Water depth and speed may have an opposite effect on the trunk vertical displacement in horses trotting on a water treadmill.

OBJECTIVE: To measure the trunk vertical displacement (VD) in horses trotting on a water treadmill (WT) at different water depths (WDs) and speeds. ANIMALS: 6 sound Standardbred horses (median age 12 years [IQR:10.5-12]). METHODS: The horses were trotted on a WT at 2 speeds (3.5 m/s and 5 m/s) and during 4 conditions: dry treadmill (DT), WD at mid-cannon (WD-CAN), mid-radius (WD-RAD), and shoulder (WD-SHOUL). The dorsoventral movement was obtained with accelerometers placed over the withers, thoracolumbar junction (T18), tuber sacrale (TS), and sacrum (S5). The VD was defined with the median value of the upward (Up) and downward (Down) amplitudes of the vertical excursion during each stride. The difference of VD at each sensor location was compared between the DT and the 3 WDs, and between the 2 trotting speeds for the same condition. RESULTS: The VD amplitudes were significantly increased at any sensor location when trotting in water at WD-CAN and WD-RAD compared to DT (P < .05 for all), with the highest increase at WD-RAD and T18. When the speed increased from 3.5 to 5 m/s, the VD amplitudes were significantly decreased at T18 at each water level (P = .03), and at WD-RAD only for the withers and TS (P = .03). CLINICAL RELEVANCE: Both water depth and speed affect the trunk VD in horses at trot on a WT with an opposite effect. The VD increases when increasing the WD up to mid-radius, while the VD decreases when increasing the trotting speed, with the main effects observed at the thoracolumbar junction.

Asymmetry Thresholds Reflecting the Visual Assessment of Forelimb Lameness on Circles on a Hard Surface.

The assessment of lameness in horses can be aided by objective gait analysis tools. Despite their key role of evaluating a horse at trot on a circle, asymmetry thresholds have not been determined for differentiating between sound and lame gait during this exercise. These thresholds are essential to distinguish physiological asymmetry linked to the circle from pathological asymmetry linked to lameness. This study aims to determine the Asymmetry Indices (AIs) with the highest power to discriminate between a group of sound horses and a group of horses with consistent unilateral lameness across both circle directions, as categorized by visual lameness assessment conducted by specialist veterinarians. Then, thresholds were defined for the best performing AIs, based on the optimal sensitivity and specificity. AIs were calculated as the relative comparison between left and right minima, maxima, time between maxima and upward amplitudes of the vertical displacement of the head and the withers. Except the AI of maxima difference, the head AI showed the highest sensitivity (≥69%) and the highest specificity (≥81%) for inside forelimb lameness detection and the withers AI showed the highest sensitivity (≥72%) and the highest specificity (≥77%) for outside forelimb lameness detection on circles.

Development of a Methodology for Low-Cost 3D Underwater Motion Capture: Application to the Biomechanics of Horse Swimming.

Hydrotherapy has been utilized in horse rehabilitation programs for over four decades. However, a comprehensive description of the swimming cycle of horses is still lacking. One of the challenges in studying this motion is 3D underwater motion capture, which holds potential not only for understanding equine locomotion but also for enhancing human swimming performance. In this study, a marker-based system that combines underwater cameras and markers drawn on horses is developed. This system enables the reconstruction of the 3D motion of the front and hind limbs of six horses throughout an entire swimming cycle, with a total of twelve recordings. The procedures for pre- and post-processing the videos are described in detail, along with an assessment of the estimated error. This study estimates the reconstruction error on a checkerboard and computes an estimated error of less than 10 mm for segments of tens of centimeters and less than 1 degree for angles of tens of degrees. This study computes the 3D joint angles of the front limbs (shoulder, elbow, carpus, and front fetlock) and hind limbs (hip, stifle, tarsus, and hind fetlock) during a complete swimming cycle for the six horses. The ranges of motion observed are as follows: shoulder: 17 ± 3°; elbow: 76 ± 11°; carpus: 99 ± 10°; front fetlock: 68 ± 12°; hip: 39 ± 3°; stifle: 68 ± 7°; tarsus: 99 ± 6°; hind fetlock: 94 ± 8°. By comparing the joint angles during a swimming cycle to those observed during classical gaits, this study reveals a greater range of motion (ROM) for most joints during swimming, except for the front and hind fetlocks. This larger ROM is usually achieved through a larger maximal flexion angle (smaller minimal angle of the joints). Finally, the versatility of the system allows us to imagine applications outside the scope of horses, including other large animals and even humans.

