A few years ago when I wanted to add size/strength to my thighs in a big way I followed the following routine:
20,15,12,10,8,6,4,2 rep range on my squats with each set at least approaching failure and sometimes hitting failure (or at least as close as one could come on a movement like squats)
I did that for about 8 months and achieved noticeable size and strength gains. Also, last summer I trained with a buddy of mine and at the end of all of our squatting sessions we would drop the weight way down and load the bar with 225 and do what we liked to call "sets of death"...Pretty simple, just do as many as you can physically tolerate. Shaking, Vision loss, full body numbness all were expected and welcomed by the end of those sets. My best was 31...
Give it a try...you'll hate me for it
That didn't really answer your question, but if you're looking for size in your thighs this might do the trick.