State of the art in computer-assisted orthopaedic THR and TKR

Computer assisted orthopaedic surgery (CAOS) was developed to improve the accuracy of surgical procedures, and it has dramatically improved in the last years from an experimental laboratory procedure to a routine procedure theoretically available for every orthopaedic surgeon. Besides robotic application, surgical navigation has been widely developed for joint arthroplasties, mostly for total knee replacement (TKR) and total hip replacement (THR). The ! rst navigated joint replacement (a TKR) was performed in January 1997 by Saragaglia et al (1), using a non-image based system with intra-operative kinematic and anatomic analysis of the knee joint. Following these pioneers, other systems have been developed and validated. However, this appealing technology has not been adopted on a broad scale, and some surgeons complain of several relevant inconveniencies of using it on a routine basis. What have we already learnt, and what are the remaining questions?