Acupuncture has potential in managing axial stiffness in steeplechase racehorses: a blinded prospective randomized preliminary study.

OBJECTIVE: Evaluate the short-term effects of acupuncture on the dynamic manifestations of axial stiffness in steeplechase racehorses. ANIMALS: 12 steeplechase racehorses presenting signs of axial stiffness during training. METHODS: Horses were randomly assigned to either an acupuncture treatment by an experienced certified acupuncturist (n = 6) or no treatment as negative controls (6). The horses' locomotion was evaluated during training before treatment (D0) and 7 (D7) and 14 (D14) days after by their rider and trainer through a questionnaire. Additionally, the improvement of their dorsal flexibility 2 days after treatment was evaluated subjectively at the trot, free jumping at the canter was evaluated by expert clinicians, and free jumping at the trot was evaluated objectively via inertial measurement units. RESULTS: Significantly more horses were improved on D7 and D14 in the acupuncture group (6/6) compared with the control group (1/5; P =.01) according to the scores set by the trainer and riders. Subjective evaluation of the dorsal flexibility also revealed a significant improvement (P = .04) for horses receiving the acupuncture treatment (median improvement score, 0.50 [reference range, 0.5 to 0.9]) compared with control horses (-0.25 [reference range, -0.5 to 0]). CLINICAL RELEVANCE: Acupuncture may be an interesting nondoping strategy to improve clinical signs of axial stiffness and performance on steeplechase racehorses.

Conservative management of equine tarsal collateral ligament injuries may allow return to normal performance.

OBJECTIVE: To describe type and distribution of tarsal collateral ligament (CL) injuries and to assess the long-term outcome in horses treated conservatively. ANIMALS: 78 horses (median age, 7 years [IQR, 4 to 9.75 years]) of different breeds and disciplines. PROCEDURES: Retrospective analysis (2000 through 2020) of horses with tarsal CL lesions diagnosed on ultrasound. The resting time, ability to return to work, and performance level after the injury were compared between horses having a single ligament (group S) or multiple ligaments (group M) affected and according to the case severity. RESULTS: Most of the horses (57/78) presented a single CL injury, while 21 had multiple CLs affected simultaneously, for a total of 108 CLs injured and 111 lesions. In both groups, the short lateral CL (SLCL) was the most commonly affected (44/108), followed by the long medial CL (LMCL; 27/108). Enthesopathies (72.1%) were more frequent than desmopathies alone (27.9%) and involved mostly the proximal insertion of the SLCL and the distal attachment of the LMCL. Conservative treatment (n = 62) consisted mainly of stall rest. The median resting time (120 days [IQR, 60 to 180 days]) did not significantly differ between the 2 groups (group S vs M) or according to the severity. Most horses (50/62) were able to return to work within 6 months. Horses that did not return (12/62) were more likely to have severe lesions (P = .01). Thirty-eight horses were able to perform at a level equal to or higher than before the injury. CLINICAL RELEVANCE: This study highlights the importance of thorough ultrasound assessment of tarsal CL injuries and demonstrates that conservative management is a viable option to allow these horses to return to previous performance level.

Investigation of Thresholds for Asymmetry Indices to Represent the Visual Assessment of Single Limb Lameness by Expert Veterinarians on Horses Trotting in a Straight Line.

Defining whether a gait asymmetry should be considered as lameness is challenging. Gait analysis systems now provide relatively accurate objective data, but their interpretation remains complex. Thresholds for discriminating between horses that are visually assessed as being lame or sound, as well as thresholds for locating the lame limb with precise sensitivity and specificity are essential for accurate interpretation of asymmetry measures. The goal of this study was to establish the thresholds of asymmetry indices having the best sensitivity and specificity to represent the visual single-limb lameness assessment made by expert veterinarians as part of their routine practice. Horses included in this study were evaluated for locomotor disorders at a clinic and equipped with the EQUISYM® system using inertial measurement unit (IMU) sensors. Visual evaluation by expert clinicians allocated horses into five groups: 49 sound, 62 left forelimb lame, 67 right forelimb lame, 23 left hindlimb lame, and 23 right hindlimb lame horses. 1/10 grade lame horses were excluded. Sensors placed on the head (_H), the withers (_W), and the pelvis (_P) provided vertical displacement. Relative difference of minimal (AI-min) and maximal (AI-max) altitudes, and of upward (AI-up) and downward (AI-down) amplitudes between right and left stance phases were calculated. Receiver operating characteristic (ROC) curves discriminating the sound horses from each lame limb group revealed the threshold of asymmetry indice associated with the best sensitivity and specificity. AI-up_W had the best ability to discriminate forelimb lame horses from sound horses with thresholds (left: -7%; right: +10%) whose sensitivity was greater than 84% and specificity greater than 88%. AI-up_P and AI-max_P discriminated hindlimb lame horses from sound horses with thresholds (left: -7%; right: +18% and left: -10%; right: +6%) whose sensitivity was greater than 78%, and specificity greater than 82%. Identified thresholds will enable the interpretation of quantitative data from lameness quantification systems. This study is mainly limited by the number of included horses and deserves further investigation with additional data, and similar studies on circles are warranted.

