Developmental Orthopaedic Disease Research Articles

Incidence of disease, injury and death in Thoroughbred foals and yearlings on stud farms in the UK and Ireland.

Up-to-date estimates of early-life morbidity and mortality in Thoroughbreds are lacking. A birth cohort was established on Thoroughbred stud farms across the UK and Ireland. All veterinary interventions for disease or injury between birth and 18 months of age or leaving the study were recorded. Multilevel Poisson regression models with farm and foal as random effects were fitted to estimate incidence rates. Data were available for 3328 foal-months at risk for 275 foals on seven farms. The overall rates of disease and injury requiring veterinary intervention and mortality were 11.9 cases/100 foal-months at risk (95% confidence interval [CI] 8.6-16.2) and 0.2 cases/100 foal-months at risk (95% CI 0.1-0.4), respectively. Almost half (n = 133/273, 49%, 95% CI 43-55) of the live-born cohort required veterinary intervention for musculoskeletal disease or injury, equating to 5.8 cases/100 foal-months at risk (95% CI 4.1-8.2), predominantly reported as developmental orthopaedic disease (DOD). Convenience sampling of participants may affect the generalisability of the findings. Rates of musculoskeletal disease and injury, in particular DOD, on Thoroughbred stud farms were high. Further work to identify modifiable risk factors and further understanding of the economic impact of these conditions and long-term consequences for musculoskeletal health and performance is required.

Disease occurrence and medication usage in pregnant Thoroughbred broodmares and factors associated with early‐life developmental orthopaedic disease in their offspring

Disease occurrence and medication usage in pregnant Thoroughbred broodmares and factors associated with early‐life developmental orthopaedic disease in their offspring

Developmental orthopaedic disease and early osteoarthritis of the temporomandibular joint in a 15‐month‐old Quarter Horse filly

SummaryA 15‐month‐old Quarter Horse filly presented for evaluation of hard swellings over the left temporomandibular joint (TMJ) and the right metatarsophalangeal joint (MTPJ). The TMJ swelling had been noted since she was weaned at 4 months of age and had slowly enlarged since then. Radiographs of both TMJs and the right MTPJ were performed, which revealed severe osteoarthrosis associated with osteochondrosis‐like lesions. The filly was subjected to euthanasia due to the poor prognosis for performance. Computed tomography and post‐mortem examination, including histopathology of the left TMJ, revealed early osteoarthritis (OA) associated with osteochondrosis‐like lesions of the left TMJ and the right MTPJ, while the right hind proximal interphalangeal joint (PIPJ) was diagnosed with early OA.

Growth and development of thoroughbred horses

Research into the growth and development of Thoroughbreds managed on commercial breeding farms is reviewed in this paper. As horses are not meat producing animals, less research has been performed quantifying growth, muscle and bone development than with other production animals. However, variations in growth and development are linked with both value and wastage in young Thoroughbred horses, and can have a long-term impact on racing performance. In Thoroughbred horses, the breeder aims for optimum, or consistent, growth rather than maximum growth. Factors affecting equine growth including environment, nutrition, season and management are discussed in sections covering conception to weaning, weanling to yearling and yearling to 2 years old when horses are nearly fully grown and racing begins. The importance of reference curves for different ages, sex and locations is highlighted. While average daily gain (ADG) declines as the foal gets older, there are seasonal and management influences to consider. Month of birth has an influence on both birthweight and the expected ADG at different ages, which are believed to be related to ambient temperatures and pasture availability for the mare and growing horse. Weaning leads to a growth setback and ADG declines through winter, but increases in spring for the yearling as temperatures and pasture quality and quantity increase. Management factors such as yearling sale preparation are associated with an increase in growth rate, with gains of over 1 kg/day common during the yearling sales preparation process of 6–12 weeks. ‘Home-bred’ horses that do not go to a yearling sale grow at a slower rate but will reach the same endpoint in mature size. Growth of Thoroughbreds is influenced by country, and regions within a country, related to genetics, climate, management practices, market preferences and sale timing. More research is needed into factors affecting growth and development of Thoroughbred horses on commercial farms and the influence differing rates of growth and development have on wastage (such as developmental orthopaedic disease) and commercial outcomes such as yearling sale results and, ultimately, racing performance.

Radiology of the equine hock and proximal cannon

Lameness associated with the hock (tarsus) and proximal cannon (metatarsus) is not uncommon in both performance and leisure horses, and radiographic evaluation is frequently indicated. In the hock, developmental orthopaedic...

