General and local [corrected] aetiologic factors in canine osteochondrosis

The epidemiology of osteochondrosis in an insured Swedish dog population

Osteochondrosis (OC) is a focal disturbance of endochondral ossification due to a failure of blood supply to the epiphyseal growth cartilage. In dogs, OC most commonly affects the shoulder joint, followed by the elbow, tarsal, and stifle joints. The condition is associated with clinical signs such as lameness and pain and the prognosis varies depending on the affected joint. Most epidemiologic studies of OC in dogs were performed over 20 years ago, and updated estimates of disease incidence are lacking. Therefore, the objectives of this study were to provide population-based estimates of the incidence rate, cause-specific mortality rate, and age at diagnosis of appendicular OC (AOC, including OC of the shoulder, elbow, stifle, and tarsal joints) and stifle and tarsal OC separately, using data from Agria Djurförsäkring in Sweden (2011-2016). Further, the study aimed to evaluate the risk of OC in subgroups divided by breed and sex and describe previous, concurrent, and subsequent diagnoses of the affected joint in dogs with stifle or tarsal joint OC. The study population included just over 600,000 dogs, of which 685 were affected by AOC. Stifle joint OC (n = 113) was more common than tarsal joint OC (n = 80). The incidence rate of AOC was 3.77 (95% confidence interval (CI): 3.49-4.07) cases per 10,000 dog-years at risk, while the incidence rate of stifle and joint tarsal OC was 0.64 (95% CI: 0.53-0.77) and 0.43 (95% CI: 0.34-0.54) cases per 10,000 dog-years at risk, respectively. All breeds at increased risk of AOC were large or giant, and male dogs had an increased risk of AOC compared to female dogs (RR 1.76, 95% CI: 1.50-2.07, p < 0.001). The median age at first diagnosis during the study period was 0.74 (0.32-11.5) years for AOC, 2.62 (0.45-8.82) years for stifle joint OC, and 0.73 (0.35-7.35) years for tarsal joint OC. Of the dogs with stifle or tarsal joint OC, 30.2% and 15.0% had a previous diagnosis of stifle/tarsal joint pain or other unspecific clinical signs, respectively, and 13.8% of the dogs with stifle joint OC suffered subsequent cruciate ligament rupture. Osteochondrosis was the most common reason for euthanasia in the affected dogs. In total, 77 dogs were euthanised due to AOC during the study period.

Long-term outcome of dogs treated by surgical debridement of proximal humeral osteochondrosis

OBJECTIVE

To evaluate long-term clinical outcomes of dogs surgically treated for proximal humeral osteochondrosis (OC).

STUDY DESIGN

Cross-sectional study.

SAMPLE POPULATION

Twenty dogs (n = 26 shoulders).

METHODS

Dogs treated with surgical debridement of proximal humeral OC lesions >12 months prior were enrolled. Orthopedic examination (including limb circumference and shoulder goniometry), kinetic gait analysis, shoulder radiographs, shoulder computed tomography (CT), and shoulder arthroscopy were performed. All owners completed a dog mobility questionnaire.

RESULTS

Brachial circumference (P = .003) and maximum shoulder extension (P = .013) were decreased and maximum shoulder flexion (P = .008) was increased (ie less flexion) in the OC limb versus the contralateral limb in unilaterally affected dogs. There were no differences in peak vertical force and vertical impulse between affected and unaffected limbs. Dogs demonstrated a 4.4% decrease in load distributed to the operated limb. Osteoarthritis was present in all shoulders treated for OC lesions. The degree of osteoarthritis in OC-affected shoulders was increased compared to the contralateral limb as evaluated on CT (P = .005) and radiography (P = .0001) in unilaterally affected cases. Moderate-to-severe synovitis was seen in all OC-affected joints. Arthroscopically, all lesions were noted to have patchy, incomplete cartilaginous infilling. Median of aggregate Liverpool Osteoarthritis in Dogs (LOAD) scores was 6.

CONCLUSION

All dogs exhibited ipsilateral muscle atrophy and progressive osteoarthritis, with most dogs exhibiting subtle lameness on the subjective gait examination. Despite this, owner-perceived mobility was satisfactory.

CLINICAL SIGNIFICANCE

Progression of joint disease over time should be expected; however, the abnormalities detected on examination appear to be of questionable clinical relevance.

