Effects of osteochondral fragmentation and intra-articular triamcinolone acetonide treatment on subchondral bone in the equine carpus

A Double-Blinded Positive Control Study Comparing the Relative Efficacy of 2.5% Polyacrylamide Hydrogel (PAAG) Against Triamcinolone Acetonide (TA) And Sodium Hyaluronate (HA) in the Management of Middle Carpal Joint Lameness in Racing Thoroughbreds

The purpose of this prospective double-blinded positive control study was to compare the efficacy of 2.5% polyacrylamide hydrogel (2.5% PAAG) in the management of middle carpal joint lameness in Thoroughbreds against treatments of triamcinolone acetonide (TA) or sodium hyaluronate (HA). A total of 31 flat-racing Thoroughbreds with lameness (grade 1-3/5) localized to the carpus by intra-articular analgesia were selected. Following a radiological assessment of the carpi confirming the absence of fragment/fracture, the horses were randomly assigned for intra-articular treatment with either 2 ml of 2.5% PAAG, 12 mg TA or 20 mg HA (followed by two further intravenous treatments of 40 mg, at weekly intervals in the HA group only), by a treating veterinarian. All horses were rested for 48 hours post-treatment and then re-entered an unaltered training regimen. Subsequent examinations at 2, 4, and 6 weeks were performed by a blinded examining veterinarian for all groups, while horses treated with 2.5% PAAG were monitored for 12 weeks for recurrence of lameness. Significantly more joints treated with 2.5% PAAG were lame free (83%) at 6 weeks compared to TA (27%; P = .007) and to HA (40%; P = .04). There was no significant difference between TA and HA groups at any time. All the joints treated within 2.5% PAAG that were lame free at 6 weeks (10/12) were still lame-free at 12 weeks. In conclusion, treatment with 2.5% PAAG led to statistically superior results compared to TA and HA in the management of selected middle carpal joint lameness in flat-racing Thoroughbreds, with therapeutic effects persisting up to 12 weeks.

In vitro Effects of Methylprednisolone Acetate on Equine Deep Digital Flexor Tendon-Derived Cells

Primary deep digital flexor tendon (DDFT) pathologies and those accompanying degenerative changes of navicular bone fibrocartilage are major causes of lameness associated with navicular disease. Intrasynovial corticosteroids are mainstay in the treatment due to the anti-inflammatory effects, but their effect on DDFT cell biosynthesis are unknown. The objective of this in-vitro study was to investigate the effects of methylprednisolone acetate (MPA) on cells isolated from the dorsal fibrocartilaginous region of forelimb DDFTs (DDFT-derived cells) of 5 horses (aged 11–17 years). Non-adherent aggregate cultures were established from third passage cells over a 72 to 96-h duration prior to treating with medium containing 0 (control), 0.05 and 0.5 mg/mL MPA for 24 h. Tendon and cartilage extracellular matrix (ECM) related gene expression, cell aggregate and culture medium GAG contents, culture medium collagen and MMP-3 and−13 concentrations were measured. After 24 h of treatment, only the higher MPA concentration (0.5 mg/mL) significantly down-regulated tendon ECM related genes; whereas, both MPA doses significantly down-regulated cartilage ECM related genes. MPA treatment did not affect the total GAG content of DDFT-derived cells or total GAG, soluble collagen and MMP-3 and−13 contents in culture medium compared to untreated controls. Future studies to determine the response of DDFT-derived cells with longer exposure times to corticosteroids and in the presence of inflammatory cytokines are necessary. These results are a first step in assessing the effects of intrasynovial medications on equine DDFT, for which currently no information exists.

Influence of Exercise and Intra-articular Site on Canals in Articular Calcified Cartilage of Equine Third Carpal Bones

The third carpal bone (C3) responds to exercise by adaptive modeling of bone and articular calcified cartilage along the dorsal load path. Canals penetrating articular calcified cartilage, thought to contain vascular tissue, are reported in numerous species. Their significance remains unclear. Our objective was to determine if the number of canals was significantly different in strenuously exercised and control young horses and in a site of intermittent high loading compared to sites sustaining lower habitual loads. Volumetric bone mineral density in the radial facet of C3 of strenuously exercised and gently exercised (control) 19-month-old thoroughbred horses ( n = 6/group) was determined by peripheral quantitative computed tomography. The hyaline cartilage was corroded to expose the surface of articular calcified cartilage. The number of canals penetrating the articular calcified cartilage surface in en face scanning electron microscopy images was compared in 4 regions. Volumetric bone mineral density of C3 was significantly greater ( P = .004) in strenuously exercised horses. There were 2 morphologically distinct groups of canals and significantly fewer ( P = .006) large canals in the dorsal than in the palmar aspect of C3 in control but not in exercised horses. Roughly circular depressions in the articular calcified cartilage surface around apparently forming canals were visible in some samples and have not been previously described in the literature. The canals may be evidence of chondroclastic activity reaching the interface of hyaline and calcified cartilage. Further work is needed to elucidate the relationships between presence of canals and the responses to exercise and to joint disease.

Musculoskeletal Pathology

The current understanding of pathology as it relates to common diseases of the equine musculoskeletal system is reviewed. Conditions are organized under the fundamental categories of developmental, exercise-induced, infectious, and miscellaneous pathology. The overview of developmental pathology incorporates the new classification system of juvenile osteochondral conditions. Discussion of exercise-induced pathology emphasizes increased understanding of the contribution of cumulative microdamage caused by repetitive cyclic loading. Miscellaneous musculoskeletal pathology focuses on laminitis, which current knowledge indicates should be regarded as a clinical syndrome with a variety of possible distinct mechanisms of structural failure that are outlined in this overview.

