The Effects of Polysulphated Glycosaminoglycan on the Healing of Collagenase Induced Tendinitis

Objective. To examine the effects of polysulphated glycosaminoglycan on tendon healing in a controlled collagenase injury model. Design. The study used a completely randomized design with four horses assigned to each of two groups, control and treated. The superficial digital flexor tendons from each horse were measured weekly by ultrasound techniques. The differences between groups were evaluated using t-statistics and trends summarized by simple linear regression. Animals. Eight horses (four Thoroughbreds and four Standardbreds) with normal superficial flexor tendons were divided into two groups of four. Group #1 control horses were not treated. Group #2 horses were treated with polysulphated glycosaminoglycans. Procedure. All of the horses had tendinitis induced in the superficial flexor tendon of both forelimbs by the injection of 4000 IU of collagenase. The treated group received 500 mg of polysulphated glycosaminoglycan (PSGAG) IM every five days for seven treatments beginning 24 h after injection of collagenase. The control group received saline at the same time periods. Ultrasound examination of each limb was performed on days 1, 3, 5, and 7 post-injection and weekly thereafter for eight weeks. An image analysis system was used to measure the proportion of tendon area damaged in mm2 on the recorded images, and these values were plotted over time. The horses were euthanatized at eight weeks and histological evaluation was performed on longitudinal sections of excised tendons. Results. The size of the tendon core defects created by the collagenase enzyme, represented as the proportion of area damaged, decreased significantly faster in the treatment group (ρ <0.01). Histologic evaluation of the core defects confirmed what was seen sonographically. Conclusion. Polysulphated glycosaminoglycans had a positive effect on tendon healing in a collagenase induced tendinitis model. Clinical relevance. Polysulphated glycosaminoglycans may be beneficial in managing clinical cases of tendinitis.

Eight horses had experimental core defects induced in the superficial digital flexor tendon of both forelimbs. One group of four horses received PSGAG IM every 5 days for seven treatments. The control group received saline. The core defects in the PSGAG treatment group developed echogenic ultrasound patterns earlier, and the mean ratio of area of the tendon decreased significantly faster in the treatment group.

Multiple Cartilaginous Exostoses in a Cat

A 2-year-old neutered male cat with idiopathic hemolytic anemia had cartilaginous exostoses on the ribs, sternum, vertebrae and scapulae. The range of lesions in the cat resembled that reported in the dog. Radiographic and histologic appearances of the cartilaginous exostoses were like those reported for other species. Theories of the pathogenesis of this disease are presented. Electron microscopic examination of two widely separated cartilage-capped exostoses showed ‘C'-type viral particles resembling those of feline leukemia to be associated with the plasma membrane of chondroblastic elements.

Multipotential Osteosarcoma with Various Mesenchymal Differentiations in a Young Dog

Apparently synchronous, aggressive, mixed mesenchymal tumors in the right tibia, right femur, left femur, and rib cage produced multiple microscopic metastases in the lungs and macroscopic metastases in the liver, kidney, and spleen in a 1.5-year-old, neutered male, mixed-breed dog. No primary soft tissue tumor mass was present. Microscopically, the neoplasm exhibited osteosarcomatous, chondrosarcomatous, liposarcomatous, leiomyosarcomatous, fibrosarcomatous, angiosarcomatous, and leukocytic differentiation and was diagnosed as a multipotential osteosarcoma with various mesenchymal differentiation. Immunohistochemically, the neoplasm was cytoplasmically immunoreactive for vimentin, osteonectin, osteocalcin, CD 18, CD 31, desmin, and muscle-specific actin. Oil Red O staining was positive within liposarcomatous areas. Skeletal metastases from a primary bone tumor are exceedingly rare in human and veterinary medicine. However, the history, clinical signs, location, microscopic and immunohistochemical features were similar to those described in aggressive, poorly differentiated osteosarcomas of children. In addition, the wide range of mesenchymal tissue differentiation of this neoplasm was unusual, and to the authors' knowledge, an osteosarcoma with this degree of multiple differentiation has not been previously reported in the dog.

Arthroscopic treatment of meniscal cysts in the horse

REASONS FOR PERFORMING STUDY

To describe the clinical symptoms, treatment, and outcome of meniscal cysts in horses. These structures have not been previously described in the literature as a potential cause of lameness in the horse.

HYPOTHESIS

Meniscal cysts are an uncommon condition of the femorotibial joint but can be a significant cause of lameness. Symptoms can be resolved by arthroscopic excision.

METHODS

Records of horses diagnosed with meniscal cysts and treated by cyst excision and meniscal debridement at 2 surgical practices were reviewed. Clinical outcome was determined by repeat veterinary examination and contact with owner.

RESULTS

Seven cases of meniscal cyst were treated with arthroscopic cyst excision and meniscal debridement. Five of 7 horses had lameness attributable to femorotibial joint pathology, while the remaining 2 horses had meniscal cysts found incidentally during diagnostic arthroscopy for the treatment of osteochondritis dissecans of the lateral trochlear ridge of the femur. Five of 6 horses with long-term follow-up were sound and a 7th horse was improved 11 months after surgery.

CONCLUSIONS AND POTENTIAL RELEVANCE

Meniscal cysts, while uncommon, can be associated with progressive lameness in the horse. Surgical excision of the cysts results in resolution or improvement of symptoms, without evidence of recurrence on follow-up examination.

Strontium-90 Induced Bone Tumours in Beagle Dogs: Effects of Route of Exposure and Dose Rate

Bone tumours from beagles exposed by inhalation to 90SrCl2 at the Inhalation Toxicology Research Institute (ITRI), by chronic ingestion of 90Sr at the Laboratory of Energy-Related Health Research (LEHR), and by injection of 90Sr citrate at the University of Utah were analysed to determine if the bone tumour characteristics differed among the three studies. The range of average skeletal doses at which the bone tumours occurred was similar in all three studies, but differences in the skeletal distribution, histological phenotype, and time to death were observed. The differences observed were attributed to the difference in dose-rate pattern obtained in the chronic ingestion study, in contrast to the inhalation and injection studies. In general, however, the differences noted in bone tumour characteristics were subtle, and would be unlikely to make an impact on models developed to assess the risk of human exposure to 90Sr.

