OSTEOCHONDROSIS IN THE LATERAL FEMORAL CONDYLES OF A HORSE

Osteochondrosis of the lateral femoral condyles was diagnosed radiographically in an 8-month-old, female Arabian horse, which had been presented with a hindlimb lameness. The diagnosis was confirmed by gross and microscopic pathology. The location of the lesions was considered unusual for osteochondrosis in the horse.     

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

A 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.     

ENLARGING BILATERAL FEMORAL CONDYLAR BONE CYSTS WITHOUT SCINTIGRAPHIC UPTAKE IN A YEARLING FOAL

Bilateral subchondral bone cysts of the femoral condyles were diagnosed by conventional radiography in a 14 month old Appaloosa colt. Surgical debridement was performed, and over the next 18 months the appearance of the cysts was evaluated with radiography and bone scintigraphy. On the preoperative scintigrams, increased radiopharmaceutical uptake was associated with the cysts. Despite continued radiographic enlargement, the cysts did not demonstrate increased radiopharmaceutical uptake post-operatively.     

青年猪骨软骨病病理组织学变化与分类

研究了265头青年猪1 060个关节(附关节和腕关节各530个)骨软骨病的病理组织学变化.肉眼观察主要表现为患部关节软骨变色、充血,关节面粗糙、裂开、糜烂或凹陷,并根据其损伤程度进行分类,即正常、轻度、中度和严重,分别占21.7%、33.3%、29.0%、16.0%.显微观察特征为关节软骨局部增厚,软骨细胞增生、肥大;在一些区域软骨细胞变性、坏死,坏死区易形成裂隙;骨质内形成软骨岛.结论:青年猪有很高的骨软骨病发病率,后肢比前肢严重,并表现典型的骨软骨病组织病理学特征.     

Osteochondrosis and osteochondral fragments in Standardbred trotters: prevalence and relationships

Reasons for performing study: Developmental orthopaedic diseases (DOD) such as osteochondrosis (OC)/osteochondrosis dissecans (OCD), palmar/plantar osteochondral fragments (POF), ununited palmar/plantar eminences (UPE) and dorsoproximal first phalanx fragments are well recognised in the horse. Aetiopathogeneses are controversial and molecular genetic screening of DNA has recently been employed for their elucidation. Precise phenotypic definition and knowledge of breed‐specific prevalence and interrelations are essential for the interpretation of following genomic studies in Standardbred trotters. Objectives: To assess the prevalence, trend of development and interrelation of DOD in tarsocrural, metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joints in Standardbred trotters. Methods: The tarsocrural and MCP/MTP joints of 464 Norwegian Standardbred yearlings were radiographed and the prevalence and interrelation of osteochondral lesions calculated. Results: Osteochondral lesions were diagnosed in 50.7% of the horses. The prevalence of tarsocrural OC/OCD at the distal intermediate ridge of the tibia (DIT) and the lateral trochlear ridge of the talus (LTT) was 19.3%. The prevalence of OC/OCD in MCP joints was 3.6%, whereas those of POF and UPE in MCP/MTP joints were 23.1 and 3.9%, respectively. Interrelation was evident for 1) most equivalent lesions in joint homologues, 2) OCD DIT and OCD LTT and 3) POF and UPE. Lesions in hock and fetlock joints were generally not significantly associated. Conclusions: The prevalence of tarsocrural OC/OCD in Norwegian Standardbreds is apparently increasing, whereas that of other articular DOD appears stable. Association analyses verify bilateralism for most equivalent lesions and suggest aetiological resemblance also between other lesions. The absence of a significant association between tarsocrural OCD and POF implies that the lesions must be considered statistically different disorders. Potential relevance: The prevalence results emphasise that DOD should be considered in Standardbred breeding regimens (e.g. by sire selection subsequent to progeny testing). Also, improved phenotypic definitions will help elucidate the true causal genes in following genomic studies.     

Epiphyseal cartilage canal blood supply to the tarsus of foals and relationship to osteochondrosis

REASON FOR PERFORMING STUDY: Pathological changes in the blood supply to growth cartilage have been implicated in the pathogenesis of osteochondrosis (OC) in horses, but have not been reported using vascular perfusion techniques. OBJECTIVE: To describe the developmental pattern of cartilage canal vessels in the distal tibial epiphysis and talar growth cartilage of foals. METHODS: Nine foals bred from parents with OC were sacrificed between the ages of 0 and 7 weeks to undergo a barium perfusion procedure. The distal end of the tibia and the entire talus were cleared in methyl salicylate and perfused vessels studied in the intact bones. Slabs with a thickness of 4-5 mm from 3 predilection sites for OC were examined in the stereomicroscope and with light microscopy. RESULTS: Cartilage canals were present for a limited period of growth. Perfused vessels initially entered canals from the perichondrium. Vessels in the proximal portion of canals retained their perichondrial arterial source throughout. With time, the ossification front advanced to incorporate the mid-portion of canals; and anastomoses formed between canal vessels and subchondral vessels. A shift occurred and vessels in the distal terminus of canals came to use subchondral vessels as their arterial source. Twelve histological lesions were found in 7 foals. All contained necrotic vessels surrounded by necrotic growth cartilage and 3 caused macroscopically visible delay in endochondral ossification. Lesions were located where vessels traversed the ossification front to enter the distal terminus of canals. CONCLUSION: Cartilage canal vessels are particularly susceptible to failure at the point where they cross the ossification front, with consequences for the viability of those chondrocytes that depend on them. POTENTIAL RELEVANCE: A better understanding of how lesions of OC arise may improve the ability to identify, monitor, prevent and treat this disorder. Involvement of cartilage canals in the pathogenesis of equine tarsal OC plausibly explains several clinical features of this disease.     

Equine hospital data as a source for study of prevalence and heritability of osteochondrosis and palmar/plantar osseous fragments of Swedish Warmblood horses

Reasons for performing study: Disturbances in skeletal development, primarily osteochondrosis (OC) and palmar/plantar osseous fragments (POF), have been commonly reported as problems in young horses. However, there are few reports of such findings for epidemiological analyses or breeding purposes. Objectives: To evaluate equine hospital data as a possible source of information for genetic evaluations by estimating prevalence and heritability of OC in the stifle, hock and fetlock joints and of POF in the fetlock. Methods: Data on Swedish Warmblood (SWB) horses were obtained from a large equine hospital in south Sweden. Prevalences were based on radiographic examinations of 879 screened horses, mainly evaluated as part of a prepurchase examination and 3639 horses with a reported history of orthopaedic problems. For the heritability study the 2 data sources were pooled and 3199 examined horses with pedigree information were considered for the linear animal model analyses. Results: The overall prevalence of OC was 13% (stifle 9%, hock 6% and dorsal osseous fragments in fetlock [DOF] 10%) and POF 10%. The overall heritability of OC was 0.05 on the visible binomial scale. The corresponding heritabilities for OC in the stifle were 0.03, hock 0.08, DOF 0.10 and POF 0.13. These values correspond to heritabilities of 0.09–0.38 on the underlying quantitative scale. Conclusions and potential relevance: Obtained prevalences and heritabilities were in accordance with other studies, supporting the hypothesis that data regularly obtained from equine hospitals may be a valuable source in studies of inherited disorders such as OC and POF. There is a need for more standardised documentation of diagnoses and consistent recording of identity of examined horses using passports or breed databases. Compilation of results from major clinics is desired in order to cover most progenies of stallions used in a region or nation.