Use of firocoxib for the treatment of equine osteoarthritis

This review presents the pathogenesis and medical treatment of equine osteoarthritis (OA), focusing on firocoxib. Inhibition of prostaglandin E₂ remains a fundamental treatment for decreasing clinical symptoms (ie, pain and lameness) associated with OA in horses. Nonsteroidal anti-inflammatory drugs (NSAIDs), which inhibit the production of prostaglandin E₂ from the arachidonic acid pathway, continue to be a mainstay for the clinical treatment of OA. Firocoxib is a cyclooxygenase (COX)-2-preferential NSAID that has been shown to be safe and to have a 70% oral bioavailability in the horse. Three clinical reports identified symptom-modifying effects (reduction in pain and/or lameness) in horses with OA administered the once-daily recommended dose (0.1 mg/kg) of oral firocoxib following 7 days of administration. Other reports have suggested that a one-time loading dose (0.3 mg/kg) of firocoxib provides an earlier (1–3 days) onset of action compared to the recommended dose. It is noteworthy that OA disease-modifying effects have been reported in horses for other COX-2-preferential NSAIDs (meloxicam and carprofen), but have not been attributed to firocoxib due to a lack of investigation to date.

Evaluation of a single intra-articular injection of autologous protein solution for treatment of osteoarthritis in horses

OBJECTIVE

To evaluate intra-articular autologous protein solution (APS) for the treatment of osteoarthritis in horses. Animals-40 client-owned horses with naturally occuring osteoarthritis.

PROCEDURES

APS was generated from a dual-device system that concentrated plasma and WBC proteins and enriched platelet growth factors. Horses were randomly assigned to receive an intra-articular injection of 5 mL of saline (0.9% NaCl) solution (n = 20) or APS (20), exercised on a treadmill, and evaluated on the basis of lameness grades, kinetic gait analysis, joint circumference, and range of motion for 14 days. Horses that received saline solution were administered APS at termination of the study, and clients scored horses for lameness and discomfort before, 12 weeks after, and 52 weeks after the APS injection.

RESULTS

The APS group had significant improvements in lameness grade, asymmetry indices of vertical peak force, and range of joint motion by 14 days, compared with baseline or control group values. No adverse effects associated with APS treatment were evident. Clients assessed lameness and comfort as improved at 12 and 52 weeks. The APS had greater likelihood (OR, 4.3 to 30.0) of a therapeutic response in horses with a lameness score < 4, < 10% vertical force asymmetry, or absence of marked osteophyte formation, subchondral sclerosis, or joint space narrowing. Concentration of interleukin-1 receptor antagonist in APS was 5.8 times that in blood.

CONCLUSIONS AND CLINICAL RELEVANCE

Intra-articular administration of APS can be considered an effective treatment option for equine osteoarthritis, with the potential for disease-modifying effects.

Histomorphometric evaluation of the effect of early exercise on subchondral vascularity in the third carpal bone of horses

OBJECTIVE

To investigate histomorphometric changes in the cartilage and subchondral bone of the third carpal bone associated with conditioning exercise in young Thoroughbreds.

ANIMALS

Nine 18-month-old Thoroughbreds. Procedures-Both third carpal bones of 9 horses (4 exercised spontaneously at pasture only and 5 given additional conditioning exercise beginning at a mean age of 3 weeks) were evaluated. Histomorphometric variables (hyaline and calcified cartilage thickness and collagen orientation; vascular channel area, number, and orientation; and osteochondral junction rugosity) of the third carpal bone, sampled at 4 dorsopalmar sites in the radial facet, were compared between the exercised and nonexercised groups.

RESULTS

The vascular channel area measured at the 4 dorsopalmar sites was larger in the exercised group than in the control group, but none of the variables were significantly different between groups. Both groups had significant site-specific variations in all measured variables. Most importantly, the vascular channel area was highest in the most dorsal aspect.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that the mild exercise imposed in both groups during the developmental period appeared to be associated with an increase in the vascular channel area beneath the calcified cartilage layer in the third carpal bone. This increased vascular channel area could also be associated with high stress in the dorsal aspect of the radial facet, a region that is known to be vulnerable to osteochondral fragmentation.

A review of translational animal models for knee osteoarthritis

Knee osteoarthritis remains a tremendous public health concern, both in terms of health-related quality of life and financial burden of disease. Translational research is a critical step towards understanding and mitigating the long-term effects of this disease process. Animal models provide practical and clinically relevant ways to study both the natural history and response to treatment of knee osteoarthritis. Many factors including size, cost, and method of inducing osteoarthritis are important considerations for choosing an appropriate animal model. Smaller animals are useful because of their ease of use and cost, while larger animals are advantageous because of their anatomical similarity to humans. This evidence-based review will compare and contrast several different animal models for knee osteoarthritis. Our goal is to inform the clinician about current research models, in order to facilitate the transfer of knowledge from the "bench" to the "bedside."

