Progression of femoropatellar osteochondrosis in nine young horses. Clinical, radiographic and arthroscopic findings

Prevalence of Juvenile Osteochondral Conditions in Yearling Thoroughbred Racehorses in Southern Brazil

This study aimed to investigate the prevalence of juvenile osteochondral conditions (JOCCs) in yearling Thoroughbred (TB) racehorses in Southern Brazil, as well as to examine the same animals studied as weanlings by Bastos et al. (2017) and compare the radiographic findings for the two ages. Radiographs of 76 male and female TB yearlings from Paraná State, Southern Brazil, were investigated. The proximal interphalangeal, metacarpophalangeal/metatarsophalangeal (MC/MT), tarsal, and femorotibial (FT) joints were evaluated using 24 radiographic projections. The evaluation consisted of a severity index (rated as 0, 1, 2, 4, or 8), the sum of which resulted in an osteoarticular status (OAS) of good, intermediate, or poor for each animal. Radiographs of 92% of the investigated animals presented at least one finding consistent with JOCCs. The most affected region was the tarsal joint (72.9%), followed by the FT (50%), MT (25%), and MC (23%) joints. Thirty-three (43.4%) horses presented a decline in their OAS, whereas nine (11.8%) presented an improvement from the weanling to yearling age. The radiographic findings suggest that JOCCs are frequent in TB yearlings, but the meaning and relevance of these radiographic findings require further study.

Problems and pointers in osteochondrosis: Twenty years on

Twenty years ago a supplement of Equine Veterinary Journal was devoted to equine osteochondrosis (OC) and recognised the importance of this developmental disease to the equine industry. In the accompanying editorial several controversial issues were identified and a number of areas for further research were highlighted. Today, equine OC is still a major clinical problem, but the on-going research has resulted in much improved knowledge and understanding of this highly complicated disease. There is still conflicting evidence on the prevalence of OC due to the dynamic character of the condition, widely varying definitions in the literature, and the range of joints affected. Nevertheless there is now convincing evidence that early vascular damage, leading to chondronecrosis, is the major mechanism of onset. The aetiological factors that determine whether a horse will develop clinical signs of OC remain obscure and the complex nature of OC and its multi-factorial character has been clearly demonstrated by genetic studies. These have shown a multitude of loci on a variety of chromosomes linked to osteochondrotic phenotypes, depending on the type of manifestation of OC, the joint involved and the breed. The controversy surrounding the possible key role of copper in the pathogenesis of OC in the early 1990s has evolved into a more limited contribution to repair thus making it just one of the many environmental factors that may have an effect on the occurrence of OC, but not a decisive one. The semantic debate concerning the most appropriate nomenclature seems to have crystallised into a consensus on terminology at three levels: OC or osteochondritis dissecans (OCD) for the disturbance in the process of endochondral ossification, juvenile ostechondral conditions (JOCC) for all joint and growth plate related disorders, and developmental orthopaedic diseases (DOD) for the full range of skeletal conditions in young horses. Future progress in improved management of OC can be expected from more research on cellular and molecular processes and the influences that determine the process of endochondral ossification, the process of articular cartilage maturation, and from epidemiological studies quantifying the long-term effects of OC on health and performance.

Osteochondrosis lesions of the lateral trochlear ridge of the distal femur in four ponies

Lesions of the lateral trochlear ridge (LTR) of the distal femur were investigated in four pony or pony cross horses. The animals were all geldings and were six to 15 months of age. Lesions were bilateral in three ponies and unilateral in one. Femoropatellar joint effusion and lameness were present in two ponies; clinical signs were absent in the others. The proximal LTR was affected in all four animals. The radiographic appearance of the lesions was a subchondral defect containing mineralised bodies. Arthroscopic and postmortem examination findings included an osteochondral flap, a fissured or irregular articular surface and a smooth surface overlying focally thickened cartilage that extended into subchondral bone. Thickened articular cartilage was a histological feature of all the lesions. Among the other histological features, the most common were chondronecrosis, chondrocyte clusters, phenotypically abnormal chondrocytes, horizontal fissures at the osteochondral junction and retained blood vessels. The signalment of the four ponies, their clinical signs and the pathological features of their lesions were consistent with osteochondrosis of the LTR in horses. The use of multiple criteria was considered to be important in making a specific diagnosis.