Retrospective Analysis of the Use of Tiludronate in Equine Practice: Safety on 1804 Horses, Efficacy on 343 Horses.

The objective of this retrospective study was to assess the safety and efficacy of a slow IV administration of 1mg/kg tiludronate in a large number of horses. Each horse that received at least one tiludronate-based treatment between 2006 and August 2019 at Virginia Equine Imaging or Fairfield Equine was included in the study. Concomitant medical treatments, preliminary nonsteroidal anti-inflammatory drug injection and potential side effects were recorded after each administration. Horses for which follow-up was available over 1 year were subject to clinical evolution assessment via lameness grade evolution and performance data when available. Collected data suggest excellent tolerance to tiludronate with only 0.9% of the 2,497 injections (1,804 horses) inducing potential side effects, mild colics being the most frequent. Clinical follow-up was available over more than 1 year for 343 horses. Most horses (>80%) presented an initial lameness score over 1.5/5, approximately half of the population was sound by 30 days and remained so after a year. Mean lameness score improved by more than one grade during the follow-up period compared to initial examination. Performance data were available for 129 horses. One year after treatment, 89 (69%) horses were still competing, 73 (82%) of them at a better or similar level. These data suggest good efficacy of tiludronate over a year after treatment. Despite limitations inherent to any field study, this is the first retrospective study of the use of bisphosphonates in horses combining a large group with long-term follow-ups.

Bone stress injuries and fatigue fractures of the pelvis in endurance horses.

BACKGROUND: Bone stress injuries and fatigue fractures of the pelvis are reported in only a small number of endurance horses. OBJECTIVES: To describe bone stress injuries and fatigue fracture of the pelvis in endurance horses trained and competing on the deep sand surfaces. STUDY DESIGN: Retrospective case series. METHODS: Medical records of horses used for endurance and diagnosed with bone stress injuries and/or fatigue fractures of the pelvis by ultrasound were reviewed. The bone stress injuries and fatigue fractures were classified as affecting the iliac wing, the iliac shaft, the tuber ischiadicum, the rest of the ischium or the pubis and subdivided into four fracture configurations: isolated iliac fracture, isolated fracture of the floor of the pelvis, isolated tuber ischiadicum fracture and multiple fractures. Descriptive statistics were performed overall and on fracture configurations for age, sex, breed, level of activity, affected limbs, previous injuries, development of the injury, seasons in the UAE, physical and dynamic findings and outcome. For each fracture configuration and the outcome, multivariable logistic regression models were developed after univariable logistic regression and collinearity analyses. Significance was set at P ≤ .05. RESULTS: Sixty endurance horses were included; 48% (95% CI: 36%-61%) had isolated iliac fracture, 17% (7%-26%) isolated fracture of the floor of the pelvis, 15% (6%-24%) isolated tuber ischiadicum fracture and 20% (10%-30%) had multiple fractures. Breed (OR, 4.42; 95%CI, 1.02-19.57) was significantly associated with isolated iliac fracture and asymmetry of bone landmarks (OR, 7.42; 95% CI, 1.47-37.45) with isolated tuber ischiadicum fracture. Degree of lameness (OR, 3.08; 95% CI, 1.07-8.9) and trotting on three tracks (OR, 8.62; 95% CI, 1.43-51.9) were significantly associated with the diagnosis of isolated fracture of the floor of the pelvis. MAIN LIMITATIONS: Data acquired in a single country. CONCLUSIONS: Bone stress injuries and fatigue fractures of the pelvis can affect endurance horses trained and competing on deep sand. Isolated bone stress injuries and/or fatigue fractures of the ileum were the commonest followed by multiple pelvic bones involvement. The presence of lameness and trotting on three tracks suggest the presence of bone stress injuries and/or fatigue fractures of the floor of the pelvis; asymmetry of bony landmarks is more commonly detected in horses with bone stress injuries and/or fatigue fractures of the tuber ischiadicum.

