Computer-assisted surgery: Evolution and basic concepts

As the field of robotics evolves, so too does our willingness to welcome technology into traditionally human-dominated realms. Computer-assisted surgery (CAS) is available for the modern operating room and is constantly being refined to enhance functionality, precision, and cost-effectiveness. Part 1 chronicles some of the evolution of CAS, looking at terminology and basic concepts.

Through the ages, humans have been fascinated with the idea of automated devices that serve our needs. Consider Hephaestus’ mechanical servants in Greek mythology [1]. We have been entranced by the potential of machines for millennia [2,3]. Now, our capabilities are catching up to our imaginings: take a look at robotics lab Boston Dynamics’ newest commercial robot, Spot® [4].

Advancements in technology, combined with interdisciplinary team collaboration, is propelling the integration of innovations in materials, computing, and medicine to bring a technological revolution to the operating room (OR) across all surgical disciplines.


What is computer-assisted surgery?

Computer-assisted surgery (CAS) is a umbrella term that encompasses different kinds of technologies that are used to [1]: perform surgical procedures, in part or in their entirety [2]; guide or navigate during surgery [3]; plan surgeries [4]; train less experienced surgeons [5]; and create patient-specific instruments (PSI) [5–7]. It is sometimes referred to as computer-aided surgery, computer-assisted intervention, surgical robots, image-guided surgery, or surgical navigation, depending on what the technology does [5, 7, 8].

CAS helps orthopedic surgeons perform surgery with increased precision and reproducibility, which is believed to have a positive impact on clinical and functional outcomes. There are two categories of CAS: robotic-assisted surgery, where a motor moves the technology, and general CAS (usually navigation systems), where the surgeon physically moves the technology [9].


Justin Chang

University College London Hospital
London, United Kingdom

Ahmed Magan, Trauma and Orthopedic Surgeon with University College London Hospital NHS Foundation Trust, UK, notes that robotic surgery in particular “has revolutionized surgical practice—from planning through to the execution of the operation. It is easy to learn and the results are reproducible.”


It all started with the brain

The pioneering work of CAS was in the field of neurosurgery in the early 1900s. Two British academics working at University College London Hospital, Sir Victory Horsley (professor of neurosurgery and a neuroscientist) and British physiologist, Robert Clarke, collaborated on the development of a stereotactic apparatus for locating lesions in the brain in 1908.

It essentially involved attaching the cranium to the “Horsley-Clarke Apparatus” and inserting a probe into an area of interest with some degree of accuracy. Their work was based on three-dimensional (3D) Cartesian geometry of a monkey brain [10]. It is no wonder that their invention lacked precision and required further work.


Applications of CAS

Over time, CAS systems have been developed for use in a wide range of surgical disciplines. An indicator of the growth of the field is that in 1999, only 14 articles indexed in PubMed included “computer-assisted surgery” or “robotic surgery” in their titles or abstracts, while by 2019, 1,027 articles were published.

Neurosurgery was the first field to employ CAS [8, 11, 12], and the technology has expanded to support myriad surgical interventions. Here are a few examples:

  • Total hip arthroplasty (THA): Robotic THA was found to improve acetabular implant positioning and reduce dislocations compared to manual THA [13, 14].
  • Partial and total knee arthroplasty (TKA): Using navigation in TKA was associated with higher clinical accuracy in implant placement [15] and robot-assisted TKAs also improved implant positioning [16].
  • Osteotomies: Using 3D-planned patient-specific instrumentation (PSI) and navigation in high tibial open wedge valgus-producing osteotomies resulted in accurately corrected mechanical leg axis [17].
  • Tumors: Minimally invasive robotic hepatectomy for liver tumors has been shown to be “safe and feasible” [18]. Intraoperative computer-assisted navigation and 3D PSI printing facilitated a successful surgical resection of metastatic acetabular osteosarcoma, ultimately preserving the patient’s hip stability and providing better quality of life for two palliative years [19].
  • Neurosurgery: Robot-assisted drainage of thalamic hemorrhages improved patients’ prognoses and was associated with reduced cases of pneumonia and renal dysfunction [20].
  • Spine surgery: A study of 18 patients that received navigation-assisted surgery for a primary spine tumor indicated that it was beneficial in the resection of tumors due to more accurate screw placement and fewer complications [21].
  • Dental implants: Compared with a novice freehand implant placement group, novices using navigation were able to achieve implant placement in mandible models with an accuracy similar to that of experienced professionals [22].

In relation to orthopedics, Ahmed Magan highlights that, “In terms of contributions, computer-assisted surgery has been a real game-changer in partial and TKA. With this procedure, the outcome is related to the alignment, balance, and soft tissue preservation and there is technology available to help surgeons achieve these factors in more reliable, repeatable ways.

“However, there are barriers to this technology being widely adopted and available in all ORs such as, added operative time, being limited to implants specific to the system, resistance to new technology training for theater staff and cost implications.”

[See Part 2 of this article series for more in-depth discussion of CAS in modern orthopedics and associated benefits and risks.]


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  • Classification of CAS systems
  • Navigation
  • Image-based navigation
  • Imageless navigation
  • Patient-specific instrumentation (PSI)
  • Optimized positioning systemTM
  • Virtual and augmented reality
  • Artificial intelligence
  • Open vs closed CAS robotic systems
  • Path of development
  • Robotics in surgery
  • Early surgical robots
  • Conclusion
  • References

Part 2 | Current use in hips and knees

Part 3 | Looking to the future

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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

Justin Chang

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