Early Lesions of Articular Osteochondrosis in the Distal Femur of Foals

Failure of the cartilage canal blood supply to epiphyseal growth cartilage has been implicated in the pathogenesis of articular osteochondrosis in horses and other animal species. In a previous study of the developmental pattern of the blood supply in the tarsus of foals, early lesions of osteochondrosis were consistently found in regions where the cartilage canal vessels traversed the chondro-osseous junction. The developmental pattern of blood vessels has also been described in the distal femoral epiphysis; however, the group of foals examined in that study did not have lesions of osteochondrosis in this location. Therefore, the relationship between the occurrence of early lesions of osteochondrosis and the developmental pattern of the blood supply to epiphyseal growth cartilage in this site in foals has not been examined. Distal femora were collected from 30 fetuses and foals (up to 11 months old) submitted for postmortem examination. Sections from the lateral trochlear ridge and medial femoral condyle of both hind limbs were examined histologically. Sixteen cartilage lesions were found in 7 of the 30 fetuses and foals. All lesions contained evidence of cartilage canal necrosis and ischemic chondronecrosis. The lesions were located in regions where cartilage canal vessels traversed the chondro-osseous junction, as previously observed in the tarsus. The location and morphology of lesions indicated that a subclinical stage of ischemic chondronecrosis existed that preceded and predisposed to the development of osteochondrosis dissecans and subchondral bone cysts.

Incidence of osteochondrosis (dissecans) in Dutch warmblood horses presented for pre-purchase examination

Data are lacking in the literature regarding the incidence of osteochondrosis (dissecans) [OC(D)] in relation to lameness evaluation in Dutch Warmblood horses. The objective of this retrospective study was to assess the incidence of radiological abnormalities consistent with osteochondrosis or osteochondrosis dissecans in 1,231 sound Dutch Warmblood (DW) horses presented for pre-purchase examination. Standardised (Dutch) pre-purchase examination protocols were evaluated. The pre-purchase examination included a clinical, lameness and radiological evaluation, performed at a private equine clinic in the Netherlands. Radiographical examination included views of the distal (DIP) and proximal (PIP) interphalangeal, metacarpo- and metatarsophalangeal (MCP/MTP), tarsocrural (TC) and femoropatellar (FP) joints. Radiographical evidence of OC(D) was found in 44.3% of clinically sound DW horses. In this study, 443 horses (36%, n = 1,231) had evidence of OCD and 102 horses (8.3%, n = 1,231) had evidence of OC on pre-purchase radiographs. The results also indicated that the TC joints were significantly more likely to be affected. A considerable number of horses did not demonstrate any lameness, although radiographs revealed OC(D).

New Surgical Treatments for Osteochondritis Dissecans and Subchondral Bone Cysts

Osteochondritis dissecans (OCD) and subchondral bone cysts (SBCs) occur commonly and at many different locations in equine limbs and can lead to secondary osteoarthritis when left untreated. Depending on the location and extent of the lesion, arthroscopic surgical debridement may be an effective treatment for returning a horse to athletic soundness. In many cases, however, additional techniques to improve the healing response in bone and cartilage are needed so as to preserve articular function. Methods for improving cartilage repair (ie, restoration of damaged cartilage)or regeneration (ie, reformation or recreation of new articular cartilage) in select cases of OCD and SBCs are discussed.

Extracellular matrix changes in early osteochondrotic defects in foals: a key role for collagen?

