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Biomedical subjects

G R Tobin

Publications and source records attributed to G R Tobin.

At least 37 records · Page 2Linked to original sources
PubMed1997

Vascular delay improves latissimus dorsi muscle perfusion and muscle function for use in cardiomyoplasty.

Ischemia of the distal portion of the latissimus dorsi muscle occurs in muscle transfer for cardiomyoplasty and reduces distal muscle contractility and thus the mechanical effectiveness of cardiomyoplasty. We hypothesized that muscle function would be improved by a vascular delay procedure that increases distal muscle perfusion of the latissimus dorsi muscle. The latissimus dorsi muscles of 10 adult mongrel dogs were subjected to a vascular delay procedure on one side and a sham procedure on the other. Following 10 days of vascular delay, muscle perfusion was measured with a laser-Doppler perfusion imager before and after elevation of the muscles as flaps based only on their thoracodorsal neurovascular pedicles. The muscles were wrapped and sutured around silicone chambers (simulating cardiomyoplasty), a stimulating electrode was placed around each thoracodorsal nerve, and the muscles were stimulated to contract in both rhythmic and tetanic fashion. Circumferential (distal and middle latissimus dorsi muscle function) force generation and fatigue rates were measured independently. Circumferential muscle force, circumferential and longitudinal fatigue rate, and distal, middle, and overall perfusion were significantly (p < 0.05) improved in delayed muscle compared with nondelayed muscle. We found that a vascular delay procedure and a 10-day delay adaptation period significantly improve latissimus dorsi muscle flap perfusion and function, particularly in the distal and middle portions of the muscle. Delay should be considered as a means of improving the clinical outcome in cardiomyoplasty.

Adaptation, Physiological↗
PubMed1997

Vascular delay in skeletal muscle: a model for microcirculatory studies.

Dynamic myoplasty is a relatively new use for muscle flaps and has led us to revisit the mechanisms of vascular delay as a means of optimizing blood supply to muscle flaps. Despite the well-documented effectiveness of vascular delay in skin flaps, vascular delay in muscle flaps has not been widely reported. Regardless of the many mechanisms postulated in the literature as contributors to the delay effect in skin, the one element common to all these hypotheses is the importance placed on changes in the microcirculation. Based on this factor, in the present study we developed and validated an animal model in which delay-induced microvascular changes could be measured in skeletal muscle flaps. We used the hairless mouse latissimus dorsi muscle flap because its vascular distribution is similar to that of humans and its thin structure will enable us in future studies to directly view and measure its microvasculature using videomicroscopy. In 12 animals, we found that delay significantly (p < 0.01) reduced necrosis of the distal part of the muscle from 57 +/- 9 percent in nondelayed flaps (n = 7) to 22 +/- 3 percent in delayed (n = 5) flaps. In these studies, we also determined that the hairless mouse latissimus dorsi muscle flap will serve as an excellent model for defining microvascular changes throughout delay.

Animals↗
PubMed1996

Inhibition of wound contraction with colchicine and D-penicillamine.

The effects of locally injected combined colchicine and D-penicillamine on wound contraction were investigated in a murine model. Two full-thickness excisional wounds were made on either side of the back of hairless (hr/hr) mice. A volume of 0.15 ml of colchicine, D-penicillamine, or combined colchicine and D-penicillamine in normal saline vehicle were injected daily into the wound on one side of the animal and 0.15 ml of vehicle alone was injected into the wound on the other side for 5 or 10 days; thus, each animal served as its own control. The surface area of each wound was measured on Days 0, 5, and 10 to determine an index of the rate of wound contraction. At the end of the experimental period (Day 5 or 10), wounds were excised en bloc from euthanized animals for histological studies. The following histological parameters were determined: the thickness of the granulation tissue, the number of fibroblasts in granulation tissue per unit area, and the number of inflammatory cells (neutrophils, lymphocytes, macrophages, mast cells) in subjacent muscle per unit area. Our data showed that after 5 days of treatment, wound contraction was significantly inhibited only in wounds treated with combined colchicine and D-penicillamine. Wound contraction was significantly inhibited even after 10 days of treatment with the combination. Histological studies revealed that although the thickness of the granulation tissue and the number of inflammatory cells in subjacent muscle were decreased by D-penicillamine alone, only combined colchicine and D-penicillamine decreased the thickness of the granulation tissue, fibroblasts in granulation tissue, and inflammatory cells in subjacent muscle. Our data suggests that very low concentrations of colchicine and D-penicillamine when combined and injected locally may be potentially useful in controlling surface scar formation.

Animals↗
PubMed1994

Closure of esophageal defects with muscle flaps.

