Healing of full-thickness cartilage compared with full-thickness cartilage and subchondral bone defects in the equine third carpal bone.

The effect of lesion depth on the quality of third carpal bone cartilage repair was examined. A 1-cm diameter articular defect penetrating the calcified cartilage in one limb and the subchondral bone plate in the opposite limb was created in the radial facet of the third carpal bones. Clinical and xeroradiographic examinations were performed every 4 weeks until 4 months (3 horses) and 6 months (3 horses) after surgery. The synovial membrane, non-opposing articular surfaces and articular defects were examined grossly, histologically and histochemically. Grossly, deeper defects contained thicker, whiter tissue, but both joints contained generalised degenerative changes. Defects extending through calcified cartilage were filled deeply by fibrocartilage and superficially by fibrous connective tissue. Defects extending through subchondral bone were consistently filled with hyaline-like cartilage in the depths of the lesion, fibrocartilage in the intermediate layer and fibrous connective tissue superficially. The results indicate that subchondral bone is the source of hyaline-like cartilage repair tissue and suggest that quality of healing of cartilage defects may be improved by penetrating the subchondral bone plate. It also appears that the synovitis associated with the procedure must be controlled before the procedure can be advocated for treatment of clinical cases.     

Development of hoof cartilage with special considerations of its ossification

The pre- and perinatal development of the hoof cartilage is described concerning the histological structure and surrounding vessels. Beginning in the third month of fetal development, the anlage of the hoof cartilage is still present in typical shape and location. It is built out of mesenchymal connective tissue. During further fetal development, the connective tissue cells will differentiate into two cell populations, fibroblasts and chondroblasts. Vessels, traversing the hoof cartilage, are surrounded by loose connective tissue, which will partially develop fibrocartilage. At birth, hoof cartilage consists of hyaline cartilage, which is disrupted by vessels, embedded in fibrous connective tissue and/or fibrocartilage. The development of the hoof cartilage is the base to understand its structure and the predisposing locations for its ossification.     

Repair of full-thickness defects in the femoral trochlea of dogs after trochlear arthroplasty

Trochlear arthroplasty was performed on one stifle in each of 18 Greyhounds; their contralateral pelvic limbs and the pelvic limbs of 2 dogs treated with sham surgery were controls. At 2, 4, 8, and 16 weeks, radiography, glycosaminoglycan histochemical analysis, histologic examination, and scanning electron microscopy of the trochlear surface were done. All dogs used the limb and walked without an observable limp within 2 weeks after surgery. Radiography at euthanasia did not reveal degenerative changes. Well-vascularized, highly cellular, loose fibrous connective tissue was reorganized with time into a dense fibrous connective tissue covering the entire wound. Scanning electron microscopy revealed that the replacement tissue surface was rough, torn, and debris-covered. Differential histologic staining established that change to fibrocartilage had begun deep within the replacement tissue. Histochemical analyses corroborated those observations.     

Subcutaneous tissue reaction to polyethylene terephtalate-covered electronic identification transponders in pigs.

Polyethylene terephtalate-covered identification transponders were injected in 4 week old piglets to examine clinically and histologically the reaction in the surrounding tissue after 4, 7 and 21 days and 6 months. Inflammatory signs at the injection site were clinically noticed from 2 days onwards and gradually decreased after day 3. A second series of inflammatory events occured in some animals around day 7. Swelling was observed thereafter in a few animals. In the pigs slaughtered at day 4, all samples showed a layer of exudate and debris surrounding the transponder. Afterwards a fibrous capsule developed. The mean thickness of reactive tissue decreased significantly (p < 0.01) between days 4 and 7 and days 14 and 21, and remained unchanged between day 21 and 6 months. The mean (+/- s.e.) capsule thickness was 0.32 +/- 0.12 mm after 6 months. It is concluded that PET-covered transponders are encapsulated in fibrous connective tissue within 3 weeks after injection at the base of the ear. After 6 months the capsule around the transponder revealed no or only minor signs of inflammation.     

Surgical repair of fracture of the os penis in a dog

An eight-year-old male Australian cattle dog cross was presented with complete urethral obstruction secondary to fracture of the os penis which had occurred two years earlier. Obstruction was associated with callus and fibrous tissue proliferation compressing the urethra at the fracture site. The problem was satisfactorily resolved by removing excess bone and fibrous tissue and stabilising the fracture with a stainless steel finger plate.     