Mandibular Ossifying Fibroma in a Dog

An aged mongrel dog was admitted for hemimandibulectomy as treatment for a mandibular mass that had been diagnosed as osteosarcoma. The fibro-osseous mass that surrounded the first molar tooth and replaced alveolar and cortical bone was reclassified as ossifying fibroma on the basis of anatomic location and histologic features. The tumor was composed of isomorphic fusiform cells with few mitotic figures. Tumoral stroma contained trabeculae of woven bone that were bordered by a single layer of osteoblasts. Excision was deemed complete with no evidence of extension or metastasis by computed tomography of the skull or thoracic and abdominal radiography. The dog was reportedly healthy 6 months after initial presentation. Though far less common than osteosarcoma as a primary canine bone tumor, ossifying fibroma should be included in the differential diagnosis for fibro-osseous proliferations, especially those of the jaw. Although benign, en bloc excision may be necessary for surgical cure.

Synovial hemangioma in the stifle joint of a dog

Synovial hemangioma was diagnosed in an 8-year-old castrated male Belgian Sheepdog with lameness of 3 months' duration. Pain, soft-tissue swelling, and hemarthrosis were localized to the left stifle joint. Projections of synovial membrane with reddish-purple nodules, excised via arthrotomy, were composed histologically of variably sized vascular channels that were lined by well-differentiated endothelial cells and separated by fibrous septa. Distension of some channels resulted in endothelial disruption, thrombosis, hemorrhage, necrosis, and focal spindle-cell proliferation. The limb was amputated to remove remaining neoplastic tissue. The hemangioma extended focally into the joint capsule and popliteal soft tissue but did not invade skeletal muscle or bone. The dog was free of detectable neoplasia 6 months after amputation. Synovial hemangioma is a rare benign vascular proliferation in people, most commonly in the knee, and should be included in the differential diagnosis for canine synovial tumors.

Effect of maturation and aging on the histomorphometric and biochemical characteristics of equine superficial digital flexor tendon

OBJECTIVE

To assess tendon morphology and non-reducible crosslink concentration, and associations of these findings with horse age and previously reported mechanical and ultrasonographic findings.

SAMPLE POPULATION

Superficial digital flexor tendon samples were obtained from 23 horses aged 2 to 23 years. The tendons had undergone ultrasonography and were submitted to biomechanical testing in the physiologic range prior to sample acquisition.

PROCEDURE

Samples were sectioned in a transverse plane; then dorsal, palmar, central, lateral, and medial regions were evaluated for fascicle cross-sectional area (CSA), septal width, and vessel density (the product of vessel numbers and vessel CSA per field). Contiguous samples were analyzed for collagen crosslinking.

RESULTS

Central fascicles were significantly larger than fascicles in other tendon regions. Fascicle CSA decreased significantly with increasing age. Because total tendon CSA is unrelated to increasing age, fascicle numbers appeared to increase with increasing age. Regional or age effects on septal width were not found. There was no age or regional effect on vessel numbers, density, or fractional area. Fascicle CSA was positively correlated with total tendon CSA; fascicle CSA was negatively correlated with elastic modulus. Hydroxypiridinium concentration tended to increase with increasing horse age; this effect was associated with a positive correlation between hydroxypiridinium values and elastic modulus.

CONCLUSIONS

Equine superficial digital flexor tendon undergoes an increase in structural organization and an increase in nonreducible crosslinks with maturation and aging. These changes are associated with an increase in elastic modulus.

Cervical and thoracic vertebral malformation ("weak neck") in Colombia lambs

The purpose of this study is to describe a developmental defect of the caudal cervical and cranial thoracic vertebrae in 11 purebred Colombia lambs. The lambs were either affected at birth, or developed the condition within the first 18 days of age. Cervicothoracic kyphosis, with a compensatory cervical lordosis and ataxia were common; 8 lambs had abnormal head posture, characterized by inability to lift the head from the ground. One lamb had rigid head and neck, and had to move the entire body to look to the left or right. Neurological signs included ataxia, tetraparesis, diminished conscious proprioception, and increased patellar and triceps reflexes. One lamb had inspiratory stridor because of compression of the trachea in the area overlying the abnormal vertebrae (cervical vertebrae 6 [C6] and 7 [C7]). Radiographic and pathological abnormalities included malalignment and malarticulation of the caudal cervical and cranial thoracic spine, rounded cranioventral margins in the bodies of vertebrae C7 and T1, wedging of the intervertebral disc spaces between C6 and T1 vertebrae, and hypoplasia of the dens. Pathological changes in the soft tissues included hypoplasia of the cervical epaxial and hypaxial musculature, with associated focal areas of myodegeneration. Mild Wallerian axonal degeneration, compatible with a mild cord compression syndrome, was found in 3 lambs in the cervicothoracic spinal cord adjacent to the vertebral anomalies. The concentrations of copper and selenium in blood, plasma, or tissues were normal in 10 of 11 lambs. All but one of the lambs in which pedigree information was provided were genetically related. Siblings born as twins to 5 of the affected lambs were normal, but both lambs from one twin pregnancy were affected. Owners reported that breeding stock had been shared among the ranches. Because of the close familial relationships of the affected lambs, the condition is suspected to have a hereditary basis.