Detection of fragment migration into the biceps tendon sheath originating from a humeral osteochondrosis lesion - A case report and review of the literature

The purpose of this report is to demonstrate that radiographic evaluation of the canine shoulder joint alone is not sensitive enough to detect migrated osteochondral fragments within the biceps tendon sheath, as a sequela to osteochondrosis dissecans of the caudal humeral head. A 6-months-old, male, 35 kg Hovawart was referred due to chronic intermittent lameness on the left forelimb. Survey radiographs revealed a semilunar radiolucency surrounded by a moderately sclerotic rim at the caudal aspect of the left humeral head, referred to as osteochondrosis dissecans. However, only computed tomography combined with ultrasonography could clearly confirm a dislodged osteochondral fragment within the left biceps tendon sheath and a consequent tenosynovitis. Arthroscopic treatment on the clinically affected left forelimb followed by an additional approach over the left biceps tendon sheath to remove the migrated fragment resulted in a complete remission of the lameness until the last follow-up one year after surgery. In our opinion, computed tomography should be applied in the medical work up of canine shoulder osteochondrosis (OC) as standard. Combined with ultrasonography, it can further aid in complete evaluation of the shoulder joint and reliable exclusion of displaced osteochondral fragments, which might also be missed during arthroscopy when located too far distally.

Use of Ultrasonography in Diagnosis of Medial Compartment Disease of the Elbow in Dogs

OBJECTIVE

 The objective of this prospective study was to evaluate the use of ultrasonography in the diagnosis of medial coronoid process disease in unclear cases.

STUDY DESIGN

 Fifteen elbows (on thirteen dogs) for which radiography and computed tomography did not lead to a clear diagnosis of medial coronoid process disease were included. On each elbow, ultrasonography was performed with a high frequency linear transducer (12-18Hz). Then, arthroscopic examination of the joint was performed by a surgeon who was unaware of ultrasonographic findings to confirm medial coronoid process disease.

RESULTS

 At least one ultrasonographic lesion was detected in 13 out of 15 elbows. The main reported ultrasonographic lesions were joint effusion (10/15 elbows) and an abnormal shape of the medial coronoid process (irregular, ill-defined or fragmented) (9/15).

CONCLUSION

 Ultrasonography can be a helpful additional diagnostic tool to confirm medial coronoid process disease of the elbow joint before performing arthroscopy in unclear cases. Further studies will be needed to evaluate the use of higher frequency transducers and determine if it could improve the diagnostic value of ultrasonography.

Angular limb deformities due to distal radial physeal osteochondrosis in farmed deer stags in New Zealand

CASE HISTORY

Three different farms reported cases of angular limb deformities in rising 2-year-old velvet, mostly red deer, stags with the earliest recorded cases occurring in 2010. Farm 1 reported a prevalence of 10-35%, farm 2, 5-11.5% and farm 3, 2-5%. Farms 1, 2 and 3 are located in South Canterbury, northern Southland and the Waikato, respectively.

CLINICAL FINDINGS

Affected animals developed angular limb deformities, with predominantly varus forelimb (bowed) deformities. On all farms serum calcium and phosphorus concentrations in affected animals were normal. Serum and liver copper concentrations were variable across the period of the study and between farms. Although some measurements were below the reference ranges, there was no evidence for a statistical association with the prevalence of abnormalities.

PATHOLOGICAL FINDINGS

The distal radius from 25 affected and four control red and red-wapiti cross deer from Farm 1 in 2010/2011, two affected red deer from Farm 2 in 2016, and one affected red deer from Farm 3 in 2021, were examined. The most consistent lesions were present in the distal radial physis, most commonly the lateral edge. There was mild-to-severe segmental thickening of the physis and, in some animals, physeal cartilage was duplicated with both sections of physis varying in thickness. Microscopically, in severely affected animals there was massive segmental thickening of physeal cartilage which often contained large cystic cavities. The cartilage matrix was eosinophilic and showed a loss of metachromatic staining with toluidine blue. In less severe cases, necrotic physeal vessels were present, consistent with vascular failure. In more chronic cases, there was duplication of the physis, the two layers being separated by a combination of normal trabecular bone and dense fibrous connective tissue.

DIAGNOSIS

Physeal osteochondrosis.

CLINICAL RELEVANCE

Osteochondrosis has a multifactorial aetiology and we propose that an increased requirement for nutrients for velvet production and increased weight bearing stress (behaviour and rapid weight gain) may lead to progression of osteochondrosis and angular limb deformities in these deer. The involvement of periods of copper deficiency is unclear at this time.