Osteochondrosis (OC) is the most important developmental orthopaedic disease in the horse. Despite some decades of research, much of the pathogenesis of the disorder remains obscure. Increasing knowledge of articular cartilage development in juvenile animals led to the presumption that the role of collagen in OC might be more important than previously thought. To study collagen characteristics of both cartilage and subchondral bone in young (5 and 11 months of age) horses, samples were taken of subchondral bone and articular cartilage from a group of 43 Dutch Warmblood foals and yearlings that suffered from varying degrees of OC. Based on a histological classification, lesions were graded as early, middle and end stage. Collagen content and some posttranslational modifications (lysyl hydroxylation, hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) cross-links) were determined, as was proteoglycan content. Data were compensated for site effects and analysed for differences due to the stage of the lesion. In early lesions total collagen was significantly decreased in both cartilage and subchondral bone of 5- and 11-month-old foals. Also in cartilage, HP cross-linking was reduced in the early lesions of 5- and 11-month-old foals, while LP cross-linking was decreased in subchondral bone of the end-stage lesions of both 5- and 11-month-old foals. Hydroxylysine content was unaffected. Collagen content remained reduced in cartilage from middle- and end-stage lesions, but returned to normal in subchondral bone. In cartilage there was a decrease in proteoglycan content in the end-stage lesions of both age groups. Thus, alterations of the collagen component, but not of the proteoglycan component, of the extracellular matrix might play a role in early OC. More severe lesions show a more general picture of an unspecific repair reaction. Biomarkers of collagen metabolism can be expected to be good candidates for early detection of OC.

Influence of liver copper status of mare and newborn foal on the development of osteochondrotic lesions

REASON FOR PERFORMING STUDY

To elucidate the highly contentious role of copper in the pathogenesis of osteochondrosis.

HYPOTHESIS

There would be no relationship between liver copper concentration of mares and foals and incidence of radiographically detectable osteochondrotic lesions in foals and yearlings was tested.

METHODS

Liver copper concentration was assessed in biopsies taken within 4 days after birth from both mares and foals and from the same foals at age 5 months. Biopsies were taken in the standing, sedated animal under ultrasonographic guidance. Radiographs were taken of both hocks (lateromedial, dorsoplantar and dorsomedial-plantarolateral oblique views) and stifles (lateromedial and caudolateral-craniomedial oblique views) at ages 5 and 11 months and scored for the presence and severity of osteochondrotic lesions.

RESULTS

Copper concentrations in newborn foals were high with a large variation (351 +/- 201 mg/kg DM). They declined until reaching values comparable to those in mature animals at 5 months (20 +/- 8 mg/kg DM; mares: 19 +/- 20 mg/kg DM). Radiographic osteochondrotic lesions decreased in number and severity from 5 to 11 months. This pattern was more predominant in the stifle than in the hock, as has been described previously.

CONCLUSIONS

There was no relationship between foal or mare liver copper concentration and osteochondrosis status at either 5 or 11 months. However, osteochondrotic lesions in foals with low-level copper status at birth decreased significantly less in number and severity than those in foals with high-level copper status at birth.

POTENTIAL RELEVANCE

It is concluded that copper is not likely to be an important factor in the aetiopathogenesis of osteochondrosis, but this study indicates that there may be a significant effect of high copper status on the natural process of repair of early lesions.

Osteitis of the axial border of the proximal sesamoid bones in horses: eight cases (1993-1999)

OBJECTIVE

To determine clinical, radiographic, and scintigraphic abnormalities in and outcome of horses with septic or nonseptic osteitis of the axial border of the proximal sesamoid bones.

DESIGN

Retrospective study.

ANIMALS

8 horses.

PROCEDURE

Data collected from medical records included signalment; history; horse use; severity and duration of lameness; results of perineural anesthesia, radiography, ultrasonography, and scintigraphy; and outcome following surgery.

RESULTS

Five horses did not have any evidence of sepsis; the other 3 had sepsis of the metacarpophalangeal or metatarsophalangeal joint or the digital synovial sheath. All horses had a history of chronic unilateral lameness. Three of 5 horses improved after diagnostic anesthesia of the metacarpophalangeal or metatarsophalangeal joint; the other 2 improved only after diagnostic anesthesia of the digital synovial sheath. Nuclear scintigraphy was beneficial in localizing the source of the lameness to the proximal sesamoid bones in 4 horses. Arthroscopy of the palmar or plantar pouch of the joint or of the digital synovial sheath revealed intersesamoidean ligament damage and osteomalacia of the axial border of the proximal sesamoid bones in all horses. All 5 horses without sepsis and 1 horse with sepsis returned to their previous uses.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that osteitis of the axial border of the proximal sesamoid bones is a distinct entity in horses that typically is associated with inflammation of the associated metacarpointersesamoidean or metatarsointersesamoidean ligament and may be a result of sepsis or nonseptic inflammation. Arthroscopic debridement may allow horses without evidence of sepsis to return to their previous level of performance.