Proteolytic activity of blowfly larvae secretions in experimental burns.

Secretions of larvae of the blowfly Calliphora erythrocephala digested experimental rat skin burn eschar in vivo and in vitro when applied topically in a vanishing cream base. Debridement was characterized by de-epithelialization and digestion of dermal collagen to a subfollicular level over a 3-day period. Analytic investigation of the secretions demonstrated the presence of enzymes with activities characteristic of trypsin, leucine aminopeptidase, and carboxypeptidases A and B. These were partially characterized. There was no evidence of chymotrypsin, elastase, or collagenase. Preparation of a suitable therapeutic form could result in a preparation useful for enzymatic debridement.

Evaluation of a prototype therapeutic system for prolonged, continuous topical delivery of homosulfanilamide in the management of Pseudomonas burn wound sepsis.

The ability of homosulfanilimide (HS) delivered from two different dressing vehicles to limit bacterial proliferation was evaluated in burned animals deliberately infected with virulent Pseudomonas organisms. Treatment consisted of once daily topical application of one of two vehicles: (1) an experimental prototype system that utilized micronized HS in a hydrophobic, bioerodible, polymeric matrix, impregnated on a fabric backing; or (2) a commercially available dressing that contained the same mass of drug in a hydrophilic cream base impregnated on the same backing. Wounds on control animals were covered with fabric backing with or without the bioerodible matrix. The experimental system was designed to maintain a finite local concentration of HS on the burn wound for at least 24 hours. It is known that the cream base presents a rapidly decreasing concentration of drug to the burn surface. HS delivered from the experimental system produced a significant reduction in deaths compared with the HS delivered from the cream base. In addition, the new method of delivering HS provided better control of local and systemic infection, and better wound hydration and also promoted earlier eschar separation. The experimental system was at least as convenient to apply as the cream and had an advantage with respect to inspection of the wound, since it could be removed and reapplied easily.

Uses of RTV silicone in orbital reconstruction.

In a five-year follow-up of 42 patients with unsatisfactory cosmetic results after enulceation, room-temperature vulcanizing (RTV) silicone was used in the surgical correction of enophthalmos and superior sulcus depression. RTV silicone with a catalyst was placed in a dissected pocket subperiosteally along the floor and lateral wall of the orbit to correct the volume deficit. When vulcanizing in situ into soft silicone rubber, the implant conformed to the orbital wall and did not migrate. We determined tissue tolerance to in situ vulcanizing silicone histologically in 30 rats by inserting prevulcanized and in situ vulcanized material in paired subcutaneous pockets. No statistical difference was noted between the two methods. In 11 cases, the same material was used as a convenient stent to maintain the pressure over a graft and to maintain socket size after the reconstruction of a contrated socket, by filling the socket with RTV silicone which surrounded a Kirschner wire drilled through the lateral orbital rim.

Comparison of synthetic adhesive moisture vapor permeable and fine mesh gauze dressings for split-thickness skin graft donor sites.

SAM and fine mesh gauze dressings were compared on 60 consecutive skin graft donor sites. SAM dressings are significantly better than fine mesh gauze dressings for healing of split-thickness skin graft donor sites; healing occurs much more rapidly with much less pain. In patients known to be colonized with Pseudomonas, care should be taken when using SAM dressings, although it is not an absolute contraindication. There were no clinically significant differences between Tegaderm and Op-Site.

The augmentation of soft tissue with injectable collagen.

Clinical experience has demonstrated the value of injectable collagen in treating small soft-tissue defects. Among the lesions that respond best to injectable collagen therapy are nasolabial and glabellar lines as well as areas of atrophy and soft scars. This material is a useful adjunct to surgical procedures and can correct contour irregularities that may follow rhinoplasty or rhytidectomy. The safety of injectable collagen has also been well demonstrated. The nature and incidence of treatment reactions (less than 3 per cent) remains unchanged since the close of clinical trials. Reactions have been localized, and although some have been cosmetically undesirable, none has been health-threatening. All ultimately resolve without therapeutic intervention. Immunologic studies have confirmed the benign nature and specificity of reactions to injectable collagen. The importance of proper injection technique cannot be overstated. Immediately upon injection, tissue blanching followed by whealing and overcorrection should be evident. These indicate the desired superficial placement of the material. The overcorrection helps to compensate for the loss of carrier saline, and it quickly dissipates. When properly injected, injectable collagen can be used safely and effectively to correct an array of soft-tissue contour irregularities.

