Alastair R. Coomer

Radiation therapy for canine appendicular osteosarcoma.

Radiation therapy (RT) for the management of canine appendicular osteosarcoma (OSA) can be described as either palliative- or curative intent. Palliative RT uses coarsely fractionated external beam RT or radiopharmaceuticals to provide relief of pain and lameness associated with OSA while resulting in minimal, if any, radiation-induced acute adverse effects. Limb amputation and chemotherapy are considered (together) the standard of care for curative-intent treatment of canine appendicular OSA. When limb amputation is not possible, RT can be used for limb sparing and is supplemented with chemotherapy for presumed micrometastatic disease. Fractionated tumour irradiation with curative intent appears to be ineffective and local disease control can more likely be achieved when stereotactic radiosurgery or intra-operative extracorporeal irradiation is combined with strict case selection and adjunctive chemotherapy. The availability of limb-sparing RT is limited by experience and availability of specialised equipment. When planned and administered appropriately, radiation-associated adverse effects are often mild and self-limiting.

Effect of bevacizumab on angiogenesis and growth of canine osteosarcoma cells xenografted in athymic mice

Objective-To investigate the effects of bevacizumab, a human monoclonal antibody against vascular endothelial growth factor, on the angiogenesis and growth of canine osteosarcoma cells xenografted in mice. Animals-27 athymic nude mice. Procedures-To each mouse, highly metastasizing parent osteosarcoma cells of canine origin were injected into the left gastrocnemius muscle. Each mouse was then randomly allocated to 1 of 3 treatment groups: high-dose bevacizumab (4 mg/kg, IP), low-dose bevacizumab (2 mg/kg, IP), or control (no treatment). Tumor growth (the number of days required for the tumor to grow from 8 to 13 mm), vasculature, histomorphology, necrosis, and pulmonary metastasis were evaluated. Results-Mice in the high-dose bevacizumab group had significantly delayed tumor growth (mean ± SD, 13.4 ± 3.8 days; range, 9 to 21 days), compared with that for mice in the low-dose bevacizumab group (mean ± SD, 9.4 ± 1.5 days; range, 7 to 11 days) or control group (mean ± SD, 7. 2 ± 1.5 days; range, 4 to 9 days). Mice in the low-dose bevacizumab group also had significantly delayed tumor growth, compared with that for mice in the control group. Conclusions and Clinical Relevance-Results indicated that bevacizumab inhibited growth of canine osteosarcoma cells xenografted in mice, which suggested that vascular endothelial growth factor inhibitors may be clinically useful for the treatment of osteosarcoma in dogs. Impact for Human Medicine-Canine osteosarcoma is used as a research model for human osteosarcoma; therefore, bevacizumab may be clinically beneficial for the treatment of osteosarcoma in humans.

Stabilisation of metacarpal or metatarsal fractures in three dogs, using circular external skeletal fixation

Abstract CASE HISTORY: Three dogs that presented with multiple metacarpal or metatarsal fractures, between January 2004 and November 2008. CLINICAL FINDINGS: Case 1 had sustained closed fractures of metacarpal bones II–V, resulting in a valgus angulation of the manus. Case 2 had 2-week-old open, infected, comminuted diaphyseal fractures of metatarsal bones II–IV. Case 3 had sustained open fractures of metacarpal bones II–V, that were initially stabilised with intramedullary Kirschner wires, but had gone to non-union 5 months after the initial surgery. TREATMENT: Circular external skeletal fixation was used in each of the three dogs. In Case 1, the fixator was used to perform a closed reduction, to align the overridden, angulated fractured metacarpus, by distracting the frame. In Case 2, the fixator was applied after a limited open reduction, and was used to provide stable fixation of the comminuted infected fractures while facilitating open wound management. In Case 3, the fixator was applied in buttress fashion, following open debridement and placement of an autogenous cancellous bone graft at the non-union fracture sites. CLINICAL OUTCOME: All three dogs developed drainage tracts from the fixator wire. There was minimal associated lameness or pain in two of the dogs, but Case 3 developed a transient lameness ascribed to infection associated with the wire tracts, which resolved following administration of antibiotics. Inflammation of wire tracts resulted in the fixator being removed prior to radiological evidence of union of all fractures in each dog, and the mean time from surgery to removal of the frame was 12 (range 7–24) weeks. None of the dogs had residual lameness or discomfort associated with the fractures at the time of long-term evaluation, which ranged from 10–45 months following surgery. CLINICAL RELEVANCE: These three cases illustrate the utility of circular external skeletal fixation for the stabilisation of complicated fractures of the metacarpus and metatarsus. The fixators were applied without inducing substantial iatrogenic trauma, and the small-diameter fixation wires provided effective stability of the short metacarpal and metatarsal fracture segments, allowing the fractures to heal. Although complications associated with wire tracts should be anticipated, circular external skeletal fixation should be considered as a viable method for managing complex fractures of the metacarpus and metacarpus in dogs.

