Preliminary study of quantitative aspects and the effect of pulsed electromagnetic field treatment on the incorporation of equine cancellous bone grafts

The quantitative aspects of equine cancellous bone graft incorporation and the possibility of influencing graft incorporation by daily exposure to a pulsed electromagnetic field (PEMF) was studied in eight yearling ponies. In order to be able to quantify formative aspects of graft remodelling, a double and treble tetracycline intravital labelling technique was used. Intravital radiographs were obtained at regular intervals throughout the trial, but were found to be of little assistance in assessing any differences between stimulated and non-stimulated grafts. The ponies were humanely destroyed at regular intervals between nine and 241 days after installation of the graft. Light microscopy and fluorescent light microscopy were used to evaluate quantitative aspects of graft incorporation and to compare PEMF-stimulated grafts with control grafts. There was a small but statistically significant effect of PEMF-stimulation on cancellous bone graft incorporation. In view of this, these observations can only be considered as indicative of a possible trend, but should encourage further studies using different signal modalities.     

Transplantation of the Canine Distal Ulna as a Free Vascularized Bone Graft

An autogenous free vascular bone graft of the canine distal ulna was evaluated. The vascularity of the graft was based on a musculoperiosteal sheath supplied solely by the caudal interosseous artery and vein. Four autogenous heterotopic (ulna to tibia) vascular transfers were performed. Two avascular transfers were performed to provide baseline criteria from which the success of vascularized transfers could be assessed. Clinical lameness evaluation, serial radiographs, bone scintigraphy, and sequential fluorochrome bone labeling were performed after surgery in both vascular and avascular transfers. All dogs were free of lameness in the donor limb by the 26th postoperative day. Serial radiographs revealed rapid graft incorporation and hypertrophy in all vascularized grafts and severe bone resorption in nonvascularized grafts. Histology, microangiography, and evaluation of fluorochrome bone labels were performed 90 days after surgery to determine graft viability, incorporation and temporal remodeling patterns. Microangiography and fluorochrome assessment complemented the histological findings. Based on these findings the distal ulnar bone graft was determined to be both viable and structurally adequate for selected cases of long bone reconstruction.     

Combination of a Corticai Allograft With a Cancellous Autograft in the Canine Tibia

This study was undertaken to determine what difference, if any, occurred when autogenous cancellous bone was placed in the medullary canal of a fresh, 4-cm cortical allograft compared to a fresh cortical allograft alone. Twelve mature dogs were used. A tubular cortical graft was placed in the midshaft of both tibias. The right tibia received the combination graft while the left tibia received a fresh cortical allograft only. Study periods ranged from one week to 17 weeks. The progress of the grafts was assessed by technetium-99m radionuclide bone scans, radiographs, gross and histological examination, and tetracycline labeling. Results indicate that autogenous cancellous bone placed in the medullary canal of a fresh cortical allograft was beneficial to the ingrowth of new blood vessels and incorporation of the cortical graft.     

Effect of hyperbaric oxygen treatment on incorporation of an autogenous cancellous bone graft in a nonunion diaphyseal ulnar defect in cats

OBJECTIVE: To determine whether hyperbaric oxygen treatment (HBOT) would affect incorporation of an autogenous cancellous bone graft in diaphyseal ulnar defects in cats. ANIMALS: 12 mature cats. PROCEDURE: Bilateral nonunion diaphyseal ulnar defects were created in each cat. An autogenous cancellous bone graft was implanted in 1 ulnar defect in each cat, with the contralateral ulnar defect serving as a nongrafted specimen. Six cats were treated by use of hyperbaric oxygen at 2 atmospheres absolute for 90 minutes once daily for 14 days, and 6 cats were not treated (control group). Bone labeling was performed, using fluorochrome markers. Cats were euthanatized 5 weeks after implanting, and barium sulfate was infused to evaluate vascularization of grafts. Ulnas were evaluated by use of radiography, microangiography, histologic examination, and histomorphometric examination. RESULTS: Radiographic scores did not differ between treatment groups. Microangiographic appearance of grafted defects was similar between groups, with all having adequate vascularization. Differences were not observed between treated and nontreated groups in the overall histologic appearance of decalcified samples of tissue in grafted defects. Mean distance between fluorescent labels was significantly greater in cats given HBOT than in nontreated cats. Median percentage of bone formation in grafted defects was significantly greater in cats given HBOT. CONCLUSIONS: Hyperbaric oxygen treatment increased the distance between fluorescent labels and percentage of bone formation when incorporating autogenous cancellous bone grafts in induced nonunion diaphyseal ulnar defects in cats, but HBOT did not affect revascularization, radiographic appearance, or qualitative histologic appearance of the grafts.     

