In vitro transmission and attenuation of impact vibrations in the distal forelimb

Short Communication: changes in gait after 12 wk of shoeing in previously barefoot horses

Farriery can impact gait symmetry and lameness outcomes, but there is limited scientific data documenting these effects. We hypothesized that shoeing previously barefoot horses with plain stamp shoes on the hind hooves would increase gait symmetry, alter hock angles and increase range of motion, and improve lameness scores more than shoeing with traditional fullered shoes. At the start of the study, gait symmetry via wireless inertial motion sensors (IMS), kinematic gait analysis (hock angle and range of motion), and American Association for Equine Practitioner's (AAEP) lameness scoring were completed for 14 barefoot horses. Horses were then trimmed and hind hooves were shod (wk 0) in three-quarter fullered shoes or plain stamp style shoes. Horses were trimmed and re-shod at week 6. At the end of 12 wk, the IMS analysis, kinematic gait analysis, and lameness scoring were repeated. Differences between shod and barefoot values were calculated for each horse, and impact of shoe type was analyzed via t-test. Significance was determined at P ≤ 0.05. No differences were observed in the IMS scores, hock angles or range of motion, or AAEP lameness scores between horses shod in fullered or plain stamp shoes (P ≥ 0.08). As no variables were determined to be significantly different between the two shoe types, data from all horses were combined to analyze the differences between the barefoot and shod state. Shoeing increased the maximum angle of the right and left hocks (P ≤ 0.03) and the minimum angle of the left (P = 0.02) but not right hock (P = 0.23) relative to barefoot conditions. No differences in hock range of motion were observed in either hock. Lower AAEP lameness scores were observed in horses when shod compared with barefoot (P = 0.001). In conclusion, shoeing previously barefoot horses improved AAEP lameness scores and increased hock angles, regardless of the type of shoe.

Hoof Impact and Foot-Off Accelerations in Galloping Thoroughbred Racehorses Trialling Eight Shoe-Surface Combinations

The athletic performance and safety of racehorses is influenced by hoof−surface interactions. This intervention study assessed the effect of eight horseshoe−surface combinations on hoof acceleration patterns at impact and foot-off in 13 galloping Thoroughbred racehorses retired from racing. Aluminium, barefoot, GluShu (aluminium−rubber composite) and steel shoeing conditions were trialled on turf and artificial (Martin Collins Activ-Track) surfaces. Shod conditions were applied across all four hooves. Tri-axial accelerometers (SlamStickX, range ±500 g, sampling rate 5000 Hz) were attached to the dorsal hoof wall (x: medio-lateral, medial = positive; y: along dorsal hoof wall, proximal = positive; and z: perpendicular to hoof wall, dorsal = positive). Linear mixed models assessed whether surface, shoeing condition or stride time influenced maximum (most positive) or minimum (most negative) accelerations in x, y and z directions, using ≥40,691 strides (significance at p < 0.05). Day and horse−rider pair were included as random factors, and stride time was included as a covariate. Collective mean accelerations across x, y and z axes were 22−98 g at impact and 17−89 g at foot-off. The mean stride time was 0.48 ± 0.07 s (mean ±2 SD). Impact accelerations were larger on turf in all directions for forelimbs and hindlimbs (p ≤ 0.015), with the exception of the forelimb z-minimum, and in absolute terms, maximum values were typically double the minimum values. The surface type affected all foot-off accelerations (p ≤ 0.022), with the exception of the hindlimb x-maximum; for example, there was an average increase of 17% in z-maximum across limbs on the artificial track. The shoeing condition influenced all impact and foot-off accelerations in the forelimb and hindlimb datasets (p ≤ 0.024), with the exception of the hindlimb impact y-maximum. Barefoot hooves generally experienced the lowest accelerations. The stride time affected all impact and foot-off accelerations (p < 0.001). Identifying factors influencing hoof vibrations upon landing and hoof motion during propulsion bears implication for injury risk and racing outcomes.

Automatic methods of hoof-on and -off detection in horses using wearable inertial sensors during walk and trot on asphalt, sand and grass

Detection of hoof-on and -off events are essential to gait classification in horses. Wearable sensors have been endorsed as a convenient alternative to the traditional force plate-based method. The aim of this study was to propose and validate inertial sensor-based methods of gait event detection, reviewing different sensor locations and their performance on different gaits and exercise surfaces. Eleven horses of various breeds and ages were recruited to wear inertial sensors attached to the hooves, pasterns and cannons. Gait events detected by pastern and cannon methods were compared to the reference, hoof-detected events. Walk and trot strides were recorded on asphalt, grass and sand. Pastern-based methods were found to be the most accurate and precise for detecting gait events, incurring mean errors of between 1 and 6ms, depending on the limb and gait, on asphalt. These methods incurred consistent errors when used to measure stance durations on all surfaces, with mean errors of 0.1 to 1.16% of a stride cycle. In conclusion, the methods developed and validated here will enable future studies to reliably detect equine gait events using inertial sensors, under a wide variety of field conditions.