The horse as a model of naturally occurring osteoarthritis

Osteoarthritis (OA) is an important cause of pain, disability and economic loss in humans, and is similarly important in the horse. Recent knowledge on post-traumatic OA has suggested opportunities for early intervention, but it is difficult to identify the appropriate time of these interventions. The horse provides two useful mechanisms to answer these questions: 1) extensive experience with clinical OA in horses; and 2) use of a consistently predictable model of OA that can help study early pathobiological events, define targets for therapeutic intervention and then test these putative therapies. This paper summarises the syndromes of clinical OA in horses including pathogenesis, diagnosis and treatment, and details controlled studies of various treatment options using an equine model of clinical OA.

Effects of extracorporeal shock wave therapy and polysulfated glycosaminoglycan treatment on subchondral bone, serum biomarkers, and synovial fluid biomarkers in horses with induced osteoarthritis

OBJECTIVE

To evaluate effects of extracorporeal shock wave therapy (ESWT) and polysulfated glycosaminoglycan treatment (PSGAGT) on subchondral bone (SCB), serum biomarkers, and synovial fluid biomarkers in horses with induced osteoarthritis.

ANIMALS

24 healthy 2- to 3-year-old horses.

PROCEDURES

An osteochondral fragment was created on the distal aspect of the radial carpal bone in 1 middle carpal joint of each horse. Horses were randomly allocated to receive local application of ESWT (days 14 and 28; n = 8), PSGAGT (IM, q 4 d for 28 days; 8), or a sham ESWT probe (placebo; days 14 and 28; 8). Serum biomarkers were measured every 7 days, and synovial fluid biomarkers were measured every 14 days. Bone density was measured by use of computed tomography on days 0 and 70, and microdamage and bone formation variables were compared among groups at the end of the study (day 70).

RESULTS

There was no significant effect of ESWT or PSGAGT on any bone variable. Serum osteocalcin concentration was significantly greater in horses that received ESWT, compared with placebo-treated horses, and serum concentration of the C-terminal telopeptide of type I collagen was significantly higher in horses that received ESWT, compared with placebo- and PSGAG-treated horses. Concentrations of the synovial fluid epitope CS846 were significantly higher in joints with osteoarthritis treated with ESWT CONCLUSIONS AND CLINICAL RELEVANCE: Treatment of osteoarthritis with ESWT had no effect on SCB but did induce increases in serum biomarkers indicative of bone remodeling. Treatment of osteoarthritis with PSGAG had no effect on SCB or biomarkers.

Intra-articular drug delivery: the challenge to extend drug residence time within the joint

The rationale behind developing sustained release microsphere formulations of non-steroidal anti-inflammatory drugs (NSAIDs) administered via the intra-articular (IA) route is to minimise the systemic bioavailability and attendant side-effects associated with oral drug administration. Overall dose is reduced whilst therapeutic benefit within the joint is maintained. The potential benefits of IA therapy for osteoarthritis (OA) are not achieved using currently available medications and delivery vehicles due to the rapid clearance of therapeutic substances from the synovial space. There is a need for sustained release delivery systems if the potential of IA drug administration is to be realised. Rationally designed microspheres taken up by synovial macrophages offer a strategy to sustain drug delivery within the joint, and to deliver NSAIDs directly to pivotal inflammatory cells. The efficacy of microsphere candidates may be evaluated in large animal models of OA. The principles of IA microsphere drug delivery may also be applicable to other classes of drugs.

The OARSI histopathology initiative - recommendations for histological assessments of osteoarthritis in the horse

OBJECTIVE

Equine models of osteoarthritis (OA) have been used to investigate pathogenic pathways of OA and evaluate therapeutic candidates for naturally occurring equine OA which is a significant clinical disease in the horse. This review focuses on the macroscopic and microscopic criteria for assessing naturally occurring OA in the equine metacarpophalangeal joint as well as the osteochondral fragment-exercise model of OA in the equine middle carpal joint.

METHODS

A review was conducted of all published OA studies using horses and the most common macroscopic and microscopic scoring systems were summarized. Recommendations regarding methods of OA assessment in the horse have been made based on published studies.

RESULTS

A modified Mankin scoring system is recommended for semi-quantitative histological assessment of OA in horses due to its already widespread use and similarity to other scoring systems. Recommendations are also provided for histological scoring of synovitis and macroscopic lesions of OA as well as changes in the calcified cartilage and subchondral bone of naturally occurring OA.

CONCLUSIONS

The proposed system for assessment of equine articular tissues provides a useful method to quantify OA change. It is believed that addition of quantitative tracing onto plastic and macroscopic measurement as recently described would be an improvement for overall assessment of articular cartilage change.

Evaluation of diffusion of triamcinolone acetonide from the distal interphalangeal joint into the navicular bursa in horses

OBJECTIVE

To determine whether triamcinolone acetonide diffuses from the distal interphalangeal joint (DIPJ) to the navicular bursa, diffusion is direct or systemic, and addition of sodium hyaluronan has an effect on diffusion in horses.

ANIMALS

11 adult horses without forelimb lameness.

PROCEDURES

1 randomly chosen forelimb DIPJ of each horse received an injection of 10 mg of triamcinolone acetonide plus 20 mg of sodium hyaluronan (group 1), and the contralateral forelimb DIPJ received an injection of 10 mg of triamcinolone acetonide plus 2 mL of lactated Ringer's solution (group 2). Synovial fluid samples were taken from both forelimb navicular bursae and 1 hind limb navicular bursa (systemic control group) at 6 hours. Triamcinolone acetonide concentrations in synovial fluid were quantified by use of high-performance liquid chromatography plus tandem mass spectrometry. Data were logarithmically transformed, and contrast analysis was performed on the 3 groups.

