# Mid-Flexion Instability in Total Knee Arthroplasty: Insights from Robotic-Assisted Surgery
## 6 Evolution of TKA Surgery and Principles of Robotic TKA  
TKA implants and instrumentations have evolved [2; 34]. Recent implant innovations include ultra-congruent prosthesis designs [35], and knee prosthetic surgery instrumentation evolved from elementary tools in the early 1970s to navigation systems and rTKA [2; 34; 36].  
[PERSON] et al. deeply analyzed the computer navigation systems and reported that they had not achieved the success they merited [34]. Conventional TKA is based on manually positioned jigs according to radiographs and intraoperative anatomical landmarks; on the contrary, rTKA utilizes computer software to convert anatomical information into a virtual patient-specific 3D reconstruction of the knee joint [2; 36; 37].  
This advancement enables the customization of knee prosthesis alignment to replicate individual anatomy [2; 36; 37]. Robotic surgery exhibits significant potential in enhancing component placement precision, reducing complication rates, and ensuring better soft tissue preservation, offering real-time feedback regarding bone cut thickness or orientation [2; 6; 7; 8; 36; 37].  
Robotic-assisted surgeries provide several options for the surgeon, with robotic arms classified as fully active, passive, and semi-active [2; 36]. As reported by [PERSON] et al., the three most commonly used robotic systems for knee arthroplasty are all semi-active [2]. They allow the surgeon to control bone resection and acquire live intraoperative feedback about any variation from the surgical plan [2]. On the contrary, active robotic systems function autonomously and complete the resections based on the surgeon's planning, while passive systems are continuously controlled by surgeons [2]. Another important aspect involves \"closed\" or \"open\" platform systems, meaning the possibility to use only one specific implant or various implant designs [2].  
Despite the initial economic cost and the increased operative time during the learning curve, studies demonstrate that the precision and high accuracy obtained with rTKA may improve patient-reported outcomes (PROMs) and long-term survivorship [2; 6; 7; 8; 13; 36; 37]. [PERSON] et al. analyzed that rTKA reduced postoperative pain and improved early functional rehabilitation compared to conventional jigs-based TKA [36]. [PERSON] et al. reported that robotic surgery improves patient satisfaction, with most patients suggesting rTKA to others [14].  
However, the two techniques had no differences in medium-to-long-term functional outcomes [2; 14; 36].  
The literature emphasized that, while recognizing the potential benefits of rTKA, it has yet to acquire endorsement among orthopedic surgeons [2]. Obstacles are associated with conflicts of interest, problems in intraoperative registration, increased radiation exposure, a long intraoperative time during the learning curve, and the cost of robotics [2]. However, as reported by [PERSON] et al., robotics has been introduced in sports medicine for anterior cruciate ligament reconstruction and osteochondral lesions, representing a turning point for future knee surgery [2].