Robotics-assisted knee arthroplasty is gaining increasing importance, as knee osteoarthritis represents a major public health issue in Germany. According to current data, more than 7% of the adult population is affected by knee osteoarthritis—equating to several million people who suffer from pain, limited mobility, and a significant loss of quality of life. As the condition usually progresses over time, many patients eventually require joint replacement surgery. Modern robotics-assisted procedures enable particularly precise, individually tailored implantation and help improve both the function and longevity of knee prostheses. The editorial team of the Leading Medicine Guide spoke with Stylianos Toumasis from Nardini Hospital in Landstuhl about this topic.
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Robotics-assisted knee arthroplasty represents one of the most advanced developments in orthopedic surgery and elevates implantation precision to a new level. While conventional methods rely heavily on the surgeon’s experience, anatomical estimates, and mechanical guides, robotics enables highly individualized, data-driven planning. At the beginning of the procedure, the patient’s knee is digitally measured, creating a precise 3D model that reflects the actual anatomy in real time. Based on this data, the system generates a personalized surgical plan defining the optimal size, position, and alignment of the prosthesis. The surgeon can adjust and refine this plan before robotics-assisted cutting guidance ensures millimeter-level precision.
“We have been using robotics-assisted knee arthroplasty for two years now, having previously worked with navigation-assisted technology. During these two years, more than 500 implantations have been performed—including primary knee replacements, partial knee prostheses, and revision surgeries. We are convinced that this technology offers clear advantages that directly benefit patients. With the help of robotics, prostheses can be implanted far more accurately and precisely. When a prosthesis is positioned exactly, its durability increases and postoperative pain is generally reduced. As a result, patients only need to stay in the hospital for a short time and can return home sooner. Another key advantage is the ability to create a personalized surgical plan. The prosthesis is tailored to the individual anatomy and specific characteristics of each patient rather than being implanted according to rigid standards. Robotics supports the precise implementation of this individualization, ultimately leading to the best possible outcomes“, explains Stylianos Toumasis at the beginning of our conversation.
Individual anatomical measurement using a robotics-assisted system fundamentally changes the planning and execution of knee replacement surgery, as it provides a precise, patient-specific real-time representation of the knee joint for the first time.
While many decisions in conventional procedures are based on experience, anatomical averages, or mechanical alignment, digital measurement enables an exact analysis of the actual joint geometry, ligament tension, leg axis, and cartilage condition.
“In robotics-assisted knee arthroplasty, anatomical measurement is performed directly during surgery. With the so-called CORI system, a robotic technology by Smith & Nephew, no preoperative CT scan is required. Instead, a virtual three-dimensional model of the knee joint is created during the procedure itself. The surface of the knee is captured point by point using special sensors and markers. This provides the surgeon with an exact representation of the individual anatomy during the operation—including all angles and specific joint characteristics. The major advantage is that everything happens live. These are not data collected months earlier, but an up-to-date, immediate depiction of the knee in exactly the condition being operated on. Within minutes, a complete 3D model is available, supplemented by information about the ligament status of the joint. Ligaments play a central role. Their tension and interaction cannot be reliably assessed using CT or MRI—this can only be done directly by the surgeon at the open joint. For a successful knee prosthesis, this so-called ligament balancing is crucial: the collateral ligaments must be stable, and depending on the type of prosthesis, the posterior cruciate ligament may also be required. This is where the surgeon’s experience comes into play, as they assess ligament tension and incorporate this information into the robotics-assisted planning. Robotics then helps position the prosthesis so that it fits optimally with the patient’s individual anatomy and ligament guidance“, explains Mr. Toumasis.
Robotics-assisted knee arthroplasty is particularly suitable for patients for whom precise, individually tailored implantation is critical to functional outcomes. Patients with complex anatomical conditions benefit especially, such as pronounced axis deviations like knock knees or bowlegs, severe cartilage damage, or pre-existing deformities resulting from prior injuries.
Younger, more active patients who place high demands on mobility, stability, and prosthesis longevity also benefit significantly from robotics, as precise alignment improves implant durability. Patients with existing partial or total knee replacements who require revision surgery also benefit, since robotics greatly facilitates planning and execution in these demanding situations.
Stylianos Toumasis comments on this: “At our clinic, we perform virtually all primary knee replacements and partial knee prostheses using robotics—even many revision surgeries. Only in very rare cases involving extremely complex bone defects does robotics reach its limits. Otherwise, we consistently use the advantages of this technology because it enables particularly precise implantation. The benefits are especially evident when it comes to complications. One major issue in recent years has been pain and dissatisfaction following knee replacement surgery. Studies show that about one in five patients is not fully satisfied after the operation. The reasons are varied—the kneecap, ligament tension, small deviations in alignment. With robotics, we can better control many of these factors by tailoring the prosthesis much more precisely to the individual anatomy. We respect the natural shape of the knee and implant the prosthesis in a way that best matches this anatomy. Another important factor is the risk of loosening. When a prosthesis is positioned precisely, the risk of loosening is significantly reduced. Long-term results over 20 years are not yet available, as robotics has only been widely used for five to six years. However, it is well established that the more precisely a prosthesis is implanted, the longer it lasts. Studies also show that patients mobilize faster and more effectively after a precisely implanted prosthesis. Overall outcomes are better because the joint functions more harmoniously from the outset, with fewer irritations or misloads“.