RESULTS

Triamcinolone acetonide was detected in navicular bursal samples in all groups. Groups 1 and 2 had significantly greater concentrations of triamcinolone acetonide than the systemic control group. There was no significant difference between groups 1 and 2.

CONCLUSIONS AND CLINICAL RELEVANCE

Triamcinolone acetonide diffused directly from the DIPJ into the navicular bursa in clinically normal horses, and diffusion was not affected by addition of hyaluronan. Injection into the DIPJ with triamcinolone acetonide or a triamcinolone acetonide-hyaluronan combination can potentially be used for treatment of navicular syndrome, but further studies are needed to determine whether triamcinolone acetonide diffuses similarly in horses with navicular syndrome.

Clinical findings, diagnosis, prevalence and predisposing factors for lameness localised to the middle carpal joint in young Standardbred racehorses

REASONS FOR PERFORMING STUDY

Lameness related to the middle carpal joint (MCJ) occurs in up to 30% of young Standardbred horses in race training and the incidence increase with radiographic severity of third carpal bone (C3) sclerosis on DPr-DDIO (skyline) view of the carpus. Factors predisposing horses to carpal injury have not been well investigated.

OBJECTIVES

To determine the importance of MCJ lameness as a cause of wastage in young Standardbred racehorses, stage of training at which it occurs and predisposing factors, and to describe clinical findings and diagnosis.

METHODS

Standardbred horses (n = 114) entering their first year of race training were examined at approximately 3-month intervals over 12-18 months. For 87 of the horses, a training diary was available and these horses were trained at 3 different stables, each using a different exercise regime. At each examination, forelimb conformation, MCJ effusion, MCJ lameness and radiographic findings were graded, and training history and reasons for lost training days recorded. Nuclear scintigraphy and exploratory arthroscopy were performed on a limited selection of horses. Results for horses that developed MCJ lameness during the study period were compared statistically with results for horses that did not.

RESULTS

Carpal lameness occurred in 28% of horses and was present in 56% with forelimb lameness. In most cases lameness was mild, bilateral and with little or no MCJ effusion and was attributed to subchondral bone pain associated with radiographic evidence of C3 sclerosis. Carpal lameness was the most common reason for >1 month's rest during the study period. It occurred at any stage of training but, in most cases, some speed training had begun. Of the variables studied, poor forelimb conformation and more intense speed training were predisposing factors.

CONCLUSIONS AND POTENTIAL RELEVANCE

The information gained should assist in making recommendations regarding training young Standardbreds to reduce the incidence of MCJ lameness. However, further investigations to determine the optimal training regime are warranted.

Radiographic evaluation of sclerosis of the third carpal bone associated with exercise and the development of lameness in Standardbred racehorses

REASONS FOR PERFORMING STUDY

Sclerosis of the third carpal bone is a common radiographic finding in both lame and sound racehorses, but there are no guidelines correlating degree of sclerosis and incidence of lameness.

OBJECTIVES

To develop a protocol for describing subchondral bone sclerosis in C3 on dorsoproximal-dorsodistal oblique (DPr-DDiO) radiographs of the carpus and to correlate these changes with exercise history and carpal lameness.

METHODS

One hundred and six Standardbreds entering their first year of training (exercise group) and 7 age-matched Standardbreds at pasture (controls) were examined at approximately 3 month intervals over 12-18 months. Examinations consisted of lameness evaluation and carpal radiographs (DPr-DDiO and flexed lateromedial projections). A grading system (very mild, mild, moderate and severe) for C3 sclerosis seen on the DPr-DDiO radiograph was developed that utilised a combination of the criteria of trabecular thickening (trabecular score; TS) and total percent area of the C3 radial facet affected (TAA).

RESULTS

Exercise group horses showed significant increase in TS and TAA throughout training compared to control horses. Middle carpal joint lameness developed in 32/106 (30%) exercise group horses and none of the control horses. Incidence of middle carpal joint (MCJ) lameness was lower in horses with mild (2/30, 6.7%) than moderate (10/32, 31.2%) and severe (20/44, 45.4%) sclerosis throughout training.

CONCLUSIONS

Horses with higher grades of sclerosis, as defined by this novel grading system, were more likely to develop MCJ lameness at some point of training. The proposed grading system gave a quantitative assessment of radiographic sclerosis that could then be used to correlate increasing severity of sclerosis with increasing incidences of lameness.

POTENTIAL RELEVANCE

These results serve as a basis for further investigation into determining the degree of C3 sclerosis at which pathological changes and lameness can be expected.

