Pin compatible means that the plug fits. My Antec 900 cases have an HDA plug on the end of the case audio jacks. It also has an AC'97 plug daisy chained off the end of that. What the motherboard provides determines your choice.
You may be able to contact the case manufacturer and get a replacement front audio panel. Motherboard? If you are lucky, the audio i/o jacks still work.
Otherwise, I think you are out of luck.
thanks for your helpful reply. I will go and see what can be done. If nothing else I have learned something!!???