Revascularization of a free nerve graft wrapped in omentum.

The revascularization of free nerve grafts wrapped in omentum was assessed in an experimental model using rats. Revascularization of the grafts, using the original vessels, proceeded in the same way as reported in earlier studies, being in progress on the 4th day after the operation and essentially complete on the 8th day. The observations made in the experiment suggest that using omentum does not offer much of an advantage with nerve grafts transplanted to tissues with a good blood supply. Using omentum would seem indicated for grafts transplanted into cicatrized or irradiated tissues.

Spherical dilators to resolve arterial spasm.

Arterial spasms developing during microsurgical vascular anastomoses can be a difficult problem. We have been using specially developed spherical dilators in clinical practice to remove spasm that do not respond to the application of warm saline with lidocain. Dilating the spastic segment of the vessel two or three times with the instrument will usually relieve the spasm. Experimental testing of the method on the rat carotid artery has shown that using the dilator three times causes only moderate damage to the endothelium, which is largely overcome within one week. Thrombosis of the dilated artery was never seen in experimental studies and clinical use.

Some thoughts and observations concerning the prevention of neuroma.

Reliable prevention of neuroma is a problem the solution of which is still outstanding. Compared to earlier methods, which mostly consisted in attempts to stop axonal proliferation abruptly, it is now coming to be generally accepted that the regenerative potential of the axons needs to be reduced gradually. The methods most in accord with this view--centro-central anastomosis and capping of nerve ends with a nerve or vein graft--are considered, adding personal observations. A new variant that has shown special promise in animal experiments involves using a nerve and a vein graft in combination. The method still requires clinical verification.

The problem of dehydration and healing of burn wounds.

In an experiment on rats, a partial thickness burn wound 20 mm in diameter was produced on the dorsum. Half the wound area was left untreated, the other half painted with elastic collodion. Examination on the 10th day following the intervention confirmed that prevention of dehydration can save a good proportion of thermally damaged tissue. It was also shown that prevention of dehydration results in a marked delay in wound healing.

Soft tissue response to textured silicone implants in an animal experiment.

In a study on rats to assess soft tissue response to textured silicone implants, ellipsoid 15 x 20 mm pieces from the bag of a Biocell breast prosthesis were implanted under the dorsal skin. Histological examinations including immunohistochemical detection of myofibroblasts were made 2 weeks and 1, 3, 6, and 8 months after implantation (12 specimens for each time interval). On the smooth side of the implant, which served as a control, the thin connective tissue capsule characteristically seen with silicone elastomer implants developed within a month. Myofibroblasts were present after the first month and appeared to reach a peak 3 months after implantation, after which they showed marked regression. On the textured side of the implant, villous processes were a characteristic feature of the capsules; originating in a common basal layer, they penetrated into the cavities of the implant. Collagen deposits and myofibroblasts only became more evident during the third month after implantation; they were limited to the common basal layer of the capsule, though foreign body reaction persisted in the villous processes until the end of the experiment. The experimental study, limited to an 8-month period after implantation, showed that texturing of the implant surface prevents compact capsule development and considerably delays or inhibits the maturation process.

Silicone cuffs for peripheral nerve repair: experimental findings.

The effectiveness of silicone cuffing in peripheral nerve repairs was assessed in a comparative study in rats. The femoral nerve was dissected out and severed bilaterally. The nerve ends were brought together with four epineural sutures on one side, while only one epineural suture was used on the other side, placing a silicone cuff around the junction site. Initially, nerve regeneration appeared to be improved by the cuff, with electrophysiologic parameters and histologic studies 6 weeks after the procedure yielding better results for the tubulated nerves. Subsequently, however, conductivity was less in the tubulated nerves, and results were clearly inferior to sutured nerves at 4 months after the operation. The deterioration was due to nerve compression caused by the cuff, which prevented axons from penetrating into the distal nerve stump, and resulted in axon fragmentation in the compressed nerve segment. The risk of nerve compression makes the use of silicone cuffs of doubtful value.

[Revitalization of bone transplants using vascular implants]. / Revitalizace kostního transplantátu implantací cév.

For investigation of revascularization of free autogenous bone grafts by implantation of blood vessels the authors used rats as experimental material. The arteries or bundles of arteries were implanted into the spongiosa of the free bone transplant--a tall vertebra. It was revealed that capillary proliferation which promotes revascularization of the graft started in the adventitia of the implanted artery. Therefore it is not necessary to severe the artery, as recommended in methods used in previous studies. Revascularization occurs even when the implanted artery retains its original function. Implantation of blood vessels does not prevent extensive necrosis of the graft but indicates osteogenesis which results in substitution of the necrotic tissue.

