Judy is right about BMP... proteins that promote bone growth to increase fusion rates. Upside is increased fusion rates, downside is potential for too much bone growth. See the item I posted back in 2009... this is about a new fusion technique, but there was an unexpected finding regarding BMP.
Mimally invasive TLIF w/Hydrocision (interesting BMP data too)
Is this a repeat surgery? Pseudoarthrosis implies (to me and I'm not a doctor) that this is a fusion that did not fuse.
Welcome to the forum... whatever you ultimately decide on, good luck to you and your husband!
Mark