The importance of 3rd party review sites seems to have become less important... Google has raised the prominence of Google Reviews and dropped the relevance of 3rd party sites like Yelp and DemandForce. What does it all mean? We're probably going to be pursuing Google Reviews more and looking for 3rd party links less. Granted, links still help SEO but looking forward Google links seem to matter the MOST.
SearchEngineLand.com has written a GREAT article on this new development. Check it out - it really applies to elective medicine and local businesses...like yours.