Histologic appearance of axial osteochondral fragments from the proximoplantar/proximopalmar aspect of the proximal phalanx in horses

Osteochondral fragments from the axial proximoplantar/proximopalmar region of the proximal phalanx were removed from 38 joints in 30 horses. Ninety-three percent of the horses were Standardbreds, and 28 of the 30 had a low-grade lameness. All but 1 of the horses had hind limb involvement. A total of 43 fragments were removed. Most (71%) of the fragments involved the medial aspect of the joint and had to be dissected from a covering of synovial tissue. Histologically, the circumference of most fragments consisted of a transition zone at the attachment of the joint capsule, a region of nonarticular, non-weight-bearing cartilage, a region where organized, dense connective tissue, presumably remnants of the short sesamoidean ligament were attached, and a region consisting of irregular truncated bony surfaces covered by healing of chronic fracture. There were several areas of degenerate hyaline cartilage, but no areas of normal hyaline cartilage or areas containing related cartilage cores or other evidence of delayed endochondral ossification. Immunohistochemical staining of 4 segments from 1 horse revealed sensory substance P immunoreactive nerves in the fibrous tissue surrounding the bony fragments and within the central cancellous spaces. The histologic appearance suggests that these osteochondral fragments may be a result of fracture, rather than a manifestation of osteochondrosis.

Effect of maturation and aging on material and ultrasonographic properties of equine superficial digital flexor tendon

Results of studies in human beings and other species have indicated that aging significantly influences the strength, modulus of elasticity, and energy storage ability of tendon. We wanted to determine the effects of aging on the material and ultrasonographic properties of equine superficial digital flexor (SDF) tendon. Ultrasonographic measurements of left forelimb SDF tendon cross-sectional area and mean echogenicity were made in 23 standing horses ranging in age from 2 to 23 years. All horses had not been in work for a minimum of 6 months prior to the study. After euthanasia, left forelimb bone-muscle-tendon-bone specimens were mounted in a materials testing system. The SDF tendon was cyclically loaded sinusoidally 100 times at 0.5 Hz from 1.5 to 5.0% strain, then was submitted to 10-minute creep-and-stress relaxation tests. Modulus of elasticity, load at 3% strain, and creep-and-stress relaxation were determined for each specimen. A significant positive correlation was found between elastic modulus and age. Correlation was not found between age and SDF tendon cross-sectional area or mean echogenicity. When 2-year-old horses were compared with older horses, the latter had tendons with a significantly (P = 0.007) greater modulus of elasticity. The authors conclude that increasing age through maturity is associated with a corresponding increase in equine SDF tendon elastic modulus.

Ultrasonography as a method to determine tendon cross-sectional area

Ultrasonographic cross sectional area (CSA) measurements of equine superficial digital flexor (SDF) tendon were obtained to determine the feasibility of ultrasonography for CSA measurement of tendon in vivo and in vitro. Ultrasonographic measurements were compared with a more traditional CSA measurement method, ink-blot analysis. In addition, values for ultrasonographic SDF tendon mean echogenicity were obtained in vivo and in vitro. The left forelimb SDF tendons of 23 horses were evaluated ultrasonographically. Cross sectional images were acquired at 4-cm intervals distal to the base of the accessory carpal bone (DACB) to the level of the proximal sesamoid bones while horses were standing squarely. After euthanasia, the left forelimbs were mounted in a materials testing system (MTS) and loaded under tension to standing load. Ultrasonographic images were again acquired at the same locations. The ultrasonographic images were digitized, and values for ultrasonographic CSA and mean echogenicity were obtained for each level. immediately after mechanical testing, a 1-cm-thick transverse section of SDF tendon at 12 cm DACB was removed. Three ink blots were prepared from each end of the removed tendon section and digitized. The 6 CSA values were averaged to generate a value for morphologic CSA for each SDF tendon at 12 cm DACB. Standing ultrasonographic tendon CSA at 12 cm DACB was consistently smallest (mean +/- SD CSA 86 +/- 11 mm2), followed by MTS ultrasonographic CSA (mean, 95 +/- 12 mm), with ink-blot morphologic CSA being largest (mean, 99 +/- 15 mm2). Comparison of standing and MTS ultrasonographic CSA values at 12 cm DACB revealed a strong positive linear correlation between methods (R2 = 0.74, P = 0.001). Comparison of ink blot CSA at 12 cm DACB with standing and MTS ultrasonographic CSA revealed strong positive linear correlations (R2 = 0.64, P = 0.001 and R2 = 0.72, P = 0.001, respectively). For ultrasonographic mean echogenicity, standing values insignificantly exceeded MTS values at each level. The authors conclude that ultrasonography is a useful technique for the noninvasive assessment of SDF tendon CSA that can be applied in vivo and in vitro.

Resolution of lameness associated with Scottish fold osteodystrophy following bilateral ostectomies and pantarsal arthrodeses: a case report

Bilateral hind-limb lameness, associated with tarsal exostoses in a Scottish fold diagnosed as having Scottish fold osteodystrophy, resolved following staged bilateral ostectomies and pantarsal arthrodeses. Degenerative changes in the phalangeal joints of the hind limbs have progressed radiographically, but lameness has not recurred 48 weeks following the second arthrodesis. Additional skeletal abnormalities were detected radiographically in both carpi and in several caudal vertebrae. A partial, left-sided conduction deafness was diagnosed by evaluating brain stem auditory-evoked responses.

Multiple metaphyseal involvement of a thymic lymphoma associated with hypercalcemia in a puppy

A six-month-old, female German shepherd dog was presented because of depression, anorexia, vomiting, polyuria, and polydipsia of approximately 10 days' duration. The puppy was depressed, and pain could be elicited on palpation of both shoulders and hips. The most significant results of serum chemistries and hematology were hypercalcemia; increased blood urea nitrogen, creatinine, and alkaline phosphatase; and leukocytosis with neutrophilia. Thoracic radiographs revealed a large thymic mass, diagnosed on histological examination as a thymic lymphoma. Radiographs of the shoulders revealed destructive bone lesions involving the proximal metaphyses of the humeri, causing slipped epiphyses. Bone lesions were found at necropsy on the proximal and distal aspects of both humeri and femurs. Bone resorption was due to local neoplastic infiltration and presumed humoral factors secreted locally and systemically by neoplastic thymic lymphocytes.