Candidate gene analysis of osteochondrosis in Spanish Purebred horses.

Equine osteochondrosis (OC) is a frequent developmental orthopaedic disease with high economic impact on the equine industry and may lead to premature retirement of the animal as a result of chronic pain and lameness. The genetic background of OC includes different genes affecting several locations; however, these genetic associations have been tested in only one or few populations, lacking the validation in others. The aim of this study was to identify the genetic determinants of OC in the Spanish Purebred horse breed. For that purpose, we used a candidate gene approach to study the association between loci previously implicated in the onset and development of OC in other breeds and different OC locations using radiographic data from 144 individuals belonging to the Spanish Purebred horse breed. Of the 48 polymorphisms analysed, three single nucleotide polymorphisms (SNPs) located in the FAF1, FCN3 and COL1A2 genes were found to be associated with different locations of OC lesions. These data contribute insights into the complex gene networks underlying the multifactorial disease OC, and the associated SNPs could be used in a marker-assisted selection strategy to improve horse health, welfare and competitive lifespan.

Pathogenesis of osteochondrosis dissecans: How does this translate to management of the clinical case?

SummaryOsteochondrosis (OC) is the most prevalent developmental orthopaedic disease in the horse. It is a complex disorder because of the interplay of factors that influence the formation of lesions and the ensuing natural healing process, the end result of which determines clinical outcome. The early pathogenetic mechanism of OC has long remained elusive, but recent research has provided compelling evidence for vascular disturbances leading to areas of ischaemic necrosis in the subarticular growth cartilage as the primary event. The aetiological factors that influence the process of the development of lesions are many and comprise both genetic and environmental factors. The genetic background of OC (dissecans) is highly complex with quantitative trait loci associated with some form of OC found on not fewer than 22 of the 33 chromosomes of the horse, and different manifestations and locations of OC having probably different genetic backgrounds. The environmental factors can be divided into nutritional factors and factors influencing the biomechanical loading of joints. Feeding large quantities of easily digestible carbohydrates is a clear risk factor and also the availability of sufficient copper for mares in the last part of pregnancy is important. Factors influencing the biomechanical loading of joints include the exercise regimen of foals, paddock size and roughness of terrain, and conformation. Equine OC is rarely a life‐threatening disease and the prognosis of (surgical) treatment is good to very good. However, the impact on economics of the equine industry and on horse welfare is large. This impact can only be lessened by the judicious management of both horse breeding and horse husbandry. Some of the measures that would alleviate the burden of OC conflict with (commercial) pressures from the industry and a balance between human‐imposed breeding and performance goals and the interest of the animal itself should be sought.

Dwarfism associated with chondrodysplasia in a red deer (Cervus elaphus)

OSTEOCHONDROSIS is a developmental orthopaedic disease characterised by the failure of endochondral ossification and premature closure of the growth plates. Chondrodysplasia and dyschondroplasia are descriptive terms implying a primary defect...

Association of breeding conditions with prevalence of osteochondrosis in foals

Osteochondrosis (OC) is the most common developmental orthopaedic disease in horses and represents a major problem to the horse industry. The complete mechanism of this multifactorial disease is not yet...

Elbow arthroscopy: Indications, approaches and syndromes

SummaryElbow arthroscopy is not commonly performed and can be challenging due to surrounding neurovascular and muscle structures. Three approaches provide access to the various compartments and joint surfaces of the elbow except the proximal radius. Indications for diagnostic arthroscopy include septic arthritis, osteochondral chip fracture, assisted reduction of adjacent epiphyseal fractures, developmental orthopaedic disease and staging of osteoarthritis. Outcome is determined by extent of joint disruption and control of infectious agents.

The role of diet in the prevention and management of several equine diseases

Modern feeding and housing practices of horses are typically directed at achieving a high level of athletic performance. There are some unfortunate consequences including an increased incidence of disease. Some of these diseases can be directly linked to dietary practices, while in others diet contributes as an important co-factor. Breeding practices to select for specific traits have also inadvertently resulted in the preferential selection of horses with genetic mutations within several breeds. In several of these genetic disorders specific dietary management is required for affected horses to achieve an acceptable level of performance. Diseases in which diet has a significant influence are discussed including equine metabolic syndrome, laminitis, diseases attributed to deficiency of vitamin E and/or selenium, exertional myopathies, nutritional secondary hyperparathyroidism, hyperkalaemic periodic paralysis, and the developmental orthopaedic disease complex.

A genome-wide association study of osteochondritis dissecans in the Thoroughbred.

