Robotic-assisted total knee arthroplasty: a game changer in alignment strategies

Although the ideal alignment philosophy in the settings of total knee arthroplasty (TKA) is still debatable today, the value of an accurately positioned implant in the clinical outcome of joint reconstruction is undeniable. Thus, it is not surprising that the use of robots in the operating room is rising worldwide [1]. Through the dynamic intraoperative assessment of joint gaps and ligaments, robotic-assisted surgery platforms enable the surgeon to execute accurate bony cuts while preserving the soft-tissue envelope [2, 3]. Despite the high costs associated with robotic-assisted TKA (raTKA) [3], this technique is gaining popularity among the surgeons, especially those aiming to restore the most "normal" knee kinematics in a patient [4]. In this article, Sebastien Lustig, Professor in the Arthritis and Joint Replacement Department of Lyon North University Hospital reviews the promises and limitations offered by raTKA for functional alignment.


Sébastien Lustig

Lyon North University Hospital
Lyon, France


Robotic-assisted total knee arthroplasty: the advent of semiactive and fully active systems

The term "robot" was initially coined in 1920 by the Czech science-fiction writer Karel Capek, who described artificially humanoids repeatedly performing labor tasks [2]. In the operating room, robots were initially designed to minimize human error while maximizing operative accuracy [3]. Since the first reported robotic-assisted total knee arthroplasty (raTKA) in the early 2000s [5], the surgical tasks performed by robotic-assisted surgery platforms have rapidly evolved. Currently, all robotic technologies use dynamic referencing to assess intraoperative knee stability, alignment, and range of motion (ROM) while adjusting bone resection, ligament balance, and position of the prothesis [2, 6]. Based on how bone resections are conducted, robotic-assisted surgery platforms can be either classified as "fully active" (ie, a robotic arm performs autonomously preprogrammed bone resections on the patient) or "semiactive" (ie, the surgeon performs bone resection within a predefined zone that has been set in the preoperative plan while receiving intraoperative feedback) [1, 3, 7]. Such systems normally include a haptic interface by which the surgeon receives information about the forces and stress exerted on articular surfaces and can adjust his/her movements intraoperatively. Preoperative computed tomography (CT) scans or magnetic resonance imaging (MRI) enables the surgeon to generate a virtual three-dimensional (3D) model of the patient-specific bony anatomy. The 3D virtual model is employed to preplan bone cuts, implant size, as well as positioning, and is subsequently mapped intraoperatively to the patient's bone anatomy using navigational trackers, in a process known as registration [8, 9]. Another type of semiactive systems are handheld robotic burrs, which are manually controlled by the surgeon. Instead of a haptic interface, the robot follows the navigation field's burring tool trajectory, controlling the speed and exposure of the device to protect against iatrogenic ligament injuries [3, 10]. Contrary to haptic systems, this type of semiactive system is imageless (ie, it is not based on CT/MRI scans) and compatible with a wide range of prosthetic implants and brands [2, 10, 11]. Each robotic device is associated with several benefits and limitations (Table 1). While semiactive systems are the most frequently used today, the appearance of second-generation fully active systems might change the orthopedic landscape in the near future.


Although the ideal alignment philosophy in the settings of total knee arthroplasty (TKA) is still debatable today, the value of an accurately positioned implant in the clinical outcome of joint reconstruction is undeniable. Thus, it is not surprising that the use of robots in the operating room is rising worldwide [1]. Through the dynamic intraoperative assessment of joint gaps and ligaments, robotic-assisted surgery platforms enable the surgeon to execute accurate bony cuts while preserving the soft-tissue envelope [2, 3]. Despite the high costs associated with robotic-assisted TKA (raTKA) [3], this technique is gaining popularity among the surgeons, especially those aiming to restore the most "normal" knee kinematics in a patient [4]. In this article, Sebastien Lustig, Professor in the Arthritis and Joint Replacement Department of Lyon North University Hospital reviews the promises and limitations offered by raTKA for functional alignment.


Sébastien Lustig

Lyon North University Hospital
Lyon, France


Robotic-assisted total knee arthroplasty: the advent of semiactive and fully active systems

The term "robot" was initially coined in 1920 by the Czech science-fiction writer Karel Capek, who described artificially humanoids repeatedly performing labor tasks [2]. In the operating room, robots were initially designed to minimize human error while maximizing operative accuracy [3]. Since the first reported robotic-assisted total knee arthroplasty (raTKA) in the early 2000s [5], the surgical tasks performed by robotic-assisted surgery platforms have rapidly evolved. Currently, all robotic technologies use dynamic referencing to assess intraoperative knee stability, alignment, and range of motion (ROM) while adjusting bone resection, ligament balance, and position of the prothesis [2, 6]. Based on how bone resections are conducted, robotic-assisted surgery platforms can be either classified as "fully active" (ie, a robotic arm performs autonomously preprogrammed bone resections on the patient) or "semiactive" (ie, the surgeon performs bone resection within a predefined zone that has been set in the preoperative plan while receiving intraoperative feedback) [1, 3, 7]. Such systems normally include a haptic interface by which the surgeon receives information about the forces and stress exerted on articular surfaces and can adjust his/her movements intraoperatively. Preoperative computed tomography (CT) scans or magnetic resonance imaging (MRI) enables the surgeon to generate a virtual three-dimensional (3D) model of the patient-specific bony anatomy. The 3D virtual model is employed to preplan bone cuts, implant size, as well as positioning, and is subsequently mapped intraoperatively to the patient's bone anatomy using navigational trackers, in a process known as registration [8, 9]. Another type of semiactive systems are handheld robotic burrs, which are manually controlled by the surgeon. Instead of a haptic interface, the robot follows the navigation field's burring tool trajectory, controlling the speed and exposure of the device to protect against iatrogenic ligament injuries [3, 10]. Contrary to haptic systems, this type of semiactive system is imageless (ie, it is not based on CT/MRI scans) and compatible with a wide range of prosthetic implants and brands [2, 10, 11]. Each robotic device is associated with several benefits and limitations (Table 1). While semiactive systems are the most frequently used today, the appearance of second-generation fully active systems might change the orthopedic landscape in the near future.


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  • Clinical and functional outcomes of robotic-assisted TKA
  • Is raTKA a cost-effective technique?
  • Robotic-assisted TKA and functional alignment philosophy: an intertwined road
  • Personalized preoperative planning
  • Registration, ligament balancing, and bone resection
  • The promising clinical outcomes of functionally aligned total knee arthroplasty
  • Conclusions and future perspectives

Part 1 | Evolution of alignment concepts

Part 3 | The use of custom implants

Additional AO resources

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Contributing experts

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

Michel Bonnin

Centre Orthopédique Santy
Lyon, France

Sébastien Lustig

Lyon North University Hospital
Lyon, France

Charles Rivière

Clinique du Sport Bordeaux-Mérignac
Mérignac, France

This issue was written by Antia Rodriguez-Villalon and Laura Kehoe, AO Innovation Translation Center, Clinical Science, Switzerland.

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