Ultrasonographically detected changes in equine superficial digital flexor tendons during the first months of race training

The forelimb superficial digital flexor (SDF) tendons of 6 Thoroughbreds were examined clinically and ultrasonographically during the first 4 months of race training. Sonograms were interpreted clinically and by use of computer-aided analysis. Tendon tissue from all horses was examined histologically at the end of the study. Computer-aided analysis of sonograms of the SDF tendons revealed trends toward an increase in mean cross-sectional area and a decrease in mean echogenicity over time with training. An inverse relation was found between increase in cross-sectional area and decrease in mean echogenicity over time in training. Two of the trained horses developed clinical signs of mild SDF tendonitis. Ultrasonography revealed an increase in cross-sectional area and decrease in mean echogenicity of clinically affected areas of the SDF tendons of 1 horse, compared with changes observed prior to the onset of tendonitis (these changes were not statistically significant). Blood vessels and lymphatics supplying the clinically and ultrasonographically affected tendon sites were large and thick-walled. These changes were not observed in the tendons of the other horses at the end of the study. The authors conclude that equine SDF tendons adapt to the early months of race training by increasing in size and decreasing in echogenicity, as determined by ultrasonography.

Characterisation of osseous bodies of the distal phalanx of foals

The distal phalanx and metacarpal physis of both forelimbs of 32 Thoroughbred foals 3-32 weeks of age were radiographed to identify those limbs with osseous bodies at a palmar process (PP) of the distal phalanx. Osseous bodies (ossicles) were identified radiographically in 19% of the foals. Sixteen of the 32 foals were selected for microradiographic and histological evaluation: 6 foals with radiographic evidence of ossicles and 10 foals without. Fourteen ossicles of the PP were observed radiographically. Ossicles were either a triangular bone fragment at the palmar aspect of the distal angle of the PP, or an oblong bone fragment separated from P3 by a radiolucent line extending 1-3 cm from the incisure of the PP to the solar margin. One foal had radiographic evidence of bilateral distal metacarpal physitis. Seventeen of 35 PPs examined microradiographically were considered normal, in that the dorsal and solar cortices were thin with trabecular bone orientated parallel to the cortical surfaces, and there was a depression in the dorsal cortical surface (i.e. parietal sulcus). Abnormal microradiographic findings in the other 18 PPs included a fracture line extending from the dorsal cortical surfaces and trabecular bridging of the fracture gap. The fracture line was often continuous with the parietal sulcus. Microradiographic evidence of a fracture was found in 75% of foals evaluated. Normal histological findings in 16 PPs included thin dorsal and solar cortices with trabeculae orientated parallel to the cortical surfaces, parallel-fibred dense connective tissue attachments of the deep digital flexor tendon to the solar cortical surfaces, and a neurovascular bundle associated with the parietal sulcus.(ABSTRACT TRUNCATED AT 250 WORDS)

Histological features of the dorsal cortex of the third metacarpal bone mid-diaphysis during postnatal growth in thoroughbred horses

The dorsal cortex of the equine third metacarpal mid-diaphyseal bone was characterised during growth by the histological and microradiographic examination of specimens from 30 horses ranging in age from 2 months to 8 y. Bone from horses aged less than 6 months was characterised by rapid periosteal apposition of circumferential trabeculae of woven bone that were next connected by radial trabeculae to the parent cortex. Deposition of lamellar bone on the inner trabecular surfaces resulted in rows of primary osteons. Replacement of primary bone occurred only after 4 months of age and preferentially in the woven interstitial bone separating rows of primary osteons formed in the postnatal periosteal cortex. Resorption cavities and incompletely filled secondary osteons characterised bone of 1 and 2-y-old horses. Bone from horses older than 3 y contained several generations of secondary osteons, fewer resorption spaces and incompletely filled osteons, and had a greater portion of circumferentially oriented collagen fibres than bone from younger horses. Bone from horses older than 5 y had large resorption cavities characterised by irregular boundaries. We propose that the process of periosteal bone tissue apposition observed in growing foals be called 'saltatory primary osteonal bone formation' and that this process results in faster cortical expansion and larger total surface area for bone deposition than circumferential lamellar, simple primary osteonal, and plexiform mechanisms of periosteal bone formation. We speculate that bone from 1 and 2-y-old horses would be more susceptible to fatigue microdamage resulting from compressive loads because of high porosity, few completed secondary osteons and low proportion of circumferentially oriented collagen fibres.

Radiographic/morphologic investigation of a radiolucent crescent within the flexor central eminence of the navicular bone in thoroughbreds

The source of a previously described radiolucent crescent in the flexor cortex of the distal sesamoid (navicular) bone on the palmaro45 degrees proximal-palmarodistal oblique (Pa45 degrees Pr-PaDio) clinical radiographic projection was investigated in 48 forelimb navicular bones from 24 Thoroughbreds by use of high-detail radiography and x-ray computed tomography (CT). Twenty-five of these bones also were evaluated, using microradiography and histologic examinations. Of these 25 bones, 5 had been labeled in vivo with fluorochrome markers. Tetrachrome-stained 100-microns-thick nondecalcified sections of these 5 bones were examined, using epifluorescence microscopy. A reinforcement line of compacted cancellous bone, parallel and several millimeters deep to the flexor cortex in the region of the flexor central eminence, was visualized by CT in 42 of 48 navicular bones and by microradiography in 23 of 25 navicular bones investigated. Variable degrees of compaction were observed in the cancellous bone between the flexor cortex and the reinforcement line. High-detail skyline radiographic projections and reconstructed CT images indicated a crescent-shaped lucency within the flexor central eminence of the flexor cortex in the bones in which the reinforcement line was identified, but the cancellous bone between the reinforcement line and the flexor cortex had not been compacted. The radiolucent crescent seen in the flexor central eminence of the navicular bone on the Pa45 degrees Pr-PaDiO projection was not caused by the concave defect or synovial fossa of the flexor central eminence overlying the flexor cortex, as was described.(ABSTRACT TRUNCATED AT 250 WORDS)

Corticocancellous bone biopsy from the 12th rib of standing horses

Unicortical corticocancellous bone biopsy specimens 4.5 mm and 6.5 mm in diameter were obtained without long-term complications from the 12th rib in eight standing horses. However, the bone specimens were unsuitable for histologic or histomorphometric evaluation. In in vitro comparisons of biopsy specimens 6.5 mm and 12 mm in diameter, and of unicortical and transcortical biopsy specimens, 12 mm transcortical specimens yielded the most cancellous bone. Transcortical bone biopsy specimens 12 mm in diameter were obtained from eight horses by using power-assisted trephination. The surgical procedure was well tolerated, but some degree of pneumothorax in all horses was treated by aspiration of air from the thorax. Long-term complications were not observed.

