Lars M. Vistnes

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.

An In-depth Look at Pressure Sores Using Monolithic Silicon Pressure Sensors

Three-dimensional scalar pressure distributions were measured in solid tissue near bony prominences in vitro in meat and in vivo in pigs using silicon pressure sensors. Data are in accord with previous theoretical models and indicate that pressure is three to five times higher internally near a bony prominence than it is at the skin over the prominence. Pressure sores are thus thought to begin internally; by the time they are evident at the skin, the sore has worked its way completely from bone to skin. This conclusion is in accord with previous clinical data. Future measurement of local vector forces is needed to fully characterize the force distribution in vivo.

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.

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.

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.

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.

Coccidioidomycosis Tenosynovitis in the Hand

A patient with disseminated coccidioidomycosis with acute palmar tenosynovitis is presented. Early synovectomy followed by amphotericin B therapy was carried out and is recommended for treatment of coccidioidomycosis tenosynovitis. The association of an exacerbation of coccidioidomycosis in a patient with a history of coccidioidomycosis treated with immunosuppressive drugs is described. Prophylactic amphotericin B therapy is recommended for such patients.

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.

USE OF VASTUS LATERALIS MUSCLE FLAP FOR REPAIR OF TROCHANTERIC PRESSURE SORES

The use of a vastus lateralis muscle flap is suggested as an approach to the surgical repair of trochanteric pressure sores in paraplegic patients. The details of the anatomy of the muscle are outlined, and our surgical technique for its use is described.

The long-term effects of hard alloplastic implants when put on bone.

The resorption of bone beneath 4 alloplastic materials has been studied for periods up to 18 months in rabbit skulls. When the effects of pressure were negated, there was no significant difference in bone resorption attributable to placement above or below the periosteum. Dacron backing or polyurethane backing were associated with more inflammation and greater bone reaction than were plain silicone or stainless steel. The changes noted at 18 months were essentially the same as those noted at 6 months.