The use of long synthetic microvascular grafts in dogs with a view to clinical application

Five centimetres long segments of 3 mm internal diameter synthetic expanded polytetrafluorethylene (E-PTFE) vascular graft (Gore-Tex) were implanted into the femoral arteries, proximal to the origin of the saphenous artery, of 10 mongrel dogs. In five cases saphenous island flaps were raised and the femoral artery was ligated distal to the saphenous origin so that a low flow system was created through the graft. In 10 femoral vessels the Gore-Tex graft was inserted without raising a flap and the distal femoral artery not ligated so that the graft acted purely as a conduit for blood flow to the distal limb. This created a high flow rate model compared to the reduced flow in the former group. In the first group flap survival was evaluated daily by direct observation of the flaps and graft patency was assessed every 48 h by means of Doppler ultrasound. None of these flaps survived longer then 48 h. In the second group, graft patency was monitored every 48 h with Doppler ultrasound and exploration of Gore-Tex grafts at 3 weeks showed that all had thrombosed.     

The use of free microvascular flaps in the leg

Summary After discussing the conventional techniques available for covering skin defects in the leg with associated complex orthopaedic problems the value of the free flap is emphasised. The technique is discussed briefly and six cases are presented. The advantages of this method are outlined and the improvement in healing afforded by the extra blood supply in cases where there is infection and exposure of bone or plate is stressed. Where large complicated skin defects can be predicted, early co-operation between orthopaedic and plastic surgeons is advised.

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Zusammenfassung Nach der Diskussion der konventionellen Techniken zur Behebung von Hautschäden am Bein und der damit verbundenen komplexen orthopädischen Probleme wird die Bedeutung des freien Lappens betont. Diese Technik wird kurz beschrieben und über 6 Fälle berichtet. Es werden die Vorteile dieser Methode hervorgehoben und die verbesserte Heilungsquote, die durch eine extra Blutzufuhr erzielt wird in Fällen, wo eine Infektion eintritt und das Freilegen des Knochens oder der Platte angezeigt ist.

     

Foot reconstruction using free microvascular muscle flaps with skin grafts

Free muscle flap transfer with skin graft coverage for extensive foot defects can be a successful form of foot reconstruction in well-selected patients who have overall normal foot innervation and deep pressure sensibility. Cutaneous sensibility does not appear to be necessary to maintain a functional or well-healed foot. The major reconstructive goal in plantar foot reconstruction is the restoration of weight-bearing during normal ambulation using regular foot apparel. Based on this reconstructive goal, the authors present their current approach in the reconstruction of extensive defects of the foot using free microvascular muscle flaps with skin grafts.     

Intracranial microvascular free flaps

Large acquired intracranial defects can result from trauma or surgery. When reoperation is required because of infection or tumor recurrence, management of the intracranial dead space can be challenging. By providing well-vascularized bulky tissue, intracranial microvascular free flaps offer potential solutions to these life-threatening complications. A multi-institutional retrospective chart and radiographic review was performed of all patients who underwent microvascular free-flap surgery for salvage treatment of postoperative intracranial infections between 1998 and 2006. A total of six patients were identified with large intracranial defects and postoperative intracranial infections. Four patients had parenchymal resections for tumor or seizure and two patients had posttraumatic encephalomalacia. All patients underwent operative debridement and intracranial free-flap reconstruction using the latissimus dorsi muscle (N=2), rectus abdominis muscle (N=2), or omentum (N=2). All patients had titanium (N=4) or Medpor (N=2) cranioplasties. We concluded that surgery or trauma can result in significant intracranial dead space. Treatment of postoperative intracranial infection can be challenging. Vascularized free tissue transfer not only fills the void, but also provides a delivery system for immune cells, antibodies, and systemically administered antibiotics. The early use of this technique when intracranial dead space and infection coexist is beneficial.     

Securing skin grafts to microvascular free flaps using the vacuum-assisted closure (VAC) device

We performed microvascular free muscle flaps on 5 patients using the vacuum-assisted closure (VAC) device (KCI, San Antonio, TX) to secure a split-thickness skin graft to the external surface of the flap in each case. This method of skin-graft fixation was selected in each case because of the complex 3-dimensional shape of the flap or because of concerns of inadequate fixation provided by conventional tie-over bolster techniques in regions that experience a significant amount of shear stress. All 5 flaps remained viable throughout the treatment course and all 5 patients experienced excellent skin-graft take. Also, decreased edema was noted in all 5 flaps. We conclude that the VAC device is a useful tool in the fixation of skin grafts to microvascular free flaps and that its use does not compromise free-flap viability.     