Prevalences of lumbosacral articulation anatomic variants identified on nuclear scintigraphy and transrectal ultrasonography of Selle Français Warmbloods, French Standardbred Trotters, and Thoroughbreds and agreement between results from the imaging modalities.

OBJECTIVE: To describe scintigraphic and transrectal ultrasonographic anatomic variants of the lumbosacral (LS) articulation in horses and to determine the agreement between results obtained with each imaging modality. ANIMALS: 243 horses (81 Selle Français Warmbloods, 81 French Standardbred Trotters, and 81 Thoroughbreds). PROCEDURES: A retrospective search of clinical records was conducted to identify horses that had undergone nuclear scintigraphy and transrectal ultrasonography of the LS region of the vertebral column between January 2016 and December 2019. Scintigraphic images were evaluated by 2 observers blinded to the other's results for classification of LS articulation anatomic variants (scintigraphic type); intra- and interobserver agreement were determined. Ultrasonographic images were evaluated for classification of LS intervertebral symphysis anatomic variant (ultrasonographic grade) by 1 observer blinded to horses' identities and scintigraphic findings; agreement analysis was performed between scintigraphic type and ultrasonographic grade. Descriptive and statistical analyses were performed to describe distribution of anatomic variants. RESULTS: The scintigraphic classification system (scintigraphic type) had excellent intra- and interobserver agreement. Agreement between results for scintigraphic type and ultrasonographic grade was moderate (κ = 0.61; 95% CI, 0.52 to 0.70). Anatomic variants of the LS articulation were observed in all groups. The distribution of variants differed significantly among breeds but not sexes. CLINICAL RELEVANCE: Anatomic variations of the LS articulation in horses must be known to avoid misinterpreting them as clinically meaningful findings. Further research is needed to determine potential relationships between these anatomic variants and LS lesions, their clinical manifestations, and their influence on athletic performance.

Evaluation of Allogeneic Bone-Marrow-Derived and Umbilical Cord Blood-Derived Mesenchymal Stem Cells to Prevent the Development of Osteoarthritis in An Equine Model.

Osteoarthritis (OA) is a significant cause of pain in both humans and horses with a high socio-economic impact. The horse is recognized as a pertinent model for human OA. In both species, regenerative therapy with allogeneic mesenchymal stem cells (MSCs) appears to be a promising treatment but, to date, no in vivo studies have attempted to compare the effects of different cell sources on the same individuals. The objective of this study is to evaluate the ability of a single blinded intra-articular injection of allogeneic bone-marrow (BM) derived MSCs and umbilical cord blood (UCB) derived MSC to limit the development of OA-associated pathological changes compared to placebo in a post-traumatic OA model applied to all four fetlock joints of eight horses. The effect of the tissue source (BM vs. UCB) is also assessed on the same individuals. Observations were carried out using clinical, radiographic, ultrasonographic, and magnetic resonance imaging methods as well as biochemical analysis of synovial fluid and postmortem microscopic and macroscopic evaluations of the joints until Week 12. A significant reduction in the progression of OA-associated changes measured with imaging techniques, especially radiography, was observed after injection of bone-marrow derived mesenchymal stem cells (BM-MSCs) compared to contralateral placebo injections. These results indicate that allogeneic BM-MSCs are a promising treatment for OA in horses and reinforce the importance of continuing research to validate these results and find innovative strategies that will optimize the therapeutic potential of these cells. However, they should be considered with caution given the low number of units per group.

An experimentally induced osteoarthritis model in horses performed on both metacarpophalangeal and metatarsophalangeal joints: Technical, clinical, imaging, biochemical, macroscopic and microscopic characterization.

