Fit and Fill Stem

The concept of “fit-and-fill” is to obtain a strong and secure initial fixation by filling the femoral canal and fitting a large area with the inner surface of the cortical bone. The fit-and-fill stem usually refers to the straight-type stem, and is often referred to as a “dual taper stem” or “double-wedge stem” because it is tapered in the coronal and sagittal plane. It is also called the metaphyseal-filling stem because of the primary site for medullary filling. Titanium alloys are used as the base material, and titanium fiber mesh, bead porous, and calcium phosphate coatings such as hydroxyapatite, are sometimes added to the proximal surface finish for bone ingrowth (or ongrowth), all of which have reported good long-term results. Survival rates with endpoints of revision or loosening are extremely good; 95–100% have been reported at 10–20 years, including Dorr type C cases and younger cases. In cases of abnormal neck anteversion requiring stem anteversion adjustment, the straight fit-and-fill straight stem without options such as a changeable neck is not indicated. Dorr type C bones may not be a good indication because of concerns about intraoperative and postoperative fractures and bone atrophy due to stress shielding. The fit-and-fill stem was the most widely used stem for primary THA in Japan until the 2000s.