Application of microvascular free flaps to burn deformities

Recent progress in the field of microvascular surgery has opened the way for various types of free tissue transplantation. Surgery involving the revascularization of free tissues by microvascular anastomoses of their arteriovenous pedicle to recipient artery and vein has come to be known by the generic term free flap surgery. This operative procedure makes it possible to achieve one-stage treatment of tissue defects. To date, this useful surgical procedure, has been applied to the correction of extensive burn deformities in 44 patients with good results. This paper describes the operative procedure and a few representative cases of free flap transfer. It is our conviction that free flap surgery has a bright future.

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Résumé Grâce aux récents progrès de la microchirurgie vasculaire, il est maintenant possible de transplanter divers tissus. Cette chirurgie, qui revascularise les tissus transplantés par anastomose de leur pédicule à une artère et une veine du site récepteur, est appelée la chirurgie des lambeaux libres. Elle permet de combler les pertes de substance en un seul temps opératoire. Depuis 1972, nous avons utilisé cette méthode chez 44 malades, pour corriger les séquelles étendues des brûlures. Les résultats sont bons. L'article décrit, par quelques exemples représentatifs, les techniques opératoires. Nous sommes convaincus que cette chirurgie a un brillant avenir.

     

Secondary burn reconstruction: recent advances with microvascular free flaps, regional flaps, and specialized grafts

A representative series of cases are presented which demonstrate secondary reconstructive plastic surgery procedures for the burn victim utilizing microvascular free flaps, regional flaps, and specialized skin grafts. The unstable burn scar of the lower extremity could be managed either by a microvascular free-flap transfer, a muscle transfer, a myocutaneous flap transfer, or a reverse dermis graft, or overgrafting. In the present day, there are many treatment modalities available to us. Long-term wearing of the Jobst pressure stocking is essential in many cases to minimize the hypertrophic burn scar. In our experience, Kenalog injection into a hypertrophic burn scar always has resulted in improvement of the condition although it is usually necessary to give multiple injections into the hypertrophic burn scar at eight week intervals. We have never known Kenalog to fail to improve a hypertrophic scar by flattening it out to a significant extent, but it may take a year or more of injections to accomplish this goal. Microvascular surgery is most definitely a team effort requiring at least two fully trained microvascular surgeons, plus experienced operating room personnel. One microvascular surgeon harvests the free flap, and the other microvascular surgeons prepares the recipient area. Both microvascular surgeons participate in the multiple anastomoses that are required. A microvascular laboratory is essential to the success of a microvascular team, and constant practice is mandatory to maintain and enhance these precision skills. The primary burn surgeon ideally must always keep in mind ways to minimize functional and aesthetic deformity and to continue to improve the quality of life of the burn victim.     

Evaluation of blood flow in free microvascular flaps

Free flap surgery is routine today, yet little is known of its pathophysiology. In this study, the authors evaluated the hemodynamics in different types of free microvascular flaps, by measuring intraoperative transit-time flow. Eighty-six free transplants--21 free TRAM flaps for breast reconstruction, 18 radial forearm flaps for head and neck reconstructions, and 47 muscle flaps for head and neck, trunk and lower extremity reconstructions--were studied. Donor artery flow was highest in the radial artery (mean: 57.5 +/- 50 (SD) ml/min) but dropped (p < 0.001) to one tenth (6.1 +/- 2 ml/min) after anastomosis. The flow was lowest (4.9 +/- 3 ml/min) in the recipient artery of the TRAM flap but, after anastomosis, increased significantly (13.7 +/- 5 ml/min) to the level of the flow in the donor artery. The donor-artery flow in muscle flaps had a mean of 15.9 +/- 11 ml/min, and it significantly increased after anastomosing (23.9 +/- 12 ml/min). Weight-related intake of blood was highest in the radial forearm flap (18.5 +/- 6 ml/ min/100g) and lowest in the TRAM flap (2.5 +/- 1 ml/min/100g). The study showed that blood flow through a free microvascular flap does not depend on recipient artery flow. Even low-flow arteries can be used as recipients, because the flow increases according to free-flap requirements. The blood flow through a free microvascular flap depends on the specific tissue components of the flap.     

Relationship between flow and incidence of thrombosis in polytetrafluoroethylene vascular grafts in free microvascular flaps in lambs.

