OBJECTIVE:To describe an extended pedicle flap based on the superficial cervical artery (SCA) for closure of oral defects in dogs. STUDY DESIGN:Anatomic study; in vivo experimental study. ANIMALS:Canine cadavers (13) and 3 dogs. METHODS:The prescapular branch of the SCA was cannulated and perfused with a lead oxide gelatin mixture. The area perfused by 1 SCA was examined as was the rostral extent of the flap. Staged implantation was performed to evaluate flap performance in vivo. In stage 1, the flap was prepared for implantation into the oral cavity. In stage 2, the flap was fully developed to include the 1 degrees, 2 degrees, and partial 3 degrees angiosome of 1 SCA pedicle. The flap was transposed by a bridging incision and a parapharyngeal tunnel into the oral cavity. The flap was used to reconstruct a partial-thickness defect created in the palate. RESULTS:The territory of the contralateral SCA was captured in all cadavers. The full flap reached the level of the canine teeth in all cadavers. In live dogs, necrosis was not observed after implantation into partial-thickness defects and dehiscence was minimal. Loss of pliability secondary to de-epithelialization and staging resulted in a limitation of rostral reach of the flap. CONCLUSIONS:Whereas the flaps did not reach as far rostrally as anticipated, they survived well in the harsh oral environment. The flap may be modified to reconstruct full-thickness palatal defects. CLINICAL RELEVANCE:The extended SCA pattern flap may be adapted for closure of oral defects.

OBJECTIVE:To develop and evaluate surgical approaches to the arteries and veins of the fore- and hindlimbs for use as potential recipient vessels for free tissue transfer.STUDY DESIGN:Experimental anatomic study.SAMPLE POPULATION:Canine cadavers (11): 2 preserved and 9 fresh cadavers.METHODS:Fore- and hindlimbs from 1 preserved cadaver injected with a pigmented silicone/barium mixture, through the common carotid artery and external jugular vein, were cut in 1 cm cross-sections. Tissue sections were used to identify the location of vessels >1 mm that could be used as recipient vessels for free tissue transfer. The other preserved cadaver was used to develop surgical approaches to these vessels. Three surgeons evaluated the written descriptions and illustrations for these approaches using fresh cadavers. Modifications to the surgical approaches were made based on recommendations from these surgeons.RESULTS:Six approaches were developed to isolate forelimb recipient vessels: palmar access, distal medial antebrachial, mid-antebrachial, proximal antebrachial, distal humeral, and mid-humeral vascular access. Twelve approaches were developed to isolate recipient vessels of the hindlimb: plantar access, dorsal tarsal, cranial distal tibial, craniomedial distal tibial, lateral distal tibial, medial distal tibial, medial femorotibial, lateral distal femoral, medial femoral, proximal medial femoral, groin, and proximal lateral femoral vascular access.CONCLUSIONS:Six forelimb and 12 hindlimb sites were identified for surgical access to recipient vessels (>1 mm diameter) suitable for use in free tissue transfer for wound reconstruction.CLINICAL RELEVANCE:For reconstruction of complex wounds of the extremities of dogs, surgeons should consider use of readily accessible recipient vessels that would allow for free tissue transfer to the fore- and hindlimbs.