Osteochondral Defects of the Lateral Trochlear Ridge of the Distal Femur of the Horse Clinical, Radiographic, and Pathological Examination and Results of Surgical Treatment

Osteochondral defects of the lateral trochlear ridge of the distal femur were identified in 15 joints of 10 horses. Lesions were bilateral in five horses and unilateral in five horses. Thirteen of these 15 defects were treated by curettage through a craniolateral femoropatellar arthrotomy. Subcutaneous seroma formation and partial skin dehiscence occurred in nine stifles. Lameness attributable to the stifle joint was no longer apparent at 6 and 12 months after surgery. The normal subchondral bony contour of the lateral trochlear ridge was altered in all joints after surgery. The subchondral bone was uniformly increased in density in all joints, and six lateral trochlear ridges had small focal radiolucent regions within the subchondral bone, which suggested that complete removal of the original lesion had not been achieved. Healing of the surgical site between 2 weeks and 14 months was evaluated in four joints. Granulation tissue from mesenchymal elements in subchondral marrow spaces gradually filled the defects with fibrocartilage.     

Variation in the ossification process of the anconeal and medial coronoid processes of the canine ulna

This morphological and radiographic study investigates the ossification process of the anconeal and medial coronoid processes of the ulna in a sample of 142 dogs ranging in age from neonatal to 44 weeks. The anconeal process was noted to develop by appositional ossification, formation of a separate ossification center, or a combination of both. Several developmental stages of the ossification center of the anconeal process as well as its anatomic position and radiographic appearance are described. Differences have been noted in the shape of this ossification center as well as the ossification process itself. The medial coronoid process develops exclusively by appositional ossification. Unlike ossification of the anconeal process, ossification of the medial coronoid process was completed earlier (p < 0.05) in smaller than in the larger dogs. In smaller dogs, both the medial coronoid and anconeal processes were found to be mature by the age of 16 weeks. In the larger dogs, ossification of the anconeal process was completed not before 14 weeks of age and ossification of the medial coronoid process was completed about 6 weeks later.     

Morphologic study of repair of induced osteochondral defects of the distal portion of the radial carpal bone in horses by use of glued periosteal autografts [corrected

The use of periosteal autografts to resurface osteochondral defects was investigated in 10 horses (2 to 3 years old), and the repair tissue was characterized morphologically. Middle carpal joint arthrotomies were made, and osteochondral defects were induced bilaterally on the distal articular surface of each radial carpal bone. Each defect measured approximately 1 cm2 and extended 3 mm into the subchondral bone plate. Residual subchondral bone plate of control and principal defects was perforated by drilling. A sterile fibrin adhesive was made by mixing a fibrinogen component and a thrombin component. A periosteal autograft was harvested from the proximal portion of the tibia and was glued onto the recipient osseous surface, with its cambium facing the joint cavity. Control defects were glued, but not grafted. Horses were walked 1 hour daily on a walker, starting at postoperative week 7 and continuing for 9 weeks. Sixteen weeks after the grafting procedure was done, carpal radiography was performed, after which horses were euthanatized. Quality of repair tissue of control and grafted defects was evaluated and compared grossly, histologically, and histochemically. Using a reticule, the proportions of various repair tissue types filling each defect were quantitated. Seven weeks after the grafting procedure was done, bilateral arthroscopy revealed synovial adhesions and marginal pannus formation in control and grafted defects. None of the autografts was found floating unattached within the respective middle carpal joints. At 16 weeks, the gross appearance of most grafted and nongrafted defects was similar, and repair was dominated by a fibrous pannus. In 4 grafted defects, bone had formed either concentrically within the defect or eccentrically in the fibrous adhesions between the defect and the joint margin. Histologically, all grafted and nongrafted defects were repaired similarly by infiltration of a mixture of fibrous tissue, fibrocartilage, and bone. Fibrous tissue was the predominant tissue in most defects and its mean proportion was 56 and 59% in the grafted and nongrafted defects, respectively. Fibrocartilaginous tissue in the deeper layers approximated 20%, and woven bone at the base of the defect was 20% in all defects. Histochemically, difference in staining for proteoglycans was not observed between grafted and nongrafted defects. Little remaining original periosteal graft tissue was evident at the defect sites. The only distinguishing feature of grafted defects was the presence of islands of bone formation either at the defect site (n = 2 horses), or in somewhat dorsally displaced tissue that was incorporated in fibrous adhesions (n = 2 horses).(ABSTRACT TRUNCATED AT 400 WORDS)     

