Robotic-Assisted Knee Arthroplasty: An Overview
Unicompartmental knee arthroplasty and total knee arthroplasty are reliable treatment options for osteoarthritis. In order to improve survivorship rates, variables that are intraoperatively controlled by the orthopedic surgeon are being evaluated. These variables include lower leg alignment, soft tissue balance, joint line maintenance, and tibial and femoral component alignment, size, and fixation methods. Since tighter control of these factors is associated with improved outcomes of knee arthroplasty, several computer-assisted surgery systems have been developed.
These systems differ in the number and type of variables they control. Robotic-assisted systems control these aforementioned variables and, in addition, aim to improve the surgical precision of the procedure. Robotic-assisted systems are active, semi-active, or passive, depending on how independently the systems perform maneuvers.
Reviewing the robotic-assisted knee arthroplasty systems, it becomes clear that these systems can accurately and reliably control the aforementioned variables. Moreover, these systems are more accurate and reliable in controlling these variables when compared to the current gold standard of conventional manual surgery.
At present, few studies have assessed the survivorship and functional outcomes of robotic-assisted surgery, and no sufficiently powered studies were identified that compared survivorship or functional outcomes between robotic-assisted and conventional knee arthroplasty. Although preliminary outcomes of robotic-assisted surgery look promising, more studies are necessary to assess if the increased accuracy and reliability in controlling the surgical variables leads to better outcomes of robotic-assisted knee arthroplasty.
These studies have shown that robotic-assisted surgery is accurate in controlling surgical variables, such as mechanical lower leg alignment, maintaining joint-line, implant positioning, and soft tissue balancing. Furthermore, these studies have shown that controlling these variables is better than the current gold standard of manual knee arthroplasty. Until now, not many studies have assessed survivorship of robotic-assisted surgery. Furthermore, no studies have, to our knowledge, compared survivorship of robotic-assisted with conventional knee replacement surgery. Finally, studies comparing functional outcomes following robotic-assisted surgery and conventional knee arthroplasty surgery are frequently underpowered due to their small sample sizes.68,70 Since many studies have shown that the surgical variables are more tightly controlled using robotic-assisted surgery when compared to conventional surgery, large comparative studies are necessary to assess the role of robotic-assisted surgery in functional outcomes and survivorship of UKA and TKA.
Cost-Effectiveness of Robotic-Assisted Surgery
High initial capital costs of robotic-assisted surgery is one of the factors that constitute a barrier to the widespread implementation of this technique. Multiple authors have suggested that improved implant survivorship afforded by robotic-assisted surgery may justify the expenditure from both societal and provider perspective.84-86 Two studies have performed a cost-effectiveness analysis for UKA surgery. Swank and colleagues84 reviewed the hospital expenditures and profits associated with robot-assisted knee arthroplasty, citing upfront costs of approximately $800,000. The authors estimated a mean per-case contribution profit of $5790 for robotic-assisted UKA, assuming an inpatient-to-outpatient ratio of 1 to 3. Based on this data, Swank and colleagues84 proposed that the capital costs of robotic-assisted UKA may be recovered in as little as 2 years when in the first 3 consecutive years 50, 70, and 90 cases were performed using robotic-assisted UKA. Moschetti and colleagues85 recently published the first formal cost-effectiveness analysis of robotic-assisted compared to manual UKA. The authors used an annual revision risk of 0.55% for the first 2 years following robot-assisted UKA, based on the aforementioned presented data by Coon and colleagues.81 They based their data on the Mako system and assumed an initial capital expenditure of $934,728 with annual servicing costs of 10% (discounted annually) for 4 years thereafter, resulting in a total cost of the robotic system of $1.362 million. These costs were divided by the number of patients estimated to undergo robotic-assisted UKA per year, which was varied to estimate the effect of case volume on cost-effectiveness. The authors reported that robotic-assisted UKA was associated with higher lifetime costs and net utilities compared to manual UKA, at an incremental cost-effectiveness ratio of $47,180 per quality-adjusted life year (QALY) in a high-volume center. This falls well within the societal willingness-to-pay threshold of $100,000/QALY. Sensitivity analysis showed that robotic-assisted UKA is cost-effective under the following conditions: (1) centers performing at least 94 cases annually, (2) in patients younger than age 67 years, and (3) 2-year revision rate does not exceed 1.2%. While the results of this initial analysis are promising, follow-up cost-effectiveness analysis studies will be required as long-term survivorship data become available.
Conclusion
Tighter control of intraoperative surgical variables, such as lower leg alignment, soft tissue balance, joint-line maintenance, and component alignment and positioning, have been associated with improved survivorship and functional outcomes. Upon reviewing the available literature on robotic-assisted surgery, it becomes clear that this technique can improve the accuracy of these surgical variables and is superior to conventional manual UKA and TKA. Although larger and comparative survivorship studies are necessary to compare robotic-assisted knee arthroplasty to conventional techniques, the early results and cost-effectiveness analysis seem promising.