OBJECTIVE:To develop and evaluate surgical approaches to the arteries and veins of the head and neck for use as potential recipient vessels for free tissue transfer. STUDY DESIGN:Experimental anatomic study. SAMPLE POPULATION:Eleven canine cadavers; 2 preserved cadavers and 9 fresh cadavers. METHODS:The head and neck of one preserved cadaver injected with pigmented silicone/barium, through the common carotid artery and external jugular vein, was cut in 1 cm sagittal sections and cross-sections. These tissue sections were used to identify the location of recipient vessels >1 mm that could be used as recipient vessels for free tissue transfer. The other preserved cadaver was used to develop surgical approaches to these vessels. Three board certified surgeons evaluated the written descriptions and illustrations of the approaches using fresh cadavers. Modifications to the surgical approaches were made based on recommendations from these surgeons. RESULTS:Seven approaches were developed to isolate recipient vessels of the head and neck region. The infraorbital, temporal, and sublingual approaches were easily performed and provided excellent access to the vessels in the region. The approach to the caudal auricular vessels was found to be more difficult but modification of the approach resolved this problem. Access to the facial artery was difficult; it was consistently <1 mm in diameter and thus its use could not be recommended. The approach to the vessels in the cervical region was easily performed. Because of the large size of the external jugular vein and the common carotid artery, end-to-side anastomosis of the donor to recipient vessels is necessary. The large superficial cervical vessels were easily accessed by a lateral shoulder approach. CONCLUSIONS:Surgical approaches to potential recipient vessels of the head and neck were consistently achieved and provided relatively easy access to the vessels. Clinical Relevance- The surgical approaches described in this report can be used to isolate arteries and veins of the head and neck that are >1 mm in diameter. These vessels are suitable for use as recipient vessels for free tissue transfer for reconstruction of complex wounds of the head and neck.

SummaryThe purpose of this project was to compare the ability of skin and muscle to revascularize cortical bone segments in the canine distal limb. A model mimicking severe combined soft tissue and orthopaedic injury with bone devascularization involving the canine metatarsus was developed. Soft tissue defects were reconstructed with a reverse saphenous conduit flap or a free trapezius muscle flap. Cortical bone blood flow was determined by the radiolabeled microsphere method at 21 days post-reconstruction. In addition cortical porosity, the amount of fluorescent labelled intracortical new bone, and the maximum depth of periosteal new bone were determined. Significant differences were not detected between skin and muscle reconstructions for any of the measured parameters of cortical revascularization. The mean values for cortical bone blood flow were higher than expected from previous studies, and did not correlate with subjective assessments of adhesion quality between bone and reconstructive tissue onlay. The reverse saphenous conduit flap, and the free trapezius muscle flap, may respectively provide superior blood supply to underlying bone than local random pattern skin and local pedicled muscle. The reverse saphenous conduit flap has a robust and reliable vascular supply, unlike that to random pattern skin. The free transfer of muscle maintains a vigorous blood supply, and has shown improvements in blood flow over pedicled muscle. Blood flow to both tissue types may be favourably affected by the denervation associated with transfer, causing arteriolar vasodilation and reductions in vascular resistance. In this model, comparable revascularization of cortical bone at 21 days was seen beneath reverse saphenous conduit flaps and free trapezius muscle flaps. However, a role for endosteal revascularization cannot be excluded.Cortical revascularization by skin and muscle reconstruction was compared at 21 days in a canine metatarsal model. Significant differences in cortical bone blood flow were not detected

This study investigated the use of heparinized and/or citrated whole blood as a perfusate for enhancing muscle tolerance to warm ischemia. Unilateral cutaneous trunci muscle flaps were harvested from Sprague-Dawley rats and stored for 10 hr at 22-24 degrees C prior to transplantation to the groin. One group served as a non-perfused control. In three experimental groups, the flaps were hand-perfused ex vivo with 1.0 ml of heparinized, citrated, or heparinized and citrated autogenous whole blood at physiological pressures. Perfusion was administered over a 10-min period 5 hr into the ischemic period. Flaps were revascularized on the femoral vessels and then harvested 48 hr following revascularization. Tissue injury was assessed by calculation of flap weight change (indicator of tissue edema), histochemical evaluation of muscle dehydrogenase activity (nitroblue tetrazolium assay), and light microscopy. All perfused groups had significantly higher muscle dehydrogenase activity compared with non-perfused controls (P < 0.005). Perfusion with combined heparin-citrated blood was significantly more protective than perfusion with either anticoagulant alone (P < 0.025). The only statistically significant reduction in percent flap edema was seen in the combined heparin-citrate perfusion of flaps compared with nonperfused controls (P < 0.05). Histologic evaluation confirmed a reduction in tissue edema in the perfused flaps. We conclude that mid-ischemic perfusion with heparinized and/or citrated blood limits the deleterious effects of extended warm ischemia.

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.