Automatic hoof-on and -off detection in horses using hoof-mounted inertial measurement unit sensors

For gait classification, hoof-on and hoof-off events are fundamental locomotion characteristics of interest. These events can be measured with inertial measurement units (IMUs) which measure the acceleration and angular velocity in three directions. The aim of this study was to present two algorithms for automatic detection of hoof-events from the acceleration and angular velocity signals measured by hoof-mounted IMUs in walk and trot on a hard surface. Seven Warmblood horses were equipped with two wireless IMUs, which were attached to the lateral wall of the right front (RF) and hind (RH) hooves. Horses were walked and trotted on a lead over a force plate for internal validation. The agreement between the algorithms for the acceleration and angular velocity signals with the force plate was evaluated by Bland Altman analysis and linear mixed model analysis. These analyses were performed for both hoof-on and hoof-off detection and for both algorithms separately. For the hoof-on detection, the angular velocity algorithm was the most accurate with an accuracy between 2.39 and 12.22 ms and a precision of around 13.80 ms, depending on gait and hoof. For hoof-off detection, the acceleration algorithm was the most accurate with an accuracy of 3.20 ms and precision of 6.39 ms, independent of gait and hoof. These algorithms look highly promising for gait classification purposes although the applicability of these algorithms should be investigated under different circumstances, such as different surfaces and different hoof trimming conditions.

Water treadmill exercise reduces equine limb segmental accelerations and increases shock attenuation

BACKGROUND

Equine water treadmills (WTs) are growing in popularity because they are believed to allow for high resistance, low impact exercise. However, little is known about the effect of water height on limb loading. The aim of this study was to evaluate the effect of water height and speed on segmental acceleration and impact attenuation during WT exercise in horses. Three uniaxial accelerometers (sampling rate: 2500 Hz) were secured on the left forelimb (hoof, mid-cannon, mid-radius). Horses walked at two speeds (S1: 0.83 m/s, S2: 1.39 m/s) and three water heights (mid-cannon, carpus, stifle), with a dry WT control. Peak acceleration of each segment was averaged over five strides, attenuation was calculated, and stride frequency was estimated by the time between successive hoof contacts. Linear mixed effects models were used to examine the effects of water height, speed, and accelerometer location on peak acceleration, attenuation and stride frequency (p < 0.05).

RESULTS

Peak acceleration at all locations was lower with water of any height compared to the dry control (p < 0.0001). Acceleration was reduced with water at the height of the stifle compared to mid-cannon water height (p = 0.02). Water at the height of the stifle attenuated more impact than water at the height of the cannon (p = 0.0001).

CONCLUSIONS

Water immersion during treadmill exercise reduced segmental accelerations and increased attenuation in horses. WT exercise may be beneficial in the rehabilitation of lower limb injuries in horses.

Validation of distal limb mounted inertial measurement unit sensors for stride detection in Warmblood horses at walk and trot

Background

Inertial measurement unit (IMU) sensor‐based techniques are becoming more popular in horses as a tool for objective locomotor assessment.

Objectives

To describe, evaluate and validate a method of stride detection and quantification at walk and trot using distal limb mounted IMU sensors.

Study design

Prospective validation study comparing IMU sensors and motion capture with force plate data.

Methods

A total of seven Warmblood horses equipped with metacarpal/metatarsal IMU sensors and reflective markers for motion capture were hand walked and trotted over a force plate. Using four custom built algorithms hoof‐on/hoof‐off timing over the force plate were calculated for each trial from the IMU data. Accuracy of the computed parameters was calculated as the mean difference in milliseconds between the IMU or motion capture generated data and the data from the force plate, precision as the s.d. of these differences and percentage of error with accuracy of the calculated parameter as a percentage of the force plate stance duration.

Results

Accuracy, precision and percentage of error of the best performing IMU algorithm for stance duration at walk were 28.5, 31.6 ms and 3.7% for the forelimbs and −5.5, 20.1 ms and −0.8% for the hindlimbs, respectively. At trot the best performing algorithm achieved accuracy, precision and percentage of error of −27.6/8.8 ms/−8.4% for the forelimbs and 6.3/33.5 ms/9.1% for the hindlimbs.

Main limitations

The described algorithms have not been assessed on different surfaces.

Conclusions

Inertial measurement unit technology can be used to determine temporal kinematic stride variables at walk and trot justifying its use in gait and performance analysis. However, precision of the method may not be sufficient to detect all possible lameness‐related changes. These data seem promising enough to warrant further research to evaluate whether this approach will be useful for appraising the majority of clinically relevant gait changes encountered in practice.

The suspensory apparatus of the distal phalanx in normal horses

REASONS FOR PERFORMING STUDY

The suspensory apparatus of the distal phalanx (SADP) is functionally and clinically important.

