What Causes Numbness In Fingers In A Person Suffering With Spondylitis?

my husband age is 51 years and weigh is 72 and sponylytis from last 3 years, has a problem of sponylytis .he has pain in neck and right hand from last 4 months and numness in 3 fingers.one orthopedic doctor said after seeing MRI report that there would be replacement of disc.this is 4 th level and the disc are giving the compression on the spinal nerve.Is there no any treatment instead of operation?please guide me.