Clinical Response to Antibiotic Impregnated Polymethyl Methacrylate Bead Implantation of Dogs with Severe Infections after Limb Sparing and Allograft Replacement -18 Cases (1994-1996)

Successful treatment of severe orthopaedic infections in people and animals has been augmented by the use of antibiotic impregnated polymethyl methacrylate (PMMA) bead implantation at the site of infection. High local wound concentrations of antimicrobials can be achieved without resulting in toxic levels systemically. Clinical, radiographic and pathological response was evaluated following PMMA beads impregnated with vancomycin and tobramycin implanted in 18 dogs with severe infections following “limb sparing” operation with allograft replacement for osteosarcoma. A variety of aerobic and anaerobic bacterial organisms were cultured from the sites of infection and numerous systemic antimicrobial drug combinations were used in an attempt to control the infections prior to the implantation of the beads. In 12 of 18 (67%) dogs implanted, clinical signs of infection resolved within a median of four weeks post implantation. Three of 12 (25%) had recurrence of signs at a median of 17 weeks post implantation. This was not a randomized, prospective controlled trial and limitations to the study exist, the most notable being the variability in individual patient treatment. However, antibiotic impregnated PMMA bead implantation may play a role in the treatment of severe infections in dogs.

Eighteen dogs with severe infections were implanted with polymethyl methacrylate beads impregnated with tobramycin and vancomycin. In 67% of dogs implanted, clinical signs of infection resolved within a median of four weeks. Antibiotic impregnated PMMA bead implantation may play a role in the treatment of severe orthopedic infections in dogs.

This study was supported in part by grant number 2 PO1 CA 29582 from the National Cancer Institute. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the National Cancer Institute, USA.

Cystic Periosteal Osteosarcoma in the Tibia of a Dog

Periosteal osteosarcoma, a rare neoplasm in dogs, was diagnosed in an eleven- year-old Golden Retriever. In this case, the tumour formed a single, large, fluid filled cyst, that originated from the periosteum of the tibia. Periosteal osteosarcomas are intermediate grade tumours and behave less aggressively than central osteosarcomas, however, they are more malignant than the low grade parosteal osteosarcoma. Cure for periosteal osteosarcoma in people may be achieved in 70-80% of cases by local excision. In this case euthanasia was elected one year post-amputation due to emaciation and lethargy associated with metastatic disease.

A cystic periosteal osteosarcoma was diagnosed in an eleven year old Golden Retriever. The tumour originated from the tibia and formed a single large fluid filled cyst. Periosteal osteosarcomas are rare, moderately aggressive tumours that may be differentiated from parosteal, surface, and central osteosarcomas. In this case euthanasia was elected one year post-amputation due to metastatic disease.

Comparison of Cemented and Non-cemented Allografts in Dogs with Osteosarcoma

This study compares the radiographic and histological appearance of cemented and non-cemented massive cortical allografts in dogs that underwent a limb sparing procedure for osteosarcoma of the distal radius. Treatment consisted of removal of the affected bone and pancarpal arthrodesis using non-cemented (n = 13) or cemented (n = 47) fresh-frozen allografts. Allografts were evaluated using a radiographic and histological scoring system and compared statistically between groups. Allografts with better healing received a higher radiographic score and a lower histological score. The mean radiographic scores, for proximal union and distal union, were significantly greater in the non-cemented group at most evaluation periods. Complications after the operation included screw, plate, allograft and host bone failure, infection and local tumour recurrence. Screw failure in the allograft and allograft failure were significantly more common in the non-cemented group. Histological examination was performed on 44 dogs and cement increased the mean combined histological scores, and mean healing scores of the distal host-graft interface significantly. The use of cemented allografts significantly decreases complications associated with implant loosening or allograft failure but may slightly delay allograft healing. At this point, the clinical relevance of the delay in healing is questionable and the benefits of intramedullary PMMA would appear to outweigh this relative delay in healing.

This study evaluated 60 radial allografts after limb sparing procedures using a standardized radiological and histological scoring system. The use of cemented allografts significantly decreased complications associated with implant loosening or allograft failure but may slightly delay allograft healing.

Sustained Release of Cisplatin in Dogs from an Injectable Implant Delivery System

Cisplatin was incorporated into an in-situ forming biodegradable implant delivery system (ATRIGELO) consisting of a biodegradable polymer dissolved in a pharmaceutically acceptable solvent. The polymer solution with the suspended cisplatin was injected subcutaneously into the flank or shoulder of six healthy beagle dogs where the water-insoluble polymer precipitated upon contact with body fluids and formed a solid implant for the controlled release of the drug. Each dog received four injections, spaced thirty days apart, of a formulation containing either poly(DL-lactide-co-caprolactone) (PLC) or pely(DL-lactide-co-glycolide) (PLGA) dissolved in dimethyl sulfoxide (DM8O) and loaded with 8% by weight cisplatin. Dosage levels of 70, 105, and 157.5 mg/m2 were used to determine dosage escalation effects. Injections of the same formulations without the drug served as controls. Samples of blood were taken at appropriate times over the four months of treatment and analyzed for platinum concentration by atomic absorption spectroscopy. Local tissue and systemic toxicities were also determined. Both formulations exhibited sustained release of cisplatin with peak serum concentrations of platinum being attained in about two days followed by gradually decreasing platinum levels to day thirty. Consistent drug release profiles were observed for each of the four thirty-day treatment periods. The dosage escalation results exhibited an approximate 50% increase in peak platinum levels and area-under-the-curve (AUC) values for each 50% increase in drug dose. Local tissue toxicity to the cisplatin-containing implants was variable and appeared to be unrelated to dose level or direction number. Tissue reaction to the implants without drug was minimal indicating a role of cisplatin in the tissue reactions. Systemic toxicity, as judged by clinical parameters and clinicopathologic evaluation, was not noted at any dose level or injection time.

Diagnoses and Clinical Outcomes Associated with Surgically Amputated Feline Digits Submitted to Multiple Veterinary Diagnostic Laboratories

Amputation is commonly performed in an attempt to both treat and diagnose conditions affecting the digits of cats. The records of multiple veterinary diagnostic laboratories were searched to identify submissions of amputated digits from cats. Eighty-five separate submissions were reviewed for diagnosis, age, sex, limb of origin, and digits affected; and the original submitting clinics were surveyed to determine clinical outcome. The Kaplan-Meier product-limit method was used to determine the disease-free interval and survival time. Neoplastic disease was identified in 63 of 85 submissions, with exclusively inflammatory lesions composing the other 22 cases. In 60 (95.2%) of the neoplastic cases, a malignant tumor was identified. Squamous cell carcinoma was the most commonly identified malignant tumor ( n = 15; 23.8%) and was associated with a median survival time of 73 days. Other diagnoses included fibrosarcoma ( n = 14; 22.2%); adenocarcinoma, likely metastases of a primary pulmonary neoplasm ( n = 13; 20.6%); osteosarcoma ( n = 5; 7.9%); mast cell tumor ( n = 4; 6.3%); hemangiosarcoma ( n = 5; 7.9%); malignant fibrous histiocytoma ( n = 2; 3.2%); giant cell tumor of bone ( n = 2; 3.2%); and hemangioma ( n = 2; 3.2%). Giant cell tumor of bone has not been previously described in the digits of cats. Various neoplasms can occur in the digits of cats, and submission of the amputated digit for histopathologic diagnosis is essential to determine the histogenesis and predict the clinical outcome.

