Arthrodesis and Defect Bridging of the Upper Ankle Joint with Allograft Bone Chips and Allograft Cortical Bone Screws (Shark Screw) after Removal of the Salto-Prosthesis in a Multimorbidity Patient: A Case Report.

The case describes the revision of an upper ankle prosthesis because of loosening. When ankle replacement is the first choice and actual bone quality does not allow a replacement of the prosthesis, arthrodesis is the only way of reducing pain and gaining stability. The amount of missing bone due to the removed prosthesis was severe. Shark Screws, made of human allograft cortical bone, were used to fix an allograft femoral head and tibia as well as fibula and talus to each other for stabilization. This was performed without any autologous bone graft and without metal screws. The human matrix of the cortical allograft allows the creation of new vessels followed by osteoblastic activity and production of new bone. The revascularization of the allografts reduces the risk of infection and wound problems. Over time, the patient's bone metabolism allows the allografts to be remodeled into the patient's bone. The case reported here had severe multimorbidity. The loosening of the prosthesis mainly affected the ability to perform housework, mobility, enjoying leisure, and it had a great impact on the emotion and well-being of the patient. One year after surgery, the patient is very satisfied to be able to walk without pain and scratches for about 90 min.