OBJECTIVES

To investigate SADP form and function and the microanatomy of its insertion zone.

STUDY DESIGN

Descriptive gross and microanatomy.

METHODS

The feet of 6 normal Standardbred horses were sectioned into blocks along the traditional perpendicular transverse axis and along functional axes of the SADP, decalcified and processed for staining with haematoxylin and eosin, Jones' periodic acid silver methenamine or Masson's trichrome stains.

RESULTS

In traditional midline toe transverse plane sections SADP collagen bundles were irregular with an unstructured appearance. In sections made transversely along planes (70° and 30°) aligned with the long axis of the SADP, collagen bundles were arranged in linear rows. The linear bundles were continuous from their origin on parietal ridges of the distal phalanx through to the secondary epidermal lamellar basement membrane. At the parietal ridge interface the collagen bundles coalesced into smaller, strongly silver staining, linear structures that penetrated the cortical bone and merged with adjacent osteons. In proximal sagittal sections collagen bundles were also linear, angled at 70° to the ground surface. In distal sagittal sections collagen bundles were also arranged linearly but in a multi-angled, 'spokes of a wheel' arrangement, centred on the distal phalanx apex.

CONCLUSIONS

Sectioning along functional axes demonstrated the true suspensory nature of the SADP connecting the parietal surface to the lamellar hoof wall. SADP/distal phalanx insertions showed penetrating fibres extending through the chondral-apophyseal interface up to and between distal phalanx osteons. Lamellar measurements made from sections perpendicular to the dorsal aspect of the distal phalanx are underestimations but if made along the longer, functional midline 70° transverse plane would accurately reflect the suspensory function of the lamellae. Laminitis pathophysiology correctly viewed as SADP degradation should inform logical, future therapeutic strategies.

Distribution and processing of a disintegrin and metalloproteinase with thrombospondin motifs-4, aggrecan, versican, and hyaluronan in equine digital laminae

OBJECTIVE

To determine the expression and distribution of a disintegrin and metalloproteinase with thrombospondin motifs-4 (ADAMTS-4), its substrates aggrecan and versican, and their binding partner hyaluronan in laminae of healthy horses.

SAMPLE

Laminae from the forelimb hooves of 8 healthy horses.

PROCEDURES

Real-time quantitative PCR assay was used for gene expression analysis. Hyaluronidase, chondroitinase, and keratanase digestion of lamina extracts combined with SDS-PAGE and western blotting were used for protein and proteoglycan analysis. Immunofluorescent and immunohistochemical staining of tissue sections were used for protein and hyaluronan localization.

RESULTS

Genes encoding ADAMTS-4, aggrecan, versican, and hyaluronan synthase II were expressed in laminae. The ADAMTS-4 was predominantly evident as a 51-kDa protein bearing a catalytic site neoepitope indicative of active enzyme and in situ activity, which was confirmed by the presence of aggrecan and versican fragments bearing ADAMTS-4 cleavage neoepitopes in laminar protein extracts. Aggrecan, versican, and hyaluronan were localized to basal epithelial cells within the secondary epidermal laminae. The ADAMTS-4 localized to these cells but was also present in some cells in the dermal laminae.

CONCLUSIONS AND CLINICAL RELEVANCE

Within digital laminae, versican exclusively and aggrecan primarily localized within basal epithelial cells and both were constitutively cleaved by ADAMTS-4, which therefore contributed to their turnover. On the basis of known properties of these proteoglycans, it is possible that they can protect the basal epithelial cells of horses from biomechanical and concussive stress.

Frontal sinuses and head-butting in goats: a finite element analysis

Frontal sinuses in goats and other mammals have been hypothesized to function as shock absorbers, protecting the brain from blows during intraspecific combat. Furthermore, sinuses are thought to form through removal of `structurally unnecessary' bone. These hypotheses were tested using finite element modeling. Three-dimensional models of domesticated goat (Capra hircus) skulls were constructed, with variable frontal bone and frontal sinus morphology, and loaded to simulate various head-butting behaviors. In general, models with sinuses experienced higher strain energy values (a proxy for shock absorption) than did models with unvaulted frontal bones, and the latter often had higher magnitudes than models with solid vaulted frontal bones. Furthermore, vaulted frontal bones did not reduce magnitudes of principal strain on the surface of the endocranial cavity relative to models with unvaulted frontal bones under most loading conditions. Thus, these results were only partially consistent with sinuses, or the bone that walls the sinuses, acting as shock absorbers. It is hypothesized that the keratinous horn sheaths and cranial sutures are probably more important for absorbing blows to the head. Models with sinuses did exhibit a more `efficient'distribution of stresses, as visualized by histograms in which models with solid frontal bones had numerous unloaded elements. This is consistent with the hypothesis that sinuses result at least in part from the removal of mechanically unnecessary bone.