Computer-assisted surgery: Current use in hips and knees

Part 2 examines the current use of computer-assisted systems in hip and knee surgery. Weighing the pros and cons, we look at benefits, economic considerations, limitations, concerns, and impact on patient outcomes. We also reveal how orthopedic surgeons are using these technologies in the operating rooms right now and how they perform after simulation training. 


Globally, the number of total hip (THA) and knee arthroplasties (TKA) performed each year is increasing [1–3]. They can be life changing procedures that, when successful, alleviate pain from conditions such as osteoarthritis, and return mobility to patients. Finding new ways to improve patient outcomes is of highest priority for healthcare systems and surgeons.


From CAS to CAOS

In Part 2 of this Insights Newsletter, we narrow our focus to computer-assisted orthopedic surgery (CAOS) systems currently used for hip and knee surgery. Part 1 introduced the different types of navigation and robotic systems used in CAS, their classification, applications, historical background, and terminology.

Orthopedic surgeons are seeing an increasing availability of CAOS systems to train them, support and guide preoperative planning, and even conduct procedures with a robotic “partner” [4]. A study that looked at the use of navigation and robot-assisted surgery in TKAs in the US between 2005 and 2014, found that by 2014, 7% of the country’s TKAs involved navigation or robots compared with 1.2% in 2005. Robots were more likely to be involved in TKAs performed in the Northeast of the country, while navigation was more likely to be used in the Western states [3]. The Australian National Joint Replacement Registry showed that in 2012, 22.8% of all primary TKAs in the country were performed using navigation—an increase from 2.4% in 2003 [5]. Similar trends have been identified in the number of computer-assisted total hip arthroplasties (THAs) [6].

Surgeon training

For most complicated procedures there is an acknowledged benefit to practice. Surgery combines a honed skill set of cognitive, communication, and manual abilities that require training and ongoing practice. For many years, surgical skills have been taught via the master-apprentice model [7] with sheer volume of exposure building competence [8]. However, with decreased working hours, and increasing hospital costs and jurisdictional restrictions, it can be challenging for trainee surgeons to accumulate hand-on experience [9]. A 2019 study found surgeon experience level to be a risk factor in primary TKA malalignment, with trainee surgeons and low-volume non-trainee surgeons performing similarly [10].


Justin Chang

University College London Hospital
London, United Kingdom

For Justin Chang, Senior Clinical Fellow, University College London Hospital, UK, using computer navigation and robotic software as learning tools, particularly for knees, “can help trainees understand principles of balancing a knee. It provides visual and objective measurements for something that is usually learned by subjective feel.”

In terms of robot-assisted surgery, “the learning curve is primarily getting familiar to the functionality and registration of the robot. Surgical outcomes are generally less affected early in the learning curve because the robot ensures components are aligned in the planned position,” says Justin Chang.

Orthopedics is considered high risk for malpractice claims [11, 12]. In France, orthopedic patients make 20% of malpractice claims [13]. Being able to train to a standardized level of competence before having access to patients is an attractive prospect. Training tools have been developed for surgeons that offer the opportunity to practice the skills needed to improve operative accuracy and potentially decrease complications, without having to touch a patient [14].


Virtual reality

CAOS training systems that employ virtual reality (VR), which is a completely simulated experience, offer highly interactive simulations without the need of supervision, with benefits offered to both trainee and practicing orthopedic surgeons [15]. Indeed, simulation training is something that residents have indicated they are interested in accessing [16].


Watch this video of the Wraith VR Surgical Simulator demonstrating a robot-assisted total knee surgical technique through a virtual reality (VR) interface. By Ghost Productions.

Studies into the effectiveness of VR simulation training in orthopedics have found that the simulation-trained orthopedic surgeons, particularly trainees, were more surgically accurate when conducting the procedure [8, 17, 18]. It also offers a way to assess basic competency before operating on a patient [19].



Efficacy of CAOS

Without adequate research it is not possible to evaluate the degree to which a technology or procedure is effective in meeting its goals. Despite growing adoption of CAOS systems, they are still not available to many surgeons around the world, particularly in less urban environments.

Justin Chang notes that this is due in part to “cost being an important factor which may limit the ability to use robotic surgery, and the operative time is usually longer as well.”

What evidence is there to support or refute the use of CAOS navigation and robot systems in hip and knee surgery? Let's examine some findings.

CAUTIONARY NOTE FROM JUSTIN CHANG: CAOS does not replace surgeon skill

“Technological assists are no replacement for understanding how to apply the fundamentals of orthopedic practice. Learning the basic principles and standard guides is very important. If the software fails or the array positions are knocked mid-procedure, conversion to standard instrumentation may be necessary. Surgeons must have the skills to quickly adapt in this type of situation.”

Read the full article with your AO login

  • CAOS in TKA
  • Navigation in TKA
  • A note on planning software for knees
  • Robot-assisted TKA
  • Navigation and robot-assisted unicompartimental knee arthroplasty
  • CAOS in THA
  • Navigation in THA
  • Navigated THA
  • Robot-assisted THA
  • Patient-specific instruments
  • PSI in TKA: Cutting jig inaccuracies
  • 3D printed PSI and high tibial osteotomy
  • CAOS economic considerations
  • Considerations before a CAOS purchase
  • CAOS systems for use in hips and knees
  • Conclusion
  • References

Part 1 | Evolution and basic concepts

Part 3 | Looking to the future

Additional AO resources on this topic

Access videos, tools, and other assets to learn more about this topic.

Contributing experts

This series of articles was created with the support of the following specialists (in alphabetical order):

Justin Chang

University College London Hospital
London, United Kingdom

Ahmed Magan

University College London Hospital
London, United Kingdom

Mark Roussot

University College London Hospital
London, United Kingdom


Georges Vles

University Hospitals Leuven
Leuven, Belgium

This issue was created by Word+Vision Media Productions, Switzerland



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