Histopathological changes in myxosomosis in rainbow trout

Rainbow trout, caught in a pond 25, 45 and 48 days from releasing, were studied for histopathological changes. Protozoan activity destroys the basal matter of the hypertrophic cartilage. The chondral tissue around plasmodium reacts by showing an increased basophilia and by chondrocytal reaction. The plasmodia tend to spread spherically, but the spreading is prevented by compact bone, connective tissue, or hardened cartilage with flattened chondrocytes. One host can bear one plasmodium or more plasmodia, up to the possibility of a generalized process. The host organism reacts to the destructive changes caused by the protozoan by letting its connective tissue cells grow into the cavities produced by the protozoan, into the plasmodia of the protozoan and into the destruction line; thus the protozoan is separated from the nutrition base. The connective tissue enters the lesion via a hole in compact bone or via a fissure between bone and cartilage. Circulation and blood elements were not found to be present in the penetrating connective tissue. The bone tissue reacts to the presence of the protozoan by thickening the periosteum. Mature spores in the lesions by the protozoan are reduced with host age.     

The effect of housing on the development of calluses and subcutaneous mucus cysts on the limbs of swine

Extremities of pigs often show swelling of various size and consistency. The aim of the present investigation was to determine the cause of the swelling with special emphasis on housing conditions. A total of 168 animals kept on slatted and/or partly slatted floors and 55 pigs kept on straw were examined. The swelling was partially caused by connective tissue proliferation only, but more often consisted of non inflamed subcutaneous bursae. Skeletal changes near the periost could never be seen. In pigs kept on straw weals and subcutaneous bursae practically never developed, whereas in animals kept on concrete, these changes did occur more frequently and were more pronounced with time.     

IMAGING DIAGNOSIS—MEDULLARY TIBIAL INFARCTION IN A HORSE

An Andalusian Stallion with left hind limb lameness had a radiolucent lesion in the medullary cavity of distal tibial metaphysis. After euthanasia for other disease, the tibia was examined with magnetic resonance (MR). The MR imaging sequences were characterized by a double line sign, although showing quite different lesion area intensities. Histologically, the lesion was compatible with medullary infarction being characterized by normal spongy bone, areas of abundant fibrous tissue and numerous necrotic adipocytes in various stages of destruction.     

The Effect of Exercise on the Healing of Articular Cartilage Defects in the Equine Carpus

Arthroscopic surgery was performed on 12 horses (2-4 years of age) to create a 7 x 14 mm full-thickness cartilage defect in one radial carpal bone and in the contralateral third carpal bone. Six horses remained confined to a small paddock and six horses underwent a program of increasing exercise consisting of walking, trotting, and cantering for 13 weeks. All lesions showed evidence of healing at week 6 that progressed to more complete healing at week 13. There was no difference in the amount of repair tissue covering the defect. Histologically, the lesions healed with a combination of fibrous tissue and fibrocartilage. The repair tissue was significantly thicker in the exercised horses but there was no difference in repair quality. It was concluded that radial carpal and third carpal lesions have an equal ability to heal and that early postoperative exercise is not detrimental to the repair tissue within these carpal cartilage defects.     

Effect of surgical technique on radiographic fusion of the anconeus in the treatment of ununited anconeal process

O bjectives : The aim of this study was to determine if internal fixation of the anconeus combined with a proximal ulnar osteotomy was more likely to result in fusion of the anconeus to the ulna compared with a proximal ulnar osteotomy alone.
M ethods : A total of 12 orthopaedic referral clinics reviewed their clinical databases for cases of ununited anconeal process. Demographic and clinical parameters were collected along with radiographic follow-up at a minimum of four weeks. Cases treated with proximal ulnar osteotomy alone were compared with those treated with proximal ulnar osteotomy + internal fixation. Both groups were compared for background and disease variables. We tested for an association between treatment method and whether radiographic anconeal union had occurred.
R esults : A total of 47 elbows (44 dogs) were identified. Of these, 28 cases (average age 7·6 months) were treated with proximal ulnar osteotomy (of which eight were stabilised with an intramedullary pin) alone. Nineteen cases (average age 7·1 months) were treated with proximal ulnar osteotomy + internal fixation. The two groups were not significantly different in age (P=0·638, Mann-Whitney U test). Fourteen of 28 cases with proximal ulnar osteotomy alone displayed anconeal union at follow-up compared with 16 of 19 cases of proximal ulnar osteotomy + internal fixation, and this difference was statistically significant (P=0·029, Fisher's exact test).
C linical S ignificance : These data suggest that use of a lag screw to stabilise and compress the ununited anconeal process in addition to proximal ulnar osteotomy produces a better radiographic outcome. It is argued that radiographic union of the anconeus is likely to be associated with better long-term clinical outcome but further studies are required to confirm this.     

