Effect of Betamethasone and Exercise on Equine Carpal Joints With Osteochondral Fragments

Osteochondral fragments were created arthroscopically on the distal aspect of both radial carpal bones in 12 horses. On day 14 after surgery, one middle carpal joint of each horse was injected with 2.5 mL Betavet Soluspan (3.9 mg betamethasone sodium phosphate and 12 mg betamethasone acetate per milliliter) and the contralateral joint was injected with 2.5 mL saline as a control. Intra-articular treatments were repeated on day 35. On day 17, six horses began exercising 5 days per week on a high-speed treadmill. The other six horses were kept in box stalls throughout the study as nonexercised controls. On day 56, all horses were examined clinically and radiographically and then were euthanatized. Samples were obtained for histological, his-tochemical, and biochemical evaluation. Mild lameness was observed in five of the six exercised horses at day 56; four horses were lame in the control limb and one horse was lame in the treated limb. Of the five nonexercised horses evaluated for lameness, two were lame in the control limb, two were lame in the treated limb, and one was lame in both the control and the treated limb. No differences were noted on radiographs or palpation of steroid treated limbs versus control limbs. Firm reattachment of the osteochondral fragment to the radial carpal bone occurred in all but three joints. Gross cartilage damage was not different between steroid-treated joints and joints injected with saline. Histologically, there were no significant detrimental effects of betamethasone with or without exercise, but there was a tendency for more pathological change in treated joints. There was a trend toward decreased glycosaminoglycan staining in steroid treated joints of rested horses, whereas exercised horses had similar glycosaminoglycan staining in treated and control joints. No significant difference in the water content or uronic acid concentration was detected between treated and control joints. Intra-articular betamethasone administration in this carpal chip model was not associated with any significant detrimental effects in either rested or exercised horses.     

Clinical effects of exercise on subchondral bone of carpal and metacarpophalangeal joints in horses

OBJECTIVE: To determine effects of treadmill exercise on subchondral bone of carpal and metacarpophalangeal joints of 2-year-old horses. ANIMALS: 12 healthy 2-year-old horses. PROCEDURE: Horses were randomly assigned to the control (n = 6) or exercised (6) groups. Horses in the exercised group ran on a high-speed treadmill 5 d/wk for 6 months. Horses in the control group were hand walked for the same amount of time. Results of clinical, radiographic, nuclear scintigraphic, and computed tomographic examinations, and serum and synovial concentrations of biochemical markers of bone metabolism were compared between groups. RESULTS: Exercised horses were significantly lamer at the end of the study than control horses. Radionuclide uptake in the metacarpal condyles, but not in the carpal joints, was greater in exercised horses, compared with control horses. Exercised horses also had a higher subchondral bone density in the metacarpal condyles than control horses, but such differences were not detected in the carpal bones. CONCLUSIONS AND CLINICAL RELEVANCE: None of the diagnostic techniques evaluated was sufficiently sensitive to detect all osteochondral damage. Computed tomography and computed tomographic osteoabsorptiometry were superior to conventional radiography for detecting small osteochondral fragments. Nuclear scintigraphy was a sensitive indicator of subchondral bone change but lacked specificity for describing lesions and discerning normal bone remodeling from damage. Newer techniques such as computed tomography may help clinicians better diagnose early and subtle joint lesions in horses prior to development of gross joint damage.     

GROSS AND HISTOPATHOLOGIC CORRELATION OF LOW‐FIELD MAGNETIC RESONANCE IMAGING FINDINGS IN THE STIFLE OF ASYMPTOMATIC HORSES

