Joint replacement surgery has evolved over the last 30 years to become one of the most common and predictable procedures in an Orthopaedic surgeons repertoire. Nonetheless, problems with malalignment, loosening, longevity and survivability still arise. Implant survival is multifactorial but proper alignment and orientation of the prosthetic components is an important issue. This is even more important when there is severe deformity or bone loss. The use of computer aided surgery enables surgeons to plan their surgery and optimise placement of implants.