I have 1.5/4.5 million (which I pay 90k for) and have no malpractice suits or claims in 20+ years of being an MD so that infintesimal risk wouldn't worry me in the least. I do a lot more off label potentially risky stuff than bovine thrombin injections. As an example vascular stents were used for years (by myself and many others) with only an approved biliary indication. We knew the stents worked and saved people surgical operations and inproved their quality of life. We used them in the arterial and venous circulation when appropriate long before the FDA granted approval.
All in all there are alot more important medical issues to solve than replacing bovine thrombin.