Background: This article presents a real-time surgical simulator for teaching three- dimensional local flap concepts. Mass-spring based simulators are interactive, but they compromise accuracy and realism. Accurate finite element approaches have traditionally been too slow to permit development of a real-time simulator.

Methods: A new computational formulation of the finite element method has been applied to a simulated surgical environment. The surgical operators of retraction, incision, excision, and suturing are provided for three-dimensional operation on skin sheets and scalp flaps. A history mechanism records a user's surgical sequence. Numerical simulation was accomplished by a single small-form-factor computer attached to eight inexpensive Web-based terminals at a total cost of $2100. A local flaps workshop was held for the plastic surgery residents at the University of Wisconsin hospitals.

Results: Various flap designs of Z-plasty, rotation, rhomboid flaps, S-plasty, and related techniques were demonstrated in three dimensions. Angle and incision segment length alteration advantages were demonstrated (e.g., opening the angle of a Z-plasty in a three-dimensional web contracture). These principles were then combined in a scalp flap model demonstrating rotation flaps, dual S-plasty, and the Dufourmentel Mouly quad rhomboid flap procedure to demonstrate optimal distribution of secondary defect closure stresses.

Conclusions: A preliminary skin flap simulator has been demonstrated to be an effective teaching platform for the real-time elucidation of local flap principles. Future work will involve adaptation of the system to facial flaps, breast surgery, cleft lip, and other problems in plastic surgery as well as surgery in general.