High-intensity exercise induces structural, compositional and metabolic changes in cuboidal bones--findings from an equine athlete model

Fatigue fracture of cuboidal bones occurs in the human foot as well as the equine carpus. The racehorse provides a naturally-occurring model to study the effects of high-intensity exercise on the morphology and metabolism of cuboidal bones. We studied both the mineral and the collagenous matrix of the third (C(3)) and radial (C(r)) carpal bones of raced and non-raced Thoroughbred (TB) horses. We hypothesised that racehorses would show increases in the mineral component of these bones and post-translational modifications of the collagenous matrix alongside changes in markers of collagen remodelling and bone formation. C(3) and C(r) carpal bones were retrieved from raced TB horses (n=14) and non-raced TB horses (n=11). Standardised proximal-distal sections were taken from each bone and these were sliced transversely to study the proximal-distal differences in bone metabolism from the subchondral plate through to trabecular bone. Histomorphometry and bone mineral density measurements were performed in parallel with biochemical analyses including total collagen, collagen synthesis and cross-links, matrix metalloproteinases-2 and 9 and their inhibitors, calcium and phosphate, and bone alkaline phosphatase. The results of this study show that, while there is a net increase in bone formation in the racehorses, there is additionally an increase in bone collagen synthesis and remodelling, particularly within the trabecular regions of the bone. The increase in bone density would lead to greater stiffness, particularly in the cortical bone, and failure of this 'stiffer' cortical bone may result from its lack of support from the rapidly remodelling and structurally weakened underlying trabecular bone.

Evidence-based musculoskeletal surgery in horses

Musculoskeletal disorders comprise a large portion of the conditions treated by equine veterinarians. Surgical intervention is the treatment of choice in many cases. The body of literature describing and exploring surgical correction of musculoskeletal disorders in horses is steadily growing but still lacking. At this juncture, we can use what information we have with the understanding that as the quality of research advances, we should apply stricter standards to the evidence we use to answer our clinical questions.

Evaluation of avocado and soybean unsaponifiable extracts for treatment of horses with experimentally induced osteoarthritis

OBJECTIVE

To evaluate the use of a combination of avocado and soybean unsaponifiable (ASU) extracts for the treatment of experimentally induced osteoarthritis in horses.

ANIMALS

16 horses.

PROCEDURES

Osteoarthritis was induced via osteochondral fragmentation in 1 middle carpal joint of each horse; the other joint underwent a sham operation. Horses were randomly allocated to receive oral treatment with ASU extracts (1:2 [avocado-to-soybean] ratio mixed in 6 mL of molasses; n = 8) or molasses (6 mL) alone (placebo treatment; 8) once daily from days 0 to 70. Lameness, response to joint flexion, synovial effusion, gross and histologic joint assessments, and serum and synovial fluid biochemical data were compared between treatment groups to identify effects of treatment.

RESULTS

Osteochondral fragmentation induced significant increases in various variables indicative of joint pain and disease. Treatment with ASU extracts did not have an effect on signs of pain or lameness; however, there was a significant reduction in severity of articular cartilage erosion and synovial hemorrhage (assessed grossly) and significant increase in articular cartilage glycosaminoglycan synthesis, compared with placebo-treated horses.

CONCLUSIONS AND CLINICAL RELEVANCE

Although treatment with ASU extracts did not decrease clinical signs of pain in horses with experimentally induced osteoarthritis, there did appear to be a disease-modifying effect of treatment, compared with findings in placebo-treated horses. These objective data support the use of ASU extracts as a disease-modifying treatment for management of osteoarthritis in horses.

Intra-Articular Injections for Joint Disease in Horses

Lameness remains an important source of reduced performance in many types of horses. Pain referable to joints is among the most common causes, and intra-articular injections remain a common and important means of addressing lameness referable to joints in horses.

Quantitative comparison of three commonly used treatments for navicular syndrome in horses

OBJECTIVE

To quantitatively compare 3 commonly used treatments for navicular syndrome (NS) in horses: heel-elevation shoeing alone, heel-elevation shoeing and phenylbutazone administration, heel-elevation shoeing and injection of the distal interphalangeal joint (DIPJ) with triamcinolone acetonide (TA), and all 3 treatments in combination.

ANIMALS

12 horses with NS.

PROCEDURE

A force plate was used to measure baseline peak vertical ground reaction force (PVGRF) of the forelimbs. Each horse's forelimbs were shod with 3 degrees heel-elevation horseshoes; PVGRF was measured 24 hours and 14 days after shoeing. Fourteen days after shoeing (following data collection), phenylbutazone (4.4 mg/kg, i.v., q 12 h) was administered (5 treatments). Two hours after the fifth treatment, PVGRF was measured; TA (6 mg) was injected into the DIPJ of the forelimb that generated the lower baseline PVGRF Fourteen days later, PVGRF was measured. Phenylbutazone was administered as before, and PVGRF was measured. Percentage body weight of force (%BWF) was calculated from PVGRF measurements and used for comparisons.

RESULTS

14 days after shoeing, mean %BWF in both forelimbs significantly increased from baseline; additional administration of phenylbutazone significantly increased %BWF applied from the more lame forelimb. Compared with shoeing alone, there was no significant change in %BWF after injection of the DIPJ with TA in shod horses.

CONCLUSIONS AND CLINICAL RELEVANCE

Heel-elevation shoeing alone and in combination with phenylbutazone administration quantitatively decreased lameness in horses with NS. Although not significant, additional DIPJ injection with TA resulted in further quantitative decrease in lameness, compared with that achieved via shoeing alone.

Effects of dosage titration of methylprednisolone acetate and triamcinolone acetonide on interleukin-1-conditioned equine articular cartilage explants in vitro

REASONS FOR PERFORMING STUDY

Osteoarthritis is a frequent sequela of joint disease, especially with severe injuries or if attempts at therapy are unsuccessful. Negative and positive effects of corticosteroid treatment of articular cartilage have been demonstrated by in vitro and in vivo studies.