Prefabrication of a skin axial flap in experiment.

Flap prefabrication was studied on the rat thigh by implanting femoral vessels into the flap's subcutaneous tissue. The aim of the experiment was to determine optimal prefabrication time, and to monitor, using contrast staining, the dynamics and morphology of the neovascularization process. The minimal time for successful prefabrication was 14 days in our experimental model. The potential of physiological and pharmacological regulation of the process of capillary neoformation is discussed. A successful attempt at free transfer of a prefabricated flap to the contralateral thigh and at femoral vessel anastomosis by microsurgery was also made as part of the experiment.

Spontaneous anastomosis of transected vessels.

Experiments were performed on rats to establish the capacity for spontaneous repair of transected arteries and veins. The tests were done on the femoral vessels, with transection effected in a number of modifications. Veins proved capable of bridging even a triple transection within 2 weeks. Not a single artery, however, anastomosed. Vascular repair was on the basis of adventitial and perivascular networks. Explanations of arterial incapacity for spontaneous repair can presently be only speculative. The observations add to our knowledge concerning the revascularization of free grafts, and also indicate that in veins, spontaneous anastomosis can be induced by loosely approximating the stumps.

Viability of skin subjected to deep partial skin thickness thermal damage: experimental studies.

Secondary tissue loss in burn wounds (due to necrosis in the zone of stasis) is interpreted as a sequel of progressive vascular occlusion and dehydration of thermally damaged tissue. In this study on rats, delayed healing represented an additional factor in determining the fate of tissue that had sustained deep partial skin thickness burns. Early revascularization induced by excision and subsequent replantation of the burned skin resulted in survival of a large part of the corium. Replantation reduced the loss of full thickness skin seen in controls left to heal spontaneously to partial loss in treated wounds. The experiments substantiate the theory that deep partial skin thickness thermal damage is at least partly reversible and indicate that with tangential excision of dermal burns a viable part of the corium is sacrificed. This deeper part of the corium can be saved by early excision and replantation.

Experimental implantation of adipose tissue fragments.

The healing of small adipose tissue implants was evaluated in experimental studies on rats. Adipose tissue of approximately 0.5 ml volume was obtained by resection of parauterine fat pads. The tissue was divided into fragments that were 1-3 mm in size and implanted under the dorsal skin. The implantation of adipose tissue in fragments offered no biological advantage and the healing process terminated in extensive necrosis of fat cells. The results are analysed and considered in relation to the implantation of adipose tissue fragments obtained by liposuction.

[Blood supply of free skin flaps]. / Durchblutung freier Hautlappen.

This article discusses the factors which determine the blood supply of free skin flaps. The method of free transfer consists of three steps, namely, the elevation of the flap, its transfer to the target area with microvascular anastomosis, and the healing of the flap on the recipient site. During the first two steps the flaps meet with a diminished blood supply and, in addition, their tissues undergo a period of ischemia. The flaps are usually able - within certain limits - to tolerate these disturbances of blood circulation. The healing of the flap begins with the proliferation of capillaries in the recipient site, which is stimulated by the relative hypoxia of the transferred tissues. The first capillary links between the recipient site and the flap can usually be observed on the third day after the transfer. On the sixth day after the operation, the anastomoses are quite numerous and can take over the blood supply to the flap. The progress of this dynamic process depends on the functional ability of the anastomosed vascular pedicle. The development of a new blood supply to the flap leads to profound remodelling of its original vascular system and the axial character of the flap is usually lost.

[Stimulating effect of isolated nerve segments on the regeneration of peripheral nerves]. / Stimulative Wirkung von isolierten Nervensegmenten auf die Regeneration peripherer Nerven.

The present paper concerns observations in two series of experiments in which the effect of isolated nerve segments on nerve regeneration was studied. Bridging of a nerve defect with a tube was used as an experimental model--a model often used in studies on nerve regeneration today. In the first series of experiments performed on rats, 14 mm of the femoral nerve were removed and the gap bridged with the femoral vein. A 2-mm nerve segment was inserted at the center of the vein in one group of the animals. In the second experimental series performed on rabbits, 40-45 mm of the peroneal nerve was resected. Up to three segments were introduced into the lumen of the bridging vein. The experiments demonstrated the promoting effect of nerve segments on nerve regeneration and indicated the probable mode of their action: the nerve segments serve as an additional source of Schwann cells and of neurofibroblasts, contributing substantially to the formation of the guiding structures for the axons. The nerve segments are apparently able to develop a similar nerve structure to that formed by the distal nerve stump. However, this ability also appears to be limited to a distance of 10 mm as is the case with distal nerve stumps. These conclusions do not exclude a possible neurotropic action of the nerve segments.

