infrared cameras were positioned on the outside of a 10 m lungeing circle and calibrated. Retroreflective markers were used to define left and right metacarpus (McIII) and proximal phalanges (P1), metatarsus (MtIII), head and sacrum. Data were recorded at 308 Hz from 6 horses lunged at walk, trot and canter on a flat and 10° banked circle in a crossover design. Measurements extracted were speed, stride length, McIII inclination, MtIII inclination, relative body inclination and duty factor. Data were smoothed with a fourth order Butterworth filter with 30 Hz cut-off. ANOVA was used to determine differences between conditions and limbs.

RESULTS

Adaptation mechanisms were influenced by gait. At canter inside forelimb duty factor was significantly longer (P<0.05) on a flat curve compared to a banked curve; at walk this was reversed. McIII inclination, MtIII inclination and relative body inclination were significantly greater (P<0.05) at trot and canter on a flat curve, so more inward tilt was found relative to the bearing surface.

CONCLUSION

Adaptation to curved motion is gait specific. At faster gaits it appears that horses negotiate a banked curve with limb posture closer to body posture and probably with demands on the musculoskeletal system more similar to straight canter.