Effects of autogenous cancellous bone on healing of homogenous cortical bone grafts

A comparative clinical and histological study was made of the effects of autogenous cancellous grafts on the rate of healing of homogenous cortical bone grafts in dogs: their right foreleg received homogenous bone grafts and their left foreleg received pre-drilled homogenous bone grafts filled with autogenous cancellous bone. Histologically, the use of homogenous cortical grafts with pre-drilled holes and autogenous cancellous bone appeared to accelerate reorganization and development of these grafts. This was seen particularly 1–2 months post-operatively and at nine months when the graft in the left leg was made up of spongy bone marrow; whereas the right leg graft still contained compact dead bone and the marrow was filled with fibrous tissue.     

Evaluation of Collagen as a Retainer for Autogenous Cancellous Bone Used in Repair of Full Thickness Cortical Bone Defects

A commercially available collagen sponge acting as a cylindrical retainer containing autogenous cancellous bone graft was proposed for treatment of full thickness cortical defects in dogs. Three groups of three dogs each were subjected to removal of at least 1.5 cm of the tibial diaphyses. All tibias were stabilized with bilateral external fixators. Group 1 received collagen surrounding an autogenous cancellous bone graft. Group 2 received collagen and group 3 received no treatment of the ostectomy site. The collagen sponge appeared to allow vascularization of the bone graft as evidenced by new bone formation and was resorbed by 3 months after implantation. Radiographic, histomorphologic, and histomorphometric evaluation at 3 months after surgery showed a greater per cent of bone in the ostectomy site in group 1.     

Vascularization of cancellous chip bone grafts

Fresh autogenous, frozen allogeneic, and commercially prepared xenogeneic cancellous chip bone grafts were placed into plug holes in the tibia and into surgically simulated nonunion defects in the ulna of dogs. The microvascular and correlated histologic reactions were studied at given times up to 12 weeks after the graft implantation. Marked and characteristic differences were noted among the 3 graft materials. Fresh autogenous chips were extensively vascularized by 1 week, and subsequent microscopic healing was rapid. Allogeneic chips were incorporated into all defects, but vascularization and histologic healing rates were slower than those with the fresh autogenous graft material. The xenogeneic graft was poorly incorporated. A foreign body reaction was seen histologically, and corresponding vascularization of the graft was slow and incomplete.     

Histologic and micro-computed tomographic evaluation of the osseointegration of a nonresorbable bone substitute in alveoli of ponies after tooth extraction

OBJECTIVE: To evaluate the biological behavior of a nonresorbable bone substitute (NRBS) in the alveoli of ponies, compared with tissue quality in naturally healing alveoli, after cheek tooth extraction. ANIMALS: 5 clinically normal ponies. PROCEDURES: In each pony, both maxillary fourth premolars (Triadan 108/208) were repulsed bilaterally during anesthesia. One randomly chosen alveolus was filled with NRBS and isolated from the oral cavity by use of dental impression material and a spring-wire retention device. The other alveolus was occluded in its occlusal third portion with dental impression material. One year after surgery, cylindrical lateromedial biopsy specimens were collected from the apical, middle, and occlusal level of each alveolus. Biopsy samples were evaluated for bone mineral density and bone volume via micro-computed tomography; qualitative histologic characteristics were evaluated via light microscopy. RESULTS: Bone mineral density and bone volume were greater in control alveoli, compared with NRBS-treated alveoli. Control alveoli were characterized by the presence of few mature bone trabeculae and wide spaces containing fat tissue and mesenchymal stroma. In treated alveoli, biocompatibility and osteoconductive properties of the NRBS were excellent; continuous bone formation and bone remodeling were also evident. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that the NRBS was integrated well in calcified alveolar tissues in ponies 1 year after maxillary cheek tooth extraction. Further research is necessary to establish the benefits of this NRBS in the development of a dental implant surgical technique in equids.     