With the recent introduction of a 0.25T rotating MRI system, clinical evaluation of the equine stifle joint is now possible in the average equine athlete. A recent publication described common abnormalities of horses with stifle lameness detected with a low‐field MRI system; however, postmortem corroboration of the lesions detected was not possible. Therefore, our objective was to compare postmortem findings with low‐field MRI findings in equine cadaver stifle joints. Ten fresh cadaver stifle joints from horses without clinical signs of stifle disease were evaluated using low‐field MRI, gross dissection, and histopathology. In eight stifles, either the lateral or medial cranial meniscotibial ligament had an irregular shape, fiber separation, or moderate abnormal signal intensity (SI) on all sequences. In five stifles, the medial femoral condyle had articular cartilage fibrillation with or without an osteochondral defect over the weight bearing surface of the medial femoral condyle. All stifles had abnormal SI on all sequences within the patellar ligaments that corresponded with adipose tissue infiltrating between the collagen bundles. Other abnormalities identified included articular cartilage fibrillation of the tibial condyles in three stifles, and articular cartilage fibrillation with chondral defects in the patella in three stifles. All abnormalities detected with low‐field MRI were corroborated by gross dissection. Findings from the current study supported the use of low‐field MRI for detection of stifle joint lesions in horses and demonstrated that some stifle joint pathologies may be subclinical in horses.     

Interleukin-6 and tumour necrosis factor in synovial fluid from horses with carpal joint pathology

The carpal joints are common sites of traumatic arthritis and osteoarthritis (OA) in athletic horses. The pro-inflammatory cytokines interleukin (IL)-6 and tumour necrosis factor (TNF) may be of great importance in the development of intra-articular lesions. The aim of the present study was to investigate possible associations between synovial fluid levels of bioactive IL-6 and TNF and different types of joint lesions seen in traumatic arthritis and OA. Synovial fluid was collected from horses with carpal lameness immediately before arthroscopic surgery. Articular cartilage, synovial membranes and intra-articular ligaments were assessed macroscopically at arthroscopy. Synovial fluid levels of IL-6 and TNF were determined by bioassays, and the cytokine levels between different grades of morphologic changes in each type of assessed tissue were compared. The highest levels of IL-6 were detected in joints with chip fractures. All joints with chip fractures also showed some degree of synovitis. Tumour necrosis factor bioactivity was low and not associated with any joint lesion. Hence, TNF is not useful as a biomarker indicating a specific joint lesion in equine traumatic arthritis or OA. We conclude that a dramatic increase of IL-6 in synovial fluid indicates the presence of osteochondral fragmentation, although low or undetectable levels of IL-6 do not exclude chip fractures. The role of IL-6 in the disease process of osteochondral fragmentation needs further investigation.     

Evaluation of samarium-153 for synovectomy in an osteochondral fragment-induced model of synovitis in horses

OBJECTIVE: To determine the effects of intraarticular administration of Samarium-153 (153Sm) bound to hydroxyapatite microspheres (153SmM) on an osteochondral chip-induced synovitis. STUDY DESIGN: Sixty days after implantation of autogenous osteochondral fragments in the middle carpal and metacarpophalangeal joints, 153SmM was administered into 1 joint of each type. The contralateral joints were used as untreated controls. ANIMALS OR SAMPLE POPULATION: Fifteen horses without preexisting joint disease were randomly divided into 2 groups (7 in the carpal group, 8 in the metacarpophalangeal group). METHODS: Horses had osteochondral fragments that were harvested from the lateral ridge of the trochlea of the talus and implanted bilaterally into a middle carpal joint and a metacarpophalangeal joint; the opposite joint type served as a control. Sixty days later, 10 to 15 mCi of 153SmM (20 to 50 microm diam) was injected into the fragment-implanted joints. Three horses were treated with nonradioactive hydroxyapatite fragments. Horses were examined clinically until they were killed 14 or 30 days later. Control and treated joints were examined grossly and microscopically to determine the effects of 153SmM on synovial membrane and cartilage. RESULTS: Intraarticular 153SmM caused a transient flare with lameness, effusion, and edema for 48 to 72 hours. Implanted osteochondral chips induced a synovitis characterized by variable degrees of joint damage and synovial infiltrate. Use of 153SmM resulted in synovectomy of variable depth and extent. CONCLUSIONS: Intraarticular 153SmM may be a useful method for synovectomy of inflamed synovial membrane. CLINICAL RELEVANCE: With further testing, radioactive pharmaceuticals might become useful clinical treatments for persistent synovitis not responsive to conventional techniques.     