Radiographic, high detail radiographic, microangiographic and histological findings of the distal portion of the tarsus in weanling, young and adult horses

Clinical radiographic (LM and D35L-P1MO views), high detail radiographic, microangiographic and histological findings of the distal portion of the tarsus of 16 horses (five weanling, four young and six adult), without known clinical histories, were evaluated to determine the sensitivity of clinical radiographs for the detection of abnormalities in the distal tarsus and the prevalence of abnormalities in this population. Clinical radiographic and high detail radiographic abnormalities were observed in at least 30 per cent of the tarsi examined. Statistical agreement between observations from clinical radiographs and corresponding post mortem high detail radiographs was not good for subchondral bone plate irregularities and joint margin changes. Three patterns of sclerosis of the medullary spongiosa were visualised on high detail radiographs: thickening of the subchondral bone plate was seen commonly in the weanling group, whereas arching and bridging patterns were more prevalent in the young and adult groups. Bone production on the dorsal cortex of the central and third tarsal bones did not increase with age. Abnormalities in vascular perfusion and articular cartilage histology were observed in association with subchondral bone plate irregularities and focal regions of osteopenia observed on high detail radiographs.

Osteomyelitis of the axial border of the proximal sesamoid bones in seven horses

Destructive lesions of the axial region of the proximal sesamoid bones were identified by radiography in eight fetlocks and seven lame adult horses. Lameness ranged from 2 to 5 (mean 4; scale 1 to 5) at the time of examination, with a duration of 10 days to two years (mean 5.6 months). Destructive lesions involved both proximal sesamoid bones when examined radiographically and were situated primarily at the level of the mid-body and apical region of the axial borders. Some lesions were cystic, whereas others eroded the axial border more diffusely. Scintigraphy revealed markedly increased activity within the proximal sesamoid bones of the clinically lame limb of four of the five horses examined. In four horses, post mortem computed tomography revealed axial border bone destruction and cavitary lesions within cancellous bone of affected proximal sesamoid bones. Lesions seen by computed tomography were larger than those identified on radiographic examination. Cavitary lesions not seen radiographically were identified in the proximal sesamoid bones of two clinically unaffected fetlocks examined for comparison in two of the seven horses. Evidence of acute, subacute or chronic/reparative osteomyelitis of the axial region of the proximal sesamoid bones was seen in the 10 fetlocks identified as abnormal from radiography or computed tomography. Also, three horses had septic synovitis of the flexor sheath of the clinically affected limb; of these, two had septic arthritis of the fetlock joint.

Squamous cell carcinoma of the hoof wall in a stallion

Squamous cell carcinoma of the hoof wall, with resultant invasion of the right hind distal phalanx, was identified in a 15-year-old Thoroughbred stallion. The clinical features included a chronic grade 2/5 right hind limb lameness and a sessile dorsal hoof wall mass that was not sensitive to palpation. Radiography revealed a well-circumscribed circular lucency within the distal phalanx, beneath the clinically noticed hoof wall mass. These features were considered to be characteristic of a hoof wall keratoma. Surgical intervention was done 10 months later. The histologic diagnosis at the time of surgery was squamous cell carcinoma. Eight months after surgery, progressive tumor invasion of the distal phalanx resulted in a pathologic articular fracture. This case highlights the need for accurate histologic diagnosis of equine hoof wall masses to differentiate between benign and malignant conditions.

Osteochondrosis of the lateral trochlear ridge of the talus in seven Rottweiler dogs

Eleven lesions of osteochondrosis in the lateral trochlear ridge of the talus were diagnosed in seven young Rottweiler dogs. Diagnosis was based on clinical and radiographic evaluations. Defects in the lateral trochlear ridge and osteochondral fragments arising from the dorsal and proximal margins of the ridge were visible radiographically. The dorsal 45 degrees lateral-plantaromedial oblique (D45 degrees L-P1MO) projection was the most useful in identifying the lesions. Exploratory arthrotomies were performed in six affected tarsi. In three cases, histologic examination revealed mineralized osteochondral fragments consistent with a diagnosis of osteochondrosis.

Pathologic findings and pathogenesis of racetrack injuries

Many lesions of the musculoskeletal system of racing horses are either acute traumatic lesions or are chronic biomechanically induced lesions that become suddenly unstable and provoke acute clinical signs. The latter lesions along with those of DJD are much more common and are of much greater overall economic importance to the racing industry than are the acute traumatic injuries. Chronic biomechanical lesions occur at predictable sites and are the result of an imbalance between repetitive microtrauma sustained in athletic performance and adaptive repair mechanisms of skeletal tissues. The distribution of these lesions in the limbs reflects the patterns of biomechanical forces placed on the skeleton during work at racing speeds and, therefore, reflects the type of racing activity for which the horse was bred. Lesions result when there is a failure of the stressed skeletal structures to adapt to the biomechanical forces placed upon them. Rest or a reduction in the level of training activity permit the healing of many asymptomatic and presumably some symptomatic lesions of the bony tissues. Articular cartilage, tendons, and ligaments have a lower capacity to resolve the damage and return to normal structure and function.