Occlusion of the Thoracic Duct Using Ultrasonically Activated Shears in Six Dogs

OBJECTIVE To assess the feasibility of sealing the thoracic duct (TD) in dogs using ultrasonically activated shears via thoracoscopy. STUDY DESIGN In vivo experimental study. ANIMALS Mature dogs (n = 6). METHODS Dogs were anesthetized without pulmonary exclusion and positioned in left lateral recumbency. Lymphangiography was performed to identify TD anatomy. Methylene blue was injected into the lymphatic catheter to identify the TD and its branches. Under thoracoscopic guidance (right dorsal 8-10th intercostal spaces), the TD was sealed with an ultrasonic device and lymphangiography was repeated. If the flow of contrast continued beyond the occlusion site, additional attempts to seal the duct were made. Dogs were euthanatized, the TD was excised and fixed in formalin for histopathology. RESULTS Thoracoscopic identification of the TD was possible in 5 dogs. Three dogs required conversion to a thoracoscopic-assisted approach and 3 dogs required resealing of the TD closer to the diaphragm. Thoracic duct occlusion (TDO) was ultimately achieved in all 6 dogs based on follow-up lymphangiography. TDO by tissue coagulation was confirmed by histopathology. CONCLUSIONS Thoracoscopic identification and occlusion of the TD using ultrasonically activated shears with bilateral lung ventilation is technically feasible in normal dogs and provides a less invasive alternative to open thoracotomy procedures.

Postmortem evaluation of surgery site leakage by use of in situ isolated pulsatile perfusion after partial liver lobectomy in dogs.

OBJECTIVE To evaluate postmortem surgery site leakage by use of in situ isolated pulsatile perfusion after partial liver lobectomies. ANIMALS 10 healthy mixed-breed male dogs. PROCEDURES Dogs were anesthetized, and 5 surgical techniques (pretied suture loop, energy-based sealer-divider, harmonic scalpel, suction with clip application, or suction with use of a thoracoabdominal stapler) were used to perform 5 partial liver lobectomies in each dog. Dogs were euthanatized, and the portal vein and hepatic artery were cannulated and perfused with a modified kidney perfusion machine (pulsatile flow for arterial perfusion and nonpulsatile flow for portal perfusion). Lobectomy sites were inspected for leakage of perfusate, and time until detection of leakage was recorded. The techniques in each dog were ranked on the basis of time until leakage. Time until leakage and rankings for each surgical technique were analyzed by use of an ANOVA. RESULTS Leakage of perfusate was recorded in 44 lobes at supraphysiologic pressures. Of the 6 lobes without leakage, a pretied suture loop procedure was performed in 5 and a harmonic scalpel procedure was performed in 1. Time until leakage and the ranking differed significantly between the pretied suture loop and the other techniques. Time until leakage and ranking did not differ significantly among the other techniques. CONCLUSIONS AND CLINICAL RELEVANCE Time until leakage of perfusate was greater for the pretied suture loop technique than for the other techniques, and that technique did not fail in 5 of 10 lobes. However, all techniques appeared to be safe for clinical use.

Primary anastomosis of segmental external auditory canal atresia in a cat

External auditory canal atresia (EACA) may arise as a congenital deformity, or as sequel to external auditory canal trauma. Diagnosis of EACA was made in this 3-year-old cat by video otoscopy and computed tomography. Successful treatment of congenital segmental EACA was achieved, using end-to-end anastomosis. Primary anastomosis should be considered for treatment of both acute and chronic separation of the annular and auricular cartilages, as well as congenital EACA in the cat.

Development of an intramuscular xenograft model of canine osteosarcoma in mice for evaluation of the effects of radiation therapy