Digital cushions in horses comprise coarse connective tissue, myxoid tissue, and cartilage but only little unilocular fat tissue

Digital cushions were studied in horses with particular reference to vascularization, tissue constituents and matrix components. The cushions mainly resembled a network of coarse collagen bundles. The areas inbetween the bundles were replenished with loosely woven interstitial connective tissue, myxoid tissue, and fibrocartilage. Expected masses of fat lobules were missing: only solitary adipocytes or small groups of adipocytes were seen. Vascular supply to the cushions was remarkably poor. The mucinous myxoid matrix largely consisted of hyaluronan with little sulphated glycosaminoglycans. Myxoid cells were stellate or ramified in shape and showed a tendency to store glycogen and lipid droplets. Myxoid cells reacted for vimentin and stained for S-100 protein. Moreover, myxoid cells often reacted for neuron specific enolase and glial fibrillary acidic protein. Myxoid tissue continuously transformed into loosely organized interstitial connective tissue with fibroblasts, which remained unreactive when tested for neuroectodermal markers. Myxoid tissue also was not clearly demarcated against irregularly interspersed islets of fibrocartilage or hyaline cartilage. Chondrocytes did not stain for neuron specific enolase but reactivity for S-100 protein and glial fibrillary acidic protein was noted in peripheral regions of fibrocartilage. Single or grouped unilocular fat cells were rarely placed into myxoid areas. Unilocular fat cells stained for vimentin, S-100 protein, and occasionally for glial fibrillary acidic protein but not for neuron specific enolase. Continuous transformation of myxoid tissue into cartilage together with corresponding reactivity for neuroectodermal marker proteins of myxoid cells and peripherally located chondrocytes suggest close relationship between myxoid cells and chondrocytes. The same criteria indicate relationship between myxoid cells and adipocytes. Coarse connective tissue, myxoid tissue, fibrous cartilage, and fat cells are functionally combined to absorb mechanical shock in the horse digital cushions.     

Thymic branchial cysts in the dog and cat

Branchial cysts of the thymus were diagnosed in 15 dogs and 2 cats. The main clinical sign was dyspnea. Pleural effusion varied in degree from minimal to severe. In all animals, an encapsulated mass in the cranial mediastinal region was found to consist of multiple epithelial cysts embedded in a stroma of fibrous connective tissue, adipose tissue, and vessels. Surgical resection of the cysts was performed in 7 dogs; 3 dogs survived and were clinically normal for 18 to 36 months.     

Radiographic Evaluation of the Anconeal Process in Skeletally Immature Dogs

Objective: To determine if a secondary center of ossification (SCO) of the anconeal process is present in skeletally immature dogs that do not develop an ununited anconeal process (UAP). Study Design: Case series. Animals: Dogs 77–154 days of age with conditions other than developmental disease of the elbow (n=78 dogs; total elbows=100). Methods: Mediolateral radiographic projections of the elbow were reviewed for presence or absence of a SCO of the anconeal process. Results: A SCO was radiographically evident in 16% of elbows from breeds that have been reported to be affected by UAP. The appearance of the SCO was different to an UAP fragment. None of the elbows with SCO of the anconeal process developed UAP. A SCO was not present in any small breed dogs. Conclusions: A SCO of the anconeal process is uncommon in medium and large breed dogs and the presence of a SCO does not indicate that UAP will develop. Clinical Relevance: Because radiographic diagnosis of a SCO of the anconeal process and UAP lesions have distinct appearances, an earlier diagnosis of UAP is possible.     