We have done an experimental study in lambs in which we investigated the influence of flow rate on free microvascular flaps using polytetrafluoroethylene (PTFE) vascular grafts. We set up five surgical groups in which blood flow was progressively increased through the PTFE vascular graft. In group I (venous autograft) we observed just one vascular thrombosis which was located at the site of the anastomosis. In group II (PTFE 3 x 10 mm) all the microvascular flaps became necrosed after the third postoperative day. In group III (PTFE 3 x 10 mm) necrosis also developed in all cases, but the anastomoses remained permeable no longer than eight days. In group IV (3 x 15 mm) the permeability in the microvascular free flaps was about 40% after 21 days, and in group V (3 x 10 mm) it reached 70%. To match graft flow rates with flap survival we did a regression analysis of flow rates for groups II, III, and V and the corresponding survival periods for the flaps. There was a clear and highly significant relationship (r = 0.717, p = 0.0001). In conclusion, it is necessary to maintain blood flow through the prosthesis at a rate higher than the thrombogenic threshold. When the flow rate in the vessels through the PTFE grafts was higher, the viability of the flaps was better. The ideal surgical technique should always be based on an arteriovenous fistula distal to the PTFE vascular graft. It is necessary to maintain blood flow through a prosthesis at a rate higher than the thrombogenic threshold.     

The use of microvascular free groin flaps for the closure of difficult lower extremity wounds.

Proficiency with techniques of microvascular anastamoses allows the successful transfer of free composite grafts from distant sources. We have used the free groin flap in the reconstruction of defects of the lower extremity not amenable to standard methods of closure. A series of representative cases has been presented in this article to illustrate our approach and technique.     

The early use of free flaps in burns

Fourth degree burns of the extremities, that is, burn wounds that go down to denuded bone or tendon, frequently necessitate either amputation of the involved limb or multistage reconstructive procedures involving prolonged hospitalization so that the limb may be salvaged. It is our belief that in these patients free flaps should be considered as a means of initial wound closure. Microvascular procedures under these circumstances may well represent the most expeditious means of salvaging an extremity even when more conventional techniques are available. Studies of a series of patients illustrating this point are presented.     

Enhancement of blood flow in experimental microvascular free flaps

Prolonged ischemia may result in tissue death because of the no-reflow phenomenon. By raising a flap 24 hours prior to subjecting it to ischemia, the authors have been able to significantly lengthen the ischemia interval prior to the onset of tissue death. These effects are believed to be the result of alteration of the no-reflow phenomenon.     

Reconstruction of the foot with microvascular free flaps

Reconstruction of the foot using microvascular flaps has been widely performed in the last 15 years but the choice of flap to repair some areas in the foot remains controversial. We present a series of 128 free flaps to the foot performed during the period of 1975–1990. One hundred and seventeen had a successful outcome (91%). The etiology of the problem was traumatic in 94, congenital in 10, tumor in 9, and chronic ulcerations due to vascular problems in 15. The indications for a specific flap depended on the site and extension of the foot problem, and were divided into four groups:

• 1 Dorsum of the foot. Cutaneous parascapular flap was the best choice.
• 2 The sole-weight-bearing area. We favored the use of the latissimus dorsi muscle flap covered with a split thickness skin graft, done immediately. A proper tailoring of the flap and postoperative care by the patient are very important to maintain the result without ulceration. Tactile sensation does not seem to be essential.
• 3 The area over the calcaneus tendon. We have used cutaneous flaps such as the parascapular and lateral arm flap or fascial flaps covered by split thickness skin grafts (STSG). The fascia used were the serratus or the parascapular.
• 4 Complex trauma problems with extensive skin loss or chronic ulcerations due to vascular diseases: the latissimus dorsi musculocutaneous or muscle plus STSG was mostly used.

The overall number of donor areas were 5 groins, 48 parascapular, 2 gluteal fold flaps, 4 lateral arm, 61 latissimus dorsi, and 8 fascial flaps. © 1994 Wiley-Liss, Inc.     