OBJECTIVES

To assess the metabolic effects of varying dosages of methylprednisolone acetate (MPA) and triamcinolone acetonide (TA) on interleukin-1alpha (IL-1) conditioned equine cartilage explants. Our hypothesis was that lower dosages of corticosteroids would be less detrimental to cartilage metabolism than higher dosages. TA would be less detrimental to cartilage metabolism than MPA.

METHODS

Treatment groups included articular cartilage explants with no IL-1 (control), IL-1 alone, and IL-1 plus 10, 5, 1 and 0.5 mg/ml MPA or 1.2, 0.6, 0.12 and 0.06 mg/ml TA. Explants were labelled with 35SO4 prior to the beginning and end of the experiment to assess glycosaminoglycan (GAG) degradation and synthesis, respectively. Total GAG content in media and explants and total cartilage DNA were also analysed.

RESULTS

MPA and TA reduced GAG synthesis compared to control and IL-1 alone. The highest dosage of MPA (10 mg/ml) reduced GAG synthesis less than lower dosages of MPA and all dosages of TA. Compared to IL-1 alone, all dosages of TA and lower dosages of MPA increased GAG degradation. MPA at 10 mg/ml reduced GAG degradation. Both MPA and TA increased media GAG content compared to control and IL-1 explants. Total cartilage GAGs were unchanged with MPA, but reduced with TA, compared with IL-1 alone. Total cartilage DNA was decreased with MPA and increased with TA compared to IL-1 and control explants.

CONCLUSIONS

MPA and TA did not counteract the negative effects of IL-1 and did not maintain cartilage metabolism at control levels. Lower dosages of MPA and TA were not less detrimental to cartilage metabolism than higher dosages. TA did not appear to be less harmful than MPA on cartilage metabolism. The results of this study differ from the findings of comparable in vivo studies.

POTENTIAL RELEVANCE

The low numbers of horses used in this study limits extrapolation of these findings to the equine population; however, this study also questions the clinical relevance of this in vitro model.

Managing chronic arthritis

Many compounds are being investigated for the control of symptoms of osteoarthritis in people and animals. Ideally, treatment should include analgesia, inflammation control, and chondroprotection. With further progress in this area, combination therapies tailored to the needs of the individual animal should enable us to maximize efficacy and minimize side effects. Only a few of the newer therapies and pharmaceutic agents have been investigated in the horse, however. With more rigorous investigation, they may be determined to be ineffective or unsafe. Meanwhile, as much information should be gathered from manufacturers as possible so as to ensure that appropriate recommendations are made.

Effects of anti-arthritic drugs on proteoglycan synthesis by equine cartilage

The concentration-effect relationships of phenylbutazone, indomethacin, betamethasone, pentosan polysulphate (PPS) and polysulphated glycosaminoglycan (PSGAG), on proteoglycan synthesis by equine cultured chondrocytes grown in monolayers, and articular cartilage explants were measured. The effect of PSGAG on interleukin-1beta induced suppression of proteogycan synthesis was also investigated. Proteoglycan synthesis was measured by scintillation assay of radiolabelled sulphate (35SO4) incorporation. Polysulphated glycosaminoglycan and PPS stimulated proteoglycan synthesis in chondrocyte monolayers in a concentration-related manner with maximal effects being achieved at a concentration of 10 microg/mL. Polysulphated glycosaminoglycan reversed the concentration-related suppression of proteoglycan synthesis induced by interleukin-1beta. Neither PSGAG nor PPS exerted significant effects on radiolabel incorporation in cartilage explants. Betamethasone suppressed proteoglycan synthesis by both chondrocytes and explants at high concentrations (0.1-100 microg/mL), but the effect was not concentration-related. At low concentrations (0.001-0.05 microg/mL) betamethasone neither increased nor decreased proteoglycan synthesis. Phenylbutazone and indomethacin increased radiolabel incorporation in chondrocyte cultures but not in cartilage explants at low (0.1, 1 and 10 microg/mL), but not at high (20 and 100 microg/mL) concentrations. These findings may be relevant to the clinical use of these drugs in the treatment of equine disease.

The effect of intra-articular methylprednisolone acetate and exercise on equine carpal subchondral and cancellous bone microhardness

Dorsal carpal osteochondral injury is a major cause of lameness in horses undergoing high intensity training. Intra-articular corticosteroid treatment is used commonly to manage exercise-associated articular pain, but its use remains highly controversial in the equine athlete. This project, therefore, aimed to compare the mechanical properties of intra-articular MPA and diluent-treated middle carpal subchondral and cancellous bone in horses undergoing a short-term treadmill exercise programme. It was hypothesised that subchondral and cancellous bone mechanical properties are influenced by intra-articular administration of methylprednisolone acetate (MPA). Eight 2-year-old female horses had MPA or diluent administered into contralateral middle carpal joints at 14 day intervals, for a total of 4 treatments per horse. Horses underwent a standard treadmill exercise protocol until euthanasia (Day 70). Standard sites were located on the dorsal aspect of third, radial and intermediate carpal bones. Osteochondral samples from each test site were divided into subchondral bone and cancellous bone portions. These were dried, resin-embedded and gold-coated. Microhardness measurements were obtained at each test site. No significant effect of intra-articular treatment was detected. At each site, cancellous bone trabecular struts had an 18-19% higher microhardness value than the overlying subchondral bone. These findings indicate that intra-articular administration of MPA at this dose has no effect on subchondral or cancellous bone adaptation to short-term exercise and, therefore, on the propensity of carpal bones to injury. Further investigation into the calcified cartilage layer, effect of different corticosteroid preparations and diffusion of medication are required.

