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A study has been undertaken to investigate Prostaglandin E1 administration procedure for improving flap survival. Whether the drug was administered continuously or transcutaneously using a silicone gel drug delivery system; or was topically injected into the critical zone of the flap; or was intraperitoneally administered intermittently over an hour after surgery a statistically significant improvement of flap survival occurred (P < 0.01, Student's t-test). However, no improvement of flap survival was seen when the drug was administered only once intraperitoneally immediately after flap elevation, although administered doses of the drug in those rats was equal to the doses in the rats which received intermittent administration of the drug intraperitoneally over an hour after surgery.

From a drug delivery system using silicone gel, the amount of Ofloxacin (OFLX) released or transferred to a wound and blood was measured over 2 weeks. From three types of silicone gel containing 2, 0.2 and 0.02% OFLX respectively, levels from that with 2% OFLX were highest, approximately two to five times higher than that with 0.02% OFLX. Statistically significant differences were found between the three types (P < 0.01, Student's t-test). When used in partial thickness skin wounds on rats, only an extremely small amount of OFLX was detected in the serum, being higher under gel containing 2% OFLX. In a clinical study, however, no drug was detected either in the blood or the wound after 1 week.

Using 60 Hirosaki hairless rats, the relationship between the time of starting topical administration of Prostaglandin E1 using silicone gel and flap survival rate is described. Compared to control groups, beginning the administration of PGE1 at 0 (P < 0.01) and 3 h (P < 0.05) after flap elevation resulted in an increased flap survival area (Student's t-test). However, in groups in which PGE1 administration was begun at 6, 9 and 12 h after flap elevation, no statistically significant differences could be detected.

In 31 patients with hypertrophic scars or keloids, a side by side test was carried out to check the efficacy of an occlusive dressing technique using cream which did not contain silicone oil, versus a simple application of vaseline, used as a control. In all cases, the cream treated areas of scar and keloid demonstrated a remarkable improvement over that of the vaseline treated area. These findings strongly suggest that the mechanisms of hydration and occlusion are the main basis of the therapeutic action of this method in treating hypertrophic scars and keloids.

To evaluate the beneficial effects of heparin on flap survival area, an experimental study was carried out on dorsal flaps in rats. Topical applications of heparin, released from a silicone gel sheet onto the critical area (which generally necrosed without treatment), resulted in an increase in the flap survival area and rate as compared to controls (p < 0.01). When heparin was applied topically but solely to an area proximal to the critical area however, no increase in the survival area resulted.

Using a silicone gel sheet continuous drug delivery system containing Prostaglandin E1 (PGE1), the relationship between flap survival rate and the site of drug application was studied. Skin flaps measuring 2 x 9 cm were raised on the dorsum of rats, and divided into 3 areas. Area 1 was within 3 cm of the flap tip, area 2 was between 3-6 cm from the flap tip including the critical zone, and area 3 was the portion within 4 cm of the flap base. Further, area 4 was a strip of skin around the flap, 1 cm in width. Compared to the control group, a significant increase in flap survival rate was seen only when PGE1 was administered to area 2 (p < 0.01, t-test). Specimens injected with dye intravascularly showed an increase in the number of thick vessels in area 3, when PGE1 was applied only to area 3. However, when PGE1 was applied to area 2, there was no significant vascular increase in area 3. Instead, an extensive network of fine vessels was observed in area 2.

The clinical effects of silicone cream were compared to vaseline on 27 patients with split (14 cases) and full thickness (13) skin grafts. Silicone cream occlusive treatment resulted in significantly less pigmentation and hardness in 21 out of 27 cases (78%), less marginal scar hypertrophy and redness in 10 and 7 cases respectively (37 and 26%), and in an even narrower marginal scar in 6 cases (22%). In nine cases of the split skin graft, fewer wrinkles resulted in the silicone cream treated lesion.

In experimental and clinical studies we showed that obstruction of closed suction drainage tubes is often caused by clots. To prevent this we describe a tube coated on the inside with a silicone gel drug delivery system, which releases anticoagulant drugs. It prevents coagulation and liquefies blood clots present in the tube. This device should thus find application as a tube for continuous suction drainage systems.

The clinical effect of silicone cream containing 20% of silicone oil was tested on 47 patients with hypertrophic scars and keloids. A silicone cream/occlusive dressing technique, quite similar in manner to silicone gel treatment, resulted in a remarkable improvement of scars and keloids in 9 of 11 cases (82%) whereas the simple application of the cream onto the scars and keloids of 36 cases resulted in only mild improvement in 8 (22%). Using the chi-square test, a statistically significant difference was seen between these two treatments (p less than 0.01). From these findings, we suggest that occlusion and hydration are the principal modes of action of the silicone gel sheet method and our silicone cream/occlusive dressing technique.

Silicone gel sheets containing Ofloxacin (OFLX), that provide a continual drug delivery system from a wound dressing to the wound so as to prevent infection and to promote healing, are described. It was found that silicone gel sheets without added medication did not inhibit microbial growth but that gel sheets containing 0.02% and 0.2% of OFLX had a positive antimicrobial effect against Staphylococcus aureus and Pseudomonas aeruginosa in a dose-dependent fashion in vitro. Further, this antimicrobial efficacy was greatly increased in a silicone gel sheet that contained 0.02% of OFLX and an additional 10% of silicone oil. In animal experiments, a silicone gel sheet containing OFLX prevented microbiol growth and promoted rapid epithelialisation in wounds to which Staphylococcus aureus had been applied, whereas wounds covered only with OpSite all resulted in continued infection.

A new procedure using a silicone gel sheet that enables the continuous topical application of a drug to a wound, and the effect of this therapeutic procedure on experimental skin flaps of rats, are described. Although a silicone gel sheet without a drug did not augment the flap survival length, silicone gel sheets containing Prostaglandin E1 (PGE1) and Ofloxacin showed significant elongation of the survival length of the flaps without signs of infection. Similarly, silicone gel sheets containing PGE1 inserted under the flap, like a drain, also showed statistically significant augmentation of the flap survival length. These facts showed a therapeutic potential of this new silicone gel sheet containing a drug.

Treatment of a split thickness donor site wound in 20 patients by means of a silicone gel sheet containing Ofloxacin, an antimicrobial agent, has been tested. For a comparison, each wound was divided into two parts, one for the silicone gel treatment and the other with a collagen sheet (10 cases) or an ointment-impregnated gauze (10 cases). Although Staphylococcus aureus was detected in three wounds treated with the collagen sheet, no wound treated with the silicone gel developed an infection even though the infected wound was adjacent. Results have shown that prompt epithelialisation occurred in the silicone gel-covered wounds, with little exudate and pain compared to wounds treated with either of the dressings. Although some wounds treated with the silicone gel tended to exhibit a slightly prolonged redness compared to wounds treated with an ointment-impregnated gauze, no subsequent cosmetic problem resulted.

The biggest problem of the TRAM flap for breast reconstruction is distal necrosis or fat lysis due to poor circulation. In order to utilise the entire TRAM flap tissue in extensive tissue defects, the contralateral rectus muscle is used as a pedicled carrier and the ipsilateral superficial or inferior epigastric vessels are anastomosed with appropriate recipient vessels in the axilla. This procedure has been performed in three cases with no necrosis, fat lysis or hardening of the flap tissue, proving adequate circulation in the flap.