This is an Ananova story. Which means that it's not very likely to be true:

Bit of a fix for bride and best man...
Doctors had to be called to separate the bride and best man after they were caught in the act during a wedding in Croatia.
The couple were trapped together by a muscle spasm after a friend of the groom walked in on them as they had sex in the toilets.
Unable to be pulled apart, the couple had to endure a procession of wedding guests who came to see what they had been doing before doctors could turn up.
Unable to help, they had to transport the pair on a stretcher to the local hospital where she was given an injection to relax her muscles, allowing the best man to get free.
The wedding party in Varazdin, Croatia, continued after the groom announced the celebrations were to mark his divorce rather than his wedding, reported daily Slobodna Dalmacija.

Tales of 'muscle spasms' locking couples together have been circulating for centuries. I think they're an urban legend, although vaginismus itself is a real enough disorder.

A similar tale appeared in an 1884 issue of Medical News, penned by a Dr. Egerton Yorrick Davis, who was the pseudonym of Dr. William Osler, a famous Professor of Medicine at Johns Hopkins University. Osler liked inventing strange stories like this and submitting them to medical journals using his Yorrick Davis alias. He did it throughout his entire career. If anyone has evidence of a real documented case of vaginismus locking a couple together, I'd like to hear about it.