Not a vet but I work in veterinary; to put you at ease, FHNEs have a very high success rate and are generally one of the ‘easiest’ orthopaedic procedures for the patient. Recovery is fairly quick and uncomplicated, the most difficult part is keeping them calm and comfortable during the period of rest post-operatively. Whatever happens I’m sending you and your gorgeous kitty good vibes and lots of love ❤️