OBJECTIVE: To determine the feasibility and reliability of muscle flaps as a sole means of closure of severe esophageal defects. DESIGN: Retrospective case series of patients with esophageal defects closed with muscle flaps. Mean follow-up was 6 years. SETTING: A university hospital and a tertiary care, university-affiliated, private hospital. PATIENTS: Fourteen patients with esophageal defects that could not be closed by standard suture techniques or failed to close with observation alone. MAIN OUTCOME MEASURES: Survival, continued esophageal leakage, restoration of esophageal continuity, and long-term esophageal function. RESULTS: There was one operative death and one delayed death, both unrelated to the esophageal injury. There were five early leaks that healed promptly. Esophageal continuity was restored in all patients. Long-term esophageal function has been excellent. CONCLUSIONS: The use of primary muscle repair for esophageal defects not amenable to standard closure techniques provides an excellent means of closing esophageal wounds and restoring esophageal continuity. This option appears to be preferable to other more destructive options in managing this serious problem.

Adolescent↗
PubMed1994

Direct visualization and measurements of wound neovascularization: application in microsurgery research.

Neovascularization or angiogenesis is an essential yet poorly understood component of the healing process. In wound healing research, there is a lack of models enabling quantitative and continuous measurements of wound neovascularization. The hairless mouse ear wound model permits quantitative measurements of wound epithelialization and neovascularization continuously throughout the healing process. On the ears of male homozygous (hr/hr) hairless mice, standardized circular full thickness dermal wounds are produced; then, using vital microscopy, these two processes are directly viewed and measured at day 0 and every third day thereafter until these are complete. This model system and its application to clinically relevant situations are reviewed.

Animals↗
PubMed1994

Microcirculation research, angiogenesis, and microsurgery.

Angiogenesis, the formation of new blood vessels, is essential to a variety of normal and pathologic processes such as wound healing and tumor growth. In microsurgery the development of new vessels between the transferred tissue and the recipient bed is critical to the final outcome of the reconstruction. Several experimental models have been previously developed to study angiogenesis and the effect that new substances have on regulating this process, but they lack the ability to make quantitative measurements. Therefore, we have developed an animal model using the homozygous (hr/hr) hairless mouse ear; by using intravital microscopy and computer-assisted analysis, angiogenesis can be quantitatively measured. Using this model we showed that basic fibroblast growth factor and transforming growth factor beta significantly increased total vessel length by 32% and 63%, respectively, during 20 days following subcutaneous injection. In this paper the importance of angiogenesis research to reconstructive microsurgery is presented and discussed.

Animals↗
PubMed1994

Vascularized muscle flaps for life-threatening mediastinal wounds in children.

Vascularized muscle flaps have been shown to be highly effective in adults for complicated mediastinal and thoracic wounds. They result in infection control, wound coverage, and preservation of life. Minimal experience exists with the use of these techniques in children. We review our experience with vascularized muscle flaps between 1985 and 1993 in treating life-threatening mediastinal wounds in 8 children. The 8 patients ranged in age from 1 day to 10 years; mean age was 2 years. Two patients had mediastinitis; one had an exposed Gore-Tex graft, and the other had an exposed homograft conduit. One patient had a midline defect with exposed right ventricle immediately beneath the skin. One patient had tracheal dehiscence after repair of an acquired tracheoesophageal fistula from battery erosion. One patient with Marfan's syndrome had a pectus deformity and an unstable sternum after emergent reoperation for a false aortic aneurysm. Two neonates had their sternum left open with a temporary Silastic skin patch after orthotopic cardiac transplantation because of swelling of the donor heart. One transplant patient had wound dehiscence. Vascularized muscle flaps used to heal the mediastinal wounds in this group included pectoralis major (10), rectus abdominis (3), and cervical strap (1). One infant with asplenia and an exposed Gore-Tex graft that had a delayed vascularized muscle flap died of Candida sepsis. Seven of 8 patients (85%) healed their mediastinal wound. Prompt recognition of thoracic wound complications facilitates immediate surgical intervention to obtain primary closure with vascularized muscle flaps, which promotes rapid healing in these children.

Child↗
PubMed1994

Comparison of the effects of commonly used wound agents on epithelialization and neovascularization.