Osteoarthritis is a common cause of pain and economic loss in both humans and horses. The horse is recognized as a suitable model for human osteoarthritis, because the thickness, structure, and mechanical properties of equine articular cartilage are highly comparable to those of humans. Although a number of equine experimental osteoarthritis models have been described in the literature, these cases generally involve the induction of osteoarthritis in just one joint of each animal. This approach necessitates the involvement of large numbers of horses to obtain reliable data and thus limits the use of this animal model, for both economic and ethical reasons. This study adapts an established equine model of post-traumatic osteoarthritis to induce osteoarthritis-associated lesions in all 4 fetlock joints of the same horse in order to reduce the number of animals involved and avoid individual variability, thus obtaining a more reliable method to evaluate treatment efficacy in future studies. The objectives are to assess the feasibility of the procedure, evaluate variability of the lesions according to interindividual and operated-limb position and describe the spontaneous evolution of osteoarthritis-associated pathological changes over a twelve-week period. The procedure was well tolerated by all 8 experimental horses and successfully induced mild osteoarthritis-associated changes in the four fetlock joints of each horse. Observations were carried out using clinical, radiographic, ultrasonographic, and magnetic resonance imaging methods as well as biochemical analyses of synovial fluid and postmortem microscopic and macroscopic evaluations of the joints. No significant differences were found in the progression of osteoarthritis-associated changes between horses or between the different limbs, with the exception of higher synovial effusion in hind fetlocks compared to front fetlocks and higher radiographic scores for left fetlocks compared to the right. This model thus appears to be a reliable means to evaluate the efficacy of new treatments in horses, and may be of interest for translational studies in human medicine.

Ultrasonography-Guided Perineural Injection of the Ramus ventralis of the 7 and 8th Cervical Nerves in Horses: A Cadaveric Descriptive Pilot Study.

Objective: To describe the feasibility and dye diffusion of selective perineural injection of the 7 and 8th cervical nerve (C7 and C8) ramus ventralis under ultrasonographic guidance in horses. Study design: Prospective experimental pilot cadaver study. Animals: Four equine cadavers of similar body weight (420-480 kg) and neck conformation. Methods: Five C7 and five C8 rami were perineurally injected with a dye solution. Anatomic dissections including vertebral canal opening were conducted to confirm nerve dye staining and describe the extent of color diffusion. Results: The ramus ventralis of the spinal cervical nerves was visualized in all cadavers. All the injections were successful in staining a portion of the nerve trunk. Eight rami had a uniform transversal staining of the nerve trunk that longitudinally covered a distance >2 cm. One C7 and one C8 nerve trunk showed incomplete transversal staining with a more concentrated color on its half cranial aspect and a longitudinal coverage of <2 cm. Five injections resulted in dye extending proximally and medially into the epidural space. Volume had no appreciable effect on the extent of nerve staining. A greater proportion of epidural diffusion was found with injections done within less than one cm distally to the articular processes. All injections were considered to be selective for the targeted nerve. Conclusion and clinical relevance: Ultrasonography-guided perineural injection of C7 and C8 ramus ventralis is a feasible technique that may have multiple applications in multimodal analgesia in horses. Further clinical study will be necessary to determine the appropriate drug, dosage, and volume to inject and to confirm its usefulness.

Outcome of Pelvic Fractures Identified in 75 Horses in a Referral Centre: A Retrospective Study.

OBJECTIVE: The aim of this study was to evaluate the reliability of fracture location and horse sporting discipline as prognostic indicators after a pelvic fracture in a referral centre caseload. MATERIALS AND METHODS: Data were collected for the short- and long-term follow-up of all cases with a diagnosis of pelvic fracture in a 7-year period. Information was obtained for 75 horses through a postal and internet survey. The proportion of horses returning to competition following fractures was compared between groups according to the competition discipline and the characteristics of the fracture. RESULTS: Forty-six of 75 horses returned to or began their intended activity. This proportion was significantly lower in the group of horses that sustained a comminuted fracture irrespective of the fracture location (11/25, p = 0.05). The proportion of Standardbred trotter racehorses returning to a sporting career after pelvic fracture (9/20) was not significantly different from horses competing in other disciplines (37/55). Cases of multiple pelvic fractures in the study population, and particularly those involving the acetabulum, had the worst sports prognosis (2/8 and 0/4). Nevertheless, two foals and one yearling (3/5) with isolated fracture of the acetabulum went on to race. CLINICAL SIGNIFICANCE: A clear characterization of the fracture is essential for prognosis, as comminuted fractures seem to entail a poorer athletic prognosis. Despite a lack of significance, prognosis seems poorer for Standardbred trotter racehorses and for cases with acetabulum involvement in multiple fractures. These results should be confirmed in larger samples.

