Effect of Ischemia and Reperfusion on Neutrophil Accumulation in Equine Microvascular Tissue Flaps

Objective— To investigate neutrophil accumulation after ischemia and reperfusion (IR) in microvascular tissue flaps in horses.
Study Design— Randomized controlled experiment.
Sample Population— A total of 8 horses between 1 and 10 years of age, 4 of each sex.
Methods— Control and experimental myocutaneous island flaps based on the superficial branch of the deep circumflex iliac vessels were dissected on each horse. Atraumatic vascular clamps were applied to the pedicle of the experimental flap for 90 minutes and then removed to allow reperfusion. Based on the assumption that rapid infiltration of neutrophils into affected tissues is a hallmark of IR injury, radiolabeled autogenous leukocytes were used to indirectly quantify neutrophil accumulation in flap tissues. Labeled leukocytes were administered through a jugular catheter 30 minutes before flap reperfusion. Biopsies were collected from each flap over a 6 hour postischemia time period; in group 1 (  n = 4  ) from 0 to 6 hours postischemia, and in group 2 (  n = 4  ) from 24 to 30 hours postischemia. Biopsies were examined scintigraphically and histologically for evidence of neutrophil infiltration.
Results— All control flaps survived and 6 of 8 experimental flaps survived. There was no significant evidence of acute neutrophil infiltration into flap tissues after reperfusion in either group.
Conclusions— The results of this study suggest that equine myocutaneous flap tissues can survive a 90-minute ischemic period and reperfusion. No significant evidence of the occurrence of IR injury in flap tissues was found.
Clinical Relevance— The reasons for the previously reported failures of equine free tissue transfer remain uncertain, but they do not appear to be caused by neutrophil mediated injury associated with ischemia and reperfusion.     

Half-Body Radiotherapy

Eight healthy mongrel dogs were treated with half-body irradiation (HBI) in a pilot study to evaluate the technique and radiotolerance of different organs. Cranial and caudal half-body fields were established using the 13th thoracic vertebra as the dividing point. Under general anesthesia, either 7 or 8 Gray (Gy) were delivered to one half of the body using opposing radiation portals. The other half of the body was similarly treated 28 days later. The dogs were monitored for 12 months. Significant radiation effects included transient bone marrow suppression and radiation sickness. There were no serious or life-threatening problems, but the 8 Gy group consistently showed more severe clinical signs and histologic changes than the 7 Gy group. Total body irradiation in two fractions of 7 or 8 Gy given 1 month apart appears to be a safe treatment that can be developed for therapy in veterinary oncology.     

Microneurovascular Free Digital Pad Transfer in the Dog

By cadaver dissections, the fifth digit of the canine hind limb was determined to have a consistent neurovascular anatomy, and therefore be a suitable donor for an axial pattern digital pad flap. The defined digital pad flap was transferred to the region of an excised metacarpal pad by microneurovascular anastomoses in five operations on four dogs. One flap failure was considered to result from failure of the venous anastomosis. In all four successful transfers, cutaneous sensation was reestablished on average in 78 days. There was histologic evidence of nerve regeneration across the anastomosis in one dog at week 24. The transferred pads of three dogs monitored for 15 months underwent hypertrophic changes. There were no complications in two active dogs. In one dog, superficial ulceration of a region of the flap adjacent to the pad required surgical revision. This dog continued to show mild lameness after daily runs of 3 to 4 km.     

Sutured End-to-End and Stapled Side-to-Side Jejunal Anastomoses in the Horse

Hand sutured end-to-end (EE) and stapled side-to-side (SS) small intestinal anastomoses were performed in 10 healthy adult horses. In five SS anastomoses, staple lines on the blind ends of the jejunum were inverted (SSI) and in five they were not (SSNI). Five EE anastomoses were sutured with polydioxanone and five were sutured with polyglyconate. All horses were euthanatized on day 30. Intra-abdominal adhesions were graded (0-4), and stomal areas were calculated from contrast radiographs made with the bowel distended. Histopathology scores for the anastomoses were based on the degree of inflammation (0-3), fibrosis (0-3), and alignment and healing of intestinal layers (0-3). Mean surgery times +/- standard deviations for EE, SSI, and SSNI techniques were 33.9 +/- 5.4, 36.2 +/- 5.6, and 29.6 +/- 5.9 minutes, respectively. Mean and median stomal areas were 9.4 +/- 5.5 and 8.9 cm2 for EE anastomoses and 17.2 +/- 16.5 and 12.1 cm2 for SS anastomoses. Intra-abdominal adhesions developed in three horses, one of which had clinical signs of colic. Mean histopathology scores for EE and SS anastomoses were 4.8 +/- 2.0 (median = 5) and 4.4 +/- 1.8 (median = 4), respectively. There were no statistically significant differences in surgery times, intra-abdominal adhesion scores, stomal areas, or histopathology scores between small intestinal EE and SS anastomoses in these horses.     

Radiographic Progression of Osteoarthritis of the Canine Stifle Joint: A Prospective Study

A radiographic scoring system for features of osteoarthritis of the canine stifle joint was devised. Intra- and inter-rater agreement was assessed by calculation of unweighted kappa statistics. "Global score," "effusion," "osteophytosis," and "intra-articular mineralization" were all features that had acceptable reliability, but "subchondral sclerosis" did not. The scoring system was used in a 13-month prospective study of the radiographic progression of osteoarthritis of the stifle joint, secondary to cranial cruciate ligament deficiency, in 58 dogs. In the index stifle joints all features were characterized by significant change over time, but osteophytosis had the greatest degree of change. In addition, 40% of contralateral joints showed progressive osteophytosis.     

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