Robotics And Total Knee Replacement: An Objective Analysis Of A Market-Driven Technology

Dec 29, 2019

Robotics is a hot term in medicine right now and a growing market making tremendous profits for the companies that make these units. This technology has entered the realm of joint replacement with the goal of improving the accuracy and reproducibility of implant sizing and placement. Makoplasty, which has the largest market share and linked to Stryker implants, has seen impressive penetration into many hospitals from large academic medical centers to even smaller community hospitals. Several other implant manufacturers are developing similar products given the success of the Makoplasty. Many surgeons have adopted this technology because it is highly marketable and appears to give these surgeons and their affiliated joint programs a technological edge that will attract patients. In fact, this is the principle reason that a majority of medical centers have purchases this extremely expensive technology – the promise that the incorporation of a robot will attract patients and thereby increase hospital revenues.

A recent editorial in the Journal of Arthroplasty raised concerns about how the marketing of this technology for the sake of attracting patients has outpaced the actual that proves it leads to superior outcomes. While robotics can improve the accuracy and reproducibility of bone cuts in total knee replacement, as well as help surgeons determine the optimal implant size and position through preoperative planning, they have yet to conclusively and consistently move the bar on improved patients outcomes. While some studies suggest earlier improvement in range of motion and reduced postoperative pain, most studies fail to show a difference in the end result once patients are fully healed and recovered. This raises serious questions about the actual value of this technology considering it substantial cost.

The critical piece of information that these companies and even the surgeons fail to disclose is that these systems use off-the-shelf, generically sized implants. As such, any operation will ultimately be a compromise between the patient’s actual anatomy and the size and shape of the implant that most closely matches it. The greater the difference in this mismatch, the more likely the implant will create a kinematic conflict that no degree of surgical accuracy can solve. This conflict is resolved through soft tissue balancing which increases the surgical trauma of the operation by forcing surgeons to release or cut tissue in order to have similar tension in the ligaments throughout the range of motion. With a non-anatomic implant, there is no degree of surgical accuracy that can change the fact that the implant is not correctly designed for each individual patient. The anatomy of each knee is unique. Even if the robot can help surgeons improve soft tissue balancing, it does not change the fact that soft tissue balancing is needed to resolve the difference between an average shape and an individual’s anatomy.

To this end, the real value proposition in knee replacement can only be accomplished by custom implants as made by Conformis. Using image-to-implant technology, Conformis can manufacture a custom, patient-specific implant that replicates the unique shape of each patient’s knee. By replacing the joint with an implant that replicates the shape of the native joint, there is no kinematic conflict created by shape mismatch. Conformis can replicate the flexion axis and implant position so that the soft tissues require minimal balancing and thus less trauma during the surgery. Rather than use a very expensive robot to implant a generically shaped prosthesis, Conformis makes custom cutting blocks that ensure accurate implant placement and actually reduces the cost of surgery by requiring less inventory and fewer disposable items needed to introduce the robot into the surgical field.

For more information on the Conformis Patient-Specific Total Knee see the following links