Intra-Articular Injection of 2 Different Dosages of Autologous and Allogeneic Bone Marrow- and Umbilical Cord-Derived Mesenchymal Stem Cells Triggers a Variable Inflammatory Response of the Fetlock Joint on 12 Sound Experimental Horses.

Osteoarthritis is a significant and costly cause of pain for both humans and horses. The horse has been identified as a suitable model for human osteoarthritis. Regenerative therapy with allogeneic mesenchymal stem cells (MSCs) is a promising treatment, but the safety of this procedure continues to be debated. The aim of this study is to evaluate the safety of intra-articular injections of allogeneic MSCs on healthy joints by comparing two different dosages and two different tissue sources, namely, bone marrow and umbilical cord blood, with a placebo treatment on the same individuals. We also assessed the influence of autologous versus allogeneic cells for bone marrow-derived MSC treatment. Twelve clinically sound horses were subjected to injections in their 4 fetlock joints. Each of the three fetlocks was administered a different MSC type, and the remaining fetlock was injected with phosphate-buffered saline as a control. Six horses received 10 million cells per joint, and the 6 other horses received 20 million cells per joint. Clinical and ultrasound monitoring revealed that allogeneic bone marrow-derived MSCs induced significantly more synovial effusion compared to umbilical cord blood-derived MSCs but no significant difference was noted within the synovial fluid parameters. The administration of 10 million cells in horses triggered significantly more inflammatory signs than the administration of 20 million cells. Mesenchymal stem cell injections induced mild to moderate local inflammatory signs compared to the placebo, with individual variability in the sensitivity to the same line of MSCs. Understanding the behavior of stem cells when injected alone is a step towards the safer use of new strategies in stem cell therapy, where the use of either MSC secretome or MSCs combined with biomaterials could enhance their viability and metabolic activity.

Distribution of Pelvic Fractures in Racing and Non-racing Sport Horses: A Retrospective Study of 86 Cases Examined in a Referral Centre.

OBJECTIVE: The aim of this study was to analyse the pelvic fracture distribution and location in a referral centre caseload. MATERIALS AND METHODS: Medical records of 6,717 horses examined in a referral centre over a 7-year period were reviewed to identify all horses diagnosed with a pelvic fracture. Eighty-six horses were identified and divided into three disciplines, namely Thoroughbred racehorses (TBR), Standardbred trotter racehorses (STR) and non-racing sport horses (NRSH). RESULTS: A pelvic fracture was diagnosed in 1.3% of the cases examined during the study period. Prevalence was significantly higher in TBR (4.2%) and, regardless of the discipline, in horses under the age of 6 years (2.2%) (p < 0.01). STR were significantly younger than TBR and NRSH at the time of fracture (median ages = 1, 3 and 4 years old, respectively; p < 0.01). The fractures occurred most frequently in the ilium (44/86). No ilial wing fractures were diagnosed in STR and isolated acetabular fractures were only diagnosed in foals and yearlings. Fatigue fractures were diagnosed in TBR alone, affecting 9/22 TBR (foals and yearlings excluded) and most often located in the ilial wing (7 fatigue fractures out of the 12 ilial wing fractures) (p < 0.01). The median age of horses suffering from a pelvic fatigue fracture was 4 years. CLINICAL SIGNIFICANCE: This study confirms that young horses (under the age of 6 years) as well as TBR are likely to be at higher risk of a pelvic fracture. Fatigue fractures of the ilial wing seem to be a rare condition in STR while they are more frequent in young TBR in training.

Evaluation of standing low-field magnetic resonance imaging for diagnosis of advanced distal interphalangeal primary degenerative joint disease in horses: 12 cases (2010-2014).