BACKGROUND: The primary effect sought with most topical wound therapy is antimicrobial. Topical wound agents are thought to promote normal healing by protecting the wound from infection. In this study, we examined the effect of six commonly used topical wound agents (bacitracin, sodium hypochlorite, silver nitrate, silver sulfadiazine, mafenide acetate, and povidone-iodine) on epithelialization and neovascularization in noninfected wounds. For this study, a new wound model was used in which direct visualization and quantification of wound epithelialization and neovascularization were carried out throughout the entire healing process. STUDY DESIGN: We measured the effect which 500 U per g of bacitracin, 0.25 percent of sodium hypochlorite, 0.5 percent silver nitrate, 1 percent silver sulfadiazine, 8.5 percent mafenide acetate, and 10 percent povodione-iodine had on the rate of wound epithelialization and neovascularization. The agents were applied topically to 99 circular full-thickness wounds (2.25 mm diameter, 0.125 mm depth) created on the dorsum of male hairless mouse ears. This model enabled us to visualize and measure directly wound epithelialization and neovascularization repeatedly throughout healing, using intravital video microscopy and computerized digitized planimetry. RESULTS: Control wounds and wounds treated with silver sulfadiazine (n = 18) and mafenide acetate (n = 14) epithelialized in 7.2 +/- 0.7, 7.1 +/- 0.3, and 7.3 +/- 0.3 days, respectively. This was significantly (p < 0.01) faster than the wounds treated with povidone-iodine (n = 10), sodium hypochlorite, (n = 8), and bacitracin (n = 13). Wounds treated with povidone-iodine epithelialized the slowest (11.8 +/- 0.55 days). Wound neovascularization was completed most rapidly in the groups treated with povidone-iodine and silver sulfadiazine (15.0 +/- 0.4 and 15.3 +/- 0.7 days, respectively). This was significantly (p < 0.05) faster than wounds treated with silver nitrate (n = 15), which neovascularized in 18.4 +/- 0.56 days. One-half of the wounds treated with sodium hypochlorite (eight of 16) did not epithelialize or neovascularize. CONCLUSIONS: The various antimicrobial agents studied in our in vivo model affect wound epithelialization and neovascularization differently. These effects on these two very important aspects of healing should be taken into consideration when indicating a specific agent for treatment of different types of wounds.

Animals↗
PubMed1991

Vaginal reconstruction with rectus abdominis myocutaneous flap: CT findings.

The distally based rectus abdominis myocutaneous flap is used in a new technique for vaginal reconstruction after pelvic exenteration for malignant disease. We identified 27 patients who underwent this procedure, of whom eight had a total of 14 postoperative CT scans and two CT-directed biopsies. The myocutaneous flap appeared as a unilateral arcuate band of soft tissue extending from the linea alba to the rectal fascia or sacrum. Additional CT findings included asymmetric thinning of the ventral abdominal wall (7/8), fluid collections (2/8), vaginal breakdown (1/8), presacral soft-tissue thickening (6/8), and tumor recurrence (3/8). The postoperative CT scan reflects the altered anatomy produced by the surgery. Complications and recurrent disease can be recognized as deviations from the normal postoperative appearance.

Abdominal Muscles↗
PubMed1990

Management of extensive right ventricular injury or rupture.

Most penetrating right ventricular injuries require simple suture repair, but more extensive injury or rupture of the right ventricle may not be amenable to this method. We have developed an approach to the problem and a technique for repair. Compression of the area with early institution of cardiopulmonary bypass will result in decompression of the right ventricle and preservation of perfusion, preventing profound hypotension. Coverage with an onlay autologous tissue patch provides hemostatic control of the defect without compromising ventricular function. Reinforcement with omentum or muscle flap can give additional protection when risk of infection is present. Application of these principles can be lifesaving and insure good cardiac function despite massive injury to the right ventricular myocardium.

Aged↗
PubMed1990

Distally based rectus abdominis flap for reconstruction in radical gynecologic procedures.

The distally based rectus abdominis myocutaneous flap is an important adjunct to radical pelvic surgery. It can be used to fashion a functional neovagina or to create a patch to cover perineal defects created by exenterative surgery. This report reviews the technical aspects of the creation of this flap and our experience with 22 patients who have undergone this procedure. The flap has been found to be technically easy to create. It is reliable with little tissue loss, and donor site complications are acceptable. Healing is aided by filling the pelvic dead space, thereby decreasing bowel complications, and by bringing a new blood supply into the operative site which has often been heavily irradiated. Operative time is minimized since the procedure requires only unilateral mobilization. Subsequent abdominal surgery has been performed without fascial complications.

Abdominal Muscles↗
PubMed1990

Lip reconstruction with motor and sensory innervated composite flaps.

Among the most elegant of recent flap refinements are innervated composite skin-muscle-mucosal flaps that restore the oral sphincter and carry both motor and sensory nerves. These flaps are based on the orbicularis oris, depressor anguli oris, and levator anguli oris perioral muscles of facial expression. Each flap can be dissected in a manner that allows transfer of the muscle into the oral sphincteric ring while restoring lip form and preserves the motor and sensory innervation. Each flap can be designed to carry skin and mucosa as needed for cover, lining, and vermilion reconstruction. Choice is determined by the specific anatomic lip defects. The orbicularis oris flap is most useful for large central defects of either the upper or lower lip. The depressor anguli oris flap is most useful for lateral lower lip defects or total lower lip reconstruction with bilateral flaps. The levator anguli oris is most useful for upper lip lateral element defects or for total upper lip restoration with bilateral flaps and an Abbe flap philtral reconstruction. Innervated composite flaps demonstrate substantial advantages when compared with preceding methods because of the superior function conveyed by the sphincter reconstruction and preserved motor and sensory nerve innervation.

