Effect of Water Depth on Limb and Back Kinematics in Horses Walking on a Water Treadmill.

Water treadmill (WT) exercise is frequently used for training/rehabilitation of horses. There is limited study into the effect of water depth on limb/back kinematics warranting investigation. The objective was to determine the effect of walking in different water depths, at the same speed, on limb/back kinematics measured simultaneously in a group of horses. Six horses (age:15 ± 6.5 years) completed a standardized WT exercise session (19 minutes duration; speed:1.6 m/s; water depths: 0.0/7.5/21.0/32.0/47.0 cm). Ten waterproof light-emitting-diode tea-light-markers and reflective-spheres were affixed to the skin at predetermined locations; inertial-measurement-units were fixed to the poll/withers/left and right tubera coxae (TC)/sacrum to determine range-of-motion (ROM) changes of these locations. Univariable-mixed-effects-linear-regression-analyses were carried out, with a significance value of P ≤ .05. At maximum carpal/tarsal flexion during swing, regression analyses showed a clear and consistent nonlinear increase in carpal and tarsal flexion at increasing water depths (P < 0.0001 for both variables). As water depth increased there was a significant increase in thoracic spine flexion-extension ROM (P < 0.0001 at all thoracic sites) and increased dorsoventral and mediolateral ROM of the sacrum/left and right TC (P < 0.001 for all variables) as water depth increased. Results suggest that horses responded to an increase in water depth until a threshold depth was reached when the biomechanical response levelled off, and there was increased pelvic roll. In conclusion, changes in limb kinematics brought about by relatively modest increases in water depth at walking speed of 1.6 m/s are sufficient to induce significant changes in back/pelvic movement highlighting key issues with relevance for WT program design.

Consensus for the General Use of Equine Water Treadmills for Healthy Horses.

Water treadmill exercise has become popular in recent years for the training and rehabilitation of equine athletes. In 2019, an equine hydrotherapy working group was formed to establish what was commonly considered to be best practice in the use of the modality. This article describes the process by which general guidelines for the application of water treadmill exercise in training and rehabilitation programmes were produced by the working group. The guidelines describe the consensus reached to date on (1) the potential benefits of water treadmill exercise, (2) general good practice in water treadmill exercise, (3) introduction of horses to the exercise, (4) factors influencing selection of belt speed, water depth and duration of exercise, and (5) monitoring movement on the water treadmill. The long-term goal is to reach a consensus on the optimal use of the modality within a training or rehabilitation programme. Collaboration between clinicians, researchers and experienced users is needed to develop research programmes and further guidelines regarding the most appropriate application of the modality for specific veterinary conditions.

Magnetic Resonance Imaging Findings in the Proximal Metacarpal Region of 359 Horses and Proximal Metatarsal Region of 64 Horses Acquired Under Standing Sedation.

Standing magnetic resonance (MR) images of proximal metacarpal/metatarsal regions are increasingly being acquired. This study aimed at describing ranges of abnormalities detected in sport/racehorses, using retrospective evaluation of magnetic resonance imaging (MRI) reports from horses with lameness isolated to proximal metacarpal/metatarsal regions with images acquired standing. It was hypothesized that MRI features are different between metacarpal and metatarsal regions and between horses doing different sports. Reports from 359 forelimbs and 64 hindlimbs were included. Palmar/plantar metacarpal/metatarsal bone injury and suspensory desmopathy, which often occurred concurrently, were most frequently reported. Third metacarpal abnormalities were more likely at palmar/medial locations, including cortical (86.4%) and trabecular (38.2%) pathology with frequent thickening, irregularity, and periosteal/endosteal abnormalities. Fluid signal was reported in cortical (38.7%) and trabecular (22.6%) bone. Medial intermetacarpal articulation abnormalities were more frequently reported (52.5%) than lateral. Suspensory ligament pathology was reported in 83.8% forelimbs, frequently with cortical (74.1%) or trabecular (32.9%) pathology. Tarsal-joint abnormalities were significantly more likely than carpal-joint abnormalities. Third metatarsal cortical (57.8%) and trabecular (20.3%) pathology was most frequently plantar, but significantly more likely to be dorsal than forelimbs. Metatarsal fluid signal was significantly less likely than metacarpal. Lateral intermetatarsal articulation pathology (23.4%) was more frequent than medial; medial was significantly more likely in forelimbs. Suspensory ligament abnormalities were reported in 64.1% hindlimbs, 39.1% having concurrent cortical pathology. Metacarpal fluid signal was significantly more likely in endurance/racehorses than dressage/show jumping horses. Dressage was overrepresented in hindlimb suspensory origin pathology. These findings indicate different pathology patterns between forelimb/hindlimb and between different sports and may be useful for MRI interpretation.

