One embodiment of the invention includes a sinus tarsi implant with an inverted thread profile having a lip or lips at the thread crest. The lips may help hold tissue in-growth and give greater purchase to the implant. The implant may also include voids that traverse threads. The voids may create an open area for soft tissue to grow into. The voids may be relatively small and consequently promote faster tissue in-growth. Thus, the lips and/or voids limit migration. They do this without creating sharp edges or pressure points (or at least limiting such creation) that are typically associated with techniques (e.g., cutting deep negative thread spaces) used to prevent migration. Therefore, the embodiments of the invention limit migration while also limiting patient discomfort. Other embodiments are disclosed.