Tissue Engineering of Canine Cartilage from Surgically Debrided Osteochondritis Dissecans Fragments

This study in dogs explored the feasibility of using cartilage fragments removed and discarded during routine palliative surgery for osteochondritis dissecans (OCD) as a source of primary chondrocytes for scaffold-free cartilage tissue-engineering. Primary chondrocytes were obtained from three OCD donors and one age-matched healthy articular cartilage (HAC) donor. After monolayer expansion of primary cells, a three-dimensional spherical suspension culture was implemented. Following this stage, cells were seeded at a high density into custom-made agarose molds that allowed for size and shape-specific constructs to be generated via a method of cellular self-assembling in a scaffold-free environment. Fifty-eight neocartilage constructs were tissue-engineered using this methodology. Neocartilage constructs and native cartilage from shoulder joint were subjected to histological, mechanical, and biochemical testing. OCD and HAC chondrocytes-sourced constructs had uniformly flat morphology and histology consistent with cartilage tissue. Constructs sourced from OCD chondrocytes were 1.5-times (32%) stiffer in compression and 1.3 times (23%) stronger in tension than constructs sourced from HAC chondrocytes and only 8.7-times (81%) less stiff in tension than native tissue. Constructs from both cell sources consistently had lower collagen content than native tissue (22.9%/dry weight [DW] for OCD and 4.1%/DW for HAC vs. 51.1%/DW native tissue). To improve the collagen content and mechanical properties of neocartilage, biological and mechanical stimuli, and thyroid hormone (tri-iodothyronine) were applied to the chondrocytes during the self-assembling stage in two separate studies. A 2.6-fold (62%) increase in compressive stiffness was detected with supplementation of biological stimuli alone and 5-fold (81%) increase with combined biological and mechanical stimuli at 20% strain. Application of thyroid hormone improved collagen content (1.7-times, 33%), tensile strength (1.8-times, 43%), and stiffness (1.3-times, 21%) of constructs, relative to untreated controls. Collectively, these data suggest that OCD chondrocytes can serve as a reliable cell source for cartilage tissue-engineering and that canine chondrocytes respond favorably to biological and mechanical stimuli that have been shown effective in chondrocytes from other animal species, including humans.

Genetics of Equine Orthopedic Disease

Orthopedic diseases are a common cause for limited exercise capacity in the horse. They often underlie genetic risk factors, which can affect bone, articular cartilage, tendons, ligaments, and adnexal structures among others. The genetic effects can directly interfere with tissue development and skeletal growth or can trigger degenerative or inflammatory processes. Many of these diseases of the locomotor system like osteochondrosis are complex and can be affected by multifactorial influences. For this reason, it is important for those performing diagnostic procedures to have a comprehensive knowledge of orthopedic diseases, their prevalence within breeds, and genetic background.

Synthetic osteochondral resurfacing for treatment of large caudocentral osteochondritis dissecans lesions of the humeral head in 24 dogs

OBJECTIVE

To report the outcome of dogs with large, caudocentral, osteochondritis dissecans (OCD) lesions of the humeral head treated with synthetic osteochondral resurfacing (SOR) implants.

STUDY DESIGN

Retrospective case series.

ANIMALS

Twenty-four client-owned large breed or giant dogs.

METHODS

The medical records of all dogs treated with first generation (G1) and second generation (G2) SOR implants were reviewed. All dogs were assessed with clinical examination and imaging 12 weeks after surgery. Assessment of outcome was based on subjective assessment of lameness, scoring of postoperative radiographs, and the Liverpool Osteoarthritis in Dogs (LOAD) questionnaire.

RESULTS

Osteochondral resurfacing was performed with a G1 implant in 13 dogs (15 shoulders) and a G2 implant in 11 dogs (13 shoulders). Lameness resolved in all dogs treated with G1 implants and in 10 dogs treated with G2 implants by 12 weeks after surgery. One dog treated with a G2 implant was found to have an implant-associated infection, requiring implant removal. No recurrence of lameness was reported in 9 limbs treated with G1 implants and 10 limbs treated with G2 implants that were available for clinical review at a median time of 387 and 365 days, respectively, after surgery. Mean postoperative LOAD scores were 4.2 of 52 and 5.2 of 52 in dogs treated with a G1 or a G2 implant, respectively.

