There are about 370 million people living in Europe. Information on demographic data of osteonecrosis is unknown for the rest of Europe. There is no centralized health service in Europe to collect and report these data on osteonecrosis. Some countries in Europe have more precise data but only data on their own country.

There are approximately 295 million people living in the United States. Demographics of osteonecrosis in the United States are not collected with very much precision and not kept up to date. There is published information that would indicate that there is an estimate of approximately 20,000 new cases of osteonecrosis of the hip in the United States every year [6]. The accumulated numbers of ON is between 0.3 million and 0.6 million people. However, that information is based upon several large series of total hip replacements in which 10 % of the patients had a total hip replacement because of osteonecrosis. Not taken into account are all the new cases of osteonecrosis which do not have a hip replacement. This could probably add another 5 or 10 % to the mix. The estimate is calculated at approximately 22,000 new cases of osteonecrosis of the hip in the United States every year [6]. These numbers are indeed very “soft” numbers.