Clinical use of microvascular PTFE grafts

This paper reports on the first clinical case where a polytetrafluoroethylene (PTFE) graft of less than 3 mm in diameter was implanted in the arterial system of a patient to bridge a vascular defect. A 1.5 cm long, 1.5 mm diameter prosthesis was interposed in the superficial palmar arch of a man who sustained a laceration of the palm of his dominant hand. The graft was implanted by means of the 3M Precise Microvascular Anastomotic System on one end, and by conventional microsurgical technique on the other end. There were no postoperative complications. The patient resumed his preinjury activities 9 weeks after trauma. Serial Doppler ultrasound examinations showed normal blood flow and complete patency of the graft. An angiogram performed 12 weeks postoperatively confirmed the patency of the prosthesis. Twelve months post-operatively the patient is free from complications. The use of small diameter PTFE prostheses may be considered when planning grafting procedures for microvascular defects. © 1995 Wiley-Liss, Inc.     

The effects of short-term preservation on microvascular free groin flaps in rats

Free groin flaps taken from rats were preserved by refrigeration at 4°C in either lactated Ringers solution or tissue culture medium for various periods of time. The results indicate that a high survival rate can be expected at periods up to 72 hours, but there was no success in preserving flaps longer than 72 hours. These preliminary experimental findings suggest that, clinically, a high survival rate can be achieved in free flaps following excision from donor sites even if the microvascular transfer must be postponed for a period up to but not exceeding 48 hours.     

Refinements in hand coverage with microvascular free flaps.

The specialized tissue requirements or dorsal and palmar skin are analyzed and options for full-thickness replacement outlined in detail. Thoughtful and accurate preoperative planning is the key to success. Dorsal coverage with a variety of pedicled and free fasciocutaneous flaps are quite satisfactory. Palmar coverage is more difficult and the need for sensation more critical. Free vascularized temporoparietal fascial flaps covered with full-thickness skin grafts are currently the treatment of choice for most complex wounds.     

Aesthetic facial contour reconstruction with microvascular free flaps

Reconstruction of challenging surgical problems has undergone a dramatic evolution over the past quarter of a century. Microsurgical correction of facial contour deformities is a prime example of how far microsurgical reconstruction has evolved. This article discusses the current surgical techniques.     

Advantages of interpositional long venous grafts in microvascular surgery.

Our clinical experience favors the use of long autologous venous micrografts any time excessive tension is noted along the anastomotic line or in case of a short pedicle in a free flap. The technical problems of harvesting and interposition of these long micrografts are presented.     

Innervation of skin grafts over free muscle flaps.

Skin grafts regain their sensory innervation from the graft bed by the regeneration of nerve endings. Although some clinical studies report sensory recovery in skin grafts implanted on free muscle flaps, the mechanism of recovery is obscure. The purpose of this study was to investigate nerve regeneration in experimental skin grafts on free muscle flaps to elucidate this phenomenon. Thirty-eight male Sprague-Dawley rats, weighing 450-550 g were used in the study. The rat gracilis muscle flap was the free flap model transferred from one groin to the other using microvascular anastomoses. Full-thickness skin grafts harvested from the abdomen were used to cover the free muscle flaps after transfer. Four study groups were formed: Group I (n = 10): Free muscle flaps were transferred without any nerve anastomosis; Group II (n = 10): Free flaps transferred with the anastomosis of the muscle's motor nerve to a sensory nerve at the recipient site; Group III (n = 10): Free flaps transferred with the anastomosis of the muscle's motor nerve to a motor nerve at the recipient site; Group IV (n = 8): Skin grafts were placed directly on the fascia layer over the medial hindlimb muscles and served as controls. The specimens were harvested for histologic examination after 12 weeks. Histologic examination was performed to visualise regenerating nerve endings using H&E, S100, Luxol Fast Blue and tyrosine hydroxylase staining. The specimens were categorically scored according to the staining pattern of neural structures around pilosebaceous units and statistical comparisons were performed by using paired t-test. Skin grafts in both Group II and Group III markedly received tyrosine hydroxylase at the base of their pilosebaceous units in many of the specimens and functional nerve twigs could also be traced from the muscle layer to the overlying skin graft. In contrast, the skin grafts in Group I did not show any nerve function in the central parts. The overall staining scores of Groups II, III and IV were significantly higher than Group I (P < 0.05; P < 0.001; P < 0.05, respectively). There was no statistically significant difference between other groups. No myelinated nerve fibres could be detected in any of the skin grafts with Luxol Fast Blue technique. It was concluded in the present study that skin grafts over reinnervated free muscle flaps can develop significantly better innervation than skin grafts over non-innervated muscle flaps. However, the activity in skin appendages indicating nerve regeneration may only imply a gross sensation and in the absence of any myelinated nerve fibres transmission of finer sensation cannot be expected in any of the study groups.