Is Amputation Or Fusion Recommended After Failed Knee Replacements Due To Infection?

My Dad is facing his 4th total knee replacement in his right knee. They keep getting infected. Dad has Lupus, Osteoperosis and Rheumatoid Arthritis. I personally do not believe it is worth the 4th attempt. Dad has had in excess of 30 general antisthetics already. If faced with Amputation or Fusion what would your recommendation be? Can you recommend somewhere where I can gain further information?