Hi, thanks for your query. Myasthenia gravis is not acquired because of any surgery or infection. Ita autosomal recessive disease where in there are auto antibodies against the neuromuscular junction causing muscle weakness. Mainly it can affect voluntary muscles like limbs, eyes, throat. Treatment aspect wise, there is no cure for it. Anticholinesterase drugs like prostigmine czn be given. Immunoglobulin, steroids are main line of treatment. All are prescription medicines, so do consult you doctor and take medicines. According to me I dont think it is advisable for you to under go second hip replacement surgery. Recovery will be very difficult . Hope my answers have helped you.