CONCLUSION

Synthetic resurfacing was technically feasible in all joints of this study and resulted in good clinical results.

CLINICAL SIGNIFICANCE

The use of SOR implants seems viable to treat large caudocentral OCD lesions of the humeral head in dogs and warrants prospective comparison with conventional arthroscopic treatment.

Species-Specific Features of Intraorganic Vascularization of the Tarsal Joint Capsule in Cattle and Canines

The comparative studies of the tarsal joint capsule of cattle (Bos taurus) and canines (Canis lupus) have clarified general patterns of the structural organization of a joint capsule and the species-specific features of its angioarchitectonics. The differences in the formation of the fibroelastic layer and the location of vascular fields in the cases of animals with different stances were established. The zones of intensive intraorganic vascularization of the joint capsule were revealed; that being—the plantar and dorsal surface in the case of cattle, the lateral and medial surfaces—in case of the canine.

Erosion of the medial compartment of the canine elbow: occurrence, diagnosis and currently available treatment options

Erosion of the medial compartment of the elbow joint refers to full thickness cartilage loss with exposure of the subchondral bone (modified Outerbridge grades 4–5) of the medial part of the humeral condyle (MHC) and the corresponding ulnar contact area. This finding may appear in the absence of an osteochondral fragment or a cartilage flap, or in combination with fragmentation of the medial coronoid process (MCP) or osteochondritis dissecans (OCD) of the MHC. With regard to the prognosis, it is important to diagnose these severe erosions. Imaging of cartilage lesions by means of radiography, ultrasonography, computed tomography or magnetic resonance imaging is challenging in dogs. In contrast, direct arthroscopic inspection provides detailed information about the cartilage.

The treatment of these severe erosions is difficult because of the limited regenerative capacity of cartilage and presumed mechanical or physical triggering factors. Several conservative and surgical treatment methods have been proposed to treat elbows with severe cartilage defects. However, due to irreversible loss of cartilage, the prognosis in these cases remains guarded.

Post-weaning high-fat diet results in growth cartilage lesions in young male rats

To determine if a high-fat diet (HF) from weaning would result in a pro-inflammatory state and affect joint cartilage, we fed male rats either HF or Chow diet post-weaning, and voluntary wheel exercise (EX) or cage only activity (SED) after 9 weeks of age. At 17 weeks body composition, plasma biomarkers and histomorphology scores of femoro-tibial cartilages of HF-SED, HF-EX, Chow-SED and Chow-EX groups were compared. Food intake and activity were not significantly different between groups. HF diet resulted in significantly higher weight gain, %fat, fat:lean ratio, and plasma leptin, insulin and TNFα concentrations, with significant interactions between diet and exercise. No abnormal features were detected in the hyaline articular cartilage or in the metaphyseal growth plate in all four groups. However, collagen type X- positive regions of retained epiphyseal growth cartilage (EGC) was present in all HF-fed animals and significantly greater than that observed in Chow-fed sedentary rats. Most lesions were located in the lateral posterior aspect of the tibia and/or femur. The severity of lesions was greater in HF-fed animals. Although exercise had a significantly greater effect in reducing adiposity and associated systemic inflammation in HF-fed rats, it had no effect on lesion incidence or severity. Lesion incidence was also significantly associated with indices of obesity and plasma markers of chronic inflammation. Clinically, EGC lesions induced by HF feeding in rats from very early in life, and possibly by insufficient activity, is typical of osteochondrosis in animals. Such lesions may be the precursor of juvenile osteochondritis dissecans requiring surgery in children/adolescents, conservative management of which could benefit from improved understanding of early changes in cellular and gene expression.

Response of cattle with clinical osteochondrosis to mineral supplementation

Since 1982, farmers in the North West province and other parts of South Africa have noticed an increase in the incidence of lameness in cattle. Macro- and microscopical lesions of joints resembled osteochondrosis. Pre-trial data indicated that cattle with osteochondrotic lesions recovered almost completely when fed a supplement containing bio-available micro- and macrominerals of high quality. In the present trial, 43 clinically affected cattle of varying ages (1-5 years) and sexes were randomly divided into three groups. Each group was fed the same commercial supplement base with differing micro- and macromineral concentrations to determine the effect of mineral concentrations on the recovery from osteochondrosis. Both supplements 1 and 2 contained 25% of the recommended National Research Council (NRC) mineral values. Additional phosphate was added to supplement 2. Supplement 3, containing 80% of the NRC mineral values, was used as the control. Results from all three groups indicated no recovery from osteochondrosis. Urine pH of a small sample of the test cattle showed aciduria (pH &lt; 6). Supplement analysis revealed addition of ammonium sulphate that contributed sulphate and nitrogen to the supplement. Supplementary dietary cation anion difference (DCAD) values were negative at -411 mEq/kg, -466 mEq/kg and -467 mEq/kg for supplements 1, 2 and 3, respectively, whereas the pre-trial supplement was calculated at +19.87 mEq/kg. It was hypothesised that feeding a low (negative) DCAD diet will predispose growing cattle to the development of osteochondrosis or exacerbate subclinical or clinical osteochondrosis in cattle.

