Bert Parcells January 3, 2017 THA Implants STEM: Cemented Bert Parcells January 3, 2017 THA Implants The cemented stem was the original THA system. Cement is polymethylmethacrylate. We discuss the cement technique, basic properties of PMMA, history of PMMA, collar vs. collarless design, and technique for antibiotic cement.