Child Has Spastic Diplegia. Can Semlarass Surgery Help?

Dear doctor, My son was diagnosed with spastic diplegia when he was one year old. now he is 5 years old and is able to walk with the help of two elbow crutches and flexible AFOs. Last year, he had undergone serial casting for three weeks which helped to reduce his spasticity very much. He also has a low muscle tone in his trunk. At present, we are in Europe. He has a wheelchair and special chair at home and school with abduction. He also wears a swash orthosis to avoid cross legging. We had taken an X ray of his hips and found that the hip dislocation is 20-25% on both legs.. We came to know about the surgical method called SEMLARASS developed by Dr. Deepak Sharan in India. Unfortunately, we couldn t consult any other doctors about this. What are the possibilities of betterment for my son if he undergoes this surgery?Is there any negative impacts for this? When the spasticity from the legs are removed through surgery, will it affect his sitting position, since he has a low tone in the trunk? I appreciate this group work to help common people to clarify their medical doubts. Thank you Prakrithi