The attached file is a replacment part for the body to leg joint. I made the file on TinkerCAD and printed in PLA with a Monoprice select mini V2. The inner joint will require some sanding to fit but you want it very snug to hold a pose. There is alot of work to take apart a NECA TMNT model. I sugest the use of a heat gun. There is a video that i found on youtube that i found helpful for the disasembly process.