**1. Introduction**

Total hip replacement is one of the most widespread and invasive orthopedic procedures worldwide [1]. In 2007, in the United States, 300,000 surgeries were performed. In the same year, from 50 up to 250 replacements for 100,000 people were carried out in Europe [2]. Total hip replacement has been performed since the 1970s, and upon an appropriate selection of patients, it significantly improves the quality of life by relieving the pain and functional disability experienced by patients with moderate-to-severe arthritis of the hip [2]. Moreover, it is a highly cost-effective procedure [3]. The main indication for surgical treatment remains osteoarthritis, which is particularly disabling among the elderly and obese patients who represent the most prevalent candidates. The other most common indications are:


Notably, apart from fractures, surgery is, however, recommended only in the event that one of the mentioned pathologies is present in association with severe pain or stiffness that limits daily activities, such as walking, getting up or sitting down, and dressing. Hip prostheses have been performed successfully at all ages, from the young adolescent with juvenile arthritis to the elderly patient with degenerative osteoarthritis [4]. Most of the patients undergoing total hip replacement are between the ages of 50 and 80. However, there is no absolute age or weight limitation for the prosthetic surgery of the hip. The duration of the implants should also be considered; although it has been estimated that roughly 58% of hip replacements will last 25 years [5], their lifespan may markedly vary depending on several factors, being obesity the major cause of a minor longevity of the prosthesis. The indication for surgery is given on the basis of the pain reported by the patient as well as in relation to the degree of disability.