OBJECTIVE To report history, findings from clinical examinations and diagnostic imaging, treatment, and outcomes associated with distal interphalangeal primary degenerative joint disease (DIP-PDJD) and to evaluate diagnostic usefulness and limitations of standing low-field MRI, relative to radiography and ultrasonography, for the diagnosis of DIP-PDJD in horses. DESIGN Retrospective case series with nested evaluation study. ANIMALS 12 client-owned horses. PROCEDURES Medical records were reviewed, and data were collected regarding signalment, history, results of physical and diagnostic imaging examinations, treatments, and outcomes of horses that underwent radiography, ultrasonography, and standing MRI for DIP-PDJD. Findings from radiography, ultrasonography, and MRI were recorded, and abnormal findings were graded. The diagnostic usefulness of MRI, relative to radiography and ultrasonography, in the diagnosis of DIP-PDJD in horses was evaluated. RESULTS A diagnosis of DIP-PDJD was established in 12 of 176 (6.8%) horses that underwent MRI examination of a foot for locomotor disorders. Radiography and ultrasonography enabled confirmation of DIP-PDJD in 3 of the 12 horses, and standing MRI enabled confirmation of DIP-PDJD in the remaining 9. Mean grade for thinning joint space and cartilage were significantly greater when determined with MRI, compared with radiography. Mean grade for osteophytes and periarticular bone remodeling were significantly greater when determined with radiography and ultrasonography, compared with MRI. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that DIP-PDJD can be challenging to detect with routine imaging, especially when synovial effusion and periarticular new bone formation are absent. Standing low-field MRI represents a potentially useful diagnostic tool to diagnose advanced DIP-PDJD in horses.

Low field magnetic resonance imaging of the equine distal interphalangeal joint: Comparison between weight-bearing and non-weight-bearing conditions.

This descriptive study aimed to compare the magnetic resonance appearance of the distal interphalangeal joint articular cartilage between standing weight-bearing and non-weight-bearing conditions. Ten forefeet of live horses were scanned in a standing low-field magnetic resonance system (0.27 T). After euthanasia for reasons unrelated to the study, the non-weight-bearing isolated feet were scanned in a vertical positioning reproducing limb orientation in live horses. The same acquisition settings as during the weight-bearing examination were used. Thickness and cross-sectional area of the distal interphalangeal articular cartilage and joint space were measured on tridimensional T1-weighted gradient echo high resolution frontal and sagittal images at predetermined landmarks in both conditions and were compared using a linear mixed-effects model. Frontal images were randomized and submitted to 9 blinded readers with 3 different experience levels for identification of weight-bearing versus non-weight-bearing acquisitions based on cartilage appearance. Weight-bearing limbs had significantly thinner distal interphalangeal cartilage (p = 0.0001) than non-weight-bearing limbs. This change was greater in the distal phalanx cartilage than that of the middle phalanx. Blinded readers correctly identified 83% (range 65 to 95%) of the images as weight-bearing or non-weight-bearing acquisitions, with significantly different results observed among the different readers (p < 0.001) and groups (p < 0.001). These results indicate that distal interphalangeal articular cartilage and particularly cartilage of the distal phalanx thins when weight-bearing compared to the non-weight-bearing standing postmortem conditions and suggest that cartilage abnormalities may be more difficult to identify on weight-bearing standing magnetic resonance imaging.

Synostosis of the first and second ribs in six horses.

CASE DESCRIPTION Over a 2-year period, 6 horses (4 Selle Français, 1 Hanoverian, and 1 Thoroughbred) were referred for evaluation of forelimb lameness. All horses had radiographic evidence of synostosis of the first and second ribs (SFSR). CLINICAL FINDINGS For 1 horse, the SFSR was considered the probable cause of the lameness (grade 3/5), with a shortening of the cranial phase of the stride in the affected limb. For 3 horses, it was considered a possible cause of the lameness (grade 1/5) for the same reason. For 2 horses, SFSR was considered an incidental finding unassociated with any clinical signs. The 4 horses with lameness suspected as attributable to SFSR had a moderate to severe amount of irregularly marginated new bone formation at the site of the SFSR, with a cranial displacement of the first rib, compared with findings for the 2 horses in which the SFSR was considered incidental. A likely congenital abnormality of the first rib was first suspected on nuclear scintigraphy in the 1 horse for which it was performed or on radiography of the caudal cervical portion of the vertebral column (3 horses) or shoulder joint (2 horses). TREATMENT AND OUTCOME The horse in which SFSR was considered the probable cause of the lameness was retired to the field and remained chronically lame. Two of the 3 horses in which SFSR was considered a possible cause of lameness received an IV infusion of tiludronate disodium and mesotherapy over the caudal cervical and cranial thoracic regions; both returned to competition but with poor results. One of the 2 horses with subclinical SFSR never developed lameness on the affected side. No follow-up information was available for the other 2 horses. CLINICAL RELEVANCE SFSR can be an incidental finding in horses, with or without clinical manifestations. This abnormality should be considered as a differential diagnosis for horses with forelimb lameness and associated shortening of the cranial phase of the stride that fails to improve with diagnostic analgesic techniques.

