Computer-assisted orthopedic surgery

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Computer-assisted orthopedic surgery or computer-assisted orthopaedic surgery (sometimes abbreviated as CAOS[1]) is a discipline where computer technology is applied pre-, intra- and/or post-operatively to improve the outcome of orthopedic surgical procedures. CAOS is an active research discipline which brings together orthopedic practitioners with traditionally technical disciplines, such as engineering, computer science and robotics.

The principal idea behind CAOS is that operative outcomes will be improved through the use of computer technology. Taking the example of joint replacement, the task of the surgeon is to integrate the new joint components into the patient's existing anatomy; CAOS technologies allow the surgeon to:

  • Plan the component placement in advance, including determination of the appropriate component sizes;
  • Measure the intra-operative placement of the components in real time, making sure that the plan is adhered to;
  • Measure the post-operative result

It has not yet been proved that CAOS technologies result in a significant long-term improvement in operative outcome. Whilst the surgeon (or even medical students in laboratory studies[2]) can achieve better results in terms of planned vs. achieved placement of components, it is not clear whether the plan has been constructed optimally. Further, because of the functional adaptability of bone, errors in component placement may become unimportant in the long term. Because of the relatively short time period over which CAOS has developed, long-term follow-up studies have not yet been possible.

With CAOS, the surgeon can more accurately pinpoint anatomical landmarks that might be hard to see in a small incision. This navigation system then guides the surgeon through different bone cuts and finally to implantation. Computer-assisted orthopedic surgery is mostly used in knee implant surgery because of the precision the surgeon get with femoral and tibial bone cuts. It is also used to navigate acetabular components placement where correct cup inclination is crucial.[citation needed]

Computer-assisted orthopedic surgery is a system where a computer interacts with body parts via infrared lights and gate detectors. There are systems that require C-Arm images or CAT scans, flourabased systems and the newest and most evolved systems are imageless systems, this means that no pre scans of any kind are necessary. The imageless systems are far less complicated, are lower cost and more patient friendly since the pre scans are not necessary. The imageless systems will also bring down operation time. The negative aspect of imageless systems is that they might be less accurate, this is yet to be proven.[citation needed]


  1. ^ Nolte, L.P. and Beutler, T.: Basic Principles of CAOS, pages S.A6-S.A16, Int. J. Care Injured (2004) 35
  2. ^ Cobb, J.P. et al.: Navigation Reduces the Learning Curve in Resurfacing Total Hip Arthroplasty, page 90, Clinical Orthopaedics & Related Research (463)

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