The effects of tissue expansion on skin lymph flow and lymphatics: an experimental study in rabbits.

Histomorphological, physiological, and biomechanical changes of the skin and tissue that are being expanded have been extensively studied in the past. The purpose of this study was to investigate whether the skin lymph flow and lymphatics may be influenced during tissue expansion, and also to study different pattern of vascular supply of skin on lymph flow during tissue expansion. The skin lymph flow was quantitatively assessed by 99mTc-dextran lymphoscintigraphy, and the structure of dermal lymphatics was evaluated by histological examination in 12 rabbits. Lymphoscintigraphic results showed that lymph flow is significantly reduced both in expanded and non-expanded (sham-operated) skin. Histologically, we saw widespread lymphatic distension in both expanded and non-expanded skin. There were no quantitative differences in the number of lymphatic vessels compared with control skin. We did not see any lymphatic capillaries in the subdermal capsule of either expanded or non-expanded skin. These results show that lymphostasis has an obstructive (mechanical) aetiology, and the tissue expander itself reduces the lymph flow regardless of expansion, and interferes with the formation of new lymphatic vessels.

Prevention of ischemia-reperfusion injury with a synthetic metalloprotein superoxide dismutase mimic, SC52608.

Superoxide dismutase (SOD) scavenges free superoxide radicals generated during reperfusion of ischemic tissue and decreases cellular injury. A synthetic manganese-based metalloprotein superoxide dismutase mimic, SC52608 (Monsanto Co.), was tested in the isolated rabbit rectus femoris muscle flap to determine its effects on ischemia-reperfusion injury. The results of our experiments analyzing 38 isolated rectus femoris muscles in 19 New Zealand White rabbits show that administration of SC52608 at the onset of 4 hours of warm ischemia and before reperfusion significantly increases the survival of the muscle from 20.0 +/- 4.9 percent (control, HEPES) to 81.5 +/- 4.6 percent (SC52608) (p < 0.001). It preserved functional contraction in 8 of 10 muscles; only 1 of 12 control muscles (control, HEPES) had contractions (p = 0.0015). SC52608 decreased the neutrophil density from 4.63 +/- 0.6 x 10(4) cells/mm2 in the control (HEPES) muscle to 2.71 +/- 0.6 x 10(4) cell/mm2 in muscles perfused with SC52608 (p = 0.03). The level of malonyldialdehyde decreased from 6.12 +/- 0.26 nmol/gm (control, HEPES) to 4.64 +/- 0.41 nmol/gm (SC52608) (p = 0.0028). Postoperative weights of the muscles showed no statistical difference (p = 0.14) between the controls (16.0 +/- 0.9 gm) and the SC52608 (18.1 +/- 0.7 gm). Our investigation shows that direct intraarterial infusion of a synthetic superoxide dismutase mimic at the onset of ischemia and prior to reperfusion can reduce reperfusion injury in skeletal muscle.

Prevention of microvascular thrombosis by topical application of recombinant tissue factor pathway inhibitor.

Tissue factor pathway inhibitor is a naturally occurring protein inhibitor of factor X and the tissue factor-factor VII complex of the extrinsic pathway of coagulation. The potential of tissue factor pathway inhibitor as a topical antithrombotic agent was evaluated in a rabbit model of thrombosis that combined intimal injury, anastomosis, and a twisted pedicle. In 207 rabbit ears, a near-complete amputation was performed, preserving the central ear artery and vein. The central ear artery was transected, the intima was removed mechanically over a 1-cm length, the artery was anastomosed, and the ear was twisted 360 degrees, wrapping the intact vein around the artery. Before recirculation, the lumen was irrigated on a blinded, randomized basis with either hirudin (100 or 500 units/ml), heparin (50 or 100 units/ml), tissue factor pathway inhibitor (10, 40, 125, or 250 microgram/ml), heparin and tissue factor pathway inhibitor together, or vehicle (control). Upon arterial reflow, the ears were observed for 7 days. Patency rates after 7 days were as follows: hirudin, 30 and 55 percent; heparin, 43 and 50 percent; tissue factor pathway inhibitor, 75 and 90 percent; heparin and tissue factor pathway inhibitor, 75 percent; and vehicle, 6 percent. The higher concentrations of tissue factor pathway inhibitor led to significantly higher patency rates than heparin, hirudin, or control solutions. Electron microscopic evaluation of specimens irrigated with gold- labeled tissue factor pathway inhibitor revealed the inhibitor bound to the injured intimal surface for at least 3 days postoperatively. Coagulation studies showed no change in the clotting profile upon intravascular infusion with tissue factor pathway inhibitor even at the highest dose used topically. We conclude that tissue factor pathway inhibitor is a more effective topical antithrombotic agent than either heparin or hirudin.