Acellular and glutaraldehyde-preserved tendon allografts for reconstruction of superficial digital flexor tendon in bovines: Part II--Gross, microscopic and scanning electron microscopic observations

Sixteen tenorrhaphies were performed at mid-metatarsal region in eight buffalo calves. A 2-cm long gap was created in the superficial digital flexor (SDF) tendon in all animals. The gap was immediately repaired with acellular grafts in animals of group I, 1% glutaraldehyde-preserved tendon allografts in group II, and in group III the defect was repaired with autografts (control group). The contralateral limb in each animal was operated after an interval of 60 days and the animals underwent the same procedure according to the designed groups. Gross observation revealed filling of host tendon-graft junction with fibrous connective tissue. Increased vascularity was seen in group I when compared with group II and III. Graft was resorbed in animals of group I and III, whereas partial absorption of graft was seen in group II. Histological observations on day 30 revealed restoration of cellularity in acellular graft and fragmentation and resorption of glutaraldehyde-preserved graft. Graft was replaced by newly formed fibrous connective tissue. Tissue reaction around polygalactin suture consisted of plasma cells, lymphocytes and macrophages. On day 90, most of the acellular graft was replaced by newly formed fibrous connective tissue. In group II the majority of graft portion remained at the site and was in a state of resorption. In the control group it was difficult to distinguish between the host tendon and the graft. Scanning electron microscopical observation showed densely packed neoformed tissue at host tendon-graft junction. Hydrolysis and invasion of connective tissue between polygalactin suture filaments, resorption of graft with cavity formation and dissolution of ground substance were observed.     

Fibrous dysplasia of mandibular bone in a dog

A nine-year-old, male German shepherd dog was presented with a firm, discrete mass lingual to the interdental space of the mandibular left third and fourth premolars. The lesion was excised and diagnosed as fibrous dysplasia of bone based on histopathologic examination. Fibrous dysplasia of bone is a rare, non-aggressive, radiolucent, non-neoplastic lesion considered developmental in origin. Usually observed as a solitary lesion, it has been reported in animals and man in the polyostotic form. The disease process causes deformity of bone which may lead to loss of bone strength. Clinical signs are secondary to site specific problems associated with expansile bone lesions. Oral examination performed 18-months postoperatively indicated no signs of recurrence.     

Radiographic changes in elbow dysplasia following ulnar osteotomy--a case report and review of the literature

This case report describes the results of bilateral elbow arthrotomy and a unilateral ulnar osteotomy in a 10-month-old dog with bilateral elbow dysplasia. Fragmented coronoid processes were removed from both joints via bilateral medial arthrotomies. On the right side an ulnar osteotomy was also performed using a caudolateral approach. Bilateral flexed lateral elbow radiographs taken before surgery and 5 months postoperatively were assessed for changes in osteophyte size on the anconeal process, caudal epicondylar ridge and radial head. Osteophytes on the anconeal process and caudal epicondylar ridge disappeared over the postoperative period in the joint that received an ulnar osteotomy. In the contralateral joint the size of the oesteophytes on the anconeal process and caudal epicondylar ridge increased in size during the same period.     

Wound Healing and Brain Stem Auditory Evoked Potentials After Experimental Ventral Tympanic Bulla Osteotomy in Dogs

Ventral tympanic bulla osteotomy was performed in 13 normal dogs to evaluate healing and retention of brain stem auditory evoked potentials (BSAEP). Healing was evaluated by gross and microscopic examination of the middle ears after 1 (n = 2), 4 (n = 8), 5 (n = 1), and 6 (n = 1) weeks. One dog was eliminated from the study. Brain stem auditory evoked potentials were measured using an air-conducted sound stimulus before and after surgery and before killing. Nine of 12 dogs re-formed the tympanic bulla by formation of fibrous connective tissue lined with cuboidal epithelium in the osteotomy site. Four of the nine dogs had a reduced tympanic bulla volume (estimated 20% to 40% volume reduction) caused by soft tissue ingrowth through the osteotomy. Nine of 12 dogs had proliferation of subperiosteal new bone from the inner surface of the tympanic bulla that varied in severity. Three of these nine dogs had nearly complete obliteration of the tympanic cavity by proliferating subperiosteal new bone. Eight dogs had nodules of granulation tissue containing new bone and mineralization diffusely distributed on the surfaces of the middle ear. The measured BSAEP sensitivity before killing was equivalent to preoperative levels in 11 dogs. The remaining dog had no change in auditory sensitivity after surgery but had a markedly reduced BSAEP detection threshold before killing. This appeared to be attributable to mechanical impingement on the ossicles and tympanic membrane by proliferating bone within the tympanic cavity. This study showed that after ventral tympanic bulla osteotomy the tympanic bulla rapidly re-forms with no deleterious effect on hearing in most dogs treated. However, the internal surfaces of the middle ear appear to be sensitive to surgical trauma, and extensive new bone proliferation is easily induced. This response may be extreme, resulting in middle ear obliteration and reduced auditory sensitivity.