Evaluation of an interfragmentary compression system for the repair of equine femoral capital physeal fractures

Femoral neck and proximal epiphyseal lengths were measured in 37 femurs from 19 cadaver foals that were 1 day to 12 months old to determine the applicability of a human interfragmentary compression system to equine femoral capital physeal fractures. Because components of the implant system are available only in fixed sizes, its use was possible in foals older than 5 weeks of age, but not in younger foals. The 135 degree angle plate conformed best to the equine femur. Femoral capital physeal fractures were created surgically and repaired with the implant system in three foals. Fracture stability was evident clinically and radiographically in all three foals until euthanasia at month 3. At necropsy, the treated femurs were 4, 8, and 27 mm shorter than their mates. Epiphyseal viability was verified in all three foals by tetracycline deposition and new appositional bone growth comparable with that in the contralateral control epiphyses. The treated capital physis was open but reduced in thickness in one foal, disorganized in one foal, and closed in one foal. Fixation by compression with the implant system resulted in stability sufficient for fracture healing and maintenance of epiphyseal viability, although it was associated with reduced longitudinal femoral growth.

The fate of articular cartilage after transplantation of fresh and cryopreserved tissue-antigen-matched and mismatched osteochondral allografts in dogs

The long-term success of massive osteochondral allografts depends not only on the incorporation of the transplanted articular cartilage. Osteochondral allografts are immunogenic, and, once an immune response is stimulated by exposure to donor cellular antigens, the cartilage becomes vulnerable to direct injury by cytotoxic antibodies or by lymphocytes, or to indirect injury by inflammatory mediators and enzymes induced by the immune response. To clarify the role of histocompatibility antigen-matching on the health of transplanted articular cartilage, we orthotopically implanted canine leukocyte antigen-matched and mismatched proximal osteochondral allografts of the radius, both fresh and cryopreserved, in beagles. Four groups of dogs received: (1) canine leukocyte antigen-mismatched frozen allografts, (2) canine leukocyte antigen-mismatched fresh allografts, (3) canine leukocyte antigen-matched fresh allografts, or (4) canine leukocyte antigen-matched frozen allografts. In twelve of the dogs, the contralateral leg was subjected to a sham operation, and in ten of the dogs, the proximal part of the radius was removed and replaced as an autogenous graft control. All animals were followed for eleven months after the operation and then were killed. The cartilage of the grafts was evaluated grossly, histologically, and biochemically. The biochemical analysis consisted of measurement of dry weight, content of glycosaminoglycan and hydroxyproline, and galactosamine-to-glucosamine ratios. Analyses of variance were used to study the effect of tissue antigen-matching and freezing on degradation of cartilage. During the study, no dog had grossly obvious clinical abnormalities, all host-graft interfaces healed, and no joints dislocated. The gross appearance of the cartilage was normal for both the joints that had an autogenous graft and those that were subjected to the sham operation. The cartilage of all allografts was thinned, dull, and roughened. The synovial membrane of all of the joints that had been operated on was mildly fibrotic and hyperplastic, but only that of the dogs that had an allograft was severely fibrotic and hyperplastic and demonstrated an inflammatory response. The inflammatory response was most severe in joints that had received a fresh canine leukocyte antigen-mismatched allograft. Invasive pannus was more frequent in joints that had received a fresh graft, particularly those that had received a canine leukocyte antigen-mismatched allograft, and cartilage was sometimes eroded to subchondral bone. Freezing was harmful to the cartilage. Very few cells survived the freezing procedure, and frozen grafts received s significantly worse histological scores had significantly less glycosaminoglycans and had a lower ratio of galactosamine to glucosamine than fresh grafts.

Pathophysiology of navicular syndrome

Navicular syndrome is a degenerative disorder of the distal half of the flexor surface of the proximal sesamoid bone that is predisposed by faulty foot conformation. In horses that become symptomatic, the faulty conformation results in sustained application of nonphysiologic pressure by the deep digital flexor tendon against the flexor cortex of the bone. This force stimulates an intense bone remodeling response in order to attenuate the pressure. An unfortunate sequela of this response is active hyperemia and edema formation in the medullary cavity of the bone. The edema is organized by fibrous tissue resulting in venous entrapment, venous hypertension, vascular bone pain, and the onset of clinical signs.

A technique for catheterization of the equine antebrachiocarpal joint

A 2.5-cm long, 0.8 mm in diameter catheter was placed percutaneously into the palmarolateral pouch of the antebrachiocarpal joint in 6 clinically normal horses. The catheter was affixed in place for 72 hours. Cytologic analysis was performed on synovial fluid specimens obtained through the catheter at postcatheterization hours (PCH) 0, 24, and 72. The horses were euthanatized at PCH 72, and macroscopic and microscopic examinations were performed on the dorsal portion of the joint capsule and the palmarolateral pouch of the catheterized and contralateral (noncatheterized) joint. Clinical, synovial fluid cytologic, and synovial membrane histologic examinations were performed to assess the effect of the catheter on clinically normal equine synovial membrane. Serially obtained synovial fluid specimens were yellow and clear or hazy and had good mucinous precipitate quality at all times in all horses, except 2, in which the catheter required readjustment. Mean refractive index was slightly decreased, and the RBC count was high at PCH 24 and 72, compared with PCH 0; the highest RBC count was 12,550 cells/microliter (PCH 24). Statistically significant (P less than 0.05) increases were observed in WBC, neutrophil, and large and small mononuclear cell counts between PCH 0 and 72. These increases were modest, except the mean WBC count (51,000 cells/microliter, PCH 72) observed in 1 horse in which the catheter was dislodged, requiring reinsertion into the joint. At necropsy, subcutaneous hemorrhages were observed at the catheter insertion site in all horses. The synovial membrane of the catheterized joint was discolored (ranging from yellow-orange to salmon), compared with the contralateral synovium (noncatheterized joint).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of gentamicin sulfate and sodium bicarbonate on the synovium of clinically normal equine antebrachiocarpal joints

