Total hip arthroplasty and bone fragility.

The number of elderly people is steadily increasing: in the United States it will increase from 12.9\% to 20\% in 2030 with respect to the total population. Italy, with UK, Denmark and Sweden are the countries with the largest number of octogenarians (about 4\% of the population) and it is estimated that this rate will increase by 300\% over the next 50 years. The number of people affected by osteoarthritis will increase significantly and therefore the number of total hip arthroplasties will progressively increase. The success of an implant depends firstly by a flawless surgical technique, a correct and stable implant fixation and an optimal preoperative planning that should consider the bone quality of the patient, in order to choose a proper implant design. Different approaches could be followed to achieve adequate fixation: northern Europe surgeons prefer the cemented implant, instead American orthopedics generally use systems that allow a direct biological osteointegration. Elderly patients often present with multiple local and general problems that could affect significantly the normal course of a prosthetic surgery procedure and its results: they have bone tissue changes that lead to increased bone fragility and, consequently, difficulties to obtain primary stability. Osteoporotic bone is characterized by reduction of bone mass, decrease of cancellous bone trabeculae and by increased porosity of cortical bone. The bone fragility implies a greater risk of iatrogenic intraoperative fractures. Furthermore, difficulties linked to bone stock deficiencies become even more significant in revision surgery, where cortical bone thinning is associated with enlargement of the isthmus thus making more difficult to obtain distal fixation of prosthetic stems. At the moment, the role played by the drugs used for the treatment of osteoporosis during implant osteointegration is still not clearly understood and is still under investigation