Can butt implants cause nerve damage/possibly paralyze you?

If performed by a buttock implant specialist, buttock implant are no more dangerous than fat transfer or breast inplants:
Risks and potential complications of buttock implants are very similar to breast implants. One main difference is while breast implants have a nearly 20% risk of hardening from excessive scar tissue formation surrounding the implant (aka capsular contracture), in my experience buttock implants have ~2% risk of this. 

On the other hand , because at least 80+ % of the fat transferred will melt away within a year, most patients are not good candidates because they lack an adequate amount of fat to harvest. Another tip is that if you purposely gain weight (i.e. fat) for the procedure, the fat you lose first as you get back to your baseline weight is that very same fat that was transferred into your buttock...so don't fall victim to this recommendation. Even those patients that had adequate amounts of fat pre-operatively, still end up seeking buttock implants after a year or so because most of the fat transferred melted away leaving them with minimal result.

 Although overall using your own fat is relatively safe, it not infrequently melts away unevenly leaving one butt cheek bigger than the other or with dimpling or hard fat cysts.  The one serious complication that can rarely (< 1%) happen is "fat embolism" in which some of the fat gets into the blood stream and travels up into the lungs, heart, and/or brain causing serious problems. This complication is more likely to happen with the larger amount of fat being transferred. This is even more likely to happen when using fillers like liquid silicone, PMMA, Sculptra, and hyaluronic acids. Also fillers, when injected in large quantities, have a relatively high infection rate, guaranteed tendency to migrate away from the original area they were injected, and almost always stimulate a lot of inflammation with a subsequent and disastrous amount of scar tissue/hardening.
Thus buttock/hip implants become a very good, safe, and long term reliable option for most patients seeking buttock/hip augmentation (at least in my practice).

Hi and thanks for your question.  Yes, there is a theoretical risk to the sciatic nerve which is deep to where the implant would be placed.  However, the risk of this is very low and it is important that you have your surgery performed by a board certified plastic surgeon trained in the procedure. If your plastic surgeon mentions this possible complication it is good thing as it shows they are aware of the anatomy and are educating you regarding the risks.As the chance of this complication is very low, I am confident in recommending implants for the right patient that does not have enough fat for grafting.  

Sometimes in placing buttock implants, the implant can irritate the sciatic nerve and this can cause pain down one's leg. This is not very common with subfascial or intramuscular placement.