2nd opinion

My 20 year old son has been advised he needs scoliosis reconstruction as he has a thoracic scoliosis from T2-T8.  He has been told he needs a 9 posterior spinal fusion, with aggressive release at the T4 level with possible partial vertebral column resection.  He was told this has significant risk to the spinal cord.  
My son also suffers from Marfans syndrome.
He has been advised that this surgery is necessary and there is no other option available to him. Can you advise the level of risk to the spinal cord there may be, and if I should get a second opinion as this is (in the surgeons own words) 'the most aggressive treatment, which is the best'?
Thanks for any light you can shed on this