Pamela A. Foresman

Early Tissue Reaction to Textured Breast Implant Surfaces

Capsular contracture around breast implants with smooth surfaces continues to be an unpredictable complication. Some surgeons believe that silicone implants covered with porous polyurethane foam have a lowered potential to contract. These textured implants are not as biocompatible as silicone. Recently, silicone implants with textured surfaces have been introduced with the hope that the incidence of unacceptable implant contracture will be reduced. Using a rat implant model, the tissue reaction to textured implant surfaces was assessed. The implant surfaces evaluated were Silastic II, Siltex, MISTI, Biocell, Silastic MSI, and Mime. Disks of each implant material were implanted under the dorsal skin of rats for a period of 28 days. Each implant with its surrounding tissue was excised, processed for histological analysis, and assessed for the tissues response to the implant with particular emphasis on the formation of a continuous collagen capsule. The results indicated that the magnitude of surface texturing influenced the development of a complete capsule. Implant surfaces with a texture of less than 150 µm in height or depth (Silastic II, Siltex, and MISTI) resulted in the formation of complete capsules. An implant (Biocell) with irregular texturing (200-350 µm) produced an organized capsule over most of its surface with localized interruptions of the capsule at the sites of its deepest cavities. Implant surfaces with texturing that exceeded 350 µm in height or depth (Silastic MSI and Même) resulted in inhibition of the formation of a continuous capsule during this 28-day study.

Tissue adhesive wound repair revisited

The purpose of this experimental study was to compare the effect of a tissue adhesive, N-butyl-2-cyanoacrylate, on the wounds ability to resist infection and gain strength to the effect of percutaneous polypropylene suture. Percutaneous sutures damaged host defenses, inviting the growth of bacteria to a level that was significantly greater than that encountered with the tissue adhesive. Immediately after wound closure, percutaneous sutures provided a more secure closure, as measured by breaking strength, than did tissue adhesives. Seven days later, the breaking strengths of wounds closed by tissue adhesives did not differ significantly from those repaired with percutaneous sutures. Tissue adhesive closure requires less psychomotor skills than suture closure and is accomplished more rapidly than suture closure.

A new hazard of cornstarch, an absorbable dusting powder

Cornstarch is currently the only powder used in the manufacture of surgical and examination gloves. The purpose of this study was to determine if cornstarch damages local tissue defenses in contaminated wounds. It was found that in contaminated wounds, cornstarch enhanced the growth of bacteria and elicited exaggerated inflammatory responses as measured by wound induration. As a result of this investigation, we do not recommend the use of gloves with cornstarch powders.

Damage to tissue defenses by EMLA® cream☆

EMLA is a new topical agent that safely anesthetizes intact skin. The purpose of this study was to determine if this cream could be safely used for anesthetizing wounds. This investigation evaluated the potential toxicity of EMLA cream in wounds by measuring its effect on host defenses and on the biology of wound repair. In contaminated wounds, EMLA cream elicited an exaggerated inflammatory response that damaged host defenses, inviting the development of infection. As a result of these investigations, we do not recommend the use of EMLA cream in wounds.

Development of independent vessel security after ligation with absorbable sutures or clips

The external jugular vein and the contralateral carotid artery in each of 59 rabbits were ligated with either sutures or absorbable clips and then divided. After 0, 1, 2, 4, 7, or 14 days following ligation, the suture or clip was removed, and the vessels resistance to leakage was quantitated. When the absorbable clips were removed from arteries after 1 day, their mean resistance pressure prior to leakage was 171 +/- 46 mm Hg; in contrast, arteries ligated with a suture did not achieve independent security until after 4 days. At 4 days, the mean pressure prior to leakage of arteries with the suture removed was only 88 +/- 49 mm Hg. Similar results were obtained with veins. The difference in vessel security was attributed to the significant increase in the width of the vessel wall compressed when an absorbable clip was utilized compared with a strand of suture.

Modulation of mechanical properties in multiple-component tissue adhesives

In vitro, ex vivo, and in vivo studies were performed to investigate the effect of mixing upon the mechanical properties of a two-component tissue adhesive. The hypothesis investigated was that a more complete mixing of the two components would yield an increase in the mechanical performance of the adhesive. This in turn would be demonstrated by improved outcomes in models of clinical sealant application. In vitro stereological analysis of tissue adhesive mixed and delivered by several different applicators demonstrated variation in the amount of mixing provided by each type of delivery system. Ex vivo tensile adhesive strength showed that there was a correlation between the amount of mixing and bonding strength; that is, more thorough mixing demonstrated higher adhesive strength. No significant difference was seen, however, between the different applicator types and impact on in vivo dermal incisional closure strength. There was a correlation, though, in amount of mixing and in vivo hemostasis. In a rabbit spleen incision model, a more thoroughly mixed sealant corresponded with a decrease in time to obtain complete hemostasis, as well as less sealant used. The effects of mixing on tissue-adhesive mechanical performance were influenced somewhat by the amount of mixing provided by the applicator. This effect, however, was dependent upon the sealant formulation and the type of in vivo application.

Anesthetic properties and toxicity of bupivacaine and lidocaine for infiltration anesthesia

The purpose of this study was to measure the toxicity and anesthetic properties of two anesthetic agents, bupivacaine and lidocaine. These anesthetic agents did not damage tissue defenses or invite infection in experimental animals. In addition, the pain of subdermal injection, the onset of anesthesia, and the frequency of satisfactory anesthesia in human volunteers were remarkably similar. Because the duration of anesthesia induced by bupivacaine was nearly four times longer than that by lidocaine, bupivacaine is recommended for infiltration anesthesia of lacerations treated in the emergency department.

Quantitative monitoring of capsular contraction around smooth and textured implants

The purpose of this study was to assess the efficacy of textured silicone implants in reducing the incidence of capsular contracture. Each of 10 female New Zealand, albino rabbits received 2 saline-filled implants, 1 on either side of the lateral chest wall. The surface of 1 implant was smooth silicone, whereas the other implants surface was textured silicone. Magnetic resonance imaging (MRI) scans of the implants were performed at 0, 9, 17, 26, 34, and 40 weeks after implantation. Data from the MRI scans were used to calculate the effective surface area of implants at each analysis interval. This technique provided a noninvasive method of monitoring implant contraction as a function of time. Eight rabbits completed the study. Four of 8 smooth implants developed contractures, whereas none of the textured implants developed contracture. For the 4 smooth implants that developed contractures, MRI scans calculated 72 ± 12% contraction at 17 weeks, but the Baker palpation test detected only mild firmness. From 17 to 40 weeks, the mean percentage of contraction for these implants changed minimally, but their mean Baker score increased from mild to severe (II to IV). Quantitative data from MRI scans were much more predictive of final implant contraction than palpation (Baker test), applanation tonometry, or indentation tonometry. The latter two tests only detected the final stages of severe implant contraction.Brohim RM, Foresman PA, Grant GM, Merickel MB, Rodeheaver GT. Quantitative monitoring of capsular contraction around smooth and textured implants. Ann Plast Surg 1993;30:424–434