Direct current stimulation of bone production in the pony: observations with a diaphyseal osteotomy model

Electrically induced osteogenesis exhibits a dose response curve and can induce bone formation in the absence of trauma and in nonunions. Electrically induced osteogenesis, using direct electric current (DC) in a third metacarpal diaphyseal osteotomy model, in conjunction with internal fixation and postoperative loading, was investigated. Twelve young adult ponies of mixed sex were divided into 2 treatment groups (A and B) of 3 stimulated and 3 controls each and evaluated, using a specifically designed procedure. Stimulated ponies in both groups were given 20 microA of DC via an implanted bone growth stimulator (BGS); group A ponies were stimulated for 60 days and group B ponies for 120 days. Biocompatibility of the BGS was excellent in all ponies. Radiographically, there was more advanced healing with better vascular development in the ponies stimulated for 60 days compared with controls, but no discernible difference was seen at 120 days. Nuclear medical bone imaging revealed a peak uptake at 4 weeks in stimulated groups and the uptake decreased after 8 weeks. Radiopharmaceutical uptake in stimulated ponies was consistently below control uptake throughout the study. Mean specific gravity (SG) of specimens prepared for testing materials properties for group A and B controls were 2.044 +/- 0.119 and 1.939 +/- 0.065, respectively. The SG for group A and group B stimulated were 1.992 +/- 0.049 and 1.876 +/- 0.031, respectively. The SG of specimens obtained from metacarpi of age-matched control ponies was 2.194 +/- 0.166. The ultimate bending strengths and the flexural moduli of elasticity in 60-day control ponies and stimulated ponies were 57 +/- 8.4, 59 +/- 23.9 MN/m2 and 89 +/- 3.5, 106 +/- 6.5 MN/m2 and in 120-day control ponies and stimulated ponies were 13 +/- 1.0, 13 +/- 3.2 GN/m2 and 13 +/- 2.89, 15 +/- 0.577 GN/m2, respectively. Sixty-day samples and 120-day samples had pending strengths (SU) of 25% and 50% that of unfractured cortex, respectively. These findings indicate that 20 microA of DC stimulation on a diaphyseal osteotomy model may not stimulate sufficient bone production to affect the mechanical properties of the bone. Therefore, based on our research, clinical use of BGS in fresh fracture management cannot be recommended.     

Treatment of severely comminuted diaphyseal fractures in the dog, using standard bone plates and autogenous cancellous bone graft to span fracture gaps: 11 cases (1979-1983)

Severely comminuted diaphyseal fractures in 11 dogs were repaired with standard bone plates that spanned a fracture gap filled with autogenous cancellous bone graft. Five dogs had closed injuries, 4 dogs had open fractures, and 2 dogs had infected nonunion fractures for which previous attempts at internal pin fixation had failed. A second autogenous cancellous bone graft was performed in 3 of the dogs during the healing period. The technique was successful in all dogs. The technique was considered a versatile and relatively simple alternative, compared with meticulous small fragment reconstruction and cortical bone allografts.     

A comparison of three methods of end-to-end anastomosis in the equine small colon

Six animals were used to compare simple interrupted, simple continuous, and stapled techniques for end-to-end rotated small colon anastomoses. Three ponies were evaluated three days after surgery for adhesion formation and luminal diameter at each anastomosis site. Two ponies and one horse were evaluated 14 days after surgery for adhesion formation. All anastomosis sites were examined histologically for alignment of tissue planes, and evidence of inflammation. No single technique was superior in all areas examined. While only three of the nine anastomoses had mild fibrinous adhesions at three days after surgery, all anastomoses had varying degrees of well-organized adhesions by 14 days after surgery. Three days after surgery luminal diameter was most comprised by the simple continuous technique. Although the simple interrupted technique was most consistent in its alignment of tissue planes, it was only slightly better than the simple continuous pattern. Stapled anastomoses were inverted or everted at all sites examined. Adhesion formation was less extensive, and histologic evidence of inflammation was less severe, in stapled anastomoses. The average times required to complete the simple interrupted, simple continuous, and stapled anastomoses were 22, 14, and 8 minutes, respectively.     