Preliminary report on osteochondrosis in cattle in the north-western parts of South Africa

The north-western part of South Africa, in particular, is well known for mineral imbalances. Aphosphorosis, resulting in rickets and osteomalacia, received a lot of attention at the turn of the nineteenth century (1882–1912). This was followed in 1997 by research on Vryburg hepatosis, another area-specific mineral imbalance–related disease in young calves reared on manganese-rich soil derived from the weathering of dolomitic (carbonate) rock formations. In 1982, a totally new syndrome (osteochondrosis) manifested in, amongst others, areas in South Africa where aphosphorosis was rife. Osteochondrosis was also identified in the south-western parts of Namibia as well as southern Botswana and other areas in South Africa. Osteochondrosis has a multifactorial aetiology and this study focused on the role of minerals, particularly phosphorus, in the development of the disease. A significant improvement in the clinical signs in experimental animals and a reduction of osteochondrosis occurred on farms where animals received bioavailable trace minerals and phosphorus as part of a balanced lick. An increase in the occurrence of the disease on farms during severe drought conditions in 2012–2013 prompted researchers to investigate the possible role of chronic metabolic acidosis in the pathogenesis of the disease.

Etiology and Pathogenesis of Osteochondrosis

Osteochondrosis is a common and clinically important joint disorder that occurs in human beings and in multiple animal species, most commonly pigs, horses, and dogs. This disorder is defined as a focal disturbance of enchondral ossification and is regarded as having a multifactorial etiology, with no single factor accounting for all aspects of the disease. The most commonly cited etiologic factors are heredity, rapid growth, anatomic conformation, trauma, and dietary imbalances; however, only heredity and anatomic conformation are well supported by the scientific literature. The way in which the disease is initiated has been debated. Although formation of a fragile cartilage, failure of chondrocyte differentiation, subchondral bone necrosis, and failure of blood supply to the growth cartilage all have been proposed as the initial step in the pathogenesis, the recent literature strongly supports failure of blood supply to growth cartilage as being the most likely. The term osteochondrosis has been used to describe a wide range of different lesions among different species. We suggest a refinement of this terminology to include the modifiers latens (lesion confined to epiphyseal cartilage), manifesta (lesion accompanied by delay in endochondral ossification), and dissecans (cleft formation through articular cartilage). The purpose of this review is to provide an overview of the disease, focusing on the most commonly cited theories, recent research findings, and our own views regarding the etiology and pathogenesis of osteochondrosis, in order to provide a better understanding of this apparently complex disease.

Assessment of articular cartilage and subchondral bone using EPIC-microCT in Labrador retrievers with incipient medial coronoid disease

The aetiopathogenesis of medial coronoid disease (MCD) remains obscure, despite its high prevalence. The role of changes to subchondral bone or articular cartilage is much debated. Although there is evidence of micro-damage to subchondral bone, it is not known whether this is a cause or a consequence of MCD, nor is it known whether articular cartilage is modified in the early stages of the disease. The aim of the present study was to use equilibrium partitioning of an ionic contrast agent with micro-computed tomography (microCT) to investigate changes to both the articular cartilage and the subchondral bone of the medial coronoid processes (MCP) of growing Labrador retrievers at an early stage of the disease and at different bodyweights. Of 14 purpose-bred Labrador retrievers (15-27 weeks), six were diagnosed with bilateral MCD and one was diagnosed with unilateral MCD on the basis of microCT studies. The mean X-ray attenuation of articular cartilage was significantly higher in dogs with MCD than in dogs without MCD (P<0.01). In all dogs, the mean X-ray attenuation of articular cartilage was significantly higher at the lateral (P<0.001) than at the proximal aspect of the MCP, indicating decreased glycosaminoglycan content. Changes in parameters of subchondral bone micro-architecture, namely the ratio of bone volume to tissue volume (BV/TV), bone surface density (BS/TV), bone surface to volume ratio (BS/BV), trabecular thickness (Tb.Th; mm), size of marrow cavities described by trabecular spacing (Tb.Sp; mm), and structural model index (SMI), differed significantly by litter (P<0.05) due to the difference in age and weight, but not by the presence/absence of MCD (P>0.05), indicating that subchondral bone density is not affected in early MCD. This study demonstrated that cartilage matrix and not subchondral bone density is affected in the early stages of MCD.