DOG1 is a sensitive and specific immunohistochemical marker for diagnosis of canine gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) and leiomyosarcomas are histologically similar primary neoplasms commonly occurring in the gastrointestinal tract of dogs and humans. Immunohistochemical staining (IHC) is needed to differentiate between these 2 entities and positive reactivity for KIT (cluster of differentiation [CD]117) is regarded as the gold standard for diagnosis of canine GIST. Studies estimate 5–10% of human GISTs stain negative or only weakly positive for KIT and have identified DOG1 (discovered on gastrointestinal stromal tumors protein 1) as a highly sensitive and specific marker for human GISTs. The purpose of this study was to evaluate immunoreactivity of a commercially available DOG1 antibody for use in diagnosis of canine GISTs. Fifty-five primary mesenchymal gastrointestinal tumors with histologic features consistent with GIST or leiomyosarcoma were evaluated via IHC for KIT, DOG1, and desmin. A subset of tumors was additionally evaluated for reactivity for smooth muscle actin (SMA). Thirty-three tumors (60%) were diagnosed as GIST based on positive immunoreactivity for KIT or DOG1 regardless of reactivity for desmin or SMA. Most GISTs (32/33, 97.0%) had similar staining for both KIT and DOG1. DOG1 expression was identified in 2 tumors (1 study tumor and 1 additional tumor) negative for KIT and desmin that had histologic features consistent with KIT-negative, platelet-derived growth factor receptor-alpha (PDGFRA)-mutant human GISTs. Our results suggest that DOG1 has improved specificity and sensitivity to that of KIT for differentiating between canine GISTs and leiomyosarcomas. Inclusion of both DOG1 and KIT IHC in diagnostic panels will improve the accuracy of canine GIST diagnosis.

Outcome following treatment of soft tissue and visceral extraskeletal osteosarcoma in 33 dogs: 2008-2013

Extraskeletal osteosarcoma (EOS) is a rare, highly malignant mesenchymal neoplasm arising from viscera or soft tissues characterised by the formation of osteoid in the absence of bone involvement. Owing to the rarity of these neoplasms very little information exists on treatment outcomes. The purpose of this study was to describe the outcome following surgical treatment of non-mammary and non-thyroidal soft tissue and visceral EOS in dogs. Thirty-three dogs were identified; the most common primary tumour site was the spleen. Dogs that had wide or radical tumour excision had longer survival times compared with dogs that had only marginal tumour excision performed [median survival time of 90 days (range: 0-458 days) versus median survival time of 13 days (range: 0-20 days)]. The use of surgery should be considered in the management of dogs with non-mammary and non-thyroidal soft tissue and visceral EOS.

Prognostic Significance of Histologic Features in Canine Renal Cell Carcinomas

The prognostic significance of histologic and clinical features was evaluated in a retrospective study of 70 dogs treated with nephrectomy for renal cell carcinoma. Dogs presenting with hematuria and cachexia had significantly decreased overall and tumor-specific survival. Mitotic index (MI), nuclear size, nuclear pleomorphism, tumor differentiation, invasiveness, Fuhrman nuclear grade, and clear cell morphology were significantly associated with survival times (overall and tumor specific) in univariate analyses. A multivariate Cox proportional hazards model was constructed using stepwise selection to evaluate potential histologic predictor variables. This multivariate analysis revealed MI, defined as the number of mitotic figures in ten 400× fields, as the sole independent prognostic variable. Median survival for dogs with an MI >30 was 187 days compared with 1184 days for dogs with an MI of <10. Dogs with an intermediate MI of 10 to 30 had a median survival of 452 days. Canine renal carcinomas were categorized into the following subtypes based on histologic features and histochemical and immunohistochemical staining: (1) clear cell, (2) chromophobe, (3) papillary, and (4) multilocular cystic renal cell carcinomas. Clear cell carcinoma was diagnosed in 6 of 70 (9%) canine tumors and was associated with a significantly decreased median survival time. Papillary carcinomas were identified in 15 of 70 tumors (21%), chromophobe in 6 of 70 (9%), and the multilocular cystic variant of canine renal cell carcinoma in 3 of 70 tumors (4%). These findings facilitate uniform categorization of canine renal cell carcinoma and provide veterinary pathologists with criteria to determine prognostic information.

Alkaline hydrolysis of mouse-adapted scrapie for inactivation and disposal of prion-positive material

Prion diseases such as bovine spongiform encephalopathy, chronic wasting disease, and scrapie pose serious risks to human and animal health due to a host of disease-specific factors, including the resistance of infectious prions (PrP(Sc)) to natural degradation and to most commercial inactivation procedures. In an attempt to address this concern, a mouse model was used to compare the efficacy of an alkaline hydrolysis process with a simulated continuous-flow rendering treatment for disposal of PrP(Sc)-infected biological material. Female C57/BL6 mice (N = 120) were randomly divided into 4 treatment groups (n = 30), and each mouse was injected intraperitoneally with their designated treatment inoculum. Treatment groups 1 and 2 served as the positive and negative controls, respectively. Group 3 was inoculated with rendered scrapie-positive mouse brain material to investigate the effectiveness of simulated continuous-flow rendering practices to reduce or eliminate PrP(Sc). Group 4 was inoculated with hydrolyzed scrapie-positive mouse brain material to determine the sterilizing effect of alkaline hydrolysis on PrP(Sc). Mice were monitored for overt signs of disease, and those showing clinical signs were killed to prevent undue suffering. Brains were obtained from all mice that died (or were killed) and analyzed with an ELISA for the presence of PrP(Sc). Results indicated that the simulated continuous-flow rendering treatment used for preparing the rendering treatment group inoculum failed to completely eliminate PrP(Sc). Rendering delayed, but did not stop, clinical mouse-adapted scrapie transmission. Compared with positive controls, the rendering treatment group experienced an approximate 45-d average delay in days to death (250 vs. 205 d for positive controls; P < 0.0001) and a death loss of 73.9% (P = 0.0094). Positive controls suffered 100% death loss. The results validated the efficacy of the alkaline hydrolysis treatment to inactivate all PrP(Sc) because no alkaline hydrolysis treatment group mice succumbed to the disease (P < 0.0001). Based on our results, alkaline hydrolysis should be considered by the animal rendering and beef packing industries as an alternative to incineration, landfill burial, and rendering for disposing of biological material potentially infected or contaminated with prion disease.

Hyalinizing Pancreatic Adenocarcinoma in Six Dogs

Exocrine pancreatic carcinoma is a particularly malignant neoplasm of the dog. Clinical and pathologic findings of an unusual variant of exocrine pancreatic neoplasia termed hyalinizing pancreatic adenocarcinoma were evaluated in 6 dogs. On microscopic examination, neoplasms were composed of tubules and acini of epithelial cells, with bright eosinophilic granular apical cytoplasm. Tubular lumina and tumor stroma contained abundant hyaline material that resembled amyloid. The hyaline material was not congophilic, and tumor cells and hyaline material were immunohistochemically negative for amyloid A, immunoglobulin light chains (κ and λ), amylin (islet amyloid polypeptide), laminin, and α1-antitrypsin. Two patients survived longer than 15 months after diagnosis; one of these dogs was untreated and had grossly evident metastasis at the time of diagnosis. The deaths of the other 4 dogs occurred as a result of poor recovery after partial pancreatectomy or in association with other concurrent life-threatening conditions. Two dogs were diagnosed with panniculitis, a condition rarely associated with pancreatic disease. Further evaluation is needed to determine the composition and biologic significance of intratumor hyaline material. Studies that associate exocrine pancreatic carcinoma grade and histologic subtype with prognostic outcomes in the dog are warranted such that appropriate therapy can be elected.