The platysma muscle. Anatomic considerations for aesthetic surgery of the anterior neck.

Our current principles for the treatment of anterior neck deformities originally evolved from cadaver dissections and clinical observations. These principles have been applied over the past seven years in nearly 100 patients. We combine as indicated submandibular lipectomy, excision of the submental fat pad, chin implantation, creation or tightening of the platysma muscular sling, and skin tightening and resection. The muscular sling is created or tightened anteriorly by approximation or imbrication of the platysma muscle in the midline. Skin is removed posteriorly, utilizing a complete or lower facelift incision. Using these techniques, we have not found posterior tightening of the platysma muscle or the creation of platysma flaps to be necessary, although we would certainly use them if other alternatives were ineffective.

Mechanism of upper lid ptosis in the anophthalmic orbit.

The occurrence of upper lid ptosis in 66 patients in the anophthalmic state was 18 percent, despite an adequate prosthesis. The commonly cited causes for this entity do not hold up under examination. A detailed review of the anatomy of the levator mechanism and of the anatomy of an enucleation suggests that the etiology is really based on the production of a mechanical imbalance in the levator apparatus. Suggestions for management and for the timing of the correction (in relation to other surgical procedures) are made.

Correction of enophthalmos and superior sulcus depression in the anophthalmic orbit: a long-term follow-up.

The purpose of this study was to review the long-term results in anophthalmic patients treated for enophthalmos. The patients in our series had augmentation of the volume of their orbital contents by subperiosteal placement of room-temperature vulcanized silicone. From 1972 to 1985, sixty-three patients received subperiosteal placement of room-temperature vulcanized silicone for their enophthalmos. Twenty-four of these patients were seen in long-term follow-up 1 to 13 years postoperatively. Indepth follow-up evaluation showed that room-temperature vulcanized silicone subperiosteal implantation for the treatment of enophthalmos and superior sulcus depression in the anophthalmic orbit is a reliable, safe procedure that is without serious complications and has excellent long-term results.

The incidence of experimental contracture varies with the source of the prosthesis.

Nominally equivalent gel-filled miniprostheses supplied by three different manufacturers were placed subcutaneously in rats under identical conditions in a double-blind comparison. The incidence of experimental contracture, defined by grossly visibly asymmetrical distortion of the implant, was 0, 9, and 91 percent for the different manufacturers, consistent with previous observations. Differences among the different implants with respect to the density of the fibrillar capsule structure, the cellularity, and the amount of extruded gel did not correlate with the incidence of contracture. Contracture rate was inversely proportional to the relative degree of filling of the prostheses, as reflected in deviations from the nominal hemispherical shape, and to the viscosity of the gel filling. For implants of the same type, the incidence of contracture was higher when the prosthesis was underfilled. Contracted capsules were more fibrous and contained more cells with microfilament bundles. It is concluded that the physical and geometric properties of silicone implants are critical in the expression of contracture and that these properties vary significantly among prosthesis manufacturers.

Medial approximation of the platysma muscle in the treatment of neck deformities.

The platysma muscle has become recognized as a key to the correction of deformities of the neck. We believe that the decussation of the medial fibers of the platysma muscle is critical to the support of the submental region and is a factor in the pleasing angle between the neck and the chin. The approximation of the medial borders of the platysma has been described in combination with other direct approaches to the anterior neck or with aggressive repositioning or flaps of the platysma. We have achieved pleasing results in the treatment of neck deformities in a variety of clinical situations by medial approximation of the platysma through a short submental incision without other manipulations of the platysma and without complications in 45 patients. All have been followed for more than 1 year.