Robotics-assisted knee surgery significantly reduces the risk of complications such as malalignment, loosening, or restricted mobility primarily because it enables an unprecedented level of precision in both surgical planning and execution.
Partial knee prostheses (unicompartmental replacements) and revision prostheses are among the most demanding procedures in knee arthroplasty, as they require particularly precise planning and a high level of surgical expertise. While the challenges differ, they share one common factor: the anatomy is more complex, less predictable, and requires an individualized strategy.
“Partial knee prostheses use different implants than total knee replacements and are only suitable for patients whose osteoarthritis is truly limited to a single compartment of the joint. In addition, the collateral and cruciate ligaments must be intact. With robotics, these procedures can be performed very precisely, leading to excellent results. In the field of revision surgery—where an old prosthesis must be removed and replaced with a new one—robotics is also becoming increasingly important. The software is now being used for such revision procedures as well. However, these operations are more complex and require extensive experience, as revision surgeries are generally less common and the anatomy is often significantly altered after removal of a loosened or infected prosthesis. This presents additional challenges for robotics. Therefore, while robotics is used in revision surgeries, it is not suitable for all patients. In cases of major bone defects, the technology reaches its limits. Regarding the learning curve, despite all the technical support, a great deal of experience is still required. Surgeons who have previously worked with navigation-assisted systems adapt more quickly, but robotics also requires training, dry runs, continuing education, and a deep understanding of the system. Despite all the technology, one thing remains clear: robotics does not replace the surgeon. It does not perform any steps independently. The surgeon decides which plan is created, what adjustments are necessary, and how the prosthesis is ultimately implanted. Responsibility always lies with the surgeon“, emphasizes Stylianos Toumasis.
Robotics can significantly increase the precision of knee replacement surgery, but the surgeon’s experience remains a central determinant of the outcome. Robotic systems provide data, measure ligament tension, display alignment axes, and prevent technical deviations—but they do not replace surgical judgment.
Robotics-assisted knee arthroplasty has a noticeably positive impact on both early rehabilitation and long-term patient satisfaction, as it makes surgery more precise, less invasive, and better aligned biomechanically.
“After surgery—whether total replacement, partial replacement, or revision—the rehabilitation process with robotics is even faster than before, as patients experience less pain, which is also related to the minimally invasive technique. While hospital stays previously often lasted two weeks, they are now usually under one week. In our joint replacement center, we perform around 250 knee surgeries per year—total replacements, partial replacements, and revision surgeries. Almost all are carried out using the robotic system. Two lead surgeons perform these procedures, as such operations require extensive experience and a high level of routine. Therefore, the majority of cases are concentrated among experienced surgeons. Robotics-assisted partial knee replacement is now standard practice in many hospitals. In contrast, robotics-assisted use in revision surgeries is still relatively rare. However, we also apply the technology where it is meaningful and feasible“, says Stylianos Toumasis, adding at the end of our conversation:
“At Nardini Hospital, we operate as a maximum-care joint replacement center with the highest quality standards—covering knee and hip arthroplasty as well as shoulder arthroplasty. The patient is always at the center of our work. Our goal is to achieve the best possible outcomes using modern technologies and minimally invasive methods. Many hospitals in Germany are now showing interest in this technology and are seeking to implement robotics-assisted procedures as well. In orthopedics, there is a growing recognition that robotics—when applied correctly—leads to more satisfied patients. Through training programs and professional exchange with colleagues, the use of robotics continues to expand in order to achieve even better long-term results“.
Thank you very much, Mr. Toumasis, for the insightful explanation of the topic of “robotics-assisted knee arthroplasty”!
- Chief Physician of Orthopedics and Trauma Surgery & Director of EPZmax, Nardini Hospital Landstuhl; Board-Certified Specialist in Orthopedics and Trauma Surgery with specializations in advanced orthopedic surgery, sports medicine, manual medicine, physical therapy; Master of Science in Health Care Management
- Areas of expertise: Hip arthroplasty (minimally invasive: AMIS/ALMIS), hip revision surgery, knee arthroplasty (partial/total), robotics-assisted (CORI), knee revision surgery, shoulder arthroplasty, arthroscopy, sports traumatology, trauma surgery, foot and hand surgery
- 15 years of experience in computer-assisted and robotics-assisted surgery
- High surgical volumes: >550 hip and ~250 knee replacements per year
- EndoCert-certified maximum-care center
