Well there's a couple of different things in play there.
First, by a positive PMS statement, I mean in comparison to saying nothing at all. Even for a well-established product, you can still demonstrate you have done your (annual-ish) due diligence from the regular sources of market feedback.
Secondly, a well-established device is unlikely to have a lot of recent (or perhaps even ancient) clinical papers describing its efficacy, however you may be able to demonstrate that it is so ubiquitous and well-established that its use is taught as standard in medical schools and the like. Use your experience and expertise to make that case, backed up with appropriate data.
Finally, I would recommend manufacturers of such devices consider Annex X 1.1.1.d as a start-point, can the safety and efficacy of the device be justified without a clinical evaluation being performed?