Differential response of skin and muscle in the experimental production of pressure sores.

An experimental model was developed to determine the effects of pressure on skin and muscle in animals. A pressure-time regimen that consistently produced cutaneous ulceration (100 percent) over a bony pressure point was found to produce no ulceration in skin in a location where muscle separated skin and bone. When pressure was applied to skin over a transposed muscle flap and bone, a reduction of the incidence of ulceration (69 percent) was noted, as compared to the corresponding side without a muscle flap between skin and bone (100 percent ulceration). Histologic studies of skin and muscle biopsies demonstrated epidermal breakdown, increased cellularity, and muscle fiber necrosis when cutaneous ulceration occurred. In the animals without ulceration, were normal muscle or a muscle flap was interposed between skin and bone, there were nevertheless significant areas of muscle necrosis in almost every case. Although these data support the supposition that the increased mass of muscle under skin can diffuse pressure and lessen incidence of ulceration, the extremely high incidence of muscle necrosis in response to pressure, despite absence of skin ulceration points to the possibility that muscle is an unsuitable coverage for a pressure-bearing area.

Correction of lower eyelid ptosis in the anophthalmic orbit: a long-term follow-up.

We describe a 10-year review of 53 patients having had correction of lower eyelid ptosis using fascia lata sling suspension by the operation first described in 1973. The overall conclusion is that this continues to be a reliable procedure with a low complication rate. Four major changes relating to operative technique that create a better result are as follows: (1) the surgical correction must begin with a prosthesis that is ideal for the socket; (2) the fascial strip is narrower at 2 mm; (3) the lateral orbital rim burr hole is placed higher; and (4) the passage of the fascial strip is facilitated by the use of Wright's needle. The optimal sequence of operative procedures in the anophthalmic orbit syndrome is (1) correction of enophthalmos and superior sulcus depression, (2) correction of lower eyelid ptosis, and (3) correction of upper eyelid ptosis.

Long-term study of reactions to various silicone breast implants in rabbits.

A long-term study of the fixation and the encapsulation of soft alloplastic implants in rabbits was done-with examination of the capsules at one, 6, 12, and 18 months. No evidence of hematoma, infection, or carcinogenesis was observed. The type of filling in the prosthesis had no demonstrable effect on the encapsulation. The mobility of the prostheses correlated directly with the capsules evoked by plain silicone, perforated silicone-backed, Dacron-backed, and polyurethane-covered prostheses (in order of decreasing mobility). A patch on the base of a given prosthesis did not influence the amount or character of the capsule formed around the remainder of that prosthesis. The results of this study are discussed in the light of past information, to point out the need for further basic research on these problems.

Iodinated silicone-an antibacterial alloplastic material.

Iodine is readily miscible in silicones and will pass freely into and out of this material at highly predictable and constant rates. Iodinated silicone is thus an effective, controlled-rate delivery system for molecular iodine. This delivery system was shown to produce bacteriostatic and bactericidal effects in vitro, and at least bacteriostatic effects in vivo. Iodinated silicone produced a protective effect against the morbidity of infection in the mouse.

Effects of local instillation of triamcinolone on the capsules around silicone bag-gel prostheses in animals.

"Soft" silicone bag-gel miniprostheses were implanted in 103 rats. The experimental animals had periprosthetic instillations of zero, 0.2, or 2 mg of triamcinolone acetonide at implantation. The compressibility, the architecture, and the chemical composition of the surrounding tissues were observed at 10 and at 120 days. The compressibility was also measured by mechanical means at 10 day intervals. At 120 days all capsules were similar. All the capsules gradually became firmer with time after the implantation. After 60 days, the steroid-treated capsules were very slightly more compressible (softer) than the controls. This slight difference in compressibility could not be correlated with the other changes in the capsule properties we examined. It is suggested that the structure of these capsules may be similar to that of immature scar, and that it is kept in this condition by the continued stimulus of the foreign implant.

