What role should technology play in modern TKA above and beyond conventional instrumentation?

Neeraj Adkar
Traditional Total Knee Arthroplasty approaches have resulted in consistently high performance, but some patients may remain dissatisfied after their surgery. Traditionally it has been performed with 3 central reconstructive goals:

(1) Restoring appropriate knee alignment, referencing off a neutral mechanical axis;
(2) Creating a balanced soft tissue envelope with symmetry as the knee moves through the flexion-extension arc; and
(3) Maintaining or restoring normal patellofemoral kinematic relationships

In the past few decades several innovative techniques involving technology have been developed to improve the accuracy and precision of total knee arthroplasty surgery, with anticipated benefits over traditional TKA Techniques, some of the important once are as follows,

a. Computer assisted navigation
b. patient-specific instrumentation, and
c. robotic-assisted total knee arthroplasty

The success of a total or unicompartmental knee replacement depends primarily on restoring the mechanical axis of the lower limb.Traditionally, this is performed using intra- or extra-medullary alignment rods to help centralize and align the components along a universally agreed and anatomically derived mechanical line from the centre of the femoral head to the middle of the ankle. This can often lead to inaccurate placement, patient dissatisfaction and early failure. However this one-for-all model may not be the best approach. In the twenty-first century, with younger and more active patients, modern technology is paving the way for more individual, accurate, reproducible and anatomically tailored methods of performing knee arthroplasty.

Most studies have reported that computer assisted navigation reduced the outliers of alignment and component malpositioning. However, additional sophisticated studies are necessary to determine if the improvement of alignment will improve long-term clinical results and increase the survival rate of the implant.

The potential for robotic surgery to improve the accuracy and precision of TKA was introduced in reports describing the early results of CAS navigation. Hansen et al reported no significant differences in unicompartmental arthroplasty component position, fixation, or clinical outcomes. There appear to have been substantive improvements in robotic-assisted TKA. The first generation of robotic-assisted surgery was associated with improved component alignment, but a higher rate of surgical complications than conventional TKA. Other studies have reported improved component alignment, ability to restore flexion-extension gap relationships, and reduction in notch avoidance among robotic-assisted TKA. However, these

benefits have generally been achieved with substantially increased operative time. As experience with these technologies improves, a decline in operative time would be expected.

Computer-assisted and robotic-assisted surgery techniques generally achieve a high level of precision and accuracy, but have not uniformly provided improved patient-reported outcome scores or reduced TKA revision risk. The advantages of computer assisted navigation are increasing the accuracy of bony resection and decreasing the chance of malposition of the implants. The surgeon can estimate the level of femoral and tibial joint line intraoperatively. This also helps soft tissue balancing and can quantify the size of the gap and the stability. Most surgeons are impressed by the navigation since they can see that the component position initially determined by the conventional technique is frequently inaccurate. In addition, navigation can be used in teaching laboratories and operating rooms as training tools for less experienced surgeons and can serve as a valuable research tool. But it has certain disadvantages. Computer assisted navigation requires new instrumentation and increases the operative time by up to 20 minutes. Another possible complication of CAS is an increased incidence of deep infection due to the longer exposure time. The procedures appear cumbersome in comparison to those of the conventional technique. It may require a number of cases before the surgeon feels comfortable with the navigation system. The present cost of most navigation systems may limit its use for low-volume institutions.

Patient-specific instrumentation has not proven to be as successful in reproducing alignment targets for routine TKA surgery, but may be particularly beneficial when extra-articular malalignment or retained components complicate the use of conventional instrumentation.

Innovations in TKA component design, materials, and surgical techniques are important to increase the proportion of patients who experience their desired outcome following TKA but relative cost associated with the implementation of many of these technological advancements remains a barrier to their widespread incorporation into routine TKA procedures. It also could be argued that navigation may not be worthy of the investment of time and money by the high volume expert. Future studies should have high methodological standards including randomization, follow-up periods, and control of preoperative, intraoperative, and postoperative protocols.

An orthopedic surgeon's experience, adaptability, and knowledge of innovative technological advances are crucial to the success of TKA. Only orthopedic surgeons who clearly understand the technology, goals, surgical method, potential error, and limitations of the same can decide whether its use is appropriate for a specific case. The technology should make TKA more simple, without complication, safe as well as cost effective.