There's another article that explains that it wasn't just the battery. After the company went under, there was nobody who could provide support for the product in the event of malfunction. Removal was recommended as the safest course.

This isn't an "FDA problem". The device was investigational, which means it did not have final FDA approval. Consequently, there is no guarantee that a surgeon would have the knowledge to maintain it. Surgeons are not expected to be familiar with every experimental device, in fact most surgeons will never touch any experimental device.

And no, surgeons aren't just going to read a bunch of documentation to get up to speed. Typically, when a new product launches the manufacturer will send their technical representatives into the operating room to help troubleshoot any issues.