Diagnoses and clinical outcomes associated with surgically amputated canine digits submitted to multiple veterinary diagnostic laboratories

Amputation is commonly performed to both treat and diagnose conditions affecting the digits of dogs. Although histopathologic evaluation of these digits is routinely done, data on the prevalence and prognosis of neoplasms of the digit are scarce. The records of multiple veterinary diagnostic laboratories were searched to identify submissions of amputated digits from dogs. Four hundred twenty-eight separate submissions were reviewed for diagnosis, age, sex, limb of origin, and digits affected, and the original submitting clinics were surveyed to determine clinical outcome of the animal. No diagnosis could be agreed upon in 24 animals, and these were excluded from the study. Kaplan-Meier product-limit method was used to determine the disease-free interval and survival time. Neoplastic disease was identified in 296 of 404 submissions, with exclusively inflammatory lesions composing 108 cases. A total of 30 different neoplastic processes were identified. In 233 (77.7%) of the neoplastic cases, a malignant tumor was identified. Squamous cell carcinoma was the most commonly identified tumor (n = 109, 36.3%), and 11 of 42 dogs for which clinical follow-up information was available developed metastatic disease. Squamous cell carcinoma of the digit appears to have a greater metastatic potential than that occurring elsewhere in the body. Other common diagnoses included melanoma (n = 52, 17.3%), soft-tissue sarcoma (n = 29, 9.7%), and mast cell tumor (n = 20, 6.7%). Melanomas were associated with poor prognoses, with a median survival time of 365 days.

Tetrachlorodibenzo-p-dioxin exposure alters radial arm maze performance and hippocampal morphology in female AhR +/- mice

Perinatal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been reported to alter spatial learning in rats tested on a radial arm maze (RAM). TCDD is believed to exert most of its effects through binding to the aryl hydrocarbon receptor (AhR). To determine whether the AhR mediates TCDD-induced alterations in spatial learning, we tested male and female AhR-knockout (AhR-/-), heterozygous (AhR+/-) and wild-type (AhR+/+) mice on the RAM. AhR+/- male and female mice were time mated, and treated dams were dosed with 5 microg TCDD/kg body weight on day 13 of gestation. When offspring reached adulthood, male and female AhR+/+, AhR+/- and AhR-/- mice from TCDD-exposed and unexposed litters were tested on the eight-arm RAM. After testing, we examined hippocampal morphology as visualized by the Timm's silver sulfide stain. TCDD-exposed female AhR+/- mice made more errors than their respective controls on the RAM and exhibited a decrease in the size of the intra- and infrapyramidal mossy fiber (IIP-MF) field of the hippocampus. None of the other TCDD-exposed groups differed from their respective control groups with regard to maze performance or hippocampal morphology. The reduction of IIP-MF field indicates a possible morphological basis for the learning deficit that was observed in the female AhR+/- mice. It is hypothesized that the effect of TCDD exposure is AhR dependent and that TCDD may alter GABAergic activity in the hippocampus of female mice during development.

Validation of monoclonal antibody F99/97.6.1 for immunohistochemical staining of brain and tonsil in mule deer (Odocoileus hemionus) with chronic wasting disease

A new monoclonal antibody (MAb), F99/97.6.1, that has been used to demonstrate scrapie-associated prion protein PrP(Sc) in brain and lymphoid tissues of domestic sheep with scrapie was used in an immunohistochemistry assay for diagnosis of chronic wasting disease (CWD) in mule deer (Odocoileus hemionus). The MAb F99/97.6.1 immunohistochemistry assay was evaluated in brain and tonsil tissue from 100 mule deer that had spongiform encephalopathy compatible with CWD and from 1,050 mule deer outside the CWD-endemic area. This MAb demonstrated abnormal protease-resistant prion protein (PrP(res)) in brains of all of the 100 mule deer and in 99 of the 100 tonsil samples. No immunostaining was seen in samples collected from deer outside the endemic area. MAb F99/97.6.1 demonstrated excellent properties for detection of PrP(res) in fresh, frozen, or mildly to moderately autolytic samples of brain and tonsil. This immunohistochemistry assay is a sensitive, specific, readily standardized diagnostic test for CWD in deer.

Spontaneous regression of osteosarcoma in four dogs

Spontaneous regression of primary malignant bone tumors is rare but has been reported in the human literature. To the authors' knowledge, spontaneous regression of primary bone tumors in dogs or cats has not been reported. Osteosarcoma (OSA) is the most common primary bone tumor in humans, and it has been reported that the incidence of OSA is 40 to 50 times greater in dogs than humans. In this report, high-grade OSA was diagnosed in biopsy specimens obtained from 4 dogs that subsequently underwent spontaneous regression without tumor-specific treatment. Osteosarcoma in dogs has characteristics similar to that of OSA in humans.

Evaluation of opioid receptors in synovial membranes of horses

OBJECTIVE

To evaluate mu-opioid receptors in synovial membranes of horses and determine whether these receptors are up-regulated in nerve endings during inflammation.

SAMPLE POPULATION

Synovial tissue obtained from 39 client-owned horses during arthroscopy and 14 research horses during necropsy; brain and synovial tissues were obtained during necropsy from 1 horse, and control tissues were obtained from a mouse.

PROCEDURE

Horses were classified into 7 groups on the basis of histologically determined degree of inflammation. Binding of primary rabbit antibody developed against mu-opioid receptors in equine synovial tissue was studied, using western blot analysis. Synovial membranes were tested for mu-opioid receptors by immunohistochemical staining, using a diaminobenzidine-cobalt chloride chromogen. Homogenates of synovial membranes were evaluated by use of radioligand binding.

RESULTS

Examination of western blots of equine thalamus revealed that rabbit antibody developed against mu-opioid receptors yielded a band (molecular weight, 55 kd) that corresponded with that of other opioid receptors. Use of immunohistochemical staining of synovial tissue revealed considerable staining in the proliferative lining layer and in regions surrounding vascular structures. Specific radioligand binding of tissue homogenates was found in all groups. We did not detect significant differences in binding between horses with inflammation and horses without inflammation.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of immunohistochemical analysis and radioligand binding of tissue homogenates suggest that there are opioid receptors in synovial membranes of horses. Our results support the practice of intra-articular administration of opioids to relieve pain after arthroscopic surgery in horses.

Effect of gas-plasma sterilization on the osteoinductive capacity of demineralized bone matrix

The current study evaluated the effect of low-temperature hydrogen peroxide gas plasma sterilization on the osteoinductive capability of human demineralized bone matrix using a rat model. Twelve athymic rats received three separate implants consisting of steam-sterilized demineralized bone matrix (negative control), sterile-harvest demineralized bone matrix (positive control), and gas-plasma-sterilized demineralized bone matrix. A demineralized bone matrix pellet from each sterilization group was placed individually into one of three separate soft tissue pockets created in the epaxial musculature of each rat. All 12 rats were euthanized 9 weeks after implantation. Each implantation site was removed along with 0.5-cm normal tissue around the implant. Histologic examination was done on each implant site to determine the presence or absence of new bone, cartilage, or bone marrow elements. All 12 sterile harvest demineralized bone matrix sites histologically contained new bone elements, whereas none of the negative control or gas plasma sterilized demineralized bone matrix sites contained any of these same elements. The results of this study indicate that demineralized bone matrix sterilized with low-temperature, gas-plasma sterilization loses its osteoinductive capacity in a manner similar to that of steam-sterilized demineralized bone matrix, making low-temperature, gas- plasma sterilization unsuitable as a method of secondary sterilization of demineralized bone matrix.

Accuracy of radiography, nuclear scintigraphy, and histopathology for determining the proximal extent of distal radius osteosarcoma in dogs

OBJECTIVE

To compare the accuracy of radiography, nuclear scintigraphy, and histopathology for determining the proximal extent of distal radius osteosarcoma in dogs.