Osteochondrosis is a developmental orthopaedic disease that occurs in horses, other livestock species, companion animal species, and humans. The principal aim of this study was to identify quantitative trait loci (QTL) associated with osteochondritis dissecans (OCD) in the Thoroughbred using a genome-wide association study. A secondary objective was to test the effect of previously identified QTL in the current population. Over 300 horses, classified as cases or controls according to clinical findings, were genotyped for the Illumina Equine SNP50 BeadChip. An animal model was first implemented in order to adjust each horse's phenotypic status for average relatedness among horses and other potentially confounding factors which were present in the data. The genome-wide association test was then conducted on the residuals from the animal model. A single SNP on chromosome 3 was found to be associated with OCD at a genome-wide level of significance, as determined by permutation. According to the current sequence annotation, the SNP is located in an intergenic region of the genome. The effects of 24 SNPs, representing QTL previously identified in a sample of Hanoverian Warmblood horses, were tested directly in the animal model. When fitted alongside the significant SNP on ECA3, two of these SNPs were found to be associated with OCD. Confirmation of the putative QTL identified on ECA3 requires validation in an independent sample. The results of this study suggest that a significant challenge faced by equine researchers is the generation of sufficiently large data sets to effectively study complex diseases such as osteochondrosis.

Dwarfism associated with chondrodysplasia in a red deer (Cervus elaphus)

OSTEOCHONDROSIS is a developmental orthopaedic disease characterised by the failure of endochondral ossification and premature closure of the growth plates. Chondrodysplasia and dyschondroplasia are descriptive terms implying a primary defect...

Risk factors for the presence and extent of Developmental Orthopaedic Disease in the limbs of young horses: Insights from a count model

Developmental Orthopaedic Disease (DOD) in limb joints is frequent, can cause lameness and is a major cause of economic losses for the horse breeding industry. Studies on risk factors for DOD usually dichotomise the outcome to presence/absence without considering the extent of the disease, which can be appreciated by the number or the severity of the lesions. The aim of this study was to assess the effects of growth, exercise conditions and feeding practices on the number of radiographic findings (RF) of DOD in a cohort of horses, assuming that the risk factors associated with the presence of the disease and the number of RF may differ. We recruited broodmares on 21 stud farms in the Normandy region, France in 2002–2004. The stud farms were visited regularly to collect growth, exercise conditions, and feeding practices data from the end of the gestation to the weaning of the foal. The carpus, the front and hind digits, the tarsus and the stifle of the foals were radiographed at approximately six months of age. Each foal was classified according to the absence (no RF) or presence (≥1 RF) of DOD and to the number of RF. A zero-inflated Poisson model was used to simultaneously determine risk factors for presence/absence and for the number of RF of the disease. The convenience sample consisted of 378 foals, 53.1% of which did not have any RF. The mean number of RF per foal was 1.25 and the variance was 2.80. Comparing to the Poisson, negative binomial, and zero-inflated negative binomial regressions, the zero-inflated Poisson model was found to be best suited for these data. Of the 295 foals with complete data, three risk factors were significantly associated with a higher risk of being affected by DOD: high wither height increase, large group size in pasture and large pasture size. Seven risk factors were associated with the number of RF: wither height at 30 days of age, age of the mare, breed, regularity of exercise, Ca/P level in the mare and foal rations, group size in pasture, and the type and frequency of handling. This study shows that risk factors vary for the presence and extent of DOD, and that the use of a count model achieves a more detailed determination of risk factors for the presence of DOD and for the number of RF of DOD compared to the more conventional dichotomy presence/absence of the disease.

Genome‐wide association analysis of osteochondrosis of the tibiotarsal joint in Norwegian Standardbred trotters

Osteochondrosis (OC), a disturbance in the process of endochondral ossification, is by far the most important equine developmental orthopaedic disease and is also common in other domestic animals and humans. The purpose of this study was to identify quantitative trait loci (QTL) associated with osteochondrosis dissecans (OCD) at the intermediate ridge of the distal tibia in Norwegian Standardbred (SB) using the Illumina Equine SNP50 BeadChip whole-genome single-nucleotide polymorphism (SNP) assay. Radiographic data and blood samples were obtained from 464 SB yearlings. Based on the radiographic examination, 162 horses were selected for genotyping; 80 of these were cases with an OCD at the intermediate ridge of the distal tibia, and 82 were controls without any developmental lesions in the joints examined. Genotyped horses descended from 22 sires, and the number of horses in each half-sib group ranged from 3 to 14. The population structure necessitated statistical correction for stratification. When conducting a case-control genome-wide association study (GWAS), mixed-model analyses displayed regions on chromosomes (Equus callabus chromosome - ECA) 5, 10, 27 and 28 that showed moderate evidence of association (P ≤ 5 × 10(-5); this P-value is uncorrected i.e. not adjusted for multiple comparisons) with OCD in the tibiotarsal joint. Two SNPs on ECA10 represent the most significant hits (uncorrected P=1.19 × 10(-5) in the mixed-model). In the basic association (chi-square) test, these SNPs achieved statistical significance with the Bonferroni correction (P=0.038) and were close in the permuted logistic regression test (P=0.054). Putative QTL on ECA 5, 10, 27 and 28 represent interesting areas for future research, validation studies and fine mapping of candidate regions. Results presented here represent the first GWAS of OC in horses using the recently released Illumina Equine SNP50 BeadChip.

