How strong is the neck after a fracture and subsequent fusion?

I broke my neck between c3,4 and 7,8. The c7 and 8 fracture healed on it's own with the use of a rigid neck brace. The fracture at 3 and 4 required surgery and the use of cadavier bone.
Will my neck ever be able to safely handle the stress and impact of competing in Jiu Jitsu, again. I miss the sport, exercise and competition, but not enough to become a parapallegic.

I would be really careful about this. A naturally healed bone is stronger than before it was broken, but you had a fusion. The fusion changes the natural mechanics of the neck. I would seriously consult with the MD who performed the procedure. The fused levels might be OK but the level above and below tends to become more mobile, so these levels with the increased load of Jui-Jutsu may not handle the increased strain well. You sustained a very serious injury, I again would highly, highly recommend speaking with the MD, before returning to competition level Juio-Jitsu.

Not to be nit-picky either but if you damaged the spinal cord in the cervical region you would become a full or incomplete Quadriplegic- meaning - no arm, trunk or leg function.

bones heal back stronger than before after a fracture. it is the body's way of ensuring it won't happen again. as for the rigorous exercise, I would give it some time and exercise your neck slowly at first very gradually working yourself up to the pre-fracture state. trust me on this, I have broken several bones in my time and know how this all works. hope I have been some help to you