As Gilmore said, he has numbness in one of his arms. Last years procedure involved shaving the bone of two vertebrae to alleviate pressure it was putting on the nerve(s). So we know the general problem, discs and vertebrae involved and why it's causing a problem. No doubt this sounds like Peyton Manning's neck injury which also caused numbness or loss of touch dexterity. Ultimately Manning underwent three posterior cervical foraminotomy before ultimately going through a vertebrae spinal anterior fusion.
It's my bet Aaron Williams could have the same surgery and continue playing however because he is waiting till the offseason to make a decision he would likely miss 2017, like Manning missed 2011. At 28 years old in 2018 Williams could come back, or he could retire. I'd put retirement at a 75% likelihood.