Powershell and page editing

I am looking for a way to edit the content of a wiki page using powershell.

I have been able to successfully replace the _entire_ aspx page with different content, but that looses all the goodness that SharePoint provides.

Essentially I am getting content from an html file and I need to load it into a blank sharepoint wiki page.  I can create the page, just need to find a way to load the content in.

Could anyone assist?

SharePoint 2013