Effects of intra-articular administration of methylprednisolone acetate on normal articular cartilage and on healing of experimentally induced osteochondral defects in horses.

The effects of intra-articular administration of methylprednisolone acetate (MPA) on the healing of full-thickness osteochondral defects and on normal cartilage were evaluated in 8 horses. In group-1 horses (n = 4), a 1-cm-diameter, full-thickness defect was created bilaterally in the articular cartilage on the dorsal distal surface of the radial carpal bone. Cartilage defects were not created in group-2 horses (n = 4). One middle carpal joint was randomly selected in each horse (groups 1 and 2), and treated with an intra-articular injection of 100 mg of MPA, once a week for 4 treatments. Injections began 1 week after surgery in group-1 horses. The contralateral middle carpal joint received intra-articular injections of an equivalent volume of 0.9% sodium chloride solution (SCS), and served as a control. Horses were evaluated for 16 weeks, then were euthanatized, and the middle carpal joints were examined and photographed. Synovial and articular cartilage specimens were obtained for histologic and histochemical evaluation. Gross morphometric evaluation of the healing defects in group-1 horses revealed that 48.6% of the defect in control joints and 0% of the defect in MPA-treated joints was resurfaced with a smooth, white tissue, histologically confirmed as fibrocartilage. This replacement tissue was a firmly attached fibrocartilage in control joints and a thin fibrous tissue in MPA-treated joints. The articular cartilage in joints treated with MPA had morphologic changes, including chondrocyte cluster formation, loss of palisading architecture, and cellular necrosis in both groups of horses.(ABSTRACT TRUNCATED AT 250 WORDS)     

Surgical repair of radial carpal bone fractures in two racehorses

A 3-year-old Standardbred gelding (Case 1) and a 2-year-old Thoroughbred gelding (Case 2) were referred for surgical evaluation of a left radial carpal bone (RCB) fracture, sustained during training. Clinical findings at the time of initial examination included a palpable effusion within the left middle carpal joint in both horses and marked signs of pain and reduced range of motion on flexion of the affected carpus. In both horses, the RCB fracture was evident on the following radiographic views of the carpus: dorsolateral–palmaromedial oblique (30° off lateromedial) and flexed lateromedial. An additional loose wedge-shaped osteochondral fragment at the proximal articular surface of the RCB could be seen in Case 2. Both horses underwent surgical reduction and repair of the fracture between 1 and 2 days following the initial injury, which consisted of arthroscopic removal of any intra-articular osteochondral fragments, and arthroscopic assisted-interfragmentary compression via a standard dorsomedial and dorsolateral approach to the antebrachiocarpal joint (ACJ) and middle carpal joints (MCJ). The two horses returned to function as racehorses, 6 months (Case 1) and 16 months (Case 2) after surgery. The RCB is a relatively uncommon site for large carpal fractures in horses. The clinical presentation and findings from this report were similar to that of third carpal bone (C3) slab fractures, confirming that surgical repair is indicated in selected cases of RCB fractures.     

Subchondral lucency of the third carpal bone in Standardbred racehorses: 13 cases (1982-1988)

Thirteen Standardbreds had subchondral lucency of the third carpal bone (C3), described as single or multiple central areas of C3 bone loss in the radial fossa. Sclerosis of the radial fossa was also detected. The mean age of 9 stallions, 3 mares, and 1 gelding was 4.1 years (range, 3 to 7 years). All horses had an acute moderate to severe lameness referable to the middle carpal joint. A dorsoproximal dorsodistal (skyline) radiographic projection was most useful and identified mild (3 horses), moderate (6 horses), and severe (4 horses) subchondral lucency and sclerosis of the radial fossa. The margin of C3 was intact dorsal to the lucent areas in all horses. In 12 horses, arthroscopic surgical evaluation and curettage of the lesion were performed. Of the 9 horses monitored long enough to allow racing, 8 horses (89%) returned to racing, although only 6 (75%) raced at the same degree of competition. Subchondral lucency of C3 resulted from chronic damage to C3 with subsequent osteochondral collapse or acute C3 proximal surface osteochondral fracture.     

