Attaining a Biologically Stable Stoma at the Implant Exit Site of a Percutaneous Osseointegrated Prosthesis
Abstract
This proposal addresses the FY20 PRORP Rehabilitation Focus Area, namely, Osseointegration: Identification of best practices to address infection, rejection, and/or failure of percutaneous osseointegrated prosthetic limbs.” The skeletal docking of artificial limbs has been in clinical use in Europe for 30 years, but has yet to be fully approved by the FDA for use in the United States. Several types of percutaneous osseointegrated devices (OI) are currently undergoing clinical trials in the United States, and avoidance of infection is requisite for clinical approval of these implants. The exit point of the connecting shaft of the device (known as the stoma) is the site that is vulnerable to infection. Obtaining a stable physical or biological seal that prevents bacterial ingress at the stoma is essential to device survival. The ability to establish a biologically stable stoma by attaching the skin directly to a device surface has never been achieved. This weak link occurs because of the intrinsic processes of wound healing. As skin cells (“the epithelium”) heal around the percutaneous device, this tissue fails to adhere directly to the device surface because the cell cannot recognize the artificial surface as “biological” tissue. These epithelial cells instead grow deeply along the implant surface; a process termed epithelial downgrowth or marsupialization. Aschoff and his co-workers reported in a clinical cohort study that infection at the stoma was essentially prevented when surgical conditions are established during the first stage surgery, which will ultimately lead to shallow stomata. His surgical technique requires stump revision and thinning of the distal soft tissues at the time of implantation of the osseointegrated portion of the endo-prosthetic device. We have observed similar findings in a 10-patient FDA-approved clinical safety trial (now further approved for a 120 patient Phase 1 Trial). These clinical observations prompted us to ask the question of whether or not epidermal cells can migrate deeply within the stoma, recognize transected bone tissues (i.e., cortical bone or periosteum) as “biological surfaces,” and then form a mature functional attachment to the bone, thus preventing infection. At present, there is no translational animal study that proves this concept. Our experimental approach is to show that accelerating epidermal downgrowth along an ultra-smooth “low-energy” ceramic zirconia surface during the early stages of stomal wound healing will “fast-track” epidermal migration toward the bone surface and that attachment to this viable bone will promote a non-migrating seal of the skin to the bone at the deep bone/endoprosthetic interface. We feel that this condition will ultimately allow the completion of mature stomal wound healing. We believe that this “paradigm shift,” i.e., taking advantage of the biological processes intrinsic to stomal wound healing by accelerating rather than attempting to slow the epithelial downgrowth and promoting epidermal attachment to the transected bone interface, will produce a seal that is key to maintaining a stable percutaneous stoma that is free from infection. Second, once this seal is established, distal bone also needs to be maintained. Currently, only the Utah device design can maintain distal bone post-implantation. We propose to test the following general hypothesis: “When the stomal skin adjacent to the percutaneous shaft of an osseointegrated prosthetic device, as part of the innate wound healing response, migrates deeply within the stoma and ultimately achieves a mature circumferential integration with the distal bone surface, the risk of subsequent infections will be mitigated.” This proposed study is therefore designed to investigate the ability of zirconia (zirconium oxide) surfaces that facilitate rapid, continuously viable epidermal migration to develop a biological seal at the perimeter of the bone/implant interface and to determ
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 05, 2021
- Source ID
- W81XWH2110667
Entities
People
- James Beck
Organizations
- United States Army
- Western Institute For Biomedical Research