Objective—To evaluate the outcomes and complications in a consecutive series of animals undergoing microvascular reconstructive procedures at two veterinary institutions. Study Design—Retrospective study.Animals or Sample Population—A total of 44 client‐owned dogs and one red‐necked wallaby.Methods—The medical records of all animals undergoing reconstructive microsurgical procedures at the Western College of Veterinary Medicine and Michigan State University were reviewed. Microvascular flap survival and related complications were described. Statistical analysis was performed to determine the significance of relationships between operative factors and outcome.Results—A total of 57 microvascular procedures were performed on 55 animals. Reconstruction was required after trauma in 42 animals, after ablative cancer surgery in 11 animals and for correction of congenital tissue aplasia in 1 animal. Donor tissues included the superficial cervical cutaneous, medial saphenous fasciocutaneous or musculofasciocutaneous, caudal superficial epigastric cutaneous, trapezius muscle or musculocutaneous, caudal sartorius muscle, latissimus dorsi muscle or musculocutaneous, cranial abdominal myoperitoneal, carpal footpad, digital footpad, and vascularized ulnar bone flaps. A total of 53 of 57 flaps (93%) survived. There was a significant relationship between flap failure and level of assistant surgeon experience (P< .05). Latissimus dorsi flaps were significantly more likely to fail when compared with pooled data from all other flap types (P< .01).Conclusions—The success of microvascular tissue transfer in this case series compares favorably with those reported in human reconstructive microsurgery. Both the primary and assistant surgeon should be practiced in microsurgical technique. Failure of latissimus dorsi flaps was not likely caused by an inherently deficient flap design, but was more likely attributed to the location and severity of trauma at the recipient site, the difficulty in isolating suitable recipient vessels for anastomosis or the absence of a trained assistant surgeon during these procedures.Clinical Relevance—This retrospective study documents the successful application of microvascular technique in a series of clinical cases requiring tissue reconstruction.

Tetralogy of Fallot was diagnosed in an acyanotic 11-month-old dog. Predicted pressure gradient across the pulmonic valve, as assessed by use of continuous wave Doppler echocardiography, was 94.5 mm Hg. Bidirectional shunting was identified by means of selective angiography. Open-heart correction was performed, using a transatrial approach with limited ventriculotomy and cardiopulmonary bypass. The hypertrophied infundibulum was resected, the ventricular septal defect was closed primarily, and a transannular pericardial patch graft was applied. Pressure gradients across the pulmonic valve were 52.9 and 22.8 mm Hg 2 weeks and 4 months after surgery, respectively. Advances in cardiopulmonary bypass, anesthetic management, and use of the transatrial approach may improve the success of open-heart correction of tetralogy of Fallot in dogs.

SummaryFour microvascular carpal foot pad transfers were performed on three dogs for reconstruction of weight bearing surfaces. All of the dogs had suffered severe trauma to the major weight bearing foot pads of at least one foot due to: burn injury (one dog), ischaemic injury (one dog) or sharp trauma (one dog). The vascular anatomy of the carpal foot pad flap was consistent in all of the dogs. The arterial pedicle arose from the caudal interosseous artery and the venous effluent drained via the cephalic vein. All of the flaps survived transfer. Post-operative care included heavily padded bandages and daily visual assessment of flap viability. All of the flaps developed partial wound dehiscence along their distal borders, presumably due to incisional stresses from weight bearing. The flaps were surgically repositioned as necessary in order to maintain a central weight bearing position. Ultimately, all of the flaps healed and hypertrophied to accomodate weight bearing stresses. In all dogs functional results were good.Foot pads are highly specialized to withstand the hostile environments into which they are placed. Reconstruction of weight bearing surface following loss of foot pads, therefore, is difficult. Microvascular free transfer of foot pads allows the reconstruction of such deficits with tissue that is, anatomically, most appropriately suited to adopt the function of weight bearing. Microvascular free transfer of the carpal foot pad flap for foot reconstruction is demonstrated in three clinical cases.