STUDY DESIGN

Retrospective clinical study.

SAMPLE POPULATION

Twenty client-owned dogs taken to Colorado State University with osteosarcoma of the distal radius.

METHODS

Medical records of 20 dogs with confirmed osteosarcoma that underwent a limb-salvage procedure were reviewed. Measurements were performed directly from the lateral view of each radius, from both the scintigram and the radiograph, to determine the length of the radius and the distance from the proximal extent of the tumor to the distal radiographic or scintographic extent of the radius. The ratio of distal radial involvement to total radius length was calculated. A similar ratio was also determined using the macroslide, which included the entire portion of bone that was excised during the limb-salvage procedure. All 3 methods of measurement were compared.

RESULTS

Nuclear scintigraphy significantly overestimated tumor length when compared with macroslide specimen measurements. Radiography also overestimated tumor length, but these results were not significantly different from macroslide specimen measurements.

CONCLUSIONS

Both radiography and nuclear scintigraphy overestimate the extent of distal radius osteosarcoma in dogs when compared with histopathologic macroslides of the same lesions. Nuclear scintigraphy overestimated tumor extent to a larger degree than did radiography.

CLINICAL RELEVANCE

Although radiography is a more accurate method of measurement of the extent of distal radius osteosarcoma, because nuclear scintigraphy overestimates tumor length to a greater degree, scintigraphy may provide a larger margin of safety for determining the site of proximal osteotomy during a limb-salvage procedure. However, caution should be taken when utilizing scintigraphy, because this method may overestimate length of radius involved to such an extent as to cause the surgeon to believe that a patient is not a suitable limb-salvage candidate.

Clinical outcome of dogs with grade-II mast cell tumors treated with surgery alone: 55 cases (1996-1999)

OBJECTIVE

To determine outcome for dogs with grade-II mast cell tumors treated with surgery alone.

DESIGN

Retrospective study.

ANIMALS

55 dogs.

PROCEDURES

Medical records were examined, and signalment; location and size of tumor; staging status; dates of local recurrence, metastasis, death, or last follow-up examination; status of surgical margins; previous surgery; postoperative complications; and cause of death were recorded. Follow-up information was obtained via reexamination or telephone conversations with owners or referring veterinarians. Univariate analysis was performed to identify prognostic factors.

RESULTS

60 tumors in 55 dogs were included. Median follow-up time was 540 days. Three (5%) mast cell tumors recurred locally; median time to local recurrence was 62 days. Six (11%) dogs developed another mast cell tumor at a different cutaneous location; median time to a different location was 240 days. Three (5%) dogs developed metastases; median time to metastasis was 158 days. Fourteen dogs died; 3 deaths were related to mast cell tumor, and 7 were unrelated. The relationship with mast cell tumor was not known for 4. Median survival times were 151, 841, and 827 days, respectively, for these 3 groups. Forty-six (84%) dogs were free of mast cell tumors during the study period. A reliable prognostic factor could not be identified.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that additional local treatment may not be required after complete excision of grade-II mast cell tumors and that most dogs do not require systemic treatment.

Treatment with a combination of doxorubicin, surgery, and radiation versus surgery and radiation alone for cats with vaccine-associated sarcomas: 25 cases (1995-2000)

OBJECTIVE

To compare use of doxorubicin, surgery, and radiation versus surgery and radiation alone for treatment of cats with vaccine-associated sarcoma.

DESIGN

Retrospective study.

ANIMALS

25 cats with vaccine-associated sarcomas.

PROCEDURE

Time to first recurrence and survival time were compared between the 2 treatment groups. The number of surgeries (1 or > 1) were compared with respect to time to first recurrence and survival time.

RESULTS

Median time to first recurrence was 661 days for the group that received doxorubicin, surgery, and radiation. Median time to first recurrence has not yet been attained for the group treated with surgery and radiation alone. Median survival time was 674 days for the group treated with doxorubicin, surgery, and radiation and 842 days for the group treated with surgery and radiation alone. For time to first recurrence and survival time, significant differences were not detected between cats that had 1 surgery and those that had > 1 surgery.

CONCLUSIONS AND CLINICAL RELEVANCE

Significant differences between the 2 treatment groups were not detected. The efficacy of doxorubicin in the treatment of vaccine-associated sarcomas is uncertain.

Surgical treatment of adrenocortical tumors: 21 cases (1990-1996)

Twenty-four adrenocortical tumors were surgically removed from 21 dogs. Histopathological examination confirmed 18 carcinomas and six adenomas. Four dogs died in the perioperative period. Fifteen of the 17 dogs that survived the perioperative period had long-term resolution of their clinical signs. Two dogs with incompletely resected tumors were treated with mitotane to control their clinical signs. Overall median Kaplan-Meier life-table survival for dogs with carcinomas was 778 days (range, one to 1,593 days). Median survival for dogs with adenomas was not reached (range, 11 to 730 days). Histopathological diagnosis, histopathological cellular features, age of the dog, and tumor size were not prognostic of outcome.

Response of feline oral squamous cell carcinoma to palliative radiation therapy

Seven cats with advanced oral squamous cell carcinoma were treated with palliative radiotherapy. Megavoltage radiation in 8 Gray (Gy) fractions was delivered on days 0, 7, and 21 for a total dose of 24 Gy. Treatment field included the mandible, oropharynx, retropharyngeal lymph nodes, and tonsils. Adjuvant treatment with chemotherapy was variable. Age ranged from 13 to 18 years old with a median age of 15 years. Three of the seven cats (43%) did not complete treatment. Six cats were euthanized due to tumor growth and/or radiation side effects with a median survival time of 60 days (range = 42 to 97 days, mean = 63 +/- 8.4 days). Radiotherapy complications or progression of disease occurred in 6 of 7 (85.7 %) cats and included adverse clinical signs, such as mucositis, serosanguinous oral discharge, pain, and dysphagia. These data suggest that coarse fractionation radiotherapy did not result in palliation in cats with inoperable oral squamous cell carcinoma.

Identification of matrix metalloproteinases in canine cutaneous mast cell tumors

Presence of matrix metalloproteinases has been associated with tumor invasion and metastasis in human neoplasia. The presence of matrix metalloproteinase 2 and matrix metalloproteinase 9 was determined in canine mast cell tumor tissue and normal stromal tissue from 24 dogs with spontaneously occurring cutaneous mast cell tumors. Seventeen of the mast cell tumors were of histologic grade 2, and 7 were of histologic grade 3. Gelatin zymography and computer assisted densitometry image analysis were used to quantify matrix metalloproteinase concentration. Bands from canine tissues migrated in the same location as human proenzyme and active enzyme matrix metalloproteinase 2 and matrix metalloproteinase 9 standards. A semiquantitative value for each patient sample was obtained by comparing the optical assessment density of each unknown band to the optical density of the human standard. The presence of matrix metalloproteinase 2 and matrix metalloproteinase 9 in histologic grade 2 mast cell tumors and histologic grade 3 mast cell tumors was compared, as was presence of matrix metalloproteinases in tumor and stromal tissue. There was dramatically more proenzyme matrix metalloproteinase 9 activity in histologic grade 3 mast cell tumors when compared to grade 2 tumors (P = .03). There was also dramatically more active enzyme matrix metalloproteinase 2 and active enzyme matrix metalloproteinase 9 activity in tumor tissue compared to stromal tissue (P = .02, P < .0001). This study demonstrates that the proenzyme and active enzyme forms of matrix metalloproteinase 2 and matrix metalloproteinase 9 are present in canine mast cell tumors. This appears to be related to the degree of histologic malignancy, although histologic grade 1 tumors were not evaluated.

