What is the cause and cure for the indentations on my front upper thighs? (Photo)

It is difficult to tell, but the indentations could be the point at which the liposuction ended. Without examining you it is difficult to tell. Too much may have been taken out at the transition between skin that had liposuction and skin that did not. A ms combination of fat grafting and liposuction above the indentation could help. I have been using a technique called SAFElipo for these type of revisions and the results have been good. The technique redistributes fat to smooth irregularities such as these. 

I I cannot tell from the photographs whether revision liposuction or fat grafting would solve the problem. It does not look like a surplus skin issue.

It is hard to tell if this is from the procedure you had or something else.  Sometimes compression sorts or sitting with pressure can cause this.  I suggest a formal consultation, there are surgical and nonsurgical options for improving this.  I have seen great success with Velashape treatments, but even laser or contouring liposuction can treat this and give you an excellent size/contour improvement.  Best, Dr. Emer.