| 1. Objective The purpose of the research was to obtain biomechanical parameters of human skin. To build four ideal 3-D finite element models for four kinds of commonly used local skin flaps. To build virtual reality 3-D finite element models for local skin flaps. Simulate the deformation of the local skin flaps during surgery and after surgery. Find out mechanical laws in the process of deformation and sewing of local skin flaps by simulating. Help clinical surgeons to design skin flaps before surgery. Help to improve the utilization rate of skin flaps. Help to reduce complications.2. Methods Find the biomechanical parameters of discarded human skin by biomechanical experiments. Build the 3-D finite element models for local skin flaps by MSC.Marc/Mentat 2005(a kind of 3-D finite element software), including four ideal 3-D finite element models for four kinds of commonly used local skin flaps:advancement skin flap, rotation skin flap, rhomboid skin flap, Z-plasty transposition flap. Scan patient's surgical area skin to obtain the three-dimensional images. Build patient's virtual reality 3-D finite element models for local skin flaps by Geomagic Studio 8.0(a kind of 3-D image analysis software) and MSC.Marc/Mentat 2005. Simulate the process of deformation and sewing of local skin flaps during surgery by using bio-mechanical parameters of human skin and models of local skin flaps. Figure out post-operative local stress of skin and wound tension in different models, paint colorful pictures about local stress distribution and wound tension distribution. Find out which is the factor that can influence final results by changing incisions, wound position and material properties of skin in the models.3. Results Have painted the stress-strain curve of human skin. Have painted colorful pictures about postoperative skin displacement, local stress distribution and wound tension distribution on the basis of simulation. The results of changing incisions, wound position and material properties of skin in the models are:1) When an advancement skin flap stretched over 50% of its initial length, the maximal stress could exceed the yield limit, and the plastic deformation can occur to skin flap.2) When a fan-shaped skin flap with central angle of 60°rotate over 30°, the maximal stress could exceed the yield limit, and the plastic deformation can occur to skin flap.3) Z-plasty transposition flap with angle of oO°can get more extending rate, but it have higher local stress and greater wound tension than Z-plasty transposition flap with angle of 45°postoperatively.4) Local skin flap model with the material parameter of human forehead skin have higher local stress and greater wound tension than model with the material parameter of human anterior thigh skin postoperatively.5) A virtual reality 3-D finite element model can simulate the skin deformation and tension distribution of a patient.4. Conclusions The stress-strain curve of human skin doesn't meet the linear rule. An advancement skin flap should not stretch over 40% of its initial length if we don't consider blood supply of it. A fan-shaped skin flap with central angle of 60°should not rotate over 30°if we don't consider blood supply of it. For Z-plasty transposition skin flaps, flap with angle of 60°has better ability than flap with angle of 45°to reduce postoperative stress and tension in the scar's direction. Different parts of human skin have different results in blood supply and survival ratio postoperatively even if they have the same incision design. The chief factors of postoperative distribution of stress and region of incision tension are contour of surgical area and incision design, and have nothing to do with the material parameters of skin. It's an effective and workable way to simulate local skin flaps by 3-D finite element models with biomechanical parameters of human skin. Virtual reality 3-D finite element model can predict patients'postoperative skin deformation and tension distribution correctly by simulation. |
PDF Full Text Request