OBJECTIVE:To evaluate the feasibility of and morbidity and mortality associated with cardiopulmonary bypass (CPB) using deep hypothermia and low flow perfusion in adult dogs weighing less than 10 kg.STUDY DESIGN:Prospective, descriptive study.ANIMALS:Two groups of three dogs underwent CPB. Group 1 dogs underwent deep hypothermia (15 to 18 degrees C), 45 minutes of low perfusion flow (20 mL/kg/min) and 1 hour of aortic cross clamp time. In group 2, ultrafiltration of perfusate before discontinuation of bypass was added to the standard treatment. Complete blood counts, serum biochemistry, urine output, ejection fraction, and cardiac output were monitored before and for 7 days after surgery.RESULTS:All dogs were successfully weaned from bypass. Four of six dogs survived, three without major complications. One dog developed and recovered from septic pleuritis. Two dogs died or were euthanatized after surgery because of respiratory or gastrointestinal complications. Minor complications included anemia, hypoproteinemia, and electrolyte disturbances. Transfusion requirements and edema formation were reduced by ultrafiltration.CONCLUSIONS:The observations in this study support the feasibility of low flow hypothermic CPB. Meticulous tissue handling, precise equipment, ultrafiltration, and aggressive postoperative potassium supplementation are recommended for smaller patients.CLINICAL RELEVANCE:Increased sensitivity to adverse sequelae of CPB may be associated with small patient size. Further evaluation is necessary before routine clinical application of low flow hypothermic CPB in this patient population.

SummaryThe objectives of the study are to describe the vascular anatomy of the carpal foot pad and to describe the surgical technique for its dissection as a free microvascular flap.Sixteen front legs from ten different dogs weighing from 20 to 30 kg were used for the study. All of the dogs were euthanatized for reason unrelated to the study. Dissection of the carpal foot pad with its dominant arterial and venous pedicle was performed and angiographic studies were performed by injection of barium sulphate and “high detailed” radiography.The vascular anatomy of the carpal foot pad was consistent in all of the dogs. The arterial pedicle arises from the caudal interosseous artery and venous drainage is provided by the cephalic vein. A branch of the ulnar nerve parallels the arterial blood supply and may be included in flap dissection. Surgical dissection of the carpal foot pad flap is relatively straight forward. The length and diameter of the arterial and venous pedicle are appropriate for microvascular anastomosis.The carpal foot pad in the dog represents a viable option for microvascular transfer and reconstruction of weight bearing surfaces.Cadaveric dissection was used to study the vascular anatomy of the carpal foot pad in dogs and to assess its potential use as a free microvascular flap.

Anatomic and experimental evaluation of the feline latissimus dorsi muscle was performed to assess its potential use as a free muscle flap. In the anatomic study, nonselective angiography of the subscapular artery was performed in nine heparinized feline cadavers. The muscle dimensions and vascular anatomy of the dissected latissimus dorsi muscle were recorded. In the experimental study four cats underwent heterotopic transplantation of a partial latissimus dorsi flap, and three cats underwent orthotopic transplantation of a complete latissimus dorsi flap. The mean length and width of the latissimus dorsi muscle was 19.0 and 5.4 cm, respectively. The dominant vascular pedicle was the thoracodorsal artery and vein. The average length and diameter of the thoracodorsal artery was 2.7 cm and 0.6 mm, respectively. Minor vascular pedicles were provided by branches of the intercostal arteries. Numerous choke anastomoses existed between the two pedicle systems. Viability of muscle flaps based on subjective evaluation, angiography, and histopathology, was 66% and 100% in the heterotopic and orthotopic studies, respectively. Flap failure seemed to be caused by both arterial and venous thrombosis. The latissimus dorsi muscle flap met criteria required for application in microvascular reconstruction. The vascular pattern was appropriate and consistent. Donor site morbidity was low, whereas surgical accessibility was high. The muscle satisfied the physical criteria of a free flap. Long-term anastomotic patency and flap viability was shown.

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.