Deep-Frozen Allogeneic Cancellous Bone Grafts in 10 Dogs: A Case Series

Deep-frozen, aseptically collected and processed allogeneic cancellous bone was implanted in eight dogs during the surgical repair of diaphyseal long bone fractures and in two dogs during arthrodeses. A combined allogeneic and autogeneic cancellous bone graft was used in two fractures with a segmental bone loss of more than 5 cm. Bone union occurred in five fractures and in both arthrodeses. Failure of fixation occurred in two dogs with nonunion fractures and in a third dog with an open, infected fracture. Biopsies from the fracture sites were obtained from these dogs following failure of their fracture fixation. The cancellous bone graft appeared to be in the process of normal incorporation in each case. Failure of fixation was attributed to technical or case management errors or both, in each of the three fractures that failed to achieve bony union. Frozen allogeneic cancellous bone grafts were effectively incorporated when used in the primary repair of fractures and arthrodeses. Combined autogenous and allogeneic cancellous bone grafts may be particularly useful in the repair of fractures with large segmental diaphyseal bone defects. The use of allogeneic cancellous bone grafts in nonunion fractures requires further investigation before it can be recommended.     

Field performance of the equine parasiticide ivermectin in an oral paste

Ivermectin, a derivative of one of the avermectin compounds, was administered at 200 mcg per kg of body weight in an oral paste formulation to 80 mixed-breed ponies of both sexes and various ages. Twenty similar ponies received oral paste vehicle. Anthelmintic activity was determined by comparing fecal egg counts taken before and 14 days after ivermectin treatment to the counts of fecal samples from vehicle-treated controls. Commonly used equine vaccines were administered at the time of treatment. Sixteen of the 20 vehicle-treated ponies had positive counts prior to treatment and 17 were positive 14 days after treatment; 66 of the 80 ivermectin-treated ponies had positive counts prior to treatment; all 80 ponies had zero counts 14 days after treatment. The eggs were identified as strongylid in all the positive ponies while three ponies also hadOxyuris equi eggs prior to treatment.No adverse reactions were attributable to ivermectin oral paste treatment or concurrent vaccine administration.     

Use of an external skeletal fixation device and bone graft for arthrodesis of the metacarpophalangeal joint in horses

Arthrodesis of the metacarpophalangeal joint was attempted in 9 adult horses, using a new external skeletal fixation device and autogenous cancellous bone graft. Four horses had excellent results, 2 horses had fair results, arthrodesis failed in 2 horses, and 1 horse fractured the third metacarpal bone. The advantages of the technique included minimal surgical trauma to the area of injury, immediate rigid fixation of the metacarpophalangeal joint, and access for treatment of soft-tissue lesions at the site of injury. Although pin loosening and pin-track infection were complications when the device was in place, all pin tracks healed without complications after device removal.     

Effects of Exercise and Polysulfated Glycosaminoglycan on the Development of Osteoarthritis in Equine Carpal Joints With Osteochondral Defects