In vivo kinetic study on uptake and distribution of intramuscular tritium-labeled polysulfated glycosaminoglycan in equine body fluid compartments and articular cartilage in an osteochondrial defect model

The uptake and distribution of intramuscularly (IM) administered tritium-labeled polysulfated glycosaminoglycan (³H-PSGAG) in serum, synovial fluid, and articular cartilage of eight horses was quantitated, and hyaluronic acid (HA) concentration of the middle carpal joint was evaluated in a pharmacokinetic study. A full-thickness articular cartilage defect, created on the distal articular surface of the left radial carpal bone of each horse served as an osteochondral defect model. ³H-PSGAG (500 mg) was injected IM, between 14 and 35 days after creation of the defects. Scintillation analysis of serum and synovial fluid, collected from both middle carpal joints at specific predetermined times up to 96 hours post-injection, revealed mean ³H-PSGAG concentrations peaked at 2 hours post-injection. ³H-PSGAG was detected in cartilage and subchondral bone 96 hours post-injection in samples from all eight horses. There were no statistically significant differences in ³H-PSGAG concentration of synovial fluid or cartilage between cartilage defect and control (right middle carpal) joints.

HA assay of synovial fluid revealed concentrations significantly increased at 24, 48, and 96 hours post-injection in both joints. The concentration nearly doubled 48 hours post-injection. However, no statistically significant differences were found between synovial concentrations of HA in cartilage defect and control joints.

³H-PSGAG administered IM to horses, was distributed in the blood, synovial fluid, and articular cartilage. HA concentrations in synovial fluid increased after IM administration of polysulfated glycosaminoglycan.     

Fate and effect of autogenous osteochondral fragments implanted in the middle carpal joint of horses.

Four autogenous osteochondral fragments removed from the lateral trochlear ridge of the talus were arthroscopically placed as loose bodies in a randomly selected middle carpal joint in each of 10 horses. The contralateral middle carpal joint, subjected to a sham procedure, served as control. Postoperative treatment was consistent with that for clinical arthroscopic patients. Lameness evaluation, radiographic examination, carpal circumference measurement, and synovial fluid analysis were performed before and at scheduled intervals after surgery. After a 2-month confinement, horses were subjected to an increasing level of exercise. Horses were euthanatized at intervals through 6 months. Gross and microscopic evaluations were performed on remaining fragments, articular cartilage, and synovial membrane of each middle carpal joint. Increased joint circumference, effusion, lameness, and degenerative joint disease distinguished implanted from control joints over the 6-month period. Implanted joints were characterized by grooved, excoriated cartilage surfaces, and synovium that was thick, erythematous, and irregular. At 4 weeks, implants were found to have adhered to synovium at their subchondral bone surface. The bone within fragments was undergoing necrosis, while cartilage was preserved. At 8 weeks, fragments were radiographically inapparent, grossly evident as pale plaques on the synovial surface, and composed of dense fibrous connective tissue. Synovial membrane specimens from implanted joints had inflammatory change characterized by mononuclear cell infiltration 2 months after implantation. Physical damage was apparent within articular cartilage of implanted joints at 2 months, and was significant (P less than 0.05) at 6 months after surgery. Chondrocyte degenerative change was significant (P less than 0.05) at 6 months after surgery. Focal reduction in safranin-O uptake was observed in cartilage layers adjacent to physical defects. Osteochondral loose bodies of the size implanted in the middle carpal joint of horses in this study were resorbed by the synovium within 2 months. Synovitis and significant articular cartilage damage were associated with the implanted fragments. Regardless of origin, free osteochondral fragments within the middle carpal joint should be removed, and methods to prevent residual postoperative debris should be implemented to reduce potential for articular pathologic change.     