Histopathologic features of distal tarsal joint cartilage and subchondral bone in ridden and pasture-exercised horses.

OBJECTIVE: To determine whether histopathologic characteristics of the osteochondral units of equine distal tarsal joints were associated with exercise history in horses without lameness. SAMPLE POPULATION: 30 cadaver tarsi from horses without lameness and with known exercise history were separated into 3 groups: nonridden, pasture exercise (group P); low-intensity, ridden exercise (group L); and high-intensity, elite competition exercise (group E). PROCEDURES: Standardized sites from the centrodistal and tarsometatarsal joints under went histologic preparation. A grading system was adapted to describe location, depth, and shape of lesions; cellular arrangement; organization at cartilage and subchondral bone (SCB) junctions; and organization of SCB. A high score signified a more severe pathological change than a low score. Exercise groups were compared by calculation of Spearman rank correlations. RESULTS: In the centrodistal joint, lesions were present in groups L and E but only medially. Cellular arrangement scores were higher at the dorsomedial location in group P than in groups L and E. Groups L and E had higher scores than group P for the organization of the cartilage, SCB junctions, and SCB, with higher scores at the dorsomedial location. In the tarsometatarsal joint, lesions were evident across the whole joint surface, with more severe lesions located laterally in all 3 groups. Overall, group E had higher scores for cellular arrangement and SCB organization than groups P and L. CONCLUSIONS AND CLINICAL RELEVANCE: Ridden exercise may increase the risk of osteochondral lesions at distal tarsal sites predisposed to osteoarthritis relative to the risk with nonridden exercise.

External characteristics of the lateral aspect of the hoof differ between non-lame and lame horses.

During a pre-purchase examination (PPE) there is always a debate about how clinical findings of the hoof different from ideal should be interpreted in relation to future lameness risk and/or unsuitability of the horse for the potential purchaser. The objectives of this study were to describe and compare external angular measurements, linear ratios and hoof capsule characteristics of non-lame and lame feet. Photographs of feet from 300 horses with foot pain and 25 non-lame horses were analysed. Hoof wall, heel and coronary band angles and hoof wall length and height, weight-bearing length, coronary band length and height of the coronary band at dorsal and palmar locations were measured and expressed as linear ratios. Mean hoof wall, heel and coronary band angles were larger in lame compared with non-lame feet; only the ratio of dorsal to palmar coronary band heights and the shape of the coronary band were significantly different between lame and non-lame horses. Growth rings were divergent and horn tubules were non-parallel in lameness of >3 months. At a PPE, a larger ratio of dorsal to palmar coronary band heights in one limb may be indicative of previous lameness in that foot. Changes in coronary band shape and divergent growth rings and horn tubules would suggest a longer duration.

Effect of exercise on thicknesses of mature hyaline cartilage, calcified cartilage, and subchondral bone of equine tarsi.

