Allow me to answer your question as best i can based upon your photos. However, please keep in mind that an in-person, or at least a virtual, consultation with physical exam is first necessary before any legitimate evaluation or final surgical recommendations can be made. It is not clear whether you have had any enhancement surgery to your buttock or not (? BBL). Either way, can tell you that no surgical procedure can guarantee lengthening the buttock “crack”. That being said, and after nearly 23 years of specializing in cosmetic plastic surgery of the buttock, buttock implants are the only option I have found to be reliable and permanent for adding length and/or depth to the buttock crack. When considering buttock implants make sure that the surgeon is going to be placing the implants within gluteus muscles , (a.k.a. “intramuscular pocket”), and that they are using anatomically correct, oval-shaped implants, such as Stanton Anatomic ®️ implants. Fillers, such as Sculptra and hyaluronic acids, for augmentation of the buttock/hips are a rip-off, period! Please keep in mind that an extremely few number of board-certified plastic surgeons specialize in these buttock implants so be sure to consult with one that is reputable and experienced. Unfortunately you may have to travel long and far away from home to find this particular surgeon. Glad to help.