Randomized controlled trial demonstrates the benefit of RGTA® based matrix therapy to treat tendinopathies in racing horses.

A randomized controlled trial was performed on racing horses, to evaluate the efficacy of a new class of therapeutic agents in regenerative medicine-ReGeneraTing Agents® (RGTA®), to treat tendinopathies. Preliminary uncontrolled studies on tendon healing in racing horses with RGTA® (OTR4131)-Equitend® showed encouraging results, justifying performing a randomized, controlled, multicenter study with a two-year racing performance follow up. The objective of this study was to evaluate the effect of Equitend® versus placebo on acute superficial digital flexor tendonitis in racing French Standardbred Trotters (ST). Twenty-two ST were randomly and blindly assigned to receive with a ratio of 2 to 1, a single Equitend® (n = 14) or placebo (n = 8) intralesional injection under ultrasonographic guidance. Horses were evaluated over 4 months, by clinical and ultrasonographic evaluations (day 0, months 1, 2, 4), and their racing performances followed up over the 2 years after treatment. During the first month of treatment, a significant decrease in the cross-sectional area (CSA) was found in the Equitend® group (p = 0.04). After 4 months, the number of Equitend® treated horses with an improved CSA was significantly higher than the placebo-treated horses (p = 0.03571). The Equitend® group returned to their pre-injury performance level, racing in, and winning, significantly more races than the placebo group (p = 0.01399 and 0.0421, respectively). Furthermore, recurrence was significantly higher in the placebo group than in the Equitend® group (71.4% vs 16.6%, p = 0.02442). In conclusion, we measured a significant, short-term, reduction effect on CSA and demonstrated a long-term beneficial effect of intralesional injection of Equitend® for the treatment of superficial digital flexor tendonitis on racing ST, racing 2. 3 times more often than placebo, with 3.3 times fewer recurrences maintaining pre-injury performance level. This study may open the way for the development of a human treatment of tendonitis.

Improvement of the Chondrocyte-Specific Phenotype upon Equine Bone Marrow Mesenchymal Stem Cell Differentiation: Influence of Culture Time, Transforming Growth Factors and Type I Collagen siRNAs on the Differentiation Index.

Articular cartilage is a tissue characterized by its poor intrinsic capacity for self-repair. This tissue is frequently altered upon trauma or in osteoarthritis (OA), a degenerative disease that is currently incurable. Similar musculoskeletal disorders also affect horses and OA incurs considerable economic loss for the equine sector. In the view to develop new therapies for humans and horses, significant progress in tissue engineering has led to the emergence of new generations of cartilage therapy. Matrix-associated autologous chondrocyte implantation is an advanced 3D cell-based therapy that holds promise for cartilage repair. This study aims to improve the autologous chondrocyte implantation technique by using equine mesenchymal stem cells (MSCs) from bone marrow differentiated into chondrocytes that can be implanted in the chondral lesion. The optimized protocol relies on culture under hypoxia within type I/III collagen sponges. Here, we explored three parameters that influence MSC differentiation: culture times, growth factors and RNA interference strategies. Our results suggest first that an increase in culture time from 14 to 28 or 42 days lead to a sharp increase in the expression of chondrocyte markers, notably type II collagen (especially the IIB isoform), along with a concomitant decrease in HtrA1 expression. Nevertheless, the expression of type I collagen also increased with longer culture times. Second, regarding the growth factor cocktail, TGF-ß3 alone showed promising result but the previously tested association of BMP-2 and TGF-ß1 better limits the expression of type I collagen. Third, RNA interference targeting Col1a2 as well as Col1a1 mRNA led to a more significant knockdown, compared with a conventional strategy targeting Col1a1 alone. This chondrogenic differentiation strategy showed a strong increase in the Col2a1:Col1a1 mRNA ratio in the chondrocytes derived from equine bone marrow MSCs, this ratio being considered as an index of the functionality of cartilage. These data provide evidence of a more stable chondrocyte phenotype when combining Col1a1 and Col1a2 siRNAs associated to a longer culture time in the presence of BMP-2 and TGF-ß1, opening new opportunities for preclinical trials in the horse. In addition, because the horse is an excellent model for human articular cartilage disorders, the equine therapeutic approach developed here can also serve as a preclinical step for human medicine.