The Development of a Porcine Model to Evaluate Wound Healing and Infection of Transcutaneous Osseointegrated Weight-Bearing Prostheses

Abstract

Clinical studies have shown that up to 73.9% of the 1.04 million US lower limb amputees report skin problems such as sweating, irritation, and sores associated with their conventional prosthesis. An alternative option redirects ambulatory forces back to the skeleton using an implant that permanently protrudes through the skin (transcutaneous) to enable direct bone anchorage (osseointegration) of a prosthesis. Transcutaneous osseointegrated prostheses show a marked improvement in amputee acceptance over conventional prostheses. Advantages include limited tissue breakdown, a non-restricted range of motion, and enhanced functionality. However this prosthetic option has not been clinically implemented in the United States because of infection concerns and an incomplete understanding of transcutaneous wound healing. Being a potential state-of-the-art altering surgical option for trauma-induced amputees, transcutaneous osseointegration will require preliminary animal studies. To evaluate the efficacy of the transcutaneous osseointegrated option, a physiologically- similar, axially-loaded, weight bearing animal model was developed. Two pigs were fit with transcutaneous osseointegrated prostheses in a single-stage amputation and implantation surgical procedure. Clinical, microbiological, and histological data were examined to assess wound healing and infection at the skin-bone-implant interface. The animals achieved 70% and 67% pre-operative weight-bearing. Bacterial cultures indicated a likely deep tissue infection in one of the two animals. The transcutaneous wounds were in the proliferative phase of wound healing by the end of the 35 and 56 day studies. The epithelial skin layer was migrating towards the implant in one animal. Results obtained from the animal model will be used to implement future topographical and material changes at the transcutaneous site. The porcine model should become the standard for implementing and testing future iterations of weight-bearing transcutaneous osseointegrated prosthetic devices.