Corticosteroids alter the differentiated phenotype of articular chondrocytes

Experimental evidence suggests that recommended dosages of some corticosteroids used clinically as antiinflammatory agents for treating arthropathies damage articular cartilage, but low dosages may be chondroprotective. The purpose of this study was to evaluate how different concentrations of methylprednisolone affect chondrocyte function and viability. Articular cartilage and chondrocytes were obtained from young adult horses, 1.5-3.5 years of age. Corticosteroid-induced changes in collagen expression were studied at the transcriptional level by Northern blot analyses and at the translational level by measuring [3H]-proline incorporation into [3H]-hydroxyproline. Fibronectin mRNA splicing patterns were evaluated with ribonuclease protection assays. Cytotoxicity was studied using erythrosin B dye exclusion. Steady-state levels of type II procollagen mRNA decreased without concurrent changes in type I procollagen expression as the medium methylprednisolone concentrations were increased from 1 x 10(1) to 1 x 10(8) pg/ml, dropping below 10% of control values by 1 x 10(5) pg/ml. Cytotoxicity occurred as methylprednisolone levels were increased further from 1 x 10(8) to 1 x 10(9) pg/ml. Changes in total collagen (protein) synthesis were less pronounced, but also demonstrated significant suppression between 1 x 10(4) and 1 x 10(8) pg/ml. Corticosteroid-induced changes in fibronectin isoform levels were evaluated in articular cartilage samples without in vitro culture. The cartilage-specific (V + C)(-) isoform was suppressed in both normal and inflamed joints by a single intraarticular injection (0.1 mg/kg) of methylprednisolone. Combined, these data indicate that methylprednisolone suppresses matrix protein markers of chondrocytic differentiation. Decreased and altered chondrocyte expression of matrix proteins likely contributes to the pathogenesis of corticosteroid-induced cartilage degeneration.

The effects of methylprednisolone on normal and monocyte-conditioned medium-treated articular cartilage from dogs and horses

OBJECTIVE

To study in vitro (1) the dose-response relationships between proteoglycan metabolism in normal and corticosteroid-treated articular cartilage; (2) long-term proteoglycan metabolism after treatment of articular cartilage with corticosteroids; and (3) the effect of corticosteroids on proteoglycan metabolism in articular cartilage treated with monocyte-conditioned medium (MCM).

STUDY DESIGN

Equine and canine articular cartilage explants were treated with corticosteroids and MCM. Proteoglycan synthesis and degradation were measured by radioactive labeling in short-term culture, and the long-term effect of corticosteroid treatment on proteoglycan metabolism was studied in normal explants.

ANIMALS

Two young cross-breed horses and 3 young Labrador retrievers.

METHODS

Equine articular cartilage explants were incubated in medium containing methylprednisolone sodium succinate (MPS) at 0, .001, .01, .1, 1, and 10 mg/mL (final concentration) for 1 day and then in fresh medium without MPS. Proteoglycan synthesis was measured by incorporation of sodium [35S]sulfate at 1, 3, 7, 10, and 13 days after initial treatment with MPS. Proteoglycan release was measured from separate explants prelabeled with sodium [35S]sulfate and treated similarly. Equine articular cartilage explants were treated with equine MCM simultaneously with, and 24 hours before MPS, at 0, 0.01, 0.1, 1, or 5 mg/mL for 72 hours. Proteoglycan synthesis and degradation in these explants was compared. Proteoglycan synthesis and degradation were measured similarly in canine articular cartilage explants treated simultaneously with canine MCM and MPS at 0, 0.001, 0.01, 0.1, 1 and 10 mg/mL for 72 hours. Equine articular cartilage explants treated with 0, 0.01, 0.1, 1, and 5 mg/mL of MPS for 72 hours were evaluated histologically.

RESULTS

Proteoglycan synthesis in normal equine articular cartilage was severely depressed by 10 mg/mL MPS for 24 hours, and proteoglycan synthesis failed to recover after 13 days of culture in medium without MPS. Cartilage treated with 5 mg/mL MPS had pyknotic chondrocyte nuclei and empty lacunae. Concentrations of 1 and 0.1 mg/mL MPS depressed proteoglycan synthesis in normal equine cartilage explants. For these 2 concentrations, proteoglycan synthesis recovered 2 days after MPS removal and increased significantly (P < .05) 7 days after treatment with MPS compared with controls without MPS. Concentrations of 0.001 and 0.01 mg/mL MPS did not significantly affect proteoglycan synthesis in normal equine cartilage explants. Cumulative proteoglycan loss over 13 days in culture from normal equine explants treated for 24 hours with different concentrations of MPS was not significantly different between treatment groups at any time point. MCM significantly depressed proteoglycan synthesis in both canine and equine articular cartilage explants and significantly increased proteoglycan release. These effects were prevented in the canine explants by simultaneous treatment with MPS at 1 and 0.1 mg/mL, and proteoglycan release induced by MCM in equine articular cartilage was inhibited by 1 mg/mL MPS.

CONCLUSIONS

Concentrations of 1.0 and 0.1 mg/mL MPS alleviated articular cartilage degradation in MCM-treated articular cartilage in vitro. These concentrations of MPS in contact with normal cartilage explants for 24 hours are unlikely to be detrimental in the long term to proteoglycan synthesis. The response of articular cartilage to MPS was affected by treatment with MCM so that results of experiments with normal articular cartilage explants may not reflect results obtained with abnormal cartilage.

