Online-first articles do not yet have volume, issue, and page numbers. They receive the volume number, issue number and page number when they are assigned to an issue. Your Open URL link handler should use the DOI (Digital Object Identifier) to make the links, the DOIs always work, even for online-first articles.
For example: http://link.springer.com/article/10.3103/S0967091215070116
Where the DOI is: 10.3103/S0967091215070116
See also: Link in to content on SpringerLink