Radial arm maze performance in rats following gestational and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

Recently, we reported that in utero and lactational exposure to 2,3, 7,8-tetrachlorodibenzo-p-dioxin (TCDD) resulted in a task-specific reduction of errors on the radial arm maze (RAM), without similar improvements on other spatial learning tasks including the Morris water maze. The effect was more pronounced in males than in females. This study further investigated the effects of in utero and lactational exposure to TCDD on RAM performance by testing male and female TCDD-exposed rats on either an eight-arm RAM with all arms baited or a 12-arm RAM with 8 of the 12 arms baited. If the rats have improved spatial learning or memory on the RAM, then they should be improved on both RAM tasks; whereas, if they are using adjacent arm selection or some other response strategy to solve the task, they should not show enhanced performance on the 12-arm RAM where not all the arms are rewarded. Time-mated Sprague-Dawley dams were gavaged with corn oil vehicle or one of two doses of TCDD in vehicle (0.1 or 0.2 microg/kg body weight) on gestational days 10 to 16. Litters were culled to eight on day 2 and weaned on day 21. Beginning on day 80, one male and female from each litter was tested on the eight-arm RAM with all arms baited. As in our previous studies, the 0.1-microg/kg TCDD-exposed male rats showed a significant decrease in the number of errors. However, the 0.2-microg/kg males did not differ from the controls. Neither group of TCDD-exposed females differed from the controls. None of the TCDD-exposed rats differed from the controls in adjacent arm selection behavior. An additional male and female from each litter were tested on the 12-arm RAM with only 8 of the 12 arms baited. In this task, neither TCDD group differed from the controls. These results suggest that the reduction of errors on the eight-arm RAM may be due to increased response patterning or use of intramaze cues rather than to improved spatial learning or memory. Also, the reduction in errors was only present at the lower dose of TCDD suggesting that the improvement in performance is only present at very low, nonovertly toxic doses of TCDD.

Fracture healing after stabilization with intramedullary xenograft cortical bone pins: a study in pigeons

OBJECTIVE

To investigate the effectiveness of intramedullary xenograft cortical bone pins compared with stainless steel Kirschner wire for the repair of a standardized avian humeral fracture.

STUDY DESIGN

Prospective randomized study.

SAMPLE POPULATION

Thirty mature pigeons (Columba livia).

METHODS

Birds were randomly assigned to 3 groups. Transverse mid-diaphyseal humeral fractures were created in 1 humerus in each bird. Fractures were stabilized with intramedullary ostrich or canine xenograft cortical bone pins or Kirschner wire. Radiographic, histological, and biomechanical assessments were used to compare fracture healing 6 weeks after fracture stabilization. The contralateral humerus of each bird was used as a control.

RESULTS

All fractures healed regardless of intramedullary pin type. There were no statistically significant biomechanical differences among groups or within groups. Xenograft cortical bone pins induced a mononuclear inflammatory reaction that did not impair bone healing. Bones stabilized with intramedullary cortical bone pins had more periosteal callus and inflammation at the fracture site than bones stabilized with stainless steel Kirschner wires.

CONCLUSIONS

Intramedullary xenograft cortical bone pins, derived from mammalian or avian sources, appear to represent an alternative for the repair of avian humeral fractures.

CLINICAL RELEVANCE

Intramedullary xenograft cortical bone pins are biodegradable and may reduce the need for additional surgery to remove implants after fracture healing.

Comparison of bone healing by demineralized bone matrix and autogenous cancellous bone in horses

OBJECTIVE

The purpose of this study was to compare bone healing induced by equine demineralized bone matrix (DBM) to autogenous cancellous bone graft (ACB) or no graft (control) in a rib-defect model in horses.

STUDY DESIGN

The osteogenic properties of ACB and DBM were evaluated in bilateral 19-mm circular defects created in the outer cortex of the 6th and 8th ribs of each horse.

ANIMALS OR SAMPLE POPULATION

Eight mature horses.

METHODS

Three rib defects in each horse were randomly treated with each of the 3 treatment groups, and the fourth rib defect received a random treatment. Rib sections, including the defects, were harvested 56 days after implantation and examined for bone mineral density, percent ash and calcium and graded for signs of radiographic and histological healing.

RESULTS

All ribs were fractured at the defect site and were classified as nonunion fractures 56 days after implantation. There were no significant differences among groups in bone mineral density and signs of radiographic or histological healing. There was an increased volume of bone in control and ACB-treated sites compared with DBM-treated sites. Rib defects treated with ACB were significantly higher in percent ash and calcium than those treated with DBM. DBM elicited no inflammatory reaction, and remodeling occurred around the periphery and within vascular channels of the decalcified particles.

CONCLUSION

DBM particles remodel from the periphery, which may explain the significantly lower percent ash, calcium, and bone when compared with ACB, because 2- to 4-microL pieces of DBM may act as space-occupying masses until completely mineralized. There was no evidence of enhanced healing associated with the use of DBM in this model.

CLINICAL RELEVANCE

Particles of 2 to 4 mm DBM should not be used as an aid to fracture repair because particles of this size interfere with normal mineralization. However, our model of nonunion fracture healing may be useful in future studies.

Outcome following treatment of vertebral tumors in 20 dogs (1986-1995)

Twenty dogs with histopathologically confirmed primary (n=15) or metastatic (n=5) osteosarcoma (n=14) or fibrosarcoma (n=6) of the vertebral column were treated with surgery (n=4), radiation therapy and chemotherapy (n=6), surgery and chemotherapy (n=2), or surgery, radiation, and chemotherapy (n=8). All dogs died due to their disease; 15 died due to local failure, and five died due to nonvertebral metastasis. Overall median survival time was 135 days, with a range of 15 to 600 days. Of the factors evaluated, only postoperative neurological status had a significant influence on outcome by multivariate analysis. This study supports the overall guarded prognosis for dogs with vertebral neoplasia. Better combinations of surgery, chemotherapy, and radiation therapy remain to be defined for this difficult subset of animal cancer.

Identification of matrix metalloproteinases in canine neoplastic tissue

OBJECTIVE

To identify matrix metalloproteinases (MMP) 2 and 9 in canine tumor tissue and to compare the amount of activity to that in unaffected stromal tissue.

ANIMALS

30 dogs with spontaneously developing, high-grade osteosarcoma.

PROCEDURE

Tumor and nearby stromal tissue (muscle) were obtained at the time of surgery. Specimens were homogenized, and supernatants were assayed, using gelatin zymography. Human derived standards were run concurrently. Densitometry was done to obtain a semiquantitative arbitrary unit value for each specimen. The amount of activity in tumor tissue was compared with the amount in stromal tissue.

RESULTS

Gelatinolytic bands were observed from the analysis of all tumor tissues and in most stromal tissues. These bands migrated in the same molecular weight area as the human MMP 2 and 9 standards. Gelatinolytic activity could be quenched by the addition of 50 mM EDTA and 1 microg of synthetic tissue inhibitor of metalloproteinase (TIMP) 2 per 100 ml. There was significantly more gelatinolytic activity in tumor tissue than in stromal tissue.

CONCLUSIONS AND CLINICAL RELEVANCE

MMP 2 and 9 are detectable in canine neoplastic tissue. Matrix metalloproteinases activity in tumor tissue is higher than in unaffected stromal tissue, indicating that canine MMP may be involved in the pathogenesis of tumor growth and metastasis.

The treatment of high-grade soft tissue sarcomas with preoperative thermoradiotherapy

PURPOSE

To explore the use of a novel program of preoperative radiation and hyperthermia in the management of high-grade soft tissue sarcomas (STS).