Facial reconstruction with prefabricated induced expanded (PIE) supraclavicular skin flaps.

The prefabricated induced expanded (PIE) supraclavicular flap refers to the staged transfer of an expanded supraclavicular skin with a fascia flap used as the carrier. In three patients, we utilized PIE supraclavicular flaps to successfully reconstruct a total forehead and two major nasal defects. Our first PIE flap confirmed the feasibility of the method but necessitated two microvascular free flaps. In the ensuing two patients, we reduced the need for microvascular anastomoses by using simple pedicled flap transfers in either or both stages. Whenever feasible, the preferred method consists of transferring a temporoparietal fascia flap to a subcutaneous pocket in the ipsilateral supraclavicular fossa and simultaneously placing a skin expander under both the fascia flap and the supraclavicular skin. After adequate expansion, the fascia becomes incorporated within the capsule of the expander, and the composite capsulofasciocutaneous flap can be safely transferred to the facial defect as the PIE flap. These patients show that supraclavicular PIE flaps can provide ample amounts of vascularized cutaneous tissue for the reconstruction of major facial defects. The necessary tissue is generated by expanding the most desirable tissue type available, and a selected vascular pedicle is induced to perfuse and carry that generated tissue. Compared with conventional expansion and adjacent flap transfers, PIE flaps allow the transfer of expanded skin to distant sites as island or free flaps perfused by the induced vascular pedicles.

Localization of topically applied TFPI binding sites in an intimectomized microvessel.

Tissue factor pathway inhibitor, TFPI, has been shown to be highly effective as a topically applied antithrombotic in an arterial model of vascular thrombosis. To elucidate the mechanism and site of TFPI action, recombinant TFPI was conjugated to 30 nm diameter gold particles and used to localize the sites of TFPI binding in a traumatized microvessel by transmission electron microscopy. The model, the central artery of the rabbit ear, was transected, denuded of endothelial lining (intimectomized), and re-anastomosed. Prior to the restoration of blood flow, TFPI-gold or unconjugated gold particles in solution were applied by irrigation to the intimectomized vessel lumen. After 10 min of blood flow, the artery was harvested for electron microscopy. TFPI-gold binding was localized to the fine strands of fibrin that lined the lumen of the intimectomized section of the artery. Little or no binding was found on platelets, exposed smooth muscle, cell membrane fragments, or uninjured vessel segments. The TFPI-gold binding could be competed with native TFPI. TFPI-gold was inhibitory, although less potent than native TFPI, in a prothrombin time assay. Unconjugated gold exhibited very little binding in the vascular model. Hence, the TFPI-gold conjugate behaved like native TFPI. Our observations have identified the fibrin complex as an in vivo binding site for TFPI and suggest that this is an in vivo site of action for TFPI as a topical antithrombotic agent.

Experimental reproduction of free flap errors: a new model of thrombosis.