Osteochondritis dissecans of the humeral head in two small-breed dogs

Shoulder pathology consistent with osteochondritis dissecans of the humeral head was diagnosed in two small-breed dogs. In both cases, the diagnosis was made tentatively on the basis of radiography and confirmed by arthroscopy of the affected shoulder joint. Both dogs were successfully treated by surgical removal of a flap of cartilage from the affected area. Clinical and radiographic follow-up was available in both cases. The excised cartilage flaps were examined histopathologically and showed the same characteristics as cartilage flaps from dogs of large breeds prone to developing osteochondritis dissecans of the shoulder.

Joint disorder; a contributory cause to reproductive failure in beef bulls?

The lame sire, unsound for breeding, can cause substantial economic loss due to reduced pregnancies in the beef-producing herd. To test the hypothesis that joint disorder is a possible cause of infertility in beef sires, right and left hind limb bones from 34 beef sires were examined postmortem to identify lesions in the femorotibial, femoropatellar (stifle), tarsocrural, talocalcaneus, and proximal intertarsal (tarsal) joints. The bulls were slaughtered during or after the breeding season due to poor fertility results. Aliquots of the cauda epididymal contents taken postmortem from 26 bulls were used for sperm morphology evaluation. As a control, hind limbs (but no semen samples) from 11 beef bulls with good fertility results were included. Almost all infertile bulls (30/34) had lesions in at least one joint. Twenty-eight bulls (28/30, 93%) had lesions in the stifle joint, and 24 (24/28, 86%) of these were bilateral. Fourteen bulls (14/30, 47%) had lesions in the tarsal joint, and 10 (10/14, 71%) of these were bilateral. Four bulls (4/34, 12%) had no lesions, three bulls (3/34, 9%) had mild osteoarthritis (OA), 5 (5/34, 15%) moderate OA, 17 (17/34, 50%) severe OA and 5 (5/34, 15%) deformed OA. Almost all OA lesions (97%) were characterized as lesions secondary to osteochondrosis dissecans. All the bulls with satisfactory sperm morphology (n = 12/34) had joint lesions, with mostly severe or deformed bilateral lesions (83%). Consequently, the most likely cause of infertility in these 12 bulls was joint disease. Almost all control bulls (10/11) had OA lesions, but most of them were graded as mild (55%) or moderate (36%). None of the control bulls had severe lesions or deformed OA. We suggest that joint lesions should be taken into consideration as a contributory cause of reproductive failure in beef sires without symptoms of lameness.

Histomorphometry of Fragmented Medial Coronoid Process in Dogs: A Comparison of Affected and Normal Coronoid Processes

OBJECTIVE

To determine if fatigue microdamage is associated with fragmented medial coronoid process (FMCP).

STUDY DESIGN

Prospective study.

ANIMALS

Thirty-eight dogs were admitted for subtotal coronoid ostectomy as treatment for FMCP. Surgical specimens of medial coronoid process (MCP) were retrieved from treated dogs. Normal MCP were collected from 5 age- and breed-matched dogs and 2 age-matched research beagles that were euthanatized for reasons other than elbow disease.

METHODS

MCP specimens from affected elbows were classified into 4 groups based on disease severity. Specimens were bulk-stained for microdamage using 1% basic fuchsin, embedded in polymethylmethacrylate and sectioned at 130 microm. Specimens were evaluated using epifluorescent microscopy (425-440 excitation, 475 nm barrier filter) for diffuse damage (D.DX), osteocyte loss, and porosity. Cartilage thickness was evaluated using bright field microscopy. Qualitative observations were also made.

RESULTS

MCP specimens from affected elbows had increased D.Dx, increased osteocyte loss, and greater porosity than normal groups. Specimens classified as severe FMCP (Classes 3, 4) had the most fatigue microdamage. Some Class 1 specimens, defined as having no visible fissuring of the articular cartilage (AC), had large microcracks in trabecular bone.

