Improved interfaces for prostheses to improve rehabilitation Attaching exo-prostheses directly to bone-anchored, osseointegrated implants that pass percutaneously through the skin is being considered as an alternative to common socket-type technologies for individuals with limb loss. One of the primary failure modes of load bearing, percutaneous osseointegrated implants is the development of infection at the skin-implant interface. Thus, the success of osseointegrated prostheses as a potential clinical treatment relies heavily on establishing a skin seal to maintain a natural barrier to infection at this interface. This is a major challenge that must be addressed before this technology can be safely introduced into the United States. Notably, our current research studies have shown that a subdermal, porous coated barrier can initially attach to the skin and prevent infection for up to nine months. This data also shows that skin migration becomes a common occurrence at the periphery of the percutaneous post at a rate of 1.6?0.5 mm/month. Moreover, histological examination of the skin-implant interface revealed that the epithelial rete ridges adjacent to the percutaneous post were flattened and devitalized with the absence of an underlying vascularized papillary dermis. The epithelial flattening around a healing wound is a normal event, but persistent presence of flattened rete ridges, even after a post operative period of 6 months as seen in our studies, remains clinically concerning. These observations indicate impaired wound healing, which may be the probable reason for the observed skin migration along the subdermal barrier. It is believed that one of the reasons for this phenomenon is the lack of blood supply due to a non-physiological, regional strain field. The physiological micromechanical forces of skin tissue have been shown to establish localized stress-strain fields. Changes to the physiological strain fields due to skin defects stimulate wound healing by promoting cellular proliferation, migration of epithelial cells, and angiogenesis. It is therefore hypothesized that in order to maintain a healthy skin tissue barrier at the skin-implant interface, the local strain fields of the skin tissue need to be maintained. The primary goal of this proposed research program is to develop and validate the efficacy of a mobile, porous coated dermal barrier to maintain the natural strain field and to confer a stable infection free skin attachment in percutaneous osseointegrated implants. Therefore, the major hypothesis to be tested will be that by allowing the skin to maintain a physiological strain field near the porous coated subdermal barrier, the skin seal will be maintained and skin migration will be prevented.
In Aim 1, a percutaneous implant with a dynamic, porous coated subdermal disk will be designed and fabricated that will maintain regional physiological motions of the skin. Using pigs for this model, rates of infection will be compared to a control group (static subdermal disk).
In Aims 2 (a) and 2(b), the ability of the dynamic, porous coated subdermal disk group to maintain a skin seal and subsequently prevent skin migration will be histologically and biomechanically measured, assessed clinically over 3 and 6 month time periods, and compared to a control group. The projected lifetime health-care cost associated replacement of prostheses for patients who have undergone one limb loss is approximately $500,000. With the establishment of infection-free osseointegrated prosthetic technology, health care costs could be significantly reduced and the lives of 1.7 million amputees could be improved immensely.
The projected lifetime health-care cost associated replacement of prostheses for patients who have undergone one limb loss is approximately $500,000. With the establishment of infection-free osseointegrated prosthetic technology, health care costs could be significantly reduced and the lives of 1.7 million amputees could be improved immensely.
| Holt, Brian Mueller; Betz, Daniel Holod; Ford, Taylor Ann et al. (2013) Pig dorsum model for examining impaired wound healing at the skin-implant interface of percutaneous devices. J Mater Sci Mater Med 24:2181-93 |