MAGNETIC RESONANCE ANATOMY OF THE CARPUS OF THE HORSE DESCRIBED FROM IMAGES ACQUIRED FROM LOW‐FIELD AND HIGH‐FIELD MAGNETS

Cadaver carpi of 30 mature horses with no history of carpal or proximal metacarpal pain were examined using low‐field (0.27 T) and high‐field (1.5 T) magnetic resonance imaging (MRI). Normal MRI anatomy in transverse, sagittal, and dorsal plane images was determined by comparison with anatomical specimens and standard texts. Subchondral bone and cortical bone thickness measurements were obtained from standardised sites. There was variable subchondral bone thickness in the radius and carpal bones; subchondral bone thickness was consistently larger at dorsal compared with palmar sites in the proximal row of carpal bones. The endosteal surface of the subchondral bone was smooth. The shape of the ulnar carpal bone was variable and one or more small osseous fragments were identified palmar to the bone in 5/30 limbs. There was no evidence to suggest that these were pathological fractures or avulsions of the lateral palmar intercarpal ligament. The amount of muscle tissue in the superficial and deep digital flexor tendons in the proximal aspect of the carpus varied, but none was present at the level of the middle carpal joint and distally. Several structures could be evaluated that cannot be imaged using radiography, ultrasonography, or arthroscopy, including the transverse intercarpal ligaments, the radiocarpal ligament, the short palmar carpal ligaments, and the carpometacarpal ligaments. Anatomical variations not previously described were identified, including the layers of the medial aspect of the carpal fascia. Knowledge of the variation in MRI appearance of the carpus of nonlame horses is helpful for interpretation of MR images of lame horses.     

Palmar carpal osteochondral fragments in racehorses: 31 cases (1994-2004)

OBJECTIVE: To evaluate records of racehorses with palmar carpal osteochondral fragments and determine whether the fragments were indicators of the severity of pathologic joint changes or prognosis. DESIGN: Retrospective case series. ANIMALS: 31 racehorses. PROCEDURES: Medical records, radiographs, and videos of arthroscopic procedures were reviewed. Information gathered included signalment; location, number, and size of the primary lesion; number and size of palmar carpal fragments; and details pertaining to surgical procedures. Outcome variables were obtained from race records. RESULTS: 31 horses met the selection criteria. Multiple palmar fragments were diagnosed in 58% of horses; small fragments (< 3 mm in diameter) were most common (52% of horses). Fifty-two percent of the horses returned to racing, 48% returned to racing and earned money, and 32% had at least 5 more starts. Horses with multiple fragments had significantly less earnings per start and lower performance index values after surgery than those with 1 fragment. Horses with palmar fragments < 3 mm in diameter were significantly less likely to return to racing and have 5 starts or to win money after surgery than horses with larger fragments. CONCLUSIONS AND CLINICAL RELEVANCE: Palmar carpal osteochondral fragments can be used as an indicator of clinically important joint pathology and as a prognostic indicator in racehorses. Horses with multiple small fragments were less likely to successfully return to racing than horses with only dorsally located carpal fragments or horses with 1 or 2 large palmar fragments. When possible, removal of palmar carpal osteochondral fragments should be considered.     

Tearing of the medial palmar intercarpal ligament in the equine midcarpal joint.

Tearing of the medial palmar intercarpal ligament is described in 45 intercarpal (midcarpal) joints in 42 horses (37 racehorses, 5 non-racehorses). Of the 37 racehorses, there were 20 Quarter Horses, 14 Thoroughbreds and 3 Standardbreds. The patients had been referred for arthroscopic surgery for removal of osteochondral chip fragments that had been diagnosed radiographically or diagnostic arthroscopy of a persistent carpal problem. The problem was unilateral in 39 horses and bilateral in 3. The presenting clinical signs were lameness and/or persistent synovial effusion. In one instance, the presenting complaint was haemarthrosis. Osteochondral chip fragments were present in the joint affected with tearing in 23 horses. In 6 horses in which osteochondral fragments were present in other joints, the degree of synovial effusion was greatest in the midcarpal joint with ligamentous tearing. In most of the 22 midcarpal joints where carpal chip fragmentation and ligamentous tearing were present concomitantly, the degree of clinical compromise was greater than normally seen with that degree of osteochondral fragmentation. A ligament was designated as torn when a defect was present in the ligament. This usually took the form of frayed fibres suspended in the irrigating solution, presenting a transverse type of defect in the dorsal aspect of the lateral portion of ligament. However, longitudinal tearing was present in 1 case and tearing was noted in the palmar aspect of the ligament in 2 other cases. The shredded fibres were trimmed in most cases and this allowed better definition of the amount of ligament considered to be torn. The degree of damage ranged from 10% to 100% of the width considered to be torn.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Accuracy of Arthroscopic Identification of Equine Carpal Lesions

