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The rate of diffusion of benzyl alcohol (the bacteriostatic agent in the provided diluent) and methylprednisolone 21-hemisuccinate and related rearrangement and hydrolysis products ("steroid") through tissue expanders was examined. The rate of diffusion of steroid through double lumen breast implants was also studied. It was found that benzyl alcohol rapidly diffused through tissue expanders into a saline bath. By 24 hours, one-half of the benzyl alcohol had diffused through the expander. The steroid was much slower to diffuse out of the expander. By 141 days, only 2% of the steroid was found in the bath. This rate was comparable for both the tissue expander and double lumen implants. In addition, a significant amount of the steroid is located in the expander wall, associated with the surface of the expander or precipitated out of solution or both. The clinical significance of these findings is discussed.

Previous work in our laboratory has demonstrated that tissue expanders are permeable to lidocaine. In this two-part study, we assessed the in vitro lidocaine diffusion in the following five common tissue expanders: Dow Corning, McGhan, Cox-Uphoff, Hyer-Schulte (Mentor), and Surgitek. In part 1, we demonstrated that wall thickness appeared to be the major determinant for diffusion. Part 2 reports an in vivo study of lidocaine diffusion from tissue expanders used for breast reconstruction. We initially determined that there is incomplete mixing between the valve and connecting tubing and the contents of the expanders, over the period of 1 week. We subsequently examined the lidocaine diffusion from seven tissue expanders placed in a submuscular position for breast reconstruction. The rate of lidocaine diffusion was highly variable, but on average was about 3% per day.

Reconstruction of the burned penile urethra has received scant attention in the surgical literature. Techniques used in repairing congenital hypospadias may not be applicable in this situation. We describe a dartos musculocutaneous island flap used to reconstruct the distal burned penile urethra in a 13-year-old boy who sustained burns to 85% of his total body surface area. Reconstruction was completed in one surgical procedure, and at two-year follow-up good results were demonstrated.