CONCEPT Femoral neck fracture and femoral head necrosis are surgical cases in which hemiarthroplasty is recommended as it seems inappropriate to replace an healthy acetabulum, that might result in subsequent bone loss and additional revision problems. Furthermore, compared to the total hip replacement, hemiarthroplasty procedures involve shorter surgical times and lower medical and prosthesis costs. The Medacta Endo Head is a product suitable to perform hemiarthroplasty on any hip joint whose acetabular conditions are satisfactory. The Endo Head is an unipolar prosthesis made of High Nitrogen stainless steel that consists of a monobloc prosthetic femoral head articulated directly with the patient's acetabulum. It is designed to be assembled with all the Medacta stems with 12/14 taper.