The equine carpal joint was used to evaluate arthroscopic diagnosis of lesions created in joints obtained from horses euthanized for reasons other than lameness. Full-thickness articular defects were made in 13 sites within the antebrachiocarpal joint and middle carpal joint approximating those found in diseased carpal joints. Arthroscopic evaluation of the lesions included location, depth, and size of the defects. The joints were subsequently examined grossly. Results showed that, when compared to gross evaluation, arthroscopy is capable of accurately identifying subtle changes in articular cartilage and bone. A statistically significant increase in error rate was found for lesions at the medial aspect of the proximal radial carpal bone. Other sites with limited arthroscopic access were the proximal ulnar carpal bone, the proximal fourth carpal bone, and the distal intermediate carpal bone. The accuracy of arthroscopic identification of lesions improved significantly during the study as experience with the technique was gained.     

Low‐field magnetic resonance imaging of keratomas of the hoof wall

Standing low‐field magnetic resonance imaging (MRI) was used to image the feet of 21 horses affected by keratomas. The animals had variable clinical histories including acute, chronic or recurrent lameness. Of the 21 horses, only 14 (66%) had radiological changes suggestive of keratoma. Standing low‐field MRI revealed a smoothly demarcated hoof wall lesion in all horses, with deformity of the adjacent surface of the distal phalanx in 15 cases. The signal characteristics of the keratomas varied, with most showing either hypointensity or heterogeneous mixed signal intensity in T1‐ and T2*‐weighted images and hypointensity in STIR sequences. An intermediate or high STIR signal intensity was present in the trabecular bone of the adjacent region of the distal phalanx in 5 cases. Surgical debridement was performed in 16 horses. Recurrence was common, especially in cases where the lesion was ill‐defined; the prior MRI appearance of these cases tended to be of heterogeneous signal intensity.     

Fractures of the carpus in racing thoroughbreds of the Japan Racing Association: Prevalence, location, and current modes of surgical therapy

From 1985 through 1994 approximately 39,800 Thoroughbred horses competed in over 3,400 races each year conducted by the Japan Racing Association (JRA). During this time the prevalence of fractures incurred during racing was 1.99, and 0.09% during training. Of these, 0.32% of the horses during racing died or were humanely destroyed as a direct result of their injuries. During 1994, 1,837 fractures occurred. The cuboidal bones of the carpus and the distal end of the radius accounted for 33.5% of all recorded fractures, with 47.4% of these occurring during racing and 24.2% occurring during training. The most common sites of fracture within the carpus were the distal end of the radius, the third carpal bone, and the radial carpal bone accounting for 35.3, 35.2, and 29.5% of fractures, respectively. Of these, 86/7% of osteochondral fractures occurred on the dorsal aspect of the cuboidal bones. At racing speed, characteristic fractures of the carpus are relatively common in race horses.Since 1991 in Japan, arthroscopic surgery has been the treatment of choice for the removal of carpal joint osteochondral fragments. Of all horses having arthroscopic surgery (n=155), 68.4% of these horses returned to race 9 months after surgery. Of all horses having osteochondral fractures of the distal end of the radius, radial carpal, and third carpal bones treated with arthroscopic surgery in 1993 (n=97) 52.6%, 60.0%, and 55.6% respectively, returned to race and competed at the same level of competition or higher compared with pre-operative racing performance. Arthroscopic surgery, as adapted by the JRA, is a useful technique for the treatment of carpal bone fractures in race horses; however, following surgery some horses had chronic arthritic changes associated with the surgical site. This suggests that the surgical methods and post-operative training program have to be re-evaluated.The objectives of this paper are to describe the prevalence, location, post-operative complication and racing performance for horses having cuboidal carpal bone fractures in racing Throughbreds of JRA.     

