Are there procedures to “fill in” a thigh gap?

Great question. 
Yes, fat is incredibly versatile and can be transferred to any part of the body you wish to plump up, or fill in, like flat or hollow areas, including a thigh gap. 
Because fat transfer uses liposuction to transfer the fat, no incisions will be made. There will be no scarring. Fat is living tissue, so it will graft onto existing cells in your body. Most clients retain 50-70% of the fat from their fat grafting procedure. If a greater enhancement is wanted, subsequent fat transfer procedures can be performed until the desired result is achieved. Results are usually permanent, and the fat will respond to weight loss and gain, like the rest of the fat on your body. 
The best way to assess and give true advice would be an in-person exam.  Please see a board-certified plastic surgeon that specializes in aesthetic plastic surgery.

Best of luck!
   
Dr. Schwartz
Board Certified Plastic Surgeon
#RealSelf100Surgeon
#RealSelfCORESurgeon
 

This can be improved with fat transfer. Keep in mind, fat transfer technique is important for successful fat transfer. I recommend water-assisted fat harvesting which gives pure fat to transfer and combine with platelet rich plasma (PRP) to get the most viable and sustainable fat cells. I combine with Sculptra to improve final results. I recommend getting a formal evaluation with an expert. Best, Dr. Emer

Fat grafting can be used to fill out most any area a patient would like. The inner thigh should be easily resolved for you with a fat transfer to the area. Discuss with a plastic surgeon who does a lot of fat grafts. Good luck.