The effect of gentamicin sulfate, unbuffered and buffered with sodium bicarbonate, on synovial fluid and membrane of clinically normal equine joints was evaluated. Thirty-six adult horses with clinically normal antebrachiocarpal joints were allotted to 6 treatment groups of 6 horses each. One antebrachiocarpal joint in each horse was chosen for treatment. Group-1 horses were given gentamicin (3 ml; 50 mg/ml); group-2 horses were given sodium bicarbonate (3 ml; 1 mEq/ml); group-3 horses were given gentamicin (3 ml; 50 mg/ml) and sodium bicarbonate (3 ml; 1 mEq/ml); group-4 horses were not treated; and horses of groups 5 and 6 were given polyionic physiologic solution (3 and 6 ml, respectively). Synovial fluid specimens were obtained from 5 horses of each group for cytologic analysis at postinjection hours (PIH) 0, 24, 72, and 192 and for pH determination at PIH 0, 0.25, 0.5, 1, 4, 8, 24, 72, and 192. The sixth horse of each group was euthanatized at PIH 24, and the synovial membrane of the treated and contralateral (nontreated) antebrachiocarpal joints was examined macroscopically and microscopically. After intra-articular gentamicin administration, the mean synovial fluid pH was lowest (5.98) at PIH 0.25, but by PIH 8, it was not significantly different from the control value (group-5 horses). When sodium bicarbonate was combined with gentamicin before intra-articular administration, the mean synovial fluid pH was lowest (7.07) at PIH 0.25, but by PIH 1, it was not significantly different from the control value (group-6 horses).(ABSTRACT TRUNCATED AT 250 WORDS)

Primary degenerative joint disease of the shoulder in a colony of beagles

Shoulder joints of 149 Beagles over 8 years old at the time of death (mean age, 13.8 years +/- 3.21), were examined radiographically throughout their life-times for the frequency of degenerative joint disease (DJD). Clinical histories revealed no underlying cause for DJD. The shoulder joints of a subgroup of 18 dogs were examined at necropsy, and thin sections of the joints were evaluated radiographically and histologically. Serial clinical radiographic studies indicated that normal shoulder joint development during the first year of life was followed by the appearance of subchondral bone sclerosis and bony remodeling of normal joint contour, and by the formation of periarticular osteophytes and enthesiophytes. All changes were progressive with age and typical for DJD in dogs. Bilateral involvement was common. Evaluation of specimens obtained at necropsy revealed: articular cartilage change with roughening of the surface layer, degeneration and death of superficial chondrocytes, exposure of deeper layers of chondrocytes that had proliferated with fissuring of the damaged cartilage, total cartilage loss with polishing of the exposed subchondral bone, mixed patterns of subchondral bone sclerosis and osteoporosis, change in contour of the articular surfaces, and formation of periarticular osteophytes and enthesiophytes. Joint capsule thickening, synovitis, pannus formation, and synovial chondroma formation were observed. Because of the available clinical information, in addition to the typical changes of DJD, it was thought that the changes were primary. Instability appeared to play a role in the pathogenesis of the joint disease described; however, it was not clear whether the instability caused abnormal forces on healthy cartilage or whether the primary cartilage wear caused the instability.

Effect of intra-articular gentamicin sulfate on normal equine synovial membrane

Gentamicin sulfate (3 ml; 50 mg/ml) was administered intra-articularly into 30 normal equine radiocarpal joints after arthrocentesis. Arthrocentesis alone was performed on 10 normal radiocarpal joints. Synovial fluid evaluations and gross and microscopic examinations were performed on synovial fluid and synovial membrane of designated joints at selected daily intervals over a period of 10 days. Synovial fluid from gentamicin-injected joints had greater turbidity, higher RBC and WBC counts, and higher refractive indices than did joints not injected with gentamicin. The largest increases developed on days 1 or 2 after gentamicin injection, with mean total WBC, large mononuclear cell, small mononuclear cell, and polymorphonuclear cell counts of 23,860, 11,853, 857, and 11,150 cells/microliter, respectively. Arthrocentesis alone resulted in smaller increases in these counts. Microscopic changes seen in the synovial membrane of gentamicin-injected joints included edema, leukocytic infiltration, and loss of synovial lining cells. These inflammatory changes resolved within 7 days after gentamicin injection.

Correlative biomechanical and histologic study of the cranial cruciate ligament in dogs

The mechanical properties of the cranial cruciate ligament were determined, using unilateral bone-ligament-bone preparations from 65 dogs of various ages and body sizes. Tensile loading of the cranial cruciate ligament from 1 of each pair of stifle joints demonstrated a decrease in material properties (modulus, maximum stress, strain energy) with aging. The decreases in maximum stress and strain energy with age were significantly less (P less than 0.05 and P less than 0.05, respectively) in the cranial cruciate ligament from dogs weighing less than 15 kg, compared with those weighing 15 kg or more. The cranial cruciate ligament and remaining femorotibial ligaments were collected from the opposite stifle joints and examined microscopically. By 5 years of age, the cranial cruciate ligaments of dogs weighing greater than 15 kg consistently had microscopic evidence of degenerative disease (loss of ligamentocytes, metaplasia of surviving ligamentocytes to chondrocytes, and failure to maintain collagen fibers and primary collagen bundles) which progressed in severity with age. The caudal cruciate ligaments were similarly affected, although the degenerative changes were rarely as severe as in the cranial cruciate ligament. The collateral ligaments underwent minimal degeneration. Sex differences had no bearing on degeneration. The cranial cruciate ligaments in dogs weighing less than 15 kg generally had less severe alterations than those in heavier dogs, and the onset of the degenerative process was delayed by several years. Cranial cruciate ligaments removed from dogs after ligament failure not only had degenerative disease, but also had undergone unsuccessful attempts at repair. In contrast, fibrous repair was rarely present in intact ligaments of asymptomatic dogs with degenerative disease of the cranial cruciate ligament.