Effects of continuous intra-articular infusion of gentamicin on synovial membrane and articular cartilage in the tarsocrural joint of horses

OBJECTIVE: To determine the effects of a continuous intra-articular infusion of gentamicin on the synovial membrane and articular cartilage in the tarsocrural joint of horses. ANIMALS: 6 healthy adult horses. PROCEDURE: A balloon infusion system attached to a catheter placed in the plantarolateral pouch of both tarsocrural joints in each horse was used for continuous gentamicin solution (GM) or balanced electrolyte solution (BES) delivery for 5 days. Cartilage and synovial membrane specimens were collected on day 5 from 3 horses and on day 14 from the remaining 3 horses. Both infused joints from each horse were assessed, using gross evaluation and histologic scoring systems. RESULTS: Significant differences in the histologic scores of synovial membrane specimens between the GM- and BES-treated joints at either 5 or 14 days were not observed. Safranin-O-fast green staining scores were similar between cartilage specimens from GM- and BES-treated joints. Although the synovial membrane histologic scores and safranin-O-fast green staining scores improved from day 5 to 14, the changes in scores were not significant. Loss of synovial intimal cells from villi was found more commonly in sections of synovial membrane from GM-treated joints, compared with BES-treated joints. CONCLUSIONS AND CLINICAL RELEVANCE: Continuous infusion of GM into the tarsocrural joint of horses does not have significant effects on histologic scores of articular cartilage or synovial membrane, compared with those infused with BES. Continuous infusion of GM into the tarsocrural joint of horses for 5 days is an acceptable method for the treatment of septic arthritis.     

Frequency distribution of carpal osteochondral fragmentation in a population of flat racing Thoroughbreds in the UK

Lameness associated with osteochondral fragmentation of the carpus is a common injury in racing horses. Frequency distributions of sites of fragmentation have previously been published in racehorses in the USA, Australia, New Zealand and Japan but not in racing Thoroughbreds in the UK. The objectives of the study were to document sites of osteochondral fragmentation in the carpus of a population of Thoroughbred flat racehorses in the UK and compare these with other Thoroughbred populations globally and other flat racing breeds. This study was a single centre retrospective observational study; case records of flat racing Thoroughbreds with sites of carpal bone fragmentation that underwent arthroscopic surgery at Newmarket Equine Hospital between 2008 and 2013 were reviewed. A total of 291 sites of fragmentation were identified arthroscopically within the carpal joints of 174 horses. This involved 135 (75%) middle carpal (MCj) and 44 (25%) antebrachiocarpal joints (ABCj), which differs from other populations reported. The most common sites of fragmentation were dorsodistal radial carpal bone (DDiCr) (49%), dorsoproximal third carpal bone (DPrC3) (22%), dorsodistal radius (DDiR) (15%), dorsoproximal radial carpal bone (DPrCr) (5%) and dorsoproximal intermediate carpal bone (DPrCi) (4%). The dorsodistal radial carpal bone is also the most common site in American (US) Quarter Horses (QHs) and Thoroughbreds (TBs) and Australian (AUS) TBs, while DPrC3 has a greater prevalence in US Standardbreds (SBs). Thereafter the frequency distribution differs between the reported study groups. Although all horses underwent bilateral radiographic examination, 45% of the total population had unilateral arthroscopic evaluation. This may therefore underestimate the total number of sites of fragmentation reported. In summary the frequency distribution of carpal fragmentation in flat racing Thoroughbreds in the UK appears to differ from other populations of racehorses.