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A Real-Time Local Flaps Surgical Simulator Based on Advances in Computational Algorithms for Finite Element Models

Mitchell, Nathan M.; Cutting, Court B. M.D.; King, Timothy W. M.D., Ph.D.; Oliker, Aaron M.S.; Sifakis, Eftychios D. Ph.D.

Plastic and Reconstructive Surgery: February 2016 - Volume 137 - Issue 2 - p 445e–452e
doi: 10.1097/01.prs.0000475793.38984.7e
Special Topics: Educators Series

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.

Supplemental Digital Content is available in the text.

Madison, Wisc.; and New York, N.Y.

From the Department of Computer Science, University of Wisconsin; Division of Plastic Surgery, University of Wisconsin Medical Center; Department of Plastic Surgery, New York University Medical Center; and Biodigital Systems, LLC.

Received for publication June 2, 2015; accepted August 13, 2015.

Disclosure: Skin and scalp flap models were produced by Aaron Oliker with Dr. Cutting during his tenure as chief animator in Dr. Cutting’s computer graphics laboratory at New York University Medical Center. Aaron Oliker is now a principal at Biodigital Systems, Inc. Biodigital Systems did not produce any of the software or models used in this article. None of the authors has a financial interest in any of the products, devices, or drugs mentioned in this article.

Supplemental digital content is available for this article. Direct URL citations appear in the text; simply type the URL address into any Web browser to access this content. Clickable links to the material are provided in the HTML text of this article on the Journal’s Web site (

Court Cutting, M.D., Department of Plastic Surgery, New York University Medical Center, 550 First Avenue, New York, N.Y. 10016,

©2016American Society of Plastic Surgeons