METHODS AND MATERIALS

Eligible patients were adults over 18 with Grade 2 or 3 STS, surgically resectable without a local excision prior to referral to Duke University Medical Center and without distant metastases. Patients were staged generally with CT and/or MR imaging. The diagnosis was established with fine needle aspiration or incisional biopsy. Patients were then treated with 5000 to 5040 cGy, 180-200 cGy per fraction. Chemotherapy was usually not employed. Generally two hyperthermia treatments per week were given with a planned thermal dose of 10-100 CEM 43 degrees T90. Invasive thermometry and thermal mapping were done in all patients. Surgical resection was planned 4-6 weeks after the completion of radiation and hyperthermia.

RESULTS

Ninety-seven patients were treated on study between 1984 and 1996. Follow-up ranged from 12 to 155 months (median 32). All tumors were high-grade in nature, 44 greater than 10 cm in size (maximum tumor diameter), 43 5-10 cm in size, 10 less than 5 cm. Seventy-eight of the 97 tumors were located in an extremity. Of the 97 patients, 48 remain alive and continually free of disease following initial therapy. Of the remaining 49 patients, 44 have relapsed (34 dead, 10 living with disease), 3 have died secondary to complications of therapy, and 2 have died of unrelated causes. Ten-year actuarial overall survival, cause-specific survival, and relapse-free survival are 50, 47, and 47% respectively. The predominant pattern of failure has been distant metastases with only 2 patients developing local failure alone. Ten-year actuarial local control for extremity tumors is 94%, 63% for the 19 patients with tumors at sites other than the extremity. Of the 78 patients with extremity lesions, 63 have had limb preservation and remain locally controlled. Overall 38 patients experienced 57 major complications. There were 3 deaths, one due to adriamycin cardiomyopathy and two secondary to wound infections. Four patients required amputation secondary to postoperative wound healing problems. Complications directly attributable to hyperthermia occurred in 15 patients with 11 instances of second- or third-degree burns and two instances of subcutaneous fat necrosis. The hyperthermia complications were generally not severe and either healed readily or were excised at the time of surgical resection of the primary tumor.

CONCLUSIONS

For these aggressive high-grade soft tissue sarcomas, this treatment program of preoperative thermoradiotherapy provided excellent local regional control for extremity lesions (95%) and satisfactory local regional control (63%) of nonextremity sarcomas, but did not appear to influence the rate of distant metastases or survival. Complications were frequent but apart from the direct thermal burns, not too different from those reported for preoperative radiotherapy alone. More effective adjuvant systemic therapy is necessary to impact favorably on survival.

Long-term adverse effects of radiation inhibition of restenosis: radiation injury to the aorta and branch arteries in a canine model

PURPOSE

To determine the long-term effects of irradiation on large arteries in view of the possible use of radiation to prevent restenosis after angioplasty.

METHODS AND MATERIALS

Groups of dogs received 10-55 Gy single-dose alone, or in combination with 50 Gy in 2-Gy fractions, or 50-80 Gy in 2-2.7-Gy fractions to an 8-cm length of aorta and branch arteries. Single doses were delivered intraoperatively. Two or 5 years after irradiation, aortas and branch arteries were evaluated histomorphometrically to determine areas of intima, media, and adventitia, and qualitatively to determine other adverse effects.

RESULTS

Intimal area increased at single doses < 20 Gy and after all fractionated doses, but was normal at doses > 20 Gy 2 years after irradiation. Intimal area was greater at 5 years than at 2 years after irradiation. Adventitial area increased with increasing dose at 2 and 5 years after irradiation. Thrombosis of the aorta and branch arteries occurred at 4-5 years after irradiation with ED50s of 29.7 Gy and about 25 Gy, respectively, but did not occur after fractionated irradiation.

CONCLUSION

Intimal proliferation is inhibited at single doses > 20 Gy, but may be stimulated at single doses of < 20 Gy or after fractionated irradiation. Adventitial fibrosis increases with increasing dose and could contribute to adverse late vascular remodeling. Severe adverse effects were not evident until 4-5 years after irradiation at does of > 20 Gy to an 8-cm vessel length.

Use of whole body hyperthermia as a method to heat inaccessible tumours uniformly: a phase III trial in canine brain masses

In this study, whole body hyperthermia (WBH) was assessed as a means of heating intracranial tumours uniformly. Twenty-five dogs received radiation therapy and 20 the combination of radiation and WBH. Total radiation dose was randomly assigned and was either 44, 48, 52, 56 or 60 Gy. Because of WBH toxicity, intercurrent disease or tumour progression, seven of the 45 dogs received less than the prescribed radiation dose. For WBH, the target rectal temperature was 42 degrees C for 2h and three treatments were planned. In five of the 20 dogs randomized to receive WBH, only one WBH treatment was given because of toxicity. WBH toxicity was severe in six dogs, and resulted in death or interruption in treatment. Most tumours did not undergo a complete response, making it impossible to differentiate tumour recurrence from brain necrosis as a cause of progressive neuropathy. Therefore, survival was the major study endpoint. There was no survival difference between groups. One-year survival probability (95% CI) for dogs receiving radiation therapy alone was 0.44 (0.25, 0.63) versus 0.40 (0.19, 0.63) for dogs receiving radiation and WBH. There was no difference in the incidence of brain necrosis in the two treatment groups. Results suggest that use of WBH alone to increase the temperature of intracranial tumours as a means to improve radiation therapy outcome is not a successful strategy.

Arthroscopic subchondral bone plate microfracture technique augments healing of large chondral defects in the radial carpal bone and medial femoral condyle of horses

OBJECTIVE

To evaluate the effect of arthroscopic subchondral bone microfracture on healing of large chondral defects in horses.

STUDY DESIGN

Short- (4 months) and long-term (12 months) in vivo experimental chondral defect model.

ANIMALS

10 horses, aged 2 to 5 years.

METHODS

Each horse had a 1 cm2 full-thickness chondral defect created in both radial carpal bones and both medial femoral condyles. One carpus and one femoral condyle of each horse had the subchondral bone plate under the defect perforated using an orthopedic awl. All horses were exercised, five horses were evaluated after 4 months and five horses after 12 months. Gross, histologic, and histomorphometric examination of defect sites and repair tissues was performed, as was collagen typing of the repair tissue.

RESULTS

On gross observation a greater volume of repair tissue filled treated defects (74%) compared with control defects (45%). Histomorphometry confirmed more repair tissue filling treated defects, but no difference in the relative amounts of different tissue types was observed. There was an increased percentage of type II collagen in treated defects compared with control defects and evidence of earlier bone remodeling as documented by changes in porosity.

CONCLUSIONS

In full-thickness chondral defects in exercised horses, treatment with subchondral bone microfracture increased the tissue volume in the defects and the percentage of type II collagen in the tissue filling the defects when compared to nontreated defects.

CLINICAL RELEVANCE

No negative effects of the microfracture technique were observed and some of the beneficial effects are the basis for recommending its use in patients cases with exposed subchondral bone.

Effects of intraoperative irradiation (IORT) and intraoperative hyperthermia (IOHT) on canine sciatic nerve: histopathological and morphometric studies

PURPOSE/OBJECTIVE

Peripheral neuropathies have emerged as the major dose-limiting complication reported after intraoperative radiation therapy (IORT). The combination of IORT with hyperthermia may further increase the risk of peripheral nerve injury. The objective of this study was to evaluate histopathological and histomorphometric changes in the sciatic nerve of dogs, after IORT with or without hyperthermia treatment.

