When you say, 'Facet ablation', I think you're referring to the ablation of the nerves. Assuming that's what you meant, the neurosurgeon guides the fine needle into the nerve, using a technique called 'fluoroscopy'. This is a fairly accurate process, because he/she can actually see the nerves, so can position the needle correctly.

Although the technique usually produces good results, there will always be errors, as with any surgical process.

If you're worried about any after-effects you're experiencing, I'd suggest that you contact your doctor as soon as possible. Hopefully, this will eliminate any worries you may have and assuage your fears.