Growing more durable equine athletes

Discussions on growing more durable equine athletes often revolve around developmental orthopaedic disease (DOD). What degree of DOD, if any, is acceptable or inconsequential to long-term athletic performance remains a question. Much effort has been directed toward diminishing or eliminating the incidence and severity of DOD, but with limited success. We must continue to define what degree the management decisions affect the horse during different stages of its growth. It would seem logical that the most profound influence would occur during the most rapid periods of growth. Therefore, concerns have been directed toward the last third of gestation and the possible indirect effect that broodmare management has on foetal development. The early postnatal period is another period of rapid growth; thus, the effect of broodmare management on lactation may affect the growth of the foal. Management will also have a direct effect on growth and development from weaning through to maturity. Recent research in other species as well as in horse suggests that genetic predisposition is the primary determinant of DOD. Non-nutritional management also may have significant effects on articular and skeletal health and athletic durability. Much effort has been directed toward nutrition and potential impact on DOD, but with limited success. Except for overt deficiencies, or perhaps excessive imbalances, nutrition does not appear to be a primary determinant of DOD, particularly of focal lesions associated with osteochondrosis. However, nutrition may serve a secondary role in diminishing the severity and incidence of DOD in horses genetically predisposed to such conditions. Producing horses that will have long-term and productive athletic careers requires sound management that starts at conception and continues throughout the life of the horse.

Association of growth, feeding practices and exercise conditions with the prevalence of Developmental Orthopaedic Disease in limbs of French foals at weaning

Developmental Orthopaedic Disease (DOD) in limb joints of horses is frequent and is a common cause of pain and lameness. DOD is a multifactorial disease involving genetics, growth, feeding practices and exercise conditions leading to joint injuries. However, there is no clear understanding of the contribution of each factor. The aim of this cohort study was to assess the adjusted effects of breed and gender, growth, feeding practices and exercise conditions on the prevalence of DOD in the limbs of foals at weaning and on the prevalence restricted to osteochondrosis (OC).Twenty-one farms in Normandy, France, were convenience sampled and enrolled in a cohort study. The study sample consisted of 401 foals from 3 breeds, followed from the 8th month of pregnancy of the mares until weaning period at approximately 6 months of age of the foals. Stud farms were regularly visited to collect growth, feeding practices and exercise conditions data. The carpus, the front and hind digits, the hock and the stifle of the foals were X-rayed at the end of follow-up. Foals were categorised as affected or unaffected by DOD or by OC. Two mixed-effects logistic regression models were used to determine risk factors for DOD or OC, adjusting for clustering by farm.Of the 378 foals with complete data, 47% (95% CI: 42–52) were affected by DOD and 36% (95% CI: 31–41) by OC. Risk was significantly increased for DOD and for OC in Warmblood foals compared to Thoroughbreds (OR 2.8; 95% CI: 1.2–6.5 for DOD, OR 2.9; 95% CI: 1.1–7.5 for OC), in foals with a high wither height at 30 days of age, and in foals with a rapid increase of wither height (for DOD only). Exercise conditions such as large area of pasture, some irregular exercise, or some batch changes were also significant risk factors for DOD or OC. No association was found with quantitative feeding practices; it was likely due to the limited variability of horse regimens and to the partial inclusion of nutritional effects in other factors such as breed and growth. In order to reduce the prevalence of DOD or OC in foals, following the growth and reducing nutritional supply in subjects growing fast, limiting the pasture areas offered and providing a regular exercise to foals seems appropriate. To our knowledge, to date the assessment of adjusted effects of potential risk factors for DOD has never been proposed.

