I realise I wasnt there and you were focused on your dog, but if the ridgeback turned on you at any stage, the first thing you need is your hand covering your throat. Thats the first place a dog will attack if it means business.
Here in Australia, where dogs are likely to come into contact with wild pigs or kangaroos, they use wide leather collars the protect the dogs throat. maybe you could invest in something to protect your dog.
As for other means of protection, start with a heavy stick, but knowing ridgebacks you could hit one across the back of its head with full force and it would barely know you are there.
Available over here is an electronic sounding device designed to hurt a dogs hearing. These are marketed to stop dog attacks and video footage I've seen shows a dog in full attack mode stop instantly. Might hurt your dog in the process, but both dogs wont be looking at each other after you press the button, and they will survive.
Another cheaper alternative would be to fill a small water pistol, something like the small Super Soaker range, with citronella. Dogs seem to hate it. With the range of those water pistols you could give the aproaching dog a dose in the face before it had a chance to bite.
And you can also try yelling at the other dog at the top of your voice as if you are the one in control.(full scream might be a better description)
The idea being to confuse the other dog, so use standard dog control type commands. "Sit Down and shut up" would be the first thing coming out of my mouth. Ive made guard dogs back down that have charged up to a fence by yelling back at them. If they think they are doing wrong or if you make them think that, they soon back off. Mind you I wouldnt have tested it without the fence being there <img src="/images/graemlins/smile.gif" alt="" />