Study of encapsulation of silicone rubber implants in animals. A foreign-body reaction.

It has long been known that the formation of a fibrous capsule around an implant is a general phenomenon in nature, an inevitable result of the tissue defense mechanism called the foreign body reaction. We have investigated this reaction in animals and find it consists of a series of interrelated processes in which the final result may vary, depending on the susceptibility of the foreign material to phagocytosis, incorporation by giant cells, or isolation by fibrosis. This susceptibility depends, in turn, on the physical and chemical properties of the implant. The process of capsule formation, as well as the structure of the final capsule, is similar in animal models and in humans--so that investigations of human encapsulation may be done in animals. The cause of abnormal induration around human breast implants is still unknown, and the question of whether normal induration in the animal model can be used to elucidate abnormal clinical induration depends on further investigation of both phenomena.

Treatment of exophthalmos.

Current procedures for Graves' exophthalmos fail to achieve complete correction. The standard orbital decompressions were therefore modified to maximize the degree of volumetric increase behind the axis of the globe. In 15 orbits, the preoperative exophthalmos averaged 9.5 mm, whereas the postoperative exophthalmos was 4.1 mm. Postoperative CT study demonstrated that the remaining posterior orbital wall, combined with the persistently increased intraocular muscle volume, blocked retrodisplacement of the globe, despite adequate total volumetric increase. The increased muscle volume varied from 2 to 5 cc. Despite this residual exophthalmos, the modified four-wall expansion provides excellent aesthetic results with visual improvement and resolution of chemosis and exposure keratitis.

The effect of commonly used antiseptics on wound healing.

Acetic acid, hydrogen peroxide, and povidone-iodine solutions were applied to experimental wounds in rats and to human donor sites to test their effects on wound healing. Control donor sites were treated with saline or dry Owens gauze. The acetic acid and povidone-iodine solutions had no significant gross or microscopic effect on the wounds. The hydrogen peroxide solution seemed to hasten the separation of the scab and to shorten the healing time, though characteristic bullae and ulceration appeared if the hydrogen peroxide treatment was applied after the crust had separated, when new epithelium was visible. We believe that the use of hydrogen peroxide should be avoided after crust separation. When only dry Owens gauze was used to treat split-skin graft donor areas, the result was a 3-day prolongation of the scab separation (compared to the saline controls) and greater subepidermal reactive and inflammatory changes.

The panniculus carnosus in the domestic pig.

The panniculus carnosus arises from the superficial fascia of the midlateral back, inserts into the medial skin of the forelimb, and fuses ventrally with the contralateral cutaneous muscle. In the midback, forelimb, thigh, and groin the panniculus carnosus is lacking; there, superficial fascia alone is present. Both the panniculus carnosus and the superficial fascia divide the panniculus adiposus into a superficial compact layer and a less compact deep layer. The firm attachment of the dermis to the panniculus carnosus, and of the panniculus carnosus to the deep fascia, makes pigskin a more suitable model for comparison with human integument than the usual laboratory animals with loosely draped skin. When using the pigskin model, however, care must be exercised to define the level of incisions and the location of flaps or grafts, with respect to the panniculus carnosus.

Excisional wound biomechanics, skin tension lines, and elastic contraction.

Confusion surrounding the concept of Langer's lines can be reduced by careful distinction among the operational definitions of the phenomenon, the empirical descriptions, and the theoretical explanations. An experimental analysis of the mechanical parameters of excisional wounds in pigskin shows that the marginal retraction, the elastic modulus at the wound midline, and the closing tension are higher for wounds oriented at right angles to tension lines--but the elastic modulus of the terminal segment of the force displacement curve is independent of orientation. The regional distribution of these values shows two patterns. The modulus parameters and the closing tension share a common distribution related to the steepness of regional force-displacement curves, while retraction has a qualitatively different distribution. On the basis of similarities in the behavior of retracting wound margins and in the distortion of punch holes which define tension lines, we hypothesize that the same mechanism may be responsible in both cases.