Surgical errors in the length and orientation of a flap pedicle can result in kinks, twists, or tension on the pedicle vessels. When these errors occur together with the microvascular repairs associated with free flap transfer, thrombosis and flap failure may be the outcome. A model was designed to simulate these events. The rabbit central ear artery and vein were dissected and all other tissue connections were severed in a near-complete amputation. The artery was transected, shortened by 2 mm, and repaired standardly. The ear was then rotated 360 degrees, twisting the vein around the repaired artery. The ear cartilage was shortened by 6 mm, then sutured, and the skin was closed. In a series of 20 ears, 95% necrosed, 18 from arterial thrombosis and 1 from venous thrombosis. Several other groups were used in which aspects of the basic model were modified to determine the factors influencing failure. When the arterial anastomosis was not performed and the vascular pedicle was rotated with cartilage shortening, all ears survived; when the cartilage was not resected in this paradigm, leaving tension on the pedicle, 50% of the ears necrosed from venous thrombosis. In counterpoint, when the artery was repaired without twisting the pedicle, all ears survived, whether or not the cartilage was shortened. When the artery was repaired without shortening it and with rotation of the ear, 50% of the ears necrosed when the cartilage was shortened, 40% from venous thrombosis and 10% from arterial thrombosis; all ears necrosed (of venous thrombosis) when the cartilage was not shortened.(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue generation with growth factors.

BACKGROUND: An in vivo experimental model was introduced to determine whether the mitogenic effect of recombinant platelet-derived growth factor (rPDGF) could be used to generate potentially useful tissue. METHODS: In Lewis rats, the extended femoral arteriovenous bundle was placed within silicone chambers containing collagen disks. The disks could deliver their content of rPDGF-BB (125 to 131 micrograms/disk) either as a rapid pulse or as a slow release. The time course of tissue generation was determined by harvesting the specimens at various postoperative days. The effect of continuous versus pulsed delivery was determined at 30 days. Analysis of the generated tissue was performed by use of histomorphometry. RESULTS: Pulsed delivery of rPDGF-BB induced the formation of a substantial amount of tissue that peaked at 10 to 15 days (145.9 +/- 13.8 vs 35.0 +/- 6.8 mm3, p < 0.0001); however, the generated tissue completely subsided by day 30. Sustained delivery of rPDGF-BB caused continuous growth of the tissue and was more effective than pulsed delivery. CONCLUSIONS: In an experimental model that approximates an in vivo tissue culture system, rPDGF-BB can induce a tenfold increase in tissue within the chamber. However, that tissue is labile and its survival necessitates continuous rPDGF-BB delivery. To become useful for reconstructive purposes, means to stabilize this new tissue growth are needed.

Applications of free scapular flap.

The scapular flap described by Saijo and dos Santos, presents some advantages such as a thin and hairless flap, large vessel diameters, and a long vascular pedicle with a constant anatomy. Furthermore, it provides combined use of skin and vascularized bone tissue from the scapula. Between the years 1988 and 1991, we have successfully used free scapular flaps for the reconstruction of various defects in twelve patients.

Prefabricated microvascular shoulder free flap for forehead reconstruction.

In a case with a large forehead defect following tight scalp bandaging in childhood, a prefabricated microvascular shoulder free flap was used for reconstruction. A free forearm fascial flap, with the radial artery and the concomitant vein as pedicle, was harvested and inserted under a subcutaneous pocket opened in the left shoulder region which served as the future "prefabricated free flap". In addition, a tissue expander was placed in this pocket to provide the necessary tissue expansion to enable primary donor site closure.

Vertical trapezius myocutaneous flap for covering wide scalp defects.

The vertical trapezius myocutaneous flap is extremely reliable, with its wide arc of rotation and its considerable soft tissue bulk, when resurfacing major defects following radical tumor surgery in the head and neck region. In this paper, the use of the vertical trapezius myocutaneous flap in the reconstruction of major scalp defects will be presented and its advantages discussed.

A rare case of Kaposi's sarcoma; hand localization.

A case is reported of Kaposi's sarcoma in a very rare location, the palmar surface of the hand. Kaposi's sarcoma, which still has an unresolved etiology has recently gained great interest because of its close association with AIDS. In our case there had been recurrences even after two surgical interventions. The result of the histopathologic examination was reported as "fibrous histiocytoma" but was also suspected to be a "dermatofibroma". We considered malignancy and performed a wide and deep total excision of the lesion. The histopathologic findings showed Kaposi's sarcoma. Discussion persists in the literature whether to apply radiotherapy or surgery for the treatment of the solitary Kaposi's sarcoma lesion. We have thus far obtained a cure after excision.