This study assessed the effects of postoperative exercise and intra-articular polysulfated glycosaminoglycan (PSGAG) on the repair of osteochondral defects in the carpal joints of ponies. Eighteen ponies with normal carpi had osteochondral defects (mean dimensions 2.4 cm × 0.9 cm) created arthroscopically on the dorsal aspect of the distal articular surface of the radial carpal bone. The ponies were randomized (while balancing for age [range, 2 to 15 years; median, 5.0 years]) to two groups—nine ponies were exercised and nine were stall confined. Beginning at surgery, six ponies in each group received five weekly intra-articular injections of PSGAG (250 mg) in one joint and lactated Ringer's solution in the contralateral joint; the remaining three ponies in each group received lactated Ringer's solution in both joints. The incremental exercise schedule on a circular, rotating walker was begun six days after surgery and occurred twice daily, reaching a maximum of 0.7 miles of walking and 2.7 miles of trotting by the third postoperative month. The effects of treatment on the joint tissues were determined by weekly lameness examinations and measurement of the range of carpal joint motion, carpal radiographs at six and 17 weeks after surgery, synovial fluid analysis, and cytologic evaluation of alcohol-fixed synovial fluid specimens at weeks 1 through 4 and week 17, and histology of the synovial membrane. Ultrasound images of the carpi were acquired before operation and at weeks 1, 2, 4, 8, 10, 13, and 17. Ponies were euthanatized 17 weeks after surgery. Exercise, without medication, caused more lameness throughout the study compared with no exercise. Exercised, nonmedicated ponies had the greatest limitation to carpal flexion (more painful joints), and nonexercised, nonmedicated (control) ponies had the least limitation to flexion. Radiographic scores indicated that the exercised, nonmedicated ponies had significantly (p < .05) more signs of osteoarthritis than exercised, medicated and control ponies. Ultrasonographic measurements indicated that exercise, without medication, caused the greatest increase in combined measurement of the joint capsule thickness and synovial fluid accumulation at all postoperative times. Synovial lining cell numbers in the synovial fluid from exercised ponies were significantly (p < .05) higher than in nonexercised ponies at week 1, and this trend continued at weeks 4 and 17 (p < .1). There were significantly (p < .05) more morphologic abnormalities in the synovial lining cells from exercised than from nonexercised ponies at week 17. Medication with PSGAG enabled exercised carpal joints to be flexed significantly further from weeks 2 through 6 compared with nonmedicated joints. Medication significantly (p < .05) reduced the combined joint capsule and synovial fluid thickness at weeks 4, 8, and 13 compared with nonmedicated joints. On histologic examination, the synovial membrane matrix of exercised, medicated joints had significantly less chronic inflammatory changes than joints receiving other treatments. The authors concluded that this level of exercise was too intense when superimposed on large osteochondral defects in the carpus because it induced osteoarthritis. Polysutfated gtycosaminoglycan ameliorated the clinical signs of osteoarthritis in the exercised ponies. However, PSGAG was also associated with the formation of cartilage repair tissue that contained less type II relative to type I collagen compared with repair tissue from nonmedicated joints.     

Efficacy of a recombinant equine influenza vaccine against challenge with an American lineage H3N8 influenza virus responsible for the 2003 outbreak in the United Kingdom

Fifteen influenza-naive Welsh mountain ponies were randomly assigned to three groups of five. A single dose of a recombinant ALVAC vaccine was administered intramuscularly to five of the ponies, two doses, administered five weeks apart, were administered to five, and the other five served as unvaccinated, challenge controls. Two weeks after the completion of the vaccination programme, the ponies were all challenged by exposure to an aerosol of influenza virus A/eq/Newmarket/5/03. Their clinical signs were scored daily for 14 days according to a standardised scoring protocol, and nasal swabs were taken daily for 10 days to monitor the excretion of virus. The challenge produced severe clinical signs of influenza (fever, coughing, nasal discharge and dyspnoea) in all five control ponies, but the vaccinated ponies developed only mild disease, consisting of a serous nasal discharge lasting for only one day. The excretion of virus was almost completely suppressed in the vaccinated ponies, but the control ponies shed the virus for up to seven days after the challenge.     

Comparison of bone healing,as assessed by computed tomography,following tibial tuberosity advancement in dogs with and without autogenous cancellous bone grafts

Abstract

AIMS: To objectively compare measures of bone healing, using computed tomography (CT) in dogs following bilateral tibial tuberosity advancement (TTA), between tibiae treated with and without autogenous cancellous bone grafts.

METHODS: Ten dogs with bilateral cranial cruciate ligament disease requiring surgical stabilisation were prospectively recruited to undergo single-session bilateral TTA, with only one, randomly assigned, tibia receiving bone graft in the osteotomy deficit. Bone healing at the osteotomy site was assessed using CT performed 38–70 days post-operatively. CT images were evaluated using both objective measurements of osseous bridging and subjective evaluation by six radiologists. Repeated measures ANOVA was used to compare the objective outcomes between the grafted and non-grafted tibiae.

RESULTS: The mean percentage of the osteotomy deficit bridged at the lateral cortex was greater in grafted (77.6, SD 35.2%) compared to non-grafted (63.0, SD 36.5%) tibiae (p=0.001), but did not differ at the medial cortex (p=0.1). The mean minimum callus width was greater in grafted (7.2, SD 3.3 mm) compared to non-grafted (3.6, SD 2.9 mm) tibiae (p<0.001). There was no difference in mean attenuation (measured in Hounsfield units) of the callus between grafted and non-grafted tibiae (p=0.5). The grafted tibia was deemed to have superior bone healing in 50/60 subjective assessments made by radiologists.