OBJECTIVE-To investigate effects of exercise on hyaline cartilage (HC), calcified cartilage (CC), and subchondral bone (SCB) thickness patterns of equine tarsi. SAMPLE POPULATION-30 tarsi from cadavers of horses with known exercise history. PROCEDURES-Tarsi were assigned to 3 groups according to known exercise history as follows: pasture exercise only (PE tarsi), low-intensity general-purpose riding exercise (LE tarsi), and high-intensity elite competition riding exercise (EE tarsi). Osteochondral tissue from distal tarsal joints underwent histologic preparation. Hyaline cartilage, CC, and SCB thickness were measured at standard sites at medial, midline, and lateral locations across joints with a histomorphometric technique. RESULTS-HC, CC, and SCB thickness were significantly greater at all sites in EE tarsi, compared with PE tarsi; this was also true when LE tarsi were compared with PE tarsi. At specific sites, HC, CC, and SCB were significantly thicker in EE tarsi, compared with LE tarsi. Along the articular surface of the proximal aspect of the third metatarsal bone, SCB was thickest in EE tarsi and thinnest in LE tarsi; increases were greatest at sites previously reported to undergo peak strains and osteochondral damage. CONCLUSIONS AND CLINICAL RELEVANCE-Increased exercise was associated with increased HC, CC, and SCB thickness in mature horses. At sites that undergo high compressive strains, with a reported predisposition to osteoarthritic change, there was increased CC and SCB thickness. These results may provide insight into the interaction between adaptive response to exercise and pathological change.

Evaluation of age-related changes in the structure of the equine tarsometatarsal osteochondral unit.

OBJECTIVE: To investigate effects of age on thickness and morphologic characteristics of hyaline cartilage, calcified cartilage, total cartilage, and subchondral bone (SCB) in the equine tarsometatarsal joint. SAMPLE POPULATION: 23 tarsal joints from cadavers of 23 ponies (11 days to 25 years old); ponies were limited to pasture exercise and euthanatized for reasons not related to this study. Procedures-Tarsi were allocated into several age groups (11 days old [n = 3], 6 to 9 months old [4], 2 to 3 years old [3], 6 to 8 years old [4], 11 to 17 years old [6], and 20 to 25 years old [3]). Histologic examination and histomorphometric measurement of hyaline cartilage, calcified cartilage, total cartilage, and SCB were performed at medial and lateral sites. RESULTS: A significant decrease was detected in thickness of hyaline cartilage and total cartilage with increasing age, but there was a significant increase in thickness of calcified cartilage and SCB with increasing age. Differences in chondrocyte and collagen fiber arrangement, tidemark, and osteochondral junction morphology were evident among age groups. CONCLUSIONS AND CLINICAL RELEVANCE: These findings suggested that the various tissues of the osteochondral unit change in different ways with age. The response of each tissue may be related to relative response of the tissues to strains induced by pasture exercise but could have an influence on how the overall properties of the osteochondral unit change with age. The findings may also be suggestive of changes that develop prior to the onset of osteoarthritis.

Validation of magnetic resonance imaging for measurement of equine articular cartilage and subchondral bone thickness.

OBJECTIVE: To validate use of magnetic resonance images (MRIs) for measurement of equine articular cartilage and subchondral bone thickness by comparison with measurements in histologic specimens. SAMPLE POPULATION: 32 cadaveric carpal joints from 16 horses. PROCEDURE: Magnetic resonance imaging was performed by use of 3-dimensional fast spoiled gradient echo (SPGR) and T2* 3-dimensional fast gradient echo (GRE) pulse sequences with and without fat saturation. Standard sites on the medial and lateral facets of the intermediate, radial, and third carpal bones were used for subchondral bone and articular cartilage thickness measurements. Digital image analysis software was used for MRI measurements 10 mm from the dorsal extent and perpendicular to the articular surface. Histomorphometric measurements of hyaline, calcified cartilage, and subchondral bone thickness were obtained at selected sites. Comparisons between histomorphometric and MRI measurements and between magnetic resonance pulse sequences were evaluated. RESULTS: There were significant correlations between GRE and SPGR and SPGR and histologic measurements of articular cartilage, with no significant difference between measurements and good agreement. When calcified cartilage was excluded from the histologic measurement, MRI measurements were significantly greater than histologic measurements. For subchondral bone thickness, there was significant correlation between GRE and SPGR but GRE was significantly greater than SPGR measurements. Histomorphometric and MRI measurements were strongly correlated and not significantly different. CONCLUSIONS AND CLINICAL RELEVANCE: Magnetic resonance imaging provides a good representation of cartilage and subchondral bone thickness, supporting its use in the study and clinical diagnosis of osteochondral structure and alteration.