History, 15th Century↗
PubMed1990

Mandibular-facial reconstruction with segmentally split serratus anterior composite flaps.

Oncologic or traumatic head and neck defects with missing mandible, facial skin, and oral mucosa are especially well suited to reconstruction with a composite tissue unit, based on the subscapular-thoracodorsal vessels, that carries any combination of skin, bone, and muscle to restore vascularized skeletal structures, oral lining, and skin cover. The subscapular-thoracodorsal vascular pedicles supply segmentally split units of the lower serratus muscle and ribs on which it originates. Also, one or two skin paddles for cover and lining flaps are carried either by the cutaneous scapular and parascapular branches of the circumflex scapular vessels or by surgically split segments of the latissimus dorsi musculocutaneous flap. The composite flap can be designed in a variety of combinations to meet recipient defect needs and allow retained innervated segments of the component muscles in situ for preservation of donor motor function. The common subscapular-thoracodorsal vascular pedicle can be transferred either as a microvascular free flap or by pedicle transposition through a subpectoral-subplatysmal tunnel to the mandibular-facial defect. This versatile reconstructive unit illustrates many of the refinements of contemporary flap reconstructions.

Face↗
PubMed1990

Segmentally split pectoral girdle muscle flaps for chest-wall and intrathoracic reconstruction.

The latissimus dorsi, pectoralis major, and serratus anterior provide the principal flaps for major chest-wall and intrathoracic reconstructions. Each of these muscles shows a philogenetically preserved internal metamerism that is expressed by a segmental morphology and neurovascular supply. This segmental anatomy creates multiple independent subunits in each muscle that can be surgically split and independently used. Surgically splitting these muscles permits flap refinements such as creating two flaps from one donor muscle and leaving independent subunits in situ to preserve donor motor function after flap transfer. The latissimus dorsi has a consistent proximal bifurcation of its neurovascular supply into a medial and lateral branch that permits dividing the muscle or skin-muscle unit into two independent flaps. The pectoralis major has three segmental neurovascular subunits, the clavicular, the sternocostal, and the external. These can be surgically split and independently transferred on vascular pedicles from the thoracoacromial, internal mammary, and lateral thoracic vessels. This provides a substantial degree of donor motor preservation, as shown by the pectoralis V-Y myoplasty for mediastinal reconstruction. The serratus arterial has a highly segmental morphology with multiple subunits corresponding to each of the first nine costovertebral units; it also can be surgically split. The resultant upper and lower groups can be further subdivided if needed. These flaps provide useful intrathoracic reconstruction with a substantial degree of donor motor preservation. Such technical refinements substantially increase each flap's versatility and lessens the donor cost for thoracic reconstruction.

Humans↗
PubMed1990

Refinements in vaginal reconstruction using rectus abdominis flaps.

An improved method for vaginal reconstruction after pelvic exenteration or abdominal perineal resection is provided by the distally based rectus abdominis flap. This extended flap carries a skin paddle from the upper abdomen on the rectus abdominis muscle and deep inferior epigastric vascular pedicle. The skin paddle is inversely tubed to form a vaginal pouch and delivered transpelvically to the perineum. In addition to providing a vaginal reconstruction for sexual function, this reconstruction lessens pelvic wound complications in the exenteration patient by filling endopelvic dead space and revascularizing these frequently irradiated wounds. This method provides a neovagina with a single flap and does not involve additional donor sites in the thighs. Transpelvic passage from above not only fills endopelvic dead space better than thigh flaps, but also it allows retention of a vaginal cuff in supralevator resections. Another significant advantage of this reconstruction is its great reliability with minimal incidence of paddle loss. This flap design illustrates a type of flap refinement in which specific flaps can carry tissue from adjacent vascular territories because of anastomotic vessels between the two vascular territories, such as the vascular watershed between the deep inferior epigastric and superior epigastric vessels in this case.

Female↗
PubMed1990

V-Y advancement flaps. Reusable flaps for pressure ulcer repair.

V-Y advancement modification of skin paddle design for the biceps femoris, tensor fascia lata, transverse lumbar, and gracilis flaps permits readvancement of each of these flaps for recurrent pressure ulcers. Our use of this refinement of these flaps over the past twelve years shows that up to two readvancements of each of these flaps can be done, thus preserving reconstructive options in a patient population prone to pressure ulcer recurrence.

Humans↗