My wife and I were both track cyclists. 4 years ago her lower back totally crapped out in the SI joint. She was dangerously close to being in a wheelchair. After a very long path of different physiotherapists, massage, acupuncture and doctors and not really getting any better she was directed to a "Feldenkrais" practitioner who has worked miracles. She is able to work again and have a decent life.
Sorry to hear about your wife's misfortunes but glad to hear she's ok now. If it's not too personal, would you mind sharing some details of her story? For example, what kind of racing was she doing? What kind and how much supplemental training (weight training, plyo, etc.) was she doing? What was her athletic history like? Did she have any pre-existing back issues? Was this a chronic/cumulative type injury or a sudden catastrophic injury? Any details you share could be helpful for others on here (and me). Thanks for sharing.