An extensive report of the World Health Organization (WHO) shows that 40% of people over the age of 70 years suffer from osteoarthritis of the lower extremity; 80% of patients with osteoarthritis has some degree of limitation of movement, and 25% cannot perform their major daily activities of life (Mathers et al., 2002). Due to the increasing number of hip and knee prostheses (over 1 million per type, worldwide) that are implanted, the number of complex revision surgeries is likely to double by 2015 (Kurtz et al., 2007). Hence, the burden of muscuslo-skeletal diseases and prosthetic revision operations is huge and is increasing rapidly with the aging population.

Unfortunately, for patients that require a major surgical intervention to their muscuslo-skeletal system, the functional outcome after surgery is often unsatisfying. The challenge is to create a tool that helps the surgeon reaching the optimal functional result for the patient.

Morevoer, the education of reconstructive surgeons is jeopardized by reduced hands-on cadaver training sessions in their curriculum and a limited surgical training time spent in the operating theatre. As a consequence, an increasing part of the learning experience is obtained on actual patients without extensive guidance from an experienced clinician, which puts patients at higher risks and compromises the quality of the health care system. The challenge is to generate a user friendly training facility for the surgeons that does not put any patients at risk and improves the know-how of the (future) surgeons.

Musculo-skeletal models that have been developed and are currently on the market are not easily accessible for surgeons because they are not user-friendly and do not present the data in a ‘clinically relevant’ way. Hence, these models have the status of a research tool, but are not used by surgeons in their daily practice. To facilitate the use of these models, a more surgeon oriented approach is therefore required.

The musculo-skeletal models that do exist are (although state-of-the-art) still quite simplistic in the sense that they do not account for compensation mechanisms that patients typically use. A model that incorporates these more realistic adaptive changes is therefore required. A surgeon-friendly musculo-skeletal model will provide additional features that cadaver specimens do not offer. The musculo-skeletal model can simulate the in-vivo functionality of the altered system and provide vital feedback that enables the surgeon to make decisions concerning implantation parameters such as the influence of muscle insertion points or the significance of adjustable prosthesis dimensions.