Nondisruptive, in vivo method for biomechanical characterization of linear incision wound healing: preliminary report

Previous work on in vivo biomechanical characterization of soft tissues and wound healing has led to the development of a methodology for nondisruptive, in vivo biomechanical analysis of linear incision wounds. The purpose of this preliminary study was to define nondisruptive biomechanical parameters that characterize progressive healing and compare them with an in vivo disruptive parameter of ultimate pressure at failure (in vivo strength). Male Sprague-Dawley rats (n = 60), each weighing 250 to 300 gm, were anesthetized and underwent creation of paired full-thickness linear incision wounds. The rats were divided into three groups (n = 10/group per time period): control group, nothing applied to either wound; carrier group, bovine serum albumin applied to each wound; transforming growth factor-beta2 group, transforming growth factor-beta2 in bovine serum albumin applied to each wound. On postoperative days 5 and 10, rats from each group underwent in vivo biomechanical testing using the Dimensional Analysis System (Dimensional Analysis Systems, Inc., Nashville, Tenn.). This computer-driven device integrates a video camera and processor with a vacuum controller, valve, and transducer to provide measurements of tissue deformation (in millimeters) and negative pressure (mmHg) as a multiaxial stress (vacuum) is applied to a wound. On each rat, one incision was tested disruptively and the other incision was tested nondisruptively. Disruptive data were measured as ultimate pressure (mmHg) at failure, or the amount of pressure required to disrupt the wound. Nondisruptive data were measured for tissue stiffness (kiloPascals) during application of negative pressure (maximum, 80 mmHg). On postoperative day 5, wounds treated with transforming growth factor-beta2 had significantly increased in vivo wound strength compared with carrier wounds. The nondisruptive parameter of tissue stiffness was also significantly increased for the transforming growth factor-beta2 treated wounds, thus supporting the disruptive data. On postoperative day 10, there was no difference in mean wound strength or mean tissue stiffness among any of the groups. These preliminary data represent the first report of in vivo, nondisruptive biomechanical characterization of linear incision wounds. The results suggest that through in vivo measurements of tissue stiffness, differences can be detected between treatment groups. Because the healing wound may be characterized without the need for disruption, this methodology should allow for consecutive, in vivo biomechanical testing of wounds in future wound healing studies.