Septic arthritis of the distal interphalangeal joint after neurectomy in a mare

Fracture of the lateral wing of the third phalanx with secondary infection of the distal interphalangeal joint occurred in a neurectomized mare. Puncture of the sole may have been the inciting cause, emphasizing the need for careful daily foot care in neurectomized horses.

Squamous cell carcinoma in the jaws of beagles exposed to 90Sr throughout life: beta flux measurements at the mandible and tooth surfaces and a hypothesis for tumorigenesis

We present the first detailed dose-response measurements for 90Sr-induced soft tissue tumors other than hemopoietic dyscrasias in chronically exposed beagles. Twenty-four of 387 dogs exposed to 90Sr beginning in utero and by continuous ingestion to 540 days of age developed squamous cell carcinoma of the jaw during their lifetime. Eleven of the 24 tumors were observed in dogs ingesting 12 microCi/day and receiving cumulative average doses of 6500-12,000 rad. None of these tumors was observed in dogs ingesting less than 1.25 microCi/day and receiving cumulative skeletal average doses of 2100-3900 rad, but four were observed at this level. The teeth of these animals acquired a 90Sr burden that is not removed by skeletal remodeling. Measurements of the radiation dose to soft tissue adjacent to the mandible and teeth of dogs chronically fed 90Sr indicated the first 10 micron of soft tissue adjacent to teeth received a radiation dose initially about the same as the average skeletal doses. By 2000-3000 days, these tissues received about two to three times that calculated for the average skeletal dose, or about four to six times the mean marrow dose. We suggest that these tumors arise from epithelial rests, which are embryonic tissue trapped in the periodontal membrane between teeth and bone.

Evidence for both prelysosomal and lysosomal intermediates in endocytic pathways

Horseradish peroxidase (HRP), an enzyme internalized by fluid phase pinocytosis, has been used to study the process by which pinosome contents are delivered to lysosomes in Chinese hamster ovary cells. Pinosome contents were labeled by allowing cells to internalize HRP for 3-5 min. Following various chase times, cells were either processed for HRP and acid phosphatase (AcPase) cytochemistry or homogenized and fractionated in Percoll gradients. In Percoll gradients, pinosomes labeled by a 3-5 min HRP pulse behaved as a vesicle population more dense than plasma membrane and less dense than lysosomes. In pulse-chase experiments, internalized HRP was chased rapidly (3-6 min chase) to a density position intermediate between the "initial" pinocytic vesicle population and lysosomes. With longer chase periods, a progressive accumulation of HRP in more dense vesicles was observed. Correspondence between the HRP distribution and lysosomal marker distribution was reached after a approximately 1-h chase. By electron microscope cytochemistry of intact cells, the predominant class of HRP-positive vesicles after pulse uptakes or a 3-min chase period was characterized by a peripheral rim of reaction product and was AcPase negative. After 10-120-min chase periods, the predominant class of HRP-positive vesicles was characterized by luminal deposits and HRP activity was frequently observed in multivesicular bodies. HRP-positive vesicles after a 10- or 30-min chase were AcPase-positive. No HRP activity was detected in Golgi apparatus. Together these observations indicate that progressive processing of vesicular components of the vacuolar apparatus occurs at both a prelysosomal and lysosomal stage.

Effects of tendon transfer on the canine scapulohumeral joint

Surgical techniques for correcting medial or lateral instability of the scapulohumeral joint in conditioned research dogs were evaluated. Lateral instability was created by severing the lateral joint capsule and the tendon of insertion of the infraspinatus muscle. In 4 dogs, the tendon of origin of the biceps brachii muscle was then transferred to a position lateral to the greater tubercle in an effort to improve lateral stability. In 3 control dogs, lateral instability was induced, but attempt was not made to stabilize the joint. Medial instability was created by severing the tendon of insertion of the subscapularis muscle and the medial joint capsule. In 3 dogs, the tendon of origin of the biceps brachii muscle was transferred to a position under the lesser tubercle. In 2 dogs, a portion of the tendon of insertion of the supraspinatus muscle was transferred to a medial location. In 3 control dogs, attempt was not made to stabilize the joint. The control dogs (n = 6) demonstrated mild-to-moderate weight-bearing lameness for 7 to 14 days after surgical induction of joint instability and thereafter had normal limb usage. Dogs having had tendon transfer procedures recovered normal limb usage in 4 to 6 weeks and thereafter behaved normally. At necropsy, all joints appeared stable, and the surgical repairs were intact. A variety of joint surface abnormalities consistent with degenerative joint disease was observed, but no consistent pattern was assignable to any given surgical manipulation.

Experimental and clinical investigations of the use of carbon fiber sutures in equine tendon repair

Braided carbon fiber sutures were used to repair surgically transected or lacerated digital flexor tendons of 20 mature horses (10 experimental and 10 clinical cases). In addition, 4 experimental horses had tenectomies that were not surgically repaired; these served as controls for the horses with carbon-implanted tendons. Six of the 10 clinically affected horses were returned to their intended use; 2 were euthanatized because of complications and 2 were still recuperating. The experimental horses were euthanatized at 12 days and 1, 2, 4, 8, and 12 months. Tendon scars were structurally and functionally similar in all of these horses. The main histologic difference between the controls and principals was the more extensive remodeling in the latter group at 8 months.

Characterization of pinocytic vesicles from CHO cells: resolution of pinosomes from lysosomes by analytical centrifugation

Pinocytic vesicles (pinosomes) and lysosomes from suspension cultured, Chinese hamster ovary (CHO-S) cells have been resolved as two non-overlapping organelle populations by analytical centrifugation in Percoll gradients. Pinosomes were labeled with either horseradish peroxidase (HRP), a fluid phase content marker, or by radioiodination by pinocytosed lactoperoxidase (LPO). CHO-S cell lysosomes followed by three different marker enzymes and electron microscopy behaved as a single, dense organelle population. Pinosomes were partially resolved from plasma membrane, a less dense organelle population.