CONCLUSIONS

Accumulation of subchondral fatigue microdamage, is associated with MCP fragmentation. Fissuring occurs in the subchondral bone before gross fibrillation of articular cartilage develops.

CLINICAL RELEVANCE

Accumulation of fatigue microdamage in the MCP is important in the pathogenesis of FMCP. The underlying cause of this microdamage accumulation must be identified before treatment plans that will prevent further osteoarthritis of the elbow joint can be designed.

Canine elbow dysplasia and primary lesions in German shepherd dogs in France

Five hundred and twenty German shepherd dogs were screened for elbow dysplasia. The following primary lesions were analysed: joint incongruity (JI), fragmented medial coronoid process (FCP), osteochondrosis or osteochondritis of the medial humeral condyle and ununited anconeal process (UAP). Three radiographic views were used for each joint to achieve a definitive diagnosis. The prevalence of elbow dysplasia was 19.4 per cent. The most frequent lesion was JI (16.3 per cent), followed by FCP (11.3 per cent). UAP was diagnosed rarely (1.1 per cent). Combinations of lesions were very frequent (42.2 per cent of the dysplastic elbows). Although these results may be biased due to prescreening of dogs with UAP, it should be highlighted that JI and FCP occur frequently in German shepherd dogs and are probably the most common primary lesions of elbow dysplasia, although they have been under-reported until now.

New findings on animal diseases published since 2003. 1. Dogs

This is the first article of a series of papers reviewing "new findings" on animal diseases. The articles are arranged in order of animal species. This article reviews seven publications on new findings on or directly related to dog diseases. The following seven cases are discussed: Canine sarcocystosis in Central America. Copper accumulation in a Skye terrier: Antemortem diagnosis and cytoprotective bile acid therapy. Keratinocyte culture and use of a cultured epidermal autograft. Line 1 insertion mutation in Factor IX of dogs with hemophilia B. Not previously described localization of the lesions in stifle osteochondritis dissecans. Panniculitis associated with pancreatitis: Antemortem diagnosis. Primary polydipsia associated with (and induced by?) gastrointestinal disease. After a short introduction, the bibliographical data, the abstract of the author(s) and some additional information derived from the article are given.

Computed tomographic osteoabsorptiometry of the elbow joint in clinically normal dogs

OBJECTIVE

To evaluate subchondral bone density patterns in elbow joints of clinically normal dogs by use of computed tomographic (CT) osteoabsorptiometry.

SAMPLE POPULATION

20 cadaver forelimbs from 10 clinically normal dogs.

PROCEDURE

Each elbow joint was imaged in parasagittal and transverse planes of 1.5-mm thickness. Slice data were converted to dipotassium phosphate equivalent density (PPED) values. Sagittal, parasagittal, and transverse medial coronoid process topographic maps were constructed. Defined zones were created for each of the 3 CT planes, and confluence and peak PPED values were determined.

RESULTS

The lowest PPED value was 340 mg/ml (articular and subchondral confluence), and the highest was 1780 mg/ml (peak subchondral density). Detectable effects of joint laterality were not found in the confluence or peak PPED measurements or in the peak-to-confluence PPED ratio for all 3 CT planes. Significant differences were found among zones in all 3 planes for confluence and peak PPED measurements and between sagittal and transverse planes for peak-to-confluence PPED ratios. Subjectively, the pattern of density distribution among dogs was fairly consistent for the sagittal and parasagittal slices. Three specific patterns of density distribution were apparent on the transverse topographic maps of the medial coronoid process that corresponded to conformational differences.

CONCLUSIONS AND CLINICAL RELEVANCE

The use of CT osteoabsorptiometry provides a repeatable technique that can be used to noninvasively examine bone density and the effects of stress acting on joints in vivo. Variability in density values for any of the CT planes was not identified among clinically normal dogs.

Use of the distomedial-proximolateral oblique radiographic view of the elbow joint for examination of the medial coronoid process in dogs

OBJECTIVE

To describe and evaluate a new radiographic view of the elbow joint in dogs that would potentially enhance observation of the medial coronoid process (MCP).

SAMPLE POPULATION

20 cadaver limbs from 10 dogs and clinical examination of 100 elbow joints of 53 dogs.