Heparin has been found to decrease ischemia/reperfusion injury in skeletal muscle and other tissue/organ systems. The timing of heparin administration to the muscle vasculature has not been explored. We investigated the use of heparinized blood as a washout solution during ischemia to reduce ischemia/reperfusion injury. A rat cutaneous maximus muscle free flap was subjected to a 10‐hr period of room temperature ischemia, then was heterotopically transplanted to the groin via microsurgical revascularization to the femoral vessels. In three experimental groups, flaps were subjected to brief ex vivo perfusion with autologous heparinized blood, at 2, 5, or 8 hr into the 10‐hr ischemic interval. In the two other groups, the flaps were not perfused, and the animals were systemically heparinized either before ischemia or before transplantation, respectively. A control group underwent no flap perfusion or systemic heparinization. After transplantation, flaps were given a 48‐hr period of in vivo reperfusion, then were harvested for evaluation. Flaps undergoing ex vivo perfusion or preischemic heparinization had no significant differences in weight gain (edema) compared with flaps receiving posttransplant heparinization or no heparinization (controls). The dehydrogenase staining of muscle biopsies was significantly faster (indicative of viable tissue) for perfused flaps and the flaps for which the animals received preischemic heparinization, when compared with flaps for which the animals received posttransplant heparinization or no heparinization. From these results, we conclude that heparin offers protection from ischemia/reperfusion injury when it can be introduced into the vascular network either prior to or during the ischemia period. These findings suggest the possibility of using heparinized washout solutions to enhance survival in amputated extremities. © 1995 Wiley‐Liss, Inc.

The distal femoral epiphyseal plates of 21 8-week-old New Zealand white rabbits were totally or partially (nutrient artery only) devascularized, or devascularized and then microsurgically revascularized. Sacrifice was at 24, 48 or 72 hours postoperatively. The heights of the proliferative and hypertrophic zones of the epiphyseal plates operated upon were compared with the contralateral control epiphyseal plates for both the central and the peripheral regions of the epiphyseal plate. Neither extent of devascularization nor revascularization had a significant effect on the height of the proliferative zone of chondrocytes at any of the follow-up intervals. Selective devascularization of the nutrient artery led to a significant increase in height of the central region of the hypertrophic zone of chondrocytes at 48 and 72 hours. Microsurgical revascularization did not lead to a significant change in the height of either the central or the peripheral regions of the hypertrophic zone of chondrocytes at any of the follow-up intervals. This study is another 'building block' experiment toward vascularized epiphyseal plate transplantation in humans.

A pedicled osteomusculocutaneous flap, composed of the cervical part of the trapezius muscle with its overlying skin and the central spine and body of the scapula, was elevated on the prescapular branch of the superficial cervical vascular pedicle in four dogs. The flap was replaced in an orthotopic location. Bone viability was evaluated using histology, fluorescence bone labeling, and angiography. Bone from the scapular spines had a high percentage of viable osteocytes, positive fluorescence, and vessels were outlined in the angiographic study. Bone from the body of the scapula was not viable based on similar criteria.

The anatomy of the cervical part of the trapezius muscle and its dominant vascular supply, the prescapular branch of the superficial cervical artery, was studied by dissection and selective angiography of 16 canine cadavers. The prescapular branch of the superficial cervical artery supplies blood to the skin of the caudal half of the neck and the cervical part of the trapezius muscle and is a minor contributor to other muscles of the neck. In these dogs, the mean length of the vascular pedicles was 4.4 cm and the mean diameter was 1.0 mm. With this information, it is possible to design a broad musculocutaneous flap suitable for reconstructive microsurgery in dogs. The potential for successful incorporation of the scapular spine in such a flap remains uncertain.

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A musculocutaneous flap based on the prescapular branch of the superficial cervical artery and including the cervical part of the trapezius muscle and overlying skin was transplanted over a defect created on the medial side of the contralateral tibia in four dogs by using microvascular technique. The donor and recipient sites in three dogs were examined clinically for 21 days, after which they were examined angiographically and histologically. All dogs were free of lameness by hour 48. Seromas formed at the donor site between days 7 and 15. One vascular pedicle was traumatized at hour 40, and the dog was euthanatized. Three flaps survived with minimal necrosis. Edema of the flaps was severe from days 5 to 11. Angiograms showed complete perfusion of the flaps, and survival was confirmed histologically. Esthetic appearance and function were good in one dog at month 7.