A training model for the stereomicroscopic evaluation of flap survival.

The stereomicroscopic appearance of the vasculature and circulation of groin flaps, with their epigastric pedicles divided at various time intervals, is an early diagnostic indication of flap viability. A simple and comprehensive training model, with characteristic vascular and flow changes within a single flap, is provided in rats, with pedicles transected at three to four days after the flap is raised.

Glueing of peripheral nerves with fibrin: experimental studies.

Experiments were carried out on rats to compare fibrin glueing of nerves with suturing. For this purpose, the sciatic nerve was transected and the cut ends were joined, either by glueing with Tissucol or with an epineural suture. Assessment of the two methods was based on clinical and histologic examination and electrophysiologic measurement (latency and amplitude of compound action potentials). Reconstruction with fibrin glue proved to be the simpler method, requiring considerably less time than nerve suture. Separation of the glued nerve stumps did not occur in any instance. The fibrin glue was completely absorbed after a maximum interval of one week following the operation. It had no negative effect on nerve regeneration, which was the same for both groups. The histologic variability found to be characteristic of both glued and sutured nerves reflected differences in the way the nerve repair was effected, rather than in the method used. The electrophysiologic measurements did not show statistically significant differences between the two methods of nerve repair.

Stimulation of peripheral nerve regeneration by an isolated nerve segment.

An experimental model in rats was used to assess the stimulant effect of an isolated nerve segment on peripheral nerve regeneration. In a first group of animals, 14 mm of the femoral nerve was removed unilaterally and the gap was bridged with femoral vein taken from the other side. In a second group, the intervention differed in that a 2-mm nerve segment was introduced at the center of the bridging vein. Histological examination was done three months after the operation. In the first group, a newly formed nerve structure was found in the proximal part of the vein, with incipient myelination of nerve fibers. The frequency of nerve fibers decreased with the distance from the proximal nerve stump, with no fibers present in the distal part of the vein. In the second group, a well-developed nerve structure was noted in both the proximal and the distal parts of the bridging vein, with myelination well advanced. Possible reasons for the positive effect of an isolated nerve segment in bridging nerve gaps are discussed.

Adipose tissue in plastic surgery.

In this article I review the present state of knowledge about adipose tissue as it is relevant to the practical purposes of plastic surgery. Fat cells are normal constituents of loose connective tissue. Large numbers of fat cells organized into lobules are classified as adipose tissue. Adipose tissue is a special form of reticular connective tissue. The lobules are both morphologically and angiologically independent units. They are seen as well-vascularized structures supplied with blood through a pedicle. Severance of the lobule normally results in necrosis. The subcutaneous fat layer derives from the "primitive organs" identifiable in the hypodermis from the fourth fetal month onward. The primitive organs are the basis for individual fat lobules. The development of adipose tissue continues until physical growth is complete. The disposition of the subcutis to develop adipose tissue shows great variation in different regions of the body. The in-situ mechanical resistance of adipose tissue is provided by the supporting structures. The development, structural characteristics, and physiology of adipose tissue can provide an explanation for many of the observations plastic surgeons have made on this tissue. The processes involved in healing, grafting, and reduction of adipose tissue are analyzed and considered in relation to the clinical picture.

[Pathophysiology of the burn wound]. / Pathophysiologie der Verbrennungswunde.

The thermal injury produced by the first, second and third degree burn is defined. The degree of thermal damage is characterised by the zones of coagulation, stasis and hyperaemia. The zone of coagulation is definitely lost and the pathophysiological changes in the zone of hyperaemia are spontaneously reversible. The zone of stasis although not immediately destroyed converts to necrosis during the first week after injury owing to a fatal combination of several factors. The healing of a burn wound proceeds from the zone of hyperaemia and follows the same course as in a surgical wound. Modifications of the healing process are produced by the graded nature of the thermal injury and by the presence of coagulated tissue acting as a foreign body. Attempts to reduce the secondary tissue loss concentrate on the zone of stasis the damage to which is considered as potentially reversible. Therapeutic measures positively influencing the pathophysiological processes in a burn wound are discussed.