CONCLUSIONS: Superior osseous bridging was detected by CT analysis following TTA using autogenous cancellous bone grafts compared with no graft. This was shown by greater bridging percentage at the lateral cortex and formation of a broader callus. Qualitative assessments made by six radiologists also supported the conclusion that bone healing was improved by use of autogenous cancellous bone graft. CT was a useful method for assessing evidence of bone healing following TTA.

CLINICAL RELEVANCE: These findings justify the application of autogenous cancellous bone graft to augment healing following TTA in dogs.     

The serological response of foals to vaccination against strangles.

A group of 100 foals was given either a commercial bacterin or an autogenous vaccine consisting of whole cells and an acid extract of Streptococcus equi. During the study, some of the foals developed clinical strangles. Various sets of sera were collected from these foals prevaccination, during vaccination, postvaccination and postinfection. The serological response of these foals was measured by passive haemagglutination and long chain tests. In foals which remained healthy, the highest titres were reached within one to two months postvaccination with a passive haemagglutination 10 x log2 mean titre of 6.78 and the long chain indices of 4.41. These levels persisted for 120 days postvaccination. Those foals which had clinical strangles exhibited lower passive haemagglutination titres (3.78) at one to two months postimmunization, but rose significantly after recovery. Four ponies immunized with formalinized Str. equi bacterin showed a partial protection against the challenge infection. The passive haemagglutination titres, long chain indices and serum bactericidal activity in these ponies were highest at 35 days postvaccination but did not increase after infection.     

NONGRAFTED AND GRAFTED OSTEOTOMIES OF PROXIMAL SESAMOID BONES OF THE HORSE

A radiographic study of healing patterns of nongrafted and grafted basilar osteotomies of proximal sesamoid bones in 14 horses was performed. Osteotomies were created in one proximal sesamoid bone of each fromt leg. One was treated by an autogenous rib graft, and the other was left nongrafted. Wedge-shaped cortical bone, corticocancellous bone with multiple drill holes, and chips of cancellous hbone were used as autogenous grafts. Presurgical, surgical, and postsurgical radiographic examinations were performed. The longest follow-up period was 40 weeks. High detail radiography of 3-mm bone sections and microangiography were also perofromed. Radiographic interpretation of lack of bone healing was erroneous in approximately one-half of the cases. Lack of an external bridging callus was incorrectly interpreted as lack of bony union. If noted, periosteal new bone formation failed to develop into a pattern of bridging callus. Radiographs did not permiit detection of the osteotomy line entering the articular surface or displacement of distal fragments. From angiography obtained ten weeks after surgery, the pattern of blood supply was similar in nontreated and grafted sesamoid bones. Microangiography showed rich vascularization of the cancellous graft and callus, reflecting good healing activity, whitle vascularization of the osteotomy site was absent in the nontreated osteotomies.     

Pacheco's parrot disease in macaws of the Lisbon's Zoological Garden. Description of an outbreak, diagnosis and management, including vaccination

The Lisbon's Zoological Garden, Portugal, has maintained for many years a large collection of psittacine birds without any serious health problems. Unexpectedly, in April 1999, a total of nine macaws died after a short period of illness. Clinical signs consisted mainly of anorexia, ruffled feathers and yellowish droppings. A herpesvirus was isolated from brain, trachea, lung, liver, spleen, kidney and intestine of each of the examined dead birds, confirming that all animals succumbed during viraemia. Serotyping of the isolate in cross neutralization tests with reference sera prove that the outbreak was caused by serotype 3 of Pacheco's parrot disease herpesviruses. An autogenous, formalin-inactivated vaccine with adjuvant (aluminium hydroxid gel) was prepared from one of the isolates and injected intramuscularly 14 days and six weeks after the onset of mortality in an attempt to protect the remaining psittacine birds in the zoo from the disease. The autogenous vaccine was well tolerated and was able to rapidly stop virus spread and morbidity and mortality among the psittacine birds. Follow-up studies demonstrate that all nine blood samples from vaccinated birds obtained nine month' after the second vaccination contain neutralizing antibodies. Twenty five month' after vaccination two out of four serum samples were still antibody positive. No herpesvirus was isolated from faecal samples nine and twenty five months after the onset of the outbreak. These data prove that the autogenous vaccine played a major role in containing a severe outbreak of Pacheco's parrot disease in a large collection of psittacine birds.