PROCEDURE

Twenty elbow joints from 10 cadavers were imaged by use of mediolateral, flexed mediolateral, craniocaudal, craniolateral-caudomedial oblique (Cr15L-CdMO), and distomedial-proximolateral oblique (Di35M-PrLO) radiographic views before and after placement of 3 lead pellets placed on the cranial, medial, and craniodistal aspect of the MCP. Three examiners independently reviewed these radiographs. One hundred elbow joints of 53 dogs with forelimb lameness and signs of pain elicited on palpation of the elbow joint were examined. These joints were radiographed and treated by use of arthroscopy. Three examiners independently graded the radiographs.

RESULTS

The MCP was identified on all Di35M-PrLO views made during the anatomic study. The Di35M-PrLO view had the largest area under the receiving operating characteristic (ROC) curve for detection of abnormalities of the MCP. Fractured and nonfractured MCP could only be significantly differentiated on Di35M-PrLO and mediolateral views. The Di35M-PrLO view had a higher agreement between examiners than other radiographic views for detection of fractures of the MCP.

CONCLUSION AND CLINICAL RELEVANCE

The Di35M-PrLO view enhances the identification of anomalies and fragmentation of the MCP in dogs, compared with other radiographic views. The Di35M-PrLO view may be of benefit for early screening of dogs potentially affected with elbow dysplasia.

Fragmented coronoid process and incomplete ossification of the humeral condyle in a rottweiler

OBJECTIVE

To describe incomplete ossification of the humeral condyle and fragmentation of the medial coronoid process in a Rottweiler.

STUDY DESIGN

Clinical report.

ANIMAL POPULATION

A 4-year-old sexually intact male Rottweiler.

METHODS

Physical examination, radiography, and computed tomography of both elbow joints were performed initially. Drill holes were made across the humeral condyle to promote ossification. Radiography and computed tomography were repeated 14 weeks later. Radiography was repeated 15 months later. A mild intermittent lameness remained.

RESULTS

Preoperatively a radiolucent line was present across the right humeral condyle. This radiolucent line remained unchanged 14 weeks after drill holes were made across the condyle.

CONCLUSIONS

Incomplete ossification of the humeral condyle is present in Rottweilers.

CLINICAL RELEVANCE

Incomplete ossification of the humeral condyle is present in Rottweilers and may coexist with fragmentation of the medial coronoid process in that breed. The radiographic diagnosis may be difficult because precise positioning is required to see the area of incomplete ossification. Computed tomography may be required to confirm the presence of incomplete ossification of the humeral condyle. Drilling holes across the humeral condyle does not appear to lead to union of the area of incomplete ossification.

The pathophysiology of osteochondrosis

Osteochondrosis is a disorder of epiphyseal cartilage about which there is considerable confusion in the literature. We believe that this is due to the fact that osteochondrosis has been studied in the chronic stage when the lesions are morphologically complicated and the initial causative insult is impossible to determine. The etiology of osteochondrosis appears to be multifactorial, with trauma, hereditary factors and rapid growth, nutritional factors, and ischemia all having a role in its pathogenesis. Although predilection sites are variable among species, the morphology of the early lesions is strikingly similar, strongly suggesting that the pathogenesis of osteochondrosis is the same, regardless of the species affected. Based on recent studies in pigs and horses, and supported by observations in dogs and cattle, we believe that local ischemia secondary to defects in cartilage canal blood supply is a key factor in the initiation of lesions of osteochondrosis and explains many of the features of this disease. Local ischemia to the epiphyseal cartilage of the articular-epiphyseal cartilage complex leads to the formation of highly vulnerable zones of necrotic epiphyseal cartilage which later cause a delay in endochondral ossification, with extension of necrotic cartilage into the subchondral bone. Trauma, whether major or minor, to the overlying articular cartilage leads to cartilage cleft formation, clinical signs of pain and lameness, and other chronic sequelae. Studies aimed at further elucidating the pathogenesis of osteochondrosis should attempt to determine the cause of the vascular defect and whether or not it may be modified by experimental manipulations.

Osteochondrosis of the femur

Osteochondrosis can occur in the stifle joint(s) of young, rapidly growing large breeds of dogs. Although not as common as osteochondrosis of the shoulder, elbow, and hock joints, the osteochondral defect in the femoral condyle(s) and stifle joint fragment can cause a clinically apparent lameness. Radiography is beneficial in identifying the lesion(s), and surgical therapy is useful in restoring limb function.