METHODS AND MATERIALS

Young adult beagle dogs were randomized into five groups of 3-5 dogs each to receive IORT doses of 16, 20, 24, 28, or 32 Gy. Six groups of 4-5 dogs each received IORT doses of 12, 16, 20, 24, or 28 Gy simultaneously with 44 degrees C of intraoperative hyperthermia (IOHT) for 60 min. One group of dogs acted as hyperthermia-alone controls. Two years after the treatment, dogs were euthanized, and histopathological and morphometric analyses were performed.

RESULTS

Qualitative histological analysis showed prominent changes such as focal necrosis, mineralization, fibrosis, and severe fiber loss in dogs which received combined treatment. Histomorphometric results showed a significantly higher decrease in axon and myelin and small blood vessels, with a corresponding increase in connective tissue in dogs receiving IORT plus hyperthermia treatment. The effective dose for 50% of nerve fiber loss (ED50) in dogs exposed to IORT only was 25.3 Gy. The ED50 for nerve fiber loss in dogs exposed to IORT combined with IOHT was 14.8 Gy. The thermal enhancement ratio (TER) was 1.7.

CONCLUSION

The probability of developing peripheral neuropathies in a large animal model is higher when IORT is combined with IOHT, when compared to IORT application alone. To minimize the risk of peripheral neuropathy, clinical treatment protocols for the combination of IORT and hyperthermia should not assume a thermal enhancement ratio (TER) to be lower than 1.5.

Intermuscular lipomas of the thigh region in dogs: 11 cases

Ten dogs with intermuscular lipomas in the thigh region were treated by surgical resection. The masses were located predominantly between the semitendinosus and semimembranosus muscles and involved the full length of the femur. These lipomas were not infiltrative but located deep between the fascial planes of the associated muscles. These tumors can appear similar to soft-tissue sarcomas in this location, but they can be differentiated by cytology and histology. Differentiation from an infiltrative lipoma is predominantly determined at the time of surgery. No tumors recurred in the median follow-up period of 17 months.

Comparison of the effects of asparaginase administered subcutaneously versus intramuscularly for treatment of multicentric lymphoma in dogs receiving doxorubicin

OBJECTIVE

To determine the effectiveness and safety of asparaginase administered s.c. versus i.m. for treatment of multicentric lymphoma in dogs receiving doxorubicin.

DESIGN

Prospective study.

ANIMALS

49 dogs with multicentric lymphoma.

PROCEDURE

Dogs were treated with doxorubicin every 3 weeks, for a total of 5 treatments, and were given 3 weekly treatments of asparaginase, s.c. or i.m. Using high-performance liquid chromatography, mean plasma asparagine, aspartic acid, glutamine, and glutamic acid concentrations were determined in dogs before and during treatment with asparaginase (10,000 U/m2 of body surface area, once a week for 3 weeks). Asparaginase was administered s.c. in 23 dogs and i.m. in 26 dogs. Variables evaluated included time to response to chemotherapy, remission and survival times, and clinical and serum biochemical indicators of toxicoses.

RESULTS

Using the World Health Organization's staging system for lymphoma, 30 dogs were in clinical stage III and 19 were in clinical stage IV. One week after asparaginase treatment, plasma asparagine concentrations were low and plasma aspartic acid, glutamine, and glutamic acid concentrations were high. Differences in plasma amino acid concentrations were not found between s.c. and i.m. groups. For dogs in clinical stage IV, i.m. administration of asparaginase significantly decreased the number of days to complete remission, compared with s.c. administration (8 vs 17 days, respectively). For dogs in clinical stage III, i.m. administration favorably increased the duration of first remission (191 vs 103 days) and survival time (289 vs 209 days). Overall, dogs treated i.m. had a faster response to chemotherapy (9 vs 15 days), a longer remission (191 vs 109 days), and a longer survival time (286 vs 198 days), compared with all dogs treated s.c. Asparaginase toxicoses were not observed regardless of the route of administration.

CLINICAL IMPLICATIONS

For dogs with multicentric lymphoma that are receiving doxorubicin, i.m. treatment with asparaginase is more effective than s.c. treatment.

Effects of 6alpha-methylprednisolone acetate on an equine osteochondral fragment exercise model

OBJECTIVE

To determine effects of intra-articularly administered 6alpha-methylprednisolone acetate (MPA) in exercised horses with carpal osteochondral fragmentation.

ANIMALS

18 horses: 3 groups of 6 each.

PROCEDURE

An osteochondral (chip) fragment was created in 1 randomly chosen middle carpal joint of each horse. Polyionic fluid (PF) was injected into both middle carpal joints of horses in the control group. In horses of the MPA-control group, MPA was injected into the middle carpal joint without an osteochondral fragment; a similar volume of PF was injected into the contralateral middle carpal joint. In the MPA-treated group of horses, 100 mg of MPA was injected into the middle carpal joint containing the osteochondral fragment; a similar volume of PF was injected into the contralateral joint. Injections were administered on postsurgical days 14 and 28, and horses were exercised on a high-speed treadmill for 8 weeks, starting on postsurgical day 15.

RESULTS

Clinical improvement in degree of lameness was not associated with MPA administration. Joints that contained an osteochondral fragment and were treated with MPA had lower prostaglandin E2 concentration in synovial fluid, and lower scores for intimal hyperplasia and vascularity in synovial membrane, compared with PF-treated joints. However, articular cartilage erosion and morphologic lesions suggested possible deleterious effect of intra-articular MPA administration.

CONCLUSIONS

Some beneficial effects of MPA administration on synovial fluid and synovial membrane were identified; however, the deleterious findings contrast with those associated with triamcinolone acetonide used in a similar model, but agree with other results of MPA administration in normal and abnormal joints.

Apparent interaction of dimethyl sulfoxide with cisplatin released from polymer delivery devices injected subcutaneously in dogs

Local tissue toxicity, systemic toxicity and platinum pharmacokinetics were evaluated in 6 normal healthy beagle dogs injected subcutaneously with two formulations of a polylactide biodegradable polymer (Atrigel) system containing cisplatin. Dogs were injected 4 times at 30 day intervals at platinum dosages of 70, 105 and 157.5 mg/m2 (dose escalation). Once pharmacokinetics were established, 29 dogs with spontaneous stage IIb appendicular osteosarcoma were treated with 4 injections of the same polymer system containing cisplatin at 70 mg/m2 (20 dogs) and 100 mg/m2 (9 dogs) to establish efficacy against micrometastatic disease. Local tissue toxicity was variable. Systemic toxicity, as judged by clinicopathologic evaluation was not noted at any dose level or injection number. Interim (6 month) survival analysis revealed a median disease-free interval of 180 days. Consistent platinum release characteristics were found, however, the lack of toxicity and decreased disease-free-interval raised concerns over the biologic activity of the cisplatin. Prior to completion of the study, it was discovered that dimethyl sulfoxide, the solvent used in the co-polymer system, may be responsible for biologic inactivation of cisplatin. This was subsequently demonstrated in tissue culture assays. The clinical trial was suspended and dogs were treated with traditional chemotherapy.

Prognostic importance of alkaline phosphatase activity in serum from dogs with appendicular osteosarcoma: 75 cases (1990-1996)

OBJECTIVE

To determine whether alkaline phosphatase activity in dogs with appendicular osteosarcoma can be used as a prognostic indicator.

DESIGN

Retrospective study.

ANIMALS

75 dogs with appendicular osteosarcoma.

PROCEDURE

Serum total alkaline phosphatase (TALP) and bone-specific alkaline phosphatase (BALP) activities were determined from archival serum samples obtained at various times during treatment of appendicular osteosarcoma and follow-up evaluations. Associations among activities of TALP and BALP and survival and disease-free intervals, percentage of bone length involved with tumor, histologic subtype, and method of surgical treatment were evaluated.