OBJECTIVE To develop an IM xenograft model of canine osteosarcoma in mice for the purpose of evaluating effects of radiation therapy on tumors. ANIMALS 27 athymic nude mice. PROCEDURES Mice were randomly assigned to 1 of 3 groups of 9 mice each: no treatment (control group), radiation at 10 Gy, or radiation at 15 Gy. Each mouse received 5 x 10(5) highly metastasizing parent osteosarcoma cells injected into the left gastrocnemius muscle. Maximum tumor diameter was determined with a metric circles template to generate a tumor growth curve. Conscious mice were restrained in customized plastic jigs allowing local tumor irradiation. The behavior and development of the tumor xenograft were assessed via evaluations of the interval required for tumor-bearing limbs to reach diameters of 8 and 13 mm, extent of tumor vasculature, histomorphology of tumors, degree of tumor necrosis, and existence of pulmonary metastasis and clinical disease in affected mice. RESULTS Tumor-bearing limbs grew to a diameter of 8 mm (0.2-g tumor mass) in a mean +/- SEM interval of 7.0 +/- 0.2 days in all mice. Interval to grow from 8 to 13 mm was significantly prolonged for both radiation therapy groups, compared with that of the control group. Histologic evaluation revealed the induced tumors were highly vascular and had characteristics consistent with those of osteosarcoma. Pulmonary metastasis was not detected, and there was no significant difference in percentage of tumor necrosis between groups. CONCLUSIONS AND CLINICAL RELEVANCE A reliable, repeatable, and easily produced IM xenograft model was developed for in vivo assessment of canine osteosarcoma.

Excision of a congenital laryngeal cyst in a five-month-old dog via a lateral extraluminal approach.

CASE DESCRIPTION A 5-month-old neutered male Golden Retriever was evaluated because of moderate stridor, exercise intolerance, and dyspnea. The dog had been neutered 3 weeks previously, and the referring veterinarian identified a large fluid-filled swelling on the left lateral aspect of the larynx during anesthetic intubation for that surgery. The referring veterinarian drained fluid from the mass by use of needle centesis via the oral cavity, which resulted in temporary improvement in clinical signs; however, the clinical signs returned soon thereafter. CLINICAL FINDINGS A large, soft, spherical mass was located between the left arytenoid and thyroid cartilages and axial to the left ceratohyoid bone, thus causing partial obstruction of the rima glottidis. Laryngoscopic examination, computed tomography (CT), and cytologic evaluation of aspirates performed before surgery; examination during surgery; and histologic evaluation of tissues following surgical excision confirmed the diagnosis of a laryngeal cyst. TREATMENT AND OUTCOME Complete surgical excision was successfully performed via a lateral extraluminal approach to the larynx. One week after surgery, the dog coughed only occasionally. Twelve months after surgery, the owner reported that the dog was clinically normal with no recurrence of clinical signs, and laryngoscopic examination revealed no recurrence of the cyst or other pathological changes in the laryngeal region. CLINICAL RELEVANCE Congenital laryngeal cysts are rarely reported in domestic animals. The information provided here described the CT appearance of a laryngeal cyst and the use of CT in diagnosis and surgical planning. Congenital laryngeal cysts can be resected via a lateral submucosal approach.

Fusion Podoplasty for the Management of Chronic Pedal Conditions in Seven Dogs and One Cat

Eight animals underwent fusion podoplasties for the treatment of chronic interdigital furunculosis (n=3), ectrodactyly (n=1), digit abnormalities associated with tendonectomy (n=1), redundant indertigital skin (n=1), conformational deformity (n=1), and necrotizing fasciitis of the paw (n=1). Median duration of bandaging was 14 days, and median duration of hospitalization was 5 days. Four dogs had dehiscence, which occurred at a mean time of 11 days after surgery. Clinical abnormalities necessitating podoplasty resolved in six animals and improved in two. Six animals had normal ambulation and two dogs had slight weight-bearing lameness after a median follow-up time of 29 mo. Fusion podoplasty may be recommended as a salvage procedure for the treatment of various chronic pedal diseases in dogs and cats.

Stabilization of Juxta-Physeal Distal Tibial and Fibular Fractures in a Juvenile Tiger Using a Hybrid Circular–Linear External Fixator

OBJECTIVE To report stabilization of closed, comminuted distal metaphyseal transverse fractures of the left tibia and fibula in a tiger using a hybrid circular-linear external skeletal fixator. STUDY DESIGN Clinical report. ANIMAL Juvenile tiger (15 months, 90 kg). METHODS From imaging studies, the tiger had comminuted distal metaphyseal transverse fractures of the left tibia and fibula, with mild caudolateral displacement and moderate compression. Multiple fissures extended from the fractures through the distal metaphyses, extending toward, but not involving the distal tibial and fibular physes. A hybrid circular-linear external skeletal fixator was applied by closed reduction, to stabilize the fractures. RESULTS The fractures healed and the fixator was removed 5 weeks after stabilization. Limb length and alignment were similar to the normal contralateral limb at hospital discharge, 8 weeks after surgery. Two weeks later, the tiger had fractures of the right tibia and fibula and was euthanatized. Necropsy confirmed pathologic fractures ascribed to copper deficiency. CONCLUSION Closed application of the hybrid construct provided sufficient stability to allow this 90 kg tigers juxta-articular fractures to heal with minimal complications and without disrupting growth from the adjacent physes.