CLINICAL RELEVANCE

It may be possible to find an intraarticular concentration of corticosteroid that protects articular cartilage against cytokine-induced matrix degradation yet not have prolonged or permanent detrimental effects on chondrocyte matrix synthesis.

Galloping exercise induces regional changes in bone density within the third and radial carpal bones of Thoroughbred horses

This study was performed to test the hypothesis that a localised bone hypertrophy could occur within the subchondral cancellous architecture of the third and radial carpal bones. Using 2 levels of controlled and defined exercise, it was observed that a high intensity treadmill exercise protocol resulted in functional adaptation of the carpal bones. The increase in trabecular thickening and density was seen to be localised to those regions underlying common sites of cartilage degradation, the interface of the thickened trabeculae with the normal architecture in the third carpal bone was coincident with a common site of clinical fractures. The bone changes were determined both qualitatively on examination of slab radiographs and quantified by dual energy x-ray absorptiometry. The findings from this study are relevant to mechanical factors involved in the pathophysiology of joint degeneration. The potential clinical implications of this study are in relation to changes in the type and duration of exercise regimens used in training of equine athletes. The rapid response of bone to mechanical stimulation has implications in the longer term for localised cartilage degradation. Imaging techniques could be developed to monitor these early bone changes in the specific areas identified in this study and thus allow appropriate changes in training intensity to minimise subsequent damage to the articular surface.

Calcified cartilage morphometry and its relation to subchondral bone remodeling in equine arthrosis

The calcified layer of articular cartilage is known to be affected by age and mechanical factors that may play a role in the development of arthrosis. Because these factors are also related to subchondral remodeling and sclerosis, a morphometric study was carried out in fluorochrome-labeled animals to determine whether the level of subchondral remodeling affected the thickness of the calcified cartilage layer and its irregularity and vascularity at the interface with subchondral bone. These parameters were also studied at a site of increased mechanical stress. The area and thickness of the calcified cartilage layer was determined in basic fuchsin-stained ground sections (120 microm). The irregularity of the chondro-osseous interface was expressed as the ratio of its length to that of the relatively straight tidemark (Int/Tid) and the number of abutting vessels with and without fluochrome labels were counted (N.Ves/Tid,%L.Ves/Tid). These were compared with single-labeled surface (sLS/BS, %) in subchondral bone, which was used as an index of remodeling. In a group of 12 horses, in which one carpus had an osteochondral fragment surgically created 10 weeks earlier, there was activation of subchondral remodeling in the third carpal bone opposite the fragment. An increase in %L.Ves/Tid (p < 0.01) at the interface was correlated with the increase in %sLS/BS in subchondral bone (r=0.431, p=0.035). The number of abutting vessels and the interface irregularity were not significantly changed on the fragmented side. In the metacarpal condyles from the fetlock joints of the same horses there were no differences associated with the surgically created fragment in the carpus and no correlation of %L.Ves/Tid with subchondral %sLS/BS. At a site where mechanical overload and traumatic osteochondrosis is known to occur on the palmar surface, the calcified cartilage was thinner, and the interface irregularity tended to be greater. These findings indicate that activated subchondral remodeling extends to involve the calcified layer, but the thickness and irregularity of the calcified cartilage are not consistently related to current subchondral remodeling. At sites of mechanical overload the calcified cartilage was thinner and the interface tended to be more irregular, suggesting previous increased remodeling.

Subchondral bone failure in an equine model of overload arthrosis

Gross examination of metacarpo-/metatarsophalangeal (fetlock) joints from racehorses revealed defects on the condylar surface that ranged from cartilage fibrillation and erosion to focal cartilage indentations and cavitation in subchondral bone characteristic of traumatic osteochondrosis. Because these lesions represented a spectrum of mechanically induced arthrosis in which microdamage is thought to play a role, a histologic study of sagittal sections was made to study the morphogenesis. Subchondral bone failure developed beneath a flattened section of the condyle where the margin of the sesamoid bone produces compression as well as shear on impact of the foot with the ground. Milder lesions had thickening of subchondral bone and underlying trabeculae. With advancing sclerosis an increased amount of osteocyte necrosis was present. Occasional vascular channels with plugs of matrix debris and cells were present just beneath the cartilage. There was increased prominence of subchondral vessels, and osteoclastic remodeling was seen in and around the sclerotic zone. Apparent fragmentation lines in the subchondral bone suggested increased matrix fragility. Irregular trabecular microfractures developed at a depth of a few millimeters. Increased vascularity with hemorrhage, fibrin, and fibroplasia could be seen in enlarged marrow spaces at this more advanced stage. The overlying articular cartilage was variably indented but remained largely viable with degeneration and erosion limited to the superficial layers. Focally, breaks in the calcified layer appeared to lead to collapse and cartilage infolding. In metacarpal condyles from experimental horses run on a treadmill, there were milder changes at the site. The subchondral bone was increased in volume and there was increased diffuse staining with basic fuchsin, but no increase in the number of microcracks was seen. The findings in the racehorses indicate that the equine fetlock condyle is a consistent site of overload arthrosis in which microfracture and failure in subchondral bone may occur. Controlled exercise in treadmill horses may provide a model in which to study the pathogenesis.