RESULTS

High activities of TALP and BALP before surgery were significantly associated with shorter survival and disease-free intervals in dogs undergoing surgery (amputation or limb-sparing procedure) and adjuvant chemotherapy. Activity of BALP significantly decreased in 29 dogs for which postoperative samples were available. Failure of BALP activity to decrease after surgery was correlated with shorter survival and disease-free intervals.

CLINICAL IMPLICATIONS

Activities of TALP and BALP in serum are important prognostic factors for appendicular osteosarcoma in dogs. Prognostic factors may help clinicians initiate more aggressive treatment for dogs that are at higher risk of death or relapse.

Radiofrequency (electrosurgical) ablation of articular cartilage: a study in sheep

The objective of this study was to examine the effect of a bipolar ablation probe on experimentally roughened articular cartilage and compare it with the traditional mechanical shaving technique using the knee joint of sheep. Twenty-eight skeletally mature ewes were divided randomly into two groups: one group was treated with a rotating shaving device and another group was treated using the bipolar ablation probe (Bipolar Arthroscopic Probe; Electroscope, Inc, Boulder, CO). Animals were killed at 0, 6, 12, and 24 weeks, and histological sections of the experimental limbs were compared with sections of the opposite limb using a modified Mankin scale. The following variables were used to determine scores: surface (0-6), cells (0-4), hypocellularity (0-3), matrix staining (transitional zone [0-4], radiate zone [0-4], and focal empty lacunae or hypereosinophilic cells (0-3). Differences in scores for all response variables were calculated as treated limb minus sham limb. Response variables were formed: score >0 recoded as 1 (favorable response treated better than sham), score of 0 recoded as 2 (neutral response no differences), and score <0 recoded as 3 (unfavorable response treated worse than sham). Bipolar ablative probe-treated limbs had 14.29% favorable responses and 35.71% favorable or neutral responses, whereas shave-treated limbs had 0% favorable and only 7.14% favorable or neutral responses. For all variables, bipolar ablative probe-treated limbs had more favorable responses. The less severe histological change in the bipolar ablative probe-treated joints compared with the shave-treated joints suggests that bipolar ablation of articular cartilage may be a better treatment for chondromalacia than the usual shaving methods of debridement. Further, there were no pathological changes in the subchondral bone.

Limb salvage surgery for osteosarcoma of the proximal humerus: outcome in 17 dogs

OBJECTIVE

To describe function and identify factors that affect outcome in dogs undergoing limb salvage surgery for osteosarcoma (OS) of the proximal humerus.

STUDY DESIGN

A retrospective study of dogs in which OS of the proximal humerus was treated with limb salvage surgery.

ANIMALS

17 client-owned dogs.

METHODS

Records were analyzed for functional outcome, recurrence, metastasis, and survival.

RESULTS

Outcome was good to excellent in 12% of dogs. Recurrence, metastasis, and survival were significantly affected by completeness of surgical margins. Double plating of the distal allograft-host junction significantly reduced frequency of biomechanical failure.

CONCLUSIONS

Limb salvage surgery for OS of the proximal humerus did not result in acceptable function and was fraught with postoperative complications. Outcome was significantly affected by completeness of surgical margins.

CLINICAL RELEVANCE

Limb salvage surgery for OS of the proximal humerus in dogs cannot be recommended until improvement in functional outcome and reduction in postoperative complications can be achieved. The dependence of outcome on completeness of surgical margins supports aggressive en bloc resection and marking and evaluating surgical margins.

Volume effects in the irradiated canine spinal cord: do they exist when the probability of injury is low?

PURPOSE

The purpose of this study was to investigate volume effects in the irradiated canine spinal cord.

MATERIALS AND METHODS

Eighty-nine beagle dogs were given 44-84 Gy photons in 4 Gy fractions to 4 or 20 cm lengths of thoracic spinal cord. As controls, 36 dogs were given 60-84 Gy in 2 Gy fractions to a 20 cm length of spinal cord and six dogs were unirradiated. Dogs were evaluated for clinical signs, and after euthanasia, for occurrence of gross lesions, severe lesions of massive hemorrhage, white matter necrosis and/or parenchymal atrophy and mild lesions of focal fiber loss. White matter vacuoles, meningeal thickness and dorsal root ganglia lesions were quantified. Data were analyzed to test for an effect of volume on dose-response curves.

RESULTS

Significant volume effects were found between 4 and 20 cm lengths of irradiated spinal cord for gross lesions, severe lesions and mild lesions (8.3-15.0 Gy difference at the ED50 level). The ED50 in 4 Gy fractions for severe lesions was 56.9 Gy (95% CI 53.1-60.6) for 20 cm and 68.8 Gy (95% CI 64.5-75.1) for 4 cm fields. Significant improvements in the fit of data to dose-response curves resulted when using models with either parallel or non-parallel curves, but in either case an appreciable difference existed between curves at low probabilities of injury. Volume effects were present for meningeal thickness and slopes of dose-response curves were different. Clinical signs correlated well with severe lesions for 20 cm (ED50 = 54.0 Gy), but not for 4 cm fields (ED50 = 77.6 Gy).

CONCLUSIONS

Volume effects exist for the occurrence of pathologic lesions in irradiated canine spinal cord. Clinical compensation for pathologic lesions occur at small, but not large irradiated volumes. There is insufficient data to support a decreased slope of dose-response curves with decreased volume. Volume effects estimated at the 50% level of spinal cord injury could also hold at low probabilities of injury characteristic of the clinic.

Tumor biology and pathology

The correct pathologic diagnosis of tumor type affecting the veterinary patient is of utmost importance to the veterinary surgical oncologist. The surgical oncologist may be presented with benign or malignant diseases, and an accurate pathologic diagnosis may be necessary to distinguish between the two conditions. In either case, assessment of surgical margins to determine completeness of surgical removal is necessary. In cases of malignancy, the pathologist should grade the tumor, if appropriate, and be able to perform specialized techniques, such as immunohistochemistry, if a diagnosis is in question. The surgical oncologist needs to understand the principles of tissue collection, fixation, and submission to help the pathologist provide an accurate diagnosis. Finally, the oncologic surgeon and surgical pathologist need to establish a cooperative working relationship and function as a team to discuss difficult cases. This will ensure the best treatment for the veterinary patient.

Principles of treatment for soft tissue sarcoma

Soft tissue sarcomas (STS) are mesenchymal tumors arising from connective tissue elements and are grouped together based on a common biologic behavior. The most common histologic types include malignant peripheral nerve sheath tumors (schwannoma and neurofibrosarcoma) "hemangiopericytoma," fibrosarcoma, and malignant fibrous histiocytoma. These tumors are relatively slow growing yet locally invasive with a high rate of recurrence following conservative management. Appropriate preoperative planning and aggressive surgical resection often result in long-term remission or cure. Identification and evaluation of resection margins are paramount in appropriate case management. The addition of radiotherapy after surgical resection can aid in remission for incompletely resected masses. Systemic chemotherapy for STS should be considered for high-grade tumors with a moderate metastatic potential. Potential prognostic factors include grade, resection margins, size, location, histologic type, and previous treatment, with grade and margins being the most important. Tumor types classified as STS that differ slightly in their presentation or treatment, including synovial cell sarcoma, rhabdomyosarcoma, liposarcoma, and vaccine-associated STS in cats, are discussed. Soft tissue sarcomas can be a frustrating disease to treat, but adherence to solid surgical oncology principles can greatly increase the odds of good disease control.