Dorsoproximal proximal phalanx osteochondral fragmentation in 117 Warmblood horses

The objective of the present study was to determine clinical and arthroscopic characteristics associated with dorsoproximal proximal phalanx (P1) fragments in Warmblood horses, as well as to examine their histopathological appearance. One hundred sixty-eight fragments were removed from 150 fetlocks of 117 Warmblood horses. Details of signalment and results of clinical examination were collected prior to surgery. After arthroscopic fragment removal and joint evaluation for synovial and/or cartilage abnormalities, the fragments were measured and evaluated histopathologically. The vast majority of the fragments (95.2%) were found medially, without predilection for front or hind limbs. In 10% of the joints, more than one fragment was present. The mean size of the fragments was 6.8 +/- 2.6 mm. Only eight horses presented fetlock-related lameness. Horses of seven years of age and older (OR = 13.32; p = 0.033) and the presence of more than one fragment (OR = 11.12; p = 0.016) were significantly associated with lameness. Arthroscopic evaluation revealed one or more abnormalities in 50.7% of the joints. On histopathology, osteochondral fragments presented as a bony center covered with smooth hyaline cartilage on one side and some fibrous tissue on the other side. No clear histopathological signs were indicating precisely their origin. In Warmblood horses with dorsoproximal P1 fragments, the age (seven years and older) and the presence of more than one fragment in a fetlock significantly increased the risk of lameness. The osteochondral dorsoproximal P1 fragments could be defined as a developmental orthopaedic disease.

Developmental orthopaedic disease in limbs of foals: between-breed variations in the prevalence, location and severity at weaning

Developmental orthopaedic disease (DOD) affects all breeds and is a common cause of pain and lameness for horses in sports. A thorough knowledge of between-breed variations for the prevalence of DOD, for its distribution among the various joints and for its severity at earlier stages in the disease process is needed in order to improve the relevance and the cost-effectiveness of DOD screening protocols. However, no prevalence study for DOD simultaneously performed on several breeds with similar farming systems and based on radiographic findings (RF) on quite a large number of joints and views, has been reported earlier. The objective of this study was to describe variations in the prevalence, location and severity of DOD in foals at weaning among Warmbloods (Wb), Standardbreds (St) and Thoroughbreds (Tb) with similar farming systems. DOD assessment was based on RF on the limb joints. A total of 392 foals from 21 volunteer stud farmers were included. To determine the statuses of foals regarding DOD, they were X-rayed on the front- and hind-limb digit, carpus, hock and stifle joints. X-ray data were analysed by three experienced equine veterinarians who gave a common assessment about the entity and the severity of RF. Between-breed variations were analysed in two steps: the first implemented for each anatomical site; the second considered only foals affected by DOD to explore RF association patterns on the affected sites, at foal level. The three breeds were represented by 25.0% of Wb, 41.1% of St and 33.9% of Tb. DOD was present in 66.3% of the foals (95% confidence interval (CI) = 61.6% to 71.0%). Prevalence of foals affected by DOD and distribution of the RF severity score on the anatomical sites differed depending on the breed: Wb foals seemed to be the most affected by DOD. Cluster analyses showed no clear association among sites. However, Wb and Tb foals were preferentially classified together because they were affected on the same sites, whereas St foals were distributed in other classes. The most severely affected sites were the proximal part of the hock and the femoro-patellar joint for Wb and St foals, and the fore fetlock and the distal part of the hock for Tb foals. This is the first epidemiological study reporting between-breed variations in DOD distribution and severity, for the limb joints of foals. These results contribute to broaden the knowledge on DOD and are of great interest to improve detection of DOD within a particular breed.

DOD incidence in thoroughbred foals between 23 and 45 weeks of age – growth, nutrition and genetic factors

The aim of this work was to understand the extent of developmental orthopaedic disease (DOD) multifactorial aetiology factors. Growth pattern, nutritional and genetic factors were studied on a population of 89 thoroughbred foals aged between 23 and 45 weeks: growth curve characteri- sation, feeding plan analysis and genetic study approach to stallion progeny were accomplished in order to evaluate their influence on DOD frequency. A statistically significant difference was found between DOD positive and DOD negative foals' weight; fillies were found to be the sub-population responsible for this difference. A shortage of energy and protein was found during the period con- sidered and there was an excess in calcium and phosphorus by the end of the period. Genetic factor analysis indicated an intensive utilisation of stallions with the higher results of DOD positive foals although the breeding system's objectives regarding this aspect remained unclear. Developmental Orthopaedic Diseases (DOD) / osteochondrosis / growth pattern / nutrition / sire evaluation